The Role of Cardiovascular Magnetic Resonance Imaging in Noninvasive Assessment of Pulmonary Hypertension Severity

Abstract

Objective: Pulmonary hypertension characterized by structural and mechanical changes in pulmonary vascular bed. Invasively calculated pulmonary artery (PA) stiffness indeces are associated with mortality in pulmonary hypertension (PH). CMRI-derived pulmonary artery distensibility (PAD) index reflects vascular remodeling in patients with pulmonary PH. The aim of the study was to evaluate the relationship between noninvasive PAD index and invasive PA stiffness indeces and basic determinants of PH severity. Design and method: We included 48 pts with PH (mean age 42.8± 14.7 yrs, m:f = 13:35): 27 idiopathic pulmonary arterial hypertension pts, 5 pts scleroderma PAH, 6 corrected congenital heart disease and 10 with inoperable CTPEH. All pts underwent 6-min walk test (6MWT), right heart catheterization (RHC), ECHO, CMRI, cardiopulmonary exercise testing (CPX). PA stiffness index and elastic modulus were calculated using data from RHC and CMRI. Pulmonary artery distensibility index (%) were derived from cross-sectional images of the main PA on cardiac magnetic resonance imgaging. Results: We revealed increased PA stiffness index 6.1 (4.6–10.2) and elastic modulus 424 mm Hg (254-678), decreased PAD index in PH pts 10% (9 –16.5). There was a significant negative correlation between PAD index and PA stiffness index (r = –0.90; p < 0.0001), so we derived the formula to calculate the invasive PA stiffness using noninvasive PAD index: PA stiffness index = 102.4/ PAD index. There was also a negative correlation between PAD and elastic modulus (r = –0.91; p < 0,0001). Patients with decreased PAD index < 20 % had higher NT-proBNP level (1558 (738-4341) versus 306 (178-370); p<0.05), also ECHO signs of RV systolic dysfunction:lower TAPSE (1.7 ±0.4 cm versus 2.0±0.4 cm; p = 0,04), tricuspid annular systolic velocity (10±2 versus 12±1 cm/sec; p = 0,007), global RV myocardial deformation (13±4% versus 21±5%; p = 0,001) and RV fractional area change ( 24±7%; p = 0,02) and reduced cardiac output which were determined by RHC (4.0 ± 1.1 versus 4.9 ±1.2 l/min; p < 0,05). Conclusions: Noninvasive CMRI-derived PA distensibility index strongly correlated with PA stiffness indeces, and may be used for noninvasive assessment of PH severity.