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Chronic respiratory insufficiency is common in patients with myotonic dystrophy type 1 (DM1) and can be treated with noninvasive home mechanical ventilation (HMV). HMV is not always tolerated well resulting in low treatment adherence. We aimed to analyze if baseline respiratory characteristics such as pulmonary function, level of pCO 2 and presence of sleep apnea are associated with HMV treatment adherence in DM1 patients. Pulmonary function testing, polysomnography and blood gas measurement data of DM1 patients were retrospectively collected. Initiation of HMV and treatment adherence after one year was documented. Patients with low treatment adherence (average daily use of HMV <5 h) were grouped with patients that discontinued HMV and compared with patients with high treatment adherence (average daily use of HMV >5 h). HMV was initiated in 101 patients. After one year, 58 patients had low treatment adherence. There were no differences between the low and high treatment adherence group regarding the respiratory characteristics. None of the included predictors (gender, age, body mass index, cytosine-thymine-guanine repeat length, FVC, daytime pCO 2 , bicarbonate, nighttime pCO 2 , nighttime base excess, apnea-hypopnea index and mean saturation during sleep) was able to significantly predict high treatment adherence. In conclusion, the respiratory characteristics are not associated with treatment adherence with HMV in DM1 patients and cannot be used to identify patients at risk for low HMV treatment adherence., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests of personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Aims: To evaluate the clinical effectiveness of routine 24 h Holter monitoring to screen for conduction disturbances and arrhythmias in patients with myotonic dystrophy type 1 (DM1)., Methods and Results: A retrospective two-centre study was conducted including DM1-affected individuals undergoing routine cardiac screening with at least one 24 h Holter monitoring between January 2010 and December 2020. For each individual, the following data were collected: Holter results, results of electrocardiograms (ECGs) performed at the same year as Holter monitoring, presence of cardiac complaints, and neuromuscular status. Holter findings were compared with the results of cardiac screening (ECG + history taking) performed at the same year. Cardiac conduction abnormalities and/or arrhythmias that would have remained undiagnosed based on history taking and ECG alone were considered de novo findings. A total 235 genetically confirmed DM1 patients were included. Abnormal Holter results were discovered in 126 (54%) patients after a mean follow-up of 64 ± 28 months in which an average of 3 ± 1 Holter recordings per patient was performed. Abnormalities upon Holter mainly consisted of conduction disorders (70%) such as atrioventricular (AV) block. Out of 126 patients with abnormal Holter findings, 74 (59%) patients had de novo Holter findings including second-degree AV block, atrial fibrillation/flutter and non-sustained ventricular tachycardia. Patient characteristics were unable to predict the occurrence of de novo Holter findings. In 39 out of 133 (29%) patients with normal ECGs upon yearly cardiac screening, abnormalities were found on Holter monitoring during follow-up., Conclusion: Twenty-four hour Holter monitoring is of added value to routine cardiac screening for all DM1 patients., Competing Interests: Conflict of interest: B.G.M.V.E. reports grants from Spieren voor Spieren, grants from Prinses Beatrix Spierfonds, grants from Dutch FSHD foundation, grants from Marigold foundation, grants from Netherlands Organisation for Scientific Research (NWO), grants from The Netherlands Organisation for Health Research and Development (ZonMw), grants from Association Francaise contre les Myopathies, grants and personal fees from Fulcrum, personal fees from Facio, personal fees from Arrowhead, all payed to the institution and outside the submitted work. C.G.F. reports grants from European Union’s Horizon 2020 research and innovation programme Marie Sklodowska-Curie grant for PAIN-Net, molecule-to-man pain network (grant no. 721841), grants from Grifols and Lamepro for a trial on IVIg in small fibre neuropathy, grants from Prinses Beatrix Spierfonds, Steering committtees/advisory board for studies in small fibre neuropathy of Biogen/Convergence, Vertex, Lilly and OliPass, outside the submitted work. K.V. reports grants from Medtronic, Abbott and Biotronik, and a consultancy agreement with Medtronic, outside the submitted work. All remaining authors have declared no conflicts of interest., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Introduction/aims: Although the extent of muscle weakness and organ complications has not been well studied in patients with late-onset myotonic dystrophy type 1 (DM1), adult-onset DM1 is associated with severe muscle involvement and possible life-threatening cardiac and respiratory complications. In this study we aimed to compare the clinical phenotype of adult-onset vs late-onset DM1, focusing on the prevalence of cardiac, respiratory, and muscular involvement., Methods: Data were prospectively collected in the Dutch DM1 registry., Results: Two hundred seventy-five adult-onset and 66 late-onset DM1 patients were included. Conduction delay on electrocardiogram was present in 123 of 275 (45%) adult-onset patients, compared with 24 of 66 (36%) late-onset patients (P = .218). DM1 subtype did not predict presence of conduction delay (odds ratio [OR] 0.706; confidence interval [CI] 0.405 to 1.230, P = .219). Subtype did predict indication for noninvasive ventilation (NIV) (late onset vs adult onset: OR, 0.254; CI, 0.104 to 0.617; P = .002) and 17% of late-onset patients required NIV compared with 40% of adult-onset patients. Muscular Impairment Rating Scale (MIRS) scores were significantly different between subtypes (MIRS 1 to 3 in 66% of adult onset vs 100% of late onset [P < .001]), as were DM1-activ C scores (67 ± 21 in adult onset vs 87 ± 15 in late onset; P < .001)., Discussion: Although muscular phenotype was milder in late-onset compared with adult-onset DM1, the prevalence of conduction delay was comparable. Moreover, subtype was unable to predict the presence of cardiac conduction delay. Although adult-onset patients had an increased risk of having an NIV indication, 17% of late-onset patients required NIV. Despite different muscular phenotypes, screening for multiorgan involvement should be equally thorough in late-onset as in adult-onset DM1., (© 2022 The Authors. Muscle & Nerve published by Wiley Periodicals LLC.)

