527
paroxysms of coughing also promote survival of the microbial species by firing large inocula at a new host. There is little evidence of symptom-free carriers,1&-.20 and, if the microbe cannot be isolated by efficient attempts at swabbing and culture, there must be little risk of dangerous dissemination.5 Pertussis is acquired mainly from cases that are typical clinically.21 Erythromycin, if given for at least 14 days, may have some therapeutic effect before the paroxysmal stage develops,22 but there have been no controlled, blinded studies of erythromycin in prevention of pertussis transmission to exposed contacts.23 All these clues suggest that the incidence of pertussis in adults is low; and infected adults usually take adequate steps to minimise transmission when
coughing.24 If adults were a major reservoir of pertussis, how would the disease have been virtually eliminated in countries that have resorted to a compulsory course of infant vaccination starting at 3 months of age?-countries that were not influenced by the scare about vaccine brain-damage. There is still no evidence of a causal relation between pertussis vaccines and permanent neurological illness;25and confidence in their safety and efficacy is increasing. In Britain, for example, the infant vaccination rate has reached an all-time high of 87%.26 Within a decade, this would give substantial herd immunity to children aged 6 months to 10 years, in whom most pertussis infection occurs; tiny babies would be protected indirectly by the absence of disease in their siblings. However, in this issue (p 507) Booy et al warn of the potential threat to such herd immunity if vaccination starts before 3 months, as now happens in the UK and is recommended by the World Health Organisation in some developing countries. Except, perhaps, for occupational groups such as obstetric and paediatric doctors and nurses, there seems no reason to advise vaccination of adults. In particular, the use of acellular pertussis vaccine can not be justified until trials in millions of vaccinees27 have shown that it is no less safe and effective than the whole-cell vaccine of countries that meet the present recommendations. 1. Cherry JD, Brunell PA, Golden GS, Karzon DT. Report of the Task Force on Pertussis and Pertussis Immunization 1988. Pediatrics 1988; 81: 939-84. 2. Abbott JD, Macaulay ME, Preston NW. Bacteriological diagnosis of whooping cough. Association of Clinical Pathologists: broadsheet 105. London: British Medical Association, 1982. 3. Granström M, Olinder-Nielsen AM, Holmblad P, Mark A, Hanngren K. Specific immunoglobulin for treatment of whooping cough. Lancet 1991; 338: 1230-33. 4. Stott NCH, Davis RH. Pertussis vaccination and pseudo whooping cough. Br Med J 1981; 282: 1871. 5. Preston NW. Pertussis today. In: Wardlaw AC, Parton R, eds. Pathogenesis and immunity in pertussis. Chichester: Wiley, 1988: 1-18. 6. Adamson PC, Wu TC, Meade BD, Rubin M, Manclark CR, Pizzo PA. Pertussis in a previously immunized child with human immunodeficiency virus infection. J Pediatr 1989; 115: 589-92. 7. Centers for Disease Control. Pertussis surveillance: United States, 1986-1988. MMWR 1990; 39: 57-66. 8. Zackrisson G, Taranger J, Trollfors B. History of whooping cough in nonvaccinated Swedish children, related to serum antibodies to pertussis toxin and filamentous hemagglutinin. J Pediatr 1990; 116: 190-94.
