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Nine-lead Holter monitoring using a lead-switching technique for the detection of ischemic ST changes.

We devised a technique to record a greater number of leads (a 9-lead monitor) by connecting a lead-switching adaptor to a commercially available 3-channel Holter recorder (9-lead DCG). Anodes were attached from positions V1 to V6 (CM1 to CM6), and to high lateral (HL), low lateral (LL) and low back (LB). A cathode was attached to the manubrium of the sternum. The CM5 lead was continuously recorded on channel 1. The device is able to switch continuously every 20 sec among leads CM6, LB, HL and LL on channel 2, and among leads CM1, CM4, CM2, and CM3 on channel 3. Electrocardiograms were simultaneously recorded with both the 9-lead DCG and the conventional 12-lead ECG systems during treadmill testing in 67 patients with coronary artery disease. In addition, 6 patients with acute myocardial infarction were studied with the 9-DCG to test ST elevation. The sensitivity and specificity of leads CM2 to CM6, HL, LL, and LB in detecting ST depressions that occurred in each corresponding lead of the 12-lead ECG lead were very high (p < 0.0001). The LB lead in particular was noteworthy for its markedly high specificity (94%) and sensitivity (83%) in detecting ST depressions occurring in leads II and aVF. Our lead-switching technique is useful when an increase in the number of leads is required in the DCG method. The LB lead, an anode on the low back, may be specific to detect inferior myocardial ischemia.