Cardiac conduction abnormalities and StokesAdams attacks in myotonic dystrophy C. NOEL, MD, M sc, FRcPIIc]; R.M. GAGNON, MD, FRCP[C]

Myotonic dystrophy is a well known cause of cardiomyopathy. While various cardiac conduction abnormalities have been described in patients with myotonic dystrophy, so far only sporadic cases of Stokes-Adams attacks have been reported. Of 27 patients with this disease various conduction disturbances were detected in 17 (630/o), 5 of whom presented with Stokes-Adams attacks and were found to have intracardiac conduction defects. The prognosis in four of the five patients was greatly improved with permanent pacemaker implantation.

though no specific lesion has been plete right bundle branch block and described.14 However, fatty infiltra- left anterior fascicular block. In 1975 a first-degree atrioventricular tion and fibrosis of the conduction block was noted (PR interval 0.26 secpathways have been reported.7'8 In onds). In February 1977 a permanent addition, ventricular and supraventri- pacemaker implanted. The electrocular arrhythmias have been noted." cardiogram was before implantation showed We describe five patients with well first-degree atrioventricular block (PR documented myotonic dystrophy and interval 0.26 seconds), complete right Stokes-Adams attacks secondary to bundle branch block (QRS interval 0.18 cardiac conduction abnormalities. seconds) and left anterior fascicular

pronostic chez quatre de ces cinq patients a 6t6 sensiblement ameliore par Ia pose d'un stimulateur cardiaque.

patients.

Patients

block (Fig. 1). Since then he has remained asymptomatic.

Among 27 patients with myotonic Case 2 dystrophy hospitalized at our instituA 47-year-old woman was hospitaltion from 1970 to 1976, 17 (63%) La dystrophie myotonique est une ized in 1972 for a first episode of had electrocardiographic evidence of cause bien connue de cardiomyopathie. There was no history of other conduction abnormalities (Table I). syncope. Si plusleurs perturbations de Ia cardiac abnormalities or symptoms. The mean age was 43 years and the conduction cardiaque ont ete decrites Myotonic dystrophy was diagnosed. chez des patients souffrant de dystrophie range 24 to 63 years. The main physical findings were muscle myotonique, jusqu'A maintenant seuls Five of the patients presented with weakness, myotonia, lack of facial exquelques cas isoles de syndrome de Stokes-Adams attacks. One patient, pression with atrophy of the facial and Stokes-Adams ont 6t6 signales. Sur aged 40 years, had a left anterior neck muscles, decreased tendon reflexes 27 patients atteints de cette maladie fascicular block in 1972 and asystole and nasal voice. The only cardiovasdivers troubles de Ia conduction ont 2 years later; he was resuscitated but cular abnormality revealed by physical 6t6 deceles chez 17 (630/c), dont 5 ont died shortly afterwards of intractable examination was bradycardia. An elecpr6sent6 un syndrome de Stokes-Adams ventricular arrhythmias. We describe trocardiogram showed 2: 1 atrioventriet chez qui on a retrouve des anomalies below in more detail the other four cular block, with a ventricular rate of de Ia conduction intracardiaque. Le 37 beats/mm, and complete left bundle

Myotonic dystrophy (Steinert's disease), as with some other neuromuscular diseases, has been reported to be associated with cardiomyopathy.14 While in patients with myotonic dystrophy heart failure is rare' and responds well to treatment, cardiac conduction abnormalities are much more frequent and may be lethal.2 The prognosis for patients with conduction defects can be improved with permanent pacemaker implantation. Griffith,6 in 1911, was the first to describe a patient with myotonic dystrophy, irregular heart rhythm and bradycardia. Since then several reports have established the relation between myotonic dystrophy and cardiac conduction abnormalities, al-

Case 1 A 52-year-old man was first seen for myotonic dystrophy in 1974. During the previous few years he had experienced many Stokes-Adams atttacks for which he had never consulted a physician. He denied other cardiovascular symptoms. Muscle weakness, myotonia. decreased tendon reflexes, cataracts, baldness and a nasal voice were noted. Physical examination revealed no cardiovascular abnormalities and a chest roentgenogram was normal. An electrocardiogram disclosed com-

