Age, conduction defects and restrictive lung disease independently predict cardiac events and death in myotonic dystrophy

An evaluation of 24 h Holter monitoring in patients with myotonic dystrophy type 1

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.

Predicting the CTG Repeat Size from a Single Spirometry Test Performed at Any Time during the Disease Course of Myotonic Dystrophy Type 1

Objective In myotonic dystrophy type 1 (DM1), the CTG repeat size in the dystrophia myotonica protein kinase gene has been shown to correlate with disease severity and is a potential predictive marker for respiratory decline. However, genetic testing can be challenging in some clinical situations. We developed a simple formula for estimating the CTG repeat size using a single spirometry test in patients with DM1. Methods In this single-center retrospective study, we reviewed 50 consecutive patients with genetically confirmed DM1 whose follow-up visits were at our hospital. The patients were randomly assigned to training and test analysis subsets. By applying a linear mixed model to the longitudinal spirometry results of the training set, we calculated the fixed effects on the annual respiratory decline. Subsequently, we derived a prediction formula to calculate the repeat size that incorporated %vital capacity (%VC) and the patient's age at the time of the spirometry evaluation; the results were validated by the test set. Results A total of 157 spirometry tests were recorded. The fixed effects on the annual %VC decline were <img align="middle" src="./Graphics/abst-61_2281_1.jpg"/>=-0.90. The derived formula [repeat size=-16.8× (age+%VC/0.90) +2663] had a moderate predictive performance with a mean coefficient of determination <img align="middle" src="./Graphics/abst-61_2281_2.jpg"/> of 0.41. Conclusion The CTG repeat size in patients with DM1 can be potentially predicted using a simple formula based on a single spirometry test conducted at any time over the disease course. It can be useful as a supportive tool for advance care planning when genetic testing is not available.

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.

METHODS

A retrospective observational cohort study was undertaken. Thirty-three patients with genetic diagnosis of DM1 were followed at our Neuromuscular unit in Modena. Abnormal trinucleotide repeat (CTG) expansion of dystrophy protein kinase gene (MDPK) on chromosome 19q 13.3 was the prerequisite for inclusion. The number of CTG repeats was determined. All the participants were older than 14 at the time of enrolment, therefore they could be included into the juvenile or adult form of the disease. Participants were neurologically evaluated every 6-8 months up to 18 years. Neurological impairment was assessed by Muscular Impairment Rating (MIRS), Medical Research Council (MRC), and modified Rankin (mRS) scales. The independent variables considered for prognosis were age at first evaluation, duration of the disease, CTG repeat number, gender, and presence of cardiac and vascular morbidities.Male patients were 51.5% and female patients 48.5%. Sixteen patients were younger than the mean age of 30.1 years, while the remaining 17 were up to 65. Twelve subjects (36.4%) underwent NIV before the end of follow-up. Muscle force and disability scores showed statistically significant deterioration (p < 0.001) during follow-up. The worsening was significantly higher among patients carrying higher number of CTG repeats and of younger age. The presence of cardio-vascular involvement has significant impact on neurological and respiratory progression.Neurological worsening is predicted by CTG expansion size, young age and presence of cardio-vascular morbidities.

Multisystemic Impairments in 93 Chinese Patients With Myotonic Dystrophy Type 1

Background: Myotonic dystrophy type 1 (DM1) is an autosomal dominant neuromuscular disease characterized by muscle weakness and multisystemic impairments, which significantly impact the quality of life. There is currently an increasing consensus on the necessity of a multidisciplinary assessment in patients with DM1, to improve the management of the disease.

Methods: To analyze the prevalence and pairwise relationships between various organs involved, we performed a retrospective study by reviewing demographic and clinical information of DM1 patients including age, disease duration, clinical history, muscular impairment rating scale score (MIRS), results of blood biochemistry, electrocardiogram, echocardiography, and ophthalmologic examination.