Background: Myotonic dystrophy type 1 (DM1) patients are at risk for metabolic abnormalities and commonly experience overweight and obesity. Possibly, weight issues result from lowered resting energy expenditure (EE) and impaired muscle oxidative metabolism., Objectives: This study aims to assess EE, body composition, and muscle oxidative capacity in patients with DM1 compared to age-, sex- and BMI-matched controls., Methods: A prospective case control study was conducted including 15 DM1 patients and 15 matched controls. Participants underwent state-of-the-art methodologies including 24 h whole room calorimetry, doubly labeled water and accelerometer analysis under 15-days of free-living conditions, muscle biopsy, full body magnetic resonance imaging (MRI), dual-energy x-ray absorptiometry (DEXA), computed tomography (CT) upper leg, and cardiopulmonary exercise testing., Results: Fat ratio determined by full body MRI was significantly higher in DM1 patients (56 [49-62] %) compared to healthy controls (44 [37-52] % ; p = 0.027). Resting EE did not differ between groups (1948 [1742-2146] vs (2001 [1853-2425>] kcal/24 h, respectively; p = 0.466). In contrast, total EE was 23% lower in DM1 patients (2162 [1794-2494] vs 2814 [2424-3310] kcal/24 h; p = 0.027). Also, DM1 patients had 63% less steps (3090 [2263-5063] vs 8283 [6855-11485] steps/24 h; p = 0.003) and a significantly lower VO2 peak (22 [17-24] vs 33 [26-39] mL/min/kg; p = 0.003) compared to the healthy controls. Muscle biopsy citrate synthase activity did not differ between groups (15.4 [13.3-20.0] vs 20.1 [16.6-25.8] μM/g/min, respectively; p = 0.449)., Conclusions: Resting EE does not differ between DM1 patients and healthy, matched controls when assessed under standardized circumstances. However, under free living conditions, total EE is substantially reduced in DM1 patients due to a lower physical activity level. The sedentary lifestyle of DM1 patients seems responsible for the undesirable changes in body composition and aerobic capacity.

Aims: The aim of this study was to determine electrocardiographic (ECG) criteria predicting abnormal infrahissian conduction in patients with myotonic dystrophy type 1 (DM1), as these criteria could be used to identify the need for an electrophysiological study (EPS)., Methods and Results: A retrospective multicentre study was conducted including DM1-affected individuals who underwent EPS between 2007 and 2018. For each individual, EPS indication, His-ventricle (HV) interval, resting ECG parameters prior to EPS, left ventricular ejection fraction (LVEF), neurological status, and DM1 DNA analysis results were collected. Electrocardiographic parameters of patients with a normal HV interval were compared with ECG parameters of patients with a prolonged HV interval. Logistic regression was performed to determine predictors for a prolonged HV interval of ≥70 ms on EPS and diagnostic accuracy of ECG parameters was ascertained. Among 100 DM1-affected individuals undergoing EPS, 47 had a prolonged HV interval. The sole presence of a PR interval >200 ms [odds ratio (OR) 8.45, confidence interval (CI) 2.64-27.04] or a QRS complex >120 ms (OR 9.91, CI 3.53-27.80) on ECG were independent predictors of a prolonged HV interval. The combination of both parameters had a positive predictive value of 78% for delayed infrahissian conduction on EPS. His-ventricle interval was independent of DM1 genetic mutation size, neuromuscular status, and LVEF., Conclusion: The combination of a prolonged PR interval and widened QRS complex on ECG accurately predicts abnormal infrahissian conduction on EPS in patients with DM1. These ECG parameters could be used as a screening tool to determine the need for referral to a specialized multidisciplinary neuromuscular team with EPS capacity., (© The Author(s) 2020. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Myotonic dystrophy type 1 (DM1) is caused by a CTG trinucleotide repeat expansion on chromosome 19q13.3. While DM1 premutation (36-50 repeats) and protomutation (51-80 repeats) allele carriers are mostly asymptomatic, offspring is at risk of inheriting expanded, symptom-associated, (CTG)n repeats of n > 80. In this study we aimed to evaluate the intergenerational instability of DM1 pre- and protomutation alleles, focussing on the influence of parental gender. One hundred and forty-six parent-child pairs (34 parental premutations, 112 protomutations) were retrospectively selected from the DM1 patient cohort of the Maastricht University Medical Center+. CTG repeat size of parents and children was determined by (triplet-primed) PCR followed by fragment length analysis and Southern blot analysis. Fifty-eight out of eighty-one (71.6%) paternal transmissions led to a (CTG)n repeat of n > 80 in offspring, compared with 15 out of 65 (23.1%) maternal transmissions (p < 0.001). Repeat length instability occurred for paternal (CTG)n repeats of n ≥ 45, while maternal instability did not occur until (CTG)n repeats reached a length of n ≥ 71. Transmission of premutations caused (CTG)n repeats of n > 80 in offspring only when paternally transmitted (two cases), while protomutations caused (CTG)n repeats of n > 80 in offspring in 71 cases, of which 56 (78.9%) were paternally transmitted. In conclusion, our data show that paternally transmitted pre- and protomutations were more unstable than maternally transmitted pre- and protomutations. For genetic counseling, this implies that males with a small DMPK mutation have a higher risk of symptomatic offspring compared with females. Consequently, we suggest addressing sex-dependent factors in genetic counseling of small-sized CTG repeat carriers.