Regional distribution and extent of perfusion abnormalities, and the lung to heart uptake ratios during exercise thallium-201 SPECT imaging in patients with cardiac syndrome X

Abstract

Background: Cardiac syndrome X is defined as angina-like chest pain with transient ischemic ST-segment changes during exercise and angiographically normal epicardial coronary arteries. Studies with myocardial perfusion imaging in this syndrome have indicated that some patients, but not all, have an abnormality on perfusion scan. However, the impact of these perfusion abnormalities on pulmonary thallium uptake is not clear in this group of patients.

Objective: To evaluate the regional distribution and extent of perfusion abnormalities, and the lung to heart (L:H) uptake ratios using exercise thallium-201 single-photon emission computed tomography (TI-201 SPECT) in patients with cardiac syndrome X.

Methods: The study group consisted of 31 selected cardiac syndrome X patients with regional perfusion abnormalities during exercise TI-201 SPECT imaging. A control group included 26 healthy subjects with normal coronary angiograms, exercise testing and exercise TI-201 SPECT imaging. Exercise TI-201 SPECT results were analyzed with further estimation of the L:H ratios, number and localization of regional perfusion defects, and their mean extent scores expressed in pixels and in per cent of the left ventricular wall. Twenty-two patients with known coronary artery disease were also included in the analysis of the L:H ratios.

Results: Multiple perfusion defects were detected in 13 (42%) patients and perfusion defects of single localization were detected 18 (58%) patients. All patients had reversible perfusion abnormalities: 21 (67.7%) had anterior, 14 (45.2%) had inferior and 12 (38.7%) had lateral localization of perfusion defects. The analysis of the extent of the perfusion defects revealed that the mean scores of the extent of the single regional defects were 38.61+/-43.8 pixels and those of multiregional defects were 106.1+/-55.2 pixels, which corresponded to 6.05+/-1.8% and 16.6+/-5.4% of the left ventricular wall defects, respectively. Patients with cardiac syndrome X had a significantly higher L:H ratio during exercise than the healthy subjects (0.46+/-0.02 versus 0.34+/-0.03, P<0.01). In addition, L:H ratios were found to be higher in patients with multiple perfusion defects (0.50+/-0.02) than in patients who had only anterior (0.45+/-0.08) or inferior (0.43+/-0.02) perfusion defects (P<0.05 for both). There were no statistically significant differences in the rest L:H ratios between the study and control groups. Also, no significant differences were observed in exercise L:H ratios between the cardiac syndrome X patients and the patients with coronary artery disease (0.46+/-0.02 versus 0.49+/-0.03, P>0.05).

Conclusions: The results suggest that multiple perfusion defects in multiple vascular regions are relatively common in cardiac syndrome X patients, with the majority of these patients having at least one abnormal perfusion bed. Patients with this syndrome who have perfusion abnormalities also had significantly higher L:H ratios during exercise than did the control patients. Increased exercise L:H ratios were more prominent in patients with multiple perfusion defects.