Abstract 19921: Cardiac MRI T1 Mapping Noninvasively Predicts Interstitial Myocardial Fibrosis in the Absence of Late Gadolinium Enhancement
Introduction: Myocardial fibrosis is associated with arrhythmia, ventricular dysfunction and adverse outcomes. Cardiac magnetic resonance (CMR) late gadolinium enhancement (LGE) is the current standard of reference for noninvasive scar assessment, but is insensitive to diffuse fibrosis. Histologic data suggests myocardial T1 time is shorter in post cardiac transplant patients, but little data is available for other etiologies of nonischemic cardiomyopathy.
Methods: 73 patients underwent endomyocardial biopsy (EMB) and CMR to establish the etiology of nonischemic cardiomyopathy. Biopsies for routine post cardiac transplant surveillance were excluded. CMR was performed on a 1.5 T scanner with 0.2 mmol/kg gadolinium-DTPA contrast. Left ventricular function was measured using SSFP cine sequences. Myocardial strain was assessed with tagged cine images. Myocardial T1 mapping was performed using a postcontrast inversion recovery Look-Locker sequence corrected for delay time and renal function using a 3 compartment model. Histologic analysis was performed using digital images of biopsy specimens stained with Masson's trichrome. Fibrosis was quantitatively measured as a percentage of total myocardium using automated image analysis software.
Results: 47/73 (64%) of patients had areas of focal myocardial scar. 26/73 patients (36%) (mean age 42 +/− 16 years, 48% male) had diagnostic CMR, EMB and had no visually identifiable scar by LGE CMR. For patients without scar, the mean ejection fraction was 49 +/− 14%, midwall circumferential strain (Ecc) was reduced (−13.0 +/− 5.4%) and mean T1 time was 478 +/− 70 ms. The mean percent myocardial fibrosis by histologic evaluation was 6.98+/− 3.95%. There was a significant inverse correlation between CMR T1 time and histologic fibrosis (r=−0.42, p=0.03). Shorter T1 time was not related to Ecc strain (r=0.39 p=0.13).
Conclusion: Interstitial myocardial fibrosis was present even in the absence of visually identifiable delayed gadolinium enhancement. Shorter T1 time correlated with increased histologic fibrosis but not with altered myocardial strain. T1 mapping may improve the sensitivity of CMR for detection of diffuse myocardial strain.
- © 2010 by American Heart Association, Inc.