Abstract of papers to be Presented at the 29th Annual Scientific Session of the American College of Cardiology Houston, Texas, March 9 to 13, 1980

Specificity, sensitivity and accuracy of the nitroglycerin ventriculogram as a predictor of surgically reversible wall motion abnormalities

Recognizing patients with coronary artery disease in whom severe left ventricular dysfunction is attributed to a chronic decrease in myocardial blood flow without infarction is often difficult but important because such patients may benefit from surgical revascularization. Herein we describe a patient with severe left ventricular dysfunction who had appreciable resting wall motion abnormalities; tomographic thallium-201 myocardial scintigraphy performed while the patient was resting identified viable myocardium. Subsequent revascularization improved regional and global left ventricular function considerably.

The hibernating myocardium refers to resting LV dysfunction due to reduced coronary blood flow that can be partially or completely reversed by myocardial revascularization and/or by reducing myocardial oxygen demand. It is different from the stunned myocardium. Methods for its detection are not yet perfect. Hibernating myocardium has been demonstrated to be present in several clinical subgroups of patients; however, currently its full clinical presence and impact are not adequately defined.

Patients who have a decreased left ventricular (LV) ejection fraction (EF) may be denied coronary bypass grafting (CABG) because it is assumed that improvement in function is unlikely. If the low LVEF were due to myocardial necrosis, this assumption would be valid. If the dysfunction were due to both necrosis and ischemia, however, then improvement may be possible with CABG. A method capable of identifying such patients would be useful. In this study, an “ischemic index” was determined for 37 patients based on the difference between the presurgical LVEF estimated from the standard 12-lead electrocardiogram by the Selvester QRS score (indicating the extent of dysfunction due to necrosis) and the presurgical LVEF measured from resting multigated radionuclide angiography (indicating dysfunction due to both necrosis and ischemia). It was hypothesized that a high ischemia index, that is, a large discrepancy between estimated and measured LVEF, would be associated with an improved postsurgical measured LVEF. The results showed that patients with an ischemic index of ≤0 had a mean decrease in LVEF of 8% (p = 0.02) and those with an index between 0 and 10 had no mean change. Patients with an index ≥11, however, had a mean increase of 5% (p = 0.02), suggesting that depressed LVEF may improve following CABG among patients whose low function is due primarily to reversible ischemia as indicated by a high ischemic index.

Except for hibernating myocardium, other manifestations of silent ischemia appear to be favorably affected by the usual therapeutic approaches to patients with suspected or documented coronary heart disease. However, it appears that in severe stable angina and unstable angina pharmacologic therapy may not be effective in controlling all or nearly all episodes of silent ischemia. There is no data to determine indications for or efficacy of therapy directed primarily at silent ischemia. Although elimination of silent ischemia would seem to be a desirable goal, there are no data to support that it can be achieved or that it is a clinically practical approach to treatment of patients.