British Heart Journal, I970, 32, 458-46I.

Sinus bradycardia treated by long-term atrialpacing

Malcolm Clarke, David W. Evans, and B. B. MilsteinFrom the Regional Cardiac Unit, Papworth Hospital, Cambridge

A technique for long-term atrial pacing is described. It uses the system whereby power from an

external pulse-generator (including battery) is transferred through the intact skin by inductive-coupling. Once installed, there is no requirementforfurther surgery to effect battery changes, andthe patient can control his heart rate over a wide range to suit his needs.

It is suggested that pacing by such means may offer a preferable alternative to drug therapyin the treatment of low cardiac output due to pathological sinus bradycardia. Two patients suc-

cessfully treated in this way are reported.

Sinus bradycardia may be a more commoncause of disability than hitherto recognized(Shaw and Eraut, I970). When pathologicalit is incapacitating because of the limitationit imposes on the cardiac output response toexercise and other stimuli; in very severe casesthere may also be a liability to Adams-Stokesattacks. Where indicated, treatment has usu-ally been by sympathomimetic or parasym-patholytic drugs (Bellet, I963; Friedberg,i966), but artificial pacemaking has occasion-ally been required (Shaw and Eraut, 1970).In these cases the pacing stimuli have beenapplied to the right ventricle, with consequentloss of the atrial transport function and poten-tial risk of pacemaker-induced ventriculartachydysrhythmia. We here describe an atrialpacing system which is free of these disadvan-tages and of the great drawback of most 'per-manent' pacing systems in current use, name-ly the requirement for periodic operations toreplace the unit. Our early experience suggeststhat long-term atrial pacing by this techniquemay be preferable to drug therapy where thelatter produces unpleasant side-effects.

Equipment and techniqueThe Lucas inductive-coupling system (Abrams,Hudson, and Lightwood, I960; Taylor, I966;Clarke, Evans, and Milstein, I970) has beenmodified by the makers to provide braided stain-less steel ring terminals to the output leads of thesecondary coil (Fig. i). The atrium is approachedby a small anterior transverse incision and thethird right costal cartilage is resected. The pleurais reflected laterally without opening it, and thepericardium over the right atrial appendage ex-Received 24 December I969.

posed. A 4 cm. vertical incision is made in thepericardium. The terminals are sutured to theepicardial surface of the right atrium about 2 cm.in front of the sino-atrial node, and a similar dis-tance apart. Additional anchorage and haemo-stasis are provided by a covering patch of Teflonfelt. The pericardium is loosely closed about theleads with 3 or 4 sutures, and the silicone-rubbercovered secondary coil left in a subcutaneouspocket at the usual site (Fig. 2). The wound isclosed after ascertaining that an adequate pacingstimulus can be induced with the primary coil4 cm. or more vertically above the secondary.The external components of the system are

standard, the pulse-generator being powered bythe universally-obtainable U2 cell. Rate controlis in the hands of the patient and a choice of powersettings is available. At normal power setting andaverage rates, the battery life is usually 3 to 4weeks and changes are quickly, easily, and safelyeffected by substituting the spare generator withattached primary coil. It is necessary to tape thiscoil to the skin in the desired position relative tothe secondary coil; this is aesthetically unsatis-factory but in practice no great disadvantage.

Case reportsCase I A 62-year-old man was admitted to thisunit in February I969. He had been dyspnoeicon moderate exertion for 5 years. Sinus brady-cardia had been diagnosed and treated with long-acting isoprenaline. This produced no sustainedimprovement and he had to give up his work as apostman. Latterly he had been dyspnoeic on walk-ing a few yards on the flat. He had been orthop-noeic and liable to attacks of paroxysmal nocturnaldyspnoea in spite of the use of five pillows andtreatment with diuretics.He also suffered from Meniere's syndrome but

gave no history of syncopal attacks.Physical examination confirmed orthopnoea

Sinus bradycardia treated by long-term atrial pacing 459

6 5 4 3 2 C-M t 2 3* -4 1 <.. ................_.,, ... ... .. ,_......

F I G. I Secondary coil and terminals.

