Myocardial Extracellular Remodeling is Associated with Ventricular Diastolic Dysfunction in Children and Young Adults with Congenital Aortic Stenosis

Objectives: This study sought to analyze cardiac magnetic resonance (CMR) measurements of myocardial extracellular volume fraction (ECV) and late gadolinium enhancement (LGE) in children and young adults with congenital aortic stenosis (AS) to determine the extent of fibrosis and examine their association with aortic valve and ventricular function.

Background: Patients with congenital AS frequently have impaired diastolic ventricular function and exercise capacity that may be related to myocardial fibrosis.

Methods: A total of 35 patients with congenital AS (median age 16 years) and 27 normal control subjects (median age 16 years) were evaluated by CMR. ECV was calculated from pre- and post-gadolinium contrast T1 measurements of blood and myocardium, and the hematocrit.

Results: ECV was significantly higher in AS patients than in normal subjects (median 0.27 [range 0.22 to 0.42] vs. 0.25 [range 0.18 to 0.27], p = 0.001). LGE was present in 8 (24%) of the AS patients. A higher ECV was correlated with echocardiographic indexes of diastolic dysfunction including a higher mitral E-wave z-score (r = 0.58, p = 0.002), E/septal E' z-score (r = 0.56, p = 0.003), E/mean E' z-score (r = 0.55, p = 0.003), and indexed left atrial volume (r = 0.56, p = 0.001). Other factors associated with an elevated ECV (>0.28) included a greater number of aortic valve interventions (p = 0.004) and a greater number of aortic valve balloon valvuloplasties (p = 0.003). ECV was not significantly associated with AS gradient, left ventricular mass, mass/volume ratio, or ejection fraction.

Conclusions: In young patients with AS, myocardial ECV is significantly elevated compared with control subjects and is associated with echocardiographic indexes of diastolic dysfunction. ECV measured by CMR may be a useful method for risk stratification and monitoring therapies targeting fibrosis.