In patients with CHF, LV dysfunction, and chronic AF, RVOT and dual-site RV pacing shorten QRS duration but after 3 months do not consistently improve QOL or other clinical outcomes compared with RVA pacing.
Invasive electrophysiologic testing and noninvasive testing were compared as methods for identifying patients with Wolff-Parkinson-White syndrome at risk for sudden death. Sixty-seven patients were studied, including nine with a history of ventricular fibrillation. Electrophysiologic testing, using the shortest interval between consecutive pre-excited beats (shortest RR interval) less than or equal to 250 ms during induced atrial fibrillation to define risk, identified seven of nine patients with previous ventricular fibrillation. The sensitivity increased to 87.5% if one patient with prior amiodarone therapy was excluded. Electrophysiologic testing had a specificity of 48.3% and a low predictive accuracy (18.9%) when using the shortest RR interval (less than or equal to 250 ms) to identify the risk for sudden death. Continuous pre-excitation after disopyramide (2 mg/kg body weight, intravenously) had a sensitivity of 71.4%, specificity of 26.1% and predictive accuracy of 12.8% for identifying patients with sudden death. Continuous pre-excitation during an exercise test identified these patients with a sensitivity of 80%, a specificity of 28.6% and a predictive accuracy of 11.8%. These noninvasive tests could also be used to predict the shortest RR interval observed during induced atrial fibrillation. Continuous pre-excitation on both tests used in combination had a sensitivity of 91.2%, a specificity of 66.7% and a predictive accuracy of 75.6% for predicting the shortest RR interval less than or equal to 250 ms. Thus, both invasive and noninvasive techniques have a good sensitivity but a low specificity for identifying patients with Wolff-Parkinson-White syndrome and sudden death.(ABSTRACT TRUNCATED AT 250 WORDS)
Two patients are described with recurrent pre-excited tachycardia and electrophysiologic characteristics typically ascribed to a nodoventricular accessory connection. The accessory pathway in each case demonstrated rate-dependent prolongation of conduction time and a low right ventricular insertion site; it was associated with a left bundle branch block configuration during pre-excitation. Intraoperatively, the pathway was demonstrated to originate at the anterior right atrioventricular (AV) anulus and not at the AV node. These data suggest that a "typical" nodoventricular pathway, by electrophysiologic criteria, may in fact be an AV pathway with AV node-like conduction properties and a distal right ventricular insertion site.
We found that 130-J biphasic truncated transthoracic shocks defibrillate as well as the 200-J monophasic damped sine wave shocks that are traditionally used in standard transthoracic defibrillators and result in fewer ECG abnormalities after the shock.
Although most asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern have a good prognosis, some die suddenly. The mechanism of sudden death is usually ventricular fibrillation, which is triggered by atrial fibrillation with a rapid ventricular response rate. Electrophysiologic testing has been proposed to identify asymptomatic patients who may be at risk for sudden death. Meaningful application of such testing requires a knowledge of whether the electrophysiologic measurements are reproducible over time. Consequently, we performed electrophysiologic studies on two occasions at least 36 months apart (mean +/- SD, 54.7 +/- 14) in 29 asymptomatic patients with the pattern. Twenty-seven patients remained asymptomatic, and sustained supraventricular tachycardia developed in two during the follow-up period. Nine patients (31 percent) lost the capacity for preexcitation and anterograde conduction over the accessory pathway, which produces the Wolff-Parkinson-White pattern. The others had little change in measurements of conduction over the accessory pathway. Patients who lost conduction over the accessory pathway tended to be older (mean +/- SD, 50 +/- 18 vs. 39 +/- 11 years; P = 0.06) than patients who retained preexcitation, and they had longer anterograde effective refractory periods at the first assessment (414 +/- 158 vs. 295 +/- 27 msec; P = 0.003). We conclude that a considerable number of asymptomatic patients with the Wolff-Parkinson-White pattern lose their capacity for anterograde conduction over the accessory pathway. This loss of capacity probably contributes to the low mortality among asymptomatic patients.
Results from this prospective study of the Wavelet electrogram morphology discrimination algorithm operating as the sole discriminator in the ON mode demonstrate that inappropriate therapy for supraventricular tachycardia in a single-chamber ICD can be dramatically reduced compared to rate detection alone.
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