Difference vectors to describe dynamics of the ST segment and the ventricular gradient in acute ischemia

Background: The ECG is important in the diagnosis and triage of the acute coronary syndrome (ACS), especially in the hyperacute phase, the "golden hours," during which myocardial salvage possibilities are largest. An important triaging decision to be taken is whether or not a patient requires primary PCI, for which, as mentioned in the guidelines, the presence of an ST elevation (STE) pattern in the ECG is a major criterion. However, preexisting non-zero ST amplitudes (diagnostic, but also non-diagnostic) can obscure or even preclude this diagnosis. Methods: In this study, we investigated the potential diagnostic possibilities of ischemia detection by means of changes in the ST vector, Delta ST, and changes in the VG (QRST integral) vector, Delta VG. We studied the vectorcardiograms (VCGs) synthesized of the ECGs of 84 patients who underwent elective PTCA. Mean +/- SD balloon occlusion times were 260 +/- 76 s. The ECG ischemia diagnosis (ST elevation, STE, or non-ST-elevation, NSTE), magnitudes and orientations of the ST and VG vectors, and the differences Delta ST and Delta VG with the baseline ECG were measured after 3 min of balloon occlusion. Results: Planar angles between the Delta ST and Delta VG vectors were 14.9 +/- 14.0 degrees. Linear regression of Delta VG on Delta ST yielded Delta VG = 324. Delta ST (r = 0.85; P < 0.0001, Delta ST in mV). We adopted Delta ST > 0.05 mV, and the corresponding Delta VG > 16.2 mV.ms as ischemia thresholds. The classical criteria characterized the ECGs of 46/84 (55%) patients after 3 min of occlusion as STE ECGs. Combined application of the Delta ST and Delta VG criteria identified 73/84 (87%) of the patients as ischemic. Conclusion: Differential diagnosis by Delta ST and Delta VG (requiring an earlier made non-ischemic baseline ECG) could dramatically improve ECG guided detection of patients who urgently require catheter intervention. (C) 2013 Elsevier Inc. All rights reserved.