2
Annotations sudden deaths after myocardial infarction, Lancet 2:1563, 1974. 10. Amsterdam, E. A., Wolfson, S., and Gorlin, R.: Effect of the~'apy in angina pectoris, &nn. Intern. Med. 68:1151, 1968. 11. Lambert, D. M. D.: Beta-blockers and life expectancy in ischaemic heart disease, Lancet 1:793, 1972. 12. 13. Lambert, D. M.D.: Hypertension and myocardial infarc- tion, Br. Med. J. 3:685, 1974. Stewart, I. McD. G.: A prospective study of the compar- ative incidence of myocardial infarction in essential uncomplicated hypertensives under treatment contain- ing or excluding a beta-adrenergic blocking agent, Clin. Sci. Mol. Med. SUppl. 3 (In press 1976). The etiology of sino-atrial disorder (Sick Sinus Syndrome) Chronic sino-atrial disorder !Sick Sinus Syndrome) is being found in patients with increasing frequency, but its etiology remains a mystery. The acute form of the syndrome was ini- tially described after electrical reversion of cardiac arrhyth - mias, ~ but the commonest association in clinical practice is with myocardial infarction. Here, sinus bradycardia or sinus arrest with junctional takeover, sometimes associated with other disturbances of atrial rhythm, is often seen soon after inferior myocardial infarction> '~ Although normal sinus rhythm almost invariably returns if the patient survives, it is not unreasonable to suppose that the chronic form of sino- atrial disease might also be due to interference with the blood supply to the sinus node and atrium> ~'The report of features of coronary artery disease in 15 (48 per cent) of 31 patients with the bradycardia-tachycardia syndrome,~ supports this theory. However, we 0btained contrary results in the survey of' a larger group of patients initiated in Devon in 1968; the incidence of myocardial infarction in patients with complete block (a condition which was also once thought to be due to coronary artery disease) was 29 (13 per cent) out of 222 patients, whereas in sino-atrial disorder the incidence was 11 (10 per cent) of 106 cases.: 8 There are very few repo~'ts of postmortem studies of the specialized cardiac tissues or their blood supply in patients dying with chronic sino-atrial disorder, because of the diffi- culty in obtaining material with adequate clinical information and the laborious nature of the pathological technique. Several descriptions of individual cases emphasize the finding of atheroma with "arteriosclerosis" of the major coronary, or sinus node arteries with. or without associated sclerosis of the sino-atrial node and right atrium. "-:~ In a recent study of eight cases, the major coronary vessels were free from atheroma in seven and in the one case with atheroma the sino-atrial artery was spared and filled wel! with contrast media on postmortem angiography2:' In this series the histology of the sino,atrial node was grossly abnormal in seven instances. The node and atrium were heavily infiltrated with amyloid material in one case. In the Other six cases the specialised muscle cells in the sino-atrial node were very scanty or had virtually disappeared and the node was either Small or largely replaced with fibrous tissue. Warembourg and associates1~ described Complete destruction of all the connections which normally exist between atrial muscle and the sino-atrial node in their case and pathological changes in the atrial muscle of the sino-atrial approaches were found in all the eight cases described above. It has been suggested that some instances of sino-atrial disorder may be congenital 1~-~. '~ and it is tempting to regard the instances Of small and apparently atrophic sino-atrial nodes as being the result of a congenital abnormality. Nevertheless, the patients coming to autopsy were elderly, and a degenerative process would be equally possible. Again the fibrosis in the node and atrium may represent a non- specific end result of one of a number of past pathological processes such as pericarditis, rheumatic fever, or diphtheria. Scandinavian authors have incriminated diphtheria, ~, " but this is unlikely to be a common factor universally and in the Devon survey a history of diphtheria was found in only 9 per cent of patients with sino-atrial disorder, an incidence iden- tical to that found in patients with complete heart block. An auto-immune mechanism has been invoked as responsible for some cases of heart block TM and this may apply in sino-atrial disease. Certainly there are similarities between the two conditions~ 5o and conduction disturbances are common in sino-atrial disease,~ but the usual site of the block and the age distribution differ.~- It is dangerous to draw dogmatic conclusions concerning the effect that pathological changes may have upon the electrophysiology of the heart, particularly since the precise number and grouping of automatic cells required ~o form a pacemaking center in man are still unknown. Nevertheless, the gross reduction in number and density of the specialized muscle cells in the sino-atrial nodes of most patients with sino- atrial disease may predispose to failure of impulse formation or the generation elf a sub-threshold impulse? ~ Furthermore, the severe pathological changes in the sino-atria] node approaches imply that, contrary ~o previous theory,~' a phys- ical basis for sino-atrial block may exist. Undoubtedly in some instances of established sino-atrial disease the blood supply to the sino-atrial node remains intact and the degree of fibrosis is no more than can be expected from the normal ageing process.~ ~-~ Here. some extra-cardiac factor such as excessive vagal tones -~ -~ or a cerebral lesion.~ might be incriminated. However, such a mechanism seems unlikely, since far from atropine abolishing the dysrrhythmia in sino- atrial disorder, the response is usually subnormal. ~ ......... In one case, carcinomatous infiltration of the cardiac plexus was found at autopsy and it is possible that this might have increased the parasympathetic drive to the sinus node, although the author considered this unlikely. ''~ More likely alternatives would seem to be degeneration of the perinodaI American Heart Journal 539

