Defibrillator shocks > 9 J delivered during the baseline rhythm or during defibrillation energy requirement testing result in a 10% to 15% reduction in cardiac index, whereas smaller energy shocks do not affect cardiac hemodynamics. The duration and extent of the adverse effect are proportional to the shock strength. Shock strength, and not ventricular fibrillation, appears to be most responsible for this effect. Therefore, the detrimental hemodynamic effects of high-energy shocks may be avoided when low-energy defibrillation is used.

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Background-High-intensity focused ultrasound has been applied to internal organs from outside the body to ablate tissue.No published study has assessed the feasibility of ablating cardiac tissue within the beating heart by use of this type of therapeutic ultrasound. The purpose of this study was to determine whether high-intensity focused ultrasound can be used to ablate the atrioventricular (AV) junction within the beating heart. Methods and Results-Ten dogs were anesthetized and underwent a thoracotomy. The heart was covered with a polyvinyl chloride membrane. The thorax above the membrane was perfused with degassed water, which functioned as a coupling medium for the ultrasound. A 7.0-MHz diagnostic ultrasound probe was affixed to a spherically focused 1.4-MHz high-intensity focused ultrasound transducer with a 1.1ϫ8.3-mm focal zone 63.5 mm from the ablation transducer. The diagnostic ultrasound probe was calibrated such that the location of the focal zone of the ablation transducer was identifiable on the 2-dimensional ultrasound image. Target sites were identified with the diagnostic ultrasound. The maximum ultrasound intensity for ablation (2.8 kW/cm 2 ) was delivered to the AV junction only during electrical diastole and for a total of 30 seconds. Complete AV block was achieved in each of the 10 dogs with 6.5Ϯ5.6 (range, 3 to 21) 30-second applications of therapeutic ultrasound. Gross inspection showed that the mean lesion volume was 124Ϯ143 mm 3 , with a depth of 6.7Ϯ3.6 mm, a length of 5.7Ϯ2.5 mm, and a width of 4.7Ϯ1.8 mm. Four hours after the dogs were killed, histopathological study demonstrated a well-demarcated area of necrosis and early inflammation. Conclusions-High-intensity focused ultrasound produces well-demarcated lesions and appears to be a feasible energy source to create complete AV block within the beating heart without damaging the overlying or underlying cardiac tissue. This energy source may allow for a noninvasive approach to ablation of cardiac arrhythmias. (Circulation. 1999;100:203-208.)

Background Bepridil hydrochloride (Bpd) has attracted attention as an effective drug for atrial fibrillation (AF) and atrial flutter (AFL). However, serious adverse effects, including torsade de pointes (Tdp), have been reported. Methods and Results Adverse effects of Bpd requiring discontinuation of treatment were evaluated. Bpd was administered to 459 patients (361 males, 63±12 years old) comprising 378 AF and 81 AFL cases. Mean left ventricular ejection fraction and atrial dimension (LAD) were 66±11% and 40±6 mm, respectively. Adverse effects were observed in 19 patients (4%) during an average follow-up of 20 months. There was marked QT prolongation greater than 0.55 s in 13 patients, bradycardia less than 40 beats/min in 6 patients, dizziness and general fatigue in 1 patient each. In 4 of 13 patients with QT prolongation, Tdp occurred. The major triggering factors of Tdp were hypokalemia and sudden decrease in heart rate. There were no differences in the clinical backgrounds of the patients with and without Tdp other than LAD and age, which were larger and older in the patients with Tdp. Conclusion Careful observation of serum potassium concentration and the ECG should always be done during Bpd administration, particularly in elderly patients. (Circ J 2006; 70: 662 -666)

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