Epicardial Coronary Artery Compliance in the Dog

Abstract

The dynamic compliance of 21 coronary arteries from 17 dogs was determined in situ. Intramyocardial portion* were occluded with a mixture of 200(1 glass beads and liquid silicone. To simulate in vivo pressure-volume conditions, 0.1 ml of saline was injected in 150 to 240 msec at a rate of 30 pulses/min. Silicone casts of the vessels, made at 100 mm Hg distending pressure, were used as a reference volume. The results indicate that the dynamic compliance decreases as the initial distending pressure rises. The change in volume for a 50 mm Hg pressure increment (initial distending pressure of 100 mm Hg) was 3.7 ± 0.6% (mean±SE). In four dogs, phasic flow in the left circumflex coronary artery was measured. The volume of systolic flow per beat during the control state was of the same order of magnitude as the compliance of the vessels; however, during reactive hyperemia, systolic coronary flow markedly exceeded the dynamic compliance of the coronary vessels. In six dogs the static compliance of a segment of coronary artery was obtained radiographically. A 30.1 ± 1. 4% change in volume occurred when the intravascular pressure was increased from 70 to 120 mm Hg.ADDITIONAL KEY WORDS coronary artery coronary artery elasticity pressure-radius relation• The pressure-volume relationships of the epicardial coronary arterial tree have not been previously described. These data are necessary to formulate any realistic dynamic model of the coronary circulation. For example, to determine the degree to which the myocardium is perfused during systole, the compliance of the epicardial coronary vessels must be known (1). Accordingly, this study was designed to determine the dynamic pressure-volume relationships, of the in situ epicardial coronary arteries in the dog and to relate these measurements to volumes of these vessels obtained from casts. These data were com- This work was supported by U. S. Public Health Service Research Grant HE-09711 and by Training Grant HE-05736, from the National Heart and Lung Institute.Received June 29, 1970; accepted for publication October 2, 1970. pared to values of phasic coronary artery blood flow obtained in vivo. In addition, static pressure-volume measurements of an epicardial segment of the left coronary artery were obtained radiographically. MethodsSeventeen mongrel dogs weighing 12 to 30 kg were killed rapidly with pentobarbital. The left circumflex coronary artery and aortic blood flows in four of these dogs had previously been measured as described below. The hearts were excised and placed in a pan of saline at room temperature. The aortic and pulmonary arteries were cut away within 1 cm of the semilunar valves and the hearts weighed. The left coronary artery was dissected from its origin for 3 mm. A 5-cm segment of high pressure, noncompliant catheter having a flame-flanged distal tip was inserted into the coronary ostia and secured with a ligature. Care was taken not to disturb the remainder of the coronary vascular bed. This technique was used to cannulate the main left coro...

Alpha Adrenergic Vasoconstriction and Nitroglycerin Vasodilation of Large Coronary Arteries in the Conscious Dog

“…6). Allowing for an inner diameter to wall thickness ratio of -8-10, this Einc estimate is slightly lower than that implied by the modulus of volume distensibility reported by Patel and Janicki (19), which in turn is lower than the Cv values reported by Douglas and Greenfield (18). Our representative Ein, is an order of magnitude lower than the Einc reported by Cox (23).…”

“…The pulsatile change observed from diastole to systole in the coronary diameter phasic waveform averaged 9% of the mean diameter, a value higher than predicted from experiments in anesthetized preparations (18,19). Late in diastole there were downward deflections in the coronary diameter waveform coincident with atrial systole and isovolumic ventricular systole.…”

Phasic coronary blood flow velocity in intramural and epicardial coronary arteries.

“…Douglas and Greenfield (1970) found the epicardial capacitance function to be large enough to account for normal systolic stroke flow, but not of sufficient magnitude to account for systolic stroke flow during vasodilation. Other investigators have found the epicardial vessels to be very compliant, two to three times that of similarly sized systemic arteries (Arts et al, 1979), suggesting potential capacitive effects.…”

“…Because the epicardial arteries function in part as capacitors (Douglas and Greenfield, 1970), the phasic flow pattern in an epicardial coronary artery may not accurately reflect the phasic pattern of myocardial perfusion. Eckstein and his colleagues, in 1962, theorized that capacitance of epicardial arteries may distort the actual myocardial perfusion in three ways: (1) the magnitude of retrograde flow during systole is concealed because blood expelled from the deep myocardial layers distends the vessels and is not measured; (2) the antegrade systolic flow that is measured is, in part, a capacitance flow that distends the epicardial arteries; and (3) the measured antegrade diastolic flow is less than the actual perfusion since the epicardial capacitor would be discharging at this time.…”

Pulsatile blood flow in the entire coronary arterial tree: theory and experiment

“…Previous studies (4,12) have investigated the dynamic elastic properties of canine coronary artery. In the current study, the ratio of E dyn/Estat (4) is used to adjust the dependence of Young's modulus on frequency.…”