Multiparametric CMR tissue characterization differentiates pathological from physiological phenotypes

An abnormal increase of cardiomyocyte mass of the left ventricle is observed in physiological and pathological phenotypes of hypertrophy.

To apply CMR tissue characterization using native T1/T2 and post-contrast T1 mapping and identify tissue phenotypes corresponding to physiological and pathological hypertrophy, in athletes and heart failure (HF), respectively.

187 individuals were prospectively enrolled, in 4 groups: Athletes (n=56, 32±13 years), HF with and without preserved ejection fraction (HFpEF: n=49, 62±12 years; HFrEF: n=49, 54±16 years, H2FpEF-score: 4.8 [3–9]), and healthy controls (n=33, 41±13.7 years). All participants underwent cardiopulmonary exercise testing and a multiparametric CMR study to assess morphology/function, T2, native T1, extracellular volume fraction (ECV), and intracellular lifetime of water (a marker of cardiomyocyte diameter). As expected, LVEF varied significantly among groups (Athletes: 64.7±6.1%, HFpEF: 59.3±10.7%, HFrEF: 29.4±8.5%, and controls: 65.4±4.3%, p<0.001) and was markedly reduced in HFrEF. Both LV mass index (Athletes: 64.1±15.8 g/m², HFpEF: 62.3±24 g/m², HFrEF: 79.5±36.7 g/m², and controls: 42±9.2 g/m², p<0.001) and cardiomyocyte mass index (calculated as (1 − ECV) x LV mass/BSA) (Athletes: 47.9±13.1 g/m², HFpEF: 42.2±17.2 g/m², HFrEF: 55.69±24.70 g/m², and controls: 30.7±6.9 g/m², p<0.001, Fig. 1A) were elevated in athletes and HF, compared to controls. Athletes and HFpEF patients showed concentric LV remodeling, while the eccentric LV remodeling was observed in HFrEF (Fig. 1B). In the HF groups NT-proBNP was elevated (Athletes: 34.6±16.8 ng/dL, HFpEF: 473.2±700.1 ng/dL, HFrEF: 1,365.3±1,772 ng/dL, and controls: 34.3±29 ng/dL, p<0.005), and adjusted maximum oxygen consumption was markedly reduced (Athletes: 49.4±9.3 mL/kg/min, HFpEF: 18.3±5.5 mL/kg/min, HFrEF: 17.1±4.2 mL/kg/min, and controls: 30.3±10.2 mL/kg/min, p<0.005). ECV was larger in both HF groups (athletes: 0.27±0.04, HFpEF: 0.31±0.05, HFrEF: 0.32±0.04, and controls: 0.26±0.02, p<0.001). The intracellular lifetime of water was longer among athletes compared to controls and shorter in HFrEF compared to HFpEF (Athletes: 0.17±0.07, HFpEF: 0.15±0.05, HFrEF: 0.13±0.05, and controls: 0.14±0.05, p<0.001). Native T1 was reduced in athletes compared to controls and elevated in the HF groups (Athletes: 1,173.4±63.2 ms, HFpEF: 1,262.8±62.4 ms, HFrEF: 1,275.1±59.9 ms, and controls: 1,212.78±76.01 ms, p<0.001). Lastly, the an increased T2 was indicative of edema in HF patients (Fig. 2).

In a prospective observational study with CMR T1/T2 mapping, physiological hypertrophy is characterized by increased cardiomyocyte diameter, normal ECV, and a decrease in native T1, due to the larger cardiomyocyte volume. In contrast, with pathological hypertrophy in HF, is associated with an increased and an above-normal native T1. Cardiomyocyte diameter appears reduced in HFrEF compared to HFpEF, reflecting the transition to an eccentric LV shape.

Type of funding sources: Public Institution(s). Main funding source(s): The São Paulo Research Foundation