Evaluation of Successful PTCA by Transstenotic Flow Velocity Ratios

Abstract

Doppler probes mounted on the tip of a guidewire allow the measurement of coronary blood flow velocities, not only proximal but also distal to stenoses eligible for percutaneous transluminal coronary angioplasty (PTCA). The objective of this study was to determine the improvement of transstenotic Doppler flow velocity ratios following PTCA and to investigate the possible impact on restenosis during follow-up control angiography three months later. Doppler flow velocity measurements were performed in 29 patients with 29 stenoses eligible for PTCA. Results of PTCA were morphologically evaluated by computer-assisted quantitative coronary angiography (QCA) and measured hemodynamically by determining transstenotic Doppler flow velocity ratios. Successful PTCA according to QCA was present in all cases with a reduction of mean diameter stenosis from 66 +/- 8% to 35 +/- 7%. Resting spectral peak velocities and velocity integrals were markedly reduced distal to lesions (all P < 0.001), resulting in mean transstenotic flow velocity and velocity integral ratios of less than 0.60 prior to PTCA. Owing to endoluminal enlargement, significant improvement of transstenotic Doppler ratios was observed in mean ratios greater than 0.90 (all P < 0.0001). In patients with restenosis, transstenotic ratios following PTCA demonstrated a tendency to be smaller than in patients without restenosis. Transstenotic Doppler flow velocity ratios are diminished in severe coronary stenoses. Improvement of these ratios provides information on hemodynamic success of interventional procedures. Thus, the determination of intracoronary Doppler flow velocity ratios contributes, in addition to angiographic estimation, to the evaluation of stenoses severity and success of interventional procedures.

Poststenotic coronary blood flow following percutaneous transluminal coronary angioplasty

“…Other authors have demonstrated several pathomechanisms probably involved in poststenotic vasoconstriction after PTCA such as endothelium-dependent (Fischell et al 1989) or myogenic (Fischell et al 1990) response to sudden increases in pressure following PTCA, increased vasoreactivity to stimuli such as serotonin released from platelets adhering and aggregating at the PTCA-site (Zeiher et al 1991, Golino et al 1994, loss of flowmediated vasodilation (Cox et al 1989), alteration of coronary autoregulatory tone (Fischell et al 1990) and sympathetic reflex diffusely distributed to the coronary tree (Gregorini et al 1994). In contrast to poststenotic coronary diameter, poststenotic coronary Doppler flow velocity showed a highly significant increase after PTCA, as observed by us (Dill et al 1994, Altstidl et al 1995a, 1997b and other groups (Segal et al 1992, Ofili et al 1993a, Segal 1993, Serruyys et al 1993, Anderson et al 1993 before. Since poststenotic coronary artery vasoconstriction routinely occurs during PTCA (Fischell et al 1988, Altstidl et al 1997a, increase of poststenotic flow velocity may be due to both reduction in diameter stenosis and decrease in coronary diameter according to the continuity equation.…”

“…A recently developed 15 MHz Doppler transducer mounted on a 0.014 (0.036 cm) angioplasty guidewire provides the ability of measuring flow velocity parameters both in proximal and distal coronary arteries (Doucette et al 1992) and could easily be incorporated into clinical angioplasty procedures. Previous investigations using this Doppler guidewire (Dill et al 1994, Altstidl et al 1995a, 1997b, Ofili et al 1993a to measure pre-and poststenotic intracoronary flow velocities both prior to and following PTCA have demonstrated significant changes with a decreased distal blood flow velocity and a loss of diastolic predominant flow pattern, which are characteristic for significantly stenosed arteries, and normalization after successful intervention. Since poststenotic coronary artery vasoconstriction, for which several pathophysiological mechanisms (Zeiher et al 1991, Golino et al 1994, Fischell et al 1989, Gregorini et al 1994 have been discussed, occurs after PTCA (Fischell et al 1988, Anderson et al 1993, additional increase in coronary flow velocity according to the continuity equation may be observed.…”