We thank the patients for participating in this study. We are also grateful to the Biomedicine Electron Microscopy Laboratory of Basic Medical Science School of Central South University, particularly to Xiaoying Wu and Jin Li for technical support. This work was supported by the National Key Research and Development Program (No. 2018YFC1311204).

The Institutional Review Board approved the study protocol, and samples of the dilated left atrium (LA) tissues in the dextrocardia cases were collected for electron microscopy after written informed consent had been obtained.
1. Surgical procedure and ablation
<ol>
	<li>Perform a median sternotomy and suspend the left lateral pericardium after opening.
	<ol>
		<li>Cannulate the ascending aorta and the superior and inferior vena cava (SVC, IVC) to establish mild hypothermic cardiopulmonary bypass (CPB).</li>
		<li>Have the operator switch position from the right side to the left of the operating table after establishing the bypass.</li>
		<li>Give antegrade cold blood cardioplegia intermittently from the aortic root to achieve cardioplegic arrest.</li>
		<li>Perform the right atrial (RA) incision on the left side of the heart, parallel to the atrioventricular sulcus, providing exposure for subsequent RA ablation and tricuspid valve surgery. Ensure the left-sided left atriotomy is located parallelly under the interatrial groove.</li>
		<li>Place a retractor on the wall of LA for sufficient exposure to perform LA ablation and approach the mitral valve (MV).</li>
		<li>Make an aortic incision via a transverse aortotomy performed specially for selective antegrade cardioplegia into the left and right coronary orifices and subsequent AV surgery. 
		NOTE: This was done for the second patient.</li>
	</ol>
	</li>
	<li>Cryoablation 
	NOTE: In the previous two patients, cryoablation was performed exclusively using a flexible, 10 cm long, metal cryoprobe (see the Table of Materials). The cryoprobe uses nitrous oxide (N2O) gas to achieve rapid atrial tissue freezing to a target of -60 &#176;C10.
	<ol>
		<li>Design the cryolesion set to replicate the mirror image of the CMP-IV lesion set. Set the duration of the LA cryoablation for each lesion at -60 &#176;C for 2 min.
		<ol>
			<li>Ensure the posterior LA box lesion is composed of the LA incision and the cryolesion encircling the left and right pulmonary veins.</li>
			<li>Apply a cryolesion line to connect the left superior pulmonary vein with the left atrial appendage (LAA).</li>
			<li>Form an ice ball to mark the coronary sinus using cryoablation from the epicardium (Figure 2). When performing the mitral isthmus line, place the cryoprobe at the inferior aspect of the left atriotomy and direct it to the mitral annulus at the 8 o&#39;clock position, across the posterior LA and coronary sinus, as marked with the ice ball (Figure 3A).</li>
			<li>Apply right-sided LAA amputation.</li>
			<li>After the LA cryoablation, sample 4 x 8 mm tissue of the cryoablated LA for electron microscopic examination. In addition, sample a similar, large, nonablated tissue from the margin of the LA incision for the control test. 
			NOTE: Nonablated tissue was sampled in the second case.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Perform prosthetic valve replacement surgery with a 27 mm mechanical MV using a 2-0 polypropylene running suture. Replace a 23 mm mechanical AV with 2-0 polypropylene running sutures. 
	NOTE: The mechanical MV replacement surgery was performed on the first patient, whereas the replacement with the mechanical AV was done for the second patient.</li>
	<li>Perform the RA cryoablation during the CPB, with the heart warm and beating, for 2 min at -60 &#176;C for each ablation lesion.
	<ol>
		<li>Create the linear cryoablation lines from the inferior aspect of the left-sided right atriotomy up onto the SVC and down to the IVC (Figure 3B).</li>
		<li>Make the tricuspid isthmus linear cryolesion from the midportion of the right atriotomy, directed endocardially toward the tricuspid annulus at the 10 o&#39;clock position (Figure 3B and Figure 4).</li>
		<li>Make a lateral cryolesion from the midportion of the right atriotomy up to the tip of the right atrial appendage (RAA).</li>
	</ol>
	</li>
	<li>Perform three-dimensional (3D) printing of the heart in advance, using the derived cardiac CT data (Figure 5)11. 
	NOTE: This was done for the third patient.
	<ol>
		<li>Access the left atrium through the interatrial groove during the operation. Extend the mitral isthmus lesion to the posterior mitral annulus for the left atrial lesion sets and ablate the coronary sinus in the endocardium and epicardium with a bipolar radiofrequency pen.
		<ol>
			<li>Make other lesions using bipolar radiofrequency clamps: (i) bilateral pulmonary vein isolation; (ii) ablation lines connecting the left atrial appendage and the left superior pulmonary vein; (iii) ablation lines connecting the right and the left superior pulmonary veins; (iv) ablation lines connecting the right and the left inferior pulmonary veins, and (v) mitral line lesions (Figure 3A).</li>
			<li>Dissect the Marshall ligament, and separate the left atrial appendage using an epicardial atrial clamp closure device. Use bipolar radiofrequency forceps to ablate the entire right atrial lesion sets, including the annular tricuspid valve lesions, superior and inferior vena cava lesion lines, and lesion lines connecting the right atrium incision to the right atrial appendage (Figure 3B).</li>
		</ol>
		</li>
		<li>Resect the A1 ruptured chordae, implant a single, flexible, artificial chord with 4-0 expanded polytetrafluoroethylene in situ (see the Table of Materials), and close the residual leak of the anterior commissure and the A2 leaflet cleft.
		<ol>
			<li>Implant a 32 mm, rigid mitral ring to stabilize the annulus. Ensure that the coaptation height is 9 mm after the mitral valve reconstruction. After de-airing and closure of the interatrial sulcus incision, remove the aortic clamp, then make a longitudinal incision on the surface of the right atrium.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Perform the tricuspid annuloplasty with a 30 mm tricuspid ring or with a 28 mm band, implanting them in an &#34;upside-down&#34; and particularly &#34;mirror-image inversion&#34; manner using 2-0 polyester interrupted sutures (Figure 6). Remove the holder before fixation of the annuloplasty ring. 
	NOTE: Tricuspid annuloplasty was performed in the previous two patients, while the band was used in the third case.</li>
	<li>Ensure that sinus rhythm is restored in all patients without any atrioventricular block before cardiopulmonary bypass weaning. Fix temporary epicardial pacing wires after the cardiac surgery.</li>
</ol>
2. Postoperative management and follow-up
<ol>
	<li>Monitor all patients by continuous ECG recordings during hospitalization to ensure no early AF recurrence occurs.</li>
	<li>Administer antiarrhythmic drugs (AADs) orally, with 200 mg/day of amiodarone routinely, for the first 3-6 months to prevent recurrence of AF.</li>
	<li>Administer warfarin for oral anticoagulation and test prothrombin time (PT) regularly.</li>
	<li>Perform chest roentgenogram, TTE, ECG, and 24 h Holter before discharge.</li>
	<li>After hospital discharge, follow all patients with clinical examination, PT test, TTE, ECG, and 24 h Holter at 3, 6, 12, 18, 24, 36, and 48 months after surgery. 
	NOTE: The third patient was followed during a 12-month follow-up period.</li>
</ol>

