Volume-pressure loop hemodynamic characterization of pulmonary hypertension
Authors: Palacios-Echavarren C , Martinez De Lizarrondo E P E , Ayala B , Rodriguez-Arias J J , Domenech-Ximenos B , Sole E , Prat S , Pereda D , Vidal B , Castella M , Blanco I , Garcia-Alvarez A 
Published: October 2024

Abstract

Background
Pulmonary hypertension (PH) includes a wide spectrum of pathologies with different pathological bases and a variety of clinical scenarios in which right ventricular (RV)-pulmonary artery (PA) coupling has relevant prognostic implications. Currently, diagnosis and hemodynamic severity of PH is typically based on mean pulmonary arterial pressure (mPAP), pulmonary capillary wedge pressure (PCWP), and pulmonary vascular resistance (PVR). However, this conception does not take into consideration the evolution of these parameters throughout the cardiac cycle. We hypothesized that not only the magnitude but also the dynamics over time plays an important role in RV adaptation to pressure overload (i.e., constant fixed resistances throughout the cycle will have a different impact than a fluctuating resistances).

Purpose
To assess PA hemodynamic patterns throughout the cardiac cycle and their association with RV remodelling, by combining right heart catheterization (RHC) and cardiac magnetic resonance imaging (CMR) data.

Methods
66 patients with PH (38 women, aged 63.59±14.70years, BMI 28.49±6.21 kg.m2) who underwent RHC in the supine position with a 7.5-FrSwan-Ganz catheter under fluoroscopic guidance (37 precapillary, 17 combined pre-postcapillary, 12 isolated postcapillary PH) and CMR with flow-encoded phase-contrast sequence were included. Pressure and flow tracings at the level of the main PA were integrated to obtain volume-pressure loops throughout the cardiac cycle. The resulting patterns based on morphology (Image 1) and slope (Pattern 1 mean slope 16,11% vs Pattern 2 mean slope 10,37%) were analysed and classified into 2 groups: Pattern 1 and Pattern 2. RV end-systolic (iRVESV) and end-diastolic volumes (iRVEDV), RV ejection fraction, RV mass and presence of late gadolinium enhancement (LGE) at the RV insertion points were compared between groups using parametric and non-parametric tests.

Results
Patients with Pattern 1 showed significantly higher mPAP (46.03±11.62 vs. 35.77±8.10 mmHg) and iPVR (746.22±584.54 vs 319.56±306.21 dynes.s.cm-5.m2) and lower PCWP (11.8±7.6 vs 17.7±7.2 mmHg). Precapillary PH patients more frequently presented a Pattern 1 (n=27; 77.1% vs 10; 32.3%). In addition, patients with Pattern 1 had higher RV volumes (iRVEDV= 105.45±34.62 ml/m2 vs 84.22±35.0 ml/m2, p=0,002; iRVESV 65.05±27.59 ml/m2 vs 44.63±25.09 ml/m2, p=0,001), poorer RV function (RVEF 39.81±11.33% vs 48.96±10.90%; p=0,001), larger RV mass (27.95±9.46 vs 23,44±7.46 g/m2, p=0,045) and smaller left atrial size (24.18±11.47 vs 34.06±19.15 cm2, p&lt;0,001) than patients with Pattern 2. The quantification of LGE was also higher in Pattern 1 as compared with Pattern 2 (5.4±2.4% vs 3.0±2.3%, p&lt;0.001).

Conclusion
Volume-pressure loops at the level of the main PA may differentiate patterns of PA hemodynamic fluctuations that have different impact on RV performance regardless the PH severity within the wide spectrum of PH.Volume-pressure loop patterns