Increased blood pressure and BMI in relation to cardiomyopathy in Duchenne muscular dystrophy

Abstract

Objective: Cardiomyopathy in Duchenne muscular dystrophy (DMD) is characterized by progressive left ventricle dysfunction (LVD). LVD is worsened by increased left ventricular afterload. We studied factors influencing this afterload: systolic blood pressure (SPB), obesity, steroid use and cardiac medication (CM) in DMD patients. Subsequently, we studied the relation between these factors and LV deformation in a subset of young patients without clinical cardiomyopathy. Methods: SBP measurements were evaluated retrospectively from 285 visits of 65 patients aged 4–18 years between February 2003 and December 2016. Values were normalized for age and length using Z-scores (Z-SBP). Age was divided in 14 groups, from 4–5 to 17– 18 years. A linear mixed model was used to analyse longitudinal correlations between Z-SBP and body mass index (BMI), steroid use, age, ambulatory status and CM use. In a subset of 36 patients <11 years, LV deformation, defined by global longitudinal strain (GLS), was quantified with speckle tracking imaging in the apical 4-chamber view of transthoracic echocardiograms. Multiple linear regression was used to assess relations between GLS, BMI, SBP, age and years on steroids. Results: Median follow-up time was 5 years (range 1–12). Z-SBP was significantly elevated in all age groups under 14 years (p < 0.016) and 15–16 years (p = 0.014). Prevalence of hypertension (Z-SBP ≥ 1.65) ranged from 22–39%. Z-SBP correlated positively with BMI (p = 0.001), and negatively with CM use over time (p = 0.017). Mean age of the younger cohort was 8.5 (±1.5) years. Here, reduced GLS was associated with increased BMI (p = 0.004, R2 = 30.8%), but not with other variables. Conclusion: SBP was significantly elevated in the majority of DMD age groups below 18 years. Z-SBP correlated positively with BMI over time. BMI was also associated with decreased LV deformation in younger patients. Prospective studies are needed for confirmation, and to assess the relevance of earlier management of these factors in DMD.