Objective To study electrocardiographic measures of ventricular repolarisation dispersion in patients prone to ventricular fibrillation compared with controls matched for the extent of coronary heart disease and the use of β blockers.

Design A case-control study.

Setting Cardiovascular laboratory of a tertiary referral centre.

Patients Fifty patients with documented ventricular fibrillation not associated with acute myocardial infarction, and their controls matched for sex, age, number of diseased coronary vessels, left ventricular ejection fraction, previous myocardial infarction and its location, and the use of β blockers.

Main outcome measures Electrocardiographic measures of QT, JT, and T_end interval dispersions in a 12 lead electrocardiogram.

Results The ventricular fibrillation patients compared to controls showed increased mean (SD) QT_apexdispersion (53 (18) ms v 44 (18) ms, respectively; p < 0.01) and mean (SD) T_end dispersion (46 (17) msv 38 (15) ms, respectively; p < 0.05).

Conclusions Increased QT_apex and T_end dispersions are associated with a susceptibility to ventricular fibrillation even when the extent of the coronary heart disease and use of β blockers are taken into consideration. However, because of a considerable overlap between the groups, measures of QT dispersion assessed from a 12 lead electrocardiogram do not provide clinically useful information for identification of patients at risk of sudden cardiac death.