Surgical procedure
RA, bipolar, transmurality
WEST, ARRESTED
All the CMIV procedures were performed under cardiopulmonary bypass (CPB) with median sternotomy. To reduce the variation among surgeons, we require the CMIV to be performed by qualified surgeons. After the initiation of normothermic CPB, both sets of pulmonary veins are then bluntly dissected, mobilized, and encircled with a urine catheter. Lesions from right atrial (RA) lesion set are performed on the beating heart and with temperature cooled to 34°C. Then, a small purse-string suture is placed at the base of the RA appendage that is wide enough to accommodate one jaw of the bipolar radio frequency (RF) ablation clamp. An ablation lesion is created along the free wall of the right atrium through the purse string down the aortic side of the RA appendage. A vertical right atriotomy is made extending from the intra-atrial septum up towards the atrioventricular groove near the free margin of the heart (at least 2 cm from the free wall ablation). From the inferior aspect of the incision, the RF ablation clamp is used to create ablation lines up to the superior vena cava and down towards the inferior vena cava. A linear cryoprobe is used to create an endocardial ablation line from the superior aspect of this atriotomy down onto the tricuspid annulus at the 2 o’clock position. All cryoablations are performed for 3 min at a temperature below −60°C. The linear cryoprobe is then inserted through the previously placed purse-string suture, and an endocardial ablation line is created down to the tricuspid annulus at the 10 o’clock position. Next, the left atrial lesion set is performed on the arrested heart after aortic cross-clamping. The heart is retracted, and the left atrial appendage (LAA) is exposed and amputated. Through the amputated appendage, the bipolar RF clamp is used to create a connecting lesion into the left inferior pulmonary vein. The LAA is then oversewn in two layers with a running polypropylene suture. The coronary sinus is marked with methylene blue between the right and the left coronary circulations. A standard left atriotomy is then performed, and the bipolar clamp is used to create ‘roof’ and ‘floor’ lesions from the superior and inferior aspects of the atriotomy to the left superior and inferior pulmonary veins, respectively. The RF ablation clamp is also used to create an ablation from the inferior margin of the atriotomy towards the mitral annulus and across the coronary sinus. As the RF bipolar clamp cannot reach the annulus itself, a bell-shaped cryoprobe is used to make an endocardial lesion to the mitral annulus at the end of the mitral isthmus lesion. To complete the left atrial isthmus ablation, an epicardial cryoablation is performed over the coronary sinus in line with the endocardial lesion. The energy source used for each procedure was AtriCure Inc., West Chester, OH, USA. It was repeated three to four times for every ablation to ensure the transmurality. Concomitant cardiac surgery was performed after ablation; for patients with severe coronary artery disease, coronary artery graft bypass was a priority to ensure sufficient cardioplegic solution perfusion.