NATIVE T1 RELAXATION TIME AND MYOCARDIAL EXTRACELLULAR VOLUME ARE ACCURATE MARKERS OF DIFFUSE MYOCARDIAL FIBROSIS IN HEART VALVE DISEASE: A COMPARISON WITH LEFT VENTRICULAR MYOCARDIAL BIOPSY

Aims: Diffuse myocardial fibrosis (DFM) is one of the major mechanisms in the pathophysiology of heart diseases. The aim of the present study was to investigate the relationship between the cardiac magnetic resonance (CMR) - derived native T1 relaxation time and myocardial extracellular volume (ECV) fraction and the extent of DMF at targeted myocardial left ventricular (LV) biopsy.
Methods and results: The study population consisted of 40 consecutive patients (age 63±8y, 65% males) undergoing valve and/or ascending aorta surgery for severe aortic stenosis (77.5%), root dilatation (7.5%) or valve regurgitation (15%). All patients underwent CMR-derived T1 mapping prior to surgery. The T1 relaxation time was assessed in basal interventricular septum pre and 10 min post contrast administration using the modified Look-Locker Inversion (MOLLI) recovery sequence. A LV myocardial biopsy specimen was obtained during surgery from the basal interventricular septal segment matched with the T1 mapping assessment. The percentage of myocardial collagen was quantified using the Picrosirius Red. The average percentage of myocardial collagen was 22.0 ± 14.8 %. Both native T1 relaxation time with cutoff value of ≥ 1010 ms (sensitivity=90%, specificity=73%, area under the curve =0.82) and ECV with cutoff value of ≥ 0.32 (sensitivity=80%, specificity=90%, area under the curve =0.85) showed high accuracy to identify severe (> 30%) DMF. The native T1 relaxation time showed significant correlation with LV mass (p<0.01) while the ECV did not (p=NS).
Conclusions: Native T1 relaxation time and ECV at 10 minutes after contrast administration are accurate markers of DFM.