Accurate rapid compact analog method for the quantification of frequency and duration of myocardial ischemia by semiautomated analysis of 24-hour Holter ECG recordings

Abstract

Although the semiautomated analysis of 24-hour Holter recordings is now widely used in the detection and quantitation of disorders of cardiac rhythm and conduction, there are still no comparable methods for routine clinical use for the detection of the frequency and duration of myocardial ischemic episodes in patients with coronary artery disease (CAD). Research methods available to detect ischemic ST-T wave changes depend on sophisticated computer systems, are ill-suited for clinical use, and are not readily validated. However, when Holter tape is replayed at 60 times real time on heat-sensitive paper recorder at slow speeds (3.3 to 10 cm/min), rapid compact analog representation of 24-hour recording can be compressed into 480 to 1440 cm of paper. By this method, the close juxtaposition of QRST complexes produces distinctive patterns; from these the frequency and duration of myocardial ischemic episodes can be identified promptly, accurately, and reproducibly. When combined with conventional Holter scanning assembly, the accuracy of detection can be validated continuously by intermittent printout of the abnormality and ventricular ectopy can be quantitated simultaneously. The analysis of a technically acceptable 24-hour recording can be accomplished in 24 to 40 minutes (at 60 times real time playback) by an experienced operator. The fast compact analog representation of two-channel 24-hour recordings permitted the reliable detection of ST segment elevation and depression, pseudonormalization of ST-T wave abnormality, T wave augmentation, AV block, ventricular tachycardia, and intermittent bundle branch blocks. The technique also allowed the relationship of chest pain to the onset of ischemia to be established. Holter recordings from 22 CAD patients known to have myocardial ischemic episodes were examined; 275 episodes with ST segment deviations were identified, 92 (33.5%) being associated with angina which developed 2 to 18 minutes after the onset of ischemia. The method of compact analog ECG signal recording proved considerably superior to ST segment trend plotting; our data indicate that when combined with intermittent printout of observed abnormalities, the technique is simple, rapid, and extremely accurate in identifying the frequency and duration of myocardial ischemia from two-channel 24-hour Holter recordings. It permits the use of Holter monitoring for the noninvasive detection of myocardial ischemic episodes in a manner analogous to the quantitation and drug-induced suppression of ventricular ectopy from continuous ECG recording.