239. Increased QT variability in patients with panic disorder and depression

Abstract

This study investigated beat-to-beat QT variability in patients with panic disorder and depression, and normal controls using an automated algorithm to compute QT intervals. An increase in QT variability is associated with symptomatic patients with dilated cardiomyopathy and also with an increased risk for sudden cardiac death. We have recently reported a significant increase in QTvi (a log ratio of QT variance normalized for mean QT over heart rate variability normalized for mean heart rate) during standing posture compared to supine condition, and also after intravenous isoproterenol suggesting that an increase in sympathetic activity is associated with an increased QT variability. QTvm (QT variability normalized for mean QT interval) was significantly higher in patients compared to controls in supine as well as standing postures (p = 0.002). QTvi was also significantly higher in patients with panic disorder (supine: −1.65 ± 0.38; standing: −1.17 ± 0.38) and depression (supine: −1.48 ± 0.39; standing: −1.17 ± 0.43) compared to controls (supine: −1.95 ± 0.28; standing: −1.47 ± 0.33) (p = 0.0001). In another analysis, QTvi was significantly higher in patients with panic disorder compared to controls in supine as well as standing postures during spontaneous breathing as well as 12, 15 and 20 per minute breathing (p = 0.005). These findings are important especially in view of the recent reports of increased risk for cardiovascular mortality and sudden death in patients with anxiety and depression and the utility of QTvi as a noninvasive measure of temporal repolarization lability. Future studies should focus on the effects of various psychotropics on QTvi.