Right ventricular remodeling in idiopathic pulmonary arterial hypertension: adaptive versus maladaptive morphology

https://doi.org/10.1016/j.healun.2014.11.002Get rights and content

Background

Although increased pulmonary pressure is caused by changes in the pulmonary vasculature, prognosis in idiopathic pulmonary arterial hypertension (IPAH) is strongly associated with right ventricular (RV) function. The aim of this study was to describe the best RV adaptive remodeling pattern to increased afterload in IPAH.

Methods

In 60 consecutive patients with IPAH, RV morphologic and functional features were evaluated by echocardiography and cardiac magnetic resonance imaging. To address the question of the best RV adaptation pattern, we divided the study population into two groups by the median value of RV mass/volume ratio (0.46) because this parameter allows the distinction between RV eccentric (≤0.46) and concentric hypertrophy (>0.46). The two groups were compared for RV remodeling and systolic function parameters, World Health Organization class, pulmonary hemodynamics, and 6-minute walk test.

Results

Despite similar pulmonary vascular resistance, mean pulmonary pressure, and compliance, patients with eccentric hypertrophy had advanced World Health Organization class and worse 6-minute walk test, hemodynamics, RV remodeling, and systolic function parameters compared with patients with concentric hypertrophy. The group with concentric hypertrophy had higher RV to pulmonary arterial coupling compared with the group with eccentric hypertrophy (1.24 ± 0.26 vs 0.83 ± 0.33, p = 0.0001), indicating higher RV efficiency. A significant correlation was found between pulmonary vascular resistance and RV to pulmonary arterial coupling (r = −0.55, r2 = 0.31, p = 0.0001), with patients with RV mass/volume ratio > 0.46 at the higher part of the scatterplot, confirming more adequate RV function.

Conclusions

Concentric hypertrophy might represent a more favorable RV adaptive remodeling pattern to increased afterload in IPAH because it is associated with more suitable systolic function and mechanical efficiency.

Section snippets

Population and study protocol

Our study population comprised 60 consecutive therapy-naïve patients affected by IPAH, World Health Organization functional class II to IV, without severe tricuspid regurgitation, referred to our Pulmonary Hypertension Unit (Policlinico Umberto I, Sapienza University of Rome) from January 2011 to December 2012. A control group for RV M/V ratio evaluation comprised 20 healthy subjects matched for age, gender, weight, and height. According to the European guidelines,10 the diagnosis of PAH was

Results

Table 1 summarizes the characteristics of the study population. Most of the patients with IPAH were female and in World Health Organization class III, with severe pulmonary hypertension and impaired effort capacity. Clinical depression was the most frequent co-morbidity, followed by thyroid disease and hypercholesterolemia.

Compared with normal subjects, patients with IPAH showed higher RV mass and volume values, lower RV ejection fraction, and higher RV M/V ratio. Among the IPAH group, RV M/V

Discussion

This study combines echocardiographic and CMR imaging to evaluate the influence of different modalities of RV morphologic adaptation to afterload on RV systolic function, hemodynamics, and clinical status of patients with IPAH. As expected, patients with IPAH showed severe RV remodeling, with higher mass values and larger volumes compared with the control group. Patients with IPAH showed a higher RV M/V ratio compared with healthy subjects. This pattern (higher M/V ratio) suggests that

Disclosure statement

Each author of this article has made substantial contributions to conception and design and acquisition, analysis, and interpretation of data; has drafted the submitted article or revised it critically for important intellectual content; has provided final approval of the version to be published; and has agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

This

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      Moreover, a disproportionate increase in right ventricular mass index (RVMI) compared with RVEDV indicates concentric hypertrophy and is associated with a favorable outcome in IPAH (13). Eccentric hypertrophy with a disproportionate increase in RVEDV compared with RVMI is considered a maladaptive response to increased afterload and is associated with a poor outcome (13,41). In IPAH, therefore, caution should be exercised when using mass measurements in isolation because they give incomplete information on RV adaptation.

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