Coronary zero flow pressure and intramyocardial pressure in transiently arrested heart.

Study objective – The aim of the study was to examine the relation between zero flow pressure and intramyocardial pressure in the inner and outer layers of the myocardium.Design – Zero flow pressure was obtained in maximally vasodilated excised hearts by decreasing perfusion pressure (at 2 mm Hg·s−1) during transient heart arrest. Intramyocardial pressures in inner and outer myocardium were measured simultaneously with needle tip pressure transducers at depths of 8.0(SD 2.6) and 3.3(1.2) mm from the epicardium respectively. Ventricular and atrial pressure could be controlled at will.Experimental material – The excised hearts of eight mongrel dogs, body weight 14.0(0.8) kg, were used.Measurements and main results – During left ventricular pressure elevation (0, 15, 30 mm Hg), zero flow pressures were 9.1(2.4), 13.8(2.2), and 19.1(5.1) mm Hg, respectively. Corresponding values of intramyocardial pressure at the outer myocardium were in good agreement with the zero flow pressures, at 9.1(3.4), 13.4(2.8), and 20.8(5.4) mm Hg. Values at the inner myocardium increased from 7.4(2.4) to 18.9(8.6) and 32.9(13.0) mm Hg. The latter two values were significantly higher than the corresponding values of zero flow pressure and intramyocardial pressure at the outer myocardium (p<0.05, p<0.01). In isotransmural pressure elevation, the three pressures increased almost equally.Conclusions – The results show that zero flow pressure is strongly affected by intramyocardial tissue pressure, and if uneven intramyocardial pressure distribution is present the value of zero flow pressure depends on the lower values of intramyocardial pressure. [ABSTRACT FROM PUBLISHER]