<ol><li>Rao, P. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Dextrocardia%3A+systematic+approach+to+differential+diagnosis%5BTitle%5D)+AND+%22American+Heart+Journal%22%5BJournal%5D)">Dextrocardia: systematic approach to differential diagnosis.</a> American Heart Journal. 102 (3), Pt 1 389-403 (1981).</li>
<li>Garg, N., Agarwal, B. L., Modi, N., Radhakrishnan, S., Sinha, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Dextrocardia%3A+an+analysis+of+cardiac+structures+in+125+patients%5BTitle%5D)+AND+%22International+Journal+of+Cardiology%22%5BJournal%5D)">Dextrocardia: an analysis of cardiac structures in 125 patients.</a> International Journal of Cardiology. 88 (2-3), 143-155 (2003).</li>
<li>Prystowsky, E. N., Padanilam, B. J., Fogel, R. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Treatment+of+atrial+fibrillation%5BTitle%5D)+AND+%22JAMA%22%5BJournal%5D)">Treatment of atrial fibrillation.</a> JAMA. 314 (3), 278-288 (2015).</li>
<li>Okamura, H., Yamaguchi, A., Adachi, K., Adachi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mitral+valve+replacement+in+a+case+of+dextrocardia+with+situs+solitus%5BTitle%5D)+AND+%22The+Journal+of+Heart+Valve+Disease%22%5BJournal%5D)">Mitral valve replacement in a case of dextrocardia with situs solitus.</a> The Journal of Heart Valve Disease. 19 (6), 794-796 (2010).</li>
<li>Sahin, M. A., Guler, A., Kaya, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mitral+valve+replacement+in+a+patient+with+situs+inversus+and+dextrocardia%5BTitle%5D)+AND+%22The+Thoracic+and+Cardiovascular+Surgeon%22%5BJournal%5D)">Mitral valve replacement in a patient with situs inversus and dextrocardia.</a> The Thoracic and Cardiovascular Surgeon. 59 (5), 305-306 (2011).</li>
<li>Uchimuro, T., Fukui, T., Matsuyama, S., Tabata, M., Takanashi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mitral+valve+replacement+in+dextrocardia+and+situs+inversus%5BTitle%5D)+AND+%22Kyobu+Geka%22%5BJournal%5D)">Mitral valve replacement in dextrocardia and situs inversus.</a> Kyobu Geka. 65 (10), 858-861 (2012).</li>
<li>Atsumi, Y., Tokunaga, S., Yasuda, S., Fushimi, K., Masuda, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mitral+valve+surgery+in+a+patient+with+dextrocardia+and+180+degrees+counter-clockwise+rotated+heart+due+to+congenital+agenesis+of+the+right+lung%5BTitle%5D)+AND+%22Journal+of+Cardiac+Surgery%22%5BJournal%5D)">Mitral valve surgery in a patient with dextrocardia and 180 degrees counter-clockwise rotated heart due to congenital agenesis of the right lung.</a> Journal of Cardiac Surgery. 28 (6), 635-637 (2013).</li>
<li>Kikon, M., Kazmi, A., Gupta, A., Grover, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Left-sided+approach+for+mitral+valve+replacement+in+a+case+of+dextrocardia+with+situs+solitus%5BTitle%5D)+AND+%22Interactive+Cardiovascular+and+Thoracic+Surgery%22%5BJournal%5D)">Left-sided approach for mitral valve replacement in a case of dextrocardia with situs solitus.</a> Interactive Cardiovascular and Thoracic Surgery. 17 (5), 900-902 (2013).</li>
<li>Khan, J. F., Khan, I., Khan, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mitral+valve+replacement+with+preservation+of+subvalvular+apparatus+in+a+patient+with+familial+dextrocardia+and+situs+solitus%5BTitle%5D)+AND+%22Journal+of+the+College+of+Physicians+and+Surgeons-Pakistan%22%5BJournal%5D)">Mitral valve replacement with preservation of subvalvular apparatus in a patient with familial dextrocardia and situs solitus.</a> Journal of the College of Physicians and Surgeons-Pakistan. 24, Suppl 3 161-162 (2014).</li>
<li>Gillinov, A. M., Blackstone, E. H., McCarthy, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Atrial+fibrillation%3A+current+surgical+options+and+their+assessment%5BTitle%5D)+AND+%22The+Annals+of+Thoracic+Surgery%22%5BJournal%5D)">Atrial fibrillation: current surgical options and their assessment.</a> The Annals of Thoracic Surgery. 74 (6), 2210-2217 (2002).</li>
