Echocardiographic evaluation of cardiac abnormalities in Duchenne's dystrophy and myotonic muscular 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.

The Relationship between Preoperative Echocardiographic Evaluation and Spinal Deformity in Patients with Neuromuscular Scoliosis

Introduction

Echocardiography is an important component of perioperative cardiac risk stratification in patients with neuromuscular scoliosis (NMS). However, there are little data regarding the relationship between preoperative echocardiographic findings and spinal deformity. We retrospectively reviewed preoperative echocardiographic data to investigate the relationship between echocardiographic evaluation and spinal deformity in NMS.

Methods

We reviewed 73 NMS patients (mean age: 13.3 years, male 66%) who underwent spinal correction surgery between 2008 and 2016. Echocardiographic data including ejection fraction (EF), valvar disease, and inferior vena cava diameter were collected from the preoperative exam. Demographic and radiographic data were also collected.

Results

Preoperative diagnoses included Duchenne muscular dystrophy, Fukuyama congenital muscular dystrophy, other dystrophy, spinal muscular atrophy, and congenital myopathies. Mean Body Mass Index (BMI) was 15.6 kg/m². Mean major Cobb angle before surgery was 86.6 ± 28.2°. Because of technical difficulty, complete echocardiographic data could only be collected and evaluated in 49.3% of patients. Neither right nor left sided cardiac evaluation could be completed in 20.5%. Patients in whom complete echocardiographic data could not be collected had significantly more extensive thoracic scoliosis with a more rigid curve and hypokyphosis, and were of lower weight and BMI than patients in whom complete data could be collected. Ten cases (13.7%) were diagnosed as having minor heart-related complications immediately after surgery, and they had higher right atrial pressures preoperatively.

Conclusions

Echocardiography can be technically difficult in NMS patients with extensive spinal deformities. We found that perioperative cardiac function could only be evaluated by echocardiogram in about half of NMS patients undergoing spinal correction surgery. The absence of an adequate preoperative cardiac evaluation could render these patients more susceptible to perioperative heart-related complications. Echocardiography may not be sufficient to evaluate cardiac conditions in children with extensive NMS.

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.

Left ventricular diastolic function in congenital myotonic dystrophy

OBJECTIVE

Examination of left ventricular function and conduction abnormalities in myotonic dystrophy.

DESIGN

Twelve patients (median age, 13.7 years) with myotonic dystrophy had detailed electrocardiography and echocardiography performed. Echocardiographic parameters were compared with body surface area (BSA) matched median normal values.

RESULTS

Fractional shortening was slightly reduced (by 28-29%) in three patients and three patients had mild mitral valve prolapse. Diastolic function was abnormal; isovolumic relaxation time (IVRT) and duration of early filling were prolonged compared with control values (median IVRT, 74 v 61 ms). Peak E velocity was increased (median, 0.82 v 0.78 m/s) but atrial phase filling was normal. Heart rate was reduced (median, 68 v 81 beats/min). Conduction abnormalities were common but showed no clear relations with diastolic abnormalities.

CONCLUSIONS

Young patients with myotonic dystrophy have myocardial diastolic dysfunction as well as abnormal electrophysiology. The prognostic implications of such abnormalities require further study.

Sustained ventricular tachycardias associated with myotonic dystrophy

Patients with myotonic dystrophy are reported to have a higher frequency of sudden death than the general population. Although causes of sudden death in myotonic dystrophy are suggested to be due to conduction of defects progressing, the HV interval cannot predict whether conduction system disease would develop or progress. We report two cases of myotonic dystrophy complicated with sustained monomorphic ventricular tachycardias (VT), which can cause sudden death. In Case No. 1, although the patient was treated successfully for sustained VT with verapamil in electrophysiologic studies, another sustained VT was confirmed 2 years later. In Case No. 2, the patient showed decreased left ventricular ejection fraction and late potentials, and induced sustained VT that was identical to clinically documented VT. Although VT is believed to be rare in patients with myotonic dystrophy, these cases suggest that VT is a possible cause of sudden death.

