Not applicable.

This research procedure closely adheres to the rules established by the China-Japan Union Hospital of Jilin University&#39;s human research ethics committee (No. 2021092704). Before radiofrequency ablation, CMR was required for all patients with atrial fibrillation. Hence our study did not place an increasing burden on patients. Right ventricular two-chamber cine bSSFP sequences were added, which extended the time of each examination by 2 min. Before the test, written informed consent was obtained from each subject. Patients who refused the further sequence were eliminated from the experiment. Patients with poor image quality or atrial fibrillation (AF) during the examination were also excluded.
1. Preparation before scanning
<ol>
	<li>Check the patient information: Patients&#39; heart rate, blood pressure, weight, and height were accurately measured. The on-duty physician formulates an introductory sequence based on the health history and other supplementary investigations and confirms quick adjustments to the analysis based on the actual circumstances.</li>
	<li>Exclude patients having MRI contraindications including renal insufficiency with eGFR &#8804; 30 mL/min/1.73 m2, cardiac implantable electronic devices, implanted metal devices, electronic cochlear implantations, etc.</li>
	<li>Place the patient in the supine position with their heads up and arms at their sides. Due to the length of the examination, do not raise the upper limb above the head.</li>
	<li>Clean the skin and place the electrodes according to the manufacturer&#39;s instructions. Ensure that the non-metallic electrocardiogram electrodes are correctly placed on the surface of the front chest wall to obtain precise electrocardiogram gating. An accurate R wave is required to reduce CMR artifacts. 
	NOTE: After the electrocardiogram electrodes are connected, the patient&#39;s electrocardiogram is displayed on the computer in real-time to measure the R wave. Reposition the electrodes on the patient&#39;s chest if the R wave is not clear enough.</li>
	<li>Place a 16-channel cardiac coil flush to the upper edge of the shoulder blade. Ensure the coil is in-line with the heart and placed to the left.</li>
	<li>Ask the patients to hold their breath at the end of exhalation and ask them to maintain the same breath motion amplitude to ensure the consistency of the scanning position. The breath-hold duration was 10-18 s. Patients were provided with sufficient time for respiratory training. During the examination, the heart rate and time of breath-holding were noted.</li>
</ol>
2. CMR scanning
<ol>
	<li>Use a three-plane localization method to locate the long-axis cine images [two-chamber, three-chamber, and four-chamber views of the left ventricle (LV)] and short-axis of the ventricle (i.e., covering the entire LV). See Figure 1 for the positioning process.
	<ol>
		<li>Acquire the orthogonal multi-slice localizers in the heart&#39;s transverse, sagittal, and coronal slices (Figure 1A).</li>
		<li>Obtain a two-chamber localizer by selecting a transverse slice at the middle of the ventricle from the transverse images. Set a slice vertically on the transverse image, parallel to the septum, and through the apex of the LV (Figure 1B).</li>
		<li>Acquire the four-chamber localizer by positioning the slice vertically on the two-chamber localizer through the apex of the heart and the center of the mitral valve (Figure 1C).</li>
		<li>Acquire the short-axis localizer by positioning the slice vertically on the four-chamber and two-chamber localizers. This slice should be perpendicular to the septum on the four-chamber localizer and at a right angle to the long axis on the two-chamber localizer (Figure 1D).</li>
	</ol>
	</li>
	<li>Based on the above localizers, generate the following standard views.
	<ol>
		<li>Obtain a four-chamber view.Slice (positioning line) will automatically appear, then position the slice through the center of the LV and vertically on the septum on the short-axis localizer. Place the slice through the apex of the heart and adjust to the center of the mitral valve on the two-chamber localizer to get the four-chamber view. Click on Apply to get the four-chamber view (Figure 1E).</li>
		<li>Obtain a two-chamber view. On the short-axis localizers, position the slice parallel to the septum, and adjust it to the center of the LV. On the four-chamber view, place the slice parallel to the septum, and through the apex of the LV (Figure 1F).</li>
		<li>Obtain a three-chamber view: Position the slice through the center of the aorta and the left atrium on the short-axis localizers. Ensure the slice passes through the apex of the LV on the four-chamber view (Figure 1G).</li>
		<li>Obtain short-axis views. Position the slices vertically on the septum and parallel to the mitral annulus on the four-chamber view. Then, arrange the slices vertically on the connection line between the apex of the LV and the center of the mitral annulus on the two-chamber view (Figure 1H).</li>
	</ol>
	</li>
	<li>Obtain a two-chamber view of the right ventricle (RV) by positioning the slice parallel to the septum and shifting the slice into the center of the RV on the short-axis view. Position the slice parallel to the septum on the four-chamber view, and then shift the slice into the center of the RV. Do not cut the LV into parts (Figure 1I).</li>
	<li>Obtain the CMR cine sequences of the two- and four-chamber views of the left and right ventricles, the three-chamber view of the left ventricle, and the short-axis view of the left ventricle using a retrospective ECG gated bSSFP sequence on a 3.0-T MR scanner.
	<ol>
		<li>Use the main parameter settings as follows: matrix = 192 x 192, field of view (FOV) = 340 mm x 340 mm, repetition time (TR) = 3.0 ms, echo time (TE) = 1.7 ms, flip angle (FA) = 45&#176;-55&#176;, temporal resolution = 30-55 ms, slice thickness = 8 mm, and slice gap = 2 mm. 
		NOTE: All the patients should be in the sinus rhythm during CMR imaging.</li>
	</ol>
	</li>
</ol>
3. Ventricular and atrial function analysis
<ol>
	<li>Ventricular function analysis
	<ol>
		<li>Click on PACS, then input Patient ID, and use Search Current Patient to find the images. Next, click on Retrieve to transfer the images to the cardiovascular post-processing workstation. Use the Function Multiplanar module (ventricular function analysis with multiplanar) to analyze the ventricular function.</li>
		<li>Choose the short-axis cine of the ventricle and click on the Detect LV/RV Contours at ED/ES Phases. 
		NOTE: The contours of end-systolic (ED) and end-diastolic (ES) ventricles, endocardium, and epicardium are in all slices and traced automatically. The LV cavity includes the ventricular outflow tract. If the automatic identification is not accurate, it should be adjusted manually. The cardiovascular post-processing workstation automatically calculates the left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume index (LVEDVI), left ventricular end-systolic volume index (LVESVI), right ventricular ejection fraction (RVEF), right ventricular end-diastolic volume (RVEDV), right ventricular end-systolic volume (RVESV), right ventricular end-diastolic volume index (RVEDVI), and right ventricular end-systolic volume index (RVESVI).</li>
	</ol>
	</li>
	<li>Left atrial function analysis
	<ol>
		<li>Use the Tissue Tracking (Feature Tracking) module to measure the LA volumes and strains in the four-, three- and two-chamber cine CMR images of the LV.</li>
		<li>Manually contour the endocardial and epicardial left atrium (LA) borders at the end of the left atrial systole and diastole (Figure 2).</li>
		<li>Exclude the pulmonary veins and left atrial appendage from the LA outline.</li>
		<li>Once the contouring is completed, ensure that the ROI Series (Segment number selection key) is shown as 6 (the four- and two-chamber CMR cine images of the LV are each divided into six segments).</li>
		<li>Click on the Perform Strain Analysis button for the software to automatically track on-screen pixels during the entire cardiac cycle (25 frames/cardiac cycle).</li>
		<li>Ensure that the software automatically calculates the left atrial volume/time curves, the global and segmental strain, and the strain rate.</li>
		<li>Use the volume/time curves to obtain the maximum volume of the left atrium (LAVmax), the left atrial active pre-systolic volume in early left ventricular diastole (LAVpre-A), and the minimum volume of the left atrium (LAVmin). Calculate the LA total, passive, and active emptying fractions (EF) as follows19: 
		<img alt="Equation 1" src="/files/ftp_upload/63598/63598eq01.jpg" style="margin: auto;" /> 
		<img alt="Equation 2" src="/files/ftp_upload/63598/63598eq02.jpg" style="margin: auto;" /> 
		<img alt="Equation 3" src="/files/ftp_upload/63598/63598eq03.jpg" style="margin: auto;" /></li>
		<li>Obtain the peak global longitudinal strain in systole (Sls) and active strain (Sla) from the strain curve of the left atrium (Figure 2) and calculate the difference between the Sls and Sla as the passive strain (Sle)19.</li>
		<li>Acquire the peak strain rate of the left atrium in left ventricular systole (SRs) (the first positive wave peak value on the curve), the peak strain rate in early left ventricular diastole (SRe) (the first negative wave peak value on the curve), and the peak strain rate in late left ventricular diastole (SRa) (second negative wave peak on the curve) from the strain rate curve19 (Figure 2).</li>
	</ol>
	</li>
	<li>Right atrial function analysis
	<ol>
		<li>Obtain the right atrial volumes and strains using the Tissue Tracking (Feature Tracking) module with the four- and two-chamber RV cine CMR images.</li>
		<li>Manually contour the endocardial and epicardial right atrium (RA) borders at the end of the right atrial systole and diastole (Figure 3).</li>
		<li>Exclude the vena cava and right atrial appendage from the RA outline.</li>
		<li>The subsequent steps were the same as steps 3.2.4 and 3.2.6.</li>
		<li>Obtain the functional parameters of the right atrium using steps 3.2.3 and 3.2.5.</li>
	</ol>
	</li>
</ol>

