Unusual fascicular extrasystoles: where is the site of origin?

Radiofrequency ablation for symptomatic, drug refractory premature ventricular contractions has been well established as a treatment modality. Mapping of ventricular ectopy that arises near the native conduction system can be challenging. We report a case of fascicular ectopy arising from the proximal His (H)-Purkinje system that was successfully mapped and ablated. The use of surface and intracardiac electrograms and timing of the His bundle and/or Purkinje potentials is crucial in identifying the exact site of origin.

Prolonged QTc interval and risks of total and cardiovascular mortality and sudden death in the general population: a review and qualitative overview of the prospective cohort studies.

BACKGROUND: In certain subgroups of patients, prolongation of the QTc interval may increase total and cardiovascular mortality due to life-threatening ventricular arrhythmias and sudden death. Nonetheless, whether modest prolongation of the QTc interval in the general population has clinical importance remains unclear. METHODS: We conducted a literature search from 1990 forward to identify all published prospective cohort studies evaluating the association between prolonged QTc interval and risks of total and cardiovascular mortality as well as sudden death. We reviewed each of the studies individually and then conducted a qualitative overview. RESULTS: The 7 prospective cohort studies identified included 36 031 individuals. There were 2677 (8.7%) individuals with prolonged QTc interval, defined as 440 milliseconds or greater. Whereas 1 study reported no association between prolonged QTc interval and mortality (relative risk, 1.02; 95% confidence interval, 0.70-1.49), the other 6 reported inconsistent associations overall as well as across subgroups defined by various characteristics including age, sex, and comorbidities. The reported associations for both cardiovascular mortality and sudden death were also inconsistent. In the overview, the only consistent findings were for the subgroup of patients with prior cardiovascular disease, in which relative risks ranged from 1.1 to 3.8 for total mortality, from 1.2 to 8.0 for cardiovascular mortality, and from 1.0 to 2.1 for sudden death. Further, in individuals without prior cardiovascular disease, associations were either absent or greatly attenuated; specifically, relative risks ranged from 0.9 to 1.6 for total mortality, from 1.2 to 1.7 for cardiovascular mortality, and from 1.3 to 2.4 for sudden death. CONCLUSIONS: There was no consistent evidence for increased risks of total or cardiovascular mortality or of sudden death, except perhaps for patients with prior cardiovascular disease. In the general population, if QTc interval prolongation is associated with any increase in mortality, that risk is likely to be small and difficult to detect reliably.

Pacemaker mode selection: the evidence from randomized trials.

The evidence base for pacing, specifically with regards to outcome-based randomized trials, is only beginning to emerge. At present, the guidelines for pacing in sinus node dysfunction (SND), atrioventricular block (AVB), and vasovagal syncope are largely based on observational, not randomized studies. The findings from observational studies that physiological pacing was associated with reduced mortality, fewer strokes, less heart failure, and less AF when compared with ventricular pacing, were not uniformly supported by the early randomized trials of a relatively small sample size. Thus, it has become increasingly clear that large scale randomized trials are necessary to measure reliably the benefit, if any, of progressively more expensive and complex pacemakers. To provide reliable answers to these important questions, three large multicenter randomized trials in Canada, the United Kingdom, and the United States have been designed and conducted. The present review analyzed the results of completed randomized trials on pacemaker mode selection. To date, > 6,000 patients requiring permanent pacing to prevent bradycardia have been randomized; among these, dual chamber pacing did not prevent stroke or improve survival when compared with ventricular pacing. However, dual chamber pacing led to a moderate reduction of incident and chronic AF, reduced symptoms of heart failure in patients with SND, prevented pacemaker syndrome, and modestly improved quality-of-life. Further, a 5-10% reduction in mortality by atrial-based pacing cannot be excluded based on the results of the analyzed trials. The availability of data from ongoing randomized trials and their meta analysis should complete the totality of evidence during the next several years.