Right ventricular MR abnormalities in myotonic dystrophy and relationship with intracardiac electrophysiologic test findings: initial results

Comprehensive Cardiovascular Management of Myotonic Dystrophy Type 1 Patients: A Report from the Italian Neuro-Cardiology Network

Myotonic dystrophy is a hereditary disorder with systemic involvement. The Italian Neuro-Cardiology Network-"Rete delle Neurocardiologie" (INCN-RNC) is a unique collaborative experience involving neurology units combined with cardio-arrhythmology units. The INCN facilitates the creation of integrated neuro-cardiac teams in Neuromuscular Disease Centers for the management of cardiovascular involvement in the treatment of myotonic dystrophy type 1 (MD1).

Cardiac magnetic resonance in patients with muscular dystrophies

Muscular dystrophies are inherited disorders sharing similar clinical features and dystrophic changes on muscle biopsy. Duchenne muscular dystrophy is the most common inherited muscle disease of childhood, and Becker muscular dystrophy is a milder allelic variant with a slightly lower prevalence. Myotonic dystrophy is the most frequent form in adults. Cardiac magnetic resonance is the gold standard technique for the quantification of cardiac chamber volumes and function, and also enables a characterisation of myocardial tissue. Most cardiac magnetic resonance studies in the setting of muscular dystrophy were carried out at single centres, evaluated small numbers of patients and used widely heterogeneous protocols. Even more importantly, those studies analysed more or less extensively the patterns of cardiac involvement, but usually did not try to establish the added value of cardiac magnetic resonance to standard echocardiography, the evolution of cardiac disease over time and the prognostic significance of cardiac magnetic resonance findings. As a result, the large and heterogeneous amount of information on cardiac involvement in muscular dystrophies cannot easily be translated into recommendations on the optimal use of cardiac magnetic resonance. In this review, whose targets are cardiologists and neurologists who manage patients with muscular dystrophy, we try to summarise cardiac magnetic resonance findings in patients with muscular dystrophy, and the results of studies evaluating the role of cardiac magnetic resonance as a tool for diagnosis, risk stratification and follow-up. Finally, we provide some practical recommendations about the need and timing of cardiac magnetic resonance examination for the management of patients with muscular dystrophy.

Proarrhythmic Manifestations of Neuromuscular Dystrophinopathies

Muscular dystrophy has been an elusive term ever since it was first described in the 19th century. Introduced in 1891 by Wilhelm Heinrich Erb, muscular dystrophy has been classified as part of a larger group of genetically determined, progressive degenerative neuromuscular disorders termed "dystrophinopathies." Cardiac arrhythmias may occur during the neurologic course of the disease. Although descriptions of the dystrophinopathies have been reported in the literature, few articles address the use of antiarrhythmic pharmacotherapy in patients with muscular dystrophy. We discuss the pathophysiology of the most common dystrophinopathies, their proarrhythmic sequelae, and the therapeutic use of antiarrhythmic agents in the clinical setting.

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.

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.

SCN4A variants and Brugada syndrome: phenotypic and genotypic overlap between cardiac and skeletal muscle sodium channelopathies

SCN5A mutations involving the α-subunit of the cardiac voltage-gated muscle sodium channel (NaV1.5) result in different cardiac channelopathies with an autosomal-dominant inheritance such as Brugada syndrome. On the other hand, mutations in SCN4A encoding the α-subunit of the skeletal voltage-gated sodium channel (NaV1.4) cause non-dystrophic myotonia and/or periodic paralysis. In this study, we investigated whether cardiac arrhythmias or channelopathies such as Brugada syndrome can be part of the clinical phenotype associated with SCN4A variants and whether patients with Brugada syndrome present with non-dystrophic myotonia or periodic paralysis and related gene mutations. We therefore screened seven families with different SCN4A variants and non-dystrophic myotonia phenotypes for Brugada syndrome and performed a neurological, neurophysiological and genetic work-up in 107 Brugada families. In the families with an SCN4A-associated non-dystrophic myotonia, three patients had a clinical diagnosis of Brugada syndrome, whereas we found a remarkably high prevalence of myotonic features involving different genes in the families with Brugada syndrome. One Brugada family carried an SCN4A variant that is predicted to probably affect function, one family suffered from a not genetically confirmed non-dystrophic myotonia, one family was diagnosed with myotonic dystrophy (DMPK gene) and one family had a Thomsen disease myotonia congenita (CLCN1 variant that affects function). Our findings and data suggest a possible involvement of SCN4A variants in the pathophysiological mechanism underlying the development of a spontaneous or drug-induced type 1 electrocardiographic pattern and the occurrence of malignant arrhythmias in some patients with Brugada syndrome.