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B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Left+atrial+volume+as+a+morphophysiologic+expression+of+left+ventricular+diastolic+dysfunction+and+relation+to+cardiovascular+risk+burden.">Left atrial volume as a morphophysiologic expression of left ventricular diastolic dysfunction and relation to cardiovascular risk burden.</a> American Journal of Cardiology. 90 (12), 1284-1289 (2002).</li><li>Inoue, Y. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+tissue-tracking+cardiac+magnetic+resonance+(CMR)+of+left+atrial+deformation+and+the+risk+of+stroke+in+patients+with+atrial+fibrillation.">Quantitative tissue-tracking cardiac magnetic resonance (CMR) of left atrial deformation and the risk of stroke in patients with atrial fibrillation.</a> Journal of the American Heart Association. 4 (4), 001844 (2015).</li><li>Singh, A., Addetia, K., Maffessanti, F., Mor-Avi, V., Lang, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LA+strain+for+categorization+of+LV+diastolic+dysfunction.">LA strain for categorization of LV diastolic dysfunction.</a> JACC Cardiovascular Imaging. 10 (7), 735-743 (2017).</li><li>Rodriguez, C. 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I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strain+echocardiographic+assessment+of+left+atrial+function+predicts+recurrence+of+atrial+fibrillation.">Strain echocardiographic assessment of left atrial function predicts recurrence of atrial fibrillation.</a> European Heart Journal Cardiovascular Imaging. 17 (6), 660-667 (2016).</li><li>Hubert, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atrial+function+is+altered+in+lone+paroxysmal+atrial+fibrillation+in+male+endurance+veteran+athletes.">Atrial function is altered in lone paroxysmal atrial fibrillation in male endurance veteran athletes.</a> European Heart Journal Cardiovascular Imaging. 19 (2), 145-153 (2018).</li><li>Kuppahally, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Left+atrial+strain+and+strain+rate+in+patients+with+paroxysmal+and+persistent+atrial+fibrillation:+Relationship+to+left+atrial+structural+remodeling+detected+by+delayed-enhancement+MRI.">Left atrial strain and strain rate in patients with paroxysmal and persistent atrial fibrillation: Relationship to left atrial structural remodeling detected by delayed-enhancement MRI.</a> Circulation Cardiovascular Imaging. 3 (3), 231-239 (2010).</li><li>Kosmala, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Incremental+value+of+left+atrial+structural+and+functional+characteristics+for+prediction+of+atrial+fibrillation+in+patients+receiving+cardiac+pacing.">Incremental value of left atrial structural and functional characteristics for prediction of atrial fibrillation in patients receiving cardiac pacing.</a> Circulation Cardiovascular Imaging. 8 (4), 002942 (2015).</li><li>Obokata, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Left+atrial+strain+provides+incremental+value+for+embolism+risk+stratification+over+CHA(2)DS(2)-VASc+score+and+indicates+prognostic+impact+in+patients+with+atrial+fibrillation.">Left atrial strain provides incremental value for embolism risk stratification over CHA(2)DS(2)-VASc score and indicates prognostic impact in patients with atrial fibrillation.</a> Journal of American Society Echocardiography. 27 (2), 709-716 (2014).</li><li>Azemi, T., Rabdiya, V. M., Ayirala, S. R., McCullough, L. D., Silverman, D. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Left+atrial+strain+is+reduced+in+patients+with+atrial+fibrillation,+stroke+or+TIA,+and+low+risk+CHADS(2)+scores.">Left atrial strain is reduced in patients with atrial fibrillation, stroke or TIA, and low risk CHADS(2) scores.</a> Journal of American Society Echocardiography. 25 (12), 1327-1332 (2012).</li><li>Ipek, E. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+magnetic+resonance-derived+right+atrial+functional+analysis+in+patients+with+atrial+fibrillation+and+typical+atrial+flutter.">Cardiac magnetic resonance-derived right atrial functional analysis in patients with atrial fibrillation and typical atrial flutter.</a> Journal of Interventional Cardiac Electrophysiology. 59 (2), 381-391 (2020).</li><li>Kowallick, J. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+left+atrial+strain+and+strain+rate+using+cardiovascular+magnetic+resonance+myocardial+feature+tracking:+a+feasibility+study[J/OL.">Quantification of left atrial strain and strain rate using cardiovascular magnetic resonance myocardial feature tracking: a feasibility study[J/OL.</a> Journal of Cardiovascular Magnetic Resonance. 16 (1), 60 (2014).</li><li>Peters, D. C., Lamy, J., Sinusas, A. J., Baldassarre, L. 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T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+MR+strain:+A+noninvasive+biomarker+of+fibrofatty+remodeling+of+the+left+atrial+myocardium.">Cardiac MR strain: A noninvasive biomarker of fibrofatty remodeling of the left atrial myocardium.</a> Radiology. 286 (1), 83-92 (2018).</li><li>Habibi, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+magnetic+resonance-Measured+left+atrial+volume+and+function+and+incident+atrial+fibrillation+results+from+MESA+(Multi-ethnic+study+of+atherosclerosis).">Cardiac magnetic resonance-Measured left atrial volume and function and incident atrial fibrillation results from MESA (Multi-ethnic study of atherosclerosis).</a> Circulation Cardiovascular Imaging. 9 (8), (2016).</li><li>Bertelsen, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Left+atrial+volume+and+function+assessed+by+cardiac+magnetic+resonance+imaging+are+maker+of+subclinical+atrial+fibrillation+as+detected+by+continuous+monitoring.">Left atrial volume and function assessed by cardiac magnetic resonance imaging are maker of subclinical atrial fibrillation as detected by continuous monitoring.</a> Europace. 22 (5), 724-731 (2020).</li><li>Claus, P., Omar, A. 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The authors have no conflicts of interest to declare.

