Canad. Med. Ass. J.Jan. 20, 1968, vol. 98 SHUJMAK AND BROWN: PORTABLE ELECTIROCAIRDIOGRAPHY 139

I'absence ou faiblesse de pouls humeraux et f6mo-raux. Ceci signe le diagnostic d'une interruption deI'arc aortique de type B avec art6re sous-claviereaberrante. La cyanose differentielle est plut6t raremais quand elle existe, elle est pathognomonique.L'electrocardiogramme et la radiographie du oceurne sont pas specifiques. Au point de vue hemodyna-mique, on note la contamination de I'aorte descend-ante par du sang arteriel venant de l'art6re sous-claviere o'u le flot est invers6. Ceci peut aussi etred6montre par cineangiocardiographie. Les malforma-tions le plus frequemment associ6es sont la com-munication inter-ventriculaire et la stenose aortique.Seul un diagnostic rapide, avec un minimum demanipulation du patient, immediatement suivi del'intervention,chirurgicale pourra permettre la surviede ces malades.

REFERENCES

1. STEIDELE, R. J.: Quoted by Roberts, W. L., Morrow A.G. and Braunwald, E.: Circulation, 26: 39, 1i62.

2. RORERTS, W. C., MoRRow, A. G. AND BRAuNwALD, E.:Ibid., 26: 39, 1962.

3. MOLLER, J. H. AND EDWARDS, J. E.: Amer. J. Roent-gen., 95: 557, 1965.

4. CELORIA, G. C. AND PATTON, R. B.: Amer. Heart J.,58: 407, 1959.

5. MEHRIZI, A. AND MORRISH, H. F.: Bull. Hopkins Hosp.,111: 127, 1962.

6. MAUCK, H. P., JR. et al.: Angiology, 14: 362, 1963.7. DAVES, M. L. AND TREGER, A.: Circulation, 29: 911,

1964.8. PILLSBURY, R. C., LOWER, R. R. AND SHUMWAY, N.

E.: Ibid., 30: 749, 1964.9. EVERTS-SUAREZ, E. A. AND CARSON, C. P.: Ann. Burg.,

150: 153, 1959.10. MERRIL, D. L., WEBSTER, C. A. AND SAMSON, P. C.:

J. Thorac. Surg., 33: 311, 1957.11. QuIE, P. G. et al.: J. Pediat., 54: 87, 1959.12. RuIZ VILLALOBOS, M. C. et al.: Amer. J. Cardiol., 8:

664, 1961.13. BLAKE, H. A., MANION, W. C. AND SPENCER, F. C.:

J. Thorac. Cardiov. Surp., 43: 607, 1962.14. REIDBORD, H. E.: J. LanceT, 84: 339, 1964.15. DORNEY, E. R., FOWLER, N. 0. AND MANNIX, E. P.:

Amer. J. Med., 18: 150, 1955.16. BOWERS, D. E., SCHIEBLER, G. L. AND KROVETZ, I. J.:

Amer. J. Cardiol., 16: 442, 1965.

Continuous Portable ElectrocardiographyK. H. SHUMAK, M.D. and

KENNETH W. G. BROWN, M.D., F.R.C.P.[C],* Toronto

A MAJOR limitation of conventional electro-cardiography is that it provides only a brief

sample of the patient's heartbeats. Importantabnormalities may be missed because they areintermittent and do not happen to occur whilethe patient's electrocardiogram is being recorded

In an attempt to increase the size of thesample, radioelectrocardiography was introducedin 1957 by Holter.1 In this system, the continu-ous electrocardiogram of the patient was trans-mitted to a radio receiver which produced arecord for examination. However, difficulties in-herent in the system limited its usefulness. Thepatient was forced to stay within the range ofthe receiver, and even then electrical inter-ference was a major problem. Accordingly,Holter2 in 1961 designed a new apparatus toovercome these disadvantages. The equipmentused in the present study is a commercial modifi-cation of Holter's 1961 apparatus. There arethree essential components to the system.

