Aortic Reservoir Function has a Strong Impact on the Cardiac Blood Supply–Workload Balance in Children

It has been reported that more than half of the ejected blood from the left ventricle is stored in the aorta during systole and expelled during diastole. One important organ that receives blood flow mainly during diastole is the heart. It is also reported that the cardiac blood supply–workload balance in small children is disadvantageous to the heart. Therefore, we measured the aortic reservoir function and examined the relationship between the aortic reservoir function and the cardiac blood supply–workload balance. The percent diastolic runoff, which is the percentage of the diastolic blood flow of the total cardiac output, was measured as the index of the aortic reservoir function. The subendocardial viability ratio—the ratio of the diastolic pressure time index (the blood supply to the heart) to the tension time index (implying the myocardial oxygen demand)—was investigated as an index of the cardiac blood supply–workload balance in children. The percent diastolic runoff was 51.7 ± 4.5%, smaller than that in adult. It had a significant positive relationship to age (r² = 0.32, p = 0.0052). The subendocardial viability ratio was 100.8 ± 19.6% and had a strong relationship to the percent diastolic runoff (r² = 0.92, p < 0.0001). The percent diastolic runoff had a positive relationship with age during childhood. The value had a strong impact on the cardiac blood supply–workload balance.