OBJECTIVES: The purpose of this study was to use cardiac magnetic resonance 
(CMR) imaging and invasive left ventricular (LV) pressure-volume (PV) 
measurements to explore the relationship between diffuse myocardial fibrosis and 
indexes of diastolic performance in a cohort of cardiac transplant recipients.
BACKGROUND: The precise mechanism of LV diastolic dysfunction in the presence of 
myocardial fibrosis has not previously been established.
METHODS: We performed CMR with T1 mapping and obtained invasive LV PV 
measurements via a conductance catheter in 20 cardiac transplant recipients at 
the time of clinically-indicated coronary angiography.
RESULTS: Both post-contrast myocardial T1 time and extracellular volume fraction 
correlated with β, the load-independent passive LV stiffness constant 
(r = -0.71, p = 0.001, and r = 0.58, p = 0.04, respectively). After multivariate 
analysis, post-contrast myocardial T1 time remained the only independent 
predictor of β. No significant associations were observed between myocardial T1 
time and τ, the active LV relaxation constant, or other load-dependent 
parameters of diastolic function.
CONCLUSIONS: Diffuse myocardial fibrosis, assessed by post-contrast myocardial 
T1 time, correlates with invasively-demonstrated LV stiffness in cardiac 
transplant recipients. In patients with increased diffuse myocardial fibrosis, 
abnormal passive ventricular stiffness is therefore likely to be a major 
contributor to diastolic dysfunction.