Phasic blood flow velocity pattern in epimyocardial microvessels in the beating canine left ventricle.

Abstract

We quantitated phasic epimyocardial microcirculatory coronary blood flow velocity patterns in the beating left ventricle. Using a newly developed floating objective and high-speed cinematography, red cell velocities in small arterioles, capillaries, and small venules and microvascular diameters in the superficial layer of the epimyocardium of beating left ventricle were determined throughout the entire cardiac cycle in open-chest anesthetized dogs. Heart rate was maintained at 140 beats/min by means of left atrial pacing. Peak red cell velocity was observed in midsystole in small arterioles and capillaries, and in late systole in small venules. Abrupt decline in red cell velocity and, in many cases, a momentary cessation or reverse of flow, was observed in these microvessels during the pre-ejection period. The internal diameter of small venule was increased in late systole, while that of small arteriole remained almost constant during the cardiac cycle. Furthermore, in these epimyocardial microvessels, a higher percentage of the total area under the velocity curve occurred during the ejection phase; 51% in small arterioles, 43% in capillaries, and 40% in small venules. These findings indicate that the phasic blood flow pattern is markedly different in the subepimyocardial microvessels from that in the large epicardial artery and the septal artery. During vasodilation following dilazep (50 micrograms/kg, i.v.), an adenosine potentiator, red cell velocity increased throughout the entire cardiac cycle in epimyocardial microvessels with significant increases in the total area under the velocity curves accompanied by significant dilation of the arterioles. The present data will provide information useful in predicting or simulating transmural differences in the phasic blood flow pattern.

Effects of Low Doses of Endothelin-1 on Basal Vascular Tone and Autoregulatory Vasodilation in Canine Coronary Microcirculation in Vivo

“…[22][23][24] Previous reports from our laboratory have demonstrated that the reactivity of observed vessels to various vasoactive substances or to physiological stimuli is well preserved in this preparation. 11,18,20,25,26 In the present study, the vasodilation of arterial microvessels was also clearly demonstrated when the perfusion pressure was reduced, indicating that the reactivity of the observed vessels was well preserved. The diameters of coronary arterial microvessels at the baseline and at perfusion pressures of 60 mmHg (mild stenosis) and 40 mmHg (severe stenosis).…”

“…[18][19][20] Briefly, a floating objective consists of a pair of convex lenses aligned on a common optical axis, and this apparatus transmits the real image of the epimyocardium of the beating heart to a fixed position without any change in magnification. The convex lens facing the heart can move in unison with the cardiac motion without touching the cardiac surface.…”

Hypercholesterolemia Impairs Transduction of Vasodilator Signals Derived From Ischemic Myocardium

“…3,13 With this system, the surface of the beating heart can be continuously observed throughout the cardiac cycle. An objective lifter was used to carefully adjust the distance between the objective and microvessels, so as not to compress the detector microvessel.…”

“…4,5,13,14 Briefly, the dogs were anesthetized and ventilated. A thoracotomy was performed, and the pericardium was cut to expose the heart surface.…”

Depside salts from Salvia miltiorrhiza improve myocardial microperfusion in rats using laser Doppler flowmetry

“…Although the cardioprotec-tive property of MLB has been studied extensively, as well as those of S miltiorrhiza depside salts, there is still no report concerning their effect on coronary microcirculation. To our knowledge, we demonstrated here for the first time that S miltiorrhiza depside salts could improve myocardial microperfusion using laser Doppler flowmetry, as well as CO. A number of strategies have been previously employed to optimize the laser Doppler system to overcome movement artifacts so that it can be used for myocardial microvascular measurement [13][14][15][16][17][18][19] . In the present study, we proposed that the probe was satisfactorily positioned when a distinct and regular waveform pattern was observed during baseline measurements and was altered following intervention, as suggested by Klassen et al [15] .…”