Two successful double-blind trials with coenzyme Q10 (vitamin Q10) on muscular dystrophies and neurogenic atrophies

Coenzyme Q10 (vitamin Q10) is biosynthesized in the human body and is functional in bioenergetics, anti-oxidation reactions, and in growth control, etc. It is indispensable to health and survival. The first double-blind trial was with twelve patients, ranging from 7-69 years of age, having diseases including the Duchenne, Becker, and the limb-girdle dystrophies, myotonic dystrophy. Charcot-Marie-Tooth disease, and the Welander disease. The control coenzyme Q10 (CoQ10) blood level was low and ranged from 0.5-0.84 microgram/ml. They were treated for three months with 100 mg daily of CoQ10 and a matching placebo. The second double-blind trial was similar with fifteen patients having the same categories of disease. Since cardiac disease is established to be associated with these muscle diseases, cardiac function was blindly monitored, and not one mistake was made in assigning CoQ10 and placebo to the patients in both trials. Definitely improved physical performance was recorded. In retrospect, a dosage of 100 mg was too low although effective and safe. Patients suffering from these muscle dystrophies and the like, should be treated with vitamin Q10 indefinitely.

Myocardial myotonia in myotonic muscular dystrophy

We sought to determine whether and to what degree myocardial myotonia might occur in myotonic muscular dystrophy. Cardiac involvement manifests itself chiefly as abnormalities of specialized tissues. Current echocardiographic techniques permit assessment of left ventricular diastolic filling properties and might detect subtle myocardial myotonia. Twenty patients (mean age 37 +/- 13 years) with myotonic muscular dystrophy were studied. Twenty normal subjects (mean age 34 +/- 12 years), served as controls. Each subject had two-dimensional targeted M-mode echocardiograms of the posterior left ventricular wall to measure the rate of early diastolic relaxation, which was defined as diastolic endocardial velocity maximum (DEVM). Global left ventricular function was quantified. Doppler recordings of mitral inflow measured peak E and A velocities, ratio of E to A (E/A), mitral deceleration time (DT) and isovolumic relaxation (IVR) time. Normal controls had DEVM = 19 +/- 3 cm/sec, IVR = 72 +/- 7 msec, E/A = 1.6 +/- 0.5, and DT = 193 +/- 18 msec. Two SDs below the mean normal DEVM was 13.3 cm/sec. Two patient groups emerged: group A (10 patients) had abnormally slow DEVM (< or = 13.2 cm/sec) and group B (10 patients) had normal DEVM (> 13.2 cm/sec) with DEVM = 11 +/- 2 cm/sec and 20 +/- 4 cm/sec, respectively. Mitral inflow parameters showed a longer DT and IVR, with lower E/A ratios for group A versus group B, with DT = 203 +/- 48 msec and 175 +/- 21 msec, IVR = 87 +/- 15 msec and 74 +/- 7 msec, E/A = 1.7 +/- 0.7 and 2.3 +/- 0.9, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between cardiac involvement and CTG trinucleotide repeat length in myotonic dystrophy

OBJECTIVES

Because sudden death due to complete atrioventricular (AV) block or ventricular arrhythmias is the most dramatic event in myotonic dystrophy, we assessed the relation of cardiac disease to cytosine-thymine-guanine (CTG) triplet mutation in adults affected with myotonic dystrophy.

BACKGROUND

The myotonic dystrophy mutation, identified as an unstable deoxyribonucleic acid (DNA) sequence (CTG) prone to increase the number of trinucleotide repeats, produces clinical manifestations of the disease in skeletal muscle, the heart and many organ systems.

METHODS

Forty-two adult patients underwent electrocardiography and echocardiography; in addition, signal-averaging electrocardiography was performed in 22, and 24-h Holter monitoring was recorded in 32. The diagnosis was established by neurologic examination, electromyography, muscle biopsy and DNA analysis. The patients were then classified into three subgroups on the basis of the number of CTG trinucleotide repeat expansions: E1 = 18 patients with 0 to 500 CTG repeats; E2 = 12 patients with up to 1,000 repeats; E3 + E4 = 10 patients with up to 1,500 repeats and 2 patients with > 1,500 repeats.

