Faculty Bibliography

OBJECTIVES: To investigate the effect of epicardial fat on surgical atrial fibrillation ablation performance using an in vitro model. Two tissue models were employed to investigate standard penetration and maximal lesion depth performance of bipolar radiofrequency (RF), microwave, and laser energy sources. METHODS: Ventricular veal tissue was utilized in various thicknesses (3 mm, 5 mm, 7 mm, 15 mm). Epicardial fat was modeled by layering porcine fat (1 mm, 2 mm and 4 mm) on moistened tissue. In each group, 8 to 10 lesions were created. Post ablation, tissue samples were sectioned and ablation depth of each myocardial section measured using 1% tetrazolium tetrachloride dye solution. RESULTS: The laser energy source produced nearly 100% transmural lesions in almost all study groups irrespective of myocardium thickness and fat thickness. The microwave device maintained transmurality in all 3-mm and most 5-mm myocardium trials but fell to near zero with all 7-mm myocardium trials. The bipolar RF maintained transmurality only when no fat was applied. In the maximal lesion depth models, the laser was capable of producing lesions >8 mm with no fat and >6 mm with either 2 mm or 4 mm of fat present. The microwave produced lesions in the no fat (>6 mm) and 2-mm (>4 mm) fat group. The bipolar RF produced 83% transmurality with no fat and zero percent transmurality with 2 mm of fat present. CONCLUSIONS: Epicardial fat can severely limit transmurality in energy sources that utilize conductive heating. Laser energy was uniformly superior at producing both transmural and deep lesions irrespective of the presence of fat.

Surgical atrial fibrillation ablation (SAFA) has not achieved the efficacy of Cox's original maze procedure, although technical improvements continue to be made. It is possible that biologic factors determine SAFA success. Therefore we examined how patient-specific characteristics affected SAFA success in 353 atrial fibrillation (AF) patients who underwent SAFA at a single institution. Among these, 257 (72.8%) had continuous AF and 96 (27.2%) had intermittent AF. For 297 patients (84.1%) postoperative follow-up was > 3 months. We compared SAFA success in patients whose procedure involved only pulmonary vein isolation with those whose procedure involved extensive lesion sets. Multivariate analysis included AF duration, left atrial size, preoperative atrial flutter, concomitant procedures, lesion sets, and energy source. Early SAFA success was classified as freedom from AF between postoperative months 3 and 6, and intermediate success between postoperative months 6 and 12. Receiver-operating characteristic (ROC) curves and stratum-specific likelihood ratios (SSLR) were generated to compare intermediate failure by left atrial size (LAS) thresholds. SAFA was more successful in the intermittent than the continuous AF group (n = 66, 86% vs n = 165, 71%; P = .014). When pulmonary vein isolation was compared only to more extensive lesion sets, there was no difference in success in the intermittent (34, 91% vs 32, 81%; P = .24) or continuous groups (67, 73% vs. 98, 69%; P = .603). Success for intermittent AF patients was not correlated with variables considered; in continuous AF patients, predictors included presence of concomitant mitral valve repair/replacement (P = .075), decreasing LAS (P = .025) and absence of preoperative atrial flutter (P = .001). In the continuous AF group, ROC curves and corresponding areas under the curve (AUC) were 0.60 (0.50-0.71) for failure at 6 months to 1 year. SSLR analysis generated 2 strata for LAS: < 8 cm with SSLR = 0.87 (0.74-1.0) and < or = 8 cm SSLR = 2.98 (1.07-8.3). In patients with intermittent AF, SAFA achieved acceptable results regardless of tested preoperative and intraoperative variables. In continuous AF, patient-specific characteristics affected success more than intraoperative variables. Failure was more than 3-fold greater in continuous AF patients with an LAS < or = 8 cm. In both patient types, more extensive lesion sets were not shown to improve outcomes. Future improvements in SAFA may depend on pharmacologic and/or surgical substrate modification

Recent years have seen many developments in the field of alternative energy sources for arrhythmia surgery. The impetus behind these advances is to replace the traditional, "cut-and-sew" Cox maze III procedure with lesion sets that are simpler, shorter, and safer but just as effective. There is demand for technology to make continuous, linear, transmural ablations reliably with a versatile energy source via an epicardial approach. This would make minimally invasive endoscopic surgical ablation of atrial fibrillation (AF) without cardiopulmonary bypass and with a closed chest feasible. These advances would shorten cardio-pulmonary bypass and improve outcomes in patients having surgical ablation and concomitant cardiac surgery. This review summarizes the technology behind alternative energy sources used to treat AF. Alternative energy sources include hypothermic sources (cryoablation) and hyperthermic sources (radiofrequency, microwave, laser, ultrasound). For each source, the biophysical background, mode of tissue injury, factors affecting lesion size, and advantages and complications are discussed.

Convenience sampling methods predominate in recruiting for laboratory-based studies within clinical and family psychology. The authors used random digit dialing (RDD) to determine whether they could feasibly recruit generalizable samples for 2 studies (a parenting study and an intimate partner violence study). RDD screen response rate was 42-45%; demographics matched those in the 2000 U.S. Census, with small- to medium-sized differences on race, age, and income variables. RDD respondents who qualified for, but did not participate in, the laboratory study of parents showed small differences on income, couple conflicts, and corporal punishment. Time and cost are detailed, suggesting that RDD may be a feasible, effective method by which to recruit more generalizable samples for in-laboratory studies of family violence when those studies have sufficient resources.

