Postoperative assessment of interstitial myocardial fibrosis in aortic valve pathologies: insights from a cardiac magnetic resonance study
Authors: Oberg Arouca Bassoli L , Rosa V E E , Pires L J N T , Cavalvante P N , Rochitte C E , Lopes M P , Fernandes J R C , Sampaio R O , Tarasoutchi F 
Published: October 2024

Abstract

Background
Data on the characteristics of diffuse myocardial fibrosis (DMF) among patient undergoing valve surgery for aortic regurgitation (AR), high-gradient aortic stenosis (HG-AS), and low-flow low-gradient aortic stenosis with low ejection fraction (LFLG-AS) are limited.

Purpose
To assess the postoperative characteristics of DMF and to compare post- and pre-operative cardiac magnetic resonance imaging (CMR) data.

Methods
Patients diagnosed with AR (38), HG-AS (62), and LFLG-AS (39), who met criteria for surgical intervention, were prospectively included. Pseudo-severe AS was excluded. Post-operative CMR was performed 6 to 8 months after surgery, and a comparison between post- and pre-operative data was made (delta=Δ). Quantitative analysis included assessment of extracellular volume fraction (ECV), indexed ECV (iECV), and myocardial mass (MM).

Results
There were differences in baseline characteristics among patients with AR, HG-AS, and LFLG-AS concerning age (54±14 vs 63±8 vs 67±8 years, respectively; p&lt;0.01), male gender (75% vs 50% vs 82%, respectively; p&lt;0.01), NYHA functional class III and IV (37.5% vs 55.2% vs 30.8%, respectively; p=0.03), EuroSCORE II (1.16±0.5 vs 1.26±0.46 vs 3.39±2.65%, respectively; p&lt;0.01), and STS (0.74±0.29 vs 1.11±0.5 vs 3.21±2.11%, respectively; p&lt;0.01). Global ECV was similar between groups (29.2±5.6 vs 27.0±3.6 vs 29.4±5.9%, respectively; p=0.01), MM was different between groups (215±76 vs 161±51 vs 203±51g, respectively; p&lt;0.01), and iECV was different between groups and significantly higher in AS patients (50.1±31.0 vs 21±8 vs 34.2±10.2ml/m², respectively; p&lt;0.01). All patients underwent valve surgery and there were differences regarding extracorporeal circulation time (94±25 vs 97±20 vs 75±41min, respectively; p&lt;0.01), and 30-day mortality (0% vs 3% vs 15%, respectively; p&lt;0.01). Post-surgery data from patients with AR (32), HG-AS (62), and LFLG-AS (21) demonstrated a comparable decrease across all groups concerning preoperative MM (ΔMM: -39.3±41.5 vs -33.4±30.9 vs -23.4±34.2g, respectively; p=0.36) (Figure 1). In contrast, iECV decreased post-surgery only in AR, remaining stable in HG-AS and LFLG-AS (ΔiECV: -19.1±22.5 vs -1.4±7.4 vs 0.9±12ml/m², respectively; p&lt;0.01). Thus, postoperative ECV maintained commensurate values in AR, while increasing in HG-AS and LFLG-AS (ΔECV: -0.1±4.5 vs 1.5±5.1 vs 2.9±4.9%, respectively; p=0.09). Δ left ventricular ejection fraction (LVEF) was similar across groups (ΔLVEF: -1.5±10.6 vs 1.1±11.7 vs 2.6±16%, respectively; p=0.44).

Conclusion
In the postoperative period, a decrease in MM was observed in all groups of aortic valve pathologies. However, only patients with AR showed a simultaneous and proportional reduction in DMF mass, explaining the patterns of ECV variation. Thus, the reduction of DMF in the postoperative period appears to vary according to the phenotypes presented, and patients with AR exhibit early reverse remodeling despite having high levels of DMF.Delta iECV, LV mass and ECV measures