From the department of medicine, University of Montreal, Notre-Dame Hospital, Montreal Reprint requests to: Dr. C. Noel, Department of medicine, Notre-Dame Hospital, 1560 Sherbrooke St. E, Montreal, PQ H2L 4K8 1402 CMA JOURNAL/JUNE 10, 1978/VOL. 118

branch block (QRS interval 0.16 seconds). A chest roentgenogram was normal. A permanent pacemaker was implanted subsequently. In January 1977, a few months after routine insertion of a third pacemaker, the patient was admitted with recurrence of Stokes-Adams attacks, complete atrioventricular block and a slow ventricular rate secondary to malfunctioning of the pulse generator. Mild left heart failure subsided with diuretic therapy and insertion of a new pacemaker. Her neurologic condition is now stable but she has slowly progressive bilateral cataracts. Case 3

A 49-year-old man had been treated for myotonic dystrophy since the age of 37 years, when an electrocardiogram disclosed incomplete right bundle branch block. In 1970 he was admitted to the emergency room with syncope. An elec-

trocardiogram showed complete atrioventricular block, then suddenly ventricular fibrillation. Immediate cardioversion reverted the cardiac rhythm to 3:1

atrioventricular block, with a ver,tricular rate of 35 beats/mm (Fig. 2). Temporary pacing was instituted and

a permanent pacemaker was implanted a few days later. The usual findings of myotonic dystrophy - muscle weakness, mainly of the neck, myotonia, decreased tendon reflexes, cataracts, baldness and testicular atrophy - were found. There was no heart murmur or evidence of other cardiovascular abnormalities. A chest roentgenogram was normal. Since 1970 three other pulse generators have been installed and the patient continues to be free of cardiovascular symptoms and syncope. The dystrophy has not progressed. Case 4 A 40-year-old woman was admitted to the emergency room in February 1976 for two episodes of syncope. There was no history of cardiac abnormalities. An electrocardiogram showed 2:1 atrioventricular block, with a ventricular rate of 35 beats/mm, left axis deviation and complete left bundle branch block. Later the same day an electrocardiogram showed right bundle branch block and left posterior fascicular block as well as 2:1 atrioventricular block. A permanent pacemaker was implanted. A diagnosis of myotonic dystrophy was made from the typical findings of muscle weakness and

FIG.

1-Case

1:

First-degree

atrophy, myotonia and some mental retardation. There was no evidence of other cardiovascular abnormalities. A chest roentgenogram was normal. Since then the patient has remained free of cardiovascular symptoms and syncope.

Discussion The four cases we have described in detail illustrate that conduction disturbances in myotonic dystrophy can be diffuse and severe. Indeed, three of the four patients had evidence of bifascicular disease in addition to atrioventricular block. Furthermore, in patient 1 the first-degree atrioventricular block in the presence

of bifascicular block probably signified involvement of the remaining fascicle, as demonstrated recently by

Levites and Haft;'0 they found that 72% of 89 patients with bifascicular block and first-degree heart block had a prolonged His-Q interval and therefore prolonged conduction in

secondary to advanced or complete transient atrioventricular block. Cases 1 and 3 demonstrate that these abnormalities can progress and that the complications can be prevented with appropriate follow-up assessment. Furthermore, in two patients the diagnosis of myotonic dystrophy was made after they had sought medical care because of Stokes-Adams attacks. In a study of 85 patients with myotonic dystrophy Fisch2 reported that 68.3% had electrocardiographic abnormalities and 91.3% of these had arrhythmias or conduction disturbances. In 1974 Gribbs" studied 25 myotonic patients, 17 of whom had conduction abnormalities; Hisbundle electrocardiograms showed infranodal block. Seven family members also had atrioventricular con-

duction abnormalities as the first manifestations trophy.'2

of

myotonic

dys-

In our patients the conduction abnormalities were the main feature of exact mechanism of the Stokes- the cardiomyopathy; none presented Adams attacks could not be demon- significant evidence of heart failure strated in patient 1 they were likely or increased heart size during followthe remaining fascicle. Although the

atrioventricular

block

(PR

interval

0.26

seconds),

complete

right

bundle

branch

block

(QRS interval 0.18 seconds) and left anterior fascicular block.

