Background: In chronic pulmonary hypertension (PH), the main cause of death is right ventricular (RV) failure. However, the onset of RV dysfunction varies significantly among patients. Early recognition of RV maladaptation would be highly relevant.

Purpose: To identify cardiac magnetic resonance (CMR)-derived parameters affected in early stages of PH before the development of RV dysfunction.

Methods: Experimental chronic PH was generated by pulmonary vein banding in 76 pigs whereas 14 animals underwent sham operation. Animals were followed-up monthly with right heart catheterization (RHC) and immediate CMR for a maximum of 9 months. CMR exams included a T1-mapping sequence to quantify equilibrium-extracellular volume (ECV) at the RV insertion points. Pairs of RHC and CMR examinations were compared among controls and PH with normal RV ejection fraction (RVEF≥55%) or reduced (REVF<55%) using ANCOVA test with Bonferroni correction. All procedures followed the “Principles of laboratory animal care”.

Results: In the presence of PH confirmed by RHC and normal RVEF, the RV displays significant hypertrophy and increased myocardial native T1 and ECV, despite preserved ventricular dimensions and PA flow (Fig 1B). In advanced stages of the disease, RV-AP uncoupling and reduced PA pulsatility develop together with RV dilatation and failure (Fig 1C).

Conclusion: RV hypertrophy and ECV expansion are early mechanisms in RV adaptation to postcapillary PH, whereas ventricular and PA dilatation, RV-PA uncoupling and reduced pulsatility appear in more advanced stages concurring with systolic dysfunction.