Heart rate variability evaluation (HRV) is used to evaluate the prognosis in heart diseases at risk of cardiac mortality. Myotonic dystrophy (MD) is complicated by cardiac involvement. The purpose of the study was to evaluate the prognostic value of HRV determination for the stratification risk in MD.
60 asymptomatic patients, 26 men, 34 women, mean age 39±12 years at inclusion, had a MD. The studies were performed at inclusion and repeated 4±2.5 years later. Recording of 24 hour Holter monitoring and measurement of HRV in the time domain was calculated every 5minutes (Elatec system); standard deviation of mean RR intervals (SDNN) was determined. Left ventricular ejection fraction (LVEF) was evaluated by 2D echocardiography.
1 – General changes of studies: LVEF tended to decrease (63±8, 61.5±19.5 %) (p< 0.06). Mean values of SDNN did not change between the first inclusion (129±41 ms) and the last study (134±51ms).
2 – Modifications of studies according to initial data: LVEF was normal in 56 patients at inclusion. And decreased at second study 64±6 %, 61.5±7 % (p<0.01). LVEF was less than 50 % in 4 patients at inclusion and did not change at second study (43.5±7 vs 45±8 %). At inclusion, SDNN was normal in 42 patients (>100 ms) (147±35 ms) and was 148±52 at second study (NS); SDNN was < 100 ms in 2 of them at second study. SDNN was decreased (50 to 100 ms) in 17 patients at inclusion (mean 85±9 ms) and tended to increase at second study (97±34 ms) (NS).
3 – Follow-up: Initial SDNN could be predictive of the mortality: four patients died from heart and respiratory failure ; Three had an initial SDNN<100ms (3/17 ; 18 %) and the last one had a normal SDNN (1/42 ; 2 %) (p<0.08).
The modifications of HRV during the follow-up were not useful for the prediction of the adverse events in myotonic dystrophy, although LVEF decreased with time. However, a relatively low HRV at the first evaluation could be predictive of increasing mortality from 2 to 18 %.Le texte complet de cet article est disponible en PDF.