RESULTS

The incidence of normal electrocardiographic (ECG) results was found to be significantly different in the three subgroups (55%, 50%, 17% in E1, E2, E3, + E4, respectively, p = 0.04), with the highest values in the group with fewer repeat expansions. The incidence of complete left bundle branch block was also significantly different among the groups (5% in E1, 0% in E2, 42% in E3 + E4 p = 0.01) and was directly correlated with the size of the expansion. A time-domain analysis of the signal-averaged ECG obtained in 12 patients in E1, 4 in E2, 5 in E3 and 1 in E4 showed that abnormal ventricular late potentials were directly correlated with CTG expansion (33% in E1, 75% in E2, 83% in E3 + E4, p = 0.05). Moreover, the incidence of ventricular couplets or triplets showed a positive correlation with size of CTG expansion (0 in E1, 0 in E2, 29% in E3 + E4, chi square 0.02).

CONCLUSIONS

Our findings suggest that the involvement of specialized cardiac tissue, accounting for severe AV and intraventricular conduction defects, is related to CTG repeat length. In addition, the presence of abnormal late potentials directly correlates to CTG expansion. Abnormal late potentials, caused by slowed and fragmented conduction through damaged areas of myocardium, represent a substrate for malignant reentrant ventricular arrhythmias. In the future, therefore, molecular analysis of DNA should identify patients with cardiac disease at high risk for development of AV block or lethal ventricular arrhythmias.

Left ventricular myocardial function in myotonic dystrophy

Myotonic dystrophy is an autosomal dominant disease affecting many organ systems, including the heart. Abnormalities of the cardiac conduction system are a frequent and well-documented finding in this neuromuscular disease, whereas overt signs of heart failure are rarely reported. However, controversy exists about the prevalence of preclinical left ventricular (LV) dysfunction in patients with myotonic dystrophy who have no symptoms of heart failure. To address this issue, load-independent LV function indexes were compared in patients with myotonic dystrophy and in normal subjects. LV measurements were obtained with M-mode echocardiography in 43 consecutive patients with myotonic dystrophy (mean age 35 +/- 14 years) who had no clinical evidence of heart failure, and in 35 sex- and age-matched controls. A cuff sphygmomanometer was used to determine blood pressure. No difference was found between patients and control subjects in the percentage of LV ejection fraction predicted for end-systolic stress (103 +/- 7 vs 103 +/- 7%; p = 0.97) or in the end-systolic stress/volume index ratio (2.9 +/- 0.5 vs 2.7 +/- 0.4 dyne7/cm3; p = 0.09). Similarly, no significant difference in LV myocardial function was detected between the 19 patients with a mild degree of the neuromuscular disease and in the 24 with a moderate or severe degree of the disease. Finally, LV myocardial function was compared between patients with myotonic dystrophy and atrioventricular or intraventricular conduction disturbances (n = 8) and those without these disturbances (n = 35), but no significant difference in the percentage of LV ejection fraction predicted for end-systolic stress or in the end-systolic stress/volume index ratio could be detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Spinal fusion in Duchenne muscular dystrophy: a multidisciplinary approach

We studied 27 Duchenne muscular dystrophy patients having spinal fusion for scoliosis. One patient died intraoperatively of cardiac arrest; all others have done well with no instances of malignant hyperthermia, postoperative ventilatory system dependence, pneumothorax, persisting infection, neurologic damage, nonunion, or pain. The anesthetic management included primarily intravenous general anesthetics with minimal myocardial depressant effects, avoiding succinylcholine and inhalation agents. Preoperative cardiac studies aided anesthetic management intra-operatively. There was an almost universal sinus tachycardia. Holter monitoring defined 4 of 16 with ventricular premature beats, 4 of 16 with atrial premature beats, and no ventricular tachycardia or atrial flutter or fibrillation. Echocardiogram demonstrated mitral prolapse in 2 of 22, frequent abnormal systolic performance with abnormal shortening fraction less than 28% in 7 of 16, and reduced rate-corrected velocity of fiber shortening in 9 of 15. Afterload was elevated in 7 of 15. The mean forced vital capacity (FVC) preoperatively was 45.3 +/- 15.9% with continuing diminution to 28.7 +/- 14.9% at 3.3 +/- 2.2 years after surgery. The main benefit of surgical stabilization is the relative ease and comfort of wheelchair seating compared with those nonoperated patients who develop progressive deformity. We have not seen lasting improvement or stabilization in FVC following surgery as decreasing function is related primarily to muscle weakness.

