[A newly-devised nine-lead Holter system for diagnosing myocardial ischemia evaluated using Tl-201 exercise...

A 9-lead Holter monitoring apparatus was devised using a commercially-available 3-lead Holter recorder. The CM5 lead was monitored continuously on channel 1, and our apparatus was applied to channels 2 and 3. Channel 2 was switched serially to V1-like (CM1), V4-like (CM4), V2-like (CM2) and V3-like (CM3) leads every 20 sec. Channel 3 was switched serially to V6-like (CM6), low-back (LB), high lateral (HL) and low-lateral (LL) leads every 20 sec. The study subjects included 98 patients with coronary artery disease. Myocardial ischemia was evaluated by exercise thallium-201 (Tl-201) scintigrams. Functional maps of myocardial perfusion were made from Tl-201 myocardial SPECT studies, and the extent and severity scores were calculated from these maps. The CM5 lead had a high sensitivity for detecting anterior, inferior and lateral wall ischemia, however, its specificity was very low. In contrast, the LB lead had very high sensitivity and high specificity for detecting inferior ischemia (79%, 76%, respectively). The percent extent score and percent severity score determined by the bull's eye method were compared between patients with ST depression of 0.5-1.0 mm and those with that greater than 1.0 mm detected by the LB lead. Both the percent extent score and percent severity score in the latter group were significantly higher than those in the former group (p < 0.001, p < 0.01, respectively), suggesting that the degree of ST depression in the LB lead reflects the degree of myocardial ischemia. The HL and LL leads had high sensitivity and specificity for detecting lateral ischemia. It was concluded that the CM5 lead is necessary for screening global myocardial ischemia and that leads LB and HL (or LL) are mainly useful for detecting inferior and lateral ischemia.