Skeletal Muscle Involvement in Patients With Truncations of Titin and Familial Dilated Cardiomyopathy

BACKGROUND

Genetic variants in titin (TTN) are associated with dilated cardiomyopathy (DCM) and skeletal myopathy. However, the skeletal muscle phenotype in individuals carrying heterozygous truncating TTN variants (TTNtv), the leading cause of DCM, is understudied.

OBJECTIVES

This study aimed to assess the skeletal muscle phenotype associated with TTNtv.

METHODS

Participants with TTNtv were included in a cross-sectional study. Skeletal muscle fat fraction was evaluated by magnetic resonance imaging (compared with healthy controls and controls with non-TTNtv DCM). Muscle strength was evaluated by dynamometry and muscle biopsy specimens were analyzed.

RESULTS

Twenty-five TTNtv participants (11 women, mean age 51 ± 15 years, left ventricular ejection fraction 45% ± 10%) were included (19 had DCM). Compared to healthy controls (n = 25), fat fraction was higher in calf (12.5% vs 9.9%, P = 0.013), thigh (12.2% vs 9.3%, P = 0.004), and paraspinal muscles (18.8% vs 13.9%, P = 0.008) of TTNtv participants. Linear mixed effects modelling found higher fat fractions in TTNtv participants compared to healthy controls (2.5%; 95% CI: 1.4-3.7; P < 0.001) and controls with non-TTNtv genetic DCM (n = 7) (1.5%; 95% CI: 0.2-2.8; P = 0.025). Muscle strength was within 1 SD of normal values. Biopsy specimens from 21 participants found myopathic features in 13 (62%), including central nuclei. Electron microscopy showed well-ordered Z-lines and T-tubuli but uneven and discontinuous M-lines and excessive glycogen depositions flanked by autophagosomes, lysosomes, and abnormal mitochondria with mitophagy.

CONCLUSIONS

Mild skeletal muscle involvement was prevalent in patients with TTNtv. The phenotype was characterized by an increased muscle fat fraction and excessive accumulation of glycogen, possibly due to reduced autophagic flux. These findings indicate an impact of TTNtv beyond the heart.

Clinical, Genetic, and Histological Characterization of Patients with Rare Neuromuscular and Mitochondrial Diseases Presenting with Different Cardiomyopathy Phenotypes

Cardiomyopathies are mostly determined by genetic mutations affecting either cardiac muscle cell structure or function. Nevertheless, cardiomyopathies may also be part of complex clinical phenotypes in the spectrum of neuromuscular (NMD) or mitochondrial diseases (MD). The aim of this study is to describe the clinical, molecular, and histological characteristics of a consecutive cohort of patients with cardiomyopathy associated with NMDs or MDs referred to a tertiary cardiomyopathy clinic. Consecutive patients with a definitive diagnosis of NMDs and MDs presenting with a cardiomyopathy phenotype were described. Seven patients were identified: two patients with ACAD9 deficiency (Patient 1 carried the c.1240C>T (p.Arg414Cys) homozygous variant in ACAD9; Patient 2 carried the c.1240C>T (p.Arg414Cys) and the c.1646G>A (p.Ar549Gln) variants in ACAD9); two patients with MYH7-related myopathy (Patient 3 carried the c.1325G>A (p.Arg442His) variant in MYH7; Patient 4 carried the c.1357C>T (p.Arg453Cys) variant in MYH7); one patient with desminopathy (Patient 5 carried the c.46C>T (p.Arg16Cys) variant in DES); two patients with mitochondrial myopathy (Patient 6 carried the m.3243A>G variant in MT-TL1; Patient 7 carried the c.253G>A (p.Gly85Arg) and the c.1055C>T (p.Thr352Met) variants in MTO1). All patients underwent a comprehensive cardiovascular and neuromuscular evaluation, including muscle biopsy and genetic testing. This study described the clinical phenotype of rare NMDs and MDs presenting as cardiomyopathies. A multidisciplinary evaluation, combined with genetic testing, plays a main role in the diagnosis of these rare diseases, and provides information about clinical expectations, and guides management.

