Analysis of digital subtraction coronary angiography for estimation of flow reserve in critical coronary stenosis.

ABSTRACT

To examine the accuracy of digital subtraction angiographic assessment of coronary flow reserve in critical coronary stenosis, time-density curves were obtained from digital angiograms for a myocardial region of interest. Time-to-peak contrast (TPC) and contrast washout rate (T) were measured in 11 patients with critical 1-vessel lesions before and after percutaneous transluminal coronary angioplasty (PTCA). Collectively, the values of TPC and T were significantly shortened, from 5.8 +/- 1.1 to 4.4 +/- 1.0 seconds (p less than 0.01) and from 11.3 +/- 4.0 to 5.2 +/- 1.2 seconds (p less than 0.001) after PTCA, respectively. All 11 patients except 1 showed shortened T after PTCA; however, in 5 of the 11 patients, TPC after PTCA had approximately the same values as those before PTCA. In experiments in dogs with critical circumflex stenosis, coronary flow and posterior wall thickening at rest were not different from control; however, contrast media-induced hyperemia was markedly attenuated, accompanied by a significant prolongation of T (7.7 +/- 4.5 vs 15.8 +/- 1.9 seconds, p less than 0.01) and completely unchanged TPC (both 6.8 seconds). With simultaneous tracings of coronary flow and time-density curves, TPC and the washout phase on the curve corresponded with contrast-induced transient flow reduction and hyperemic phases, respectively. It is concluded that T appears more sensitive than TPC when basal coronary flow is maintained to almost normal levels, as in patients with stable effort angina pectoris having critical coronary stenosis.