Coronary artery pressure development and wave transmission characteristics in the horse

Measurements of the pressure waveform development and the wave transmission characteristics in the left extramural coronary arteries of the horse have been carried out. Near the ostium the left coronary pressure waveforms are seen to be virtually identical to the corresponding aortic root waveforms; however, the present of low frequency, relatively large amplitude pressure oscillations (on the order of 5 to 10 Hz) gradually become the dominant diastolic feature as one proceeds distally from the left ostium, and these eventually completely mask the incisura. In a limited number of experiments, these oscillations have been simultaneously observed on both centerline velocity and phasic flow signals. These are felt to be primarily due to wave reflection phenomena, but may represent a combined effect of wave reflections and the natural oscillatory motion of the heart mass. Peak systolic pressures were found to remain relatively unchanged as one proceeds distally; however, the end-diastolic pressures were found to decrease steadily, thus giving rise to an increasing pulse pressure and a gradually decreasing mean pressure. Wave speeds in the coronary arteries were found to range between 4 and 11 m.s-1, and the data obtained indicate the wave speed to be highly dependent on both local intralumenal pressure and spatial location.