Cardiac magnetic resonance feature tracking (CMR-FT) is the most often utilized MR technology for myocardial strain analysis because it is rapid, simple, and efficient. By measuring the displacement and displacement velocity between two sites of the heart, the strain rate obtained by CMR-FT can be utilized to determine atrial function. Strain is represented as a percentage, indicating the proportional curvature of the myocardium18.
Strain reflects the deformation ability of the myocardium, while strain rate reflects the deformation speed of the myocardium. The strain curve expanded rapidly during ventricular systole to reach the peak signifying the maximal distortion of the myocardium during atrial diastole. Because of the atrial myocardium&#39;s expansion, the strain rate curve generated a positive wave. During this time, the atrium&#39;s purpose is to hold return blood flow, which indicates the atrium&#39;s diastolic function. Then, the mitral or tricuspid valves opened in the early ventricular diastole, and blood rapidly flowed into the ventricle. At this time, the atrial volume and the myocardial deformation decreased, and the strain curve quickly dropped to enter the plateau stage. The strain rate curve generated the first negative wave, and the atrium served as a route for venous blood flow into the ventricle. The atrium is constricted to pump blood into the ventricle during late ventricular diastole, and the myocardial fibers are contracted. The strain rate curve&#39;s myocardial deformation decreased to the baseline level, and the second negative wave developed. By the end of this phase, the atrium volume had been reduced to a minimum level19,20.
Recently, it has been confirmed that atrial function is an independent predictor of AF, stroke, and AF recurrence after ablation10,11,12,13,14,15. In an asymptomatic multiethnic group, Habibi et al. discovered that higher LA volumes and decreased passive and total LA emptying fractions are correlated with a higher risk of new-onset AF21. A study found that LA&#39;s volumetric and functional features are independently related to the occurrence of AF in older patients with stroke risk factors22. Habibi et al. discovered that pre-operative LA strain is lower in patients with recurrence following ablation3. Moreover, Inoue et al. also examined the baseline MR of 169 AF patients who had pre-radiofrequency ablation and discovered that a history of stroke/transient ischemic episode was linked with severely impaired LA reservoir function7. Even in patients with low-risk CHADS2 scores, reduced LA strain is still a potentially sensitive marker for the increased risk of stroke or transient ischemic attack15.
These findings are consistent with our findings that the strain in the LA and RA is reduced in AF patients. In AF patients, the strain in each segment of the atrium is reduced, showing that all the segments are implicated in atrial remodeling. More research is needed to determine whether the strain distribution in the atrium differs between patients with different heart diseases. Close attention should be devoted to the patient&#39;s breath training in preparation for the CMR examination. Because images are taken toward the conclusion of the expiratory phase, the same breath range should be used to ensure correct positioning. Before the examination, the patient should be positioned in a suitable position to avoid repositioning due to displacement.
During CMR examination, motion and susceptibility artifacts should be avoided as artifacts leading to unclear boundaries easily affect the atrial wall. Susceptibility artifacts, in particular, should get careful consideration while examining ventricular and atrial artifacts (especially for 3.0T MR). Controlling the patient&#39;s heart rate and rhythm is also essential because an abnormal rhythm will prevent the strain value from being available. We introduced the cine sequence at the right ventricular two-chamber to improve the accuracy of the functional analysis of the right atrium since it was necessary to analyze the function of both atria. This is a special aspect of the current methodology compared to normal scans. The endocardium and epicardium of the atrial diastole and systole must be manually demarcated while examining the atrial strain. At this point, care should be taken to choose the appropriate phase and ensure the atrial appendage is excluded from the atrial contour. The operator must estimate the atrial end-diastole based on experience, and among the 25 frames of a cardiac cycle, the phase with the most considerable atrial volume should be chosen. To get the average value, two calculations should be conducted. Delineation of the endocardium and epicardium should be redone if a significant discrepancy between the two is observed.
Echocardiographic speckle tracking, magnetic resonance tagging, and CMR-FT are common strain approaches. The concepts of echocardiographic speckle tracking are similar to those of CMR-FT technology. Nevertheless, the effectiveness of this technique needs to be improved due to limitations such as low spatial resolution, a weak ultrasound acoustic window, and reproducibility23. The gold standard for myocardial strain is the MR tagging procedure, which is highly reliable. However, picture acquisition and post-processing are difficult and time-consuming processes. Because the atrial wall is thin, this approach is not currently used in atrial strain analysis. Additional sequences are not required for the development of CMR-FT technology. With high spatial resolution cine images and simple post-processing processes, it can be utilized to assess the global and segmental strains of the myocardium24. In addition, research has demonstrated that the strain parameters recorded by CMR-FT are compatible with MR Tagging, confirming the dependability of CMR-FT technology23,24. Moreover, a range of CMR-FT post-processing tools is currently available. As a result, strain data may vary significantly between studies due to the absence of a consistent reference standard. Additional large-sample, multicenter research, and updated post-processing software are required to offer an appropriate reference standard.
Nowadays, CMR-FT technology is being utilized in the investigation of atrial function. Mechanistic studies are urgently needed to increase our understanding of atrial cardiomyopathy in clinical practice. Consequently, atrial strain/strain rate as an atrial imaging biomarker will play a crucial role in the prediction, diagnosis, and prognostic evaluation of atrial fibrillation (AF).

