Comprehensive surgical approach to treat atrial fibrillation in patients with variant pulmonary venous anatomy.

OBJECTIVES: Catheter radiofrequency ablation procedures yield fairly successful results for the treatment of atrial fibrillation; however, patients with anatomic variant pulmonary veins (PV) are generally thought not to benefit from catheter ablation technique, with recurrence rates observed as high as 78%. We report a comprehensive surgical approach to treat this subset of patients with a modified full maze procedure. METHODS: From January 2002 to December 2009, 72 patients undergoing cardiac surgery who had drug-refractory and/or recurrent AF after catheter ablation were identified. PV variance was observed on preoperative multislice chest computed tomography. All patients underwent multiple PV epicardial circumferential isolation and epicardial-endocardial longitudinal PV ablations along with standard maze as an adjunct to the cardiac surgical procedure. Patients were followed up at 6 months, 1 year, and 2 years postoperatively. RESULTS: Typical patterns of PV variation were observed in 72 patients. Left common PV trunk was found in 49 patients (68%), with a mean length of 21 ± 4.6 mm, diameter of 28.6 ± 4.9 mm, and wall thickness of 2.1 ± 1.7 mm. Right PV variants, including right middle and right top PVs, were found in 23 patients (32%), with a length of 20 ± 2.1 mm, diameter of 9.9 ± 3.4 mm, and wall thickness of 1.9 ± 1.7 mm. Overall restoration of sinus rhythm was confirmed in 64 patients (94%) at 1-year follow-up. Twelve patients were defibrillated into sinus rhythm within 90 days after the operation. CONCLUSIONS: A modified full maze procedure should be considered as a first choice treatment for atrial fibrillation with variant drainage of PVs because of the nature of PV size, wall thickness, and specific foci in the arrhythmogenic veins. Multiple PV isolation and epicardial-endocardial longitudinal PV ablations along with the standard maze are essential to success. Early referral for surgical ablation allows higher success rates.

The role of approximate entropy in predicting ventricular defibrillation threshold.

BACKGROUND: The role of myocardial tissue mass on ventricular defibrillation threshold (DFT) is unclear. We hypothesized that changes in tissue mass modulate DFT by changing ventricular fibrillation (VF) wavefront regularity (entropy). METHODS AND RESULTS: The right ventricles (RV) of seven farm pigs were isolated, superfused and perfused through the right coronary artery with oxygenated Tyrode's solution at 37 degrees C. The epicardial surface was stained with the voltage sensitive dye, di-4-ANEPPS, and activation wavefront numbers (AWN) during VF were determined from the optical maps using a CCD camera (96 x 96 pixels over a 3.5 x 3.5 cm area). The RV mass was progressively reduced by sequential cutting of 1 to 2 g of tissue (approximately 12 cuts in total) distal to the perfusion site. After each cut, VF was reinduced, optical maps obtained, and the 50% probability of successful DFT(50) determined using an up-down algorithm. After each cut, the approximate entropy (ApEn) was also computed using 5 seconds of VF data obtained with a bipolar electrode and a pseudo-electrocardiogram. Tissue mass reduction of up to one third of the RV mass (ie, from 48.4 +/- 4.25 g to 34 +/- 4.7 g) caused little or no change in the DFT, ApEn or AWN. However, further progressive reduction of the RV mass near the critical mass of VF resulted in a significant (P < 0.05) progressive decrease in all three measured parameters. DFT energy was reduced by 27% (1.47 +/- 0.34 J vs. 1.02 +/- 0.14 J). There was a significant (P < 0.01) correlation between the DFT and ApEn, which significantly further increased (P < 0.001) near the critical mass. In a separate series of 6 isolated RVs, the ApEn correlated well with the Kolmogorov-Sinai (K-S) entropy, the standard method of calculating entropy. CONCLUSION: Tissue mass reduction significantly reduces DFT when the mass reduction increases VF wavefront regularity.