Reduced collateral perfusion is a direct consequence of elevated right atrial pressure

Abstract

In the present study we determined quantitatively the effects of increased right atrial pressure (RAP) on coronary and collateral flows. In an isolated, blood-perfused, maximally vasodilated dog heart preparation in which the left ventricle was vented, we used the retrograde flow method to assess collateral flow. When RAP was elevated from 5 +/- 1 (control) to 13 +/- 1 and 23 +/- 1 mmHg, retrograde flow from the left circumflex coronary artery (which was open to atmospheric pressure) increased 29 +/- 8 and 97 +/- 21% relative to control while left anterior descending flow decreased 5 +/- 1 and 14 +/- 2%, respectively (P < 0.01; n = 7). The increase in retrograde flow could be due to 1) an increase in collateral flow due to increased pressure at the origin of the collaterals or 2) the elevated RAP (venous outflow pressure), which forces the antegrade collateral flow component in the retrograde direction. To distinguish between these possibilities we embolized the circumflex with 30-microns spheres to eliminate the antegrade flow component. After embolization there was no significant change in retrograde flow with elevated RAP, indicating that the second supposition was correct. We conclude that increased RAP 1) results in a reduction of flow to the collateral-dependent myocardium and 2) reduces perfusion of the unoccluded coronary vessel. Furthermore, we found that under conditions of varying venous outflow pressure, retrograde flow may not serve as a reliable index of collateral flow.

Acetaminophen and myocardial infarction in dogs

“…Neither of these two variables differed between the two groups of dogs under any condition. The coronary vasculature was viable and responsive in both groups (e.g., brisk hyperemic flow responses upon release of 15-s periods of inflow occlusion; data not shown) and in a physiological state in all regards [e.g., control, baseline values that are consistent with previous reports from our laboratory (27,30) and from other laboratories (20,26)]. Neither did nonspecific collateral coronary blood flow differ at any time interval in the two groups.…”

“…Coronary perfusion pressure was measured at the tip of the LAD cannula. We used a modification of the methods of Manor et al (26) and Scheel et al (40) to estimate nonspecific coronary collateral blood flow. To do this, the subclavian-to-LAD shunt was constructed of two segments of catheter in series (with the flow probe interposed between them).…”