Results: Ninety three DM1 patients (60 males and 33 females), aged 34.7 ± 12.6 (mean ± standard deviation) years were recruited. Of which, two congenital cases were of maternal and paternal inheritance, respectively. In the other 91 patients, cataract was found in 44.1% of patients, followed by hypogonadism (40.8%), frontal balding (40.7%), and cardiac abnormalities (34.5%). Thyroid dysfunction and insulin insensitivity were relatively uncommon. Age (p < 0.001) is independently correlated with cataract, and MIRS correlates positively with cardiac abnormalities (p = 0.005) and frontal balding (p = 0.015). Male patients more frequently had frontal balding (Risk ratio, 3.98; 95% confidence interval, 1.493–10.611) compared with female patients. Male patients with cataract presented more frequent cardiac abnormalities (Risk ratio, 4.40; 95% confidence interval, 1.055–18.358) compared with non-cataract male patients. Hypogonadism in male patients was characterized as decreased testosterone level, accompanied by elevated levels of luteinizing hormone and follicle-stimulating hormone.

Conclusions: In Chinese patients with DM1, we conclude that (1) cataract, hypogonadism, frontal balding and cardiac abnormalities are frequently observed; (2) age is an independent indicator to cataract and MIRS is the only predictor for cardiac abnormalities and frontal balding; (3) a positive correlation between ophthalmologic and cardiac impairments in male patients is found; (4) endocrine abnormalities show diverse manifestations and hormone tests are recommended; (5) particular attention should be given to patients with older age and higher MIRS score.

Respiratory dysfunction in myotonic dystrophy type 1: A systematic review

Myotonic dystrophy type 1 (DM1) is one of the most common muscular dystrophies in adults. This review summarises the current literature regarding the natural history of respiratory dysfunction in DM1, the role of central respiratory drive and peripheral respiratory muscle involvement and its significance in respiratory function, and investigates the relationship between genetics (CTG repeat length) and respiratory dysfunction. The review included all articles that reported spirometry on 10 or more myotonic dystrophy patients. The final review included 55 articles between 1964 and 2017. The major conclusions of this review were (1) confirmation of the current consensus that respiratory dysfunction, predominantly a restrictive ventilatory pattern, is common in myotonic dystrophy and is associated with alveolar hypoventilation, chronic hypercapnia, and sleep disturbance in the form of sleep apnoea and sleep related disordered breathing; (2) contrary to commonly held belief, there is no consensus in the literature regarding the relationship between CTG repeat length and severity of respiratory dysfunction and a relationship has not been established; (3) the natural history and time-course of respiratory functional decline is very poorly understood in the current literature; (4) there is a consensus that there is a significant involvement of central respiratory drive in this alveolar hypoventilation however the current literature does not identify the mechanism for this.

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.

Myotonic dystrophy and the heart: A systematic review of evaluation and management

Myotonic dystrophy (MD) is a multisystem, autosomal dominant disorder best known for its skeletal muscle manifestations. Cardiac manifestations arise as a result of myocardial fatty infiltration, degeneration and fibrosis and present most commonly as arrhythmias or conduction disturbances. Guidelines regarding the optimal cardiac management of patients with MD are lacking. The present article provides a summary of the pathophysiology of cardiac problems in patients with MD and provides a practical approach to contemporary cardiac monitoring and management of these patients with a focus on the prevention of complications related to conduction disturbances and arrhythmias.

METHODS

A literature search was performed using PubMed and Medline. The keywords used in the search included "myotonic dystrophy", "cardiac manifestations", "heart", "arrhythmia", "pacemaker" and "defibrillator", all terms were used in combination. In addition, "myotonic dystrophy" was searched in conjunction with "electrophysiology", "electrocardiogram", "echocardiograph", "signal averaged electrocardiograph", "magnetic resonance imaging" and "exercise stress testing". The titles of all the articles revealed by the search were screened for relevance. The abstracts of relevant titles were read and those articles which concerned the cardiac manifestations of myotonic dystrophy or the investigation and management of cardiac manifestations underwent a full manuscript review.

Sleep disordered breathing in young boys with Duchenne muscular dystrophy

OBJECTIVES

To describe sleep-disordered breathing (SDB) in young boys with Duchenne muscular dystrophy (DMD) and its relationship with pulmonary function tests (PFTs).