2022 HRS expert consensus statement on evaluation and management of arrhythmic risk in neuromuscular disorders

This international multidisciplinary document is intended to guide electrophysiologists, cardiologists, other clinicians, and health care professionals in caring for patients with arrhythmic complications of neuromuscular disorders (NMDs). The document presents an overview of arrhythmias in NMDs followed by detailed sections on specific disorders: Duchenne muscular dystrophy, Becker muscular dystrophy, and limb-girdle muscular dystrophy type 2; myotonic dystrophy type 1 and type 2; Emery-Dreifuss muscular dystrophy and limb-girdle muscular dystrophy type 1B; facioscapulohumeral muscular dystrophy; and mitochondrial myopathies, including Friedreich ataxia and Kearns-Sayre syndrome, with an emphasis on managing arrhythmic cardiac manifestations. End-of-life management of arrhythmias in patients with NMDs is also covered. The document sections were drafted by the writing committee members according to their area of expertise. The recommendations represent the consensus opinion of the expert writing group, graded by class of recommendation and level of evidence utilizing defined criteria. The recommendations were made available for public comment; the document underwent review by the Heart Rhythm Society Scientific and Clinical Documents Committee and external review and endorsement by the partner and collaborating societies. Changes were incorporated based on these reviews. By using a breadth of accumulated available evidence, the document is designed to provide practical and actionable clinical information and recommendations for the diagnosis and management of arrhythmias and thus improve the care of patients with NMDs.

Targeting Myotonic Dystrophy Type 1 with Metformin

Myotonic dystrophy type 1 (DM1) is a multisystemic disorder of genetic origin. Progressive muscular weakness, atrophy and myotonia are its most prominent neuromuscular features, while additional clinical manifestations in multiple organs are also common. Overall, DM1 features resemble accelerated aging. There is currently no cure or specific treatment for myotonic dystrophy patients. However, in recent years a great effort has been made to identify potential new therapeutic strategies for DM1 patients. Metformin is a biguanide antidiabetic drug, with potential to delay aging at cellular and organismal levels. In DM1, different studies revealed that metformin rescues multiple phenotypes of the disease. This review provides an overview of recent findings describing metformin as a novel therapy to combat DM1 and their link with aging.

An overview of heart rhythm disorders and management in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is the most common adult form of muscular dystrophy, presenting with a constellation of systemic findings secondary to a CTG triplet expansion of the noncoding region of the DMPK gene. Cardiac involvement is frequent, with conduction disease and supraventricular and ventricular arrhythmias being the most prevalent cardiac manifestations, often developing from a young age. The development of cardiac arrhythmias has been linked to increased morbidity and mortality, with sudden cardiac death well described. Strategies to mitigate risk of arrhythmic death have been developed. In this review, we outline the current knowledge on the pathophysiology of rhythm abnormalities in patients with myotonic dystrophy and summarize available knowledge on arrhythmic risk stratification. We also review management strategies from an electrophysiological perspective, attempting to underline the substantial unmet need to address residual arrhythmic risks for this population.

Drosophila Heart as a Model for Cardiac Development and Diseases

The Drosophila heart, also referred to as the dorsal vessel, pumps the insect blood, the hemolymph. The bilateral heart primordia develop from the most dorsally located mesodermal cells, migrate coordinately, and fuse to form the cardiac tube. Though much simpler, the fruit fly heart displays several developmental and functional similarities to the vertebrate heart and, as we discuss here, represents an attractive model system for dissecting mechanisms of cardiac aging and heart failure and identifying genes causing congenital heart diseases. Fast imaging technologies allow for the characterization of heartbeat parameters in the adult fly and there is growing evidence that cardiac dysfunction in human diseases could be reproduced and analyzed in Drosophila, as discussed here for heart defects associated with the myotonic dystrophy type 1. Overall, the power of genetics and unsuspected conservation of genes and pathways puts Drosophila at the heart of fundamental and applied cardiac research.

2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients: Developed in collaboration with and endorsed by the Heart Rhythm Society (HRS), the American College of Cardiology (ACC), the American Heart Association (AHA), and the Association for European Paediatric and Congenital Cardiology (AEPC) Endorsed by the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS)

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

2021 PACES expert consensus statement on the indications and management of cardiovascular implantable electronic devices in pediatric patients

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

Nationwide incidence of myotonic dystrophy type 1 and the status of multi-organ involvement

PURPOSE

This study aimed to investigate the incidence of myotonic dystrophy type 1 (DM1) and the status of multi-organ involvement.

