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

The efficacy and safety of the Cox-Maze IV procedure in dextrocardia are largely unknown. This protocol summarizes the procedure concomitantly with the vulvular surgery performed in three patients with dextrocardia. CMP4 is safe and effective in eliminating atrial fibrillation in dextrocardia.

Moreover, the 3D-printed heart model helps preoperative simulating and planning for the surgical ablation of AF.Begin the surgical procedure for a median sternotomy by cannulating the superior and inferior vena cava to establish a mild hypothermic cardiopulmonary bypass, or CPB. After establishing the bypass, have an operator switch position from the right side to the left of the operating table. To achieve cardioplegic arrest, give an antegrade cold-blood cardioplegia intermittently from the aortic root.

Then, perform the right atrial incision on the left side of the heart parallel to the atrioventricular sulcus. Ensure the left-sided left atriotomy is located parallelly under the interatrial groove. Place a retractor on the wall of the left atrium, or LA.For cryoablation, design a cryolesion set to replicate the mirror image of the CMP4 lesion set and maintain the duration of the LA cryoablation for each lesion at minus 60 degrees Celsius for two minutes.

After confirming that the posterior LA box lesion is composed of an LA incision and cryolesion encircling the left and right pulmonary veins, apply a cryolesion line connecting the left superior pulmonary vein with the left atrial appendage, or LAA. Then, form an ice ball to mark the coronary sinus using cryoablation from the epicardium. When performing the mitral isthmus line, place the cryoprobe at the inferior aspect of the left atriotomy and direct the tube to the mitral annulus at the 8:00 position across the posterior LA and coronary sinus, as marked with the ice ball.

Then, apply right-sided LAA amputation. After the LA cryoablation, sample a 4×8-millimeter tissue of the cryoablated LA for the electron microscopic examination and sample a large non-ablated tissue from the margin of the LA incision for the control test. Perform the prosthetic valve replacement surgery with a 27-millimeter mechanical mitral valve or a 23-millimeter mechanical atrium valve using a 2-0 polypropylene running suture.

With the heart warm and beating, perform the right atrium cryoablation during the cardiopulmonary bypass for two minutes at minus 60 degrees Celsius for each ablation lesion. Create the linear cryoablation lines from the inferior aspect of the left-sided right atriotomy up onto the superior vena cava and down to the inferior vena cava. Make a tricuspid isthmus linear cryolesion from the mid-portion of the right atriotomy directed endocardially toward the tricuspid annulus at the 10:00 position, followed by a lateral cryolesion from the mid-portion of the right atriotomy up to the tip of the right atrial appendage, or RAA.

Use the derived cardiac CT data to perform a 3D printing of the heart. During the operation, access the left atrium through the interatrial groove and extend the mitral isthmus lesion to the posterior mitral annulus. Then, ablate the coronary sinus in the endocardium and epicardium with a bipolar radiofrequency pen.

Make the other lesions using bipolar radiofrequency clamps as described in the manuscript. When done, dissect the Marshall ligament and separate the left atrial appendage using an epicardial atrial clamp closure device. Then, use bipolar radiofrequency forceps to ablate the entire right atrial lesion sets.

After resecting the A1-ruptured cordi, implant a single, flexible, artificial cord with 4-0 expanded polytetrafluoroethylene in situ and close the residual leak of the anterior commissure and the A2 leaflet cleft. To stabilize the annulus, implant a 32-millimeter rigid mitral ring, ensuring the coaptation height is nine millimeter. After deairing and closure of the interatrial sulcus incision, remove the aortic clamp and then make a longitudinal incision on the surface of the right atrium.

Perform the tricuspid annuloplasty by implanting a 30-millimeter tricuspid ring in an upside-down and mirror image inversion manner using 2-0 polyester interrupted sutures. Remove the holder before fixation of the annuloplasty ring. Ensure that the patient’s sinus rhythm is restored without any atrial ventricular block before cardiopulmonary bypass weaning.

After the cardiac surgery, fix temporary epicardial pacing wires. In the postoperative course during the hospital stay, atrial fibrillation or no other complications were observed in any patient. After discharge, all the patients were followed up for one to three years, the 3, 6, 12, 18, 24 and 36 months follow-up in two patients, and at 3, 6, and 12 months follow-up in a patient was carried out.

At three months after the surgery, all the heart functional capacities were improved to New York Heart Association Class I.The electron microscope of the samples collected from the cryoablated left atrium displayed tissue necrosis in the endocardium and muscularis. However, only edema and degeneration were observed in the epicardium and neighboring muscularis. The lesion set in dextrocardia should be designed to replicate the mirror image of the CMP4 lesion set.

The tricuspid band must be implanted in an upside-down and mirror image inversion manner. Following this procedure, other methods, including chemical and physical ablation, can be performed using the biatrial lesion set of the CMP4 operation. However, cryoablation is the most recommended for valve surgery concomitant surgical ablation.

The 3D-printed heart model displaying the spatial relationship between the specific ablation lines and the key anatomical references may help simulate and modify the CMP4 procedure, especially in patients with rare malformations.