BEAT-TO-BEAT QRS AMPLITUDE VARIABILITY AFTER ACUTE MYOCARDIAL-INFARCTION AND CORONARY-ARTERY BYPASS-GRAFTING

Ischemic myocardial injury has been demonstrated to be associated with increased beat-to-beat electrical variability of the depolarization p hase. This can be quantified by electrocardiographic (EGG) signal vari ance analysis, a technique that has proven its diagnostic value in the detection of coronary artery disease (CAD). This study evaluates QRS amplitude variability during a 6-month follow-up period in 73 patients with acute myocardial infarction (AMI) and in 56 patients subjected t o coronary artery bypass grafting (CABG). The beat-to-beat QRS amplitu de variability was quantified with variance electrocardiography. The e quipment allows computerized time domain analysis of high-fidelity ECG signals from 24 leads, and the detected electrical heterogeneity is t hen expressed as a nondimensional index ranging from 0 to 150, with va lues > 90 being indicative of ischemic myocardial involvement. One wee k after AMI 55% of the patients presented with an abnormal QRS variabi lity index > 90. A significant (p < 0.01) increase in the index values occurred during the follow-up period, but only in the patients with a n initial index < 70. in the CABG group 44% of the patients had a preo perative QRS variability index > 90. The values increased (p < 0.05) i n all patients after surgery; the increase was transient in patients w ith an initial index < 70 (p < 0.01). The results demonstrate that the myocardial injury in patients with CAD is often associated with incre ased electrical variability of myocardial depolarization. The QRS ampl itude variability index can be used as a marker of such an injury, and analysis of its changes in the course of ischemic cardiac events may provide new insights into the dynamics of ischemic heart diseases and the mycardial healing process.