Prognostic value of exercise radionuclide angiography in a population-based cohort of patients with known or suspected coronary artery disease

Dipyridamole administration at the end of an insufficient exercise Tc-99m MIBI SPECT improves detection of multivessel coronary artery disease in patients with previous myocardial infarction

To demonstrate that the administration of dipyridamole at the end of an insufficient maximal subjective exercise test can improve the diagnostic accuracy of single-photon emission computed tomography in patients with previous myocardial infarction, 209 consecutive patients were studied with technetium-99m methoxyisobutyl isonitrile single-photon emission computed tomography and coronary angiography. Patients were divided in 3 groups: group 1, 107 patients with sufficient exercise testing; group 2, 55 patients with insufficient exercise testing; group 3, 47 patients with insufficient exercise testing in whom intravenous dipyridamole (0.56 mg/kg over 4 minutes) was administered at the end of exercise. In groups 1 and 3 the sensitivity values for the diagnosis of multivessel disease were significantly higher (80% and 76%, respectively) than those in group 2 (59% [p = 0.009 and p = 0.02, respectively]). Specificity and predictive values were not different among the 3 groups. Thus, in patients with previous infarction in whom adequate levels of exercise could not be achieved, dipyridamole administration at the end of exercise significantly increased the sensitivity for diagnosing multivessel disease.

Prognostic value of exercise thallium-201 imaging in a community population

BACKGROUND

The prognostic value of exercise thallium-201 imaging has been well established in referral patient populations at tertiary care centers, but these results may be influenced by referral bias.

METHODS

This study was performed to evaluate the prognostic value of thallium imaging in a community-based population of 446 residents of Olmsted County, Minn. Eleven variables were prospectively selected and tested for their associations with outcome end points.

RESULTS

Four variables (age, history of myocardial infarction, number of abnormal thallium segments on the postexercise images, and increased thallium lung uptake) contained the most independent prognostic information. For the end point overall mortality rate, the multivariate chi-square values were 17.2 (p < 0.0001) for age and 20.9 (p < 0.0001) for the number of abnormal thallium segments on the postexercise images. Five-year survival rate for patients older than the median age of 59 years with an abnormal scan was 84% versus 97% for patients < or = 59 years of age with a normal scan.

CONCLUSION

Exercise thallium imaging was useful for prognostic purposes in this relatively low-risk community population, confirming the findings of referral population studies.

Worsening left ventricular performance on serial exercise radionuclide angiography does not identify high-risk patients

OBJECTIVE

To determine whether worsening exercise performance on serial exercise radionuclide angiography identifies patients at increased risk of future cardiac events.

MATERIAL AND METHODS

One hundred nine medically treated patients with previous Q-wave myocardial infarction underwent two exercise radionuclide angiographic studies at least 6 months apart (median, 16 months) without an intervening clinical event. Worsening exercise performance between the two studies was defined by five criteria: (1) lower (5% or more) peak exercise ejection fraction; (2) worsening peak exercise wall motion score; (3) combination of criteria 1 and 2; (4) worsening serial delta (exercise - rest) ejection fraction; or (5) increasing exercise ST-segment depression of 1 mm or more. Patients were followed up for a median duration of 3.9 years after the second exercise study.

RESULTS

Five cardiac deaths and 10 nonfatal myocardial infarctions occurred during follow-up. A Cox proportional hazards analysis failed to show an association between any of the aforementioned variables and cardiac events. Of the 15 patients with cardiac events, 4 (27%) had a lower (5% or more) exercise ejection fraction and 2 (13%) had a worsening exercise wall motion score. Of the 94 patients without cardiac events, 37 (39%) had a lower (5% or more) exercise ejection fraction and 28 (30%) had a worsening serial exercise wall motion score (not a statistically significant difference).

CONCLUSION

Worsening exercise performance on serial exercise radionuclide angiography does not identify patients at increased risk of future cardiac events.

Usefulness of the lymphocyte concentration as a prognostic marker in coronary artery disease

The prognostic utility of the relative lymphocyte concentration was tested in a population-based study of chronic coronary artery disease. This inexpensive, readily available test was found to be significantly related to survival (p = 0.03) in 211 patients followed for a mean of 45 months.

Simultaneous dipyridamole/maximal subjective exercise with 99mTc-MIBI SPECT: improved diagnostic yield in coronary artery disease

OBJECTIVES

We attempted to demonstrate that simultaneous dipyridamole administration and maximal subjective exercise in patients who are unable to achieve a good exercise level can improve the diagnostic efficacy of technetium-99m methoxy isobutyl isonitrile (99mTc-MIBI) myocardial single-photon emission computed tomography (SPECT).

BACKGROUND

The results of myocardial perfusion scintigraphy are unsatisfactory if the level of exercise achieved by the patient is insufficient. The use of dipyridamole with maximal subjective stress testing has been shown to improve the quality of the thallium-201 myocardial perfusion images, but there are no studies demonstrating that this combination improves the diagnostic accuracy of myocardial perfusion SPECT.

METHODS

Two hundred thirty-one consecutive patients, without a previous myocardial infarction, were classified into three groups: group 1, 91 patients with an adequate exercise test; group 2, 68 patients with an inadequate exercise test; group 3, 72 patients with an inadequate exercise test who then received intravenous dipyridamole (0.56 mg/kg body weight over 4 min) simultaneously with exercise.

RESULTS

Results for sensitivity (89%) and negative predictive value (83%) in group 3 were significantly better than those in group 2 (71% [p = 0.03] and 56% [p = 0.002], respectively) and not significantly different from those in group 1. The polar maps of 20 patients studied with an without dipyridamole at the same exercise level revealed a significantly greater extent of ischemia in each territory and in a global assessment (19 + 20% vs. 8 + 11%, p < 0.0001) when dipyridamole was administered during physical exercise.

CONCLUSIONS

Intravenous dipyridamole administration during exercise testing is advisable in all patients who are unable to achieve an adequate exercise level. This approach permits physicians to avoid missing ergometric information while optimizing myocardial SPECT results.

Role of nuclear cardiology for determining management of patients with stable coronary artery disease

Both radionuclide angiography and myocardial perfusion imaging provide important insights that determine the management of patients with stable coronary artery disease. Both nuclear cardiology procedures have clearly demonstrated use in the noninvasvie identification of severe (left main or three-vessel) coronary artery disease and the noninvasive assessment of prognosis and thereby determine which patients should be sent to coronary angiography. Both radionuclide angiography and myocardial perfusion imaging provide prognostic information that is independent of resting left ventricular function and coronary anatomy and thereby influence the decision regarding which patients should be sent to coronary revascularization. This review considers the evidence supporting the uses of these nuclear cardiology procedures and provides suggestions regarding their cost-effective application.