STUDY DESIGN

This retrospective study examined diagnostic polysomnogram and PFT data of boys younger than 18 years with DMD and treated with steroids. Spirometry, respiratory muscle strength, body mass index (BMI), sleep architecture variables, and indices of SDB were analyzed. We examined the effect of PFT measures on the risk of each type of respiratory event using logistic regression and have reported results as OR (95% CI).

RESULTS

Subjects included 110 boys with DMD, mean age 11.5 (5.6-17.9) years. Mean (±SD) percent forced vital capacity predicted was 79.5% ± 29.1%. Mean BMI for all subjects was 21.9 ± 7.0 kg/m(2), and mean BMI z-score was 0.65 ± 1.93. Seventy (63.6%) subjects had obstructive sleep apnea; 37 (33.6%) subjects had central sleep apnea; 18 (17%) subjects had hypoventilation. Median (IQR) Apnea Hypopnea Index was 2.9 (1.6-6.9) and median Obstructive Index was 1.5 (0.5-3.8). Obstructive Index during rapid eye movement sleep positively correlated with BMI (r = 0.33, P = .002), BMI z-score (r = 0.22, P = .04), and age (r = 0.31, P = .004). Lower forced vital capacity was associated with increased risk of hypoventilation (OR 0.8, P = .001).

CONCLUSION

SDB is common in young boys with DMD treated with steroids. It is manifest with rapid eye movement-obstructive sleep apnea, often severe, and strongly influenced by BMI.

Prevalence of type 1 Brugada ECG pattern after administration of Class 1C drugs in patients with type 1 myotonic dystrophy: Myotonic dystrophy as a part of the Brugada syndrome

BACKGROUND

Both type 1 myotonic dystrophy (MD1) and Brugada syndrome (BrS) may be complicated by conduction disturbances and sudden death. Spontaneous BrS has been observed in MD1 patients, but the prevalence of drug-induced BrS in MD1 is unknown.

OBJECTIVE

The purpose of this study was to prospectively assess the prevalence of type 1 ST elevation as elicited during pharmacologic challenge with Class 1C drugs in a subgroup of MD1 patients and to further establish correlations with ECG and electrophysiologic variables and prognosis.

METHODS

From a group of unselected 270 MD1 patients, ajmaline or flecainide drug challenge was performed in a subgroup of 44 patients (27 men, median age 43 years) with minor depolarization/repolarization abnormalities suggestive of possible BrS. The presence of type 1 ST elevation after drug challenge was correlated to clinical, ECG, and electrophysiologic variables.

RESULTS

Eight of 44 patients (18%) presented with BrS after drug challenge. BrS was seen more often in men (26% vs 6%, P = .09) and was related to younger age (35 vs 48 years, P = .07). BrS was not correlated to symptoms, baseline ECG, HV interval, results of signal-averaged ECG, or abnormalities on ambulatory recordings. MD1 patients with BrS had longer corrected QT intervals, greater increase in PR interval after drug challenge, and higher rate of inducible ventricular arrhythmias (62% vs 21%, P = .03). Twelve patients were implanted with a pacemaker and 5 with an implantable cardioverter-defibrillator. Significant bradycardia did not occur in any patients, and malignant ventricular arrhythmia never occurred during median 7-year follow-up (except 1 hypokalemia-related ventricular fibrillation).

CONCLUSION

BrS is elicited by a Class 1 drug in 18% of MD1 patients presenting with minor depolarization/repolarization abnormalities at baseline, but the finding seems to be devoid of a prognostic role.