Atrial fibrillation (AF) is the most common tachyarrhythmia, and its prevalence increases with age1. According to studies, atrial remodeling is intimately associated with the development of atrial fibrillation and can increase the effect of atrial cardiomyopathy2. The function of the left atrium (LA) is a crucial indicator and biomarker of subclinical cardiac disorders3. LA function can provide significant diagnostic value reflecting diastolic dysfunction4 and determine the onset, course, and prognosis of atrial fibrillation (AF)5.
The atrial function can be divided into the reservoir, conduit, and booster pump functions corresponding to ventricular systole, early diastole, and late diastole. The reservoir function corresponds to the atrium receiving blood flow from the pulmonary vein to maximum volume when the ventricle is in systole3. During the early diastole of the ventricle, the atrioventricular valve opens, allowing the atrium to serve as a conduit for blood flow from the atria to the ventricle3. When entering late diastole, the atrium aggressively contracts during the booster pump phase to finish ventricular filling3. Irregular morphology and function of the ventricles can directly cause alterations in atrial circulation. The evaluation of changes in this function is essential in understanding the mechanism of whole-heart physiology and hemodynamics. In addition, left atrial enlargement is associated with a bad prognosis for various cardiovascular illnesses6. Morphological markers are less sensitive to ventricular and atrial dysfunction than functional strain metrics. Previous studies have demonstrated that changes in left atrial strain and strain rate occur before structural changes, closely related to structural remodeling and myocardial fibrosis in the left atrium7,8.
Early atrial strain evaluations were mainly based on echocardiographic speckle tracking9,10. Cardiac magnetic resonance (CMR) imaging can provide enhanced spatial resolution, tissue contrast, and a more precise depiction of the atrial wall&#39;s periphery. Cardiac magnetic resonance feature tracking (CMR-FT) has been used to assess ventricular strain and was later applied to the atrium3. This method has become more prevalent in the monitoring of atrial function. Research has demonstrated that left atrial function is an independent prognostic factor of atrial fibrillation (AF), stroke, and relapse of AF after radiofrequency ablation10,11,12,13,14,15. Whereas strain evaluation of the right atrium (RA) by MRI is uncommon, Esra et al. revealed that the RA&#39;s reservoir and booster pump function is markedly diminished in individuals with regular atrial flutter and atrial fibrillation (AF)16. Also, segmental strain analysis can help investigate changes in regional atrial function or remodeling. The present study provides a technical protocol for CMR-FT of the left and right atria and segmental strain and strain rate.

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			<td>CVI42</td>
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			<td>MAGNETOM Spectra 3.0T</td>
			<td>Siemens</td>
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estimating bilateral atrial function by cardiovascular magnetic resonance feature tracking in patients with paroxysmal atrial fibrillation

Atrial fibrillation (AF) is the most common form of arrhythmia. Atrial remodeling is considered the most critical mechanism for the presence and development of atrial fibrillation. Also, atrial remodeling can lead to the enlargement and dysfunction of the left atrium (LA), resulting in thrombosis and heart failure. Functional changes in left atrial strain and strain rate occur before structural alterations and are closely associated with structural remodeling and left atrial fibrosis. These parameters are sensitive biomarkers for atrial function. Cardiac magnetic resonance feature tracking (CMR-FT) is a novel, non-invasive, post-processing technique that can evaluate left atrial strain and strain rate. The CMR-FT was utilized in this investigation to assess the bilateral atrium strain rate in individuals with paroxysmal AF. Modifications in each segmental strain were evaluated using segmental analysis. The CMR-FT is recommended for non-invasive evaluations in the clinical assessment of atrial strain among existing strain imaging techniques. Further, it is a flexible parameter measurement with good reproducibility, high soft-tissue resolution, and post-processing based on standard cine balanced steady-state free precision (bSSFP) long-axis images without requiring a new sequence acquisition.

