Effects of heart rate and right ventricular pressure on right coronary arterial flow and its systolic versus diastolic distribution in a variety of congenital heart diseases in children

BACKGROUND AND METHODS: In order to elucidate the underlying adjusting mechanism of human right coronary arterial (RCA) flow to increased right ventricular pressure (RVP) in children, we recorded RCA flow velocity in 24 pediatric cardiac patients at the orifice of its main trunk at the time of heart catheterization using the Doppler guidewire. RESULTS: The ratio of diastolic flow (DF)/total flow (TF), or the proportion of the DF time integral over a total of one cardiac cycle, had a negative correlation with heart rate (HR; r = -0.58, n = 11) in children with normal right ventricular systolic pressure (RVSP; RVSP < 35 mmHg). In contrast, the DF/TF ratio had a good correlation (r = 0.88, n = 24) with RVSP in all patients under study. The ratio of diastolic area (DA)/total area (TA), defined as the ratio of an area encircled by the aortic pressure curve above and the RVP curve below for diastole, over a total of one cardiac cycle, representing the overall effect of both HR and transcoronary pressure difference, also correlated well (r = 0.89, n = 24) with DF/TF. Total volume flow of the RCA also increased (r= 0.76, n = 24) with increases in RVSP, first by an increase in flow velocity through the RCA, during both systole and diastole, then by widening of the RCA lumen at very high pressures. These changes were initially more dependent on diastole with increasing RVSP because: (i) of a more marked augmentation of flow velocity in diastole compared with systole; and then (ii) of a significant decrease in flow velocity in systole at very high pressures. CONCLUSIONS: We clarify how the RCA manages to increase flow through it at different HR as a function of chronic RVP overload in pediatric cardiac patients.