Beat-to-Beat Electrocardiographic Variation in Healed Myocardial
Morphology Infarction
Shlomo A. Ben-Haim, MD, DSc, Bruno Becker, MD, Yeouda Edoute, MD, PhD, Mira Kochanovski, MD, Orly Azaria, BSC, Elieser Kaplinsky, MD, and Yoram Palti, MD, PhD wo basic types of electrophysiologic derangement can be demonstratedin healed myocardial infarction. One involves delayed activation that is stable and fried in time. Such an abnormality can easily be detected by the current electrocardiographic (ECG) averaging techniques. Numerous studies have correlated the presenceof fixed and reproducible delayed activity with subsequentlethal arrhythmias and mortality.1-4 The secondtype of electrophysiologic derangement is not accessible to the current averaging techniques. This involves unstable and constantly changing patterns of delayed activity, documented in numerous experimental investigations using direct recording from the heart. Such unstable and variable patterns of electrophysiologic activity, from beat to beat, have been demonstratedin acutely ischemic myocardium.5 In chronic healed myocardial infarction, the fmed and delayed reproducible activity may becomeunstable and variable from beat to beat by various stressstimuli (such as catecholaminesand rapid rate pacing).6 However, theoretically one would expect beat-to-beat variability in the electrocardiogram to occur in patients with healed myocardial infarction, even without stressing the heart. This beat-to-beat variability may arise from the increased dispersion of electrophysiologic characteristics present in healed infarction myocardiurn. Under such conditions, propagation of the electrical activation of each beat is dependenton the route of propagation of the previous beat. Therefore, propagation of activation may travel through different routes for each heartbeat, causing the ECG morphology to become beat variable. Becauseit is impossible to record these individual small beat-to-beat variations associatedwith myocardial injury, we designeda system to measure the degree of variability at different regions of interest within the From the Cardiovascular ResearchGroup, Rappaport Family Institute for Researchin the Medical Sciences,and the Department of Physiolc- QRS complex. The present study was designed to ingy and Biophysics, Faculty of Medicine, Technion-Israel Institute of vestigate whether indeed individual beat-to-beat variTechnology,Haifa, the Department of Cardiology, Meir Hospital, Kfar Saba, and the Heart Institute, Chaim Sheba Medical Center, Tel Ha- ability in the ECG morphology exists in patients with shomer, Tel Aviv, Israel. This study was supported in part by Grant recent healed myocardial infarction. Using high-fidelity electrocardiographic (ECG) amplifiers, we measured subtle beat-to-beat ECG morphologic variations at different phases of the ECG complex. The electrocardiograms were recorded from 49 men with a documented Q-wave myocardial infarction and from 30 agematched normal men. Forty consecutive beats were averaged to achieve an average ECG signal from whii variance could be calculated. The relative variance, defined as the ratio between the integrated variance of the examined window and the integrated variance of the EC0 signal that was close to full cycle length, was calculated at QRS onset and at offset in 2 frequency bands (4 to 40 and 60 to 120 Hz). Patients with healed infarction had a relative variance of 2.1 f 0.5 (mean f standard deviation [SD]) at QRS offset (a window of 40 ms), which was significantly lower than that of the healthy vohmteers: 2.5 f 0.33 (mean f SD; p
Morphology Infarction
Shlomo A. Ben-Haim, MD, DSc, Bruno Becker, MD, Yeouda Edoute, MD, PhD, Mira Kochanovski, MD, Orly Azaria, BSC, Elieser Kaplinsky, MD, and Yoram Palti, MD, PhD wo basic types of electrophysiologic derangement can be demonstratedin healed myocardial infarction. One involves delayed activation that is stable and fried in time. Such an abnormality can easily be detected by the current electrocardiographic (ECG) averaging techniques. Numerous studies have correlated the presenceof fixed and reproducible delayed activity with subsequentlethal arrhythmias and mortality.1-4 The secondtype of electrophysiologic derangement is not accessible to the current averaging techniques. This involves unstable and constantly changing patterns of delayed activity, documented in numerous experimental investigations using direct recording from the heart. Such unstable and variable patterns of electrophysiologic activity, from beat to beat, have been demonstratedin acutely ischemic myocardium.5 In chronic healed myocardial infarction, the fmed and delayed reproducible activity may becomeunstable and variable from beat to beat by various stressstimuli (such as catecholaminesand rapid rate pacing).6 However, theoretically one would expect beat-to-beat variability in the electrocardiogram to occur in patients with healed myocardial infarction, even without stressing the heart. This beat-to-beat variability may arise from the increased dispersion of electrophysiologic characteristics present in healed infarction myocardiurn. Under such conditions, propagation of the electrical activation of each beat is dependenton the route of propagation of the previous beat. Therefore, propagation of activation may travel through different routes for each heartbeat, causing the ECG morphology to become beat variable. Becauseit is impossible to record these individual small beat-to-beat variations associatedwith myocardial injury, we designeda system to measure the degree of variability at different regions of interest within the From the Cardiovascular ResearchGroup, Rappaport Family Institute for Researchin the Medical Sciences,and the Department of Physiolc- QRS complex. The present study was designed to ingy and Biophysics, Faculty of Medicine, Technion-Israel Institute of vestigate whether indeed individual beat-to-beat variTechnology,Haifa, the Department of Cardiology, Meir Hospital, Kfar Saba, and the Heart Institute, Chaim Sheba Medical Center, Tel Ha- ability in the ECG morphology exists in patients with shomer, Tel Aviv, Israel. This study was supported in part by Grant recent healed myocardial infarction. Using high-fidelity electrocardiographic (ECG) amplifiers, we measured subtle beat-to-beat ECG morphologic variations at different phases of the ECG complex. The electrocardiograms were recorded from 49 men with a documented Q-wave myocardial infarction and from 30 agematched normal men. Forty consecutive beats were averaged to achieve an average ECG signal from whii variance could be calculated. The relative variance, defined as the ratio between the integrated variance of the examined window and the integrated variance of the EC0 signal that was close to full cycle length, was calculated at QRS onset and at offset in 2 frequency bands (4 to 40 and 60 to 120 Hz). Patients with healed infarction had a relative variance of 2.1 f 0.5 (mean f standard deviation [SD]) at QRS offset (a window of 40 ms), which was significantly lower than that of the healthy vohmteers: 2.5 f 0.33 (mean f SD; p
