How to assess the immediate results of PTCA. Should we use pressure gradient, flow reserve or minimal luminal cross-sectional area?

Abstract

Intracoronary blood flow velocity measurements with a Doppler probe, and the radiographic assessment of myocardial perfusion with contrast media have previously been used to investigate regional coronary flow reserve. We have applied both techniques in the same patients to measure the immediate improvement in coronary flow reserve as a result of angioplasty. In a group of 13 consecutive patients with a single proximal stenosis, coronary flow reserve was measured pre- and post-angioplasty by digital subtraction cineangiography, while Doppler measurements before and after papaverine were obtained pre- and post-angioplasty in the proximal part of the stenotic vessel. As a result of the angioplasty, coronary flow reserve measured with the radiographic technique (mean ± s.d.) increased from 1.1. ± 0.4 to 2.2 ± 0.4 (p < 0.001), while coronary flow reserve measured with the Doppler probe (mean ± s.d.) increased from 1.2 ± 0.3 to 2.4 ± 0.4 (p < 0.001). Pharmacologically induced hyperemia measured with the radiographic technique and with the Doppler probe were linearly related (r = 0.91 with an SEE = 0.3); this excellent relation confirmed the reliability of the intracoronary measurements. Using these two independent techniques coronary flow reserve immediately after angioplasty was found to be substantially improved but still abnormal. In a more recent study, we selected 18 patients without angina and with normal exercise thallium scintigraphy 5 months after successful percutaneous transluminal coronary angioplasty. We compared their coronary flow reserve with the flow reserve of 24 patients with angiographically normal coronary arteries, to establish whether angioplasty can restore coronary flow reserve of atherosclerotic coronary arteries to a normal level. We studied the quantitative cineangiographic changes and the concomitant alterations in coronary flow reserve resulting from angioplasty, as well as the subsequent changes 5 months later. Coronary flow reserve was measured with digital subtraction cineangiography. Angioplasty resulted in an increase in minimal obstruction area (mean ± s.d.) from 1.0 ± 0.5 to 3.6 ± 0.8 mm2 and in coronary reserve (mean ± s.d.) from 1.0 ± 0.3 to 2.5 ± 0.6 immediately following angioplasty. Five months later, a substantial and significant (p < 0.05) late increase in obstruction area (4.3 ± 1.4 mm2) and flow reserve (3.8 ± 1.1) had occurred. In 72% of our patients coronary flow reserve was restored to normal, 5 months after angioplasty.