From July 2020 to August 2021, 243 individuals undergoing MRI scans at our hospital were assessed, and 71 patients with AF who had CMR imaging were ultimately recruited for this study. Patients were excluded based on the following criteria: non-ischemic cardiomyopathy confirmed by CMR examination, such as hypertrophic cardiomyopathy, dilated cardiomyopathy, and myocardial amyloidosis (n = 11); myocardial infarction (n = 8); unqualified image quality due to severe CMR artifacts on cine (n = 2); persistent AF (n = 23), and AF during the CMR (n = 6). Finally, 21 patients with paroxysmal AF who were granted an MRI scan with a sinus rhythm were selected for the study. The control group consisted of 19 age and gender-matched individuals with normal CMR. Table 1 summarizes the baseline demographic information of the paroxysmal AF patients and controls.
All CMR images were uploaded to the cardiology post-processing workstation for analysis by two radiologists with more than 5 years of post-processing expertise. The two radiologists averaged the data and re-measured it in cases with significant differences. Aside from the standard characteristics of left and right ventricular function, the parameters of left and right atrial function were examined. The atrial strain parameters included longitudinal strain and strain rate of reservoir, conduit, and booster pump phases (Figure 2 and Figure 3). We conducted segmental (6-segment) strain parameter analysis on the four- and two-chamber views, in addition to the global longitudinal strain, to assess the effect of AF on the atrial longitudinal strain in various segments. The results showed that the left and right atria&#39;s global longitudinal strain during the AF group&#39;s reservoir phase was significantly lower than in the control group (Figure 4). In the four and two-chamber views, the longitudinal strain of each segment of the left atrium during the reservoir phase was significantly lower than the control group (Figure 5).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63598/63598fig01.jpg" /> 
Figure 1: Illustration of the three-plane localization. (A) Orthogonal multi-slice localizers; (B) Positioning and two-chamber localizer; (C) Positioning and four-chamber localizer; (D) Slice position and short-axis localizer; (E) Positioning and four-chamber view; (F) Positioning and two-chamber view; (G) Positioning and three-chamber view; (H) Positioning and short-axis view; (I) Positioning and two-chamber view of the right ventricle. <a href="https://www.jove.com/files/ftp_upload/63598/63598fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/63598/63598fig02.jpg" /> 
Figure 2: The left atrial longitudinal strain and strain rate measures using the CMR feature tracking from the four-, three-, and two-chamber cine CMR images. (A-F) Tracking of left atrial endocardial and epicardial borders at the end of the diastole and systole from the four-, three-, and two-chamber cine CMR images. (G-H) The strain and strain rate curves of the left atrium represent the three LA functions: atrial reservoir function (Sls: peak global longitudinal strain in systole; SRs: strain rate in systole), conduit function (Sle: passive strain; SRe: early diastolic atrial strain rate), booster pump function (Sla: active strain; SRa: late diastolic atrial strain rate). <a href="https://www.jove.com/files/ftp_upload/63598/63598fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/63598/63598fig03.jpg" /> 
Figure 3: The right atrial longitudinal strain and strain rate measures using the CMR feature tracking from the four and two-chamber cine CMR images. (A-D) Tracking of right atrial endocardial and epicardial borders at the end of the diastole and systole from the four- and two-chamber cine CMR images. (E-F) The strain and strain rate curves of the right atrium represent the three RA functions: atrial reservoir function (Sls: peak global longitudinal strain in systole; SRs: strain rate in systole), conduit function (Sle: passive strain; SRe: early diastolic atrial strain rate), booster pump function (Sla: active strain; SRa: late diastolic atrial strain rate). <a href="https://www.jove.com/files/ftp_upload/63598/63598fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/63598/63598fig04.jpg" /> 
Figure 4: Comparison of the global longitudinal strain of the left and right atria in the AF and control groups during the reservoir phase. (A) The left atrium&#39;s global longitudinal strain during the AF group&#39;s reservoir phase was significantly lower than the control group (53.17% vs 33.59%, P &#60; 0.05). (B) The global longitudinal strain of the right atrium during the reservoir phase in the AF group was significantly lower than in the control group (49.99% vs 38.08%, P &#60; 0.05). AF: atrial fibrillation. <a href="https://www.jove.com/files/ftp_upload/63598/63598fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/63598/63598fig05.jpg" /> 
Figure 5: Comparison of the longitudinal strains of the left atrium in the four- and two-chamber views with six segments. (A) The longitudinal strains of the left atrial four-chamber view with six segments during the reservoir phase were significantly lower than the control group. (B) The longitudinal strains of the left atrial two-chamber view with six segments during the reservoir phase were significantly lower than the control group during the reservoir phase. AF = atrial fibrillation. <a href="https://www.jove.com/files/ftp_upload/63598/63598fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Table 1: Baseline information for the AF and control groups. <a href="https://www.jove.com/files/ftp_upload/63598/baseline information table.docx" target="_blank">Please click here to download this Table.</a>

Watch this Scientific Journal Video about Estimating Bilateral Atrial Function by Cardiovascular Magnetic Resonance Feature Tracking in Patients with Paroxysmal Atrial Fibrillation at JoVE.com

Estimating Bilateral Atrial Function by Cardiovascular Magnetic Resonance Feature Tracking in Patients with Paroxysmal Atrial Fibrillation

The atrial function is associated with the strain and strain rate. The cardiac magnetic resonance feature tracking (CMR-FT) technique was used in this study to quantify left and right atrial global and segmental longitudinal strain and strain rate in individuals with paroxysmal atrial fibrillation.

Atrial fibrillation (AF) is the most common form of arrhythmia. Atrial remodeling is considered the most critical mechanism for the presence and ...

estimating-bilateral-atrial-function-cardiovascular-magnetic

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1.6K Views.  China-Japan Union Hospital of Jilin University. The atrial function is associated with the strain and strain rate. The cardiac magnetic resonance feature tracking (CMR-FT) technique was used in this study to quantify left and right atrial global and segmental longitudinal strain and strain rate in individuals with paroxysmal atrial fibrillation.

Video: Estimating Bilateral Atrial Function by Cardiovascular Magnetic Resonance Feature Tracking in Patients with Paroxysmal Atrial Fibrillation

Magnetic Resonance Derived Myocardial Strain Assessment Using Feature Tracking

Purpose: An accurate and practical method to measure parameters like strain in myocardial tissue is of great clinical value, since it has been shown, that strain is a more sensitive and earlier marker for contractile dysfunction than the frequently used parameter EF. Current technologies for CMR are time consuming and difficult to implement in clinical practice. Feature tracking is a technology that can lead to more automization and robustness of quantitative analysis of medical images with less time consumption than comparable methods.
Methods: An automatic or manual input in a single phase serves as an initialization from which the system starts to track the displacement of individual patterns representing anatomical structures over time. The specialty of this method is that the images do not need to be manipulated in any way beforehand like e.g. tagging of CMR images.
Results: The method is very well suited for tracking muscular tissue and with this allowing quantitative elaboration of myocardium and also blood flow.
Conclusions: This new method offers a robust and time saving procedure to quantify myocardial tissue and blood with displacement, velocity and deformation parameters on regular sequences of CMR imaging. It therefore can be implemented in clinical practice.

An accurate and practical method to measure parameters like strain in myocardial tissue is of great clinical value, since it has been shown, that strain is a more sensitive and earlier marker for contractile dysfunction than the frequently used parameter EF.