<li>Song, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Case+report%3A+the+Cox-Maze+IV+procedure+in+the+mirror%3A+the+use+of+three-dimensional+printing+for+pre-operative+planning+in+a+patient+with+situs+inversus+dextrocardia%5BTitle%5D)+AND+%22Frontiers+in+Cardiovascular+Medicine%22%5BJournal%5D)">Case report: the Cox-Maze IV procedure in the mirror: the use of three-dimensional printing for pre-operative planning in a patient with situs inversus dextrocardia.</a> Frontiers in Cardiovascular Medicine. 8, 722413(2021).</li>
<li>Lev, M., Liberthson, R. R., Eckner, F. A., Arcilla, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Pathologic+anatomy+of+dextrocardia+and+its+clinical+implications%5BTitle%5D)+AND+%22Circulation%22%5BJournal%5D)">Pathologic anatomy of dextrocardia and its clinical implications.</a> Circulation. 37 (6), 979-999 (1968).</li>
<li>Cox, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+first+Maze+procedure%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">The first Maze procedure.</a> The Journal of Thoracic and Cardiovascular Surgery. 141 (5), 1093-1097 (2011).</li>
<li>Prasad, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Cox+maze+III+procedure+for+atrial+fibrillation%3A+long-term+efficacy+in+patients+undergoing+lone+versus+concomitant+procedures%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">The Cox maze III procedure for atrial fibrillation: long-term efficacy in patients undergoing lone versus concomitant procedures.</a> The Journal of Thoracic and Cardiovascular Surgery. 126 (6), 1822-1827 (2003).</li>
<li>Gaynor, S. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+prospective%2C+single-center+clinical+trial+of+a+modified+Cox+maze+procedure+with+bipolar+radiofrequency+ablation%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation.</a> The Journal of Thoracic and Cardiovascular Surgery. 128 (4), 535-542 (2004).</li>
<li>Weimar, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+cox-maze+procedure+for+lone+atrial+fibrillation%3A+a+single-center+experience+over+2+decades%5BTitle%5D)+AND+%22Circulation+Arrhythmia+and+Electrophysiology%22%5BJournal%5D)">The cox-maze procedure for lone atrial fibrillation: a single-center experience over 2 decades.</a> Circulation Arrhythmia and Electrophysiology. 5 (1), 8-14 (2012).</li>
<li>Ruaengsri, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Cox-maze+IV+procedure+in+its+second+decade%3A+still+the+gold+standard%5BTitle%5D)+AND+%22European+Journal+of+Cardio-thoracic+Surgery%22%5BJournal%5D)">The Cox-maze IV procedure in its second decade: still the gold standard.</a> European Journal of Cardio-thoracic Surgery. 53, Suppl 1 19-25 (2018).</li>
<li>Badhwar, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Society+of+Thoracic+Surgeons+2017+Clinical+Practice+Guidelines+for+the+surgical+treatment+of+atrial+fibrillation%5BTitle%5D)+AND+%22The+Annals+of+Thoracic+Surgery%22%5BJournal%5D)">The Society of Thoracic Surgeons 2017 Clinical Practice Guidelines for the surgical treatment of atrial fibrillation.</a> The Annals of Thoracic Surgery. 103 (1), 329-341 (2017).</li>
<li>Ad, N., Holmes, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Prediction+of+sinus+rhythm+in+patients+undergoing+concomitant+Cox+maze+procedure+through+a+median+sternotomy%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">Prediction of sinus rhythm in patients undergoing concomitant Cox maze procedure through a median sternotomy.</a> The Journal of Thoracic and Cardiovascular Surgery. 148 (3), 881-886 (2014).</li>
<li>Damiano, R. J., Voeller, R. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Biatrial+lesion+sets%5BTitle%5D)+AND+%22Journal+of+Interventional+Cardiac+Electrophysiology%22%5BJournal%5D)">Biatrial lesion sets.</a> Journal of Interventional Cardiac Electrophysiology. 20 (3), 95-99 (2007).</li>
<li>Lawrance, C. P., Henn, M. C., Damiano, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Surgical+ablation+for+atrial+fibrillation%3A+techniques%2C+indications%2C+and+results%5BTitle%5D)+AND+%22Current+Opinion+in+Cardiology%22%5BJournal%5D)">Surgical ablation for atrial fibrillation: techniques, indications, and results.</a> Current Opinion in Cardiology. 30 (1), 58-64 (2015).</li>