METHODS

This was a nationwide, population-based, cohort study using data from the Korean National Health Claims database. All patients with DM1 from the entire population aged ≤ 80 years were included. To identify possible systemic diseases along with DM1, we searched for concurrent codes for systemic diseases. To assess the recent status of systemic evaluation, concurrent codes for various diagnostic and treatment modalities were collected. Cumulative incidence during 2016-2019 was first evaluated then systemic evaluation for those patients was assessed during 2010-2019.

RESULTS

A total of 387 patients (47.8% men) during the recent 4-year study period (2016-2019) were diagnosed with DM1. The cumulative incidence in the general population was 0.77 (95% confidence interval: 0.76-0.77) per 100,000 persons. In newly developed incidental cases, cardiac involvement developed in 51.2%, pneumonia in 30.7%, diabetes in 26.9%, brain involvement in 18.1%, cataract in 13.7%, and cancers in 5.4% of total patients. Electrocardiography was performed in 93.8%, Holter in 33.9%, and echocardiography in 31.3% of the total patients for cardiac evaluation.

CONCLUSIONS

The incidence estimates of DM1 in the Asian population were lower than those of Caucasians. This study provides the real situation of screening and treatment for systemic diseases related to DM1. These detailed estimates could promote an understanding of the current disease status and allow for appropriate planning within the healthcare system.

Role of CMR Imaging in Diagnostics and Evaluation of Cardiac Involvement in Muscle Dystrophies

PURPOSE OF REVIEW

This review aims to outline the utility of cardiac magnetic resonance (CMR) in patients with different types of muscular dystrophies for the assessment of myocardial involvement, risk stratification and in guiding therapeutic decisions.

RECENT FINDINGS

In patients suffering from muscular dystrophies (MD), even mild initial dysfunction may lead to severe heart failure over a time course of years. CMR plays an increasing role in the diagnosis and clinical care of these patients, mostly due to its unique capability to precisely characterize subclinical and progressive changes in cardiac geometry, function in order to differentiate myocardial injury it allows the identification of inflammation, focal and diffuse fibrosis as well as fatty infiltration. CMR may provide additional information in addition to the physical examination, laboratory tests, ECG, and echocardiography. Further trials are needed to investigate the potential impact of CMR on the therapeutic decision-making as well as the assessment of long-term prognosis in different forms of muscular dystrophies. In addition to the basic cardiovascular evaluation, CMR can provide a robust, non-invasive technique for the evaluation of subclinical myocardial tissue injury like fat infiltration and focal and diffuse fibrosis. Furthermore, CMR has a unique capability to detect the progression of myocardial tissue damage in patients with a preserved systolic function.

2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consenus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology, (ACC) and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate follow-up in pediatric patients.

2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

Transcriptional signatures of synaptic vesicle genes define myotonic dystrophy type I neurodegeneration

Aim

To delineate the neurogenetic profiles of brain degeneration patterns in myotonic dystrophy type I (DM1).

Methods

In two cohorts of DM1 patients, brain maps of volume loss (VL) and neuropsychological deficits (NDs) were intersected to large‐scale transcriptome maps provided by the Allen Human Brain Atlas (AHBA). For validation, neuropathological and RNA analyses were performed in a small series of DM1 brain samples.

Results

Twofold: (1) From a list of preselected hypothesis‐driven genes, confirmatory analyses found that three genes play a major role in brain degeneration: dystrophin (DMD), alpha‐synuclein (SNCA) and the microtubule‐associated protein tau (MAPT). Neuropathological analyses confirmed a highly heterogeneous Tau‐pathology in DM1, different to the one in Alzheimer's disease. (2) Exploratory analyses revealed gene clusters enriched for key biological processes in the central nervous system, such as synaptic vesicle recycling, localization, endocytosis and exocytosis, and the serotonin and dopamine neurotransmitter pathways. RNA analyses confirmed synaptic vesicle dysfunction.

