Is idiopathic ventricular fibrillation a short QT syndrome? Comparison of QT intervals of patients with idiopathic ventricular fibrillation and healthy controls

Objective. The purpose of this study was to determine if patients with idiopathic ventricular fibrillation (VF) have shorter QT intervals than comparable healthy controls. Background. The upper limit of the normal Q T is well defined. Less is known about the lower limit of the normal QT. Patients with the recently described "short QT syndrome" have characteristics resembling those of patients with idiopathic VF. Methods. The ECGs of 28 consecutive patients with idiopathic VF (17 men and 11 women, age 31 ± 17 years) were compared to those of 270 age- and gender- matched healthy controls. Based on published literature, we defined "short QT" as QTc ≤ 360 ms for males and ≤ 370 ms for females. Results. Despite signific ant overlapping, the QTc of males with idiopathic VF was shorter than the QTc of healthy males (371 ± 22 ms vs 385 ± 19 ms, P = .034). Short QT intervals were found more frequently among males with idiopathic VF (35% vs 10%, P = .003). No such differences were apparent among women. Short QTc intervals were more commonly seen during bradycardia. However, the correlation between short QT and a history of VF was independent of heart rate. Conclusions: "Short" QTc values are commonly seen in male patients with idiopathic VF. However, "short" QTc values are not rare among healthy adults, especially at slow heart rates. Further studies are needed to define when a given QT is really "too short.".