AJP - Heart and Circulatory Physiology, Vol 253, Issue 2 317-H324, Copyright © 1987 by American Physiological Society
Coronary input impedance during cardiac cycle as determined by impulse response method
G. A. Van Huis, P. Sipkema and N. Westerhof
The coronary arterial system was characterized by its input impedance
determined in systole and diastole from impulse response functions in five
dogs. The impulse response technique was verified on a known hydraulic
system. A second confirmation was obtained on the circumflex artery:
reflected pulses were correlated with site of reflections generated by
occlusions. The impulse response indicates discrete reflections,
superimposed on the tail of the response, resulting from diffuse
reflections. Input impedance was calculated from Fourier analysis of the
impulse response. Characteristic impedance was 1.0 +/- 0.2 X 10(9) Pa X s X
m-3 (0.13 +/- 0.02 mmHg X ml-1 X min) and impedance at 0 Hz was 2.6 +/- 0.8
X 10(9) Pa X s X m-3. No significant differences between systole and
diastole were found in both characteristic impedance and impedance at 0 Hz.
It is concluded that the coronary system consists of a proximal part that
can be described with the three-element windkessel and a distal part not
seen by oscillatory pressure or flow perturbations, which depends on the
phase of cardiac contraction.