Conclusions

The combination of large‐scale transcriptome interactions with brain imaging and cognitive function sheds light on the neurobiological mechanisms of brain degeneration in DM1 that might help define future therapeutic strategies and research into this condition.

Predictors of respiratory decline in myotonic dystrophy type 1 (DM1): a longitudinal cohort study

We studied 33 patients affected by juvenile and adult myotonic dystrophy type 1 (DM1). The aim of the study was to assess clinical and laboratory parameters that could predict the requirement of noninvasive ventilation (NIV) in DM1. Secondary outcome was to assess the interplay between genetic profile, muscle impairment severity and presence of cardiac comorbidities.Patients with genetic diagnosis of DM1 were recruited. An abnormal trinucleotide repeat (CTG) expansion of dystrophy protein kinase gene (DMPK) on chromosome 19q13.3 was the prerequisite for inclusion. The number of triplet repeats was measured in genomic DNA to classify subjects. A multidisciplinary team evaluated the patients every 6-8 months up to 18 years with serial cardiological and respiratory function assessments. Neurological progression was monitored using a validated DM1-specific rating scale (MIRS). Independent variables considered for the study outcomes were gender, genetic status, age of presentation, MIRS scores, and results of pulmonary function tests (PFTs).Patients were 17 males (51.5%) and 16 females (48.5%). 16 cases were younger than mean age of 31.4 years, the remaining 17 were up to 65. 12 subjects (36.4%) underwent NIV during follow up. Cardiac comorbidities were detected in 63.6% of cases and in 91% of patients in NIV. Among PFTs, forced vital capacity (FVC) was a reliable indicator of respiratory decline. FVC values were significantly associated with clinical muscle severity assessed by MIRS.Severity of muscular impairment, CTG expansion size, age and presence of cardiac comorbidities predict respiratory impairment in DM1.

Predictors of prognosis in type 1 myotonic dystrophy (DM1): longitudinal 18-years experience from a single center

The aim of the study was to identify possible predictors of neurological worsening and need of non-invasive ventilation (NIV) in individuals affected by myotonic dystrophy type 1 (DM1), the most common form of adult-onset muscular dystrophy.

Cardiovascular manifestations of myotonic dystrophy

Patients with myotonic dystrophy, the most common neuromuscular dystrophy in adults, have a high prevalence of arrhythmic complications with increased cardiovascular mortality and high risk for sudden death. Sudden death prevention is central and relies on annual follow-up and prophylactic permanent pacing in patients with conduction defects on electrocardiogram and/or infrahisian blocks on electrophysiological study. Implantable cardiac defibrillator therapy may be indicated in patients with ventricular tachyarrhythmia.

Congenital myopathies are mainly associated with a mild cardiac phenotype

BACKGROUND

To evaluate the prevalence of cardiac involvement in patients with congenital myopathies and the association to specific genotypes.

METHODS

We evaluated patients with physical examination, electrocardiogram, echocardiography, and 48-h Holter monitoring. Follow-up was performed for major events.

RESULTS

We included 130 patients, 55 men (42%), with a mean age of 34 ± 17 years. A genetic diagnosis was established in 97 patients (75%). Right bundle branch block was observed in three patients: 2/34 patients with a ryanodine receptor 1 (RYR1) and 1/6 with a tropomyosin two gene (TPM2) gene mutation. Echocardiography showed left-ventricular hypertrophy in five patients: 2/17 and 3/34 patients with a Dynamin 2 (DNM2) and a RYR1 mutation, respectively. One patient with a myosin heavy-chain (MYH7) mutation had dilated cardiomyopathy and heart failure. On Holter monitoring, frequent ventricular premature contractions were observed in one patient with a DNM2 mutation. Two patients with a TPM2 and a RYR1 mutation, respectively, had a single short run of non-sustained ventricular tachycardia. Atrioventricular nodal re-entry tachycardia was observed in a 20-year-old man with an actin 1 gene mutation. During follow-up (median 8.4 years), four patients died, all of non-cardiac causes.