FIG. 2 X-ray of chest showing internal com-ponents in position.

with minimal ankle oedema but no gross cardio-megaly or auscultatory abnormality. Right bra-chial blood pressure was 2I0/85 mm. Hg andheart rate 35-40 a minute; this rate was not in-creased by exercise. Chest x-ray showed somecardiac enlargement with unfolding of the aorta.The lung fields were clear. The electrocardiogram(Fig. 3) confirmed sinus bradycardia and revealedoccasional nodal escape; it was otherwise normal.No other evidence of intrinsic cardiac disease wasfound.

Intravenous atropine (0-6-12 mg.) resulted inheart rates up to 6o a minute but oral para-sympatholytics produced only unpleasant generaleffects without useful cardiac acceleration. Tem-porary transvenous right ventricular pacing wasinstituted as a therapeutic test. At pace-made ratesof 70-80 a minute he lost his orthopnoea and wasable to walk indefinitely on the flat and climb 2flights of stairs without distress.The temporary system was removed and a per-

manent inductive-coupling atrial system inserted,as described above. Atrial fibrillation ensued onthe first post-operative day and persisted, withrapid ventricular response, until spontaneous re-version to sinus rhythm on the sixth day. Duringthis time, when the pacemaker was turned off anddigitalization started, he felt particularly well.Resumption of slow sinus rhythm was accom-panied by deterioration of mood and return of hisdyspnoea. Atrial pacing at 70-80 a minute wastherefore reinstituted and he again became verybright and cheerful and free of dyspnoea. He hasremained well and active since discharge fromhospital io months ago. His right brachial bloodpressure is now about I40/70 mm. Hg. The pulse-

FIG. 3 Upper tracing: pre-operative electro-cardiogram of Case I. Lower tracing: post-operative electrocardiogram of Case i. Thepacing signals (one of which is arrowed) havebeen emphasized during reproduction.,~~~~~~~~~~~~~~~~~~~~~~~~~~~

i~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~....Issecond

1 - rid

460 Clarke, Evans, and Milstein

generator has been used in the 'high-power' modein this case since the late post-operative period.Case 2 A 53-year-old woman was admitted tothe unit in April I969. Her symptoms of dyspnoeaand dizziness on slight exertion, effort angina, andundue fatiguability extended over a period of 9years. They had forced her to retire from hernursing post.

Clinical examination revealed no abnormalityapart from a fixed heart rate of 40 a minute, withoccasional irregularity, and right brachial bloodpressure of I30/85 mm. Hg. The chest x-ray wasnormal.The electrocardiogram showed sinus bradycar-

dia occasionally interrupted by ventricular extra-systoles. Other investigations yielded no relevantfindings.

Test infusions of isoprenaline and atropine bothproduced a satisfactory increase in heart rate, butshe found the side-effects of the oral preparationsintolerable. A permanent atrial pacing system wasinstalled and was functioning normally (on 'low-power' setting and usually about 7o a minute) atfollow-up 7 months later. She had experienced noeffort dyspnoea or dizziness and no angina sincethe operation; she volunteered the informationthat she could not remember ever having felt soalert before.

Pace-made electrocardiogramFig. 3 shows the sequence of atrial stimulationby the pacemaker and ventricular activationafter an appropriate PR interval in each case.As noted by Lister et al. (I965), this intervalvaries directly with heart rate (Fig. 4) and notinversely as in the physiological state or whenheart rate is increased by atropine or isoprena-line. In Case I the PR interval increased fromOI4 sec. at a frequency of 40 a minute to 024sec. at Ioo a minute. In Case 2 the intervalwas o-i8 sec. at 6o a minute and 0-24 sec. atI35 a minute. Both patients have physio-logical PR intervals at their usual pace-maderates of 70-80 a minute, and at these rates thenodal and ventricular ectopic activity seenduring bradycardia is not in evidence. Theyhave not been tested for development of AVdissociation at very fast atrial rates.

DiscussionThe sinus bradycardia shown by these twopatients bore no relation to that of the trainedathlete and none of the well-known patho-logical states associated with such bradycardiawas found. Nor was there evidence of specificcardiac disease, though the second patienthad angina pectoris when her pulse rate wasslow. Selective coronary arteriography wasnot carried out.