This study was supported by a grant from the OntarioHeart Foundation and was conducted in the Departmentof Medicine, University of Toronto and Toronto GeneralHospital.*Rykert Research Cardiologist, University of Toronto.Reprint requests to: Dr. K. W. G. Brown, CardiovascularUnit, Toronto General Hospital, Toronto, Ontario.

The electrocardiocorder* is a battery-operatedelectrocardiographic recorder which uses mag-netic tape instead of paper to record the electro-cardiogram continuously for 10 hours. This unitweighs four pounds and is portable by virtue ofa leather case not unlike that used for cameras.Two electrodes are used, one taped over thesternal end of the right second rib and the otherover the rib inferior to the cardiac apex. This bi-polar lead along the long axis of the heart re-sembles lead V5 of the standard electrocardio-gram.The electrocardioscanner consists basically of

two oscilloscope screens. On one screen, succes-sive PQRST complexes are rapidly super-imposed on one another. On the other, therhythm is presented in a picket-fence fashion,the height of each picket representing an R-Rinterval. By means of these two screens, anychange in the shape of the PQRST complex, orin the heart rate or rhythm, is easily detected.There is also a continuous audible signal pro-duced which changes with arrhythmias or withchanges in heart rate. The tape is played backat precisely 60 times the recording speed, so that

*Model 350 electrocardiocorder, Model 450 electrocardio-scanner and Model 550 electrocardiocharter, AvionicsResearch Corporation (T.M. reg.).

140 Shumak and Brown: Portable Electrocardiography Canad. Med. Ass. J.Jan. 20,1968, vol. 98

Fig. 1..Case 1. A burst of ventricular tachycardia during: the 10-hour electrocardiogramig o" " . *" . . * -. .....

normal.)tracing of a patient with intermittent tachycardia. (The conventional electrocardiogram was

nal.)

the entire 10-hour tape record can be reviewedon the display screens in 10 minutes.The third component, the electrocardiocharter,

is a modified electrocardiogram machine whichprints out any portion of the 10-hour tape onstandard electrocardiogram paper at the same

speed as a conventional electrocardiogrammachine. Abnormalities first located by playingthe tape on the electrocardioscanner are printedout on the electrocardiocharter for a permanentrecord and detailed analysis.At the beginning of the recording, the time is

noted, and the patient keeps a diary noting theexact time of any symptoms experienced duringthe 10-hour monitoring period. When the tape isstarted on one of the playback units, a clock onthe unit is set at the same time as the start of thediary. In this way, changes in the electrocardio¬gram can be correlated fairly precisely withreported symptoms.At times, interference in the recording can be

confusing and suggest abnormality. The inter¬ference arises as a result of extraneous potentialssuch as from muscle or from loose connections.This is a problem initially, but with experienceit becomes apparent that the patterns producedby such interference are characteristic, so thatone is able to recognize them as artefact withlittle difBculty.

Results

Forty-one patients were monitored on one or

more occasions for 10 hours with the Holterapparatus. Five of the patients are of specialinterest and will be presented in detail:

Case 1..Mr. C.K., 44 years of age, presentedwith a two-year history of occasional bouts of rapidpalpitation. Conventional electrocardiography failedto offer any clue as to the nature of these episodes.The first 10-hour tape showed occasional ventricularextrasystoles, but during the monitoring the patienthad no symptoms. A second recording was madeand during this the patient drank some whiskey,since this had frequently caused symptoms in thepast. During the second taping, the patient did havea brief symptomatic episode. In Fig. 1, the tracingat the time of this man's symptoms reveals a briefbout of ventricular tachycardia. The patient was

placed on procainamide hydrochloride and has sub¬sequently been symptom-free.

