Improved electrocardiographic detection of hyperacute ischemia by difference vector analysis

Background. The ECG is important for diagnosis and triage in the hyperacute phase of acute coronary syndrome (ACS), especially during the “golden hours”, when myocardial salvage possibilities are largest. An important triaging decision is whether or not a patient requires primary PCI, for which the guidelines mention ST elevation (STE) in the ECG as major criterion. This criterion has, however, a low sensitivity and specificity. Methods. We investigated the diagnostic possibilities of ischemia detection by means of changes in the ST vector, ΔST, and/or changes in the VG (QRST-integral) vector, ΔVG. We studied vectorcardiograms (VCGs) synthesized from the ECGs of 84 patients who underwent elective PTCA. Mean ± SD balloon occlusion times were 260 ± 76 s. ECG ischemia diagnosis (STE or non-STE (NSTE), and the differences ΔST and ΔVG with the baseline ECG were measured after 3 min. of occlusion. Results. Linear regression of ΔVG on ΔST yielded ΔVG = 324 · ΔST (r = 0.85; P <; 0.0001, ΔST in mV). With ΔST thresholds of 0.025, 0.050, 0.075 and 0.100 m V and corresponding ΔVG thresholds of 8.1, 16.2, 24.3 or 32.4 m V·ms, respectively, we determined the sensitivity for ischemia detection, that varied from 55% for the STE criterion to 87 or even 99% for the one but most and the most sensitive ΔST and ΔVG criteria, respectively. Conclusion. Differential diagnosis by ΔST and ΔVG (requiring an earlier made non-ischemic baseline ECG) could dramatically improve ECG guided detection of patients who urgently require catheter intervention.