CONCLUSION

Congenital myopathies are generally associated with a mild cardiac phenotype. Our findings substantiate the literature and indicate that, except for patients with specific genotypes, such as MYH7 and TTN mutations, repeated cardiac assessments can be minimized, given a normal initial cardiac screening at time of diagnosis.

Non-invasive evaluation of the relationship between electrical and structural cardiac abnormalities in patients with myotonic dystrophy type 1

BACKGROUND

Cardiac involvement in myotonic dystrophy type 1 (MD1) includes conduction disease, arrhythmias, and left-ventricular (LV) systolic dysfunction leading to an increased sudden cardiac death risk. An understanding of the interplay between electrical and structural myocardial changes could improve the prediction of adverse cardiac events. We aimed to explore the relationship between signs of cardiomyopathy by conventional and advanced cardiovascular magnetic resonance (CMR), and electrical abnormalities in MD1.

METHODS

Fifty-seven MD1 patients (43 ± 13 years, 46% male) and 15 matched controls (41 ± 7 years, 53% male) underwent CMR including cine-imaging with feature-tracking strain analysis, late gadolinium enhancement (LGE), and native/post-contrast T1-mapping with extracellular volume calculation. Standard 12-lead and long-term ECG monitoring were performed as screening for rhythm and/or conduction abnormalities.

RESULTS

Abnormal ECGs were recorded in 40% of MD1; a pathologic CMR was found in 44%: 21% had an impaired LV-EF and 32% showed non-ischemic LGE. When looking at MD1 patients with available long-term ECG monitoring (n = 39), those with atrial fibrillation (Afib)/flutter(Afl) episodes had lower LV-EF (52 ± 7 vs. 60 ± 5%, p = 0.002), lower global longitudinal strain (- 17 ± 3 vs. - 20 ± 3%, p = 0.034), a trend to lower left atrial emptying fraction (LA-EF) (44 ± 14 vs. 55 ± 8%, p = 0.08), and higher prevalence of LGE (88% vs. 23%, p = 0.001) with an intramural (75% vs. 23%, p = 0.01) and septal (63% vs. 13%, p = 0.009) pattern. In a model including LV-EF (OR 0.8, 95% CI 0.7-1.0, p = NS) and LGE presence (OR 14.8, 95% CI 1.4-159.0, p = 0.026), only LGE was independently associated with the occurrence of Afib/Afl episodes.

CONCLUSION

Myocardial abnormalities depicted by non-ischemic LGE-CMR were the only independent predictor for the occurrence of Afib/Afl on ECG monitoring, previously shown to predict adverse cardiac events in MD1.

Survival patterns and cancer determinants in families with myotonic dystrophy type 1

BACKGROUND AND PURPOSE

Research indicates that patients with myotonic dystrophy type 1 (DM1) are at increased risk of cancer and early death. Family data may provide insights given DM1 phenotypic heterogeneity, the broad range of non-muscular manifestations and the usual delays in the diagnosis of DM1.

METHOD

Family history data were collected from 397 genetically and/or clinically confirmed DM1 patients (respondents) enrolled in the US or UK myotonic dystrophy registries. Standardized mortality ratios were calculated for DM1 first-degree relatives (parents, siblings and offspring) by their reported DM1 status (affected, unaffected or unknown). For cancer-related analyses, mixed effects logistic regression models were used to evaluate factors associated with cancer development in DM1 families, including familial clustering.

RESULTS

A total of 467 deaths and 337 cancers were reported amongst 1737 first-degree DM1 relatives. Mortality risk amongst relatives reported as DM1-unaffected was comparable to that of the general population [standardized mortality ratio (SMR) 0.82, P = 0.06], whilst significantly higher mortality risks were noted in DM1-affected relatives (SMR = 2.47, P < 0.0001) and in those whose DM1 status was unknown (SMR = 1.60, P < 0.0001). In cancer risk analyses, risk was higher amongst families in which the DM1 respondent had cancer (odds ratio 1.95, P = 0.0001). Unknown DM1 status in the siblings (odds ratio 2.59, P = 0.004) was associated with higher cancer risk.

CONCLUSION

There is an increased risk of death, and probably cancer, in relatives with DM1 and in those whose DM1 status is unknown. This suggests a need to perform a careful history and physical examination, supplemented by genetic testing, to identify family members at risk for DM1 and who might benefit from disease-specific clinical care and surveillance.