9. Addiss DG, Davis JP, Meade BD, et al. A pertussis outbreak in a Wisconsin nursing home. J Infect Dis 1991; 164: 704-10. 10. Trollfors B, Rabo E. Whooping cough in adults. Br Med J 1981; 283: 696-97. 11. MacLean DW. Adults with pertussis. J R Coll Gen Pract 1982; 32: 298-300. 12. Mertsola J, Ruuskanen O, Eerola E, Viljanen MK. Intrafamilial spread of pertussis. J Pediatr 1983; 103: 359-63. 13. Robertson PW, Goldberg H, Jarvie BH, Smith DD, Whybin LR. Bordetella pertussis infection: a cause of persistent cough in adults. Med J Aust 1987; 146: 522-25. 14. Aoyama T, Goto R, Iwai H, Murase Y, Iwata T. Pertussis in the adult. Sixth International Symposium on Pertussis. Bethesda: United States Public Health Service (DHHS Publication no FDA 90-1162), 1990: 249-50 (abstr). 15. Mortimer EA. Pertussis and its prevention: a family affair. J Infect Dis 1990; 161: 473-79 16. Long SS, Welkon CJ, Clark JL. Widespread silent transmission of pertussis in families: antibody correlates of infection and symptomatology. J Infect Dis 1990; 161: 480-86. 17. Mulholland EK. Pertussis vaccine: a time-bomb? Lancet 1990; 335: 1592. 18. Krantz I, Alestig K, Trollfors B, Zackrisson G. The carrier state in pertussis. Scand J Infect Dis 1986; 18: 121-23. 19. Jenkinson D, Pepper JD. A search for subclinical infection during a small outbreak of whooping cough: implications for clinical diagnosis. J R Coll Gen Pract 1986; 36: 547-48. 20. Bass JW. Is there a carrier state in pertussis? Lancet 1987; i: 96. 21. Thomas MG, Lambert HP. From whom do children catch pertussis? Br Med J 1987; 295: 751-52. 22. Bass JW. Erythromycin for pertussis: probable reasons for past failures. Lancet 1985; ii: 147. 23. Health and Welfare Canada. Statement on management of persons exposed to pertussis and pertussis outbreak control. Canada Dis Weekly Rep 1990; 27: 127-30. 24. Williams WO. Whooping cough in adults. Br Med J 1981; 283: 1122. 25. Cherry JD. ’Pertussis vaccine encephalopathy’: it is time to recognize it as the myth that it is. JAMA 1990; 263: 1679-80. 26. White JM, Hobday S, Begg NT. ’COVER’ (Cover of vaccination evaluated rapidly): 19. Comm Dis Rep 1991; 1: R140. 27. Baxter DN, Gibbs ACC. How are the sub-unit pertussis vaccines to be evaluated? Epidemiol Infect 1987; 99: 477-84.
Antitachycardia devices The first reports of pacing for termination of tachycardia appeared in the 1960s1; and in the early 1980s, with the development of implantable antitachycardia pacemakers, long-term use of antitachycardia pacing became a practicable means of arrhythmia control. Yet, despite these developments, use of the technique was restricted to very small numbers of patients. Why was enthusiasm for long-term antitachycardia pacing so limited? The therapy is invasive and also time-consuming because the device has to be programmed individually. With atrial antitachycardia pacing there was the risk of atrial fibrillation and induction of ventricular fibrillation in patients with accessory pathways.With ventricular tachycardia the risk of heart rate accelerationwas felt to be unacceptable. Long-term efficacy of the technique was limited4 and, because attacks were terminated rather than prevented, symptoms were not always alleviated. For supraventricular arrhythmias introduction of radiofrequency methods for atrioventricular node modification and for ablation of accessory pathways has reduced the use of the technique even further. By contrast, a sharp increase in antitachycardia pacing for ventricular arrhythmias seems likely to occur as a result of the development of implantable cardioverter defibrillators (ICDs) with antitachycardia pacing
528
functions. Over 1000 such devices have been
implanted already, and with Food and Drug Administration approval of several such devices expected soon this number will increase dramatically. By providing rescue defibrillation or cardioversion in the event of tachycardia acceleration, these devices overcome many of the earlier objections. Initial reports have been favourable,s indicating a high success rate with infrequent induction of ventricular fibrillation. With this technique, acceleration of tachycardia remains a hazard,66 especially when the original ventricular rate is fast;7 and electrophysiological testing does not reliably indicate its likelihood.8 Subthreshold pacing may offer a means to terminate ventricular tachycardia without the risk of acceleration, but its efficacy has yet to be confirmed and it is not specifically available in current ICDs. Lest enthusiam for these combined devices should reach excessive heights, Johnson and Marchlinski9 have sounded a cautionary note in their account of two patients with these devices. One patient with mitral valve disease and a history of atrial fibrillation had an ICD inserted for ventricular tachycardia. A postoperative episode of atrial fibrillation triggered antitachycardia pacing, which induced ventricular tachycardia; after a further series of pacing interventions, a defibrillating shock successfully restored sinus rhythm. In a second patient sinus tachycardia triggered postoperative and induction of ventricular antitachycardia pacing tachycardia which then triggered a 500-V shock. Thus inappropriate delivery of antitachycardia pacing can be arrhythmogenic and may lead to progressively more aggressive intervention. Inappropriate delivery of therapy results from erroneous detection of a tachyarrhythmia and the highlights diagnostic limitations of existing ICDs which, without exception, use heart rate as their primary means of arrhythmia detection. When defibrillators were used only to treat ventricular fibrillation or very fast ventricular tachycardia, difficulties with this approach were infrequent. Since antitachycardia pacing is now used for slower ventricular tachycardias problems with sinus tachycardia or atrial fibrillation exceeding the heart rate threshold for arrhythmia detection have become more common. Some ICDs offer rate stability criteria to exclude inappropriate detection of atrial fibrillation and sudden-onset criteria to exclude sinus tachycardia, but their use has been limited, partly because of concerns that they may lessen the sensitivity of detection of ventricular tachycardia and partly because clinical data are lacking. Development of pressure sensing leadsl° or signal morphology processingll may eventually improve diagnostic capability. Thus, although the implantable defribillator has largely overcome concerns about the safety of antitachycardia pacing for ventricular arrhythmias,
still have reservations about widespread use. Antitachycardia pacing should always be "tuned" to suit the individual patient. Antiarrhythmic drug therapy to control the frequency of attacks, to reduce the risk of overlap with sinus tachycardia, and to inhibit atrial tachyarrhythmias is likely to be needed in we must
many
patients.