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.

Unmasked Brugada pattern by ajmaline challenge in patients with myotonic dystrophy type 1

BACKGROUND

Myotonic dystrophy type 1 (DM1) generates missplicing of the SCN5A gene, encoding the cardiac sodium channel (Nav 1.5). Brugada syndrome, which partly results from Nav 1.5 dysfunction and causes increased VF occurrence, can be unmasked by ajmaline. We aimed to investigate the response to ajmaline challenge in DM1 patients and its potential impact on their sudden cardiac death risk stratification.

METHODS

Among 36 adult DM1 patients referred to our institution, electrophysiological study and ajmaline challenge were performed in 12 patients fulfilling the following criteria: (1) PR interval >200 ms or QRS duration >100 ms; (2) absence of complete left bundle branch block; (3) absence of permanent ventricular pacing; (4) absence of implantable cardioverter-defibrillator (ICD); (5) preserved left-ventricular ejection fraction >50%; and (6) absence of severe muscular impairment. Of note, DM1 patients with ajmaline-induced Brugada pattern (BrP) were screened for SCN5A.

RESULTS

In all the 12 patients studied, the HV interval was <70 ms. A BrP was unmasked in three patients but none carried an SCN5A mutation. Ajmaline-induced sustained ventricular tachycardia occurred in one patient with BrP, who finally received an ICD. The other patients did not present any cardiac event during the entire follow-up (15 ± 4 months).

CONCLUSION

Our study is the first to describe a high prevalence of ajmaline-induced BrP in DM1 patients. The indications, the safety, and the implications of ajmaline challenge in this particular setting need to be determined by larger prospective studies.

Myotonic dystrophy type 1 mimics and exacerbates Brugada phenotype induced by Nav1.5 sodium channel loss-of-function mutation

BACKGROUND

Myotonic dystrophy type 1 (DM1), a muscular dystrophy due to CTG expansion in the DMPK gene, can cause cardiac conduction disorders and sudden death. These cardiac manifestations are similar to those observed in loss-of-function SCN5A mutations, which are also responsible for Brugada syndrome (BrS).

OBJECTIVE

The purpose of this study was to investigate DM1 effects on clinical expression of a loss-of-function SCN5A mutation causing BrS.

METHODS

We performed complete clinical evaluation, including ajmaline test, in 1 family combining DM1 and BrS. We screened the known BrS susceptibility genes. We characterized an SCN5A mutation using whole-cell patch-clamp experiments associated with cell surface biotinylation.

RESULTS

The proband, a 15-year-old female, was a survivor of out-of-hospital cardiac arrest with ventricular fibrillation. She combined a DMPK CTG expansion from the father's side and an SCN5A mutation (S910L) from the mother's side. S910L is a trafficking defective mutant inducing a dominant negative effect when transfected with wild-type Nav1.5. This loss-of-function SCN5A mutation caused a Brugada phenotype during the mother's ajmaline test. Surprisingly, in the father, a DM1 patient without SCN5A mutation, ajmaline also unmasked a Brugada phenotype. Furthermore, association of both genetic abnormalities in the proband exacerbated the response to ajmaline with a massive conduction defect.

CONCLUSION

Our study is the first to describe the deleterious effect of DM1 on clinical expression of a loss-of-function SCN5A mutation and to show a provoked BrS phenotype in a DM1 patient. The modification of the ECG pattern by ajmaline supports the hypothesis of a link between DM1 and Nav1.5 loss of -function.

Cardiac management in neuromuscular diseases

This article addresses the pathophysiology, diagnostic approaches, and therapeutic options in the more common forms of muscular dystrophy, especially those seen in pediatric and young adult populations. The major emphasis is on the dystrophinopathies because their treatment options are templates for those used in various other forms of dystrophy. Most patients with cardiomyopathy are treated with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, with other agents added as the disease progresses. Destination therapies and transplantation options are mentioned where appropriate. Some dystrophies can have significant conduction abnormalities requiring pacemaker treatment. Others with ventricular tachydysrhythmias may necessitate internal cardiac defibrillator placement.