Twenty-four-hour ambulatory ECG monitoring relevancy in myotonic dystrophy type 1 follow-up: Prognostic value and heart rate variability evolution

BACKGROUND

Patient prognosis in type 1 myotonic dystrophy (DM1) is very poor. Annual 24-hour holter ECG monitoring is recommended but its relevance is debated. Main objective was to determine whether holter ECG parameters could predict global death in DM1 patients and secondarily to assess whether they could predict cardiovascular events and sudden cardiac death, to compare DM1 patients and healthy controls, and to assess their evolution in DM1 over a 5-year period.

METHODS

This retrospective study included genetically confirmed DM1. Primary endpoint was global death. Secondary endpoints were labeled "sudden cardiac death" which was a composite of sudden cardiac death, aborted sudden cardiac death, implantable cardioverter defibrillator therapy, sustained ventricular tachycardia, atrioventricular block grade 3, pause >3 s; and "cardiovascular events" which was a composite of all-cause mortality, pacemaker or cardioverter defibrillator implantation, sustained ventricular tachycardia, supraventricular tachycardia, hospitalization for acute cardiac cause and heart failure.

RESULTS

Forty-seven patients (22 women, 40 ± 13 years old) were included. Three (7%) DM1 patients died, 9 (19%) experienced "sudden cardiac death" endpoint and 21 (45%) experienced "cardiovascular event" endpoint during mean follow-up of 95 ± 22 months. None of holter ECG parameters were discriminant to predict death or secondary endpoints. Compared to healthy controls, DM1 patients had higher SDNN and LF/HF ratio. Finally, heart rate variability parameters remained stable over a mean interval of 61 ± 15 months excepting pNN50 which decreased significantly.

CONCLUSION

Results suggest that annually-repeated holter ECG in DM1 is not useful for stratifying risk of sudden death and cardiovascular outcomes.

Modeling of Myotonic Dystrophy Cardiac Phenotypes in Drosophila

After respiratory distress, cardiac dysfunction is the second most common cause of fatality associated with the myotonic dystrophy (DM) disease. Despite the prevalance of heart failure in DM, physiopathological studies on heart symptoms have been relatively scarce because few murine models faithfully reproduce the cardiac disease. Consequently, only a small number of candidate compounds have been evaluated in this specific phenotype. To help cover this gap Drosophila combines the amenability of its invertebrate genetics with the possibility of quickly acquiring physiological parameters suitable for meaningful comparisons with vertebrate animal models and humans. Here we review available descriptions of cardiac disease in DM type 1 and type 2, and three recent papers reporting the cardiac toxicity of non-coding CUG (DM1) and CCUG (DM2) repeat RNA in flies. Notably, flies expressing CUG or CCUG RNA in their hearts developed strong arrhythmias and had reduced fractional shortening, which correlates with similar phenotypes in DM patients. Overexpression of Muscleblind, which is abnormally sequestered by CUG and CCUG repeat RNA, managed to strongly suppress arrhythmias and fractional shortening, thus demonstrating that Muscleblind depletion causes cardiac phenotypes in flies. Importantly, small molecules pentamidine and daunorubicin were able to rescue cardiac phenotypes by releasing Muscleblind from sequestration. Taken together, fly heart models have the potential to make important contributions to the understanding of the molecular causes of cardiac dysfunction in DM and in the quick assessment of candidate therapeutics.

Neuromuscular Disease: Cardiac Manifestations and Sudden Death Risk

Cardiovascular complications of neuromuscular diseases disproportionately affect the cardiac conduction system. Cardiomyopathy and cardiac arrhythmias produce significant morbidity and mortality. Patients with neuromuscular diseases should be carefully and frequently evaluated for the presence of bradycardia, heart block, and tachyarrhythmias. Preemptive treatment with permanent pacemakers or implanted defibrillators is appropriate in patients with conduction system disease or who are at risk for ventricular arrhythmias.

