INVIVO OBSERVATION OF SUBENDOCARDIAL MICROVESSELS OF THE BEATING PORCINE HEART USING A NEEDLE-PROBE VIDEOMICROSCOPE WITH A CCD CAMERA

We developed a portable needle-probe videomicroscope with a charge-coupled device (CCD) camera to visualize the subendocardial microcirculation. In 12 open-chest anesthetized pigs, the sheathed needle probe with a doughnut-shaped balloon and a microtube for flushing away the intervening blood was introduced into the left ventricle through an incision in the left atrial appendage via the mitral valve. Images of the subendocardial microcirculation of the beating heart magnified by 200 or 400 on a 15-in. monitor were obtained. The phasic diameter change in subendocardial arterioles during cardiac cycle was from 114+/-46 mum (mean+/-SD) in end diastole to 84+/-26 mum in end systole (p<0.001, n=13, ratio of change=24%) and that in venules from 134+/-60 mum to 109+/-45 mum (p<0.001, n=15, ratio of change=17%). In contrast, the diameter of subepicardial arterioles was almost unchanged (2% decrease, n=5, p<0.01), and the venular diameter increased by 19% (n=8, p<0.001) from end diastole to end systole. Partial kinking and/or pinching of vessels was observed in some segments of subendocardial arterioles and venules. The percentage of systolic decrease in the diameter from diastole in the larger (>100 mum) subendocardial arterioles and venules was greater than smaller (50-100 mum) vessels (both p<0.05). In conclusion, using a newly developed microscope system, we were able to observe the subendocardial vessels in diastole and systole. The vascular compression by cardiac contraction decreased the diameters of subendocardial arterioles and venules by about 20%, whereas subepicardial arterial diameter changed very little during the cardiac cycle and subepicardial venules increased in diameter during systole.