Case 2..Mrs. V.P., a 50-year-old woman withknown mitral stenosis, was admitted in heart failure.She gave a history of recent onset of brief episodesof rapid palpitation. At the time of admission, shewas in atrial fibrillation with a digitalis-controlledventricular rate of approximately 95 per minute(Fig. 2a). During continuous portable electrocardi-

Fig. 2..Case 2. Mitral stenosis. (a) Atrial fibrillation controlled with digitalis (5 p.m.).(b) Palpitation coincided with bursts of nodal tachycardia (6.08 p.m.).

Canad. Med. Ass. J.Jan. 20, 1968, vol. 98 Shumak and Brown: Portable Electrocardiography 141

Fig. 3..Case 3. (a) Stable normal sinus rhythm when asymptomatic. (b) Frequentventricular ectopic beats occurring singly and in salvos of three during spells of tinnitus andvertigo.

ography, she reported two episodes of palpitationwhich correspond to a rapid (nodal) tachycardiaof 175 per minute (Fig. 2b). The patient was sub¬sequently found to be hyperthyroid and treated,with relief of the palpitation.

Case 3..Mr. S.L., 47 years old, presented witha six-month history of recurrent bouts of tinnitusand vertigo and an eight-year history of occasionalpalpitation. During the admission physical examina¬tion, he had an abrupt onset of these symptoms andhis cardiac rhythm suddenly became highly irregu-lar. By the time a conventional electrocardiogramwas obtained, the irregularity had disappeared. Dur¬ing dynamic electrocardiography, he recorded 27attacks of tinnitus and vertigo, lasting from fiveseconds up to five minutes. Fig. 3 shows his rhythmwithout and with symptoms. Of the 27 symptomaticbouts, 26 showed coincident arrhythmias of this sort.

During the 10 hours, he had only one burst of thistype of arrhythmia without symptoms. All thisstrongly suggested a relationship between his cardi¬ac arrhythmia and his tinnitus and vertigo. Unfor¬tunately, attempts to treat his arrhythmia were un-

successful, so that we do not know if its abolitionwould affect the tinnitus and vertigo.

Case 4..Mrs. E.B. This 48-year-old woman hadthe syndrome of sinus bradycardia, paroxysmal atrialfibrillation and syncope due to intermittent asystole.She did not respond to any of numerous medicationstried and eventually she was treated with implanta¬tion of a ventricular demand pacemaker. The pace-maker unit was set to stimulate the heart if theventricular rate fell below 60 per minute. Beforedischarge from hospital, she was monitored for 10hours to ensure that the pacemaker was functioningas intended. Fig. 4 is a representative tracing illus-

Fig. 4..Case 4. Paroxysmal atrial fibrillation and syncope due to periods of asystole,treated with implantation of a ventricular demand pacemaker. When asystole occurs, theartificial pacemaker discharges automatically after 1 second and stimulates the heart at 60per minute until spontaneous ventricular activity resumes.

142 Shumak and Brown: Portable Electrocardiography Canad. Med. Ass. J.Jan. 20, 1968, vol. 98

Fig. 5..Case 5. (Top) 11.20 a.m. no discomfort. (Bottom) S-T depressions in the electro¬cardiogram coinciding with postprandial chest pain and interpreted as in support of thediagnosis of angina pectoris (12.35 p.m. pain after lunch).

trating that after precisely one second with no

spontaneous ventricular beat, the pacemaker beganto discharge, and it was concluded that the pace¬maker function was intact.

Case 5..Mr. L.E., a 39-year-old man with knownangina pectoris, was admitted with a history of re¬

cent onset of a different type of chest pain aftermeals, for which he had been ingesting scores ofnitroglycerin. An upper gastrointestinal radiographrevealed a moderately large hiatus hernia. He was

monitored in an effort to determine if his pain was

anginal in origin or not. Fig. 5 is a tracing duringa bout of pain after his dinner. He had similar painand a similar change in his electrocardiogram afterhis lunch. In each instance, the period of chest painnoted in his diary coincided with S-T segment de¬pressions in the electrocardiogram. On this basis,it was concluded that his pain was truly anginal inorigin. He died of coronary heart disease fourmonths later.As previously mentioned, 41 patients had one

