Role of afterload in determining regional right ventricular performance during coronary underperfusion in dogs.

Abstract

SUMMARY. The relationship between coronary perfusion pressure and regional myocardial performance of the right ventricular free wall was studied, in the presence or absence of right ventricular hypertension in 13 open-chest dogs. The right coronary artery was perfused through a shunt from a carotid artery. Regional systolic shortening of the right ventricular free wall was measured by means of a sonomicrometric technique at various levels of coronary perfusion pressure. Regional shortening was insensitive to coronary perfusion pressure or flow when it was above 31 mm Hg or 0.27 ml/min per g. Once coronary perfusion was below this critical level, regional shortening in both base to apex and circumferential orientations decreased linearly, depending on the degree of perfusion pressure. Despite the presence of a monoexponential relationship between coronary perfusion pressure or flow and regional shortening, a direct linear relation between perfusion pressure and flow was consistently noted, with or without pulmonary artery banding, suggesting that there is limited autoregulation of right coronary flow. The critical perfusion pressure for maintaining regional myocardial function of the right ventricle was highly dependent on the level of right ventricular systolic pressure (r = 0.64 -0.72, P < 0.05). Thus, right ventricular systolic pressure was one of the important determinants of regional wall motion during coronary underperfusion. (Circ Res 57: 96-104, 1985) IN the left ventricle, severe coronary arterial stenosis reduces both coronary perfusion pressure and regional myocardial blood flow (Nakamura et al., 1973;Tomoike et al., 1977). This produces regional wall motion abnormalities (Wyatt et al., 1975;Nakamura et al., 1977; Koyanagi, 1979) and subsequent reductions in cardiac output if the ischemic zone is large enough (Lekven et al., 1973;Isoyama et al., 1983). The concept of critical flow below which regional contractile performance deteriorates in proportion to the reduction in perfusion has been documented repeatedly (Wyatt et al., 1975;Downey, 1976;Banka et al., 1977;Vatner, 1980;Weintraub et al., 1981). The critical level of perfusion pressure for maintaining normal regional wall motion in the left ventricle was about 40 to 60 mm Hg (Wyatt et al., 1975;Waters et al., 1977;Banka et al., 1977; Koyanagi, 1979). However, the relationship between coronary perfusion pressure and regional wall motion in the right ventricle remains poorly understood.Accordingly, in the present study, we examined the effects of graded reductions in regional coronary perfusion pressure on regional segment shortening in the right ventricular free wall. Because afterload influences the extent of regional wall motion during systole (Lekven and Kiil, 1975; Sasayama et al., 1980), segment shortening was measured with and without an increased level of right ventricular pressure induced by constricting the pulmonary artery. MethodsThirteen mongrel dogs (19-23 kg) were sedated with intramuscular morphine sulfate (10 mg) and then anest...

Nitric oxide contributes to oxygen demand?supply balance in hypoperfused right ventricle

“…In addition, Heusch et al [9] described a similar close association between decreases in left ventricular oxygen consumption and mechanical function. In contrast, decreases in right coronary blood flow have remarkably little effect on right ventricular function, so long as right coronary perfusion pressure is maintained above a critical value of 30-40 mm Hg [2,3,21]. The current investigation produced findings consistent with these earlier reports; right ventricular function, as indexed by the triple product, was not significantly altered by right coronary hypoperfusion in either the control or treated condition.…”

Transmural distribution of myocardial infarction: difference between the right and left ventricles in a canine model.

“…This phenomena cannot be explained by the pattern of transmural flow distribution. Urabe et al showed a lower level of critical perfusion pressure in the right coronary artery in determining regional myocardial function, 37 which accords well with the present results. The lower level of critical coronary flow in the right ventricle may also be explained by 1) a thinner wall and lower intracavitary pressure in the right ventricle and 2) a lower level of oxygen consumption.…”

Mechanism of attenuated pressure-flow autoregulation in right coronary circulation of dogs.

“…This investigation was prompted by the recent studies of Murray and Vatner 7 and Urabe et al 8 Although neither group specifically assessed right coronary autoregulation, measurements of right coronary flow were reported as right coronary perfusion pressure was altered. Murray and Vatner 7 found that a 34% increase in mean aortic pressure due to aortic constriction in normal conscious dogs was accompanied by a 55% increase in right coronary blood flow.…”