Computer-assisted evaluation of dipyridamole thallium-201 SPECT in patients with aortic stenosis

Dipyridamole SPECT detects significant coronary artery disease (CAD) in patients without aortic stenosis. This study was done to establish normal 201Tl distribution limits in patients with aortic stenosis and to apply these normal limits to patients with aortic stenosis and angiographically significant CAD (> or = 75% area reduction).

Fifty-two patients (mean age 68 yr; mean valve area 0.67 cm2) were examined with 201Tl SPECT after dipyridamole infusion (0.56 mg/kg during 4 min). After tomographic reconstruction, basal, mid-ventricular and apical short-axis slices were selected. The highest activity in each six-degree segment was normalized to the maximal activity of each slice.

Significant CAD was found in 24 patients. Five patients without CAD, but with localized hypokinesia or left bundle-branch block, were excluded from the reference group which finally consisted of 16 patients. Sensitivity for CAD was 88% when the lowest relative activity in each segment was used as the lower limit of normal. With -2 s.d. and -2.5 s.d. curves the sensitivity was 83% and 75%, respectively. Gender-specific limits were not used. Nonsignificant CAD was found in seven patients (< 75% stenoses).

This study presents the normal distribution of 201Tl uptake for patients with aortic stenosis, using dipyridamole SPECT. The range method had the highest sensitivity for detection of significant CAD.