Cardiac abnormalities in myotonic dystrophy. Electrophysiologic and histopathologic studies

Focal right atrial dysplasia and atrial flutter in a patient with myotonic dystrophy

Focal dysplasia of the right atrium was identified postmortem in a 22-year-old man with myotonic dystrophy and sudden death. Antemortem cardiac abnormalities included a single syncopal episode associated with atrial flutter with exercise-induced 1:1 atrioventricular conduction, sinus node dysfunction, and mild mitral valve prolapse. Pathologically there was only mild conduction system disease and the ventricular myocardium was normal. Right atrial dysplasia, previously unreported in myotonic dystrophy, appears to have been an arrhythmogenic lesion in this patient, serving as a morphological substrate for reentry.

Prevalence of intraventricular block in the general population: the Framingham Study

QRS intervals in the ECGs of members of the Framingham Heart Study cohort and offspring were measured to provide an estimate of the prevalence of intraventricular block in the general population. Intervals of greater than or equal to 0.09 second appear in men twice as commonly as in women, are rare before age 50 to 60, and shift from a predominance of right bundle branch block in the young to an indeterminate pattern in the elderly. Complete intraventricular block (QRS interval greater than or equal to 0.12 second) is seen in 11% of elderly men and 5% of elderly women. Aside from age and sex, logistic regression indicates strong associations with concurrent manifestations of coronary heart disease, congestive heart failure, and atrioventricular block, as well as hypertension, left ventricular hypertrophy, and ventricular extrasystoles. Among those subjects free of clinical coronary disease and congestive heart failure, associations between QRS interval and age, sex, atrioventricular block, and ECG left ventricular hypertrophy remain significant by multivariate analysis. Whether people with prolonged QRS intervals need special monitoring or attention cannot be told from these data.

Pathology of the cardiac conduction system in myotonic dystrophy: a study of 12 cases

In 12 autopsy cases of myotonic dystrophy, the most frequently observed histopathologic lesions of the cardiac conduction system were fibrosis, fatty infiltration and atrophy. Fibrosis involved the sinus node in 6 cases, atrioventricular (AV) node in 7, AV bundle in 8, bundle branches in 10 and ventricular myocardium in 11. Fatty infiltration was observed in the sinus node in two cases, AV node in two, AV bundle in six, bundle branches in one and ventricular myocardium in nine. Atrophy was prominent in the AV bundle in five and bundle branches in eight. Lymphocytes infiltrated the conduction system in three cases and were associated with myotonic dystrophy in two and varicella myocarditis in one. Ventricular myocytes were hypertrophied in seven cases, vacuolated in three and exhibited disarray in two. The distribution and extent of conduction system lesions tended to correspond to antemortem electrocardiographic abnormalities, including prolonged PR interval in six cases, intraventricular conduction delay in six and bundle branch block in four. Cardiac involvement by myotonic dystrophy may have contributed to sudden death in four cases.

Myotonic dystrophy: ambulatory electrocardiogram, electrophysiologic study, and echocardiographic evaluation

Myotonic dystrophy is frequently associated with functional and anatomic derangements in the myocardium. Ten myotonic dystrophy patients (seven men and three women, ages ranging from 35 to 58 years) were evaluated with a 12-lead ECG, 24-hour Holter monitor recording, invasive electrophysiologic studies, and echocardiographic examination. Nine patients displayed abnormalities in the conduction system. ECG and Holter monitor abnormalities were first-degree atrioventricular block (n = 8), second-degree atrioventricular block (n = 1) (Wenckebach type), complete left bundle branch block (n = 2), left anterior fascicular block (n = 5), left posterior fascicular block (n = 1), sinus bradycardia (n = 6), sick sinus syndrome (n = 2), frequent premature ventricular complexes (n = 4), and ventricular tachycardia (n = 2). Electrophysiologic study abnormalities included AH interval less than or equal to 140 msec (n = 7), AH interval greater than 140 msec (n = 3), HV interval greater than 60 msec (n = 9), and ventricular tachycardia induction (n = 1). Echocardiographic examination revealed mitral valve prolapse (n = 6). We conclude that diffuse conduction abnormalities were seen in a majority of our patients with myotonic dystrophy. Ventricular arrhythmias, including ventricular tachycardia, were seen in some of these patients, and mitral valve prolapse was a frequent finding.

Anesthesia for pediatric neurological and neuromuscular diseases

Children with neurological and neuromuscular diseases often present anesthetic problems in the perioperative period. The anesthetic technique can play a significant role in altering the state of the brain during neurosurgical procedures through effects on the cerebral circulation and metabolism. Pre-existing neuromuscular disease may also have specific anesthetic implications such as cardiorespiratory involvement (eg, myotonia dystrophica), the potential for drug interactions (eg, myasthenia gravis) or abnormal responses to commonly used drugs (eg, malignant hyperthermia). In this review, the perioperative anesthetic considerations in a number of common neurological and neuromuscular conditions in the pediatric patient are discussed.

