Atrial pacing and thallium‐201 scintigraphy in patients with chest pain: Correlation with coronary anatomy

Atrial pacing and thallium‐201 scintigraphy were performed in 72 patients referred for evaluation of chest pain. Coronary artery disease (CAD) was present in 63 patients, as documented by cardiac catheterization performed at the same time or within 2 months of atrial pacing. Nine patients had no or insignificant (< 50% stenosis) CAD. The sensitivity of pacing‐induced angina for CAD was 51%, and was 49% for ST depression. Specificities were 89% and 78%, respectively. A reversible perfusion defect was seen in 54% of patients with CAD (specificity 89%), and a fixed defect in 29% (specificity 100%). The sensitivity of an abnormal thallium‐201 scan (one or more reversible or fixed defects) was 79% (p < 0.05 compared to angina or ST depression). Combined sensitivity of ST depression and/or an abnormal thallium‐201 scan was 87%. There were no significant changes in any of these sensitivities as the number of vessels with CAD increased. Thallium‐201 scintigraphy correctly identified 11 of 19 (58%) patients with single‐vessel disease as having CAD in only one vessel, but underestimated the extent of disease in all but a few patients with multivessel disease. The sensitivity of perfusion imaging to identify lesions in specific vessels ranged from 27% (circumflex) to 57% (right coronary artery). Specificities were 100% for circumflex, 78% for anterior descending, and 83% for right coronary artery lesions. The sensitivity of a reversible defect or an abnormal thallium‐201 scan did not change significantly as the degree of stenosis in the vessel perfusing a myocardial segment increased, nor did it differ between lesions involving the proximal or nonproximal segments of a vessel. Fixed perfusion defects were significantly more frequent in segments perfused by occluded vessels than those with subtotal stenoses. Addition of thallium‐201 scintigraphy to the atrial pacing test increases sensitivity for detection of CAD. The test is limited, however, in its ability to define the extent or severity of CAD, or to identify specific vessels with CAD.