BACKGROUND: The Maze III procedure is an effective surgical treatment for atrial fibrillation (AF). However, it is not widely applied due to its complexity, increased operative times, and the risk of bleeding. Various energy sources have been introduced to simplify the traditional "cut and sew" approach. METHODS: This study involves patients undergoing surgical atrial fibrillation ablation (SAFA) at a single institution from 1999 to 2005. Type of concomitant procedures, preoperative clinical characteristics, and chronicity of AF were evaluated in overall patient population. Parameters including surgical approach, lesion pattern, and energy source used were collected intraoperatively. Clinical outcomes examined were postoperative rhythm success, stroke, early mortality, and long-term survival. RESULTS: Three hundred thirty-nine patients were identified. Three hundred twenty-eight (96.8%) patients had associated cardiac disease and underwent concomitant procedures; 75.8% of patients had persistent AF. Energy sources used were microwave (49.8%), radiofrequency (42.2%), and laser (8.0%). In 41.9% of cases a pulmonary vein encircling lesion was the only lesion created. Combination lesion sets were performed in the remaining cases. Rhythm success rates at 3, 6, 12, and 24 months were 74.1%, 68.2%, 74.5%, and 71.1%, respectively. Patients who underwent surgical removal of left atrial appendage by means of stapling or simple excision had no early postoperative stroke. Early mortality was 4.9%. Postoperative survival rates at 1, 3, and 5 years were 89.6%, 83.1%, and 78.0%. CONCLUSIONS: Surgical ablation of atrial fibrillation is a safe and effective procedure in restoring sinus rhythm with excellent postoperative survival rates. Further advancements in the field will eventually result in minimally invasive procedures with higher success rates.

The development of lesser invasive transcatheter techniques for aortic valve replacement (AVR) to treat high surgical risk patients with severe aortic stenosis (AS) has engendered controversy among traditional cardiovascular therapists. Presently, there are two catheter-based treatment systems (the Cribier-Edwards Aortic Bioprosthesis and the CoreValve Revalving System) utilizing either a balloon-expandable or a self-expanding stent (or cage) platform which unfolds a pericardial tissue valve within the displaced diseased aortic valve. After ex vivo durability testing and animal studies, several clinical registries with these transcatheter AVR systems in almost 300 patients worldwide have demonstrated the following: (1) good acute hemodynamic performance with reduction in mean aortic valve gradients to <10 mm Hg; (2) frequent para-valvular regurgitation, which has improved with self-expanding devices and the use of larger (26 mm) valve sizes; (3) acceptable periprocedural (30-day) mortality (<10%) with the newest generation devices and improved operator techniques. Enlightened interdisciplinary treatment teams incorporating surgeons, interventionalists, and medical therapists as well as rigorously conducted randomized clinical trials will be required to determine if these innovative transcatheter AVR approaches will represent a viable therapy for high-risk patients with severe AS in the future.

BACKGROUND: Due to its complexity and risk of bleeding, the Maze III procedure has been largely replaced by surgical ablation for atrial fibrillation (AF) using alternative energy sources. Radiofrequency (RF) and microwave (MW) are the most commonly used energy forms. In this study, we sought to compare these energy modalities in terms of clinical outcomes. METHODS: Two hundred five patients underwent surgical ablation of AF, from October 1999 to May 2004 at our institution via an endocardial approach. Patients were categorized into 2 groups: RF and MW. Baseline characteristics, operative details, and clinical outcomes were compared between the 2 groups. Rhythm success was defined as freedom from AF and atrial flutter as determined by postoperative electrocardiograms. RESULTS: One hundred twenty patients (58.5%) were ablated using RF, whereas 85 (41.5%) were ablated with MW. Most of the patients had persistent AF in both the RF and MW groups (85.7% versus 80.0%, respectively; P = .363). Intraoperative left atrial size was 6.4 +/- 1.7 cm for the RF group and 6.4 +/- 1.7 cm for the MW group (P = .820). Postoperative rhythm success at 6 and 12 months was 72.4% versus 71.4% (P +/- .611) and 75.0% versus 66.7% (P = .909) for the RF and MW groups, respectively. Hospital length of stay was comparable for both groups (15.4 +/- 14.0 versus 13.3 +/- 13.9 days; P = .307). Postoperative survival at 6 months, 1 year, and 3 years was 90.4%, 89.5%, and 86.1% for RF patients compared to 87.9%, 86.5%, and 84.4% for MW patients, respectively (log rank P = .490). CONCLUSIONS: RF and MW energy forms yield comparable postoperative rhythm success, hospital length of stay, and postoperative survival. Both sources are rapid, safe, and effective alternatives to "cut and sew" techniques for surgical treatment of AF.

We describe epicardial ablation using a new device that utilizes 980 nm wavelength laser energy. The device can be used in both open and minimally invasive approaches and should make ablation therapy safe, effective, and easy to use.

As less complex modifications of the Maze procedure have been developed, a number of energy sources have been introduced to facilitate the creation of electrically isolating lesions within the atria. These include cryoablation, radiofrequency, microwave, laser, and focused ultrasound. Although each of these sources works slightly differently, the goal of all thermal sources is to heat tissue to a temperature (50 degrees C) above which irreversible electrical isolation occurs. These sources have been utilized both endocardially in arrested heart procedures as well as epicardially in the beating heart setting. There are several obstacles to the use of these sources epicardially, mostly related to the heat sink effect of endocardial blood. Several recent modifications have been introduced that will hopefully increase the efficacy of these sources in beating heart applications.