Name: estimating bilateral atrial function by cardiovascular magnetic resonance feature tracking in patients with paroxysmal atrial fibrillation
Uploaded: 2022-07-20T12:45:00.000+00:00
Duration: 8 min 10 s
Description: 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

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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>

<ol>
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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.

<table><tbody><tr><td>CVI42</td><td>Circle Cardiovascular Imaging (Canada)</td><td></td><td></td></tr><tr><td>MAGNETOM Spectra 3.0T</td><td>Siemens</td><td></td><td></td></tr></tbody></table>

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

Research

JoVE Journal

Medicine

1.6K Views.  China-Japan Union Hospital of Jilin University. Proefremodellering wordt beschouwd als het meest kritieke mechanisme voor atriumfibrilleren. Functionele veranderingen in linker atriumstam treden op vóór structurele veranderingen die nauw verband houden met structurele remodellering en myocardiale fibrose in het linker atrium. Cardiale magnetische resonantie functie tracking is een nieuwe niet-invasieve nabewerkingstechniek die linker atriale spanning en reksnelheid met hoge nauwkeurigheid en reproduceerbaarheid kan evalueren.Het e...

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.

Magnetic Resonance Derived Myocardial Strain Assessment Using Feature Tracking

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 ...

Remote Magnetic Navigation for Accurate, Real-time Catheter Positioning and Ablation in Cardiac Electrophysiology Procedures

New remote navigation systems have been developed to improve current limitations of conventional manually guided catheter ablation in complex cardiac substrates such as left atrial flutter. This protocol describes all the clinical and invasive interventional steps performed during a human electrophysiological study and ablation to assess the accuracy, safety and real-time navigation of the Catheter Guidance, Control and Imaging (CGCI) system. Patients who underwent ablation of a right or left atrium flutter substrate were included. Specifically, data from three left atrial flutter and two counterclockwise right atrial flutter procedures are shown in this report. One representative left atrial flutter procedure is shown in the movie. This system is based on eight coil-core electromagnets, which generate a dynamic magnetic field focused on the heart. Remote navigation by rapid changes (msec) in the magnetic field magnitude and a very flexible magnetized catheter allow real-time closed-loop integration and accurate, stable positioning and ablation of the arrhythmogenic substrate.

This report provides a detailed description of a new remote navigation system based on magnetic driven forces, which has been recently introduced as a new robotic tool for human cardiac electrophysiology procedures.

New remote navigation systems have been developed to improve current limitations of conventional manually guided catheter ablation in complex cardiac ...

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 ...

Non-fluoroscopic Catheter Tracking for Fluoroscopy Reduction in Interventional Electrophysiology

A technological platform (MediGuide) has been recently introduced for non-fluoroscopic catheter tracking. In several studies, we have demonstrated that the application of this non-fluoroscopic catheter visualization system (NFCV) reduces fluoroscopy time and dose by 90-95% in a variety of electrophysiology (EP) procedures. This can be of relevance not only to the patients, but also to the nurses and physicians working in the EP lab. Furthermore, in a subset of indications such as supraventricular tachycardias, NFCV enables a fully non-fluoroscopic procedure and allows the lab staff to work without wearing lead aprons. With this protocol, we demonstrate that even complex procedures such as ablations of atrial fibrillation, that are typically associated with fluoroscopy times of &#62;30 min in conventional settings, can safely be performed with a reduction of &#62;90% in fluoroscopy exposure by the additional use of NFCV.

Radiation exposure is an underestimated risk in complex ablation procedures. Here, we describe a protocol to significantly decrease fluoroscopy time and dosage for both the patient and the lab staff by using a novel non-fluoroscopic catheter visualization system.

A technological platform (MediGuide) has been recently introduced for non-fluoroscopic catheter tracking. In several studies, we have demonstrated that ...