Duchenne's cardiomyopathy in a canine model: electrocardiographic and echocardiographic studies

Thirteen dogs affected with X-linked Duchenne's muscular dystrophy and 11 female carrier dogs were studied by electrocardiography (ECG) and echocardiography. Twelve of the affected dogs were studied as immature animals and followed at 1 to 6 month intervals until they were 7 to 46 months of age. Compared with control dogs, affected dogs had significantly increased (p less than 0.02) Q/R ratios in ECG leads II, III, aVF, CV6LL (V2) and CV6LU (V4). Carrier dogs had significantly increased (p less than 0.02) Q/R ratios in leads V2 and V4. The Q/R ratio increased in three of six dogs followed up from age 6 months to greater than 2 years. The PR intervals were significantly shorter (p less than 0.02) in affected dogs. Ventricular arrhythmias were identified in four of six mature affected dogs. Two-dimensional echocardiography revealed distinctive hyperechoic lesions in 12 of the 13 affected dogs and in 6 of the 11 carrier dogs. Hyperechoic lesions corresponded to calcified myocardium and surrounding dense connective tissue. This study establishes the dog affected with Duchenne's muscular dystrophy as an animal model of Duchenne's cardiomyopathy and demonstrates that the heart in carrier dogs is affected by the dystrophic process.

The heart in muscular dystrophy: an electrocardiographic and ultrasound study of 20 patients

Twenty patients with different types of muscular dystrophy (MD) were included in a cross-sectional study by means of electrocardiography and ultrasound cardiography. A manifest cardiomyopathy was detected in 8 patients; a latent cardiomyopathy was found in 4. A hypertrophic cardiomyopathy was especially frequent in facioscapulohumeral MD, a congestive cardiomyopathy in Becker-Kiener MD. The ECG showed a reduction in the QT interval and frequent block formers in the X-chromosomal inherited forms and the trunc-girdle form. Bradycardia and a prolonged QT interval were frequent in myotonic dystrophy and facioscapulohumeral MD. Signs of cardiac infarction in the ECG were most frequent in the trunc-girdle forms. A high cardiac output per minute in conjunction with increased left ventricular volume was frequent in Becker-Kiener and Landouzy MD. A left ventricular dysfunction with reduced ejection was characteristic of myotonic dystrophy and trunc-girdle MD. A mitral valve prolapse was more frequent with increasing severity of the muscle disease and was particularly frequent in myotonic dystrophic and Landouzy MD. The cardiac output per minute and the stroke volume were significantly lower (P less than or equal to 0.03) where a mitral valve prolapse was present.

Marked cardiac involvement in limb-girdle muscular dystrophy

A 42-year-old man with limb-girdle muscular dystrophy who showed prominent cardiac involvement is described. He was treated for and diagnosed with dilated cardiomyopathy before admission. Initially, no overt feature of muscular dystrophy was evidenced, but serum enzymes were elevated. During the 2-year follow-up period, distinct features of muscular dystrophy appeared, and muscle biopsy confirmed the diagnosis. He was regarded as experiencing a sporadic occurrence. Because some patients diagnosed with and treated for dilated cardiomyopathy may have similar results, this form of muscular dystrophy should be recognized as occasionally associated with cardiac muscle disease.

Cardiac involvement in congenital myotonic dystrophy

Seven young patients (mean age 19 years 8 months) with congenital myotonic dystrophy and with defined symptoms at birth were investigated by electrocardiography and echocardiography. None had cardiovascular symptoms. Electrocardiograms or echocardiograms or both were abnormal in all patients. Atrioventricular and intraventricular conduction defects were the most common electrocardiographic abnormalities and were seen in five patients. The echocardiographic examinations showed impaired left ventricular systolic function in one patient. Other echocardiographic findings were a small left ventricle and atrium, minor valve defects, and mitral valve prolapse. This study shows that the heart is often affected in young patients with congenital myotonic dystrophy. The specialised conduction system is often affected and so too is the myocardium, causing impaired systolic function.