or more continuous 10-hour recordings made. Inall, 53 recordings were obtained.Of the patients monitored, four were "normal

controls" and in each of these no abnormalitieswere detected. A larger series of normal subjectsunder a variety of environmental conditionsis currently being studied at the Toronto GeneralHospital. Of the remaining 37 subjects, 21 were

monitored because of palpitation, eight becauseof syncope or blackouts, four because of atypicalchest pain, and four because of the possibilityof pacemaker malfunction.The yield of positive findings was surprisingly

high. Nineteen of the 21 patients with palpita¬tion demonstrated one or more types of ar¬

rhythmia during the 10-hour recording. Thirteenshowed ventricular premature beats, four withtursts of ventricular tachycardia. Intermittentatrial fibrillation was recorded in four, one pa¬tient had intermittent nodal tachycardia and one

Tiad bursts of atrial flutter. Although cardiacirregularities were recorded in 19 of this group,

they produced symptoms in only 12. In each ofthese 12 patients there was close temporal rela¬tionship between the arrhythmia and the symp¬tom of palpitation.Of the eight patients with intermittent cerebral

episodes, an arrhythmia was found in four. Onlyone of these patients^ however, had symptomsduring the period of monitoring and he has beenpresented (Case 3). One additional patientdemonstrated a recurrent arrhythmia (bursts ofatrial fibrillation), but was asymptomatic duringthe monitoring. The arrhythmia was treated andthe patient has had no recurrence of symptoms.Of the four patients monitored to assess pace¬

maker function, one was found to have pace¬maker failure, one showed frequent competitionand two showed normally functioning pace¬makers.Of the four patients with questionable angina,

two showed characteristic ischemic S-T depres-sion at the time of the chest pain. Two showedno changes at the time of their pain.A summary of our results is presented in

Table I.

TABLE I..Results Obtained in Patients Monitoredfor 10 Hours by Holter Continuous

ElectrocardiographyNo. showing

No. of definiteReason for monitoring patients abnormalities

Palpitation. 21 19Intermittent cerebral episodes.... 82Assessment of pacemaker function 42Atypical chest pain. 4 2Normals. 4 0

Total. 41 25

DlSCUSSION

Although the Holter apparatus was developedin 1961, there are relatively few reports in theliterature concerning its use. In 1964, Gilson,Holter and Glasscock3 reported their analysis of.

Canad. Med. Ass. J.Jan. 20, 1968, vol. 98 Shumak and Brown: Portable Electrocardiography 143

230 recordings of five or more hours' duration,and described the normal basic patterns andnormal variations observed. In addition, theypointed out the typical artefact patterns and themanner in which the various arrhythmias appearon the screen. Later that year, Norland andSemler4 demonstrated the potential clinical use-

fulness of this technique in the diagnosis ofangina and detection of arrhythmias. Corday etal.5 also found this apparatus useful, particularlyin the assessment of angina and of transientneurological symptoms.As might be anticipated with new, delicate

equipment, technical problems have been en¬

countered. These cannot be attributed to lackof familiarity, for they have not disappeared withcontinued use. Periodic mechanical and electricalfailures in the recording units have been a

source of frustration and inconvenience. Themotor in these units apparently has a life ex-

pectancy of approximately only 150 hours. If a

patient from out of town is being monitored, wenow insist that he remain over until the tapehas been reviewed, to be certain that a satis-factory full 10-hour tracing has been recorded.When the tape is transferred from the

scanning unit to the printout unit, slight dis-crepancies in synchronization of the clocks can

result in considerable loss of time locating thedesired segment of the tape. Tapes containingseveral areas of interest often require two or

three hours for careful evaluation. This difficultycan be partially overcome by having a suitablytrained technician screen the tape and prepareappropriate areas for subsequent interpretation.A more recent model incorporating the two play-back units into one unit is apparently available,but the authors have had no experience with it.