Quantification of Mouse Heart Left Ventricular Function, Myocardial Strain, and Hemodynamic Forces by Cardiovascular Magnetic Resonance Imaging

Mouse models have contributed significantly to understanding genetic and physiological factors involved in healthy cardiac function, how perturbations result in pathology, and how myocardial diseases may be treated. Cardiovascular magnetic resonance imaging (CMR) has become an indispensable tool for a comprehensive in vivo assessment of cardiac anatomy and function. This protocol shows detailed measurements of mouse heart left ventricular function, myocardial strain, and hemodynamic forces using 7-Tesla CMR. First, animal preparation and positioning in the scanner are demonstrated. Survey scans are performed for planning imaging slices in various short- and long-axis views. A series of prospective ECG-triggered short-axis (SA) movies (or CINE images) are acquired covering the heart from apex to base, capturing end-systolic and end-diastolic phases. Subsequently, single-slice, retrospectively gated CINE images are acquired in a midventricular SA view, and in 2-, 3-, and 4-chamber views, to be reconstructed into high-temporal resolution CINE images using custom-built and open-source software. CINE images are subsequently analyzed using dedicated CMR image analysis software.
Delineating endomyocardial and epicardial borders in SA end-systolic and end-diastolic CINE images allows for the calculation of end-systolic and end-diastolic volumes, ejection fraction, and cardiac output. The midventricular SA CINE images are delineated for all cardiac time frames to extract a detailed volume-time curve. Its time derivative allows for the calculation of the diastolic function as the ratio of the early filling and atrial contraction waves. Finally, left ventricular endocardial walls in the 2-, 3-, and 4-chamber views are delineated using feature-tracking, from which longitudinal myocardial strain parameters and left ventricular hemodynamic forces are calculated. In conclusion, this protocol provides detailed in vivo quantification of the mouse cardiac parameters, which can be used to study temporal alterations in cardiac function in various mouse models of heart disease.

This study describes a comprehensive cardiovascular magnetic resonance imaging (CMR) protocol to quantify the left ventricular functional parameters of the mouse heart. The protocol describes the acquisition, post-processing, and analysis of the CMR images as well as assessment of different cardiac functional parameters.

Mouse models have contributed significantly to understanding genetic and physiological factors involved in healthy cardiac function, how perturbations ...

Bioengineering

Electrophysiological Assessment of Murine Atria with High-Resolution Optical Mapping

Recent genome-wide association studies targeting atrial fibrillation (AF) have indicated a strong association between the genotype and electrophysiological phenotype in the atria. That encourages us to utilize a genetically-engineered mouse model to elucidate the mechanism of AF. However, it is difficult to evaluate the electrophysiological properties in murine atria due to their small size. This protocol describes the electrophysiological evaluation of atria using an optical mapping system with a high temporal and spatial resolution in Langendorff perfused murine hearts. The optical mapping system is assembled with dual high-speed complementary metal oxide semiconductor cameras and high magnification objective lenses, to detect the fluorescence of a voltage-sensitive dye and Ca2+ indicator. To focus on the assessment of murine atria, optical mapping is performed with an area of 2 mm &#215; 2 mm or 10 mm x 10 mm, with a 100 &#215; 100 resolution (20 &#181;m/pixel or 100 &#181;m/pixel) and sampling rate of up to 10 kHz (0.1 ms) at maximum. A 1-French size quadripolar electrode pacing catheter is placed into the right atrium through the superior vena cava avoiding any mechanical damage to the atrium, and pacing stimulation is delivered through the catheter. An electrophysiological study is performed with programmed stimulation including constant pacing, burst pacing, and up to triple extrastimuli pacing. Under a spontaneous or pacing rhythm, the optical mapping recorded the action potential duration, activation map, conduction velocity, and Ca2+ transient individually in the right and left atria. In addition, the programmed stimulation also determines the inducibility of atrial tachyarrhythmias. Precise activation mapping is performed to identify the propagation of the excitation in the atrium during an induced atrial tachyarrhythmia. Optical mapping with a specialized setting enables a thorough electrophysiological evaluation of the atrium in murine pathological models.

This protocol describes the electrophysiological evaluation of murine atria utilizing an optical mapping system with a high temporal and spatial resolution, including dual recordings of the membrane voltage and Ca2+ transient under programmed stimulation through a specialized electrode catheter.

Recent genome-wide association studies targeting atrial fibrillation (AF) have indicated a strong association between the genotype and ...

Echocardiographic Evaluation of Atrial Communications before Transcatheter Closure

Transthoracic (TTE) and transesophageal echocardiography (TEE) is the standard imaging method for atrial septal defect (ASD) and patent foramen ovale (PFO) detection, for patient selection for transcatheter ASD/PFO closure,&#160;for intraoperative guidance and for long-term follow-up. The size, shape, location and the number of the atrial communications schould be determined. The accuracy of PFO detection can be improved by using agitated saline together with maneuvers to transiently increase the right atrial (RA) pressure. The appearance of microbubbles in the left atrium (LA) within 3 cardiac cycles after opacification of the RA is considered positive for the presence of an intracardiac shunt. Three dimensional TEE identifies further septal fenestrations and describes the dynamic morphology of ASD/PFO and atrial septal aneurysm. Follow-up evaluations with TTE is recommended at 1, 6, and 12 months after the procedure, with a subsequent evaluation every year. Previous studies showed an increased incidence of atrial arrhythmias early after device closure. Speckle tracking analysis may help to understand functional left atrial remodeling following percutaneous closure and its impact on atrial arrhythmias.

