Right ventricular contractility in systemic sclerosis-associated and idiopathic pulmonary arterial hypertension

Since systemic sclerosis (SSc) also involves the heart, the aim of the present study was to evaluate possible differences in right ventricular (RV) pump function between SSc-associated pulmonary arterial hypertension (PAH; SScPAH) and idiopathic PAH (IPAH). In 13 limited cutaneous SScPAH and 17 IPAH patients, RV pump function was described using the pump function graph, which relates mean RV pressure ((P) over bar RV) and stroke volume index (SVI). Differences in pump function result in shift or rotation of the pump function graph. (P) over bar RV and SVI were measured using standard catheterisation. The hypothetical isovolumic (P) over bar RV ((P) over bar RV,iso) was estimated using a single-beat method. The pump function graph was approximated by a parabola: (P) over bar RV=(P) over bar RV,iso[1-(SVI/SVImax)(2)], where SVImax is the hypothetical maximal SVI at zero (P) over bar RV, enabling calculation of SVImax. There were no differences in SVI and SVImax. Both (P) over bar RV and (P) over bar RV,iso were significantly lower in SScPAH than in IPAH ((P) over bar RV 30.7 +/- 8.5 versus 41.2 +/- 9.4 mmHg; (P) over bar RV,iso 43.1 +/- 12.4 versus 53.5 +/- 10.0 mmHg). Since higher pressures were found at similar SVI, the difference in the pump function graph results from lower contractility in SScPAH than in IPAH. Right ventricular contractility is lower in systemic sclerosis-associated pulmonary arterial hypertension than in idiopathic pulmonary arterial hypertension.