Laser energy source in surgical atrial fibrillation ablation: preclinical experience.

PURPOSE: The purpose of this study was to evaluate diffusing tip laser energy in surgical atrial fibrillation ablation using a canine model. This is the first report to describe the pathological and histological findings using a laser energy source. DESCRIPTION: The surgical atrial fibrillation ablation procedure was performed through a left atriotomy; the pulmonary veins were encircled in 16 dogs using a diode laser (980 nm) with a diffusing tip that permits linear ablation perpendicular to the fiber direction. Lesion durations were 45 seconds with a power density of 3.8 or 4.5 W/cm. Six animals were allowed to survive 4 hours after the procedure, with the remainder sacrificed at 1 week (n = 1), 4 weeks (n = 3), and 6 weeks (n = 6). Electrophysiologic effectiveness was judged using unipolar or bipolar pacing from the pulmonary veins after attempting isolation. Hearts were harvested for histologic examination using standard trichrome staining. EVALUATION: All animals tolerated the procedure. The animals required an average of 5.6 +/- 0.82 lesions to complete the procedure. All animals had confirmed isolation of the pulmonary veins as judged by unipolar or bipolar pacing, and this isolation persisted in those animals that were allowed to survive. Pathology revealed all lesions to be transmural with an average tissue thickness of 3.62 +/- 1.50 mm (range, 0.95 mm to 7.06 mm). CONCLUSIONS: Diffusing tip laser technology reproducibly makes rapid, transmural, and electrophysiologically effective atrial lesions.

Does a pre-left ventricular assist device screening score predict long-term transplantation success? A 2-center analysis.

BACKGROUND: A risk factor summation score was previously validated to successfully predict survival after insertion of a left ventricular assist device (LVAD). We investigated whether this scoring system also predicts clinical outcomes after eventual heart transplantation in LVAD recipients. METHODS: A retrospective review was performed on 153 consecutive patients who received an LVAD as a bridge to transplantation at 2 large-volume centers from 1996 to 2003. The scoring system was used to designate low- and high-scoring groups. RESULTS: Thirty-day mortality and 5-year survival after transplantation were equivalent between groups (4.46% versus 7.32% and 76% versus 70%, respectively). No difference was seen in length of posttransplantation ventilator dependence (2.83 +/- 0.49 versus 3.3 +/- 0.72 days) or intensive care unit monitoring (6.38 +/- 0.77 versus 6.97 +/- 1.1 days). However, low-scoring patients had a significantly decreased duration of inotrope support (5.57 +/- 0.45 versus 7.74 +/- 1.0 days, P = .035). CONCLUSION: A risk factor summation score may predict which LVAD patients will require prolonged inotropic support following heart transplantation. However, survival in high-risk (elevated score) LVAD patients following heart transplantation is comparable to low-risk groups, favoring the continued practice of LVAD implantation as a bridge to transplantation even in high-risk patients.

Off-pump epicardial atrial fibrillation surgery utilizing a novel bipolar radiofrequency system.

BACKGROUND: Over the past several years, pulmonary vein isolation for the treatment of atrial fibrillation has gained significant popularity. This study was undertaken to evaluate a novel radiofrequency (RF)-enabled clamp system designed to create transmural lesions epicardially on the beating heart using bipolar RF. METHODS: A set of differently shaped clamps modified to deliver bipolar RF energy were used to create a series of lesions in a beating heart canine model. The pulmonary veins and atrial appendages of 6 dogs were electrically isolated using bipolar RF energy. The right and left atrial appendages served as controls for the right and left pulmonary veins, respectively. Temperature-controlled RF energy was delivered to maintain a tissue temperature of 80 degrees C for 15 seconds. Electrical isolation was assessed acutely and after 4 weeks by a bipolar pacing protocol. RESULTS: A total of 24 circumferential lesions were created. By pacing analysis, 100% (24/24) of these lesions were electrically isolated acutely and 95% (19/20) were still isolated 4 weeks later. At 4 weeks, 92% (22/24) of lesions were transmural by histologic analysis, and 96% (23/24) demonstrated endocardial continuity. One animal experienced a fatal cardiac arrhythmia during initiation of the post-survival procedure, prior to electrophysiologic evaluation, accounting for the reduced number of potential electrically isolated lesions. CONCLUSION: Bipolar RF ablation utilizing a novel bipolar RF clamp device results in electrical isolation and histologic transmurality in an off-pump epicardial model.

Computed tomographic scan of the chest underestimates the number of metastatic lesions in osteosarcoma.

