Detection and quantification of previous myocardial infarction by exercise-redistribution tomographic thallium-201 scintigraphy

Prevalence, characteristics, and risk stratification of electrocardiographic and symptomatic silence of myocardial ischemia despite scintigraphically evidenced ischemia in symptomatic patients presenting with severe coronary artery stenosis

Symptoms of angina pectoris and transient ST-segment depression are most commonly used to evidence acute myocardial ischemia during exercise testing. However, the diagnostic accuracy of either or both criteria in relation to clinical characteristics and the patient's exercise response has been a subject of controversy. The prevalence and severity of symptoms of angina pectoris and/or ST-segment depression were studied prospectively in 147 consecutive patients with a history of daily angina pectoris, scintigraphic evidence of exercise-induced myocardial ischemia, and coronary artery stenosis > 75%. Logistic regression analysis was applied to determine absence of any or both criteria by the clinical characteristics or exercise response of the patient. During exercise testing, ST-segment response failed to prove scintigraphically evidenced myocardial ischemia in 14/147 patients (10%) and 35/147 patients (24%) when ST-segment depression > or = 0.1 in either > or = 1 or > or = 2 ECG leads was chosen. Symptoms of angina pectoris were found to be absent in 69/147 patients (47%). Only 58 patients (40%) suffered from angina and met the ECG criterion at the time of scintigraphic myocardial ischemia. Absence of ST-segment depression was best predicted by clinical variables such as large myocardial infarction (increase: 2.6 times, p = 0.007), number of stenoses < or = 2 (2.0 times, p = 0.023), and presence of diabetes mellitus (4.3 times, p = 0.035). Painless myocardial ischemia was determined by blood response to exercising. Thus, a double product > 23 increased the risk of painless myocardial ischemia by 1.5 times (p = 0.017).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the distribution of myocardial blood flow between exercise-induced and hyperventilation-induced attacks of coronary spasm: a study with thallium-201 myocardial scintigraphy

Exercise and hyperventilation tests are often used as the provocative tests for coronary artery spasm. To examine the distribution of myocardial blood flow during exercise-induced and hyperventilation-induced attacks of coronary spasm, thallium-201 myocardial scintigraphy was performed in 47 patients with variant angina. The extent and severity scores and severity index (severity score/extent score) of scintigraphic perfusion defect were calculated. In 32 patients, anginal attack associated with ST elevation on the electrocardiogram was induced by exercise; in 23 patients, the attack was induced by hyperventilation. In patients with either anterior or inferior wall ischemia, both the extent and severity scores and severity index in the scintigram were significantly greater in exercise-induced anginal attack than those in hyperventilation-induced attack. In patients with simultaneous anterior and inferior wall ischemia, they tended to be greater in exercise-induced attack. In eight patients in whom anginal attack was induced by both exercise and hyperventilation, these scores and index were significantly greater in exercise-induced attack than those in hyperventilation-induced attack. These data suggest that myocardial ischemia during exercise-induced attack is enhanced as compared with that during hyperventilation-induced attack. Thallium-201 scintigraphy combined with exercise testing seems to be more sensitive for detecting myocardial ischemia induced by coronary spasm.

Quantitative exercise thallium-201 rotational tomography for evaluation of patients with prior myocardial infarction

The utility of stress-redistribution thallium-201 myocardial perfusion single-photon emission computed tomography (SPECT) in patients with a prior single myocardial infarction was studied in 66 patients who were tested by both SPECT and coronary angiography. SPECT was quantified by comparing the patients' circumferential count profiles to a previously established normal data base and by plotting the results onto a polar coordinate map that localized defects to the 3 major coronary artery territories. The pattern of reversibility of the quantitatively detected defects was assessed by consensus visual analysis. SPECT thallium-201 detected myocardial infarction in 62 of 66 patients (sensitivity = 94%). Sixty-five percent of the infarct zones showed some reversibility at 4-hour imaging which corresponded with angiographic evidence of flow to the infarct zones in 95.5% of cases. Late (18 to 24 hours) imaging, done in 26 patients, showed complete or partial reversibility of 29% of infarct zone segments which were nonreversible on 4-hour images. To improve specificity for detection of disease in coronary arteries supplying the non-infarct territories, new quantitative criteria were developed that took into consideration contiguity of defects with the infarct zone. Accuracy for detection of patients with multivessel coronary disease by quantitative thallium-201 SPECT was 86%, which was significantly higher than those of the clinical response to exercise (48%), the exercise electrocardiographic response (56%) or their combination (65%).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiographic diagnosis of remote posterior wall myocardial infarction using unipolar posterior lead V9

