Background: Polymorphic ventricular tachycardia (VT) without QT prolongation is well described in patients without structural heart disease (mainly idiopathic ventricular fibrillation and Brugada syndrome) and in patients with acute ST-elevation myocardial infarction. Methods: Retrospective study of patients with polymorphic VT related to coronary artery disease, but without evidence of acute myocardial ischemia. Results: The authors identified 43 patients in whom polymorphic VT developed within days of an otherwise uncomplicated myocardial infarction or coronary revascularization procedure. The polymorphic VT events were invariably triggered by extrasystoles with short (364±36 ms) coupling interval. Arrhythmic storms (4–16 events of polymorphic VT deteriorating to ventricular fibrillation) occurred in 23 (53%) patients. These arrhythmic storms were always refractory to conventional antiarrhythmic therapy, including intravenous amiodarone, but invariably responded to quinidine therapy. In-hospital mortality was 17% for patients with arrhythmic storm. Patients treated with quinidine invariably survived to hospital discharge. During long-term follow-up (of 5.6±6 years; range, 1 month to 18 years), 3 (16%) of patients discharged without quinidine developed recurrent polymorphic VT. There were no recurrent arrhythmias during quinidine therapy Conclusions: Arrhythmic storm with recurrent polymorphic VT in patients with coronary disease responds to quinidine therapy when other antiarrhythmic drugs (including intravenous amiodarone) fail.

Background-Atrioventricular nodal reentrant tachycardia (AVNRT) is considered a sporadic disease occurring in ≈22.5cases per 10 000 in the general population. We define the prevalence and characteristics of familial AVNRT among patients who underwent radiofrequency ablation. Methods and Results-Ablation reports of all patients with familial AVNRT (at least 2 first-degree family members) who underwent radiofrequency ablation in our institution and in another hospital were reviewed. There were 1587 patients from our institution, of whom 20 had ≥1 first-degree relatives with AVNRT. This indicates a familial AVNRT prevalence of 127 cases per 10 000 (95% confidence interval, 82-196/10 000). First-degree relatives of patients with AVNRT presented a hazard ratio of at least 3.6 for exhibiting AVNRT compared with the general population. After inclusion of 4 families with familial AVNRT who underwent ablation at another hospital our population study comprised a total of 24 families (50 patients) with AVNRT. Patients at ablation were younger in the familial AVNRT group when compared with the sporadic AVNRT group (44.2±19 versus 54.8±18 years old, P=0.0001). The male/female ratio was similar, with female predominance. The supraventricular tachycardia mechanism was typical slow/fast reentry in most cases in both groups.The most common familial relationship in our 24 families included a parent and a child in 67% of cases and less often 2 siblings (29%). Conclusions-Familial AVNRT prevalence is higher than previously believed suggesting that this arrhythmia may have a genetic component. Autosomal dominance with incomplete penetrance is the most likely mode of inheritance.