<li>Gammie, J. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+multi-institutional+experience+with+the+CryoMaze+procedure%5BTitle%5D)+AND+%22The+Annals+of+Thoracic+Surgery%22%5BJournal%5D)">A multi-institutional experience with the CryoMaze procedure.</a> The Annals of Thoracic Surgery. 80 (3), 876-880 (2005).</li>
<li>Gaita, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Linear+cryoablation+of+the+left+atrium+versus+pulmonary+vein+cryoisolation+in+patients+with+permanent+atrial+fibrillation+and+valvular+heart+disease%3A+correlation+of+electroanatomic+mapping+and+long-term+clinical+results%5BTitle%5D)+AND+%22Circulation%22%5BJournal%5D)">Linear cryoablation of the left atrium versus pulmonary vein cryoisolation in patients with permanent atrial fibrillation and valvular heart disease: correlation of electroanatomic mapping and long-term clinical results.</a> Circulation. 111 (2), 136-142 (2005).</li>
<li>Ad, N., Henry, L., Hunt, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+concomitant+cryosurgical+Cox-Maze+procedure+using+Argon+based+cryoprobes%3A+12+month+results%5BTitle%5D)+AND+%22The+Journal+of+Cardiovascular+Surgery%22%5BJournal%5D)">The concomitant cryosurgical Cox-Maze procedure using Argon based cryoprobes: 12 month results.</a> The Journal of Cardiovascular Surgery. 52 (4), 593(2011).</li>
<li>Ad, N., Holmes, S. D., Friehling, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Minimally+invasive+stand-alone+Cox+Maze+procedure+for+persistent+and+long-standing+persistent+atrial+fibrillation%3A+perioperative+safety+and+5-year+outcomes%5BTitle%5D)+AND+%22Circulation+Arrhythmia+and+Electrophysiology%22%5BJournal%5D)">Minimally invasive stand-alone Cox Maze procedure for persistent and long-standing persistent atrial fibrillation: perioperative safety and 5-year outcomes.</a> Circulation Arrhythmia and Electrophysiology. 10 (11), 005352(2017).</li>
<li>Song, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cryomaze+ablation+procedure+for+atrial+fibrillation+concomitant+with+valve+surgery%5BTitle%5D)+AND+%22Chinese+Journal+of+Clinical+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">Cryomaze ablation procedure for atrial fibrillation concomitant with valve surgery.</a> Chinese Journal of Clinical Thoracic and Cardiovascular Surgery. 24 (5), 369-373 (2017).</li>
<li>Liu, Y. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Research+on+the+efficacy+and+safety+of+surgical+management+of+atrial+fibrillation+with+two+paths+of+radio-frequency+ablation%5BTitle%5D)+AND+%22Chinese+Journal+of+Clinical+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">Research on the efficacy and safety of surgical management of atrial fibrillation with two paths of radio-frequency ablation.</a> Chinese Journal of Clinical Thoracic and Cardiovascular Surgery. 33 (2), 105-106 (2017).</li>
<li>Lawrance, C. P., Henn, M. C., Damiano, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Concomitant+Cox-Maze+IV+techniques+during+mitral+valve+surgery%5BTitle%5D)+AND+%22Annals+of+Cardiothoracic+Surgery%22%5BJournal%5D)">Concomitant Cox-Maze IV techniques during mitral valve surgery.</a> Annals of Cardiothoracic Surgery. 4 (5), 483-486 (2015).</li>
<li>Ad, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Expert+consensus+guidelines%3A+Examining+surgical+ablation+for+atrial+fibrillation%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">Expert consensus guidelines: Examining surgical ablation for atrial fibrillation.</a> The Journal of Thoracic and Cardiovascular Surgery. 153 (6), 1330-1354 (2017).</li>
<li>Cox, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Intraoperative+options+for+treating+atrial+fibrillation+associated+with+mitral+valve+disease%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">Intraoperative options for treating atrial fibrillation associated with mitral valve disease.</a> The Journal of Thoracic and Cardiovascular Surgery. 122 (2), 212-215 (2001).</li>
</ol>