Supine changes in lung function correlate with chronic respiratory failure in myotonic dystrophy patients

Quality of life and prognosis of patients with myotonic dystrophy type 1 (MD1) often depend on the degree of lung function impairment. This study was designed to assess the respective prevalence of ventilatory restriction, hypoxaemia and hypercapnia in MD1 patients and to determine whether postural changes in lung function could contribute to the early diagnosis of poor respiratory outcome. Fifty-eight patients (42.6±12.9 years) with MD1 were prospectively evaluated from April 2008 to June 2010 to determine their supine and upright lung function and arterial blood gases. The prevalence of ventilatory restriction was 36% and increased with the severity of muscular disability (from 7.7% to 70.6%). The prevalence of hypoxaemia and hypercapnia was 37.9% and 25.9%, respectively. Multiple regression analysis showed that the supine fall in FEV1 was the only variable associated with ventilatory restriction, hypoxaemia and hypercapnia. Our data indicate that supine evaluation of lung function could be helpful to predict poor respiratory outcome, which is closely correlated with hypoxaemia and/or hypercapnia.

Atrial flutter or fibrillation is the most frequent and life-threatening arrhythmia in myotonic dystrophy

BACKGROUND

Several arrhythmias were reported in myotonic dystrophy (MD).

OBJECTIVES

To evaluate the prevalence of atrial fibrillation (AF) and atrial flutter (AFL) in MD and the clinical consequences.

METHODS

One hundred sixty-one patients, mean age 41 ± 14 years, were referred for a type 1 MD. All patients were asymptomatic except four patients and followed during 5 ± 4 years. Electrocardiogram (ECG), echocardiography assessing left ventricular ejection fraction, and Holter monitoring were obtained and repeated.

RESULTS

Twenty-seven patients (17%) presented sustained (>1 hour) AF (n = 15) or AFL (n = 12); two of them presented syncope-related 1/1 AFL. In one of them, 16 years of age, cardiac defibrillator was implanted for a diagnosis of ventricular tachycardia, but the true diagnosis was established after inappropriate shocks. AFL ablation was performed in five patients, but four developed AF. The other seven patients with AFL developed AF. During the follow-up, 22 patients died (14%) from cardiac and respiratory failure; eight patients with AF/AFL died (30%) while only 14 without AF/AFL died (10%; P < 0.01). Univariate analysis indicated that age >40 years (death: 48 ± 14 vs 40 ± 8 in alive patients), abnormal ECG, and occurrence of AF/AFL were significant factors of death. At multivariate analysis, AF at ECG (odds ratio: 3.12) and age >40 (odds ratio: 3.14) were the sole independent variables predicting death.

CONCLUSIONS

AF and AFL were frequent in MD and increased mortality. AFL could present as 1/1 AFL with a poor tolerance and a risk of misdiagnosis despite frequent conduction disturbances. This arrhythmia could explain wide QRS tachycardia occurring in MD and interpreted as VT.

[A genetic systemic disease: clinical description of type 1 myotonic dystrophy in adults]

Type 1 myotonic dystrophy is an autosomal dominant inherited disorder related to the expansion of a trinucleotide (CTG) repeat in the exon 15 in the 3'-untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. Mutant transcripts containing an expanded CUG repeat are retained in nuclear foci and cause numerous dysfunctions by interfering with biogenesis of other mRNAs. Prominent clinical features are progressive muscular weakness and myotonia, which affect skeletal muscles but also white muscles leading to digestive, urinary and obstetrical disorders. Functional prognosis correlates with motor handicap and vital prognosis is linked to cardiac rhythm disturbances and conduction defects due to progressive subendocardial fibrosis, and to complex respiratory dysfunctions, which associate restrictive lung disease, involvement of the central inspiratory pathway, and sleep apnea. Other clinical features are lens opacity, glucose intolerance, metabolic syndrome, several endocrine disorders (gonadal deficiency, hyperparathydoidism), or immunoglobulin deficiency due to immunoglobulin G hypercatabolism. Life expectancy is reduced in myotonic dystrophy, and death is mainly caused by respiratory complications, but also by cardiac arrhythmias. Moreover, an abnormal incidence of tumors has been reported. Therefore, myotonic dystrophy does not only concern neurologists but a multidisciplinary approach is necessary, including at least pneumologist, cardiologist, and physiotherapist. General internists should also be implicated, not only in the initial diagnosis step, but also in the diagnosis of complications and their treatments.