Ryan GF, Easley RM, Zaroff LI, Goldstein S. Paradoxical use of a demand pacemaker in treatment of supraventricular tachycardia due to the Wolff-Parkinson-White syndrome. Observation on termination of reciprocal rhythm. Circulation 1968; 38: 1037-43. 2. Lau CP, Cornu E, Camm AJ. Fatal and nonfatal cardiac arrest in patients with an implanted antitachycardia device for the treatment of supraventricular tachycardia. Am J Cardiol 1988; 61: 919-21. 3. Griffith MJ, Paul V, Garratt CJ, Ward J, Ward DE, Camm AJ. Two forms of back up defibrillation for antitachycardia pacing in ventricular tachycardia. Br Heart J 1990; 64: 97. 4. Kappenberger L, Valin H, Sowton E, et al. Multicenter long-term results of antitachycardia pacing for supraventricular tachycardia. Am J Cardiol 1989; 64: 191-93. 5. Fromer M, Schlapfer J, Fischer A, Kappenberger L. Experience with a new implantable pace-cardioverter-defibrillator for the therapy of recurrent sustained ventricular tachyarrhythmias: a step towards a universal tachyarrhythmia control device. PACE 1991; 14: 1288-98. 6. Schneider MAE, Siebels J, Duckeck W, Geiger M, Kuck KH. Antitachycardia pacing by pacer/defribillator devices in ventricular tachycardia: superior to low-energy cardioversion. Eur Heart J 1991; 1.
12: 364 (abstr). 7. Schöls W, Brachmann J, Schmitt
C, Kübler W. Relation of tachycardia
pacing. Eur Heart J 1991; 12: 418 (abstr). 8. Rankin AC, Zaim S, Powell A, et al. Anti-tachycardia pacemaker/ implantable cardioverter defibrillator in patients with drug-refractory ventricular tachycardia. Eur Heart J 1991; 12: 364 (abstr). 9. Johnson NJ, Marchlinski FE. Arrhythmias induced by device antitachycardia therapy due to diagnostic nonspecificity. JACC 1991; rate to success
of antitachycardia
18: 1418-25. 10. Sharma AD, Bennett TD, Erickson M, Klein GJ, Wee R, Guiraudon G. Right ventricular pressure during ventricular arrhythmias in humans: potential implications for implantable antitachycardia devices. JACC 1990; 15: 648-55. 11. Tooley MA, Davies DW, Nathan AW, Camm AJ. Recognition of multiple tachyarrhythmias by rate-independent means using a small microcomputer. PACE 1991; 14: 337-40.
