Directionality and proportionality of the ST and ventricular gradient difference vectors during acute ischemia

作者：ter Haar C Cato; Maan Arie C; Schalij Martin J; Swenne Cees A^*

来源：Journal of Electrocardiology, 2014, 47(4): 500-504.

DOI：10.1016/j.jelectrocard.2014.03.008

• Acute coronary syndrome
• ECG
• Ischemia
• ST amplitude
• Ventricular gradient

Background: The ECG is important in diagnosis and triage in the initial phase of the acute coronary syndrome (ACS). The primary goal of making an ECG at first medical contact should be the reliable detection of cardiac ischemia, thus facilitating a correct triage by corroborating the diagnosis of ACS. Ischemia detection by ST amplitude analysis is limited to situations in which there is an identifiable J point. The ventricular gradient (VG) is independent of conduction and might be an alternative ECG-based variable for ischemia detection.
Methods: We studied vectorcardiograms (VCGs) synthesized of the ECGs of 67 patients who underwent elective PTCA with prolonged balloon occlusions (mean +/- SD occlusion duration 214 +/- 77 s), and computed, during occlusions, the changes of the ST and VG vectors with respect to baseline, Delta ST and Delta VG, and the angle between these vectors, angle(Delta ST, Delta VG). We then analyzed directionality and proportionality of Delta ST and Delta VG by performing linear regressions of angle(Delta ST, Delta VG) on time after occlusion, and of Delta VG on Delta ST, respectively.
Results: Linear regression of angle(Delta ST, Delta VG) on time after occlusion yielded a slope of 1.55*10(-3) degrees/s and an intercept of 11.96 degrees; r(2) < 0.001 (NS). Linear regression of Delta VG on Delta ST on all data yielded a slope of 253 mV and an intercept of 14.4 mV.ms; r(2) = 0.75 (P < 0.001). Broken stick linear regression (breakpoint Delta ST = 0.255 mV) yielded slopes of 330 mV and 160 mV, intercepts of 5.6 mV.ms and 47.2 mV.ms, and r(2) values of 0.66 (P < 0.001) and 0.63 (P < 0.001) for the smaller and larger Delta ST values, respectively.
Conclusion: Our study suggests that, because of the directionality and proportionality between Delta ST and Delta VG, the change in the ventricular gradient, Delta VG, between a reference ECG and an ischemic ECG is a meaningful measure of ischemia.

• 出版日期2014-8