Neurologic aspects of mitral valve prolapse

Mitral valve prolapse (MVP), the most frequently encountered valvular condition in the population, has been reported in an increasing variety of neurologic, muscular, and psychiatric disorders during the last twelve years. Extensive review of reports indicates this has resulted from observations of either (1) inordinate incidence of MVP in well-defined neurologic entities or (2) development of neurologic or ophthalmologic complications attributed to MVP. In the review presented, basis is found for categorizing MVP by its association with (1) well-defined, genetically determined neurologic disorders; (2) disorders characterized by structural abnormalities, many genetically determined, or inflammatory processes of connective tissues; (3) "mechanical" prolapse resulting from disproportion of mitral valve annulus and left ventricular size, which is, at times, reversible; and (4) a generally asymptomatic state that, at times, is associated with ischemic, thrombotic, embolic, and infectious disorders of the brain and eye. The paradox between the large number of persons with MVP in the general population who remain healthy and a subpopulation of patients with complications of MVP (eg, stroke) or other entities has been identified. A second paradox is found between the well-known increased incidence of MVP, especially in young patients with stroke, and the apparent rarity of stroke among patients with both common (eg, migraine) and unusual (eg, myotonic dystrophy) neurologic entities in which an extraordinary high prevalence of MVP is known to exist.

Autonomic function and the sinus tachycardia of Duchenne muscular dystrophy

The cardiovascular autonomic function of 13 boys with Duchenne muscular dystrophy was examined in order to test the hypothesis that the labile sinus tachycardia of that disorder is due to autonomic dysfunction. Five non-invasive procedures evaluated the responses of heart rate and blood pressure to postural change, the Valsalva maneuver, sustained hand grip and deep breathing. No individual had sufficient evidence of autonomic dysfunction. Most tests were normal (76%), 16% were borderline, and 8% were abnormal. None had more than one abnormal test. Although most had some difficulty with the Valsalva maneuver, the study demonstrated that simple clinical non-invasive testing of autonomic function can be carried out on a young severely handicapped population.

Gated radionuclide ventriculography in the evaluation of cardiac function in Duchenne's muscular dystrophy

Left ventricular ejection fractions were determined in 38 patients with Duchenne's muscular dystrophy. No significant correlation between the severity of respiratory dysfunction or age and cardiac function was seen. We suggest that the cardiac status of each patient should be evaluated separately from his respiratory status, particularly when long-term assisted ventilation is being considered.

Electrocardiographic findings in myotonic dystrophy

Sixty five patients with myotonic dystrophy, from a defined population in northern Sweden with an extremely high prevalence of this disease, were examined by electrocardiography. The patients were subdivided into three groups according to the severity of the disease. Abnormal electrocardiograms were found in 6 (35%) patients with mild disease, 12 (50%) patients with moderate disease, and 23 (96%) patients with severe disease. First degree atrioventricular block and left anterior hemiblock were the most commonly encountered abnormalities in patients with mild and moderate disease, whereas atrial fibrillation and flutter, abnormal Q waves, and repolarisation abnormalities were more common in patients with severe disease. This study shows that the heart is often affected by myotonic dystrophy. These effects can be detected by electrocardiography in early and mild forms of the disease. The effect on the heart is progressive and clinically important atrial arrhythmias and electrocardiographic abnormalities which are useful in differential diagnosis are common in severe forms of the disease.

Cardiomyopathy of Duchenne muscular dystrophy

A total of 18 male patients with Duchenne muscular dystrophy (DMD), aged 8-29 years (mean, 15.7 years), were prospectively studied to assess the cardiomyopathy associated with DMD, using clinical parameters and noninvasive cardiovascular investigations: electrocardiogram (ECG), Holter monitoring, and echocardiography. In addition, five clinical tests of cardiovascular autonomic function were used to assess the role of the autonomic nervous system in the pathogenesis of dysrhythmias. The majority of subjects were asymptomatic, but four had abnormal physical findings. All had abnormal ECG, the commonest abnormality (in 16) being tall R waves or increased R/S ratios in the right precordial leads; 14 had abnormal findings on echocardiography, including three with poor left ventricular function and five with mitral valve prolapse (MVP). Labile abrupt sinus tachycardia was present in 11, and four had high-grade ventricular ectopy. None had definite clinical evidence of autonomic dysfunction. The cardiomyopathy of DMD appears to be unrelated to disease severity. However, abnormal Q waves or Q/R ratios in ECG leads I, aVL9 and V5-V6 are significantly related to young age (p less than 0.05), and high-grade ventricular ectopy occurred significantly more frequently (p less than 0.05) in older subjects (greater than 15 years). Dysrhythmias were not related to the presence of MVP, poor left ventricular function, or autonomic dysfunction.

