Does Ethnicity Influence the Relationship Between Aldosterone and Early Sign of Cardiac Remodelling? A Cardiovascular Magnetic Resonance Study

Objective: Native T1 and T2 myocardial mapping techniques by cardiac magnetic resonance (CMR) offer quantitative assessments of myocardium composition with T1 manly related to tissue fibrosis and T2 to myocardial oedema. It has been proposed that compared to white individuals, in black subjects water retention/volume expansion driven by aldosterone could be a more prominent contributing factor to hypertension and hypertensive heart disease. Therefore, we aimed to assess differences in myocardial tissue characterization and its relation with plasma aldosterone concentration (PAC) in a dual ethnic cohort of subjects with hypertension. Design and method: Subjects with hypertension recruited from the outpatient service at Guys and St Thomas’ Hospital (UK) underwent a single study visit in which anthropometric measurements, blood tests and a multi-parametric CMR were performed. The latter included quantification of left ventricular mass indexed (LVMI) and native T1 and T2 relaxation times. Results: A dual ethnic cohort of 107 subjects (age 45±13 years (mean±SD)), 57% male were recruited. Most subjects were non-smokers (79.5%), average BMI 29.3±5.5 Kg/m 2 ; 11% had diabetes, 23% dyslipidaemia and 2.5% a previous cardiovascular event. Black subjects (n=64) had higher PAC compared to white individuals (511±339 pmol/L vs 384.3±292 pmol/L, p=0.036) but age, BMI and blood pressure (BP) values were similar (47±14 years vs 43±12 years, 29.7±4 Kg/m 2 vs 28.7±7 Kg/m 2 , 150±22 mmHg vs 148±23 mmHg for systolic BP respectively; all P >0.05). T1 relaxation time was similar between black and white subjects, however LVMI and T2 relaxation time were significantly higher in black subjects (66.7±24.9 g/m 2 vs 55.2±10.4 g/m 2 and 47.0±2.2 ms vs 45.7±2.2 ms respectively; both P<0.05). In the entire population PAC was significantly correlated with T2 mapping (Beta=0.198, P=0.025) and LVMI (Beta=0.296, P=0.016) but not T1. We also found a significant interaction between PAC, T2 mapping and ethnicity. Conclusions: The highest T2 relaxation time in black hypertensive likely reflects myocardial inflammation and ethnic related differences in myocardial tissue characterization could be related to PAC. Further studies are warranted to elucidate the potential pathophysiological mechanisms.