The authors have no conflicts of interest to disclose.

Dextrocardia is a group of rare heart defects in which the heart is situated on the right side of the thoracic cavity instead of on the left side. One-third of all dextrocardia cases are mirror-image cases, which means the orientation of the cardiac chambers is a mirror image to levocardia (normally situated heart)12. It is estimated that situs inversus dextrocardia associated with situs inversus totalis occurs with an incidence of much less than 1 in 10,000-50,000 births1<...

Dextrocardia is a rare, congenital cardiac malformation in which the axis of the heart is indexed to the right side of the thoracic cavity. Dextrocardia with situs inversus totalis refers to all visceral organs, including the heart, being mirrored and is extremely rare1,2. Atrial fibrillation (AF) is the most common arrhythmia that affects millions of people and causes substantial morbidity and mortality, especially with respect to the increased risk of stroke3.
A literature survey was unable to demonstrate a definitive approach for the concomitant Cox-Maze procedure (CMP) and valve surgery in dextrocardia with situs inversus. There are only a few reports of mitral valve replacement in cases of dextrocardia with situs solitus and even less in situs inversus4,5,6,7,8,9. However, those strategies are not applicable to tricuspid valve surgery, not to mention the complex CMP-IV in dextrocardia.
This paper reports the surgical techniques and experience in three cases concerning the biatrial lesion set of the CMP-IV operation using cryoablation or radiofrequency ablation concomitantly with valve surgery in situs inversus dextrocardia. All surgeries succeeded in the maintenance of sinus rhythm (SR) at 12 months follow-up to each patient and at 48 months follow-up to the previous two. Electron microscopy was used to investigate the transmurality of the atrial cryoablation.
CASE PRESENTATION:
Patients and preoperative examination 
From February 2016 to September 2020, a 48-year-old female patient, a 55-year-old male patient, and a 39-year-old male patient were successively admitted to the cardiac center with similar complaints of palpitation, dyspnea, and easy fatigability on exertion lasting for years (Table 1). They all denied any familiar history of situs inversus dextrocardia or other cardiac health comorbidities. All patients were referred to electrocardiography (ECG), chest roentgenography (Figure 1), computed tomography (CT), and Doppler transthoracic echocardiography (TTE) routinely for preoperative examination.
Case 1: A 48-year-old woman presented with complaints of palpitation, dyspnea, and easy fatigability on exertion lasting for years. The anamnesis was unremarkable. During the physical examination, a grade 3 systolic blowing murmur was heard in the fifth intercostal space outside the midline of the right clavicle. X-ray plain film and CT scan showed that the contour of the dextrocardia was enlarged and situs inversus totalis. Transesophageal echocardiography revealed moderate to severe mitral regurgitation and mild tricuspid regurgitation after moderate mitral valve prolapse and tricuspid annular dilation. There was no thrombosis, and the diameter of the left atrium was 5.3 cm. AF with a rapid ventricular rate was detected by ECG.
Case 2: A 55-year-old man presented with similar symptoms for years. There was no history of cardiac health comorbidities; however, he had had a stroke about six months ago. On physical examination, a diastolic blowing murmur was heard at the left second intercostal space, radiating to the neck. Plain X-ray and CT scan revealed dextrocardia with an enlarged contour and situs inversus totalis. Transesophageal echocardiography showed moderate aortic valve regurgitation and mild to moderate tricuspid regurgitation following mild aortic prolapse and tricuspid annular dilation. The diameter of the left atrium was 4.5 cm without atrial thrombosis. AF with a rapid ventricular rate was detected by ECG.
Case 3: A 39-year-old male presented with progressive exertional dyspnea and intermittent palpitation without any history of situs inversus dextrocardia or other cardiac health complications. During the physical examination, a grade 3 systolic blowing murmur was heard in the fifth intercostal space outside the midline of the right clavicle. X-ray plain film and CT scan revealed that the contour of dextrocardia was enlarged and situs inversus totalis. Transesophageal echocardiography showed severe mitral valve regurgitation and tricuspid regurgitation after annular enlargement. There was no atrial thrombosis, and the left atrium diameter was 5.8 cm. A 24 h ambulatory ECG demonstrated paroxysmal AF with a total load of 165 min.
Diagnosis, assessment, and plan 
Case 1: A biatrial cryo-Cox-Maze IV procedure (cryo-CMP-IV) with mechanic mitral valve replacement and tricuspid annuloplasty were simultaneously performed.
Case 2: A biatrial cryo-CMP-IV procedure with concomitant mechanic aortic valve (AV) replacement and tricuspid annuloplasty was performed.
Case 3: A biatrial CMP-IV procedure, mitral valvuloplasty, and tricuspid annuloplasty were performed simultaneously.

<table><tbody><tr><td>CryoICE</td><td>AtriCure, Cincinnati, Ohio</td><td>CRYO2</td><td>Cryoablation in case 1 and case 2 was performed exclusively using it with a flexible 10cm in length metal cryoprobe.</td></tr><tr><td>Medtronic Open Pivot Standard mechanical MV</td><td>Medtronic, Minneapolis, Minn</td><td>709291 / MHV 500DM27 STD MITRAL</td><td>A 27-mm MV was adopted in case 1.</td></tr><tr><td>Medtronic Open Pivot Standard mechanical AV</td><td>Medtronic, Minneapolis, Minn</td><td>646871 / MHV 500FA23 STD AORTIC</td><td>A 23-mm AV was adopted in case 2.</td></tr><tr><td>bipolar radiofrequency pen</td><td>AtriCure Inc., Cincinnati, OH</td><td></td><td>Maze-IV in case 3</td></tr><tr><td>bipolar radiofrequency clamps</td><td>AtriCure Inc., Cincinnati, OH</td><td></td><td>Maze-IV in case 3</td></tr><tr><td>Goretex</td><td>W.L. Gore &amp;amp; Associates, Inc., Elkton, Maryland</td><td></td><td>A surgical suture made of polytetrafluoroethylene.</td></tr><tr><td>rigid mitral ring</td><td>Kingstron Bio, Suzhou, China</td><td>Element Force ARM32</td><td>A 32 mm ring was adopted in case 3.</td></tr><tr><td>Tricuspid Sovering Band</td><td>Sorin Group Italia S.r.l., VC, Italy</td><td>SBG0730 / SB30T</td><td>A 30 mm ring was adopted in case 1.</td></tr><tr><td>Tricuspid Sovering Band</td><td>Sorin Group Italia S.r.l., VC, Italy</td><td>SQB0240 / SB30T</td><td>A 30 mm ring was adopted in case 2.</td></tr><tr><td>Tricuspid Sovering Band</td><td>Sorin Group Italia S.r.l., VC, Italy</td><td>SBF0930 / SB28T</td><td>A 28 mm band was adopted in case 3.</td></tr></tbody></table>

cox-maze iv procedure concomitant with valvular surgery in situs inversus dextrocardia: a single-center experience in china

