Análise da disfunção autonômica estudada pela variabilidade da frequência cardíaca correlaciona-se com a fibrose do músculo cardíaco em pacientes com Distrofia Muscular de Duchenne
USA – aumento da frequência cardíaca em repouso pode ocorrer por disfunção autonômica e pode ser observado em Duchenne. A disfunção autonômica relaciona-se com maior mortalidade. O teste da variabilidade da frequência cardíaca é simples e de fácil realização. Estudado em 74 pacientes com Duchenne ele apresentou uma correlação positiva com a presença de fibrose cardíaca identificada na ressonância magnética. Portanto a disfunção autonômica está presente em pacientes com Distrofia muscular de Duchenne e pode relacionar-se com a presença de fibrose do músculo cardíaco.
O resumo em inglês pode ser lido abaixo:
(Journal of the American College of Cardiology, Volume 61, Issue 10, Supplement, 12) Autonomic Dysfunction by Heart Rate Variability Analyses Correlates with Myocardial Fibrosis in Pediatric Duchenne Muscular Dystrophy
Tamara O. Thomas, John Jefferies, Angela Lorts, Jeffrey Anderson, Kan Hor, Zhiqian Gao, Elaine Urbina
Background: An elevated resting heart rate and cardiac failure are frequently observed during the natural history of Duchenne Muscular Dystrophy (DMD). We hypothesize that the elevated resting heart rate reflects autonomic dysfunction that can be identified by heart rate variability (HRV) analyses and this abnormal HRV correlates with abnormal cardiac magnetic resonance imaging (cMR) findings.
Methods: DMD patients (N=74) and controls (N=19) had anthropometric and blood pressure data collected with heart rate and HRV analyses via Holter monitoring. Time and frequency domain HRV parameters were calculated. Imaging data was taken from clinical cMR performed on DMD cases only. T-test was used to perform pair-wise comparison between groups. A p-value of <0.05 was used for statistical significance.
Results: DMD cases did not differ from controls in age, height, weight or blood pressure, however, they did differ in body mass index (17.8 + 2.5 years controls, 23 + 6.8 years cases). DMD cases had higher resting average heart rate (83.0 + 9.4 controls, 99.4 + 8.9 cases, p< 0.001). Among HRV variables, decreases were seen in: standard deviation of R to R intervals (p<0.001), the percent RR intervals differing by >50 ms from previous RR interval (p<0.001), the root-mean-square of successive differences of RR intervals (p<0.001), the standard deviation of the mean R to R segment (SDANN, p<0.001), Very Low Frequency (<0.04 Hertz), Low Frequency (0.04-0.15 Hertz) and High Frequency (0.15-0.4 Hertz). Of the HRV variables, SDANN most significantly correlates with positive late gadolinium enhancement on cMR (p 0.01). 19/74 DMD cases were on beta blocker (ββ) and the average resting heart rate differed significantly from those not on ββ (101.5 ± 6.9 no ββ, 93.5 ± yes ββ, p 0.009), however, there was no difference between the groups in HRV analyses. There was no difference in cardiac function by cMR between DMD cases with abnormal versus normal HRV or those on ββ versus not on ββ.
Conclusions: In conclusion, DMD patients have decreased overall HRV which correlates with early scar fibrosis by cMR. This autonomic dysfunction is associated with increased mortality and may be helpful in early risk stratification and medical therapy.
