AJP - Heart and Circulatory Physiology, Vol 251, Issue 4 774-H778, Copyright © 1986 by American Physiological Society
Origin of atrial coving in canine phasic coronary artery blood flow
P. A. McHale and J. C. Greenfield Jr
The transient decrease in left circumflex coronary artery blood flow during
atrial contraction (atrial coves) was examined in open-chest, heart-blocked
dogs. Prominent atrial coves were observed in left circumflex flow during
both diastole and systole as a result of the asynchrony of atrial and
ventricular contractions. In eight open-chest dogs, atrial contractions
decreased diastolic circumflex coronary flow by 0.016 +/- 0.002 ml and
systolic flow by 0.014 +/- 0.001 ml compared with diastolic and systolic
intervals during which no atrial contractions occurred. The diastolic and
systolic flow reductions in this vessel were not significantly different (P
greater than 0.14). In five of the eight dogs no diastolic atrial coves
were observed in left anterior descending coronary flow, and only minimal
diastolic coving was present in the remaining three dogs; no systolic coves
were present in this vessel in any of the eight dogs. In five additional
open-chest dogs, brief inflation of a balloon in the left atrium produced
elevations of left ventricular diastolic pressure comparable to those
produced by atrial contraction. Only minimal atrial coves were associated
with these balloon inflations. These data are consistent with the
hypothesis that atrial contraction limits flow through the atrial blood
vessels and results in a transient decrease in flow in the atrial arteries
that arise from the left circumflex coronary artery. Although increases in
ventricular diastolic pressure may be partially responsible for the
appearance of atrial coves in the left circumflex coronary artery,
mechanical contraction of the atrial musculature appears to be of
significant importance.