Atrial fibrillation (AF) is the most common cardiac arrhythmia. The use of ablation technologies made the Cox-Maze IV procedure (CMP-IV) technically easier, faster, becoming the gold standard for the surgical treatment of AF. However, the efficacy and safety of CMP-IV in situs inversus dextrocardia are largely unknown. This paper summarizes the CMP-IV procedure performed concomitantly with valvular surgery in patients with situs inversus dextrocardia at this institution.
From February 2016 to September 2020, three dextrocardia patients with persistent AF and valvular diseases were referred to this institution for valvular and CMP-IV surgery. CMP-IV was performed using either cryoablation with a nitrous oxide (N2O)-based cryoprobe or a bipolar radiofrequency clamp and bipolar radiofrequency pen. Mechanical valve replacement or mitral vavuloplasty was performed in another patient in addition to tricuspid annuloplasty. Transmurality of the ablated atrial tissues was evaluated by electron microscopy. Heart function was assessed by transthoracic echocardiography. Cardiac rhythm was monitored by 24 h Holter at 3, 6, 12, 18, 24, and 48 months follow-up. 
All the AF was successfully eliminated in the ablation procedure without recurrence or other complications during hospitalization. The mean bypass and crossclamp times were similar in all the patients. The postoperative ventilator support time, the duration of stay in the ICU, and postoperative residence time were also not significantly different among the patients. Transmural atrial necrosis was detected in the ablated atrial tissues. Sinus rhythm maintenance was achieved at 3, 6, 12, 18, 24, and 48 months follow-up in all the patients. All valve protheses switched freely; no tricuspid regurgitation was observed. The results of the present study demonstrate that the CMP-IV is safe and effective in eliminating AF in dextrocardia patients concomitant with valvular surgery.

Surgical procedure and early postoperative period 
A mechanic MV replacement, tricuspid annuloplasty, and concomitant cryo-CMP-IV were performed simultaneously for the first patient. The second had undergone surgery of mechanic AV replacement, tricuspid annuloplasty, and concomitant cryo-CMP-IV. In the third patient, a biatrial CMP-IV procedure was performed simultaneously with mitral valvuloplasty and tricuspid annuloplasty. All operations were smooth, and each beating heart restored SR after resus...

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Cox-Maze IV Procedure Concomitant with Valvular Surgery In Situs Inversus Dextrocardia: A Single-Center Experience in China

We summarize the Cox-Maze IV procedure concomitant with valvular surgery performed in patients with situs inversus dextrocardia at this institution.

Atrial fibrillation (AF) is the most common cardiac arrhythmia. The use of ablation technologies made the Cox-Maze IV procedure (CMP-IV) technically ...

cox-maze-iv-procedure-concomitant-with-valvular-surgery-situs

Research

JoVE Journal

Medicine

3.4K Views.  Central South University. We summarize the Cox-Maze IV procedure concomitant with valvular surgery performed in patients with situs inversus dextrocardia at this institution.

Video: Cox-Maze IV Procedure Concomitant with Valvular Surgery In Situs Inversus Dextrocardia: A Single-Center Experience in China

Echocardiographic Approaches and Protocols for Comprehensive Phenotypic Characterization of Valvular Heart Disease in Mice

The aim of this manuscript and accompanying video is to provide an overview of the methods and approaches used for imaging heart valve function in rodents, with detailed descriptions of the appropriate methods for anesthesia, the echocardiographic windows used, the imaging planes and probe orientations for image acquisition, the methods for data analysis, and the limitations of emerging technologies for the evaluation of cardiac and valvular function. Importantly, we also highlight several future areas of research in cardiac and heart valve imaging that may be leveraged to gain insights into the pathogenesis of valve disease in preclinical animal models. We propose that using a systematic approach to evaluating cardiac and heart valve function in mice can result in more robust and reproducible data, as well as facilitate the discovery of previously underappreciated phenotypes in genetically-altered and/or physiologically-stressed mice.

This protocol provides a detailed description of the echocardiographic approach for comprehensive phenotyping of heart and heart valve function in mice.

The aim of this manuscript and accompanying video is to provide an overview of the methods and approaches used for imaging heart valve function in ...

Optimization of the Cuff Technique for Murine Heart Transplantation

Murine cardiac transplantation has been performed for more than 40 years. With advancements in microsurgery, certain new techniques have been used to improve surgical efficiency. In our lab, we have optimized the cuff technique with two major steps. First, we used the inner tube technique to insert a temporary inner tube into the external jugular vein and carotid artery blood vessel to facilitate eversion of the vessel over the cuff. Second, we performed complete heterotopic cardiac transplantation through the collaboration of two experienced surgeons. These modifications effectively reduced the operation time to 25 minutes, with a success rate of 95%. In this report, we describe these procedures in detail and provide a supplemental video. We believe that this report on the improved cuff technique will offer practical guidance for murine heterotopic heart transplantation and will enhance the utility of this mouse model for basic research.

We introduce an inner tube approach to the cuff technique for mouse cervical heterotopic heart transplantation to help evert the vessel over the cuff. We found that cooperation between two experienced surgeons markedly shortens the operation time.

Murine cardiac transplantation has been performed for more than 40 years. With advancements in microsurgery, certain new techniques have been used to ...