Neuromuscular Disorders and the Role of the Clinical Electrophysiologist

Cardiac involvement is common and may be the presenting or predominant manifestation in a variety of neuromuscular disorders, most notably the inherited muscle disorders, or muscular dystrophies. Cardiac manifestations of the neuromuscular disorders result from pathological involvement of the myocardium and the cardiac conduction system, with resulting cardiomyopathy or rhythm disturbances including supraventricular arrhythmias, life-threatening ventricular arrhythmias, and sudden cardiac death. Many of these neuromuscular disorders are rare and may be unrecognized by even experienced specialists in internal and cardiovascular medicine. Furthermore, the initial cardiac manifestations in these patients are often asymptomatic. The goal of this investigation is to review the scope of cardiac conduction defects and rhythm disturbances in these disorders and to propose some practical recommendations for arrhythmia monitoring and management of these patients.

Incidence and predictors of sudden death, major conduction defects and sustained ventricular tachyarrhythmias in 1388 patients with myotonic dystrophy type 1

AIMS

To describe the incidence and identify predictors of sudden death (SD), major conduction defects and sustained ventricular tachyarrhythmias (VTA) in myotonic dystrophy type 1 (DM1).

METHODS AND RESULTS

We retrospectively enrolled 1388 adults with DM1 referred to six French medical centres between January 2000 and October 2013. We confirmed their vital status, classified all deaths, and determined the incidence of major conduction defects requiring permanent pacing and sustained VTA. We searched for predictors of overall survival, SD, major conduction defects, and sustained VTA by Cox regression analysis. Over a median 10-year follow-up, 253 (18.2%) patients died, 39 (3.6%) suddenly. Analysis of the cardiac rhythm at the time of the 39 SD revealed sustained VTA in 9, asystole in 5, complete atrioventricular block in 1 and electromechanical dissociation in two patients. Non-cardiac causes were identified in the five patients with SD who underwent autopsies. Major conduction defects developed in 143 (19.3%) and sustained VTA in 26 (2.3%) patients. By Cox regression analysis, age, family history of SD and left bundle branch block were independent predictors of SD, while age, male sex, electrocardiographic conduction abnormalities, syncope, and atrial fibrillation were independent predictors of major conduction defects; non-sustained VTA was the only predictor of sustained VTA.

CONCLUSIONS

SD was a frequent mode of death in DM1, with multiple mechanisms involved. Major conduction defects were by far more frequent than sustained VTA, whose only independent predictor was a personal history of non-sustained VTA. ClinicalTrials.gov no: NCT01136330.

Structural and electrical cardiac abnormalities are prevalent in asymptomatic adults with myotonic dystrophy

OBJECTIVE

Cardiac disease accounts for a large burden of premature mortality and morbidity in patients with type 1 myotonic dystrophy (MD). However, little is known about structural cardiac abnormalities particularly in asymptomatic patients with MD. We sought to describe the prevalence and extent of structural cardiac abnormalities in patients with MD and to assess their association with functional, electrical, biochemical and genetic disturbances.

METHODS

In this case-control study, 40 adults with MD who had no contraindications to cardiac MRI (CMR) were identified from the Grampian region genetic database. Forty-one age-and-gender-matched healthy volunteers were also recruited. All subjects underwent detailed assessment including CMR, echocardiography, electrocardiography, signal-averaged electrocardiography, Holter monitoring and quantification of serum B-type natriuretic peptide (BNP). Genetic testing of patients with MD was performed with quantification of CTG trinucleotide repeat sequences. Results of clinical, electrical, genetic and biochemical investigations were correlated with cardiac structural and functional abnormalities detected on CMR.

RESULTS

Electrical disturbances including prolongation of PR (187±29 vs 156±23 ms, p<0.001) and QRS intervals (99±11 vs 89±9 ms, p<0.001) were the most prevalent abnormality. Patients with MD had a significantly lower left ventricular (LV) mass (142±44 vs 172±73 g, p=0.03) and lower right ventricular (RV) ejection fraction (46±9 vs 50±7%, p=0.02) compared with controls, although LV ejection fraction was similar between the groups (58±8 vs 59±6%, p=0.34). LV non-compaction was also significantly more prevalent in the MD cohort (35% vs 12%, p=0.019). Late gadolinium enhancement was present in 13% of patients with MD. Muscular disability scores correlated with electrical changes (r=0.529, p<0.001); however, the number of CTG repeat sequences did not correlate with either electrical or structural abnormalities.

