CLINICALLY SILENT ELECTROCARDIOGRAPHIC ABNORMALITIES AND RISK OF PRIMARY CARDIAC-ARREST AMONG HYPERTENSIVE PATIENTS

Background Whether continuous ECG indexes that reflect the severity of left ventricular hypertrophy (LVHI), myocardial injury (CIIS), and QT -interval prolongation (QTI) are associated with the risk of primary c ardiac arrest among hypertensive patients, independent of conventional binary ECG criteria, remains unknown. Methods and Results We conducte d a population-based case-control study among patients who were free o f clinically recognized heart disease and who received care at a healt h maintenance organization. Cases (n=131) were treated hypertensive pa tients who had had a primary cardiac arrest between 1977 and 1990. Con trols (n=562) were a stratified random sample of treated hypertensive patients. Resting ECGs were reviewed to estimate the severity of left ventricular hypertrophy, myocardial injury, and QT-interval prolongati on on the basis of the algorithms of the Novacode ECG classification s ystem. After adjustment for other risk factors and binary ECG criteria for the abnormalities, the LVHI, CIIS, and QTI scores were directly r elated to the risk of primary cardiac arrest. In a comparison of the 8 0th with the 20th percentile score for the LVHI, the risk was in creas ed 40% (odds ratio, 1.4; 95% CI, 1.0 to 2.0); for the CIIS, the risk w as increased 70% (odds ratio, 1.7; 95% CI, 1.2 to 2.5); and for the QT I, the risk was increased 80% (odds ratio, 1.8; 95% CI, 1.3 to 2.7). C onclusions Our findings suggest that continuous ECG indexes that refle ct left ventricular hypertrophy, myocardial injury, and QT-interval pr olongation are directly related to the risk of primary cardiac arrest among hypertensive patients without clinically recognized heart diseas e. Binary ECG criteria may underestimate the prognostic importance of these pathophysiological abnormalities.