Myocardial tissue velocity reduction is correlated with clinical neurologic severity in myotonic dystrophy

Cardiac Pathology in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1), the most common muscular dystrophy affecting adults and children, is a multi-systemic disorder affecting skeletal, cardiac, and smooth muscles as well as neurologic, endocrine and other systems. This review is on the cardiac pathology associated with DM1. The heart is one of the primary organs affected in DM1. Cardiac conduction defects are seen in up to 75% of adult DM1 cases and sudden death due to cardiac arrhythmias is one of the most common causes of death in DM1. Unfortunately, the pathogenesis of cardiac manifestations in DM1 is ill defined. In this review, we provide an overview of the history of cardiac studies in DM1, clinical manifestations, and pathology of the heart in DM1. This is followed by a discussion of emerging data about the utility of cardiac magnetic resonance imaging (CMR) as a biomarker for cardiac disease in DM1, and ends with a discussion on models of cardiac RNA toxicity in DM1 and recent clinical guidelines for cardiologic management of individuals with DM1.

Outcome measures frequently used to assess muscle strength in patients with myotonic dystrophy type 1: a systematic review

Measurement of muscle strength is fundamental for the management of patients with myotonic dystrophy type 1 (DM1). Nevertheless, guidance on this topic is somewhat limited due to heterogeneous outcome measures used. This systematic literature review aimed to summarize the most frequent outcome measures to assess muscle strength in patients with DM1. We searched on Pubmed, Web of Science and Embase databases. Observational studies using measures of muscle strength assessment in adult patients with DM1 were included. From a total of 80 included studies, 24 measured cardiac, 45 skeletal and 23 respiratory muscle strength. The most common method and outcome measures used to assess cardiac muscle strength were echocardiography and ejection fraction, for skeletal muscle strength were quantitative muscle test, manual muscle test and maximum isometric torque and medical research council and for respiratory muscle strength were manometry and maximal inspiratory and expiratory pressure. We successfully gathered the more consensual methods and measures to evaluate muscle strength in future clinical studies, particularly to test muscle strength response to treatments in patients with DM1. Future consensus on a set of measures to evaluate muscle strength (core outcome set), is important for these patients.

Risk Stratification of Genetic, Dilated Cardiomyopathies Associated With Neuromuscular Disorders: Role of Cardiac Imaging

The etiology of dilated cardiomyopathy (DCM) can be grouped as either genetic or nongenetic. More than 50 pathogenic genes have been described, with sarcomeric and lamin A/C mutations being the most common. Mutation carriers for genetic DCM are often asymptomatic until cardiac disease manifests with heart failure, arrhythmias, or sudden cardiac death. Preventive strategies are promising but can only be applied and tested adequately if genetic DCM can be diagnosed at an early stage. Early diagnosis of mutation carriers that may develop overt DCM requires advanced imaging techniques that can detect subtle structural and functional abnormalities. Advanced echocardiographic techniques such as tissue Doppler imaging and speckle tracking strain analysis permit early detection of functional abnormalities, whereas cardiovascular magnetic resonance techniques provide information on tissue characterization and myocardial energetics that may be altered at an early stage. Furthermore, nuclear imaging techniques provide information on cellular function (metabolism, perfusion). Once the diagnosis of overt DCM has been established, various imaging parameters such as echocardiography-based myocardial mechanics and cardiovascular magnetic resonance-based tissue characterization have shown incremental benefit to left ventricular ejection fraction in risk stratification. Further research is required to understand how imaging techniques may help to choose management strategies that could delay progression when instituted early in the course of the disease. The present article reviews the role of imaging in the risk stratification of genetic DCM in general, with specific emphasis on DCM associated with neuromuscular disorders.

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.