Transthoracic (TTE) and transesophageal (TEE) echocardiography represent the basic imaging tools for interatrial septum examination. Three dimensional (3D) TEE provides incremental information in the assessment of the interatrial septum. Further advanced echocardiography techniques using speckle tracking echocardiography are applied for sensitive volumetric and functional assessment of the heart chambers.&#160;

Transthoracic (TTE) and transesophageal echocardiography (TEE) is the standard imaging method for atrial septal defect (ASD) and patent foramen ovale ...

Optimizing Pulmonary Artery Banding for Consistent Right Heart Failure Induction

Rat Model of Right-Sided Cardiac Remodeling and Arrhythmia Using Pulmonary Artery Banding

Clinical conditions, including chronic obstructive pulmonary disease or pulmonary arterial hypertension (PAH), can lead to chronic right ventricle pressure overload and progressive right heart failure (RHF). RHF can be identified by right-sided cardiac hypertrophy and dilation associated with abnormal myocardial function affecting the RV and the right atrium (RA). We recently demonstrated that severe RHF is accompanied by an increased risk of atrial inflammation, atrial fibrosis, and atrial fibrillation (AF), the most common type of cardiac arrhythmia (CA). Recent studies have shown that RV and RA inflammation plays an important role in the arrhythmogenesis of CA, including AF. However, the impact of inflammation in the development of CA and AF in RHF is poorly described.
Experimental models of RHF are required to better understand the association between right-sided myocardial inflammation and CA. The rat model of monocrotaline (MCT)-induced pulmonary hypertension (PH) is well-established to provoke RHF. However, MCT triggers severe pneumo-toxicity and pulmonary inflammation. Hence, MCT-induced RHF does not help to distinguish whether the subsequent myocardial inflammation originates from the RHF per se or circulating inflammatory signals secreted by the injured lung.
In this article, a mechanical method involving pulmonary artery trunk banding (PAB) was used to provoke right-sided cardiac arrhythmogenesis. The PAB consists of performing a permanent suture of the pulmonary artery trunk for 3 weeks. Such an approach generates increased right-sided pressure overload. At D21 post-PAB, the suture results in hypertrophied, dilated, and inflamed RV and RA. The PAB-induced RHF is also accompanied by vulnerability to ventricular and atrial arrhythmias, including AF.

Right heart failure (RHF) is characterized by right-sided cardiac dilation and hypertrophy, leading to ventricular and atrial malfunction. Cardiopulmonary conditions associated with RHF are accompanied by an increased risk for cardiac arrhythmias. This article describes a standardized model of pulmonary artery banding-induced RHF associated with enhanced ventricular and atrial arrhythmogenesis.

Clinical conditions, including chronic obstructive pulmonary disease or pulmonary arterial hypertension (PAH), can lead to chronic right ventricle ...

Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice

Mouse models of genetic and acquired risk factors for atrial fibrillation (AF) have proven valuable in investigating the molecular determinants of AF. Programmed electrical stimulation can be performed using transesophageal atrial pacing as a survival procedure, thus enabling serial testing in the same animal. However, numerous pacing protocols exist, which complicates the reproducibility. The present protocol aims to provide a standardized strategy to develop model-specific experimental parameters to improve reproducibility between studies. Preliminary studies are performed to optimize the experimental methods for the specific model under investigation, including age at the time of the study, sex, and parameters of the pacing protocol (e.g., mode of pacing and definition of AF susceptibility). Importantly, care is taken to avoid high stimulus energies, as this can cause stimulation of the ganglionic plexi with inadvertent parasympathetic activation, manifested by exaggerated atrioventricular (AV) block during pacing and often associated with artifactual AF induction. Animals demonstrating this complication must be excluded from the analysis.

The present protocol describes the optimization of experimental parameters when using transesophageal atrial pacing to assess atrial fibrillation susceptibility in mice.

Mouse models of genetic and acquired risk factors for atrial fibrillation (AF) have proven valuable in investigating the molecular determinants of AF. ...

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

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