Cardiac imaging techniques for physicians: late enhancement

Late enhancement imaging is used to diagnose and characterize a wide range of ischemic and nonischemic cardiomyopathies, and its use has become ubiquitous in the cardiac MR exam. As the use of late enhancement imaging has matured and the span of applications has widened, the demands on image quality have grown. The characterization of subendocardial MI now includes the accurate quantification of scar size, shape, and characterization of borders which have been shown to have prognostic significance. More diverse patterns of late enhancement including patchy, mid-wall, subepicardial, or diffuse enhancement are of interest in diagnosing nonischemic cardiomyopathies. As clinicians are examining late enhancement images for more subtle indication of fibrosis, the demand for lower artifacts has increased. A range of new techniques have emerged to improve the speed and quality of late enhancement imaging including: methods for acquisition during free breathing, and fat water separated imaging for characterizing fibrofatty infiltration and reduction of artifacts related to the presence of fat. Methods for quantification of T1 and extracellular volume fraction are emerging to tackle the issue of discriminating globally diffuse fibrosis from normal healthy tissue which is challenging using conventional late enhancement methods. The aim of this review will be to describe the current state of the art and to provide a guide to various clinical protocols that are commonly used.

Structural and functional cardiac changes in myotonic dystrophy type 1: a cardiovascular magnetic resonance study

BACKGROUND

Myotonic dystrophy type 1 (MD1) is a neuromuscular disorder with potential involvement of the heart and increased risk of sudden death. Considering the importance of cardiomyopathy as a predictor of prognosis, we aimed to systematically evaluate and describe structural and functional cardiac alterations in patients with MD1.

METHODS

Eighty MD1 patients underwent physical examination, electrocardiography (ECG), echocardiography and cardiovascular magnetic resonance (CMR). Blood samples were taken for determination of NT-proBNP plasma levels and CTG repeat length.

RESULTS

Functional and structural abnormalities were detected in 35 patients (44%). Left ventricular systolic dysfunction was found in 20 cases, left ventricular dilatation in 7 patients, and left ventricular hypertrophy in 6 patients. Myocardial fibrosis was seen in 10 patients (12.5%). In general, patients had low left ventricular mass indexes. Right ventricular involvement was uncommon and only seen together with left ventricular abnormalities. Functional or structural cardiac involvement was associated with age (p = 0.04), male gender (p < 0.001) and abnormal ECG (p < 0.001). Disease duration, CTG repeat length, severity of neuromuscular symptoms and NT-proBNP level did not predict the presence of myocardial abnormalities.

CONCLUSIONS

CMR can be useful to detect early structural and functional myocardial abnormalities in patients with MD1. Myocardial involvement is strongly associated with conduction abnormalities, but a normal ECG does not exclude myocardial alterations. These findings lend support to the hypothesis that MD1 patients have a complex cardiac phenotype, including both myocardial and conduction system alteration.

Myotonic dystrophy types 1 and 2

Myotonic dystrophies (dystrophia myotonica, or DM) are inherited disorders characterized by myotonia and progressive muscle degeneration, which are variably associated with a multisystemic phenotype. To date, two types of myotonic dystrophy, type 1 (DM1) and type 2 (DM2), are known to exist; both are autosomal dominant disorders caused by expansion of an untranslated short tandem repeat DNA sequence (CTG)(n) and (CCTG)(n), respectively. These expanded repeats in DM1 and DM2 show different patterns of repeat-size instability. Phenotypes of DM1 and DM2 are similar but there are some important differences, most conspicuously in the severity of the disease (including the presence or absence of the congenital form), muscles primarily affected (distal versus proximal), involved muscle fiber types (type 1 versus type 2 fibers), and some associated multisystemic phenotypes. The pathogenic mechanism of DM1 and DM2 is thought to be mediated by the mutant RNA transcripts containing expanded CUG and CCUG repeats. Strong evidence supports the hypothesis that sequestration of muscle-blind like (MBNL) proteins by these expanded repeats leads to misregulated splicing of many gene transcripts in corroboration with the raised level of CUG-binding protein 1. However, additional mechanisms, such as changes in the chromatin structure involving CTCN-binding site and gene expression dysregulations, are emerging. Although treatment of DM1 and DM2 is currently limited to supportive therapies, new therapeutic approaches based on pathogenic mechanisms may become feasible in the near future.

