Thoracoscopic Epicardial Ventricular Ablation
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The authors present the case of hybrid endocardial and epicardial ablation in this 73-year-old man with monomorphic PVCs with 25-33% burden and degenerated left ventricle ejection fraction with dilated cardiomyopathy.
Prior endocardial ablation done 3 1/2 years ago focused on RVOT and was not effective. It suggested an epicardial LV summit source based on activation timing and pattern. The patient was brought back for anticipated hybrid epicardial and endocardial ablation. Endocardial mapping and ablation involved the use of intracardiac echo and CARTO-3 electro-anatomic navigation system for right ventricle outflow tract mapping as well as retro-aortic access to the aortic sinuses and left ventricle outflow tract. This was followed by ablation in LVOT below the left aortic cusp. The surgical epicardial part was done in the EP lab after endocardial mapping and ablation were performed. The patient was kept on the EP table in the supine position, avoiding any movement relative to the electro-anatomic navigation magnet. The approach is a standard supine left thoracoscopic with camera port in the fourth or fifth intercostal space laterally and working ports triangulating at suitable distances from the camera port. The pericardial sac was open anterior to the left phrenic nerve using electrocautery or ultrasonic scalpel to get to the summit of the left ventricle. The incision should be anterior to the phrenic nerve. Particular attention was paid to avoid injuring vital structures, particularly the phrenic nerve, the left atrial appendage, and the left pulmonary artery. Anatomical landmarks were defined, including the anterior descending coronary and its accompanying anterior interventricular vein, the diagonal coronary, the greater cardiac vein, and the left atrial appendage. These define the triangle of the left ventricle summit.
Electrophysiologic testing and mapping was performed using a variety of tools such as an electrophysiologic catheter, surgical pacing, and sensing wand. A useful trick is to tie up an electrophysiologic catheter to endoscopic endo-Kittner in order to have precise positioning of the catheter at mapping epicardial sites. The epicardial activation mapping data was processed by the electro-anatomic navigation system and used to detect earliest activation site and thus ablation targets. Epicardial ablation could be achieved using radiofrequency or cryoablation tools precisely at the selected site. In this case, cryoablation was chosen due to the obvious proximity to coronary arteries. Cryoablation might provide more precise placement of lesions and more comfort in proximity to coronary arteries. The cryoablation is typically three minutes long with appropriate confirmation both by temperature measurement as well as visual feedback of adequate delivery. In this case, three different lesions were sequentially delivered creeping up superiorly into the apex of the summit triangle of the left ventricle. Instantaneous favorable result was confirmed by absence of any PVC for more than 15 minutes. A thoracic drain was inserted via the left fifth intercostal port and the surgery was completed.
Rare PVCs were recorded for two days of hospital stay and favorable medium term results confirmed two weeks later by absence of any PVCs on outpatient electrocardiogram.
Yamada T, McElderry HT, Doppalapudi H, Okada T, Murakami Y, Yoshida Y, et al. Idiopathic ventricular arrhythmias originating from the left ventricular summit: anatomic concepts relevant to ablation. Circ Arrhythm Electrophysiol. 2010;3(6):616‐623.
Tamim Antaki has a consultant agreement with Atricure, Inc.