Diastolic Function in Steinert's Disease

Myotonic dystrophy type 1 (MD) is the most common autosomal dominant muscular dystrophy in adults. Cardiac involvement is mainly characterized by conduction abnormalities and arrhythmias. We sought to assess diastolic function in MD patients. Echocardiography-Doppler was performed in Steinert's patients and in a control group completed by tissue Doppler imaging (TDI). Twenty-six patients with Steinert's disease were included in the study and were compared to a control group. Mean age was similar in the 2 groups (45.1 years ±10.9 in Steinert's patients vs 42.1 years ±11 in control group p 0.4). 6 /26 patients with Steinert's disease disclosed a left ventricular (LV) ejection fraction <50%. Mean left atrial (LA) diameter was statistically different between Steinert's patients and patients in group control (27.8 mm ±8.5 vs 19.7 mm ±4; P=0.0018). Mean peak E/A mitral ratio was 1.29±0.45 in Steinert's patients vs 1.36±0.4 in control group (P=0.6). We found an increase of the mitral E deceleration time in Steinert's patients in comparison with patients in control group (219 ms ±53 vs 176 ms ±29; P=0.013). Mean peak lateral early diastolic velocity Ea was similar in the 2 groups (12.3 cm/s ±3 vs 13.1 cm/s ±3.8; P=0.50). Mean peak septal early diastolic velocity was similar in the 2 groups (11.2 cm/s ±2 vs 10.4±2; P=0.51). We found an increase of the LA diameter and an increase of the mitral deceleration time in Steinert's patients that suggest diastolic abnormalities.

[Heart and Steinert's disease]

Myotonic dystrophy type 1 (Steinert disease) is an autosomal dominant disease characterized by myotonia and multiorgan damage. This latter is the most frequent of the adult-onset muscular dystrophies. Heart involvement is often associated, including cardiomyopathies, atrioventricular block, atrial and ventricular arrhythmias.

Evaluation of biventricular functions with tissue Doppler imaging in patients with myotonic dystrophy

BACKGROUND

Myotonic dystrophy (MD) is characterized by myotonia with dystrophic involvement of the muscles. Cardiac involvement is usually not evident in the early stages of MD.

HYPOTHESIS

We investigated biventricular functions by tissue Doppler imaging (TDI) in MD patients with no overt cardiac involvement to explore the value of TDI in the early detection of myocardial dysfunction.

METHODS

A total of 21 MD patients (15 male, age: 32.2 +/- 12.3 yrs) and 21 healthy controls (13 male, age: 32.2 +/- 7.8 yrs) were included. In addition to conventional echocardiography, pulsed Doppler and TDI were performed including measurement of myocardial performance index (MPI); peak systolic (Sm) and early (Em) and atrial (Am) diastolic myocardial velocities at the basal mitral and tricuspid annulus.

RESULTS

All patients and controls had normal ejection fraction. Transmitral E peak velocity was significantly lower while both deceleration time of E velocity and isovolumic relaxation time were significantly longer in MD patients (P = 0.007, P = 0.001, and P < 0.001, respectively). Sm, Em and Am peak velocities were significantly lower in MD patients in all segments except for Em of the mitral anterior annulus and Am of the tricuspid lateral annulus. Both left and right ventricular MPI were significantly higher in MD patients (P < 0.001 and P = 0.013, respectively).

CONCLUSION

There are changes in myocardial systolic and diastolic functions in MD patients although they have no overt heart failure. Myocardial tissue velocities and MPI are useful in identifying subclinical biventricular involvement in these patients.

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.

Use of tissue Doppler imaging to identify and manage systemic diseases

In systemic diseases such as amyloidosis, sarcoidosis, Friedreich's ataxia, Fabry's disease and muscular dystrophy the clinician has to judge the presence and the amount of cardiac involvement. In most of these patients conventional echocardiographic parameters are not sensitive enough to detect sub-clinical dysfunction. Tissue Doppler imaging and in addition strain rate imaging has proven to be very sensitive for the assessment of myocardial dysfunction. This review explores the impact of these new techniques to identify and to manage cardiac aspects of the different systemic diseases.

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.