Purpose: An accurate and practical method to measure parameters like strain in myocardial tissue is of great clinical value, since it has been shown, that ...

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Atrial fibrillation (AF) is a complex cardiac arrhythmia with high morbidity and mortality.1,2 It is the most common sustained cardiac rhythm disturbance seen in clinical practice and its prevalence is expected to increase in the coming years.3 Increased intra-atrial pressure and dilatation have been long recognized to lead to AF,1,4 which highlights the relevance of using animal models and stretch to study AF dynamics. Understanding the mechanisms underlying AF requires visualization of the cardiac electrical waves with high spatial and temporal resolution. While high-temporal resolution can be achieved by conventional electrical mapping traditionally used in human electrophysiological studies, the small number of intra-atrial electrodes that can be used simultaneously limits the spatial resolution and precludes any detailed tracking of the electrical waves during the arrhythmia. The introduction of optical mapping in the early 90's enabled wide-field characterization of fibrillatory activity together with sub-millimeter spatial resolution in animal models5,6 and led to the identification of rapidly spinning electrical wave patterns (rotors) as the sources of the fibrillatory activity that may occur in the ventricles or the atria.7-9 Using combined time- and frequency-domain analyses of optical mapping it is possible to demonstrate discrete sites of high frequency periodic activity during AF, along with frequency gradients between left and right atrium. The region with fastest rotors activates at the highest frequency and drives the overall arrhythmia.10,11 The waves emanating from such rotor interact with either functional or anatomic obstacles in their path, resulting in the phenomenon of fibrillatory conduction.12 Mapping the endocardial surface of the posterior left atrium (PLA) allows the tracking of AF wave dynamics in the region with the highest rotor frequency. Importantly, the PLA is the region where intracavitary catheter-based ablative procedures are most successful terminating AF in patients,13 which underscores the relevance of studying AF dynamics from the interior of the left atrium. Here we describe a sheep model of acute stretch-induced AF, which resembles some of the characteristics of human paroxysmal AF. Epicardial mapping on the left atrium is complemented with endocardial mapping of the PLA using a dual-channel rigid borescope c-mounted to a CCD camera, which represents the most direct approach to visualize the patterns of activation in the most relevant region for AF maintenance.

This report provides a detailed description of the methodology and results of simultaneous endocardial and epicardial optical mapping of electrical excitation in the intact left atrium of a Langendorff-perfused sheep heart during stretch-induced atrial fibrillation.

 Atrial fibrillation (AF) is a complex cardiac arrhythmia with high morbidity and mortality.1,2 It is the most common sustained cardiac rhythm disturbance ...

The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting an estimated 6 million people in the United States 1. Since AF affects primarily elderly people, its prevalence increases parallel with age. As such, it is expected that 15.9 million Americans will be affected by the year 2050 2. Ischemic stroke occurs in 5% of non-anticoagulated AF patients each year. Current treatments for AF include rate control, rhythm control and prevention of stroke 3.
The American College of Cardiology, American Heart Association, and European Society of Cardiology currently recommended rate control as the first course of therapy for AF 3. Rate control is achieved by administration of pharmacological agents, such as &beta;-blockers, that lower the heart rate until it reaches a less symptomatic state 3. Rhythm control aims to return the heart to its normal sinus rhythm and is typically achieved through administration of antiarrhythmic drugs such as amiodarone, electrical cardioversion or ablation therapy. Rhythm control methods, however, have not been demonstrated to be superior to rate-control methods 4-6. In fact, certain antiarrhythmic drugs have been shown to be associated with higher hospitalization rates, serious adverse effects 3, or even increases in mortality in patients with structural heart defects 7. Thus, treatment with antiarrhythmics is more often used when rate-control drugs are ineffective or contraindicated. Rate-control and antiarrhythmic agents relieve the symptoms of AF, including palpitations, shortness of breath, and fatigue 8, but don't reliably prevent thromboembolic events 6.
Treatment with the anticoagulant drug warfarin significantly reduces the rate of stroke or embolism 9,10. However, because of problems associated with its use, fewer than 50% of patients are treated with it. The therapeutic dose is affected by drug, dietary, and metabolic interactions, and thus requires detailed monitoring. In addition, warfarin has the potential to cause severe, sometimes lethal, bleeding 2. As an alternative, aspirin is commonly prescribed. While aspirin is typically well tolerated, it is far less effective at preventing stroke 10. Other alternatives to warfarin, such as dabigatran 11 or rivaroxaban 12 demonstrate non-inferiority to warfarin with respect to thromboembolic events (in fact, dabigatran given as a high dose of 150 mg twice a day has shown superiority). While these drugs have the advantage of eliminating dietary concerns and eliminating the need for regular blood monitoring, major bleeding and associated complications, while somewhat less so than with warfarin, remain an issue 13-15.
Since 90% of AF-associated strokes result from emboli that arise from the left atrial appendage (LAA) 2, one alternative approach to warfarin therapy has been to exclude the LAA using an implanted device to trap blood clots before they exit. Here, we demonstrate a procedure for implanting the WATCHMAN Left Atrial Appendage Closure Device. A transseptal cannula is inserted through the femoral vein, and under fluoroscopic guidance, inter-atrial septum is crossed. Once access to the left atrium has been achieved, a guidewire is placed in the upper pulmonary vein and the WATCHMAN Access Sheath and dilator are advanced over the wire into the left atrium. The guidewire is removed, and the access sheath is carefully advanced into the distal portion of the LAA over a pigtail catheter. The WATCHMAN Delivery System is prepped, inserted into the access sheath, and slowly advanced. The WATCHMAN device is then deployed into the LAA. The device release criteria are confirmed via fluoroscopy and transesophageal echocardiography (TEE) and the device is released.

The accompanying video describes a procedure for percutaneous placement of the WATCHMAN Left Atrial Appendage (LAA) Device. The WATCHMAN is a nitinol device designed to be permanently implanted at, or slightly distal to, the opening of the left atrial appendage (LAA) to trap blood clots before they exit the LAA, preventing thromboembolic stroke.

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting an estimated 6 million people in the United States 1. Since AF affects primarily ...

