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Thallium-201 uptake and clearance after dipyridamole infusion may differ from that after exercise stress because the hemodynamic effects of these two interventions are different. In this study of normal volunteers, thallium kinetics after dipyridamole (n = 13) were determined from three serial image sets (early, intermediate and delayed) and from serial blood samples and compared with thallium kinetics after exercise (n = 15). Absolute myocardial thallium uptake was greater after dipyridamole compared with exercise (p < 0.0001), although the relative myocardial distribution was similar.

Controversy has arisen concerning whether gender influences the prognosis after myocardial infarction. Although some studies have shown there to be no difference between the sexes, most have indicated a worse prognosis for women, attributing this to differences in baseline characteristics. It has been further suggested that black women have a particularly poor prognosis after infarction. To determine the contribution of gender and race to the course of infarction, 816 patients with confirmed myocardial infarction who were enrolled in the Multi-center Investigation of the Limitation of Infarct Size (MILIS) were analyzed. Of those patients, 226 were women and 590 were men, 142 were black and 674 were white.

To develop an approach to predicting adverse events after percutaneous transluminal coronary angioplasty (PTCA), 50 patients had thallium-201 exercise testing within 1 month after successful single vessel coronary angioplasty and were followed up for a mean of 18 months. Adverse events were: 1) clinical events consisting of recurrent angina (17 patients) and myocardial infarction (1 patient); 2) treatment events consisting of repeat coronary angioplasty (10 patients) and coronary bypass surgery (1 patient); and 3) restenosis, denned as a >30% increase in luminal stenosis (15 of 38 recatheterized patients). There were no deaths. Of the clinical, exercise, angiographic and thallium scan variables analyzed by stepwise logistic regression, postangioplasty gradient >20 mm Hg predicted clinical events and treatment events, and the number of segments with slower thallium clearance predicted clinical events, treatment events and restenosis. Using Cox Hazards model regression of survival without events, the number of transient qualitative thallium defects also predicted clinical events and restenosis.

To determine the utility of rest-injected technetium-99m methoxybutyl isonitrile (Tc-99m isonitrile) uptake as a marker of myocardial viability, the regional uptake of this agent was compared with regional wall motion by equilibrium gated blood pool scan in 26 patients with previous myocardial infarction and with postrevascularization uptake in 8 patients after coronary bypass surgery. Rest left ventricular Tc-99m isonitrile uptake was assessed qualitatively in three coronary vascular territories as grade 0 (markedly reduced) to grade 2 (normal), and quantitatively by circumferential profile analysis. Wall motion was scored qualitatively in corresponding vascular territories as normal, hypokinetic or akinetic/dyskinetic.

To determine the potential of planar technetium-99m methoxybutyl isonitrile myocardial imaging as a method of detecting totally occluded or severely stenosed coronary arteries, the regional distribution of technetium-99m isonitrile at rest was compared with the coronary anatomy in 38 patients with prior myocardial infarction who underwent coronary arteriography. Left ventricular technetium-99m isonitrile tracer uptake at rest was assessed in the three major coronary vascular territories.

Exercise thallium-201 perfusion scans and gated equilibrium blood pool scans were performed in 120 catheterized patients with a chest pain syndrome. Eighty-six patients had coronary artery disease and 34 patients did not. The effects of gender, propranolol, exercise level, exercise ischemia, history of typical angina, history of previous myocardial infarction, electrocardiographic Q waves, number of diseased vessels and extent of coronary artery obstruction on diagnostic accuracy were evaluated. The overall sensitivity and specificity of thallium scans were 76 and 68%, respectively, and those of gated blood pool scans 80 and 62% (p = not significant). Propranolol decreased the specificity of thallium scans (propranolol = 42%; no propranolol = 87%, p < 0.05). Thallium scans and anginal history were less sensitive for detecting coronary disease in women (men: thallium = 79%; angina = 77%; women: 54 and 46%, respectively; p < 0.05). Exercise level did not significantly affect the diagnostic accuracy of either scan.

A technique to measure left ventricular (LV) function and myocardial perfusion was validated in 12 dogs. 133Xe in saline was injected into the left atrium (LA) or LV and two data sets were obtained using gamma camera imaging: 1) A first pass gated scan for LV function; followed by 2) Sequential images for regional myocardial perfusion. LV ejection fraction and wall motion measurements from the 133Xe blood pool images were compared to ejection fraction (r=0.88, P<0.01) and wall motion (r=0.83, P<0.01) data from 99mTc labeled blood pool scans. The perfusion measurements obtained with the 133Xe method were compared to microsphere data (r=0.79, P<0.01). Measurements after LV 133Xe injection were similar to data following LA injection. Thus, quantitative assessment of global LV function, regional wall motion and myocardial perfusion is possible with LA or LV 133Xe injection and gamma camera imaging.

To determine if the myocardial clearance of omega 123I-16-hexadecanoic acid (123I-HDA) is affected by decreased coronary blood flow, six anesthetized dogs had partial occlusion of the left anterior descending coronary artery. One hour later, 113Sn-microspheres were injected into the left atrium, followed immediately by the IV administration of 123I-HDA. Following injection, regional myocardial 123I activities were monitored continuously with miniature cadmium telluride radiation detectors placed against the endocardium in both ischemic and nonischemic zones. After 3 h continuous monitoring, 46 Sc microspheres were injected into the left atrium and the dogs were killed. Ischemic and nonischemic areas of myocardium were sectioned and counted in a well counter.

Exercise-induced increases in pulmonary blood volume ratio have been shown to be a sensitive marker of coronary artery disease, and correlate well with exercise-induced increases in left ventricular filling pressure. To compare the impact of single vessel coronary disease on left ventricular systolic function (ejection fraction) versus diastolic filling pressure (pulmonary blood volume) before and after intervention, serial supine exercise gated blood pool scans were performed before and after coronary angioplasty in 32 patients with isolated left anterior descending coronary artery disease. By applying previously established criteria of abnormal ejection fraction (rest <50% or failure to rise by 5% with exercise) and pulmonary blood volume ratio (>1.06), 66% of the patients were found to have abnormal responses before angioplasty by ejection fraction compared with 81% abnormal responses by pulmonary blood volume ratio (p = 0.15). After angioplasty, the proportion of patients with abnormal ejection fraction (59%) was essentially unchanged, whereas only 38% continued to have an abnormal pulmonary blood volume ratio (p < 0.01 compared with before angioplasty). The mean pulmonary blood volume ratio also decreased significantly from 1.15 ± 0.10 before angioplasty to 1.02 ± 0.15 after angioplasty (p < 0.001).

Left ventricular end-systolic pressure-volume analysis was employed to assess the inotropic effect of the phosphodiesterase inhibitor enoximone (formerly MDL-17,043) in nine patients with severe heart failure (New York Heart Association class IV symptoms, mean ejection fraction = 0.22). Left ventricular pressure-volume loops were constructed using high fidelity left ventricular pressure measured with micromanometer-tipped catheters and simultaneous left ventricular volume obtained by gated blood pool imaging. Afterload was reduced with the vasodilator nitroprusside to generate the baseline left ventricular end-systolic pressure-volume relation, a relatively load-independent measure of contractile function.