Ischemic and viable myocardium in patients with non-Q-wave or Q-wave myocardial infarction and left ventricular dysfunction: a clinical study using positron emission tomography, echocardiography, and electrocardiography.

OBJECTIVES

We investigated whether patients with non-Q-wave myocardial infarction (NQMI) have more ischemic viable myocardium (IVM) than patients with Q-wave myocardial infarction (QMI).

BACKGROUND

Non-Q-wave myocardial infarction is associated with higher incidences of cardiac events than QMI, suggesting more myocardium at risk in NQMI.

METHODS

To identify myocardial ischemia, hibernation, and scar, the resting and stress (82)rubidium perfusion and F-18 fluorodeoxyglucose metabolic positron emission tomographic imaging (PET) was performed in 64 consecutive patients with NQMI (n = 21) or QMI (n = 43). Echocardiography was performed for assessment of left ventricular function and wall motion index (WMI). The relationships between PET, echocardiographic, and electrocardiographic findings were analyzed.

RESULTS

There were no significant differences in left ventricular ejection fraction (LVEF) between NQMI and QMI groups (28 +/- 10% vs. 25 +/- 11%, p > 0.05). Ischemic and viable myocardium was more common in NQMI than in QMI (91% vs. 61%, p < 0.05). The total amount of IVM was significantly higher in NQMI than in QMI (6.5 +/- 5.2 vs. 2.9 +/- 2.8 segments, p < 0.001). Neither the number of Q waves, residual ST-segment depression of >or=0.5 mm or elevation of >or=1 mm, nor LVEF and WMI were significant predictors for IVM. Wall motion index correlated with scar segments (r = 0.54, p < 0.001) and LVEF (r = -0.67, p < 0.001).

CONCLUSIONS

Ischemic and viable myocardium is common in patients with NQMI and left ventricular dysfunction, suggesting that aggressive approaches should be taken to salvage the myocardium at risk in such patients.