PTCA acutely expands perfused myocardial mass and increases flow homogeneity

Summary

In absence of collaterals, coronary stenosis produces a pressure drop in the microcirculation which might compromise capillary pressure and physiological blood—tissue exchanges. The present study tests the hypothesis that a derecruitment of vascular units occurs in the post-stenosis territory to maintain capillary pressure constant and that the restoration of a normal distal coronary pressure by PTCA is able to recruit additional myocardium to perfusion. Nine patients with single left coronary vessel disease, no previous myocardial infarct and normal ventricular function, were studied in a single session, before and after successful PTCA and stenting. Flow entering the stenotic vessel (CBF = ml/min, by Doppler catheter and quantitative angiography), and flow per gram of myocardium downstream the stenosis (MBF = ml/min/g of tissue, by the analysis of radioactive Xenon wash-out curves) were simultaneously measured. Perfused tissue was calculated as CBF/MBF and heterogeneity of flow distribution as the ratio between high and low flow sub-compartments estimated by bi-exponential analysis of Xenon curves. Distal coronary pressure was assessed by pressure wire. Heterogeneity of perfusion was also assessed in the remote region perfused by the angio-graphically normal left coronary branch. Distal coronary pressure during balloon occlusion was 21 ± 10 mmHg. PTCA increased CBF following i.e. adenosine from 19.8 ± 16.1 to 48 ± 27 ml/min, coronary flow reserve from 1.5 ± 0.2 to 2.3 ± 0.8 (p < 0.01) and distal coronary pressure from 68 ± 9 to 99 ± 8 at rest, and from 54 ± 10 to 99 ± 10 mmHg during adenosine. Perfused myocardial volume at rest increased from 27 ± 21 to 39 ± 8 g. A strict correlation was found between the increase in distal coronary pressure and the increase in perfused volume after PTCA (r = 0.79, p < 0.001). Flow homogeneity significantly increased following PTCA to the level of the remote region. In conclusion severe coronary stenosis contracts the amount of normally perfused myocardium likely to preserve capillary pressure and flow reserve in the residual perfused vascular units. PTCA expands perfused volume and decreases flow heterogeneity, according to the increase in distal coronary pressure.