Catheter Ablation in Combination With Left Atrial Appendage Closure for Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting millions of individuals worldwide 1-3. The rapid, irregular, and disordered electrical activity in the atria gives rise to palpitations, fatigue, dyspnea, chest pain and dizziness with or without syncope 4, 5. Patients with AF have a five-fold higher risk of stroke 6.
Oral anticoagulation (OAC) with warfarin is commonly used for stroke prevention in patients with AF and has been shown to reduce the risk of stroke by 64% 7. Warfarin therapy has several major disadvantages, however, including bleeding, non-tolerance, interactions with other medications and foods, non-compliance and a narrow therapeutic range 8-11. These issues, together with poor appreciation of the risk-benefit ratio, unawareness of guidelines, or absence of an OAC monitoring outpatient clinic may explain why only 30-60% of patients with AF are prescribed this drug 8.
The problems associated with warfarin, combined with the limited efficacy and/or serious side effects associated with other medications used for AF 12,13, highlight the need for effective non-pharmacological approaches to treatment. One such approach is catheter ablation (CA), a procedure in which a radiofrequency electrical current is applied to regions of the heart to create small ablation lesions that electrically isolate potential AF triggers 4. CA is a well-established treatment for AF symptoms 14, 15, that may also decrease the risk of stroke. Recent data showed a significant decrease in the relative risk of stroke and transient ischemic attack events among patients who underwent ablation compared with those undergoing antiarrhythmic drug therapy 16.
Since the left atrial appendage (LAA) is the source of thrombi in more than 90% of patients with non-valvular atrial fibrillation 17, another approach to stroke prevention is to physically block clots from exiting the LAA. One method for occluding the LAA is via percutaneous placement of the WATCHMAN LAA closure device. The WATCHMAN device resembles a small parachute. It consists of a nitinol frame covered by fabric polyethyl terephthalate that prevents emboli, but not blood, from exiting during the healing process. Fixation anchors around the perimeter secure the device in the LAA (Figure 1). To date, the WATCHMAN is the only implanted percutaneous device for which a randomized clinical trial has been reported. In this study, implantation of the WATCHMAN was found to be at least as effective as warfarin in preventing stroke (all-causes) and death (all-causes) 18. This device received the Conformit&eacute; Europ&eacute;enne (CE) mark for use in the European Union for warfarin eligible patients and in those who have a contraindication to anticoagulation therapy 19.
Given the proven effectiveness of CA to alleviate AF symptoms and the promising data with regard to reduction of thromboembolic events with both CA and WATCHMAN implantation, combining the two procedures is hoped to further reduce the incidence of stroke in high-risk patients while simultaneously relieving symptoms. The combined procedure may eventually enable patients to undergo implantation of the WATCHMAN device without subsequent warfarin treatment, since the CA procedure itself reduces thromboembolic events. This would present an avenue of treatment previously unavailable to patients ineligible for warfarin treatment because of recurrent bleeding 20 or other warfarin-associated problems.
The combined procedure is performed under general anesthesia with biplane fluoroscopy and TEE guidance. Catheter ablation is followed by implantation of the WATCHMAN LAA closure device. Data from a non-randomized trial with 10 patients demonstrates that this procedure can be safely performed in patients with a CHADS2 score of greater than 1 21. Further studies to examine the effectiveness of the combined procedure in reducing symptoms from AF and associated stroke are therefore warranted.

Catheter ablation is combined with placement of the WATCHMAN Left Atrial Appendage Closure Device to prevent ischemic stroke in a patient with non-valvular atrial fibrillation.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting millions of individuals worldwide 1-3. The rapid, irregular, and ...

Tracking the Mammary Architectural Features and Detecting Breast Cancer with Magnetic Resonance Diffusion Tensor Imaging

Breast cancer is the most common cause of cancer among women worldwide. Early detection of breast cancer has a critical role in improving the quality of life and survival of breast cancer patients. In this paper a new approach for the detection of breast cancer is described, based on tracking the mammary architectural elements using diffusion tensor imaging (DTI). 
The paper focuses on the scanning protocols and image processing algorithms and software that were designed to fit the diffusion properties of the mammary fibroglandular tissue and its changes during malignant transformation. The final output yields pixel by pixel vector maps that track the architecture of the entire mammary ductal glandular trees and parametric maps of the diffusion tensor coefficients and anisotropy indices. 
The efficiency of the method to detect breast cancer was tested by scanning women volunteers including 68 patients with breast cancer confirmed by histopathology findings. Regions with cancer cells exhibited a marked reduction in the diffusion coefficients and in the maximal anisotropy index as compared to the normal breast tissue, providing an intrinsic contrast for delineating the boundaries of malignant growth. Overall, the sensitivity of the DTI parameters to detect breast cancer was found to be high, particularly in dense breasts, and comparable to the current standard breast MRI method that requires injection of a contrast agent. Thus, this method offers a completely non-invasive, safe and sensitive tool for breast cancer detection.

We describe how to obtain parametric and vector maps of the diffusion tensor of the breast using magnetic resonance imaging. The protocol and final output following imaging processing are tailored for tracking breast architectural features and detecting breast malignancy.

Breast cancer is the most common cause of cancer among women worldwide. Early detection of breast cancer has a critical role in improving the quality of ...

Robotic Ablation of Atrial Fibrillation

Background: Pulmonary vein isolation (PVI) is an established treatment for atrial fibrillation (AF). During PVI an electrical conduction block between pulmonary vein (PV) and left atrium (LA) is created. This conduction block prevents AF, which is triggered by irregular electric activity originating from the PV. However, transmural atrial lesions are required which can be challenging. Re-conduction and AF recurrence occur in 20 - 40% of the cases. Robotic catheter systems aim to improve catheter steerability. Here, a procedure with a new remote catheter system (RCS), is presented. Objective of this article is to show feasibility of robotic AF ablation with a novel system. Materials and Methods: After interatrial trans-septal puncture is performed using a long sheath and needle under fluoroscopic guidance. The needle is removed and a guide wire is placed in the left superior PV. Then an ablation catheter is positioned in the LA, using the sheath and wire as guide to the LA. LA angiography is performed over the sheath. A circular mapping catheter is positioned via the long sheath into the LA and a three-dimensional (3-D) anatomical reconstruction of the LA is performed. The handle of the ablation catheter is positioned in the robotic arm of the Amigo system and the ablation procedure begins. During the ablation procedure, the operator manipulates the ablation catheter via the robotic arm with the use of a remote control. The ablation is performed by creating point-by-point lesions around the left and right PV ostia. Contact force is measured at the catheter tip to provide feedback of catheter-tissue contact. Conduction block is confirmed by recording the PV potentials on the circular mapping catheter and by pacing maneuvers. The operator stays out of the radiationfield during ablation. Conclusion: The novel catheter system allows ablation with high stability on low operator fluoroscopy exposure.

