Determination of the site, extent, and significance of regional ventricular dysfunction during acute myocardial infarction

Nuclear Cardiology: Present and Future

Nuclear cardiology has made significant advances since the first reports of planar scintigraphy for the evaluation of left ventricular perfusion and function. While the current "state of the art" of gated myocardial perfusion single-photon emission computed tomographic (SPECT) imaging offers invaluable diagnostic and prognostic information for the evaluation of patients with suspected or known coronary artery disease (CAD), advances in the cellular and molecular biology of the cardiovascular system have helped to usher in a new modality in nuclear cardiology, namely, molecular imaging. In this review, we will discuss the current state of the art in nuclear cardiology, which includes SPECT and positron emission tomographic evaluation of myocardial perfusion, evaluation of left ventricular function by gated myocardial perfusion SPECT and gated blood pool SPECT, and the evaluation of myocardial viability with PET and SPECT methods. In addition, we will discuss the future of nuclear cardiology and the role that molecular imaging will play in the early detection of CAD at the level of the vulnerable plaque, the evaluation of cardiac remodeling, and monitoring of important new therapies including gene therapy and stem cell therapy.

Cardioprotective effect of unstable angina prior to acute anterior myocardial infarction

To evaluate the difference in the process of left ventricular functional recovery after successful percutaneous transluminal coronary angioplasty (PTCA), 25 patients with sudden onset of acute Q wave anterior myocardial infarction (MI [group 1]) and 28 patients with unstable angina prior to MI (group 2) were investigated in the late hospital phase. The circumferential extent of left ventricular dysfunction was significantly larger in group 1 than in group 2. The left ventricular ejection fraction (EF) and the ratio of systemic arterial systolic blood pressure to left ventricular end-systolic volume (P/V ratio) were significantly lower in group 1 compared with group 2. The P/V ratio had nonlinear relationships with left ventricular end-diastolic volume (LVEDV) in both groups and the P/V ratio in group 1 was significantly lower than those in group 2 at any given LVEDV. Thus, in patients with successful PTCA, unstable angina prior to acute MI had better left ventricular pump function in the course of left ventricular remodeling.

Detection and quantification of acute, isolated myocardial infarction by two dimensional echocardiography

Ninety consecutive patients with acute, isolated myocardial infarction were evaluated with two dimensional echocardiography. Satisfactory echocardiograms were obtained in 66 patients (73 percent). All patients were studied 2 to 12 hours after the onset of symptoms. Sixty patients had additional studies at 48 and 72 hours. Long axis views were obtained at the base, body and apex of the left ventricle. Five short axis views of the left ventricle were obtained at different levels from the cardiac base to the apex. The individual short axis views, corrected for the end-diastolic internal diameter of the left ventricle, were divided into equal segments and the area of asynergy in each view was estimated. Infarct localization was similar on electrocardiography and echocardiography in 62 of 66 patients. In two dimensional echocardiography in one patient. The results of an echocardiographic study in one patient were false negative. During the study period the individual asynergic area remained stable. The initial asynergic area correlated well (r = 0.87, p less than 0.01) with the peak value of the isoenzyme of creatine kinase (CK-MB), which occurred hours later. Thus, two dimensional echocardiography is a reliable method to localize and quantify, early after the onset of symptoms, the eventual extent of myocardial involvement in patients with acute, isolated infarction.

Regional left ventricular function in acute myocardial infarction: evaluation with quantitative radionuclide ventriculography

Regional and global left ventricular performance was noninvasively assessed with quantitative gated equilibrium radionuclide ventriculography in 43 patients an average of 40 hours after the onset of a first acute transmural myocardial infarction. In all 16 patients with anterior infarction, regional ejection fraction, a quantitative measure of regional left ventricular performance, was uniformly depressed in the infarcted zone. In patients with inferior infarction the abnormalities of regional performance were less severe. Fourteen of 20 patients (70 percent) with inferior infarction had depressed performance in the infarcted zone. Function in noninfarcted zones was abnormal in only 6 of the 20 patients (30 percent) with inferior infarction, but it was abnormal in 11 of the 16 patients (69 percent) with anterior infarction, particularly in those with severe pump failure. As a consequence, global left ventricular ejection fraction was significantly lower in patients with anterior than in those with inferior infarction (mean +/- standard error of the mean 31 +/- 3 percent versus 51 +/- 3 percent, less than 0.005). Prognosis and clinical functional class were related to performance not only in infarcted zones, but also in noninfarcted zones as assessed with electrocardiography. It is concluded that depressed function in apparently noninfarcted left ventricular zones contributes significantly to left ventricular dysfunction after acute myocardial infarction, particularly in patients with anterior infarction.