Structural myocardial involvement in adult patients with type 1 myotonic dystrophy

Echocardiographic Features of Cardiac Involvement in Myotonic Dystrophy 1: Prevalence and Prognostic Value

Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy in adults. Cardiac involvement is reported in 80% of cases and includes conduction disturbances, arrhythmias, subclinical diastolic and systolic dysfunction in the early stage of the disease; in contrast, severe ventricular systolic dysfunction occurs in the late stage of the disease. Echocardiography is recommended at the time of diagnosis with periodic revaluation in DM1 patients, regardless of the presence or absence of symptoms. Data regarding the echocardiographic findings in DM1 patients are few and conflicting. This narrative review aimed to describe the echocardiographic features of DM1 patients and their prognostic role as predictors of cardiac arrhythmias and sudden death.

Prevalence of Left Ventricular Systolic Dysfunction in Myotonic Dystrophy Type 1: A Systematic Review

Cardiac involvement is recorded in about 80% of patients affected by myotonic dystrophy type 1 (DM1). The prevalence of cardiac conduction abnormalities and arrhythmias has been well described. Data regarding the prevalence of left ventricle systolic dysfunction (LVSD) and heart failure (HF) are still conflicting. The primary objective of this review was to assess the prevalence of LVSD and HF in DM1. The secondary aim was to examine the association of clinical features with LVSD and to detect predisposing and influencing prognosis factors. A systematic search was developed in MEDLINE, EMBASE, Cochrane Register of Controlled Trials, and Web of Science databases to identify original reports between January 1, 2009, and September 30, 2017, assessing the prevalence of LVSD and HF in populations with DM1. Retrospective and prospective cohort studies and case series describing the prevalence of LVSD, as evaluated by echocardiography, and HF in patients with DM1 were included. Case reports, simple reviews, commentaries and editorials were excluded. Seven studies were identified as eligible, of which 1 was a retrospective population-based cohort study, and 6 were retrospective single-center-based cohort studies. Echocardiographic data concerning LV function were available for 647 of the 876 patients with DM1 who were included in the analysis. The prevalence of LVSD in patients with DM1, defined as LVEF < 55%, was 13.8%, 4.5-fold higher than in general population. Patients with DM1 and LVSD were older, were more likely to be male, had longer baseline atrioventricular and intraventricular conduction-time durations, had higher incidences of atrial arrhythmias, and were more likely to have undergone device implantation. Also, symptomatic HF is more prevalent in patients with DM1 despite their limited levels of physical activity. Further studies are needed to evaluate the prevalence of LVSD and HF in patients with DM1 and to investigate electrocardiographic abnormalities and other clinical features associated with this condition.

Pentamidine rescues contractility and rhythmicity in a Drosophila model of myotonic dystrophy heart dysfunction

Up to 80% of individuals with myotonic dystrophy type 1 (DM1) will develop cardiac abnormalities at some point during the progression of their disease, the most common of which is heart blockage of varying degrees. Such blockage is characterized by conduction defects and supraventricular and ventricular tachycardia, and carries a high risk of sudden cardiac death. Despite its importance, very few animal model studies have focused on the heart dysfunction in DM1. Here, we describe the characterization of the heart phenotype in a Drosophila model expressing pure expanded CUG repeats under the control of the cardiomyocyte-specific driver GMH5-Gal4. Morphologically, expression of 250 CUG repeats caused abnormalities in the parallel alignment of the spiral myofibrils in dissected fly hearts, as revealed by phalloidin staining. Moreover, combined immunofluorescence and in situ hybridization of Muscleblind and CUG repeats, respectively, confirmed detectable ribonuclear foci and Muscleblind sequestration, characteristic features of DM1, exclusively in flies expressing the expanded CTG repeats. Similarly to what has been reported in humans with DM1, heart-specific expression of toxic RNA resulted in reduced survival, increased arrhythmia, altered diastolic and systolic function, reduced heart tube diameters and reduced contractility in the model flies. As a proof of concept that the fly heart model can be used for in vivo testing of promising therapeutic compounds, we fed flies with pentamidine, a compound previously described to improve DM1 phenotypes. Pentamidine not only released Muscleblind from the CUG RNA repeats and reduced ribonuclear formation in the Drosophila heart, but also rescued heart arrhythmicity and contractility, and improved fly survival in animals expressing 250 CUG repeats.

Orthognathic Surgery in Patients With Congenital Myopathies and Congenital Muscular Dystrophies: Case Series and Review of the Literature

PURPOSE

This case series examined preoperative findings and the surgical, anesthetic, and postoperative management of 6 patients with congenital myopathies (CMs) and congenital muscular dystrophies (CMDs) treated at a tertiary medical institution with orthognathic surgery over 15 years to describe pertinent considerations for performing orthognathic surgery in these complex patients.

MATERIALS AND METHODS

According to the institutional review board-approved protocol, chart records were reviewed for all orthognathic surgical patients with a clinical, genetic, or muscle biopsy-proved diagnosis of CM or CMD.

RESULTS

Six patients (5 male, 1 female) qualified, and they were treated by 4 surgeons in the division of oral and maxillofacial surgery from 1992 through 2007. Average age was 19.5 years at the time of orthognathic surgery. Five patients had Class III malocclusions and 1 patient had Class II malocclusion. All 6 patients had apertognathia with lip incompetence. Nasoendotracheal intubation with a difficulty of 0/3 (0=easiest, 3=most difficult) was performed in all cases. Routine induction and maintenance anesthetics, including halogenated agents and nondepolarizing muscle relaxants, were administered without malignant hyperthermia. All 6 patients underwent Le Fort level osteotomies; 4 also had mandibular setback surgery with or without balancing mandibular inferior border osteotomies. Five patients required planned intensive care unit care postoperatively (average, 18.4 days; range, 4 to 65 days). Postoperative respiratory complications resulting in major blood oxygen desaturations occurred in 5 patients; 4 of these patients required reintubation during emergency code response. Five patients required extended postoperative intubation (average, 4.2 days; range, 3 to 6 days) and ventilatory support. Average hospital length of stay was 21.8 days (range, 6 to 75 days). Average postoperative follow-up interval was 29.8 weeks (range, 6 to 128 weeks).

CONCLUSIONS

Patients with CMs or CMDs often have characteristic dentofacial malocclusions that contribute to functional problems with feeding and drooling and psychosocial problems. Orthognathic surgery, usually bimaxillary, can be judiciously considered in these patients; these procedures typically require multidisciplinary pre- and postoperative evaluation and care over lengthy hospital stays with a high risk of respiratory complications that bear consideration in treatment planning.