Increased QT variability in patients with panic disorder and depression

This study investigated beat-to-beat QT variability in patients with panic disorder and depression, and normal control subjects using an automated alg orithm to compute QT intervals. An increase in QT variability appears to be associated with symptomatic patients with dilated cardiomyopathy and also with an increased risk for sudden death. QT(vm) (QT variability normalized for mean QT interval) and QT(vi) (a log ratio of QT variance normalized for mean QT over heart rate variability normalized for mean heart rate) were s ignificantly higher in patients with panic disorder and depression in supin e as well as standing postures (P = 0.002 and 0.0001 for QT(vm) and QT(vi), respectively). In another analysis, QT(vi) was significantly higher in pat ients with panic disorder compared to control subjects in supine as well as standing postures during spontaneous breathing as well as 12, 15 and 20 pe r minute breathing (P = 0.005). These findings are important especially in view of the recent reports of increased risk for cardiovascular mortality a nd sudden death in patients with anxiety and depression and the utility of QT(vi) as a noninvasive measure of temporal repolarization lability. (C) 20 00 Elsevier Science Ireland Ltd. All rights reserved.