Cardiac MRI-Derived Left Ventricular Pressure-Volume Loops Enhance Personalized Assessment of Disease Severity and Prognosis in Pulmonary Arterial Hypertension

Background: In pulmonary arterial hypertension (PAH), the increase in pulmonary vascular resistance (PVR) causes right ventricular (RV) pressure overload and consequent underfilling of the left ventricle (LV) (1).

Recently developed non-invasive LV pressure-volume (PV) loops, derived from cardiovascular magnetic resonance (CMR) imaging in combination with brachial arterial pressures, allow estimation of stroke work (SW), ventricular efficiency (VE), external power, contractility, arterial elastance (Ea), and ventriculo-arterial coupling (VAC) (2).

The present study aimed to assess whether CMR-based LV PV loops can improve individualized evaluation and prognostic prediction in patients with PAH.

Methods: LV PV loops were generated from short-axis balanced steady-state free-precession cine CMR sequences. Invasive hemodynamics were collected using right heart catheterization (2, 3).

Patients were categorized into two groups, separating those with marked RV pressure overload from those with mild overload, according to a composite score derived from CMR risk factors outlined in the most recent European Society of Cardiology guidelines for pulmonary hypertension (4).

The primary outcome was defined as death or lung transplantation during follow-up.

Results: CMR examinations from 90 PAH patients (mean age 57.0 ± 19.1 years, 73% women) and 27 healthy controls (mean age 58.6 ± 9.1 years, 63% women) were analysed.

Compared to controls, patients with PAH demonstrated higher contractility, Ea, and VAC but lower SW and VE. Within the PAH cohort, individuals with severe RV pressure overload exhibited elevated Ea and VAC but reduced SW, VE, and external power compared with those with mild overload (Figure 1).

SW, external power, VE, Ea, and VAC correlated significantly with invasively measured mean pulmonary artery pressure and PVR (Figure 2a–d).

Over a median follow-up of 11.7 years (IQR 8.0–15.0 years), 65% of patients with PAH experienced death or lung transplantation (n=58/89; one patient lost to follow-up). Cox regression revealed that SW predicted outcome in the youngest third of the PAH cohort (age ≤ 55 years), with infra-median values associated with poorer prognosis (HR = 0.307, 95% CI = 0.095–0.992) (Figure 3).

Conclusion: Patients with PAH exhibit altered LV mechanics that depend on the degree of RV pressure overload. Ea, VAC, SW, VE, and external power correlate with disease severity. Among patients ≤ 55 years, supra-median SW was associated with longer lung transplantation-free survival, making it a potential prognostic marker.

Figure 1: Comparisons between PAH patients and controls as for mechanical derivatives calculated by use of non-invasive PV loops. Severely pressure overload PAH patients (blue) n = 56, mildly pressure overloaded PAH patients (orange) n= 36, healthy controls (green) n= 27. Student’s t-tests were performed to identify differences between mean values in the different groups; the symbol * indicates p values <0.050, the symbol ** indicates p values <0.010
Figure 2: Correlations between (a) LV stroke work and mean pulmonary artery pressure (PAP), (b) systemic arterial elastance and mean pulmonary artery pressure (c) LV stroke work and pulmonary vascular resistance (PVR), (d) systemic arterial elastance and pulmonary vascular resistance.
Figure 3: Kaplan-Meier survival curves for PAH patients after index cardiac MRI. Supra-median stroke work (SW) values show present a more favorable outcome in terms of lung transplantation-free survival with an age-adjusted Hazard Rate in the younger third of the PAH patients' cohort with age up to 55 years.