Effects of testosterone and nandrolone on cardiac function: a randomized, placebo-controlled study

BACKGROUND

Androgens have striking effects on skeletal muscle, but the effects on human cardiac muscle function are not well defined, neither has the role of metabolic activation (aromatization, 5alpha reduction) of testosterone on cardiac muscle been directly studied.

OBJECTIVE

To assess the effects of testosterone and nandrolone, a non-amplifiable and non-aromatizable pure androgen, on cardiac muscle function in healthy young men.

DESIGN

Double-blind, randomized, placebo-controlled, three-arm parallel group clinical trial.

SETTING

Ambulatory care research centre.

PARTICIPANTS

Healthy young men randomized into three groups of 10 men.

INTERVENTION

Weekly intramuscular injections of testosterone (200 mg mixed esters), nandrolone (200 mg nandrolone decanoate) or matching (2 ml arachis oil vehicle) placebo for 4 weeks.

MAIN OUTCOME MEASURES

Comprehensive measures of cardiac muscle function involving transthoracic cardiac echocardiography measuring myocardial tissue velocity, peak systolic strain and strain rates, and bioimpedance measurement of cardiac output and systematic vascular resistance.

RESULTS

Left ventricular (LV) function (LV ejection fraction, LV modified TEI index), right ventricular (RV) function (ejection area, tricuspid annular systolic planar motion, RV modified TEI index) as well as cardiac afterload (mean arterial pressure, systemic vascular resistance) and overall cardiac contractility (stroke volume, cardiac output) were within age- and gender-specific reference ranges and were not significantly (P < 0.05) altered by either androgen or placebo over 4 weeks of treatment. Minor changes remaining within normal range were observed solely within the testosterone group for: increased LV end-systolic diameter (30 +/- 7 vs. 33 +/- 5 mm, P = 0.04) and RV end-systolic area (12.8 +/- 1.3 vs. 14.6 +/- 3.3 cm(2), P = 0.04), reduced LV diastolic septal velocity (Em, 9.5 +/- 2.6 vs. 8.7 +/- 2.0 cm/s, P = 0.006), increased LV filling pressure (E/Em ratio, 7.1 +/- 1.6 vs. 8.3 +/- 1.8, P = 0.02) and shortened PR interval on the electrocardiogram (167 +/- 13 vs. 154 +/- 12, P = 0.03).

CONCLUSION

Four weeks of treatment with testosterone or nandrolone had no beneficial or adverse effects compared with placebo on cardiac function in healthy young men.

Left ventricular synchronization by biventricular pacing in Becker muscular dystrophy as assessed by tissue Doppler imaging

Biventricular (BiV) pacing is a promising therapy for severe heart failure. The effect of BiV pacing is cardiac resynchronization of both ventricles. Asynchrony of the ventricular contraction and restoration of cardiac synchronization can be assessed by tissue Doppler imaging. Here we describe a patient with Becker muscular dystrophy with heart failure caused by dilated cardiomyopathy in whom a BiV pacemaker was implanted.

Contribution of Doppler tissue imaging and myocardial performance index to assessment of left ventricular function in patients with Duchenne's muscular dystrophy

Doppler tissue velocities (DTV) are abnormal in a variety of cardiac conditions when standard measures of ventricular function are normal. Detection of left ventricular dysfunction in Duchenne's muscular dystrophy (DMD) has relied on 2-dimensional imaging yet often these images are suboptimal. This study was undertaken to determine if DTV and the myocardial performance index (MPI) could provide additional diagnostic information in DMD. We determined in 31 patients and 13 age-matched control subjects the prevalence of both abnormal DTV of the mitral annulus and abnormal MPI. Mean values for early diastolic DTV were significantly lower for patients compared with control subjects (P < .001) and were abnormally low in 86% of patients. The MPI was abnormal in 79% of patients. All but one patient with DMD had either abnormal DTV or abnormal MPI yet 19% had normal fractional shortening. DTV and MPI are important additions to the echocardiographic evaluation of patients with DMD.

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.