CMA JOURNAL/JUNE 10, 1978/ VOL. 118 1403

up assessment. In 1964 Orndahl and associates, in a review of the literature, found that only 7% of 195 patients with myotonic dystrophy had heart failure. They also reported 29 cases of myotonic dystrophy, in only 1 of which moderate heart failure was associated. Because the disease can follow a long and relatively benign course,'3 and in view of the low frequency of heart failure, the prognosis for these patients is greatly improved by permanent pacemaker implantation. The decision to insert a permanent pacemaker was easily made in all our patients because of the history of Stokes-Adams attacks and the conclusive electrocardiographic findings. When a permanent pacemaker should be implanted in asymptomatic patients with intraventricular conduction abnormalities has not been established; we hope that better followup of these patients will provide an answer to this question. However, in view of the threat of

sudden death and the impossibility References of predicting the outcome in asymp- 1. Ev.i.is W: The heart in myotonic tomatic patients with abnormal intraatrophica. Br Heart J 6: 41, 1944 cardiac conduction, it is reasonable 2. FISCH C: The heart in dystrophia myotonica. Am Heart J 41: 525, 1951 to consider His-bundle studies in paSC: The heart in myotonia tients with bifascicular block. A per- 3. CHURCH atrophica. Arch intern Med 119: 176, manent pacemaker may be indicated 1967 for those with a long His-Q interval, 4. DEWIND LT, JONES RJ: Cardiovascular observations in dystrophia myofor this may be a sign of impending tonica. JAMA 144: 299, 1950 complete heart block.14 Those with 5. ORNDAHL G, THULESIUS 0, ERNESa normal His-Q interval should be TROM 5, et al: The heart in myotonic closely followed by repeated electrodisease. Acta Med Scand 176: 479, cardiography and probably by am1964 bulatory electrocardiographic mon- 6. GRIFFITH TW: On myotonia. Q J Med 5: 229, 1911/12 itoring at regular intervals. Finally, KENNEL AJ, TITUS JL, MERIDETH J: electrocardiographic abnormalities 7. Pathologic findings in the atrioventrishould be looked for in the families cular conduction system in myotonic of these patients because, as Holt dystrophy. Mayo Clin Proc 49: 838, 1974 and Lambert reported,'5 they can AMP: Dystrophia cordis antedate other features of the dis- 8. THOMSON myotonica studied by serial histology ease, although the neurologic maniof the pacemaker and conducting sysfestations usually precede the onset tem. I Pathol Bacteriol 96: 285, 1968 of cardiac symptoms. 9. CLEMENTS SD JR, COLMERS RA, HURST JW: Myotonia dystrophica. We thank Drs. J.G. Lemire and R.A. Ventricular arrhythmias, intraventricuNadeau for reviewing our manuscript, lar conduction abnormalities, atrioand Miss J. Guilbault for secretarial ventricular block and Stokes-Adams assistance. attacks successfully treated with permanent transvenous pacemaker. Am J Cardiol 37: 933, 1976 10. LEVITES R, HAFT JI: Significance of first degree heart block (prolonged PR interval) in bifascicular block. Am I Cardiol 34: 259, 1974 11. GRIBBS RC: Hypertrophy and cardiomyopathy in the neuromuscular discases. Circulation Res 35 (suppl 2): 11-145, 1974

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12. GRIBBS RC, DAVIS RJ, ANDERSON D:

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Cardiac conduction abnormalities in myotonic dystrophy (abstr). Ann intern Med 78: 819, 1973 13. ELLIOT FA: Clinical Neurology, 2nd ed, Saunders, Philadelphia, 1971, p 451 14. Vm. Z, MASON DT, FLETCHER RD, et al: Prolonged His-Q interval in chronic bifascicular block: relation to impending complete heart block. Circulation 53: 46, 1976 15. HOLT JM, LAMBERT EHN: Heart disease as the presenting feature in myotonia atrophica. Br Heart 1 26: 433, 1964

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FIG 2-Case 3, following cardioversion of ventricular fibrillation: 3:1 atrioventricular block with ventricular rate of 35 beats/mm and ventricular premature beats; remainder of electrocardiogram normal. 1404 CMA JOURNAL/JUNE 10, 1978/VOL. 118

LIVING WITH ASTHMA IN ADULT LIFE. K. Michael Hume. 60 pp. The Chest, Heart and Stroke Association, London, 1978. $5, paperbound. ISBN 0-901548-43-X NCHS GROWTH CURVES FOR CHILDREN BIRTH-lB YEARS, UNITED STATES. Vital and Health Statistics. Series 11, No. 165. National Center for Health Statistics. 74 pp. lIlust. U.S. Department of Health, Education, and Welfare, Public Health Service, Hyattsville, 1978. Price not stated, paperbound. DHEW pubi no (PHS) 78-1650 continued on page 1417

Cardiac conduction abnormalities and Stokes-Adams attacks in myotonic dystrophy.

Cardiac conduction abnormalities and StokesAdams attacks in myotonic dystrophy C. NOEL, MD, M sc, FRcPIIc]; R.M. GAGNON, MD, FRCP[C] Myotonic dystrop...
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