Immunology and Infection

Biventricular Assessment of Cardiac Function and Pressure-Volume Loops by Closed-Chest Catheterization in Mice

Assessment of cardiac function is essential to conduct cardiovascular and pulmonary-vascular preclinical research. Pressure-volume loops (PV loops) generated by recording both pressure and volume during cardiac catheterization are vital when assessing both systolic and diastolic cardiac function. Left and right heart function are closely related, reflected in ventricular interdependence. Thus, recording biventricular function in the same animal is important to get a complete assessment of cardiac function. In this protocol, a closed chest approach to cardiac catheterization consistent with the way catheterization is performed in patients is adopted in mice. While challenging, the closed chest strategy is a more physiological approach, because opening the chest results in major changes in preload and afterload that create artifacts, most notably a fall in systemic blood pressure. While high-resolution echocardiography is used to assess rodents, cardiac catheterization is invaluable, particularly when assessing diastolic pressures in both ventricles.
Described here is a procedure to perform invasive, closed chest, sequential left and right ventricular pressure-volume (PV) loops in the same animal. PV loops are acquired using&#160;admittance technology with a mouse pressure-volume catheter and pressure-volume system acquisition. The procedure is described, beginning with the neck dissection, which is required to access the right jugular vein and the right carotid artery, to the insertion and positioning of the catheter, and finally the data acquisition. Then, the criteria required to ensure the acquisition of high-quality PV loops are discussed. Finally, the analysis of the left and right ventricular PV loops and the different hemodynamic parameters available to quantify systolic and diastolic ventricular function are briefly described.

Presented here is a protocol to assess biventricular heart function in mice by generating pressure-volume (PV) loops from the right and left ventricle in the same animal using closed chest catheterization. The focus is on the technical aspect of surgery and data acquisition.

Assessment of cardiac function is essential to conduct cardiovascular and pulmonary-vascular preclinical research. Pressure-volume loops (PV loops) ...

A Doxorubicin-Induced Murine Model of Dilated Cardiomyopathy In Vivo

Dilated cardiomyopathy (DCM) refers to a spectrum of heterogeneous myocardial disorders characterized by ventricular dilation and depressed cardiac performance in the absence of hypertension, valvular, congenital, or ischemic heart diseases, and which may be related to infection, autoimmune or metabolic abnormalities, or family inheritance. It can progress into congestive heart failure with a poor prognosis. Doxorubicin (Dox) is widely employed as a chemotherapeutic drug, but its use is limited because it causes DCM-like changes of the myocardium. Its myocardial toxicity is attributed to oxidative stress, chronic inflammation, and cardiomyocyte apoptosis. A model of DCM exploiting these Dox-induced DCM symptoms has not been established.

Described is a protocol to establish a Doxorubicin-induced dilated cardiomyopathy (DCM) model in mice via long-term intraperitoneal injection of Doxorubicin.

Dilated cardiomyopathy (DCM) refers to a spectrum of heterogeneous myocardial disorders characterized by ventricular dilation and depressed cardiac ...

A Simplified Stepwise Approach to Echo Guidance during Percutaneous Mitral Valve Repair

Percutaneous transcatheter edge-to-edge reconstruction of the mitral valve is a safe and well-established therapy for severe symptomatic mitral regurgitation in patients with high surgical risk. Echocardiographic guidance in addition to fluoroscopy is the gold standard and should be performed using a standardized technique.
This article lays out our reproducible step by step echocardiographic guide including views, measurements as well as highlighting possible difficulties that may arise during the procedure.
This article provides detailed and chronological echocardiographic views for each step of the procedure, especially preferences between 2D and 3D imaging. If needed, pulse wave, continuous wave and color doppler measurements are described. Furthermore, as there are no official recommendations for the quantification of mitral regurgitation during the percutaneous edge-to-edge-repair procedure, advice is also included for echocardiographic quantification after grasping the mitral leaflets and after device deployment. In addition, the article deals with important echocardiographic views to prevent and deal with possible complications during the procedure.
Echocardiographic guidance during transcatheter mitral valve repair is mandatory. A structured approach improves the collaboration between interventionist and imager and is indispensable for a safe and effective procedure.

This protocol presents in detail how to perform real-time echocardiographic guidance during transcatheter mitral valve repair. The fundamental views and the necessary measurements are described for each stage of the procedure.

Percutaneous transcatheter edge-to-edge reconstruction of the mitral valve is a safe and well-established therapy for severe symptomatic mitral ...

Modifications of the Langendorff Method for Simultaneous Isolation of Atrial and Ventricular Myocytes from Adult Mice

A single cardiomyocyte is a vital tool in the cellular and subcellular level studies of cardiac biology and diseases as a fundamental unit of contraction and electrical activity. Hence, isolating viable, high-quality cardiomyocytes from the heart is the initial and most crucial experimental step. Comparing the various protocols for isolating the cardiomyocytes of adult mice, the Langendorff retrograde perfusion is the most successful and reproducible method reported in the literature, especially for isolating ventricular myocytes. However, isolating quality atrial myocytes from the perfused heart remains challenging, and few successful isolation reports are available. Solving this complicated problem is extremely important because apart from ventricular disease, atrial disease accounts for a large part of heart diseases. Therefore, further investigations on the cellular level to reveal the mechanisms are warranted. In this paper, a protocol based on the Langendorff retrograde perfusion method is introduced and some modifications in the depth of aorta cannulation and the steps that may affect the digestion process to isolate atrial and ventricular myocytes were simultaneously made. Moreover, the isolated cardiomyocytes are confirmed to be amenable to patch clamp investigation.

This protocol describes modifications of the Langendorff method including the depth of aorta cannulation for simultaneous Isolation of atrial and ventricular myocytes from adult mice.

A single cardiomyocyte is a vital tool in the cellular and subcellular level studies of cardiac biology and diseases as a fundamental unit of contraction ...

