Analysis of coronary slosh phenomenon under coronary stenosis by measurement of blood flow or vasucular diameter in intramyocardial vessels and microvessels

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It is well known that myocardial ischemia is frequently observed in the subendocardial layer. Although several possible reasons have been claimed in relation to some characteristic differences between subendo- and subepi-cardial layers such as stress during systole, extravascular pressure, number density of blood vessels, and hematocrit, no conclusive reason is given yet. We have found that part of blood which flows into the subendocardial myocardium during diastole is forced to flow into the subepicardial artery by myocardial compression during systole and this reversed blood flow volume is an important determinant of transmural distribution. Prof. Feigl from University of Washington also predicted the possibility of blood transport from subendo- to subepi-cardial sides during systole. He then named this phenomenon "slosh" and has claimed its patho-physiological significance.The objectives of this study are (1) to examine the effect of vasodilating compounds and sympathetic nerve syst … More em on the blood transport (slosh) from subendo- to subepi-cardial sides by myocardial compression during systole and the change in this effect in the case of coronary artery stenosis and (2) to study if these compounds can allow uniform blood distribution (anti-slosh hypothesis). The blood flow in septal artery of anesthetized open-chest dog was measured using a 20 MHz ultrasound Doppler velocimeter, and the extent of "slosh" was evaluated as the ratio of forward to backward flows. The effect of "slosh" was augmented by an increase in coronary artery stenosis and by administrations of adenosine or nitroglycerin into a coronary artery. It was found that the stimulation of alpha-sympathetic nerve system led to an anti-slosh effect which was linearly associated with heart rate. We also observed coronary microvessels in the subendocardial myocardium using a needle-probe CCD microscope and found that the arterial diameter decreased about 20 % during systole. This decrease in arterial diameter is considered to cause the "slosh" phenomenon. Less