PURPOSE: Survival in osteosarcoma correlates with complete resection of primary and metastatic disease. The feasibility of complete pulmonary metastasectomy using thoracoscopy has been raised. Because palpation is not possible, minimally invasive techniques require preoperative radiological enumeration and localization of metastases not presenting at the lung surface. We hypothesized that computed tomographic (CT) scanning underestimated the number of pulmonary metastases in these patients. METHODS: Institutional review board approval was obtained. We determined the association between the number of lesions identified by CT scanning and the number of metastases found at thoracotomies for metastatic osteosarcoma from May 1996 to October 2004. Correlations between CT findings and pathology results were computed using the Kendall tau-b correlation coefficient. Depth, in millimeters, from the pleural surface was measured for those lesions seen on CT scan. RESULTS: We analyzed 54 consecutive thoracotomies performed in 28 patients for whom complete imaging was available. Computed tomographic scanning was performed a median of 20 days before thoracotomy (range, 1-85 days). Correlation between the number of lesions identified by CT and the number of metastases resected at surgery was poor, with a Kendall tau-b correlation coefficient of 0.45 (P < .001). In 19 (35%) of 54 thoracotomies, CT scanning underestimated the number of pathologically proven, viable and nonviable metastases found by the surgeon. Accounting for viable metastases only, correlation between the number of lesions identified by CT and the number of metastases resected at surgery was 0.50 (P < .001), and CT scanning underestimated the number of viable metastases present in 14 (26%) of 54 thoracotomies. Many lesions (32%) were pleural-based, but nearly half (47%) were 5 mm or deeper from the pleural surface of the lung. CONCLUSIONS: Even in the era of modern CT scanning, only a very rough correlation exists between CT findings and the number of lesions identified at thoracotomy. In more than one third of thoracotomies in our series, metastases would have been missed by any tactic besides manual palpation of the lung during open thoracotomy. Minimal access procedures should not be the approach of choice if the goal is resection of all pulmonary metastases in osteosarcoma.

Edge-to-edge mitral valve repair: the Columbia Presbyterian experience.

BACKGROUND: The edge-to-edge mitral valve repair, first described by Alfieri in 1995 treats mitral regurgitation when standard reparative techniques are difficult, unlikely to succeed, or have failed. This study examines one institution's medium-term experience with this procedure. METHODS: This study involved patients undergoing edge-to-edge mitral valve repair at a single institution from 1997 to 2003. Preoperative and postoperative echocardiograms were compared. Postoperative morbidity was examined including need for reoperation and long-term medical management. Thirty-day survival and long-term actuarial survival were also determined. RESULTS: Seventy-one patients comprised this study. Mitral regurgitation on echocardiogram went from 3.43 +/- 0.86 to 0.39 +/- 0.61 (p < 0.001) following repair. Thirty-day mortality was 3 of 71 (4.2%) patients. Actuarial survivals at 24 and 60 months were 84.5% and 58.3%, respectively; adjusted excluding noncardiac death they were 89.5% and 82.3%, respectively. Forty (56.3%) patients had concomitant ring placement and experienced similar survival to those repaired with the bow-tie stitch alone. Home telephone follow-up was conducted, and current medical therapy was determined on 51 patients; 59% were on a beta-blocker, 31% were on an angiotensin-converting enzyme (ACE) inhibitor, 27% were on a diuretic, and 22% were on digoxin. All were New York Heart Association (NYHA) class I or II. Three patients (4.2%) underwent mitral valve reoperation after a mean of 299 +/- 429 days. In no case did the bow-tie suture rupture. CONCLUSIONS: Edge-to-edge mitral valve repair is a valuable tool in the armamentarium available to treat complex cases of mitral insufficiency or as an adjunct to standard repair techniques that fail to achieve an acceptable result.

Insertion of a left ventricular assist device in patients without thorough transplant evaluations: a worthwhile risk?

OBJECTIVES: Patients in acute cardiogenic shock may require placement of left ventricular assist devices before undergoing standard pretransplant evaluations. This practice raises ethical and logistic concerns and has led us to investigate the short- and long-term outcomes for this patient population. Methods and results We examined our adult bridge-to-transplant left ventricular assist device population over a 6-year period to characterize those patients with acute cardiogenic shock who received left ventricular assist devices on an emergency basis (ie, placement of a device within 24 hours of being listed for cardiac transplantation). Outcomes before and after transplant were compared with those of candidates with nonemergency evaluations by Kaplan-Meier survival curves and the Fisher exact test where appropriate. Of the 115 patients who required left ventricular assist device support, 73 (63%) patients required emergency placement; 70% of these patients survived to transplant compared with 83% of those with nonurgent device implantation (not statistically significant). Posttransplant survival curves were similar for patients with emergency device placement and those with nonurgent placement (not statistically significant). Twenty-two patients having emergency device placement did not undergo heart transplantation because of multisystem organ failure (14), device support withdrawal from irreversible neurologic injury (4), device or technical problems (2), and left ventricular assist device explant due to myocardial recovery (2). CONCLUSIONS: At our institution, the majority of left ventricular assist devices are placed on an emergency basis. Few of these patients require discontinuation of device support due to undetected conditions during abbreviated preoperative evaluation. Survival before and after transplant is comparable with those of patients who undergo nonurgent left ventricular assist device placement or medical therapy.