Abstract Background Myotonic dystrophy type I (MD) is an autosomal dominant neuromuscular disorder with frequent cardiac involvement that is key for the patient prognosis. Cardiac conduction disorders are common in this population; however, there are no well-defined clinical parameters, which can predict the developing of ventricular arrhythmias (VA). Purpose We aimed to assess clinical, electrocardiographic and cardiac imaging parameters to identify those MD patients who are at increased risk of VA and sudden cardiac death at follow-up. Methods Several clinical, ECG and echocardiographic parameters from patients with MD type I diagnosed in our center from 1990 to 2024 were retrospectively collected. We compared the baseline and follow-up characteristics of patients that developed VA, with patients that were free of VA during the study period. Univariate analysis of qualitative variables were performed using Fisher test. We used t-Student for quantitative variables with normal distribution, and U-Mann Whitney for those with non-normal distribution. For multivariate analysis, we applied logistic regression adjusted by age and sex. Results 44 patients with MD were included. 29 (65,9%) were male, and mean age at disease diagnosis was 34,7±13,3 years. 8 patients (18,1%) received an ICD (62% secondary prevention), and 20 (45,4%) a conventional pacemaker during follow-up. 10 (4,4%) patients developed ventricular arrhythmias (both sustained and non-sustained; VA group) and 34 individuals did not develop any type of VA (non-VA group). PR interval duration in the VA group was 217,5±9,3 ms, and 192,15±29,5 ms in the non-VA group (p=0,03); (Figure 1). In the VA group there was a non-significant trend to wider QRS interval at diagnosis (111,9±20 vs 99,8±14,5; p=0,08). There were also no statistical significance in the grade of PR and QRS interval length increasing (delta PR and delta QRS), during follow-up between groups. The prevalence of syncope was significantly higher in the VA group (60% vs 14,7%; p=0,008). CTG triplet expansion was higher in the VA group (907,1±566,5 vs 505,4±490,6), although without statistical significance (p=0,08). VA group patients showed also a higher degree of neuromuscular impairment than patients in non-VA group (40% vs 20,59%; p=0,237). The multivariate analysis (Figure 2), showed that syncopal events were significantly associated to the development of VA (OR=9,45; p=0,028). The patients with PR interval duration 200 ms were more prone to develop ventricular arrhythmias too (OR=10,53; p=0,068). Conclusion In patients with MD type I syncopal events are significantly associated with an increased risk of developing VA during follow-up. Additionally, a prolonged PR interval and greater CTG expansion showed a trend toward predicting the occurrence of these arrhythmias. These findings could lead to early identifying patients at higher risk of suffering VA.
Zabaleta et al. (Sat,) studied this question.