The Controversial Epidemiology of Left Ventricular Dysfunction in Patients With Myotonic Dystrophy Type 1.
The Controversial Epidemiology of Left Ventricular Dysfunction in Patients With Myotonic Dystrophy Type 1 To the Editor In a recent issue of JAMA Cardiology, we read with great interest the report of Tanawuttiwat et al1 entitled "Left Ventricular Dysfunction and Conduction Disturbances in Patients With Myotonic Muscular Dystrophy Type I and II." In their well written research letter, the authors described the baseline prevalence and longitudinal incidence of conduction abnormalities and left ventricular dysfunction in a large single center cohort of patients with myotonic muscular dystrophy type 1 and type 2 (DM1 and DM2) The authors defined left ventricular dysfunction (LVD) as an ejection fraction less than 55% which differs from previous studies that used cutoffs of 50% or less. They reported a prevalence of left ventricular dysfunction at baseline in patients with DM1 of 11.8% with an incidence of 2% during the follow up period (mean, 5.76 years) The occurrence of left ventricular dysfunction in their DM1 cohort is much lower than those reported in previous studies.2 4 In particular, Bhakta et al2 showed an LVD prevalence of 18.9% in 180 patients with DM1 who underwent echocardiographic evaluation; Petri et al4 reported an LVD prevalence of 20.6% in 129 patients with DM1; and Groh et al3 showed a high incidence (12.5% of LVD in 406 patients with DM1 during a follow up period similar to that of the present study (mean, 5.7 years) According to previous reports,2 patients with DM1 with LVD were older, were more likely to be male, had longer baseline atrioventricular conduction time interval and intraventricular conduction time duration at study entry, had more incidence of atrial arrhythmias, and were more likely to have underwent device implantation. Compared with other large cohort studies of patients with DM1,3,4 the study population of the report by Tanawuttiwat et al1 has a similar mean age and percentage of male patients, higher percentage of atrial arrhythmias (22.7%1 vs 12.8%3 vs 11.4%4) and device implantation (20.5%1 vs 13.5%3 vs 3.9%4) consequently, we cannot explain the low occurrence of LVD. In conclusion, we suggest the authors consider a cutoff of left ventricular ejection fraction of 50% or less for defining LVD and evaluate the clinical and electrocardiographic characteristics of the DM1 subgroup with LVD to explain what may be the cause of this different occurrence of LVD in their study population.
JAMA cardiology