Laser ablation of the pulmonary veins by using a fiberoptic balloon catheter: implications for treatment of paroxysmal atrial fibrillation.

BACKGROUND AND OBJECTIVE: Focal sources of paroxysmal atrial fibrillation may be treatable by electrical isolation of the pulmonary veins from the left atrium. A new fiberoptic balloon catheter was tested as an alternative to radiofrequency catheter ablation for creation of circumferential thermal lesions at the pulmonary vein orifice. STUDY DESIGN/MATERIALS AND METHODS: In vitro and in vivo experiments were conducted in canine hearts to demonstrate efficacy and optimize ablation dosimetry. Continuous-wave, 1.06-microm, Nd:YAG laser radiation was delivered radially through diffusing optical fiber tips enclosed in a balloon catheter. During in vivo studies, the catheter was placed at the pulmonary vein orifice through a left atrial appendage sheath under X-ray fluoroscopic guidance during an open-chest procedure. Additionally, circumferential lesions in the left atrial appendage were correlated with epicardial electrograms demonstrating elimination of electrical activity. RESULTS: The pulmonary veins were successfully ablated by using laser powers of 30--50 W and irradiation times of 60--90 seconds. Transmural, continuous, and circumferential lesions were produced in the pulmonary veins in a single application without evidence of tissue vaporization or endothelial disruption. CONCLUSION: Laser ablation by using a fiberoptic balloon catheter may represent a promising alternative to radiofrequency catheter ablation for electrical isolation of the pulmonary veins from the left atrium during treatment of paroxysmal atrial fibrillation. Further development and testing of the fiberoptic catheter is warranted for possible clinical studies.

Resuscitation after prolonged ventricular fibrillation with use of monophasic and biphasic waveform pulses for external defibrillation.

BACKGROUND: Survival after prolonged ventricular fibrillation (VF) appears severely limited by 2 major factors: (1) low defibrillation success rates and (2) persistent post-countershock myocardial dysfunction. Biphasic (BP) waveforms may prove capable of favorably modifying these limitations. However, they have not been rigorously tested against monophasic (MP) waveforms in clinical models of external defibrillation, particularly where rescue from prolonged VF is the general rule. METHODS AND RESULTS: We randomized 26 dogs to external countershocks with either MP or BP waveforms. Hemodynamics were assessed after shocks applied during sinus rhythm, after brief VF (>10 seconds), and after resuscitation from prolonged VF (>10 minutes). Short-term differences in percent change in left ventricular +dP/dt(max) (MP -16+/-28%, BP +9.1+/-24%; P=0.03) and left ventricular -dP/dt(max) (MP -37+/-26%, BP -18+/-20%; P=0.05) were present after rescue from brief VF, with BP animals exhibiting less countershock-induced dysfunction. After prolonged VF, the BP group had lower mean defibrillation thresholds (107+/-57 versus 172+/-88 J for MP, P=0.04) and significantly shorter resuscitation times (397+/-73.7 versus 488+/-74.3 seconds for MP, P=0.03). CONCLUSIONS: External defibrillation is more efficacious with BP countershocks than with MP countershocks. The lower defibrillation thresholds and shorter resuscitation times associated with BP waveform defibrillation may improve survival after prolonged VF arrest.

Endogenous ethanol production and hepatic disease following jejunoileal bypass for morbid obesity.

In this study, we sought to determine whether or not elevated levels of ethanol were present in the systemic circulation, resulting from endogenous ethanol production, which might contribute to the hepatic damage following jejunoileal bypass for morbid obesity. Venous serum samples for assay of ethanol by gas-liquid chromatography were obtained in 8 normal subjects, 9 obese patients prior to surgery, 20 obese patients 2 weeks to 40 months after jejunoileal bypass, and in 2 dogs before and after jejunoileal bypass. Ethanol was detected after jejunoileal bypass in only 7 of the 20 patients and in the 2 dogs. Serum ethanol concentrations ranged from 0.15 to 4.12 mg/100 ml with a mean of 1.18 +/- 1.59 (SD)( mg/100 ml in the 7 patients and ranged from 0.20 to 2.23 mg/100 ml in the dogs. Incubation of the contents of the bypassed intestine of a dog with dextrose resulted in the production of significant amounts of ethanol. However, there was no correlation between the presence of ethanol in the serum and liver histology, when liver biopsy was obtained, postoperatively. Since ethanol was detected in the serum in only small concentrations and in only one-third of the patients, it is unlikely that ethanol production by bacteria in the intestine is of significance in the pathogenesis of liver disease following jejunoileal bypass.