In spite of careful technique, unexplainedartefacts occasionally appear. For example, over

the course of a few seconds the height of theR wave gradually declines until it is imper-ceptible for a few cycles and then graduallyreturns to normal. It is important that theseartefacts be recognized as such and not be mis-interpreted and form the basis for major thera¬peutic procedures. The initial expense of theequipment and cost of maintenance cannot bedisregarded.

Notwithstanding these disadvantages, theHolter apparatus answers a specific need in thestudy of a select group of cardiac patients. Inthe investigation of recurring palpitation or syn¬cope, patients were frequently admitted to thecoronary unit to monitor the heart rhythm fordiagnostic purposes. These patients are now

monitored as outpatients without occupying a

badly needed bed in the unit. Moreover, since

many of these patients have symptoms onlywhen active in their everyday environment,portable electrocardiography is often more in-formative than monitoring at bed rest.

Currently, we believe there are five applica-tions for portable electrocardiography:

1. To investigate the cause of palpitation.2. To determine if a cardiac arrhythmia is the

basis of intermittent cerebral episodes.3. To clarify the etiology of atypical chest

pain, or to assess a certain pattern of chest painin a patient known to have coronary heart dis¬ease along with one or more other conditionswhich can produce chest discomfort.

4. To determine if a previously implantedartificial pacemaker is functioning as it should.

5. To advance knowledge concerning thechanges in heart rhythm which can occur innormal individuals under a variety of environ-mental conditions. Similar studies should be alsoundertaken in patients with known heart disease.Although the present series is based on a rela-

tively small number of patients, the proportionin whom this technique contributed to the diag¬nosis and management was sufficiently high toendorse the availability of the apparatus in eachmajor medical centre. The technical difficultiesencountered make us hesitant to recommend itsuse for routine office practice.

« A continuous 10-hour electrocardio-bummary gram was recorde(i Qn 41 ambulant

patients using a commercial adaptation of the Holtertechnique. A camera-sized electrocardiogram taperecorder is worn by the subject for 10 hours. Theentire tape is scanned in 10 minutes on the oscillo-scope screen of a second unit. A third componentprovides a write-out of selected segments on stand¬ard electrocardiogram paper.The equipment is of value in the diagnosis of:

(1) intermittent cerebral attacks secondary tocardiac arrhythmias, (2) the type of cardiac arrhyth¬mia during brief episodes of palpitation, (3) atypi¬cal angina pectoris, and (4) malfunction of im¬planted cardiac pacemakers. This method also hasgreat potential in clinical heart research.

This equipment is expensive and facilities shouldbe available to overcome frequent technical prob¬lems. Detailed analysis of tapes with many arrhyth¬mias and correlation of abnormalities with symp¬toms is time-consuming. For these reasons, the auth¬ors conclude that the method is not practical forroutine practice. However, it is a useful tool in a

small select group of patients and should be avail¬able in each large medical centre.

. , , Les auteurs ont procede a Tenregistre-ment d'un electrocardiogramme con-

tinu d'une dur6e de 10 heures sur 41 maladesambulatoires. L'appareil etait une adaptation com-

144 GUTILERREZ AND OTHERS: PREMATURE BEATS AND SUDDEN DEATH Canad. Med. Ass. J.Jan. 20, 1968, vol. 98

merciale de la methode de Holter. Le sujet portesur lui, pendant toute la duree de l'experience, unenregistreur electrocardiographique sur ruban de lagrandeur d'un appareil photographique. On se sertensuite d'un deuxieme appareil avec ecran oscillo-scopique pour dechifrer le totalite du ruban en 10minutes. Un troisieme appareil permet d'obtenir untrace de certaines parties sur papier electrocardio-graphique normal.

Cet appareillage est precieux pour diagnostiquer(1) des attaques cerebrales intermittentes seondairesa des arythmies cardiaques, (2) la forme d'arythmiecardiaque durant les brefs episodes de palpitations,(3) des formes atypiques d'angine de poitrine et(4) pour deceler un vice de fonctionnement depacemakers cardiaques implantes. Cette methodeoffre egalement de vastes possibilites en recherchescardiologiques cliniques.

