Effect of coronary sinus occlusion on coronary flow, resistance, and zero flow pressure during maximum vasodilatation...

The effects of coronary sinus occlusion on the relation between coronary artery pressure and flow during maximum vasodilatation were studied in seven swine. The left anterior descending (LAD) coronary artery was instrumented with two catheters, a hydraulic occluder, and a flowprobe. Mean flow was measured at a series of pressures produced by partial LAD occlusion during maximum vasodilatation induced by an intracoronary infusion of adenosine. Observations were made under control conditions and during occlusion of the coronary sinus produced by inflating the balloon on the catheter positioned in the coronary sinus. Systemic haemodynamic variables did not change significantly after the coronary sinus was occluded. The mean right atrial pressure was 4 mmHg. At any given LAD perfusion pressure mean flow during coronary sinus occlusion was always less than during the control state: at LAD pressure 30 mmHg, control flow was 53 ml.min-1 vs occluded flow 24 ml.min-1; at LAD pressure 40 mmHg, control flow 79 ml.min-1 vs occluded flow 49 ml.min-1; and at LAD pressure 50 mmHg, control flow 105 ml.min-1 vs occluded flow 74 ml.min-1; p less than 0.001 for all comparisons. The mean (SD) LAD pressure at which flow stopped (Pzf) when the coronary sinus was unobstructed was 10(2) mmHg. The Pzf during occlusion of the coronary sinus was significantly higher at 20(4) mmHg (p less than 0.001). The slopes of the mean pressure-flow relations were not significantly different during the control state (2.62(0.65) ml.min-1 per mmHg) vs the occluded state (2.47(0.63) ml.min-1 per mmHg), indicating no change in vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)