Pulmonary vein isolation (PVI) with an ablation catheter is a curative treatment for atrial fibrillation (AF). Robotic catheter systems aim to improve catheter steerability. Here, a procedure with a new robotic catheter system is presented. The goal of the procedure is electrical block between pulmonary vein and left atrium.

Background: Pulmonary vein isolation (PVI) is an established treatment for atrial fibrillation (AF). During PVI an electrical conduction block between ...

Isolation of Atrial Cardiomyocytes from a Rat Model of Metabolic Syndrome-related Heart Failure with Preserved Ejection Fraction

In this article, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes (ACMs) from a rat model of metabolic syndrome (MetS)-related heart failure with preserved ejection fraction (HFpEF). The prevalence of MetS-related HFpEF is rising, and atrial cardiomyopathies associated with atrial remodeling and atrial fibrillation are clinically highly relevant as atrial remodeling is an independent predictor of mortality. Studies with isolated single-cell cardiomyocytes are frequently used to corroborate and complement in vivo findings. Circulatory vessel rarefication and interstitial tissue fibrosis pose a potentially limiting factor for the successful single-cell isolation of ACMs from animal models of this disease.
We have addressed this issue by employing a device capable of manually regulating the intraluminal pressure of cardiac cavities during the isolation procedure, substantially increasing the yield of morphologically and functionally intact ACMs. The acquired cells can be used in a variety of different experiments, such as cell culture and functional Calcium imaging (i.e., excitation-contraction-coupling).
We provide the researcher with a step-by-step protocol, a list of optimized solutions, thorough instructions to prepare the necessary equipment, and a comprehensive troubleshooting guide. While the initial implementation of the procedure might be rather difficult, a successful adaptation will allow the reader to perform state-of-the-art ACM isolations in a rat model of MetS-related HFpEF for a broad spectrum of experiments.

Here, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes from a rat model of metabolic syndrome-related heart failure with preserved ejection fraction. A manual regulation of intraluminal pressure of cardiac cavities is implemented to yield functionally intact myocytes suitable for excitation-contraction-coupling studies.

In this article, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes (ACMs) from a rat model of ...

Left Atrial Stenosis Induced Pulmonary Venous Arterialization and Group 2 Pulmonary Hypertension in Rat

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of group 2 PH, due to mitral stenosis (MS), to facilitate the investigation of disease mechanisms and potential therapeutic strategies. We present a novel rat model of pulmonary venous congestion-induced pulmonary venous arterialization and group 2 PH caused by left atrial stenosis (LAS). LAS is achieved by constricting the left atrium using a half-closed titanium clip. After the LAS surgery, a rat model with a transmitral inflow velocity greater than or equal to 2.0 m/s on echocardiography gradually develops pulmonary venous arterialization and group 2 PH over an 8- to 10-week period. In this protocol, we provide the step-by-step procedure of how to perform the LAS surgery. The presented LAS rat model mimics MS in humans and is useful for studying the underlying molecular mechanism of pulmonary venous arterialization and for the preclinical evaluation of therapies for group 2 PH.

Left atrial stenosis (LAS) is a novel surgical technique used for studying group 2 pulmonary hypertension (PH) and mechanisms underlying pulmonary venous arterialization. Here, we present a protocol to constrict the left atrium using a titanium clip to cause pulmonary venous arterialization and moderate PH in a rat.

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of ...

Isolation of Atrial Myocytes from Adult Mice

The electrophysiological properties of atrial myocytes importantly affect overall cardiac function. Alterations in the underlying ionic currents responsible for the action potential can cause pro-arrhythmic substrates that underlie arrhythmias, such as atrial fibrillation, which are highly prevalent in many conditions and disease states. Isolating adult mouse atrial cardiomyocytes for use in patch-clamp experiments has greatly advanced our knowledge and understanding of the cellular electrophysiology in the healthy atrial myocardium and in the setting of atrial pathophysiology. In addition, studies using genetic mouse models have elucidated the role of a vast array of proteins in regulating atrial electrophysiology. Here we provide a detailed protocol for the isolation of cardiomyocytes from the atrial appendages of adult mice using a combination of enzymatic digestion and mechanical dissociation of these tissues. This approach consistently and reliably yields isolated atrial cardiomyocytes that can then be used to characterize cellular electrophysiology by measuring action potentials and ionic currents in patch-clamp experiments under a number of experimental conditions.

This protocol is used to isolate single atrial cardiomyocytes from the adult mouse heart using a chunk digestion approach. This approach is used to isolate right or left atrial myocytes that can be used to characterize atrial myocyte electrophysiology in patch-clamp studies.

The electrophysiological properties of atrial myocytes importantly affect overall cardiac function. Alterations in the underlying ionic currents ...

Cooling or Warming the Esophagus to Reduce Esophageal Injury During Left Atrial Ablation in the Treatment of Atrial Fibrillation

Ablation of the left atrium using either radiofrequency (RF) or cryothermal energy is an effective treatment for atrial fibrillation (AF) and is the most frequent type of cardiac ablation procedure performed. Although generally safe, collateral injury to surrounding structures, particularly the esophagus, remains a concern. Cooling or warming the esophagus to counteract the heat from RF ablation, or the cold from cryoablation, is a method that is used to reduce thermal esophageal injury, and there are increasing data to support this approach. This protocol describes the use of a commercially available esophageal temperature management device to cool or warm the esophagus to reduce esophageal injury during left atrial ablation. The temperature management device is powered by standard water-blanket heat exchangers, and is shaped like a standard orogastric tube placed for gastric suctioning and decompression. Water circulates through the device in a closed-loop circuit, transferring heat across the silicone walls of the device, through the esophageal wall. Placement of the device is analogous to the placement of a typical orogastric tube, and temperature is adjusted via the external heat-exchanger console.

The goal of this protocol is to describe the use of esophageal temperature modulation to counteract esophageal thermal injury from left atrial ablation for the treatment of atrial fibrillation.

Ablation of the left atrium using either radiofrequency (RF) or cryothermal energy is an effective treatment for atrial fibrillation (AF) and is the most ...