These cases might be considered examplesof the 'lazy sinus syndrome' (Shaw andEraut, I970), a disease state that may prove

PACINGSTIMULUS

I SEC.~~~~~~PACING

STIMULUS

FIG. 4 Pace-made electrocardiogram (Case 2)showing variation ofPR interval with heartrate. Upper tracing: pacemaker rate 135 aminute, PR = o024 sec. Lower tracing: pace-maker rate 6o a minute, PR = o-i8 sec.

to be not rare. Drug treatment of this con-dition is frequently unsatisfactory because ofinadequate rate response or because of intoler-able side-effects inseparable from the drug'saction. Chief of these are mouth dryness andaccommodation disturbance in the case ofatropine and like preparations, and tremulous-ness and a most unpleasant feeling of tensionwith isoprenaline.Long-term atrial pacing provides a practic-

able alternative. The technique described in-volves a very minor thoracotomy but has theadvantages of external rate control, preserva-tion of atrial transport function (Johansson etal., I963; Sowton, I965), and avoidance ofany risk of pacemaker-induced ventriculartachydysrhythmia (Siddons and Sowton,I967). The risk of atrial dysrhythmia due tocompetitive sinus rhythm (Sowton, I965)must be small where the rate of the naturalpacemaker is so slow. Above all, the fact thatthe pulse-generator is external and easilyinterchangeable guarantees safety, and thereis no requirement for biennial or more fre-quent operations to change batteries as theyfail.Thoracotomy could be avoided by use of a

transvenous system, but pacing by this means

Sinus bradycardia treated by long-term atrial atrial pacing 461

has proved unreliable because of instabilityof the electrode tip (Kastor et al. I969).Stable transvenous atrial pacing has been ac-complished by placement of the electrode inthe proximal portion of the coronary sinus,but this method is not recommended forroutine use because of the potential hazardsof perforation and thrombus formation (Moss,Rivers, and Cooper, i969). It is concludedthat, at present, the most reliable way to es-tablish long-term atrial pacing is to suturethe electrodes to the atrium.

We wish to thank Dr. J. H. N. Bett of Melbourne,Australia, for his part in suggesting this methodof treatmnent. We are grateful also to the staff atJoseph Lucas' Research Laboratory for theirinterest and prompt assistance, to Dr. H. A.Fleming for permission to report Case 2, and tothe Photographic Department at Addenbrooke'sHospital, Cambridge, for reproductions of thefigures.

ReferencesAbrams, L. D., Hudson, W. A., and Lightwood, R.

(I960). A surgical approach to the management ofheart-block using an inductive coupled artificialcardiac pacemaker. Lancet, I, I372.

Bellet, S. (I963). Clinical Disorders of the Heart Beat,2nd ed., p. iI8. Henry Kimpton, London.

Clarke, M., Evans, D. W., and Milstein, B. B. (1970).Long-term pacing with an inductively coupledsystem. In preparation.

Friedberg, C. K. (i966). Diseases of the Heart, 3rd ed.,p. 486. W. B. Saunders, Philadelphia and London.

Johansson, B. W., Karnell, J., Malm, A., Sievers, J.,and Swedberg, J. (1963). Electrocardiographicstudies on patients with an artificial pacemaker.British Heart Journal, 25, 5I4.

Kastor, J. A., DeSanctis, R. W., Leinbach, R. C.,Harthome, J. W., and Wolfson, I. N. (I969).Long-term pervenous atrial pacing. Circulation,40, 535.

Lister, J. W., Stein, E., Kosowsky, B. D., Lau, S. H.,and Damato, A. N. (I965). Atrioventricular con-duction in man. Effect of rate, exercise, isopro-terenol and atropine on the P-R interval. AmericanJournal of Cardiology, I6, 5i6.

Moss, A. J., Rivers, R. J., and Cooper, M. (I969).Long-term pervenous atrial pacing from theproximal portion of the coronary vein. Journal ofthe American Medical Association, 209, 543.

Shaw, D. B., and Eraut, D. C. (I970). Sinus brady-cardia, sino-atrial block, and lazy sinus syndrome.In Proceedings of the British Cardiac Society.British Heart Journal, 32, 557.

Siddons, H., and Sowton, E. (I967). Cardiac Pace-makers, p. I13. Charles C. Thomas, Springfield,Illinois.

Sowton, E. (I965). Artificial pacemaking and sinusrhythm. British Heart Journal, 27, 311.

Taylor, A. B. (I966). Experience with cardiac pace-making. British Medical Journal, 2, 543.