Optimal electrocardiographic leads for detecting acute myocardial ischemia

This study identifies the most sensitive electrocardiographic leads for monitoring ST-segment changes caused by acute coronary ischemia. The data set consisted of 120-lead electrocardiograms (ECGs) digitally recorded during balloon-inflation angioplasty in 3 groups of patients with single-vessel disease (left anterior descending [LAD], 32; right coronary artery [RCA], 36; left circumflex [LCx], 23). The ST deviation was measured in all recorded leads during baseline and ischemic states, and its difference between these 2 states (DeltaST) was calculated at 352 sites and plotted as DeltaST maps. The patients in each group were divided, by means of DeltaST criteria, into subgroups of "responders" and "nonresponders." Mean DeltaSTs for each group/subgroup were calculated and standardized by the corresponding standard deviation (SD); these values were plotted as mean DeltaST and t maps. Sites where extrema of DeltaST occurred most frequently were sought in bootstrap trials, performed in each group/subgroup, The results suggest that the optimal sites for the ischemia-sensitive leads are; V-3 (+) and just below V-8 (-) for LAD-related ischemia; the left iliac crest (+) and above V-2 at the third intercostal space (-) for RCA-related ischemia; and just below V-8 (+) and above V-2 at the third intercostal space (-) for LCx-related ischemia, Three "optimal" bipolar leads using these sites registered, in the responders from the LAD, RCA, and LCx groups, mean DeltaST (+/- SD) of 232 59, 245 96 and 158 +/- 91 muV, respectively; the corresponding t values were 15,14, 9.90, and 6.75. In the 12-lead ECG, only lead V-3 approached optimal DeltaST and t values for the LAD responders (187 +/- 61 muV; t = 11.75) and lead III for the RCA responders (191 +/- 76 muV; t = 9.73), but even these values were significantly Suboptimal (P = 0.0011 and P = 0.0120, respectively). We found that the "optimal" bipolar leads can be derived, to an excellent approximation, from the 12 standard leads or from 3 EASI leads (with 3 electrodes at Frank's transverse level and I on the manubrium), by using precalculated regression coefficients. By means of bootstrap trials, we estimated the mean sensitivity (SE) and the mean positive predictive value (PPV) with which 3"optimal" vessel-specific leads Could identify ischemia related to the LAD, RCA, and LCx arteries, in the test set, as (SE/PPV) 94.7/92.8%, 78.7/80.9 %, and 81.5/80.9%. A similar diagnostic performance can be achieved by vessel-specific leads derived from the 12-lead ECG (93.0/93.4%, 76.6/82.0%, and 82.7/77.1 %) and, interestingly, from the EASI lead system (97.8/88.4%, 78.0/80.2%, and 76.8/83.2%). Thus, although the,optimal" bipolar leads for detecting ischemia related to each of the 3 coronary arteries were found to require sampling outside the 12-lead ECG, these leads can be derived from the full set of 12 standard leads or-for clinical monitoring applications-from the EASI lead system by using fewer electrodes at convenient locations.