QT dispersion in patients with social phobia

QT dispersion (QTd) is the maximal interlead difference in QT interval on the surface 12-lead electrocardiogram (ECG). An increase in QTd is found in various cardiac diseases and reflects cardiac autonomic imbalance. It has recently been associated with increased anxiety levels, thereby predisposing affected individuals to fatal heart disease. This is the first study to assess QTd in social phobia, as a marker of anxiety-induced cardiac dysregulation.

QTd and rate-corrected QTd were measured in 16 physically healthy and non-depressed outpatients with long-term (mean 28+/-12.2 years; age 37.9+/-9.6 years) social phobia (SP) and in 15 physically and mentally healthy age- and gender-matched controls. The Liebowitz Social Anxiety Scale (LSAS) was scored concomitantly. The intra- and inter-observer reproducibilities of QTd were highly correlated (r=0.96, P<0.001; r=0.74, P=0.002, respectively).

QTd and rate-corrected QTd were significantly higher in the patients with SP compared to the controls (70+/-21 versus 43+/-10 ms, P<0.001 and 75+/-23 versus 46+/-10 ms, P<0.001, respectively), and highly correlated with the two LSAS subscores.

Prolonged SP is associated with an increase in QTd. This association may result from prolonged anxiety and, in turn, a decrease in vagal modulation and/or increase in sympathetic modulation. Further large-scale epidemiological studies are needed to determine if increased QTd can serve as a trait/state marker, and if it is a risk factor for sudden cardiac death in patients with SP.