D. S. Berman

New approach to interpretation of technetium-99m pyrophosphate scintigraphy in detection of acute myocardial infarction: Clinical assessment of diagnostic accuracy

A modified classification for interpreting technetium-99m pyrophosphate scintigrams defines the 2+ diffuse pattern of tracer uptake as equlvocal rather than positive for acute myocardial infarction. Results of scintigraphy using this classification were compared with results of standard diagnostic tests for myocardial infarction in 235 patients admitted to a coronary care unit with acute chest pain. Of 81 patients with acute transmural infarction by standard clinical, electrocardiographic and serum enzyme criteria, 76 had a positive, 5 an equivocal and none a negative scintigram. Of 18 with acute nontransmural infarction by standard criteria, 7 had a positive, 9 an equivocal and 2 a negative scintigram. This it was uncommon for a patient with acute myocardial infarction, transmural or nontransmural, to have a definitely negative technetium-99m pyrophosphate study. Ten patients had equivocal evidence of infarction by standard criteria. Of the remaining 126 patients with no evidence of acute myocardial infarction by standard criteria, 87 had a negative, 35 an equivocal and 4 a definitely positive scintigram. Thus the definitely positive scintigraphic pattern was relatively highly specific for acute myocardial infarction. If the 2+ pattern had been considered positive, the specificity of the technique would have been greatly decreased. Computer processing strengthened observer certainty of the visual impression but changed the scintigraphic evaluation in only eight cases. Thus, use of an equivocal pattern renders technetium-99m pyrophosphate imaging both an extremely sensitive and specific method for detecting acute myocardial infarction.

Radionuclide assessment of nitroglycerin influence on abnormal left ventricular segmental contraction in patients with coronary heart disease.

Noninvasive gated cardiac blood pool imaging with technetium-99m autologous erythrocytes was employed to differentiate reversible versus irreversible abnormal ventricular segmental contraction by regional wall and pump responses to sublingual nitroglycerin in 25 patients with chronic coronary heart disease. In 12 patients without ECG infarctions compared to 13 with infarctions, radioisotopic images demonstrated significantly greater percent decreases in end-systolic volumes (33.8 ± 6.7 SEM VS 18.7 ± 4.4; P ⩽ 0.05) without differences in percent reductions in end-diastolic volumes (13.7 ± 3.9 vs 11.6 ± 6.1; NS) and thereby significantly greater percent increases in ejection fractions (9.3 ± 1.6 vs 4.1 ± 2.0; P ⩽ 0.05). In the 22 patients with regional dyssynergy, improvement in disordered pattern and extent of localized dyssynergy following antianginal action of nitroglycerin was related to ECG absence of prior infarction. These observations demonstrate the clinical accuracy of atraumatic scintigraphy in the detection of reversible localized dyssynergy due to myocardial ischemia in coronary heart disease.

Noninvasive detection of regional myocardial ischemia using rubidium-81 and the scintillation camera: comparison with stress electrocardiography in patients with arteriographically documented coronary stenosis.

The sensitivity of rest and stress myocardial perfusion studies using scintillation camera imaging of intravenously administered rubidium-81 (81Rb) in the detection of myocardial ischemia was compared to that of stress electrocardiography by relating results in 40 patients to the degree of stenosis delineated by coronary arteriography. Of 33 patients with greater than 75% stenosis of at least one of the three major coronary vessels (significant stenosis), rest and stress 8lRb imaging detected ventricular ischemia in 29 (88%), whereas simultaneous stress electrocardiography was positive (1 mm or greater horizontal ST-segment depression) in only 19 (58%) of the same patients. Five of the 29 patients who developed stress-induced scintigraphic evidence of ischemia did not develop angina or a positive electrocardiogram with stress. In 31 of the 33 patients with significant coronary stenosis, either the stress scintigram or the stress electrocardiogram was positive. In seven patients with less than 50% narrowing of a major coronary vessel on coronary arteriography, the stress scintigrams were negative, whereas the stress electrocardiograms were positive in the two of these patients with the syndrome of angina with normal coronary arteriograms. It is concluded that high resolution images of the myocardium can be obtained with 81Rb using the scintillation camera with special shielding, and that rest and stress 81Rb scintigraphy appears to provide greater sensitivity and specificity when compared to stress electrocardiography in the noninvasive identification of significant coronary stenosis.

Problem of diffuse cardiac uptake of technetium-99m pyrophosphate in the diagnosis of acute myocardial infarction: Enhanced scintigraphic accuracy by computerized selective blood pool subtraction

Abstract Because considerable controversy attends the interpretation of the diffuse uptake pattern of technetium-99m pyrophosphate scintigraphy, a practical computerized method for selective subtraction of the cardiac blood pool from these equivocal technetium-99m pyrophosphate scintigrams is described. The technique employs injection of a readily available radiopharmaceutical (technetium-99m pertechnetate) and standard computer software. The subtraction process allows subclassification of the equivocal scintigrams into two groups: one with definite myocardial localization of radioactivity, and the other without evidence of myocardial labeling. The clinical utility of this selective subtraction technique was assessed in 35 patients with equivocal pyrophosphate scintigrams and in an additional 13 patients with probably abnormal scintigrams by comparing the results of the subtraction scintigraphy with the final clinical diagnosis based on history, serial electrocardiograms and serial cardiospecific serum enzyme determinations. The results demonstrated that the subclassification based on computerized selective blood pool subtraction is clinically useful: If definite myocardial localization is demonstrated after subtraction, acute infarction is likely, whereas, if no myocardial localization is evident after subtraction, acute infarction is highly unlikely. Therefore, the addition of this simple selective blood pool subtraction technique to standard pyrophosphate imaging has been found to improve the overall effectiveness of pyrophosphate scintigraphy in the detection of acute myocardial infarction.

Clinical study of Tc-99m pyrophosphate scintigraphy in exercise-induced ventricular ischemia: Validation of technetium pyrophosphate specificity in myocardial infarction

Tc-99m pyrophosphate (PYP) localizes in acute myocardial infarctions; however, the critical question of whether ischemia (I) can cause abnormal PYP localization remains unanswered. Rest (R) and exercise PYP scintigraphy was performed in 15 patients (pts) with arteriography documented multivessel coronary disease (>75% stenoses). All 15 pts had exertional angina and treadmill ECG for I. In 11/15 R and exercise Rb-81 scintigraphy was also performed: all 11 had Rb-81 evidence of I with exercise. Multiple images were obtained 2 hours after intravenous injection of PYP using a scintillation camera with high resolution collimator. For exercise PYP studies, injection was made after exercise onset of chest pain and ECG evidence of I on treadmill. No evidence of + myocardial PYP activity after exercise compared to R was seen in 14/15. In contrast, definite + myocardial activity on the exercise PYP study occurred in one pt. In this pt particularly severe angina on exercise was associated with transient ST elevations on ECG. Although there was no serial ECG evidence of infarction, there was a rise in serum CPK and repeat resting PYP scintigraphy was positive 3 days after exercise, suggesting that small subendocardial infarction rather than transient ischemia had been produced. These results demonstrate that transient I is not sufficient to cause myocardial localization of PYP. Thus unlike exercise Rb-81 scintigraphy, exercise scintigraphy with PYP cannot be used in screening for coronary ischemia but, instead, is specific for recent myocardial necrosis.