Myocardial Native T₁ Predicts Load-Independent Left Ventricular Chamber Stiffness In Patients With HFpEF

Objectives: This study sought to evaluate the potential of cardiac magnetic resonance T₁ mapping to detect load-independent left ventricular (LV) chamber stiffness by histological confirmation.

Background: Accurate noninvasive diagnosis of LV diastolic dysfunction in heart failure with preserved ejection fraction (HFpEF) remains challenging.

Methods: Nineteen HFpEF patients (14 female, 65 ± 16 years of age) without primary cardiomyopathy were prospectively enrolled. Cine, late gadolinium enhancement cardiac magnetic resonance, and triple-slice T₁ mapping using a modified Look-Locker inversion recovery sequence were performed at 3-T. Extracellular volume (ECV) was quantified from pre- and post-contrast T₁ values of the blood and myocardium with hematocrit correction. LV stiffness constant (beta) was assessed by calculating the slope of the end-diastolic pressure-volume relationship curve during vena cava occlusion. Biopsy samples were used for quantification of collagen volume fraction (CVF) and myocardial cell size.

Results: Six patients showed focal scar on late gadolinium enhancement. There was no significant difference in histological CVF between patients with and without focal myocardial scarring (p = 0.2). Septal ECV rather than native T₁ was a better surrogate marker for detecting histological CVF (r = 0.54; p = 0.02, and r = 0.44; p = 0.06, respectively). Global native T₁ and ECV, but not native T₁ and ECV in the septal myocardium, correlated well with the beta of passive LV stiffness, and had similar ability for predicting LV stiffness to histological CVF (r = 0.54, 0.50, 0.53, all p < 0.05, respectively). When the beta ≥0.054 was considered as moderately increased LV stiffness, global native T₁ ≥1,362 ms provided 88% sensitivity and 64% specificity with the C-statistic of 0.81 (95% confidence interval: 0.56 to 0.95).

Conclusions: Myocardial native T₁ provides comparable ability in predicting LV stiffness to ECV and histological CVF and may be useful for monitoring patients with HFpEF who have renal dysfunction, allergy to gadolinium, or wheezing that can simulate asthma. Our feasibility study shows the potential of native T₁ to allow for insight of heterogeneous pathophysiology and better risk stratification of HFpEF.