QT INTERVAL DISPERSION - A NONINVASIVE MARKER OF SUSCEPTIBILITY TO ARRHYTHMIA IN PATIENTS WITH SUSTAINED VENTRICULAR ARRHYTHMIAS

Objective-To assess QT interval dispersion on the surface electrocardi ogram in patients with sustained ventricular arrhythmias. Design-A ret rospective and prospective blinded controlled study of patients referr ed for investigation of ventricular arrhythmias at a tertiary cardiac centre. Patients and methods-89 consecutive patients with sustained ve ntricular arrhythmias due to chronic ischaemic heart disease, cardiomy opathy, or ventricular tachycardia (VT) in a normal heart. 32 patients did not meet the inclusion criteria; therefore 57 patients were compa red with a control group of 40 patients with myocardial disease but no history of arrhythmias and 12 normal controls with no myocardial dise ase. Standard 12 lead electrocardiograms were enlarged, the QT interva ls for each lead measured, and QT dispersion calculated. Results-There was a significantly greater mean QT dispersion (77 ms) in patients wi th sustained ventricular arrhythmias compared with the control group ( 38 ms, p < 0.01). This held for all groups; after myocardial infarctio n VT (82 (22) ms v control 38 (10) ms; p < 0.01), dilated cardiomyopat hy VT (76 (18) ms v control 40 (11) ms, p < 0.01), and normal heart VT (65 (7) ms v control 32 (8), p < 0.05). There was also a greater QT d ispersion in patients with impaired left ventricular function and VT, with a correlation between left ventricular function and QT dispersion in patients with VT (r = 0.56, p < 0.01). Conclusion-QT interval disp ersion may be a further non-invasive marker of susceptibility to ventr icular arrhythmias.