The etiology of sino-atrial disorder (Sick Sinus Syndrome)

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Annotations

sudden deaths after myocardial infarction, Lancet 2:1563, 1974.

10. Amsterdam, E. A., Wolfson, S., and Gorlin, R.: Effect of the~'apy in angina pectoris, &nn. Intern. Med. 68:1151, 1968.

11. Lambert, D. M. D.: Beta-blockers and life expectancy in ischaemic heart disease, Lancet 1:793, 1972.

12.

13.

Lambert, D. M.D.: Hypertension and myocardial infarc- tion, Br. Med. J. 3:685, 1974. Stewart, I. McD. G.: A prospective study of the compar- ative incidence of myocardial infarction in essential uncomplicated hypertensives under t reatment contain- ing or excluding a beta-adrenergic blocking agent, Clin. Sci. Mol. Med. SUppl. 3 (In press 1976).

The etiology of sino-atrial disorder (Sick Sinus Syndrome)

Chronic sino-atrial disorder !Sick Sinus Syndrome) is being found in patients with increasing frequency, but its etiology remains a mystery. The acute form of the syndrome was ini- tially described after electrical reversion of cardiac arrhyth - mias, ~ but the commonest association in clinical practice is with myocardial infarction. Here, sinus bradycardia or sinus arrest with junctional takeover, sometimes associated with other disturbances of atrial rhythm, is often seen soon after inferior myocardial infarction> '~ Although normal sinus rhythm almost invariably returns if the patient survives, it is not unreasonable to suppose that the chronic form of sino- atrial disease might also be due to interference with the blood supply to the sinus node and atrium> ~' The report of features of coronary artery disease in 15 (48 per cent) of 31 patients with the bradycardia-tachycardia syndrome, ~ supports this theory. However, we 0btained contrary results in the survey of' a larger group of patients initiated in Devon in 1968; the incidence of myocardial infarction in patients with complete block (a condition which was also once thought to be due to coronary artery disease) was 29 (13 per cent) out of 222 patients, whereas in sino-atrial disorder the incidence was 11 (10 per cent) of 106 cases.: 8

There are very few repo~'ts of postmortem studies of the specialized cardiac tissues or their blood supply in patients dying with chronic sino-atrial disorder, because of the diffi- culty in obtaining material with adequate clinical information and the laborious nature of the pathological technique. Several descriptions of individual cases emphasize the finding of atheroma with "arteriosclerosis" of the major coronary, or sinus node arteries with. or without associated sclerosis of the sino-atrial node and right atrium. "-:~ In a recent study of eight cases, the major coronary vessels were free from atheroma in seven and in the one case with atheroma the sino-atrial artery was spared and filled wel ! with contrast media on postmortem angiography2:' In this series the histology of the sino,atrial node was grossly abnormal in seven instances. The node and atrium were heavily infiltrated with amyloid material in one case. In the Other six cases the specialised muscle cells in the sino-atrial node were very scanty or had virtually disappeared and the node was either Small or largely replaced with fibrous tissue. Warembourg and associates 1~ described Complete destruction of all the connections which normally exist between atrial muscle and the sino-atrial node in their case and pathological changes in the atrial muscle of the sino-atrial approaches were found in all the eight cases described above.

