BEAT-TO-BEAT QRS VARIABILITY IN THE 12-LEAD ECG AND THE DETECTION OF CORONARY-ARTERY DISEASE

The aim of this article was to study beat-to-beat QRS variability in p atients with ischemia and old myocardial infarction using the 12-lead resting electrocardiogram (BCG). The variability analysis was based on beats that have been synchronized in time with an iterative alignment technique. The QRS variability was measured in patients submitted for myocardial scintigraphy. Those with a normal myocardial scintigraphy (called NO, n = 34, mean age 57 years, 23 women) were compared with a group with both myocardial infarction and exercise-induced ischemia (c alled ISCINF, n = 27, mean age 57 years, 5 women). The mean QRS variab ility was somewhat smaller in lead I in ISCINF than in NO, and there w as no statistically significant difference in QRS variability among th e groups in leads II, III, and V-1-V-6. Using a multivariate approach, the joint variability in leads I, II, III, and V-1-V-6 was used for c alculating receiver operating characteristics based on a leave-one-out procedure. The sensitivity for detecting coronary artery disease was 75% at a specificity of 50%. It is concluded that beat-to-beat QRS var iability in the 12-lead ECG does not discriminate between the presence and absence of coronary artery disease sufficiently well for clinical purposes.