Acute Anterior Transmural Myocardial Ischemia: DISCUSSION part 2

ST Segment

In dog models, the sum of ST elevations in multiple leads has correlated with the amount of myocardial ischemia and necrosis. There are conflict­ing clinical reports as to the relationship between ST elevation and the severity and extent of myocardial ischemia and infarction. In a previous angioplasty study, Cohen et al found that the acute ST elevations closely paralleled the development of new wall motion abnormalities on left ventriculography. In the 12 patients with LAD occlusion, ST elevations in all 12 leads as well as ST elevations in only one lead (lead V2) were highly correlated with percentage of LV hypocontractility (r= .096, r= .092, respectively). We also found a significant, although not as close, relation­ship between ST elevations and LV dysfunction. Important differences between the studies may be that while Cohen et al evaluated only LV systolic dysfunction and directly, by visualization of the LV, we evaluated LV systolic and diastolic dysfunction and indirectly, as manifested by increasing LV filling pres­sures. Our study patients were also different in having longer durations of ischemia and higher magnitudes of ST elevations.

Clinical Implications and Limitations

Our study examined the behavior of R- and S-wave amplitude changes in patients with acute anterior transmural myocardial ischemia. We found R-wave changes to be variable but generally upward and to be directly correlated with ST elevations, while S- wave changes were almost uniformly downward and inversely correlated. While the overall correlations with changes in PW were fair to poor, patients with the greatest increases in R waves or decreases in S waves tended to have the highest rises in PW. Evalu­ation of the specificity of these findings for the presence of transmural ischemia was beyond the scope of this study. As such, the possible value of examining R- or S-wave changes in situations where ST elevations are not diagnostic of ischemia, ie, left bundle branch block remains to be determined. viagra soft

We found that the magnitude of acute anterior ST elevations related to changes in LV filling pressures. Knowledge of such a relationship may have important clinical utility in patients with acute ischemic compli­cations during LAD angioplasty, in variant angina, and possibly in early presentations of anterior myocardial infarctions before the onset of necrosis and additional confounding variables.

Category: Disease

Tags: Myocardial Ischemia, ventricular filling

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