The accuracy of four electrocardiographic criteria for diagnosing remote posterior myocardial infarction was assessed prospectively in 369 patients undergoing exercise treadmill testing with thallium scintigraphy. Criteria included the following: 1) R-wave width greater than or equal to 0.04 s and R-wave greater than or equal to S-wave in V1; 2) R-wave greater than or equal to S-wave in V2; 3) T-wave voltage in V2 minus V6 greater than or equal to 0.38 mV (T-wave index); 4) Q-wave greater than or equal to 0.04 s in left paraspinal lead V9. Twenty-seven patients (7.3 percent) met thallium criteria for posterior myocardial infarction, defined as a persistent perfusion defect in the posterobase of the left ventricle. Sensitivities for the four criteria ranged from 4 to 56 percent, and specificities ranged from 64 to 99 percent. Posterior paraspinal lead V9 provided the best overall predictive accuracy (94 percent), positive predictive value (58 percent), and ability to differentiate patients with and without posterior myocardial infarction of any single criterion (p less than .0001). Combining the T-wave index with lead V9 further enhanced the diagnostic yield: the sensitivity for detecting posterior infarction by at least one of these criteria was 78 percent, and when both criteria were positive, specificity was 98.5 percent. It is concluded that a single, unipolar posterior lead in the V9 position is superior to standard 12-lead electrocardiographic criteria in diagnosing remote posterior myocardial infarction, and that combining V9 with the T-wave index maximizes the diagnostic yield.

Quantification of myocardial ischemia and infarction with single photon emission computed tomography

To evaluate the feasibility of 201Tl single photon emission computed tomography (SPECT) for quantitative detection of myocardial infarction and ischemia, scintigraphic studies were related to angiographic findings. In study A infarct sizes with SPECT were compared with the angiographic infarct sizes of 30 patients. A linear correlation was found for the % infarct of the left ventricular circumference between both methods (r = 0.73; P less than 0.001; mean infarct size 20.7% +/- 10.5% (angio) vs 19.8% +/- 12.9% (SPECT), mean +/- SD). Furthermore, a significant inverse correlation between scintigraphic infarct size and left ventricular ejection fraction (r = -0.87, P less than 0.001) was obtained. In study B exercise/rest 201Tl SPECT was used for quantification of myocardial ischemia. Forty-three patients underwent both stress 201Tl SPECT and biplane exercise left ventriculography. Ischemia was expressed as % defect size of the left ventricular circumference. Sensitivity and specificity for detection of ischemia were 96% and 100% respectively with stress SPECT. Extent of myocardial ischemia correlated significantly with both methods (r = 0.63; SPECT defect = 1.0 angiographic ischemia +2%; P less than 0.001). The regression followed the line of identity and the mean sizes of ischemia were identical (SPECT 12.2 +/- 7.6% vs 14.6 +/- 12.4% ventriculography, mean +/- SD) demonstrating the agreement of both methods. However, there was some intraindividual variance between the scintigraphic and the angiographic study. The sensitivity and specificity in single regions with SPECT were lower compared to the global test results.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation of global and regional left ventricular function to tomographic thallium-201 myocardial perfusion in patients with prior myocardial infarction

To determine the relation between regional myocardial perfusion and regional wall motion in humans, tomographic thallium-201 imaging and two-dimensional echocardiography at rest were performed on the same day in 83 patients 4 to 12 weeks after myocardial infarction. Myocardial perfusion and wall motion were assessed independently in five left ventricular regions (total 415 regions). Regional myocardial perfusion was quantitated as a percent of the region infarcted (range 0 to 100%) using a previously validated method. Wall motion was graded on a four point scale as 1 = normal (n = 266 regions), 2 = hypokinesia (n = 64), 3 = akinesia (n = 70), 4 = dyskinesia (n = 13) or not evaluable (n = 2). Regional wall motion correlated directly with the severity of the perfusion deficit (r = 0.68, p less than 0.0001). Among normally contracting regions, the mean perfusion defect score was only 2 +/- 4. Increasingly severe wall motion abnormalities were associated with larger perfusion defect scores (hypokinesia = 6 +/- 5, akinesia = 11 +/- 7 and dyskinesia = 18 +/- 5, all p less than 0.01 versus normal. Among regions with normal wall motion, only 3% had a perfusion defect score greater than or equal to 10. Conversely, among 68 regions with a large (greater than or equal to 10) perfusion defect, only 13% had normal motion whereas 87% had abnormal wall motion. The relation between perfusion and wall motion noted for the entire cohort was also present in subgroups of patients with anterior or inferior infarction. In patients with prior myocardial infarction, the severity of the tomographic thallium perfusion defect correlates directly with echocardiographically defined wall motion abnormalities, both globally and regionally.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of myocardial perfusion and function by single photon emission computed tomography

Although planar radionuclide techniques provide accurate, noninvasive measurements of myocardial perfusion and function that are of proven clinical value in the evaluation of the cardiac patient, they are limited by poor object contrast and superimposition of surrounding structures. Due to incomplete angular sampling and significant longitudinal distortion, limited angle tomography did not solve these problems. Single photon emission computed tomography (SPECT) can acquire scintillation information over very small angles of rotation and, thus, improve both object contrast and delineation of overlying or adjacent structures without distortion. The early SPECT systems were cumbersome, dependent on individual user developed software, and had extremely long acquisition and processing time. Improved camera design, new software algorithms, and the use of array processors have simplified and standardized quality control, decreased processing time, and minimized the number of user interventions. New image display formats and quantitative methods of analysis have made interpretation less cumbersome, more reliable and highly reproducible. Cardiac SPECT has been used with thallium-201 and gated blood pool imaging in both research and clinical applications and shown an improvement over planar methods of acquisition.