Increased temporal dispersion of myocardial repolarization in myotonic dystrophy type 1: beyond the cardiac conduction system

BACKGROUND AND OBJECTIVES

The most frequently mechanism underlying sudden cardiac death in myotonic dystrophy type 1 (DM1) is bradyarrhythmias due to cardiac conduction abnormalities. However the risk of ventricular tachyarrhythmias remains a concern in clinical management as well as in its determinant. We therefore assessed autonomic nervous system activity aiming to disclose differences in the QT variability index (QTVI)-a marker of temporal myocardial repolarization lability-between DM1 patients and healthy controls. We also investigated the possible differences within DM1 patients by subdividing them according either to the presence of first degree atrioventricular block (1st AVB) or to the cytosine-thymine-guanine (CTG) repeat expansion size.

METHODS

Sixty-two DM1 patients and 20 healthy subjects underwent neurological and cardiological examinations, the latter including ECG, echocardiography and 24-hour Holter monitoring. All underwent a 5-minute ECG recording to assess heart rate variability power spectral components, and the QTVI values.

RESULTS

Power spectral data, namely total power, low frequency power and high frequency power, were lower, whereas QTVI values were higher in DM1 patients than in controls (p<.0001). Higher QTVI values were found in DM1 subgroups with 1st AVB (p=.009) and more than 500 CTG repeat (p=.014) with respect to DM1 patients without 1st AVB and CTG<500. Spectral data did not significantly differ. At multivariable analysis, QTVI and age were independently associated with PR interval and CTG repeat.

CONCLUSIONS

The increased values of QTVI argue in favour of an important heart involvement extending beyond the conduction system. Whether QTVI could be useful in predicting clinical course of DM1 clearly requires larger prospective studies.

Myocardial Fat Imaging

The presence of intramyocardial fat may form a substrate for arrhythmias, and fibrofatty infiltration of the myocardium has been shown to be associated with sudden death. Therefore, noninvasive detection could have high prognostic value. Fat-water–separated imaging in the heart by MRI is a sensitive means of detecting intramyocardial fat and characterizing fibrofatty infiltration. It is also useful in characterizing fatty tumors and delineating epicardial and/or pericardial fat. Multi-echo methods for fat and water separation provide a sensitive means of detecting small concentrations of fat with positive contrast and have a number of advantages over conventional chemical-shift fat suppression. Furthermore, fat and water–separated imaging is useful in resolving artifacts that may arise due to the presence of fat. Examples of fat-water–separated imaging of the heart are presented for patients with ischemic and nonischemic cardiomyopathies, as well as general tissue classification.

Possible de novo CTG repeat expansion in the DMPK gene of a patient with cardiomyopathy

CTG triplet repeats of "normal" length in the myotonic dystrophy protein kinase (DMPK) gene have been previously believed to be stable and new pathological expansion was not believed to occur. Here we report possible de novo CTG repeat expansion in the DMPK gene in a patient with cardiomyopathy, who was not diagnosed as having myotonic dystrophy type 1 (DM1) by conventional genetic tests.

Usefulness of clinical and electrocardiographic data for predicting adverse cardiac events in patients with myotonic dystrophy

BACKGROUND

Myotonic dystrophy type 1 (DM1) has been associated with an increased risk of sudden death, either by heart block or malignant ventricular arrhythmias. Identifying patients at risk remains difficult and no consensus has been reached regarding the best approach for follow-up and prevention of sudden death.

OBJECTIVES

To identify noninvasive clinical and electrocardiographic predictors of adverse cardiac events in patients with DM1.

METHODS

Clinical and serial electrocardiographic data on 428 patients with a DNA-proven diagnosis of DM1, followed during a mean period of 11.7 years, were reviewed. Variables associated with adverse cardiac events were identified.

RESULTS

Eleven patients (2.6%) experienced sudden death and 13 (3.0%) required implantation of a pacemaker. On univariate analysis, adverse events were associated with advancing age, prolongation of the PR, QRS and corrected QT (QTc) intervals, as well as the degree of neuromuscular impairment. No such relationship was found with the extent of genetic anomaly (number of cytosine-thymine-guanine repeats). However, multivariate analysis using Cox proportional hazards models showed that only baseline PR and QTc intervals were significantly linked to the end points of sudden death or pacemaker implantation; the age-adjusted RR was 3.7 (95% CI 1.5 to 8.6) if baseline PR was 200 ms or longer (P=0.003), and 3.0 (95% CI 1.0 to 8.8) if the baseline QTc was 450 ms or longer (P=0.047).

CONCLUSIONS

In a large unselected cohort of 428 patients with DM1, the cumulative incidence of sudden death was relatively low, and the delayed conduction on surface electrocardiogram was found to be potentially helpful for identifying patients at risk for sudden death or pacemaker implantation.

