Journal, Supraventricular tachycardia with AV block · Supraventricular tachycardia withAVblock NabilEl-Sherif Fromthe Cardiology Department, KasrEl-AiniFaculty ofMedicine, Cairo

British Heart Journal, 1970, 32, 46.

Supraventricular tachycardia with AV block

Nabil El-SherifFrom the Cardiology Department, Kasr El-Aini Faculty of Medicine,Cairo University, Egypt, U.A.R.

It is extremely difficult, even impossible - except in rare instances - to differentiate cases of par-oxysmal atrial tachycardia with block from AV junctional tachycardia with forward block butfree retrograde conduction to the atria. These cases are collectively termed supraventricular tachy-cardia with block. The arrhythmia is not uncormmon and an incidence of I in 360 electrocardio-grams was found in the last 6-year period.

Supraventricular tachycardia with block has a dynamic nature, and because it depends primarilyon the electrocardiogram for its recognition a critical review of the salient cardiographic features isgiven. However, not uncommonly it needs to be differentiated from a long list of other disorders ofthe heart beat. The relation of the arrhythmia to other atrial disorders is discussed, and the presenceof supraventricular tachycardia with latent block is mentioned.Of the present series, 82 per cent were found to be precipitated by means that deplete body potas-

siun in a digitalized patient suffering usually from an advanced cardiac disease. This group has aserious prognosis With 22 per cent mortality, but rapid intervention by discontinuing digitalis anddiuretic measures and the administration of potassium and other antiarrhythmic drugs are usuallyeffective. In I8 per cent of cases digitalis could not be blamed for the arrhythmia, and this grouphas a better prognosis, and digitalis may be beneficial in controlling the ventricular rate if heartfailure is present.

Though disorders of impulse formation andimpulse conduction are usually treated separ-ately in papers on the electrocardiogram theyoften show mutual dependence. Usually whena rhythm disturbance comprises both dis-orders the prognosis is less favourable. Thisis exemplified by cases of paroxysmal atrialtachycardia with AV block, long recognizedas a serious complication of digitalis over-dosage. Though the first description of a casewas that of Lewis (I909), few cases had beendescribed until 1943 when two large serieswere published by Barker et al. and Decherd,Herrmann, and Schwab. More recently,paroxysmal atrial tachycardia with block hasbecome more frequently described, and itsrelation to digitalis overdosage was clarifiedby the extensive work of Lown and Levine(I958). However, much emphasis on the sub-ject has obscured the fact that AV junctionaltachycardia with or without block is an evenmore frequent manifestation of digitalis over-dosage (Pick, Langendorf, and Katz, I96I;Soffer, I96I; Castellanos and Lemberg, I963).At least 5 different types of AV junctionaltachycardia with block have been described(Pick et al., I96I); one of these is a case of AV

Received I9 May 1969.

junctional tachycardia with forward conduc-tion disturbance in the presence of a normalretrograde conduction to the atria. This typeresembles cases of paroxysmal atrial tachy-cardia with block except perhaps for the direc-tion of atrial activation, as judged by the in-scription of inverted P waves in diaphrag-matic surface leads. However, recently wehave learned to depend less on the directionof the P wave as an indication of the site ofimpulse formation. Inverted P waves havebeen seen in experimentally induced low atrialextrasystoles and tachycardias (Prinzmetal etal., I952), while experimentally producedretrograde atrial activation may produce,against the rule, upright P waves in diaphrag-matic surface leads (Moore et al., I967).

In the presence of a single ectopic supraven-tricular systole it may be possible to differen-tiate atrial from AV junctional origin, depend-ing largely on the temporal relation betweenthe P and QRS. The situation becomes moredifficult in the presence of paroxysmal tachy-cardias initiated in the atria or AV junctionaltissue. These are usually considered togetherunder the term of paroxysmal supraventricu-lar tachycardia, since their clinical manifesta-tions and their response to exercise, carotid

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Supraventricular tachycardia with AV block 47

sinus compression, and drugs are usuallyidentical (Friedberg, I966). It is now becom-ing extremely difficult, even impossible - ex-cept in a few instances as will be seen later -to differentiate cases of atrial tachycardia withAV block from cases of AV junctional tachy-cardia with forward block and normal retro-grade conduction, simply because of loss ofthe fixed temporal relation between the P andQRS, while the direction of the P wave offerslittle help. The present work finds that suchdifferentiation is in fact unwarranted, since theaetiology, clinical picture, salient electrocar-diographic features, and management arepractically the same. These cases can be col-lectively termed supraventricular tachycardiawith complete atrial capture and forward AVblock or simply supraventricular tachycardiawith block. It should be emphasized here thatother types ofAV junctional tachycardia withblock showing complete or incomplete AVdissociation, where the atria are basically con-trolled by the sinus rhythm or atrial fibrilla-tion, are not included in the term, since thesecases present sufficiently characteristic elec-trocardiographic patterns of their own.

