Coronary hemodynamics in elasmobranchs and teleosts.

Until recently, direct measurements of coronary blood flow in fishes had not been made. This review presents and compares in vivo measurements of coronary flow recorded from the school shark, Galeorhinus australis, and the coho salmon, Oncorhynchus kisutch. In both species, the coronary blood flow was phasic and strongly influenced by the cardiac cycle. Coronary blood flow in the school shark was more severely compromised by the cardiac cycle with a short retrograde flow occurring during systole. In the coho salmon, there was an anterograde coronary blood flow throughout the cardiac cycle. Differences in coronary hemodynamics are discussed in relation to differences in the myoarchitecture of the school shark and coho salmon hearts. The regulation of coronary blood flow through changes in vascular resistance (vasoactivity of the coronary vessels) is also discussed.