It has been suggested that some instances of sino-atrial disorder may be congenital 1~- ~. '~ and it is tempting to regard the instances Of small and apparently atrophic sino-atrial nodes as being the result of a congenital abnormality. Nevertheless, the patients coming to autopsy were elderly, and a degenerative process would be equally possible. Again the fibrosis in the node and atrium may represent a non- specific end result of one of a number of past pathological processes such as pericarditis, rheumatic fever, or diphtheria. Scandinavian authors have incriminated diphtheria, ~, " but this is unlikely to be a common factor universally and in the Devon survey a history of diphtheria was found in only 9 per cent of patients with sino-atrial disorder, an incidence iden- tical to that found in patients wi th complete heart block. An auto-immune mechanism has been invoked as responsible for some cases of heart block TM and this may apply in sino-atrial disease. Certainly there are similarities between the two conditions~ 5o and conduction disturbances are common in sino-atrial disease, ~ but the usual site of the block and the age distribution differ. ~-

It is dangerous to draw dogmatic conclusions concerning the effect that pathological changes may have upon the electrophysiology of the heart, particularly since the precise number and grouping of automatic cells required ~o form a pacemaking center in man are still unknown. Nevertheless, the gross reduction in number and density of the specialized muscle cells in the sino-atrial nodes of most patients with sino- atrial disease may predispose to failure of impulse formation or the generation elf a sub-threshold impulse? ~ Furthermore, the severe pathological changes in the sino-atria] node approaches imply that, contrary ~o previous theory, ~' a phys- ical basis for sino-atrial block may exist.

Undoubtedly in some instances of established sino-atrial disease the blood supply to the sino-atrial node remains intact and the degree of fibrosis is no more than can be expected from the normal ageing process. ~ ~-~ Here. some extra-cardiac factor such as excessive vagal tones -~ -~ or a cerebral lesion. ~ might be incriminated. However, such a mechanism seems unlikely, since far from atropine abolishing the dysrrhythmia in sino- atrial disorder, the response is usually subnormal. ~ ......... In one case, carcinomatous infiltration of the cardiac plexus was found at autopsy and it is possible that this might have increased the parasympathetic drive to the sinus node, although the author considered this unlikely. ''~ More likely alternatives would seem to be degeneration of the perinodaI

American Heart Journal 539

Annotations

ganglionated plexus, ~- or reduction of cholinesterase activity in atrial tissue, ~ either of which would be indiscernible on routine light microscopy.

Sino-atrial disorder is likely to be the end result of one of a number of pathological processes which interfere with sino- atrial node and atrial muscle function. From the very limited data available, it seems unlikely tha t coronary artery disease plays a major role in producing the chronic form of the disorder. Rather, conditions leading to atrophy or fibrosis should be sought.

David B. Shaw, M.D. Heart Block and Bradycardia Survey

Cardiac Department Royal Devon and Exeter Hospital

Wonford, Exeter EX2 5DW England

REFERENCES

1. Lown, B.: Electrical reversion of cardiac arrhythmias, Br. Heart J. 29'.469, 1967.

2. James, T. N.: The coronary circulation and conduction system in acute myocardial infarction, Progr. Cardio- vasc. Dis. 10:410, 1968.

3. Rokseth, R., and Hatle, L.: Sinus arrest in acute myocar- dial infarction, Br. Hear t J. 33:639, 1971.

4. Ferrer, I.: The sick sinus syndrome, Circulation 47:635, 1973.

5. Sutton, R., Norman, J., and Briers, L.: Sick sinus syndrome, Br. Med. J. 3:367, 1975.

6. Conde, C. A., Lepp0, J., Lipski, J., Stimmel, B., Litwak, R., Donoso, E., and Dack, S.: Effectiveness of pacemaker t reatment in the bradycardia-tachycardia syndrome, Am. J. Cardiol. 32:209, 1973.

7. Shaw, D. B., and Eraut, D.: Prevalence and morbidity of hear t block in Devon, Br. Med. J. 1 ;144, 1970.

8. Shaw, D. B., Kekwick, C. A., and Brownlee, W. C.: Sick sinus syndrome, Br. Meal. J. 3:767, 1975.

9. Rosen, K. M, Rahimtuola, S. H., Gunnar, R. M., and Lev, M.: Transient and persistent atrial standstill With His bundle lesions, Circulation 44:220, 1971.

10. Kaplan, B. M., Langendorf, R., Lev, M., and Pick, A.: Tachycardia-bradycardia syndrome (so-called Sick Sinus Syndrome), Am. J. Cardiol. 31:497, 1973.

