BACKGROUND: The underlying pathophysiology of heart failure with preserved 
ejection fraction (HFPEF) is incompletely understood, but myocardial 
extracellular matrix accumulation is thought to play a major role. Our aims were 
to estimate myocardial extracellular matrix using cardiac magnetic resonance T1 
mapping and to assess the relationship between pathobiology/pathophysiology and 
prognosis.
METHODS AND RESULTS: Patients with suspected HFPEF (n=100) were enrolled in this 
prospective, observational study. Confirmatory diagnostic tests, cardiac 
magnetic resonance imaging including T1 mapping, and invasive hemodynamic 
assessments were performed at baseline. Sixty-one patients with confirmed HFPEF 
entered a longitudinal outcome-monitoring phase (mean, 22.9±5.0 months), during 
which 16 had a cardiac event. Cardiac magnetic resonance T1 time (hazard ratio, 
0.99; 95% confidence interval, 0.98-0.99; P=0.046), left atrial area (hazard 
ratio, 1.08; 95% confidence interval, 1.03-1.13; P<0.01), and pulmonary vascular 
resistance (hazard ratio, 1.01; 95% confidence interval, 1.00-1.01; P=0.03) were 
significantly associated with cardiac events. Patients with T1 times below the 
median (<388.3 ms) were at greater risk of cardiac events than the rest of the 
group (P<0.01). Extracellular matrix of left ventricular biopsies (n=9), 
quantified by TissueFAXS technology correlated with T1 time (R=0.98; P<0.01). T1 
time also correlated with right ventricular-pulmonary arterial coupling 
(pulmonary vascular resistance: R=-0.36; P<0.01; right ventricular ejection 
fraction: R=0.28; P=0.01).
CONCLUSIONS: In the present preliminary study, cardiac magnetic resonance 
postcontrast T1 time is associated with prognosis in HFPEF, suggesting 
postcontrast T1 as possible biomarker for HFPEF.