CONCLUSIONS

Patients with MD have a high prevalence of both electrical and structural abnormalities. These include reduced LV mass, impaired RV contractility, a high prevalence of LV non-compaction and myocardial fibrosis. These findings illustrate the potential utility of CMR detecting subclinical disease in otherwise asymptomatic patients with MD.

Symptomatic Trifascicular Block in Steinert's Disease: Is It Too Soon for a Pacemaker?

We report a case of a 62-year-old male with Steinert's disease who presented with progressive intermittent episodes of lightheadedness five years after he was diagnosed with the disease. On evaluation, he developed a new onset trifascicular block (first degree atrioventricular block, new onset right bundle branch block, and left anterior fascicular block). A dual chamber pacemaker was inserted and lightheadedness improved significantly.

Clinical, pathological and genetic characteristics of a pedigree with myotonic dystrophy type 1

The aim of the present study was to investigate the clinical, pathological and molecular genetic characteristics of a pedigree with myotonic dystrophy type 1 (DM1). A series of clinical data from a pedigree with DM1 were collected. Muscle biopsy revealed a typical nuclear ingression within numerous muscle fibers following hematoxylin and eosin staining. Genomic DNA was extracted from the venous blood of two patients and the triplet-primed polymerase chain reaction method was performed to amplify the dystrophia myotonic protein kinase (DMPK) gene. The amplified products were subjected to gene sequencing by capillary fluorescence electrophoresis, and a pathogenic mutation in the DMPK gene comprising >50 cytosine-thymine-guanine repeat sequences was found. DM1 includes multi-system damage, as well as skeletal muscle involvement, and can affect the central nervous system, endocrine glands, skin and heart. A skeletal muscle biopsy and genetic testing can confirm the diagnosis and clarify the severity of the disease. In addition, it is necessary to distinguish DM1 from DM2.

Uncovering the Role of Hypermethylation by CTG Expansion in Myotonic Dystrophy Type 1 Using Mutant Human Embryonic Stem Cells

CTG repeat expansion in DMPK, the cause of myotonic dystrophy type 1 (DM1), frequently results in hypermethylation and reduced SIX5 expression. The contribution of hypermethylation to disease pathogenesis and the precise mechanism by which SIX5 expression is reduced are unknown. Using 14 different DM1-affected human embryonic stem cell (hESC) lines, we characterized a differentially methylated region (DMR) near the CTGs. This DMR undergoes hypermethylation as a function of expansion size in a way that is specific to undifferentiated cells and is associated with reduced SIX5 expression. Using functional assays, we provide evidence for regulatory activity of the DMR, which is lost by hypermethylation and may contribute to DM1 pathogenesis by causing SIX5 haplo-insufficiency. This study highlights the power of hESCs in disease modeling and describes a DMR that functions both as an exon coding sequence and as a regulatory element whose activity is epigenetically hampered by a heritable mutation.

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We identify a disease-associated, differentially methylated region in DM1 hESCs

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CTG expansion size correlates with the degree of methylation specifically in DM1 hESCs

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DMPK hypermethylation hampers the activity of a regulatory element for SIX5

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DM1 hESCs provide an opportunity to study diseased cardiomyocytes in vitro

Neurologic disease with pregnancy and considerations for the obstetric anesthesiologist

Women with neurologic conditions present a challenge during pregnancy and in the peripartum period. Given the low prevalence of these diseases during pregnancy, most management decisions are guided by retrospective reviews and case reports. This article reviews current literature for some of the more common or complex neurologic conditions affecting pregnancy with special consideration for anesthetic management. In particular, epilepsy; multiple sclerosis; primary intracranial hypertension; secondary intracranial hypertension-Arnold-Chiari malformations and intracranial neoplasms; spinal cord injury; neuromuscular junction disorders-myasthenia gravis; and hereditary neuromuscular disorders-myotonic dystrophy and spinal muscular atrophy will be discussed. By increasing understanding of anesthetic issues for parturients with neurologic disease, providers may more effectively anticipate anesthetic considerations, thereby optimizing care plans.