Cet appareil cou'te cher et devrait comporter desmoyens de surmonter des problemes techniques qui

surviennent souvent. L'analyse detaille- des rubansenregistres sur des sujets souffrant de plusieurs aryth-mies et la correlation des anomalies avec les symp-tomes exige beaucoup de temps. Pour ces raisons,les auteurs estiment que la methode n'est guere utiledans la pratique courante, bien qu'elle le soit chezun groupe restreint de malades choisis. Ils conside-rent que les grands centres medicaux devraientposseder au moins un de ces appareils.

The authors wish to thank the numerous physiciansat the Toronto General Hospital who permitted theirpatients to be monitored and Mrs. G. Fielding Biggarfor generous financial help in obtaining this equipment.

REFERENCES

1., HOLTER. N. J.: Ann. N.Y. Acad. Sci., 65: 913, 1957.2. Idemn: Science, 134: 1214, 1961.3. GILSON, J. S., HOLTER, N. J. AND GLASSCOCK, W. R.:

Amer. J. Cardiol., 14: 204, 1964.4. NORLAND, C. C. AND SEMLER, H. J.: J. A. M. A., 190:

115, 1964.5. CORDAY, E. et al.: Ibid., 193: 417, 1965.

Significance of T Wave Interruption by Premature Beatsas a Cause of Sudden Death

MIGUEL R. GUTIERREZ, M.D.,* GEORGE H. CHANGFOOT, M.B., B.S.tand DWIGHT I. PERETZ, M.D., M.Sc., F.R.C.P.[C], F.A.C.P., F.A.C.C.4

Vancouver, B.C.

P REMATURE beats occurring in patients withacute myocardial infarction and ischemic

heart disease should forewarn the physicianof possible impending disaster. Although thepresent study was carried out in a coronarycare unit with sophisticated instrumentation, theexperience gained is applicable in small com-munity hospitals as long as an electrocardio-graph is available for determining the phe-nomenon.The relationship between sudden death in

patients with serious myocardial disease andthe interruption of the electrocardiographic Twave by the QRS complex of a prematuresystole was first recognized in 1960 by Smirkand Palmer.' Numerous experimental studies inanimals have been reported, alluding to thecausal relationship between T wave interruption

From the Coronary Care Unit, Department of Medicine,St. Paul's Hospital, Vancouver, British Columbia.*Resident in Medicine, St. Paul's Hospital, Vancouver,British Columbia.tFellow in Cardiology, Department of Medicine, St. Paul'sHospital.tDirector, Medical Intensive Care and Coronary Care Unit,St. Paul's Hospital; Clinical Instructor, Faculty of Medi-cine, University of British Columbia.Reprint requests to: Dr. D. I. Peretz, 1081 Burrard Street,Vancouver 1, British Columbia.

by an extrasystole produced electrically,2-4 che-mically5 or following ligation of the circum-flex coronary artery,6 and the electrogenesis ofventricular tachycardia-fibrillation. Smirk andPalmer coined the term "R on T phenomenon"to describe the electrocardiographic event; thatis, the interruption of the antecedent T waveby the R wave (QRS complex) of a prematurebeat. The occurrence of ventricular tachyarrhy-thmias consequential or related to the R on Tphenomenon in a significant number of patientswith ischemic heart disease was electrographic-ally demonstrated by Ahuja, Gutierrez andManning.7

It is appreciated by many workers in thisfield", 7 8 and it is recognized generally by prac-tising physicians that the appearance of frequentmultifocal premature beats associated with acutemyocardial infarction is an ominous sign. Espe-cially when T wave interruption is seen, it repre-sents a warning of the possible initiation of a-nimpending life-threatening arrhythmia.The following is the classification of T wave

interruption (R on T phenomenon) describedby Smirk and Palmer' (Fig. 1):