The heart in myotonic dystrophy Myotonic dystrophy is the commonest muscular dystrophy of adult life with a prevalence of about 5 per 100 000.1 Apart from the neuromuscular manifestations, this disorder has multiple systemic effects including cataract, mental retardation, and cardiac involvement. A study and extensive review2 of 1967 showed that published work in electrocardiographic (ECG) abnormalities occurred in 202 of 236 patients; only 16% had cardiac symptoms,
half of which
were
attributed
to
arrhythmias. Although the reports may have been biased towards positive findings, prospective studies showed a similarly high prevalence of abnormal ECGs in symptom-free patients,3,4 mainly impaired conduction and supraventricular arrhythmias. Intracardiac electrophysiological studies revealed abnormalities in all areas of the conducting system, most commonly in the His-Purkinje system;3,5 this distribution correlates with the appearance of prolonged PR and QRS intervals. Overt primary myocardial involvement in
paroxysms of coughing also promote survival of the microbial species by firing large inocula at a new host. There is little evidence of symptom-free carriers,1&-.20 and, if the microbe cannot be isolated by efficient attempts at swabbing and culture, there must be little risk of dangerous dissemination.5 Pertussis is acquired mainly from cases that are typical clinically.21 Erythromycin, if given for at least 14 days, may have some therapeutic effect before the paroxysmal stage develops,22 but there have been no controlled, blinded studies of erythromycin in prevention of pertussis transmission to exposed contacts.23 All these clues suggest that the incidence of pertussis in adults is low; and infected adults usually take adequate steps to minimise transmission when
coughing.24 If adults were a major reservoir of pertussis, how would the disease have been virtually eliminated in countries that have resorted to a compulsory course of infant vaccination starting at 3 months of age?-countries that were not influenced by the scare about vaccine brain-damage. There is still no evidence of a causal relation between pertussis vaccines and permanent neurological illness;25and confidence in their safety and efficacy is increasing. In Britain, for example, the infant vaccination rate has reached an all-time high of 87%.26 Within a decade, this would give substantial herd immunity to children aged 6 months to 10 years, in whom most pertussis infection occurs; tiny babies would be protected indirectly by the absence of disease in their siblings. However, in this issue (p 507) Booy et al warn of the potential threat to such herd immunity if vaccination starts before 3 months, as now happens in the UK and is recommended by the World Health Organisation in some developing countries. Except, perhaps, for occupational groups such as obstetric and paediatric doctors and nurses, there seems no reason to advise vaccination of adults. In particular, the use of acellular pertussis vaccine can not be justified until trials in millions of vaccinees27 have shown that it is no less safe and effective than the whole-cell vaccine of countries that meet the present recommendations. 1. Cherry JD, Brunell PA, Golden GS, Karzon DT. Report of the Task Force on Pertussis and Pertussis Immunization 1988. Pediatrics 1988; 81: 939-84. 2. Abbott JD, Macaulay ME, Preston NW. Bacteriological diagnosis of whooping cough. Association of Clinical Pathologists: broadsheet 105. London: British Medical Association, 1982. 3. Granström M, Olinder-Nielsen AM, Holmblad P, Mark A, Hanngren K. Specific immunoglobulin for treatment of whooping cough. Lancet 1991; 338: 1230-33. 4. Stott NCH, Davis RH. Pertussis vaccination and pseudo whooping cough. Br Med J 1981; 282: 1871. 5. Preston NW. Pertussis today. In: Wardlaw AC, Parton R, eds. Pathogenesis and immunity in pertussis. Chichester: Wiley, 1988: 1-18. 6. Adamson PC, Wu TC, Meade BD, Rubin M, Manclark CR, Pizzo PA. Pertussis in a previously immunized child with human immunodeficiency virus infection. J Pediatr 1989; 115: 589-92. 7. Centers for Disease Control. Pertussis surveillance: United States, 1986-1988. MMWR 1990; 39: 57-66. 8. Zackrisson G, Taranger J, Trollfors B. History of whooping cough in nonvaccinated Swedish children, related to serum antibodies to pertussis toxin and filamentous hemagglutinin. J Pediatr 1990; 116: 190-94.
