Right ventricular concentric hypertrophy and clinical worsening in idiopathic pulmonary arterial hypertension

Background: Because the pathophysiology of idiopathic pulmonary arterial hypertension (IPAH) is an afterload mismatch, wall stress represents the most important feature affecting the overloaded right ventricle (RV). Thus, the RV mass/volume (M/V) ratio may reflect more adequately the suitability of the remodeling pattern in minimizing RV wall stress compared with the lone RV volume. This study investigated the prognostic effect of the RV M/V ratio in IPAH. Methods: Enrolled in our center were 74 therapy-naïve IPAH patients who were prospectively monitored for the presence of clinical worsening (CW). Baseline evaluation included clinical, hemodynamic, and echocardiographic parameters. Cardiac magnetic resonance was used for RV M/V ratio determination. Results: During 541 ± 283 days of follow-up, 31 of 74 patients (42%) presented with CW. Actuarial rates of CW were 14%, 28%, and 46%, at 6, 12, and 24 months, respectively. The RV M/V ratio significantly improved the power of the prognostic model based on traditional clinical, hemodynamic, and imaging parameters (area under the curve: 0.74 vs 0.66, respectively; p = 0.01). When the cutoff values of the RV M/V ratio and cardiac index (CI) derived from receiver operating characteristic curve analysis were combined, patients with a low RV M/V ratio/low CI, low RV M/V ratio/high CI, and high RV M/V ratio/low CI showed a 28.8, 8.8, and 6.1 increase in the hazard ratio, respectively, compared with high RV M/V ratio/high CI patients (p = 0.0001). Conclusions: The RV M/V ratio is an independent predictor of prognosis in IPAH and may allow clinicians to better stratify patients with normal CI, identifying at an early stage those patients at higher risk of right heart failure development before hemodynamic instability appears.