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This study demonstrates that patients with poorer conduction properties of the anterograde slow and retrograde fast pathways usually need isoproterenol to facilitate induction of atrioventricular nodal reentrant tachycardia. Isoproterenol infusion usually facilitates induction of tachycardia by enhancing the retrograde ventriculoatrial conduction.

We conclude that most patients with transient AV block are clinically and electrocardiographically stable over a long follow-up time; thus, whether such patients will eventually have complete AV block is as yet unknown.

In western populations, patients with hypertension who have a nocturnal decrease in blood pressure (BP) may have less left ventricular (LV) hypertrophy and cardiovascular morbidity than those without a diurnal variation in BP. To further examine this association between nocturnal BP reduction and LV mass index, we studied 720 normotensives ( or = 160/95 mm Hg) from Taiwan and Quemoy island by using 24-hour ambulatory BP monitoring and 2-dimensional echocardiography to obtain LV mass index during a community-based cardiovascular survey. After controlling for age, sex, height, weight, daytime BP, and daytime heart rate, the nocturnal reduction of systolic BP was found to associate weakly with LV mass index, for the whole population (partial correlation coefficient = -0.06, p < 0.05), as well as for the patients with hypertension (partial correlation coefficient = -0.09, p < 0.05), but these associations were eliminated when 24-hour BP and heart rate were accounted for. The average and percent nocturnal decrease of systolic BP (mean +/- SD; mm Hg, [%]) of 3.2 +/- 5.9 (2.7 +/- 4.8%); 3.3 +/- 7.3 (2.4 +/- 5.4%); and 4.6 +/- 9.0 (3.0 +/- 6.1%) in normotensives, borderline hypertensives, and hypertensives, respectively, was smaller than that found in previous studies. Hence, in this large Chinese population, a small nocturnal BP drop was found and it was only weakly associated with LV mass index. These results emphasize the general need for ambulatory BP reference values based on internal controls.

To evaluate and compare the safety and efficacy of catheter-mediated direct-current (DC) or radio-frequency (RF) ablation in patients with free wall accessory atrioventricular pathways, 95 patients with free wall accessory atrioventricular pathway-mediated tachyarrhythmias underwent catheter ablation. Immediately after ablation, 27 of 30 accessory pathways (90%) were ablated successfully with DC, but 2 of the 27 had early return of conduction and received a second ablation session; 3 of 8 (38%) and 57 of 62 (92%) accessory pathways were ablated successfully with RF through a small-tip (2 mm) and a large-tip (4 mm) electrode catheter, respectively. Complications in DC ablation included transient hypotension (2 patients) and pulmonary air-trapping (2 patients) and in RF ablation, cardiac tamponade (1 patient) and suspicious aortic dissection (1 patient); myocardial injury and proarrhythmic effects were more severe in DC ablation. Procedure and radiation exposure time were significantly longer in RF ablation (DC, 3.6 ± 0.2 hours, 34 ± 4 minutes; RF 4.2 ± 0.5 hours, 50 ± 10 minutes). This study confirms that RF ablation is associated with little morbidity and few complications, and RF ablation with a large-tip electrode catheter is an effective and relatively safe nonsurgical method for treatment of free wall accessory atrioventricular pathway-mediated tachyarrhythmias.

Predictors and comparisons of complications in patients with electrophysiologic study or radiofrequency ablation have not been assessed in previous published reports. The purpose of this study was to prospectively evaluate the procedure-specific complications and investigate the possible causes and predictors of complications in electrophysiologic study and radiofrequency ablation. Data of diagnostic electrophysiologic studies and radiofrequency ablation were prospective, and represented a consecutive series of 2,593 patients with 3,966 procedures. The present study showed that a significantly higher complication rate occurred in radiofrequency ablation than in electrophysiologic study (3.1% vs. 1.1%, respectively, p = 0.00002) and a significantly higher complication rate occurred in elderly than in young patients with electrophysiologic study (2.2% vs 0.5%, p = 0.0002) or radiofrequency ablation (6.1% vs 2.0%, p = 0.00015). Multiple logistic analysis found that older age (p0.01) and systemic disease in elderly patients (p0.01) were the independent predictors of complications in both procedures. Furthermore, there was no temporal trend in the incidence of complication. We conclude that the incidence of complication was higher in radiofrequency ablation, and elderly patients had a higher incidence of complications in both electrophysiologic study and radiofrequency ablation; these procedures, when performed by experienced personnel in an appropriately staffed and equipped laboratory, can be undertaken with an acceptable risk.