9. Addiss DG, Davis JP, Meade BD, et al. A pertussis outbreak in a Wisconsin nursing home. J Infect Dis 1991; 164: 704-10. 10. Trollfors B, Rabo E. Whooping cough in adults. Br Med J 1981; 283: 696-97. 11. MacLean DW. Adults with pertussis. J R Coll Gen Pract 1982; 32: 298-300. 12. Mertsola J, Ruuskanen O, Eerola E, Viljanen MK. Intrafamilial spread of pertussis. J Pediatr 1983; 103: 359-63. 13. Robertson PW, Goldberg H, Jarvie BH, Smith DD, Whybin LR. Bordetella pertussis infection: a cause of persistent cough in adults. Med J Aust 1987; 146: 522-25. 14. Aoyama T, Goto R, Iwai H, Murase Y, Iwata T. Pertussis in the adult. Sixth International Symposium on Pertussis. Bethesda: United States Public Health Service (DHHS Publication no FDA 90-1162), 1990: 249-50 (abstr). 15. Mortimer EA. Pertussis and its prevention: a family affair. J Infect Dis 1990; 161: 473-79 16. Long SS, Welkon CJ, Clark JL. Widespread silent transmission of pertussis in families: antibody correlates of infection and symptomatology. J Infect Dis 1990; 161: 480-86. 17. Mulholland EK. Pertussis vaccine: a time-bomb? Lancet 1990; 335: 1592. 18. Krantz I, Alestig K, Trollfors B, Zackrisson G. The carrier state in pertussis. Scand J Infect Dis 1986; 18: 121-23. 19. Jenkinson D, Pepper JD. A search for subclinical infection during a small outbreak of whooping cough: implications for clinical diagnosis. J R Coll Gen Pract 1986; 36: 547-48. 20. Bass JW. Is there a carrier state in pertussis? Lancet 1987; i: 96. 21. Thomas MG, Lambert HP. From whom do children catch pertussis? Br Med J 1987; 295: 751-52. 22. Bass JW. Erythromycin for pertussis: probable reasons for past failures. Lancet 1985; ii: 147. 23. Health and Welfare Canada. Statement on management of persons exposed to pertussis and pertussis outbreak control. Canada Dis Weekly Rep 1990; 27: 127-30. 24. Williams WO. Whooping cough in adults. Br Med J 1981; 283: 1122. 25. Cherry JD. ’Pertussis vaccine encephalopathy’: it is time to recognize it as the myth that it is. JAMA 1990; 263: 1679-80. 26. White JM, Hobday S, Begg NT. ’COVER’ (Cover of vaccination evaluated rapidly): 19. Comm Dis Rep 1991; 1: R140. 27. Baxter DN, Gibbs ACC. How are the sub-unit pertussis vaccines to be evaluated? Epidemiol Infect 1987; 99: 477-84.
Antitachycardia devices The first reports of pacing for termination of tachycardia appeared in the 1960s1; and in the early 1980s, with the development of implantable antitachycardia pacemakers, long-term use of antitachycardia pacing became a practicable means of arrhythmia control. Yet, despite these developments, use of the technique was restricted to very small numbers of patients. Why was enthusiasm for long-term antitachycardia pacing so limited? The therapy is invasive and also time-consuming because the device has to be programmed individually. With atrial antitachycardia pacing there was the risk of atrial fibrillation and induction of ventricular fibrillation in patients with accessory pathways.With ventricular tachycardia the risk of heart rate accelerationwas felt to be unacceptable. Long-term efficacy of the technique was limited4 and, because attacks were terminated rather than prevented, symptoms were not always alleviated. For supraventricular arrhythmias introduction of radiofrequency methods for atrioventricular node modification and for ablation of accessory pathways has reduced the use of the technique even further. By contrast, a sharp increase in antitachycardia pacing for ventricular arrhythmias seems likely to occur as a result of the development of implantable cardioverter defibrillators (ICDs) with antitachycardia pacing
528
functions. Over 1000 such devices have been
implanted already, and with Food and Drug Administration approval of several such devices expected soon this number will increase dramatically. By providing rescue defibrillation or cardioversion in the event of tachycardia acceleration, these devices overcome many of the earlier objections. Initial reports have been favourable,s indicating a high success rate with infrequent induction of ventricular fibrillation. With this technique, acceleration of tachycardia remains a hazard,66 especially when the original ventricular rate is fast;7 and electrophysiological testing does not reliably indicate its likelihood.8 Subthreshold pacing may offer a means to terminate ventricular tachycardia without the risk of acceleration, but its efficacy has yet to be confirmed and it is not specifically available in current ICDs. Lest enthusiam for these combined devices should reach excessive heights, Johnson and Marchlinski9 have sounded a cautionary note in their account of two patients with these devices. One patient with mitral valve disease and a history of atrial fibrillation had an ICD inserted for ventricular tachycardia. A postoperative episode of atrial fibrillation triggered antitachycardia pacing, which induced ventricular tachycardia; after a further series of pacing interventions, a defibrillating shock successfully restored sinus rhythm. In a second patient sinus tachycardia triggered postoperative and induction of ventricular antitachycardia pacing tachycardia which then triggered a 500-V shock. Thus inappropriate delivery of antitachycardia pacing can be arrhythmogenic and may lead to progressively more aggressive intervention. Inappropriate delivery of therapy results from erroneous detection of a tachyarrhythmia and the highlights diagnostic limitations of existing ICDs which, without exception, use heart rate as their primary means of arrhythmia detection. When defibrillators were used only to treat ventricular fibrillation or very fast ventricular tachycardia, difficulties with this approach were infrequent. Since antitachycardia pacing is now used for slower ventricular tachycardias problems with sinus tachycardia or atrial fibrillation exceeding the heart rate threshold for arrhythmia detection have become more common. Some ICDs offer rate stability criteria to exclude inappropriate detection of atrial fibrillation and sudden-onset criteria to exclude sinus tachycardia, but their use has been limited, partly because of concerns that they may lessen the sensitivity of detection of ventricular tachycardia and partly because clinical data are lacking. Development of pressure sensing leadsl° or signal morphology processingll may eventually improve diagnostic capability. Thus, although the implantable defribillator has largely overcome concerns about the safety of antitachycardia pacing for ventricular arrhythmias,
still have reservations about widespread use. Antitachycardia pacing should always be "tuned" to suit the individual patient. Antiarrhythmic drug therapy to control the frequency of attacks, to reduce the risk of overlap with sinus tachycardia, and to inhibit atrial tachyarrhythmias is likely to be needed in we must
many
patients.
