Usefulness of a third holter lead for detection of myocardial ischemia

Abstract

Two-channel ambulatory electrocardiographic (ECG) monitoring is a useful method for detecting translent myocardial ischemia in patients with coronary artery disease. However, the monitoring of only 2 leads may fail to detect a significant number of ischemic episodes. In this study, the additional diagnostic value of a third bipolar chest lead was evaluated by recording a simultaneous 12-lead electrocardiogram and a 3-channel ambulatory electrocardiogram during exercise testing in 223 patients (aged 63 ± 10 years) with proved or suspected coronary disease. Leads CM 5, CM 3, and an inferior lead (Y-modfied or CMf) were monitored on the ambulatory electrocardiogram. Diagnostic ST-segment depression on the standard electrocardiogram was detected in 98 patients (44%), 94 (96%) of whom also had diagnostic ST-segment changes on the ambulatory electrocardiogram. Two additional patients had ST-segment depression only on the ambulatory electrocardiogram (both in lead CM 5). Maximal ST-segment depression and duration of Ischemia detected on standard and ambulatory ECG leads were similar in the 94 patients in whom ST-segment changes were detected on both types of ECG monitoring. CM 5 was the single lead with the highest sensitivity (89%) in detecting myocardial ischemia. The addition of CM 3 to CM 5 increased sensitivity to 91%, and the addition of an inferior lead to CM 5 increased sensitivity to 94%, particularly improving the detection of isolated inferior myocardial ischemia. The combination of all 3 ambulatory ECG leads had a sensitivity of 96%, an improvement of only 2% compared with the best combination of 2 leads (i.e., CM 5 ± inferior lead). Thus, these data indicate that the addition of a third bipolar chest lead to ambulatory ECG devices has limited clinical relevance for improving the detection of transient ST-segment depression. They also indicate that the monitoring of an inferior lead may significantly improve the detection of isolated inferior ischemia.