Hybrid Procedure:
The hybrid convergent procedure has been previously described in detail.3,5,6 To briefly summarize our surgical experience, preoperative evaluation included an echocardiogram and an ischemic evaluation. General anesthesia was used for all cases. Initially, a laparoscopic approach with an upper midline abdominal incision and the placement of a single incision laparoscopic surgery (SILS) Port was used. Insufflation and two working ports (including a grasper and a harmonic scalpel via the SILS port) allowed us to gain access into the pericardial space via the bare area of diaphragm just medial to the falciform ligament, above the left lobe of the liver. After a year or so, our approach changed. We were able to perform a similar subxiphoid incision without laparoscopy (saving time and cost) by packing the stomach and omentum off to the patient’s left with a moist sponge and using two appendiceal retractors to expose the bare area of the diaphragm. A long-tipped low-power Bovie was used to divide the diaphragm and access the pericardial space.
Once access was obtained with the cannula and laparoscope, the ablation was carried out beginning at the pericardial reflection against the medial side of the right superior pulmonary vein (PV). We moved from superior to inferior along the left atrium (LA), medial to the right PV and down to the level of the inferior vena cava (IVC). This movement was repeated on the patient’s left. We ablated to the coronary sinus, taking care to overlap lesions. We then moved underneath the left inferior PV and attempted ablation on the left anterior portion of the left PVs. In approximately two-thirds of cases, we could observe catheter placement up to the base of the left atrial appendage (LAA). In one-third of cases, we could not see the anterior portion of the left PVs due to hemodynamic instability. For these cases, we would place three or four lesions blindly.
After left anterior PV ablation, we ablated the anterior portion of the right PVs. With each ablation, we instilled 25 cc of room-temperature saline into the pericardial wall through the cannula to avoid thermal conduction to other mediastinal structures. Once finished, we placed a silastic drain through a separate incision. We infused 500 mg of solumedrol through the drain and let it sit while we closed the incision in a standard manner. The drain was hooked to bulb suction and removed on the day of discharge. After the surgeon completed the epicardial ablation, all chest incisions and drains were covered in a sterile fashion. Then, the endocardial evaluation and intervention by the electrophysiologist commenced.
After baseline intervals and pacing thresholds were measured, RA and RV pacing at fixed incremental cycle lengths were performed. The first half of the initial heparin bolus was then given, and the maintenance infusion was started after the diagnostic catheters were in position. The cryoballoon (CB) process of PV isolation began after transvenous access and transeptal puncture. At that point, an exchange length wire was advanced to the left superior PV to exchange for a 12F FlexCath sheath in place of a SL-1 sheath. The second half of the heparin bolus was given after the left atrium was entered. A preoperative computed tomography scan with contrast of the LA and PVs was used to evaluate LA size, PV anatomy (including any anomalies), and the PV ostium. Depending on the size of the ostium, a 23/28mm Artic Front CB catheter with a spiral 15/20mm Achieve wire was advanced sequentially to all PVs, the anterior and posterior walls of the LA, and the roof of the LA. Using a field filter of 0.1 mV, each area was mapped to evaluate for isolation. Pacing, using the Achieve catheter, was performed to verify non-capture at the antrum/ostium of each PV as well as the posterior wall. Entrance and exit block were confirmed in all pulmonary veins. A 3D anatomical map was performed of the LA (specifically the roof), posterior walls, and all PVs. This was done to verify PV and posterior wall isolation. Posterior wall isolation was homogenous, starting at the level of the superior PVs down to the level of the right and left inferior PVs.
It was generally identified that the anterior/superior turnaround borders of the left and right superior PVs were not completely isolated, especially the ridge between the left superior PV and the LAA. Rarely, the inferior/posterior borders of the left and right inferior PV were also still connected. When the PVs were not completely isolated, cryo-energy was delivered to complete the isolation. Care was taken to verify that the esophageal temperature probe was positioned directly behind the PV we were isolating or the posterior wall we were ablating. The goal was to achieve approximately -40 degrees Celsius for 4 minutes. When PV signals were present on the Achieve catheter, we strove to isolate these signals or eliminate them altogether within the first 60 seconds. If this was not achieved, we would reposition the balloon catheter to find a better fit and seal. Care was taken to verify that the esophageal temperature did not fall below -30 degrees Celsius.
When delivering cryo-energy along the right-sided PVs, a quadripolar catheter was often positioned in the right subclavian vein to pace the right phrenic nerve. A fetal monitor was placed on the patient’s abdomen to audibly monitor right hemidiaphragm contractility. Cryo-energy delivery to the right-sided pulmonary veins was stopped when the intensity of diaphragmatic contractility began to diminish. When the endocardial posterior roof line was not complete, a 4 mm tipped deflectable, irrigated tipped electrode was used to deliver radiofrequency using 20-25 watts for 30-60 seconds. If the esophageal temperature probe temperature rose > 1 degree Celsius, ablation was stopped, and the area was allowed to return to baseline temperature before another ablation lesion was delivered nearby, but not in the same location. The goal was elimination of endocardial signals > 0.1 mV and lack of pacing response from the ablated area.
When all PVs and the posterior wall were isolated and the posterior roofline was completed, we would continue to pace and remap for 20 minutes after the last ablation. Isoproterenol up to 5 mcg/min was often infused during this waiting period. Sometimes intravenous adenosine 6 and 12 mg were used after the 20-minute waiting period. If there was no reconnection of PVs or posterior wall, then the ablation was terminated. Post ablation, no significant signals above 0.1 mV were observed. Likewise, pacing along the line failed to capture atrial tissue. After PVI, RA, and RV incremental pacing and programmed stimulation were performed. No arrhythmias were inducible. Intracardiac echocardiography was used to rule out pericardial effusion as well as to measure PV velocities pre- and post-procedure. Heparin was reversed with intravenous protamine by the anesthesia service.