THE PROGNOSTIC VALUE OF THE QT INTERVAL AND QT INTERVAL DISPERSION INALL-CAUSE AND CARDIAC MORTALITY AND MORBIDITY IN A POPULATION OF DANISH CITIZENS

Aims. To evaluate the prognostic value of the QT interval and QT inter val dispersion in total and in cardiovascular mortality, as well as in cardiac morbidity, in a general population. Methods and results. The QT interval was measured in all leads from a standard 12-lead ECG in a random sample of 1658 women and 1797 men aged 30-60 years. QT interva l dispersion was calculated from the maximal difference between QT int ervals in any two leads. All cause mortality over 13 years, and cardio vascular mortality as well as cardiac morbidity over 11 years, were th e main outcome parameters. Subjects with a prolonged QT interval (430 ms or more) or prolonged QT interval dispersion (80 ms or more) were a t higher risk of cardiovascular death and cardiac morbidity than subje cts whose QT interval was less than 360 ms, or whose QT interval dispe rsion was less than 30 ms. Cardiovascular death relative risk ratios, adjusted for age, gender, myocardial infarct, angina pectoris, diabete s mellitus, arterial hypertension, smoking habits, serum cholesterol l evel, and heart rate were 29 for the QT interval (95% confidence inter val 1.1-7.8) and 4.4 for QT interval dispersion (95% confidence interv al 1.0-19.1). Fatal and non-fatal cardiac morbidity relative risk rati os were similar, at 2.7 (95% confidence interval 1.4-5.5) for the QT i nterval and 2.2 (95% confidence interval 1.1-4.0) for QT interval disp ersion. Conclusion. Prolongation of the QT interval and QT interval di spersion independently affected the prognosis of cardiovascular mortal ity and cardiac fatal and non-fatal morbidity in a general population over Il years.