Evaluation of Index of Cardiac Electrophysiological Balance in Patients with Myotonic Dystrophy Type 1

Background: Myotonic dystrophy type 1(MD1), which is characterized by decreased muscle tone, progressive muscle weakness, and cardiac involvement, is an autosomal dominant and progressive congenital muscle disease. Cardiac involvement more often manifests as conduction abnormalities and arrhythmias (such as supraventricular or ventricular). Approximately one-third of MD1-related deaths occur due to cardiac causes. The index of cardiac-electrophysiological balance (ICEB) is a current parameter calculated as QT interval/QRS duration. The increase in this parameter has been associated with malignant ventricular arrhythmias. In this study, our aim was to compare the ICEB values of MD1 patients and the normal population.Material and method: A total of 62 patients were included in our study. They were divided into two groups -32 MD patients and 30 controls. The demographic, clinical, laboratory, and electrocardiographic parameters of the two groups were compared. Results: The median age of the study population was 24 (20-36 IQR), and 36 (58%) of these patients were female. Body mass index was higher in the control group (p = 0.037). While in the MD1 group creatinine kinase was significantly higher (p <0.001), In the control group creatinine, aspartate aminotransferase, alanine aminotransferase, calcium, and lymphocyte levels were significantly higher (p=0.031, p= 0.003, p=0.001, p=0.002, p=0.031, respectively). ICEB [3.96 (3.65-4.46) vs 3.74 (3.49-3.85) p=0.015] and corrected ICEB (ICEBc) [4.48 (4.08-4.92) vs 4.20 (4.03-4.51) p = 0.048] were significantly higher in the MD1 group.Conclusion: In our study, ICEB was found to be higher in MD1 patients than in the control group. Increased ICEB and ICEBc values in MD1 patients may precipitate ventricular arrhythmias in the future. Close monitoring of these parameters can be helpful in predicting possible ventricular arrhythmias and in risk stratification.