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To evaluate the quantitative relationships between resting potassium-43 (43K) myocardial imaging and left ventricular segmental contraction abnormalities, 15 patients were studied by both radionuclide and contrast angiographic techniques at least two months following transmural myocardial infarction. The ECG location of infarction involved the anterior wall alone in six patients, inferior wall alone in three patients, both anterior and inferior walls in five patients, and in one patient ECG-anatomic correlation was obscured by newly developed left bundle branch block. 43K defects were noted in all patients. Anterior wall 43K defects were noted in all patients with previous anterior infarction and seven of nine inferior infarcts. These 43K defects were associated with a quantifiable decrease in regional radioactivity of at least 20% of normal appearing zones, and their location correlated with the angiographic site of akinesis or dyskinesis. The extent of the 43K defect (% 43K HP [% potassium 43 hypoperfusion]) was measured by planimetry and averaged 49% of the anterior view image (range 25-66%), 43% of the left anterior oblique image (range 0-58%), with the mean of both views being 47% (range 17-62%). The mean total area of the anterior image was 58 cm2 (range 40-101 cm2). The extent of the 43K defect (% 43K HP) was related to the extent of segmental contraction abnormality (% ACS). Correlations between % ACS and anterior view % 43K HP (r = 0.67), left anterior oblique % 43K HP (r = 0.54), and mean % 43K HP (r = 0.77) were found. The total size of the anterior view image correlated with left ventricular end-diastolic volume (r = 0.79). Thus, in this initial group of patients following transmural infarction, potassium-43 imaging can be accurately and quantitatively correlated with the site and extent of regional ventricular dysfunction as it is assessed by quantitative left ventricular angiography.

The emergence in the past 20 years of nuclear medicine as a distinct diagnostic discipline has been a major clinical advance. The relatively rapid evolution from the small laboratory limited primarily to the study of thyroid disease to the large unit in which radioactive tracers (radionuclides) are utilized to evaluate structure and function of most organ systems has been accelerated by major advances in instrumentation, new radioactive tracers and application of computer techniques. Application of these radionuclide techniques to the study of coronary artery disease has been quite recent, and has in part been limited by the need for a coordinated effort between the cardiologist and the specialist in nuclear medicine. However, realization of the potential usefulness of these techniques has fostered an increasingly productive liaison between the two specialties. The potential advantages of these radionuclides in evaluating patients with cardiovascular disease is twofold: first, they may permit the noninvasive or atraumatic acquisition of data that might otherwise be obtained only at the time of cardiac catheterization; second, and perhaps more important, they may permit the acquisition of physiologic measurements or observations not attainable by more conventional modes of study. Functionally, these techniques can be divided into those that evaluate cardiac performance and those that evaluate coronary blood flow, regional myocardial perfusion and myocardial viability.

The authors describe a miniature cadmium telluride (CdTe) detector module for continuous monitoring of ventricular function using an equilibrium radionuclide blood-pool label. The detector and collimator are small, light, and suitable for direct attachment to the chest wall. Clinical studies in 18 patients using a prototype system demonstrated reasonably good correlation with left-ventricular ejection fractions (LVEF) determined by first-pass studies performed with a multicrystal scintillation camera (r = 0.74) and gated equilibrium studies performed with a computerized sodium iodide (Nal) probe (r = 0.76). The CdTe device may prove to be useful in patients in intensive and coronary care units as well as in ambulatory patients.

The variability of left ventricular ejection fraction, normalized mean ejection rate and regional wall motion was evaluated from first pass quantitative radionuclide angiocardiograms obtained with a computerized multicrystal scintillation camera. Three radionuclide studies separated by an average of 4.3 days were obtained in each of 20 patients. Ejection fraction and ejection rate obtained on the first, second and third studies did not differ significantly. The mean (+/- standard deviation) variability of sequential ejection fraction measurement was 4.4 +/- 3.6 percent, and of sequential ejection rate was 0.56 +/- 0.47 sec(-1). Variations in measurements were not related to fluctuations in heart rate or blood pressure. Variability in ejection rate was significantly greater in patients with normal function than in those with abnormal function. Regional wall motion analysis was constant in 19 of 20 patients. Thus, sequential quantitative radionuclide angiocardiography allows reproducible serial assessment of left ventricular performance that can be performed with a low level of intrinsic variability.

The effect of patient positioning on thallium-201 images in the left lateral projection was evaluated in 28 patients. The left lateral image was performed with the patient on his right side (LLrs) and also supine (LLsup). False-positive inferoposterior defects were reported in five patients (18%) in the LLsup view, but not in the LLrs view. Image quality was better in the LLrs view. The false-positive results in the LLsup view may result from two factors: a) overlap of the left hemidiaphragm and myocardium; or b) changes in orientation of the heart in the two lateral positions. Therefore, thallium-201 images in the LL position should be performed with the patient lying on his right side.