Introduction: Myotonic dystrophy type 1 (MD1) is the most common muscular dystrophy of adult life. Cardiac involvement is characterized by disorders of atrioventricular conduction, ventricular arrhythmias, and sudden death. Heart rate turbulence (HRT) is a noninvasive risk predictor in patients affected by ischemic heart disease. The aim of our study is to assess the prognostic value of HRT in MD1 patients.
Methods and results: We performed HRT analysis by 24-hour Holter recording to calculate turbulence onset (TO) and turbulence slope (TS) in 29 MD1 patients (mean age 52 +/- 10 years), and in 30 patients (mean age 52 +/- 13 years) with frequent ventricular arrhythmias and structurally normal heart (VANH). An electrophysiological study (EPS) tested ventricular arrhythmias inducibility in 22 MD1 patients. TO was significantly different between MD1 and VANH patients (-1.66 +/- 2.04 and -2.98 +/- 1.79%, respectively, P 0.01), while no difference was observed in TS between MD1 and VANH patients (11.12 +/- 6.46 and 9.12 +/- 6 msec/beat, respectively). On EPS, sustained ventricular arrhythmias (SVA) were induced in six MD1 patients. TO was significantly different in inducible MD1 patients (0.88 +/- 1.95%), as compared with both noninducible (-2.49 +/- 1.43%, P < 0.001) or no eligible to EPS (-1.93 +/- 1.63%, P < 0.005) MD1 patients and to VANH patients (-2.98 +/- 1.79%, P < 0.001).
Conclusions: An impairment of TO, a measure of HRT, suggesting impaired cardiac parasympathetic activity, may be a useful, noninvasive predictor of arrhythmic risk in MD1 patients.