Changes in Myocardial Perfusion Reserve after PTCA: Noninvasive Assessment with Positron Tomography

Abstract

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]ammoniaor 82Rbat 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.

The clinical utility of assessing myocardial blood flow using positron emission tomography

“…There is more than 30 years of experience with this tracer that has been published in animal and human studies. 36 Unlike H 2 15 O and 13 NH 3 , 82 Rb is a generator product and it is widely available in the US, with increasing availability in Canada, and in several regions of Europe and Japan. It has a short physical half life of 76 s, enabling rapid serial imaging; enhancing patient throughput; and reducing radiation exposure when lower doses are used.…”