Optimal site for atrial lead implantation in myotonic dystrophy patients: the role of Bachmann's Bundle stimulation

AIM

The aim of this study was to identify the optimal site for atrial lead implantation in myotonic dystrophy type 1 (MD1) patients.

METHODS

The atrial pacing lead was positioned in the high-lateral right atrial wall (site A), then in the right atrial appendage (site B), and finally on the interatrial septum (site C) in 22 patients. Pacing and sensing thresholds were obtained for all sites. The lead was repositioned and fixed at the optimal site, defined as the location with the lowest pacing and the highest sensing thresholds.

RESULTS

Mean pacing thresholds were 1.46 +/- 0.32 V at site A, 1.45 +/- 0.33 V at site B, and 0.84 +/- 0.24 V at site C. P-wave amplitude was 1.52 +/- 0.45 mV at site A, 1.52 +/- 0.49 mV at site B, and 2.60 +/- 0.48 mV at site C. Atrial lead was implanted at site C in all patients without complications.

CONCLUSIONS

Interatrial septum in the region of Bachmann's Bundle seems to be the optimal site for atrial lead implantation in MD1 patients.

Cardiac assessment of limb-girdle muscular dystrophy 2I patients: an echography, Holter ECG and magnetic resonance imaging study

Mutations in the FKRP gene may be associated with cardiac involvement. The aim of our study was to assess myocardial involvement in patients with LGMD2I, using physical examination, echocardiography, resting and 24-h ambulatory electrocardiogram and cardiac magnetic resonance imaging, with particular attention to the detection of myocardial morphologic abnormalities. Patients were compared to matched controls. Twenty-three patients were enrolled (men 10--women 13; 32.3+/-9.5 years). Twenty-two had the C826A gene mutation (homozygous 12, heterozygous 10). Nine patients had severe muscle alterations, 10 had milder muscle involvement and 4 had isolated exertional myoglobinuria. When compared to controls, LGMD2I patients had reduced left ventricular ejection fraction (50.8+/-13.9 versus 66.6+/-3.8%, p<0.0001). Sixty percent of patients had reduced left ventricular ejection fraction, including 8% with severe reduced left ventricular ejection fraction <30%. None had significant arrhythmia. Gene mutation and the severity of the muscle disease were not predictive of cardiac involvement. Cardiac magnetic resonance imaging displayed a high prevalence of myocardial functional abnormalities, fatty replacement and fibrosis, among the 13 patients investigated. Reduced contractility and cardiac magnetic resonance imaging morphological abnormalities are highly prevalent in LGMD2I patients suggesting that all patients should be referred for cardiac evaluation.

Early detection of biventricular involvement in myotonic dystrophy by tissue Doppler

BACKGROUND

Myotonic dystrophy is associated with arrhythmias and risk of sudden death but also with symptoms of heart failure. Our study aimed to identify early biventricular dysfunction in asymptomatic patients with myotonic dystrophy by tissue Doppler.

METHODS

Thirty-six patients with myotonic dystrophy (M/F=20/16, mean age=36.4 years), asymptomatic for heart failure, and 36 age- and sex-matched healthy controls underwent Doppler echocardiography and pulsed tissue Doppler of lateral mitral annulus and of tricuspid annulus.

RESULTS

The two groups had similar body mass index, blood pressure, heart rate, cardiac mass and endocardial shortening. Standard Doppler showed significantly lower transmitral early (E) diastolic peak velocity, longer transmitral deceleration and isovolumic relaxation times and higher tricuspid inflow atrial peak velocity in myotonic dystrophy than in controls. Tissue Doppler of mitral annulus showed lower myocardial systolic velocity (p<0.02), lower early diastolic velocity (E(m)) (p<0.05) and atrial velocity (A(m)) (p<0.005), but no difference of E(m)/A(m) ratio. At tricuspid annulus, E(m) and E(m)/A(m) ratio were lower (p<0.02 and p<0.005, respectively). The ratio between tricuspid inflow E velocity and E(m), index of the degree of right ventricular filling pressure, was higher (p<0.001) than in controls. Tissue Doppler derived left ventricular and right ventricular measurements were all associated with the disease condition, independent of age and heart rate.

CONCLUSIONS

Tissue Doppler identifies subclinical biventricular involvement in myotonic dystrophy. Early left ventricular myocardial systolic and diastolic changes are evident. Right ventricular dysfunction, involving myocardial relaxation and right ventricular filling pressure, might be the arrhythmogenic substratum of these patients.

