The importance of Post-Processing Methods for Assessing Right Ventricular Volumes and Function in Patients with Pulmonary Hypertension, results from the PRINCEPT study

Background: Right ventricular (RV) function and volumes assessment by cardiac magnetic resonance imaging (CMR) has emerged as a strong prognostic marker in patients with pulmonary hypertension (PH), but expert centers propose different thresholds, possibly explainable by methodological differences.

What is the impact of including or excluding RV trabeculations on RV metrics in PH patients? Which level of pulmonary artery (PA) flow assessment is most reliable for estimating RV stroke volume (RVSV) using four-dimensional flow magnetic resonance imaging (4D-Flow MRI).

Methods: 42 patients with PH were prospectively recruited as part of the PRINCEPT study and underwent right heart catheterization and CMR including 4D-Flow MRI. RVSV, RV ejection fraction (RVEF), end systolic volume index (RVESVi), and mass were assessed either including (Tin(v)) or excluding (Tex(v)) the trabeculations from the RV volume. RVSV_Tin(v) and RVSV_Tex(v) were then compared to the PA forward flow (PAFF) measured at the mid-PA trunk (Mid_PAFF) and at the PA annular level (Ann_PAFF), using 4D-flow MRI. 23 were re-evaluated after surgery: patients with chronic thrombo-embolic PH underwent pulmonary endarterectomy, while patients with refractory pulmonary arterial hypertension had lung transplantation.

Results: Excluding trabeculations from RV volumes led to higher RVEF, RVSV, and RV mass (45.8±12.9% vs. 40.4±12.7%; 70.2±20.8ml vs. 64±18.6ml; and 57.4±23.5g vs. 41.1±16.5g, respectively; all P< 0.001), and lower RVESVi (51±28.2ml/m² vs. 58.8±30.5ml/m², P< 0.001). Compared to the standard approach of associating mid-PAFF flow measurement with RVSV_Tin(v), association between Ann_PAFF and RVSV_Tex(v) was stronger (Pearson r coefficients were 0.66 and 0.85 respectively, P=0.04). Our longitudinal analysis demonstrated strong changes for RV Mass, RVESVi and RVEF. Post-operative data demonstrated a significant reduction in the impact of excluding trabeculations on RV metrics measurements, underscoring the effects of reverse remodelling.

Conclusion: Post-processing methodological differences using CMR and 4D-Flow MRI significantly impacted RV measurements when applying guideline-recommended thresholds.

Scatter plot comparing preoperative assessment of RVEF measured using 2 different volumetric methods: RVEF Excluding Tex(v) were higher by about +5.49% than those obtained including trabeculations Tin(v).
Cine Fiesta short axis views showing Right Ventricle (RV) volume assessment including (Tin(v) versus excluding (Tex(v)) trabeculations within the RV volume in diastole (A-C) and in systole (B-D).