Prognostic Value of Myocardial Extracellular Volume Fraction and T2-mapping in Heart Transplant Patients

Abstract

Objectives: The purpose of this study was to examine prognostic value of T1- and T2-mapping techniques in heart transplant patients.

Background: Myocardial characterization using T2 mapping (evaluation of edema/inflammation) and pre- and post-gadolinium contrast T1 mapping (calculation of extracellular volume fraction [ECV] for assessment of interstitial expansion/fibrosis) are emerging modalities that have been investigated in various cardiomyopathies.

Methods: A total of 99 heart transplant patients underwent the magnetic resonance imaging (MRI) scans including T1- (n = 90) and T2-mapping (n = 79) techniques. Relevant clinical characteristics, MRI parameters including late gadolinium enhancement (LGE), and invasive hemodynamics were collected. Median clinical follow-up duration after the baseline scan was 2.4 to 3.5 years. Clinical outcomes include cardiac events (cardiac death, myocardial infarction, coronary revascularization, and heart failure hospitalization), noncardiac death and noncardiac hospitalization.

Results: Overall, the global native T1, postcontrast T1, ECV, and T2 were 1,030 ± 56 ms, 458 ± 84 ms, 27 ± 4% and 50 ± 4 ms, respectively. Top-tercile-range ECV (ECV >29%) independently predicted adverse clinical outcomes compared with bottom-tercile-range ECV (ECV <25%) (hazard ratio [HR]: 2.87; 95% confidence interval [CI]: 1.07 to 7.68; p = 0.04) in a multivariable model with left ventricular end-systolic volume and LGE. Higher T2 (T2 ≥50.2 ms) independently predicted adverse clinical outcomes (HR: 3.01; 95% CI: 1.39 to 6.54; p = 0.005) after adjustment for left ventricular ejection fraction, left ventricular end-systolic volume, and LGE. Additionally, higher T2 (T2 ≥50.2 ms) also independently predicted cardiac events (HR: 4.92; CI: 1.60 to 15.14; p = 0.005) in a multivariable model with left ventricular ejection fraction.

Conclusions: MRI-derived myocardial ECV and T2 mapping in heart transplant patients were independently associated with cardiac and noncardiac outcomes. Our findings highlight the need for larger prospective studies.

Keywords: T1 mapping; T2 mapping; extracellular volume fraction; heart transplantation; magnetic resonance imaging; natural history; prognosis.

FIGURE 1. Baseline and Follow-Up

T1-mapping values were shown as mean global native T1, postcontrast T1, and extracellular volume fraction (ECV) in the left panel and as tercile categories in the right panels.

CENTRAL ILLUSTRATION. Survival Curves Categorized by Myocardial ECV and T2 Mapping

(A) Extracellular volume fraction (ECV) for all clinical events (covariates = left ventricular end systolic volume index [LVESVI], presence of late gadolinium enhancement [LGE]). (B) ECV for cardiac events (unadjusted). (C) T2 mapping for all clinical events (covariates = left ventricular ejection fraction [LVEF], LVESVI, presence of LGE). (D) T2 mapping for cardiac events (covariates = LVEF).