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 <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 <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.Occlusion of the coronary sinus resulted in a decrease in coronary flow at any given LAD perfusion pressure during maximum vasodilatation. This was due entirely to an increase in the pressure at which flow stopped without a change in coronary vascular resistance or right atrial pressure. The increase in Pzf was probably due to an increase in extravascular pressure affecting mainly the venous system or to an intrinsically higher zero flow pressure in the extracoronary sinus drainage pathways.
- Coronary artery pressure-flow relation
- Coronary vessels
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)