Coronary angiographic rates after stress single-photon emission computed tomographic scintigraphy

There is speculation that coronary angiography may be overused for the assessment of coronary artery disease. Because of its proved ability to differentiate high- and low-risk subsets of patients with coronary artery disease, myocardial perfusion scintigraphy should be an effective strategy in patient selection for angiography. This retrospective clinical study analyzed the relation between scintigraphic findings and subsequent angiography.

Coronary angiographic rates were determined by following up on all stress single-photon emission computed tomographic (SPECT) myocardial perfusion studies performed in a cardiology practice nuclear laboratory during a 26-month interval. All patients were followed up for at least 3 months; mean follow-up was 8.9 months. Subsequent angiography was determined from catheterization laboratory logs, medical records, and telephone contact. Scintigraphic studies were graded according to presence or absence of reversible perfusion defects, affected coronary territories, and lung uptake of 201Tl. Scans were categorized high risk if more than two of the following three criteria were met: reversibility of left anterior descending or multivessel distributions or abnormal lung uptake of thallium. Of 4162 studies, 60% had reversible perfusion defects. Of such studies, 32% were followed up by angiography versus 3.5% without reversible defects. Among studies with reversible defects, the subsequent angiography rate was 60% for those showing high-risk reversibility, compared with 9% for all other studies demonstrating reversibility. Multivariate logistic regression identified high-risk reversibility (odds ratio 20.96) and any reversibility (odds ratio 8.22) as the strongest predictors of angiography. Other correlates of lesser statistical significance were angina and absence of prior infarction or coronary bypass.

In this large retrospective study, the results of SPECT scintigraphy overpowered all other clinical and treadmill characteristics in determining the likelihood of subsequent coronary angiography. Only rarely were patients categorized as relatively low risk by scintigraphy referred for angiography. As such, SPECT scintigraphy as used in a private practice, self-referral environment appears to be effective in stratifying potential candidates for coronary angiography.