11. Kulbertus, H. E., Leval-Rutten, F., and Demoulin, J. C.: Sinu-atrial disease: A report of 13 cases, J. Electrocar- diol. 6(4):303, 1973.

12. Warembourg, H., Th6try, C. I., Lekieffre, J., Delbecque, H., and Gosselin, B.: Blocs Sino-Auriculaires et blocs auriculo-ventriculaires associ6ts, Arch. Mal. Coeur. 67:787, 1974.

13. Brownlee, W. C., Evans, R. C., and Shaw, D. B.: Pathol~

ogy of conducting system in sino-atrial disease, Br. Heart J. 37:779, 1975,

14. Williams, D. O., Jones, E. L., Nagle, R. E., a n d Smith, B. S.: Familial atrial cardiomyopathy with heart block, Q. J. Med. 41:491, 1972.

15. Radford, D. J., and Izukawa, T.: Sick sinus syndrome, Arch. Dis. Child. 50:879, 1975.

16. Rokseth, R., Hatle, L., Gedde-Dahl, D., and Foss, P. O.: Pacemaker therapy in sino-atrial block complicated by paroxysmal tachycardia, Br. Heart J, 32:93, 1970.

17. Rasmussen, K.: Chronic sino-atrial heart block, AM. HEART J. 81:38, 1971.

18. Fairfax, A. J., and Leatham, A.: Idiopathic heart block: Associated with vitiiigo, thyroid disease, pernicious anaemia and diabetes mellitus, Br. Med. J~ 4:322, 1975.

19. Fowler, P. B. S., Ikram, H., Maini, R. N., Makey, A. R., and Kirkbam, J. S.: Bradycardia with angina: Haemody- namic aspects with treatment, Br. Med. J. 1:92, 1969.

20. Eraut, D, and Shaw, D. B.: Sinus bradycardia, Br. Heart J. 33:742, 1971.

21. Narula, 0. S.: Atrio-ventricular conduction defects in patients with sinus bradycardia, Circulation 44:1096, 1971.

22. Evans, R. C., Kekwick, C. A., and Shaw, D. B.: Overdrive suppression and other tests of sino-atrial function, Br. Heart J. 37:559, 1975:

23. Scherf, D.: The mechanism of sino-atrial block, Am. J. Cardiol. 23:769, 1969.

24. Lev, M. J.: Ageing changes in the human sinu-atrial node, J. Gerontol. 9:1, 1954.

25. Davies, M., and Pomerance, A.: Quantitative study of ageing changes in the human sino-atrial node and inter- nodal tracts, Br. Heart J. 34:150, 1972.

26. Laslett, E. E.: Syncopal at tacks associated with prolonged arrest of the whole heart , Q. J. Med. 2:247, 1909.

27. Webb, A. M., and Wilson, D. C.: Standstill of the heart of vagal origin, AM. HEART J. 5:493, 1930.

28. Kirk, J. E., and Kvorning, S. A.: Sinus bradycardia-A clinical study of 515 consecutive cases, Acta Med. Scand. (Suppl.) 266:625, 1952.

29. Easley, R. M., and Goldstein, S.: Sino-atrial syncope, Am. J. Med. 50:166, 1971.

30. Mandel, W. J., Hayakawa, H., Allen, H. N., Danzig, R., and Kermaier, A. I.: Assessment of sinus node function in patients with the sick sinus syndrome, Circulation 46:761, 1972.

31. Pearson, R. S. B.: Sinus bradycardia with cardiac asys- tole, Br. Heart J. 12:61, 1950.

32. Rossi, L.: Histopathologic features of cardiac arrhyth- rajas, Casa Editrice, Ambrosiana, Milano, 1969.

33. Dighton, D. H.: Sinus bradycardia: Autonomic influences and clinical assessment, Br. Heart J. 36:791, 1974.

Of the cardiac work-up

There is a practice in most hospital and medical insti tutions and office groups to do a "complete" work-up of patients. This modern work-up is looked upon with pride and with a sense of superiority. It is considered superior to the work-up of equally

competent, if not more competent, physicians who fortunately do not have access to expensive gadgetry and hazardous procedures. Today these "centers" routinely include, along with EPA and lateral roentgenographic views of the heart ,

5 4 0 October, 1976, Vol. 92, No. 4