Cardiac abnormalities in myotonic dystrophy. Electrocardiographic and echocardiographic findings in 65 patients and 34 of their unaffected relatives. Relation with age and sex and relevance for gene detection

Sixty-five patients with a definite diagnosis of myotonic dystrophy (MD) and 34 of their presumably unaffected relatives were examined cardiologically, including ECG in all and echocardiography in 61 and 32 persons respectively, in order to investigate the frequency of cardiac abnormalities, their clinical importance and their potential value as a preclinical marker in the diagnosis of MD. Atrioventricular conduction (AVC) abnormalities were found in 18/33 (54%) of affected males and in only 5/32 (16%) of affected females (P = 0.0025). Intraventricular (IVC) conduction abnormalities were encountered with similar frequency in both sexes: in 12/33 (36%) of affected males and 10/32 (31%) of affected females. Mitral valve prolapses (MVP) were seen more often in affected females: 9/31 (29%) of affected males vs 15/30 (50%) of affected females have MVP (P = 0.16). A previously undescribed finding was that of pericardial effusions in 5 affected and in 1 unaffected person. All affected males with MVP also had conduction abnormalities, but cardiac findings were not interrelated otherwise. None of the cardiac abnormalities mentioned were age-related. Only 8/65 (12%) of patients had cardiac symptoms, all of which were the result of conduction defects. As far as can be judged from a transversal study, the value of cardiac examination of this kind as a preclinical test for the diagnosis of MD is modest. It is argued that IVC-abnormalities, but not AVC-disturbances or MVP, in clinically unaffected relatives may indicate that they are preclinical heterozygotes. The significance of pericardial effusion for the diagnosis of MD awaits further evaluation.

Intellectual function in muscular dystrophies

Intellectual function was studied in 28 boys with Duchenne dystrophy, 12 patients with facioscapulohumeral-type and 10 patients with limb-girdle-type muscular dystrophy. A definite relationship between intelligence level and the type of muscle disease was found. The more severe the genetic damage manifested by the rapidity of progression of muscular dystrophy the more definite the affection of the CNS manifesting as mental deficit. The factors influencing the level and structure of intelligence seem to exert their effect before the manifestation of muscle lesions.

Mitral valve prolapse in myotonic dystrophy

Forty-three patients with myotonic dystrophy (MyD) and 43 age- and sex-matched controls were prospectively evaluated for mitral valve prolapse (MVP) using both cardiac auscultation and echocardiography (ECHO). Prevalence of MVP was significantly increased in MyD patients when using either abnormal auscultation plus abnormal ECHO (23.3%, P less than 0.02) or abnormal ECHO alone (30%, P less than 0.01) as diagnostic criteria for MVP. Frequency of MVP was even more increased in patients with a thin, flat chest compared with patients with normal physical appearance (P less than 0.007). These findings are in support of the concept that the increased frequency of MVP in neuromuscular disorders is likely due to geometrical changes of the heart caused by thorax deformities, rather than structural changes of the mitral valve. For this reason, MVP in MyD probably belongs to the entity of so-called benign, secondary MVP. This is further supported by the absence of symptoms of "systemic" complications of MVP in our patient population.

Biochemical rationale and the cardiac response of patients with muscle disease to therapy with coenzyme Q10

Cardiac disease is commonly associated with virtually every form of muscular dystrophy and myopathy. A double-blind and open crossover trial on the oral administration of coenzyme Q10 (CoQ10) to 12 patients with progressive muscular dystrophies and neurogenic atrophies was conducted. These diseases included the Duchenne, Becker, and limb-girdle dystrophies, myotonic dystrophy, Charcot-Marie-Tooth disease, and Welander disease. The impaired cardiac function was noninvasively and extensively monitored by impedance cardiography. Solely by significant change or no change in stroke volume and cardiac output, all 8 patients on blind CoQ10 and all 4 on blind placebo were correctly assigned (P less than 0.003). After the limited 3-month trial, improved physical well-being was observed for 4/8 treated patients and for 0/4 placebo patients; of the latter, 3/4 improved on CoQ10; 2/8 patients resigned before crossover; 5/6 on CoQ10 in crossover maintained improved cardiac function; 1/6 crossed over from CoQ10 to placebo relapsed. The rationale of this trial was based on known mitochondrial myopathies, which involve respiratory enzymes, the known presence of CoQ10 in respiration, and prior clinical data on CoQ10 and dystrophy. These results indicate that the impaired myocardial function of such patients with muscular disease may have some association with impaired function of skeletal muscle, both of which may be improved by CoQ10 therapy. The cardiac improvement was definitely positive. The improvement in well-being was subjective, but probably real. Likely, CoQ10 does not alter genetic defects but can benefit the sequelae of mitochondrial impairment from such defects. CoQ10 is the only known substance that offers a safe and improved quality of life for such patients having muscle disease, and it is based on intrinsic bioenergetics.

