Diastolic-systolic coronary flow differences are caused by intramyocardial pump action in the anesthetized dog.

Abstract

SUMMARYThe effect of cardiac contraction on coronary arterial flow has been described in terms of an intramyocardiaJ pump, which displaces blood backward and forward during systole and diastole, respectively. Normally, the mean forward flow exceeds, and consequently conceals, this backflow. The main left coronary artery of six anesthetized open-chest dogs was perfused with a Gregg cannula from a constant pressure source via a pcrfusion line containing an adjustable stenosis. At mean left main arterial pressures, P^, of 65, 90, 125, and 155 mm Hg, the hearts were perfused via different grades of stenosis, while a constant mean perfusion pressure (Pu,) distal to the stenosis was maintained. Mean coronary flow was then independent of stenosis grade. However, with increasing stenosis grade, the systolic-diastolic coronary flow difference decreased, whereas the dlastolic-systolic coronary pressure difference increased. By varying the stenosis grade at constant P^ linear relationships between diastolic-systolic pressure difference and flow difference were obtained and were interpreted as being a result of an electrical analog potential-source equivalent. From the potential-source equivalent, the diastolic-systolic pressure changes of the intramyocadial pump, pi_, can be determined as well as the coronary resistance, R., impeding the flow variations originated by p^. We found p^ = 53.1 ± 7.02 (SD) nun Hg, and independent of P^. R. was correlated with the resistance to coronary flow, Re, via R. = 0.63 x R,. -12.9 mm Hg»s/ml (r -0.939, n -25). R* was defined as (Pic -14 nun Hg)/mean coronary flow. The waterfall model extended to allow for autoregulation to achieve an equal division of mean flow over the myocardium could not explain these results. From a decay curve of coronary arterial pressure following clamping of the perfusion line, intramyocardial coronary capacitance was estimated to be approximately 0.07 ml/mm rig/100 g LV. This value is in agreement with published volume pressure relationships of the intramyocardial blood compartment. The phasic coronary blood flow component requires intramyocardial arterial volume. We conclude that systolic-diastolic variations in coronary blood flow are not due to varying resistances but are caused by an active intramyocardial pump. Circ Res 49.-SS4-593, 1981THREE centuries have elapsed since Scaramucci (Porter, 1898) first speculated on the phasic nature of coronary blood flow. In modern physiological thinking, two more or less parallel lines of reasoning developed: Sabiston and Gregg (1957) held that contraction of the heart impedes coronary arterial flow, whereas Wiggers (1954) believed that systole and diastole were inseparable. In the second volume of Circulation Research, Wiggers states, "The volume of blood that can enter intramural vessels during diastole must depend to some extent on the degree to which they are emptied during preceding systole," supporting this opinion with the observation that systole enhances coronary venous outflow.From the Department of Physiology ...

Temporal diffeomorphic free-form deformation: Application to motion and strain estimation from 3D echocardiography

“…Muscle contraction is augmented when vascular emptying is facilitated. This corroborates with data showing that vascular volumes decreases with contraction (Spaan et al (1981)). Yin et al (1996) experimentally showed the change of vascular volume to vary from 2 to 4 ml/100 g tissue when modifying the perfusion pressure from 0 to 120 mmHg.…”

Association between coronary lesion severity and distal microvascular resistance in patients with coronary artery disease

“…It is known that coronary flow occurs mainly during diastole, and the pressure amplitude can significantly increase at the distal site of a coronary stenosis (21). The magnitude of the distal pressure amplitude depends on the severity of coronary stenosis.…”

Analysis of lumped parameter models for blood flow simulations and their relation with 1D models

“…For each ∆x, we display the difference between the entropy functional e from (18) and the linear energy e lin given in (19). Precisely, for each pair of solutions (P 0D , Q 0D ) we compute…”

“…The large number of micro-circulation networks connecting each small artery to small vein also makes the method of discretely modelling individual vessel segments computationally prohibitive. To overcome this problems, a lumped parameter model of micro-circulation is used [19]. This model contains only a resistor and a capacitance.…”