Generation and Characterization of Right Ventricular Myocardial Infarction Induced by Permanent Ligation of the Right Coronary Artery in Mice

Right ventricular infarction (RVI) is a common presentation in clinical practice. Severe RVI can lead to fatal hemodynamic dysfunction and arrhythmia. In contrast to the extensively used mouse myocardial infarction (MI) model generated by left coronary artery ligation, the RVI mouse model is rarely employed due to the difficulty associated with model generation. Research on the mechanisms and treatment of RVI-induced RV remodeling and dysfunction requires animal models to mimic the pathophysiology of RVI in patients. This study introduces a feasible procedure for RVI model generation in C57BL/6J mice. Further, this model was characterized based on the following: infarct size evaluation at 24 h after MI, assessment of cardiac remodeling and function with echocardiography, RV hemodynamics assessment, and histology of the infarct zone at 4 weeks after RVI. In addition, a coronary vasculature cast was performed to observe the coronary arterial arrangement in RV. This mouse model of RVI would facilitate the research on mechanisms of right heart failure and seek new therapeutic targets of RV remodeling.

There are several differences between the right and left ventricles. However, the pathophysiology of right ventricular infarction (RVI) has not been clarified. In the present protocol, a reproducible method for RVI mouse model generation is introduced, which may provide a means to explain the mechanism of RVI.

Right ventricular infarction (RVI) is a common presentation in clinical practice. Severe RVI can lead to fatal hemodynamic dysfunction and arrhythmia. In ...

Fully Endoscopic Mitral Valve Repair with Percutaneous Cannulation of Groin Vessels

Endoscopic mitral valve surgery (EMS) has become a standard of care at specialized heart centers, further reducing surgical trauma compared to a traditional minimally invasive, thoracotomy-based approach. Exposure of the groin vessels for the establishment of cardiopulmonary bypass (CPB) via surgical cutdown in minimally invasive surgery (MIS) may result in wound healing disorders or seroma formation. The avoidance of surgical exposure of the groin vessels by using fully percutaneous techniques for the insertion of a CPB cannula with the implementation of vascular pre-closure devices has the potential to reduce these complications and improve clinical results. Herein, we present the utilization of a novel plug based vacsular closure device with a resobable collagen plug and the absence of suture material for closure of the arterial access for CPB in MIS. While this device was initially predominantly used in transcatheter aortic valve implantation (TAVI) procedures, with its safety and feasibility shown, we herein show that it can be used in CPB cannulation, since it is capable of closing arterial access sites up to 25 French (Fr.) in size. This device may be suitable to significantly reduce groin complications in MIS and simplify the establishment of CPB. Here, we describe the fundamental steps of EMS, including percutaneous groin cannulation and decannulation using a vascular closure device.

This protocol demonstrates in detail how to perform fully endoscopic mitral valve surgery (EMS) with percutaneous cannulation of the groin vessels, using a percutaneous plug-based vascular closure device. Fundamental steps and useful instructions are described in detail for each step.

Endoscopic mitral valve surgery (EMS) has become a standard of care at specialized heart centers, further reducing surgical trauma compared to a ...

Surgically Induced Cardiac Volume Overload by Aortic Regurgitation in Mouse

Aortic regurgitation (AR) is a common valvular heart disease that exerts volume overload on the heart and represents a global public health problem. Although mice are widely applied to shed light on the mechanisms of cardiovascular disease, mouse models of AR, especially those induced by surgery, are still paucity. Here, a mouse model of AR was described in detail which is surgically induced by disruption of the aortic valves under high-resolution echocardiography. In accordance with regurgitated blood flow, AR mouse hearts present a distinctive and clinically relevant volume overload phenotype, which is characterized by eccentric hypertrophy and cardiac dysfunction, as evidenced by echocardiographic and invasive hemodynamic evaluation. Our proposal, in a reliable and reproducible manner, provides a practical guide on the establishment and assessment of a mouse model of AR for future studies on molecular mechanisms and therapeutic targets of volume overload cardiomyopathy.

This protocol presents a practical guide on the surgery for creation of aortic regurgitation (AR) in the mouse. Assessment of the AR mouse by echocardiography and invasive hemodynamic measurement recapitulates its clinically relevant characteristics of volume overload-induced eccentric hypertrophy, suggesting its promising application in the study of cardiac hypertrophy.

Aortic regurgitation (AR) is a common valvular heart disease that exerts volume overload on the heart and represents a global public health problem. ...

Biology

A Modified Technique for Transverse Aortic Constriction in Mice

Transverse aortic constriction (TAC) is a frequently used surgery in research regarding heart failure and cardiac hypertrophy based on the formation of pressure overload in mouse models. The main challenge of this procedure is to clearly visualize the transverse aortic arch and precisely band the target vessel. Classical approaches perform a partial thoracotomy to expose the transverse aortic arch. However, it is an open-chest model that causes a rather large surgical trauma and requires a ventilator during the surgery. To prevent unnecessary trauma and simplify the operating procedure, the aortic arch is approached via the proximal proportion of the sternum, reaching and binding the target vessel using a small self-made retractor that contains a snare. This procedure can be conducted without entering the pleura cavity and does not need a ventilator or microsurgical operation, which leaves the mice with physiological breathing patterns, simplifies the procedure, and significantly reduces operation time. Due to the less invasive approach and less operation time, mice can undergo fewer stress reactions and recover rapidly.

The present protocol describes a modified and simplified technique with a minimally invasive transverse aortic constriction (TAC) procedure using a self-made retractor. This procedure can be conducted without a ventilator or microscope and introduces pressure overload, eventually leading to cardiac hypertrophy or heart failure.

Transverse aortic constriction (TAC) is a frequently used surgery in research regarding heart failure and cardiac hypertrophy based on the formation of ...