Primary amyloidosis in a patient with myotonic dystrophy

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A family with myotonic dystrophy associated with diffuse cardiac conduction disturbances as demonstrated by His bundle electrocardiography

In a family with myotonic dystrophy, three siblings showing ECG abnormalities were subjected to His bundle ECG studies. The duration of the disease ranged from 9 to 24 years. All three siblings had prolonged HV intervals (His-Purkinje conduction times) of 70 to 80 msec. The sister with the shortest duration of the disease had second-degree atrioventricular (AV) nodal block as well as left posterior fascicular block, the younger brother had left anterior fascicular block, and the elder brother with the longest history had first-degree AV block without bundle branch or fascicular block. With regard to associated arrhythmias, however, the elder brother developed paroxysmal ventricular tachycardia, apparently due to reentry involving the right bundle branch system, whereas the younger brother and sister had sinus bradycardia alone. This study reveals the prevalence of diffuse conduction disturbances of the specialized conducting system in a family with myotonic dystrophy.

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.

Ventricular tachycardia and sudden death in myotonic dystrophy: clinical, electrophysiologic and pathologic features

A 37 year old man who presented with a cardiomyopathy, conduction defects and atrial and ventricular arrhythmias was found to have the neuromuscular manifestations of myotonic dystrophy. Despite implantation of a permanent cardiac pacemaker, antiarrhythmic drug therapy and antiarrhythmic surgery, sudden death occurred. The results of electrophysiologic studies, coronary arteriography and pathologic findings are described. This case confirms previous observations that ventricular arrhythmias, in addition to atrial arrhythmias and conduction disturbances, are cardiac manifestations of myotonic dystrophy and can lead to sudden death.

Endomyocardial biopsy: a review of the literature

A review of the literature relating to endomyocardial biopsy (EMB) is presented. This is considered important at this time since EMB is being utilized with increasing frequency, particularly for the diagnosis of myocarditis. The development of the technique is briefly outlined. Emphasis is placed on the clinical application of EMB in the various primary cardiomyopathies (dilated, hypertrophic, restrictive, and obliterative), the infiltrative secondary cardiomyopathies (amyloidosis, sarcoidosis, hemochromatosis), myocarditis, as well as such conditions as adriamycin cardiotoxicity, cardiac transplant rejection, and Kawasaki disease. More controversial application of EMB in primary mitral valve prolapse (Barlow's syndrome), idiopathic ventricular arrhythmias, and the elucidation of the enigmatic finding of angina with angiographically normal coronary arteries is detailed. Experience with immunological and biochemical investigation of biopsy material, as well as with virus isolation and drug assays in the myocardium, is alluded to. Complications encountered with this procedure are also discussed, and its future role is contemplated.

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.

Anaesthesia in babies with congenital dystrophia myotonica

The anaesthetic procedures used in two babies with congenital dystrophia myotonica are described, and the problems of providing anaesthesia in patients with the adult and congenital forms of the condition discussed.

Clinical and induced ventricular tachycardia in a patient with myotonic dystrophy

A 20 year old patient with myotonic dystrophy presented with hemodynamically significant ventricular tachycardia at a rate of 230 beats/min requiring cardioversion. Two days later, the identical tachycardia was reproducibly initiated and terminated in the electrophysiology laboratory using two extrastimuli in the right ventricle. Trials of procainamide and quinidine were not successful in controlling the induced rhythm and amiodarone was administered. On restudy with amiodarone, ventricular fibrillation was induced using a single extrastimulus. This case suggests that ventricular tachyarrhythmias may contribute to the known cardiac morbidity and mortality in myotonic dystrophy.

Ambulatory electrocardiographic recording in mild or moderate myotonic dystrophy and myotonia congenita (Thomsen's disease)

Ambulatory electrocardiographic recording (AER) was performed on 27 adult patients with mild or moderate myotonic dystrophy (MD) and in 12 adult patients with mild myotonia congenita (MC) to determine whether characteristic arrhythmias and conduction disturbances occur in the early stages of these myotonic disorders. In MD and MC, AER showed at least one finding regarded as normal in 93% and 0% of cases, respectively. The most common abnormalities in MD were first degree atrioventricular (A-V) block (in 70% of cases) and QTc greater than or equal to 0.46 s (in 33%). Abnormal sinus intervals and frequent second degree A-V block were rare, each occurring in 4% of patients. Ventricular tachycardia did not occur. It is concluded that signs of involvement of cardiac conductive tissue in the MD disease process are very common, even in the early stages. Delayed A-V conduction in the most common single finding. Sinus nodal dysfunction, severe disturbances in A-V conduction, and ventricular arrhythmias are not common in mild disease. Repeated AER is indicated, to evaluate whether conduction disturbances in MD are progressing.