Ryan GF, Easley RM, Zaroff LI, Goldstein S. Paradoxical use of a demand pacemaker in treatment of supraventricular tachycardia due to the Wolff-Parkinson-White syndrome. Observation on termination of reciprocal rhythm. Circulation 1968; 38: 1037-43. 2. Lau CP, Cornu E, Camm AJ. Fatal and nonfatal cardiac arrest in patients with an implanted antitachycardia device for the treatment of supraventricular tachycardia. Am J Cardiol 1988; 61: 919-21. 3. Griffith MJ, Paul V, Garratt CJ, Ward J, Ward DE, Camm AJ. Two forms of back up defibrillation for antitachycardia pacing in ventricular tachycardia. Br Heart J 1990; 64: 97. 4. Kappenberger L, Valin H, Sowton E, et al. Multicenter long-term results of antitachycardia pacing for supraventricular tachycardia. Am J Cardiol 1989; 64: 191-93. 5. Fromer M, Schlapfer J, Fischer A, Kappenberger L. Experience with a new implantable pace-cardioverter-defibrillator for the therapy of recurrent sustained ventricular tachyarrhythmias: a step towards a universal tachyarrhythmia control device. PACE 1991; 14: 1288-98. 6. Schneider MAE, Siebels J, Duckeck W, Geiger M, Kuck KH. Antitachycardia pacing by pacer/defribillator devices in ventricular tachycardia: superior to low-energy cardioversion. Eur Heart J 1991; 1.
12: 364 (abstr). 7. Schöls W, Brachmann J, Schmitt
C, Kübler W. Relation of tachycardia
pacing. Eur Heart J 1991; 12: 418 (abstr). 8. Rankin AC, Zaim S, Powell A, et al. Anti-tachycardia pacemaker/ implantable cardioverter defibrillator in patients with drug-refractory ventricular tachycardia. Eur Heart J 1991; 12: 364 (abstr). 9. Johnson NJ, Marchlinski FE. Arrhythmias induced by device antitachycardia therapy due to diagnostic nonspecificity. JACC 1991; rate to success
of antitachycardia
18: 1418-25. 10. Sharma AD, Bennett TD, Erickson M, Klein GJ, Wee R, Guiraudon G. Right ventricular pressure during ventricular arrhythmias in humans: potential implications for implantable antitachycardia devices. JACC 1990; 15: 648-55. 11. Tooley MA, Davies DW, Nathan AW, Camm AJ. Recognition of multiple tachyarrhythmias by rate-independent means using a small microcomputer. PACE 1991; 14: 337-40.
The heart in myotonic dystrophy Myotonic dystrophy is the commonest muscular dystrophy of adult life with a prevalence of about 5 per 100 000.1 Apart from the neuromuscular manifestations, this disorder has multiple systemic effects including cataract, mental retardation, and cardiac involvement. A study and extensive review2 of 1967 showed that published work in electrocardiographic (ECG) abnormalities occurred in 202 of 236 patients; only 16% had cardiac symptoms,
half of which
were
attributed
to
arrhythmias. Although the reports may have been biased towards positive findings, prospective studies showed a similarly high prevalence of abnormal ECGs in symptom-free patients,3,4 mainly impaired conduction and supraventricular arrhythmias. Intracardiac electrophysiological studies revealed abnormalities in all areas of the conducting system, most commonly in the His-Purkinje system;3,5 this distribution correlates with the appearance of prolonged PR and QRS intervals. Overt primary myocardial involvement in