Widespread Electroanatomic Alterations of Right Cardiac Chambers in Patients with Myotonic Dystrophy Type 1

INTRODUCTION

Conduction disturbances and arrhythmias characterize the cardiac feature of myotonic dystrophy type 1 (MD1); a myocardial involvement has been suggested as part of the cardiac disease. The aim of our study was to investigate the underlying myocardial alterations using electroanatomic mapping (CARTO) and their possible correlation with genetic and neurological findings.

METHODS AND RESULTS

Right atrial and ventricular CARTO maps were obtained in 13 MD1 patients. Thirteen age-matched patients with paroxysmal supraventricular tachycardia and normal heart served as controls. Unipolar voltage (UNI-v), bipolar voltage (BI-v) amplitudes, bipolar potential duration (Bi-dur), and atrial propagation time (A-pt) were measured. UNI-v and BI-v in interatrial septum, anterolateral atrial wall, and right ventricle outflow tract were lower in MD1 patients than controls (P < 0.001). Bi-dur and A-pt were longer in MD1 patients than controls (P < 0.001, P = 0.046, respectively). A significant relationship was documented between CTG triplets and the percentage of Bi-v <0.5 mV in the atrial anteroseptal region (r = 0.6, P = 0.02).

CONCLUSIONS

Altered electroanatomic patterns are present in the right cardiac chambers in MD1 patients. Widespread myocardial alterations, not necessarily limited to the conduction system, may support the presence of a cardiac myopathy as part of the disease.

Genetics of right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disease that may result in arrhythmia, heart failure, and sudden death. The hallmark pathological findings are progressive myocyte loss and fibrofatty replacement, with a predilection for the right ventricle. However, variants of ARVC that preferentially affect the left ventricle are increasingly recognized. ARVC is distinguished from dilated cardiomyopathy by a propensity toward ventricular arrhythmia and sudden death in the absence of significant ventricular dysfunction. In the majority of families, ARVC shows autosomal dominant inheritance with incomplete penetrance. Recessive forms are also described, often in association with cutaneous disorders. Causative mutations have so far been identified in plakoglobin, desmoplakin, and plakophilin, all of which encode key components of the desmosome. Desmosomes are protein complexes that anchor intermediate filaments to the cytoplasmic membrane in adjoining cells, thereby forming a three-dimensional scaffolding that provides tissues with mechanical strength. Unraveling of the genetic etiology of ARVC has elicited a new model for pathogenesis. Impaired functioning of cell adhesion junctions during exposure to shear stress may lead to myocyte detachment and death, accompanied by inflammation and fibrofatty repair. At least three mechanisms contribute to the arrhythmic substrate: bouts of myocarditis, fibrous and adipose infiltrates that facilitate macroreentry, and gap junction remodeling secondary to altered mechanical coupling. The latter may underlie arrhythmogenicity in early disease. Although ARVC can be considered a disease of the desmosome, a variety of other genetic defects give rise to phenocopies, which may ultimately enhance our understanding of the broad phenotypic spectrum.

Cardiac complications of childhood myopathies

The management of individuals with a neuromuscular disorder is usually focused on the skeletal muscle weakness and resulting complications, such as respiratory failure. Long-term prognosis of a number of neuromuscular conditions is, however, also determined by the type and severity of cardiac involvement. Early recognition and treatment of the cardiovascular complications are part of the task of the multidisciplinary team involved in the care of these patients. Although for several of the common conditions, there is general consensus on the cardiac investigations and treatments, in the rarer disorders, evidence-based recommendations are not available, and suggestions from experts provide an acceptable solution. This review summarizes the recent advances in our understanding of the pathogenesis and phenotypic diversity of cardiac complications associated with pediatric myopathies and provides a rational framework for planning the monitoring and therapeutic intervention in individual conditions.

Screening with MRI: a new "all inclusive" protocol

In the past decades, only mammography has been considered to be a valuable radiological screening test in the European community, as the amount of ionizing radiation associated with other radiological imaging modalities did not justify their use for screening. MRI overcomes many limitations inherent to other imaging methods: lack of ionizing radiation, high spatial and temporal resolution, and unsurpassed soft-tissue contrast. Up to now, only few diseases have been screened for with MR: primarily breast cancer and colonic cancer. A new 60-minute comprehensive MR screening protocol is now capable of assessing the central nervous, the peripheral and the cardiovascular system, as well as the colon, allowing for screening of several diseases simultaneously.