Rationale: Pulmonary hypertension (PH) is characterized by increased arterial load requiring more right ventricular (RV) hydraulic power to sustain adequate forward blood flow. Power can be separated into a mean and oscillatory part. The former is associated with mean and the latter with pulsatile blood flow and pressure. Because mean power provides for net blood flow, the ratio of oscillatory to total power (oscillatory power fraction) preferably should be small. It is unknown whether this is the case in pulmonary arterial hypertension (PAH).
Objectives: To derive components of power generated by the right ventricle in PAH.
Measurements and main results: Thirty-five patients with idiopathic PAH (IPAH) and 14 subjects without PH were included. The patients were divided in two groups, "moderate" and "high," based on pulmonary artery (PA) pressure. PA pressures were obtained by right heart catheterization and PA flows by magnetic resonance imaging. Total hydraulic power (Power(total)) was calculated as the integral product of pressure and flow. Mean hydraulic power (Power(mean)) was calculated as mean pulmonary artery pressure times mean flow. Their difference is oscillatory power (Power(oscill)). Total hydraulic power in subjects without PH compared with moderate and high IPAH was 0.29 ± 0.10 W (n = 14), 0.52 ± 0.14 W (n = 17), and 0.73 ± 0.24 W (n = 18), respectively. The oscillatory power fraction is approximately 23% and not different between groups.
Conclusions: In this study, oscillatory power fraction is constant at 23% in non-PH and IPAH, implying that a considerable amount of power is not used for forward flow, making the RV less efficient with respect to its arterial load. Our findings emphasize the need to develop new therapy strategies to optimize RV power output in PAH.