Idioventricular rhythm

Abstract: Background In some patients with atrial fibrillation, the ventricular rate may be difficult to control with medications. We evaluated a radiofrequency catheter technique to modify atrioventricular conduction in atrial fibrillation in order to control the ventricular rate without creating pathologic atrioventricular block. Methods We studied 19 consecutive patients with atrial fibrillation and uncontrolled ventricular rates refractory to drug therapy. They had had atrial fibrillation for a mean (±SD) of 5.5 ±4.9 years, had had 4.9 ±0.9 unsuccessful drug trials, and were 62 ±15 years old. Before the procedure, the maximal ventricular rate during exercise was 180 ±39 beats per minute. A total of 11 ±5 radiofrequency-energy applications were delivered to the posterior septal or midseptal right atrium, near the ostium of the coronary sinus. Results Successful control of the ventricular rate without pathologic atrioventricular block was achieved in 14 of the 19 patients (74 percent). Persistent third-degree atr...

Abstract: We compared the effects of initial electrical shocks using 175 and 320 J (joules) in 249 patients with ventricular fibrillation. Survival was unrelated to the energy level used for defibrillation. Reversion to an organized rhythm occurred in a similar proportion of both treatment groups after one or two shocks. The rhythm identified after the first shock was related to outcome (the survival rate was 42 per cent in patients with supraventricular rhythm, 30 per cent in persistent ventricular fibrillation, 26 per cent in idioventricular rhythm, and 14 per cent in asystole; P less than 0.02). Fibrillation recurred in 68 per cent of patients who had been initially defibrillated to an organized rhythm. Repeated shocks at the higher energy level resulted in a higher incidence of atrioventricular block after defibrillation (24 per cent of patients receiving 320 J and 9 per cent of those receiving shocks of lower energy; P less than 0.005). Patients who survived required fewer shocks than patients who later died in the hospital (2.6 shocks as compared with 3.6; P less than 0.005). We conclude that initial defibrillatory shocks using 175 J are as safe and effective as shocks of nearly twice that energy level.

Abstract: To determine the frequency and severity of cardiac arrhythmias in intracranial subarachnoid hemorrhage, 120 nonselected patients were prospectively studied by 24-hour Holter monitoring Arrhythmias were found in 96 of 107 patients (90%) with adequate Holter recording: ventricular premature complexes in 49, nonsustained ventricular tachycardia in 5, supraventricular premature complexes in 29, paroxysmal supraventricular tachycardia or atrial fibrillation in 9, sinoatrial block and arrest in 29, second-degree atrioventricular block in 1, atrioventricular dissociation in 4 and idioventricular rhythm in 2 Life-threatening ventricular arrhythmias (torsades de pointes-type ventricular tachycardia) occurred in 4 patients, degenerating into either ventricular flutter or fibrillation in 2 ST-segment changes suggestive of acute transitory myocardial ischemia were found in 8 patients (15 mm or more of ST depression in 7 patients and 15 mm or more of ST elevation in 1 patient) The frequency and severity of arrhythmias were significantly higher in patients studied within 48 hours of subarachnoid hemorrhage; serious ventricular arrhythmias were associated with QTc prolongation more than 550 ms and with hypokalemia less than 35 mEq/liter No correlation was found between age, clinical condition, site and extent of subarachnoid hemorrhage and either the occurrence or severity of arrhythmias The results of our study indicate an extremely high incidence of arrhythmias, sometimes serious, in subarachnoid hemorrhage, especially in the first 48 hours after hemorrhage Continuous electrocardiographic monitoring is therefore mandatory

Abstract: This investigation was performed to evaluate the feasibility of detecting repolarization alternans with the heart rate elevated with a bicycle exercise protocol. Sensitive spectral signal-processing techniques are able to detect beat-to-beat alternation of the amplitude of the T wave, which is not visible on standard electrocardiogram. Previous animal and human investigations using atrial or ventricular pacing have demonstrated that T-wave alternans is a marker of vulnerability to ventricular arrhythmias. Using a spectral analysis technique incorporating noise reduction signal-processing software, we evaluated electrical alternans at rest and with the heart rate elevated during a bicycle exercise protocol. In this study we defined optimal criteria for electrical alternans to separate patients from those without inducible arrhythmias. Alternans and signal-averaged electrocardiographic results were compared with the results of vulnerability to ventricular arrhythmias as defined by induction of sustained ventricular tachycardia or fibrillation at electrophysiologic evaluation. In 27 patients alternans recorded at rest and with exercise had a sensitivity of 89%, specificity of 75%, and overall clinical accuracy of 80% (p <0.003). In this patient population the signal-averaged electrocardiogram was not a significant predictor of arrhythmia vulnerability. This is the first study to report that repolarization alternans can be detected with heart rate elevated with a bicycle exercise protocol. Alternans measured using this technique is an accurate predictor of arrhythmia inducibility.