Changes in myocardial perfusion reserve after PTCA: Noninvasive assessment with positron tomography

The effect of percutaneous transluminal coronary angioplasty (PTCA) on myocardial perfusion reserve has not been previously determined. Accordingly, 11 patients underwent positron imaging with [¹³N]ammonia or ⁸²Rb at rest and following dipyridamole + handgrip stress before and after PTCA. The ratio of stress to rest activity (S:R) was determined for each region of interest. Relative myocardial perfusion reserve by positron tomography (RMPR) was calculated by dividing S:R of the stenotic area by a corresponding value from a normal reference area of the same patient. Automated quantitative coronary arteriography was used to objectively measure the percent diameter (%D) and the percent area narrowing (%A) of the stenoses. In nine patients with successful PTCA, %D and %A improved (68 ± 10 to 49 ± 15% and 92 ± 3 to 72 ± 5%) and RMPR increased from 0.79 ± 0.07 to 0.96 ± 0.05. In the two patients in whom PTCA was unsuccessful, RMPR was unchanged. Changes in RMPR correlated inversely with changes in %D (r=-0.68) and %A (r=-0.92) and directly with improved coronary flow reserve derived from all stenosis measurements (r=0.73, p<0.001 for each). This study suggests that dipyridamole + handgrip stress imaging with PET can be used to assess changes in myocardial perfusion reserve before and after PTCA with the potential for determining restenosis noninvasively.