Cardiac involvement in myotonic muscular dystrophy (Steinert's disease): a prospective study of 25 patients

The presence, degree and frequency of disorders of cardiac conduction and rhythm and of regional or global myocardial dystrophy or myotonia have not previously been studied prospectively and systematically in the same population of patients with myotonic dystrophy. Accordingly, 25 adults with classic Steinert's disease underwent electrocardiography, 24-hour ambulatory electrocardiography, vectorcardiography, chest x-rays, echocardiography, electrophysiologic studies, and technetium-99m angiography. Clinically important cardiac manifestations of myotonic dystrophy reside in specialized tissues rather than in myocardium. Involvement is relatively specific, primarily assigned to the His-Purkinje system. The cardiac muscle disorder takes the form of dystrophy rather than myotonia, and is not selective, appearing with approximately equal distribution in all 4 chambers. Myocardial dystrophy seldom results in clinically overt ventricular failure, but may be responsible for atrial and ventricular arrhythmias. Since myotonic dystrophy is genetically transmitted, a primary biochemical defect has been proposed with complete expression of the gene toward striated muscle tissue, whether skeletal or cardiac. Specialized cardiac tissue and myocardium have close, if not identical, embryologic origins, so it is not surprising that the genetic marker affects both. Cardiac involvement is therefore an integral part of myotonic dystrophy, targeting particularly the infranodal conduction system, to a lesser extent the sinus node, and still less specifically, the myocardium.

Mitral valve prolapse related to geometrical changes of the heart in cases of progressive muscular dystrophy

The significance of geometrical changes of the heart for the development of mitral valve prolapse (MVP) was studied by echocardiograms and chest x-ray films in 58 cases of progressive muscular dystrophy (PMD). The incidence of MVP was significantly higher (p less than 0.001) in cases where the thoracic spine was straight or lordotic compared with cases of kyphotic thoracic spine. The flattening of the thorax associated with deformation of the thoracic spine was correlated with the left atrial dimension and left ventricular dimension (r = 0.62, r = 0.37, respectively; p less than 0.001), and MVP developed predominantly in cases with flattened thorax and small left atrial or left ventricular dimensions. The left atrial and left ventricular dimensions were significantly smaller in cases with MVP compared to cases without MVP (p less than 0.001, p less than 0.005, respectively). When both the left atrial and the left ventricular dimension shortened to certain levels, MVP was observed in almost all cases. From these results, it was suggested that the portion from the left atrium to the left ventricle was pressed by the forward bending of the thoracic spine, and the subsequent geometrical changes of the mitral ring and the left ventricle could produce redundancy of the chorda tendinea of the mitral valve, resulting in the occurrence of MVP.

Dystrophic degeneration of papillary muscle and ventricular myocardium. A basis for mitral valve prolapse in Duchenne's muscular dystrophy

The hearts of three children who died with Duchenne's progressive muscular dystrophy and features of mitral valve prolapse were examined to find if the valve disorder arose from cardiomyopathy due to the primary disease or from dystrophic changes in th mitral valve itself. Gross, histologic and ultrastructural features of mitral valve annulus, anterior and posterior leaflets, chordae tendineae, right and left ventricles, and anterior and posterior papillary muscles were compared with those of similar tissues from normal children of matched age and sex. Fibrosis and myofibrillar lysis--most extensive in posterior papillary muscle and in the posterobasal segment of the left ventricle--were the main histopathologic findings. Myofibrillar lysis was characterized by a total loss of actin and myosin myofilaments. By contrast, the mitral valve annulus, its leaflets and the origin, distribution pattern, length and thickness of chordae tendineae were entirely normal. These observations establish that mitral valve prolapse syndrome in Duchenne's dystrophy is an expression of cardiomyopathy involving papillary muscle and ventricular myocardium rather than a result of dystrophic changes in the mitral valve leaflets, annulus or chordae tendineae.