Effect of shock polarity on the efficacy of transthoracic atrial defibrillation.

BACKGROUND: The energy requirement for internal ventricular defibrillation is reduced by reversal of shock polarity. The influence of shock polarity on the efficacy of transthoracic atrial defibrillation is unknown. METHODS: This prospective, randomized study enrolled 110 consecutive patients who were referred for elective cardioversion of persistent atrial fibrillation (AF). The electrodes were placed in the anteroposterior position. The patients were randomized to receive either standard (anterior pad = cathode) or reversed polarity (anterior pad = anode) shocks with a damped sinusoidal monophasic waveform. A step-up protocol was used to estimate the cardioversion threshold. The initial shock energy was 50 J, with subsequent increments to 100, 200, 300, and 360 J in the event of cardioversion failure. RESULTS: Sixty-four percent of the patient population were men, with a mean age of 66 +/- 13 years and a mean duration of AF of 242 +/- 556 days. The overall success rates of cardioversion were 84% for standard polarity and 78% for reversed polarity (P not significant). Among the patients who were successfully cardioverted, the mean atrial defibrillation threshold was 198 +/- 103 J for standard polarity and 212 +/- 107 J for reversed polarity (P not significant). CONCLUSIONS: Reversal of shock polarity does not improve transthoracic cardioversion efficacy with a standard damped sinusoidal monophasic waveform. Alternate strategies should be considered for patients who fail external cardioversion, such as adjunctive pharmacologic treatment, use of a biphasic shock waveform, or internal cardioversion.

Cardiac thrombosis as a manifestation of Behçet syndrome.

Herein, we report 3 cases of Behçet syndrome that were accompanied by intracardiac thrombus. The 1st patient was a 30-year-old man who presented with dyspnea; a right atrial thrombus was identified upon transthoracic echocardiography. The 2nd patient was a 52-year-old man who was admitted for dyspnea; transthoracic echocardiography revealed an echogenic mass in the right ventricle. The 3rd patient was a 23-year-old man who was hospitalized for hemoptysis; the diagnosis of pulmonary embolism was made, and right ventricular thrombosis was found.Because these patients had no hemodynamic compromise, medical management consisting of immunosuppressive and anticoagulative therapy was adopted. This treatment resulted in complete dissolution of the thrombi.

Management of cardiac involvement in neuromuscular diseases: review.

Neuromuscular Diseases are a heterogeneous molecular, clinical and prognosis group. Progress has been achieved in the understanding and classification of these diseases.Cardiac involvement in neuromuscular diseases namely conduction disorders, ventricular dilatation and dilated cardiomyopathy with its impact on prognosis, is often dissociated from the peripheral myopathy. Therefore, close surveillance is mandatory in the affected patients. In this context, preventive therapy (beta-blockers and angiotensin converting enzyme inhibitors) has been recently recommended in the most common Neuromuscular Diseases, Duchenne Muscular Dystrophy and Myotonic Dystrophy.

Lack of benefit of an active pectoral pulse generator on atrial defibrillation thresholds.

INTRODUCTION: Atrial defibrillation can be achieved with standard implantable cardioverter defibrillator leads, which has led to the development of combined atrial and ventricular devices. For ventricular defibrillation, use of an active pectoral electrode (active can) in the shocking pathway markedly reduces defibrillation thresholds (DFTs). However, the effect of an active pectoral can on atrial defibrillation is unknown. METHODS AND RESULTS: This study was a prospective, randomized, paired comparison of two shock configurations on atrial DFTs in 33 patients. The lead system evaluated was a dual-coil transvenous defibrillation lead with a left pectoral pulse generator emulator. Shocks were delivered either between the right ventricular coil and proximal atrial coil (lead) or between the right ventricular coil and an active can in common with the atrial coil (active can). Delivered energy at DFT was 4.2 +/- 4.1 J in the lead configuration and 5.0 +/- 3.7 J in the active can configuration (P = NS). Peak current was 32% higher with an active can (P < 0.01), whereas shock impedance was 18% lower (P < 0.001). Moreover, a low threshold (< or = 3 J) was observed in 61% of subjects in the lead configuration but in only 36% in the active can configuration (P < 0.05). There were no clinical predictors of the atrial DFT. CONCLUSION: These results indicate that low atrial DFTs can be achieved using a transvenous ventricular defibrillation lead. Because no benefit was observed with the use of an active pectoral electrode for atrial defibrillation, programmable shock vectors may be useful for dual-chamber implantable cardioverter defibrillators.