Material and methodsThe electrocardiograms at Kasr El-Aini, CairoUniversity Hospitals, in the 6-year period fromJanuary i962 to January i968 were reviewed, and

records showing supraventricular tachycardia withblock were studied. In a total of 23,500 electro-cardiograms 66 cases were found. Most of themwere studied and personally followed. In the fewinstances where personal contact was lacking,thorough review of the clinical and laboratorydata was obtained. During the study, emphasiswas placed on the type of heart disease presentand details of the therapeutic measures employed,especially the digitalis and diuretic regimen. Theonset and offset of the arrhythmia were recordedwhen possible. The course, duration, number ofattacks, and measures instituted in the treatmentwere all included in the study. The electrocardio-grams were analysed for atrial and ventricularrates, configuration of the atrial complexes, PPcycles, type ofAV block, cardiographic manifesta-tions of digitalis toxicity, and other associatedrhythm disturbances.

ResultsPertinent data in the 66 cases that fulfilled thediagnosis of supraventricular tachycardia withblock are summarized in Tables 1-3. The ages

FIG. I Supraventricular tachycardia withblock showing varying degree of AV block.Note that the multiple ectopic P waves inrecord B arise from the same ectopic centrethat later on discharges repeatedly. All recordswere obtained in one sitting.

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48 Nabil El-Sherif

of the patients ranged widely from i8 to 75years, with a mean of 38 years. More than halfof them were in an advanced stage of conges-tive failure. Digitalis was regarded as theaetiological factor in the development of thearrhythmia in 82 per cent, using the criteriaof Lown, Wyatt, and Levine (I960). Clinicalsigns of digitalis toxicity were usually lacking;however, electrocardiographic signs in theform of multifocal ventricular premature sys-toles, ST, and T changes were frequently re-corded. Usually, these patients were on amaintenance dose of digitalis, and the arrhyth-mia developed after measures leading to ex-cessive loss of body potassium, usually an in-tensive diuretic therapy.During the period of observation i2 pa-

tients died, and all were cases of digitalis-induced supraventricular tachycardia withblock. However, out of these only 4 patientshad died in spite of active measures for treat-ment of the arrhythmia.

Discussion

Electrocardiographic features

P Wave There is a definite, yet sometimesslight, change in the contour of the P wavefrom the basic sinus P wave. This is particu-larly seen in records showing either the onsetor offset of the arrhythmia (Fig. i and 2). TheP waves were upright though sometimesdiminutive in the diaphragmatic surface leadsin 76 per cent and inverted in 24 per cent ofthe cases (Fig. 3). Though the contour of theP wave is in no way a sure sign of the site oforigin of the ectopic discharge, it seems fromthis work that supraventricular tachycardiawith block arises much more frequently fromthe upper part of the atria near the sino-atrialnode than from the lower atrial region and theadjacent AV junctional tissue. As early as1943, Barker et al. reported negative P wavesin one-sixth of their cases of paroxysmalatrial tachycardia with block. Lown andLevine (1958) stated that the site of origin ofthe ectopic focus in paroxysmal atrial tachy-cardia with block was most commonly in theupper part of the atrium near the sino-atrialnode. This criterion of positive P wave indiaphragmatic surface leads was, however,rigidly followed in later descriptions of tachy-cardia with block (Goldberg et al., i960),probably actively excluding cases with nega-tive P waves on the basis of their presumedAV junctional origin. On the other hand, someauthors included all cases with negative Pwaves under the heterogeneous group of AVjunctional tachycardia with block (Pick et al.,

TABLE i Aetiological diagnosis in 66 casesof supraventricular tachycardia with block

Aetiology No. of patients

Digitalis-induced Arrhythmia unrelatecarrhythmia to digitalis

Men Women Men Women

Rheumatic heart disease 17 9 I 3Hypertension 4 2 I ICoronary heart disease 7 I 4Cor pulmonale 6 2Cardiomyopathy 2 2Atrial septal defect (post-operative) - IChronic renal failure 2 - -

Total 38 i6 7 5

(54) (I2)

TABLE 2 Electrocardiographic characteristicsin supraventricular tachycardia with block

Rate/mim. <100 101-120 121-150 151-200 201-250 > 250

Atrial I 3 8 29 20 5Ventricular 39 24 3 -

Type of AV block: 2: I 48Wenckebach 2Icomplete 3varying 34

Contour of P wave in diaphragmatic surface leads:positive (sometimes diminutive) 50negative i6

TABLE 3 Therapeutic considerations in supra-ventricular tachycardia with block

Therapeutic measure No. of No. ofcases successful

reversions

Digitalis-induced arrhythmiapotassium by mouth I0 8potassium intravenously i8 17procainamide 6 5antazohne 2 2phenytoin 2 2propranolol 4 4

Total 42 38

Arrhythmias unrelated to digitalisprocainamide 4 4propranolol 2 2digitalis 6 4

Total 12 10



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Supraventrictilar tachycardia with AV block 49

I96I; Castellanos and Lemberg, I963). Asalready mentioned, the contour of the P waveis not a sure sign of the site of origin of theectopic discharge. A positive P wave may arisefrom retrograde activation of the atria and anegative P wave may arise not in the AV junc-tional tissue but in the lower part of the atria.It is only in one condition that we becomereasonably sure that the negative P wave arisesfrom AV junctional tissue; this is seen in Fig.4 which shows an ectopic centre of dischargewith an intrinsic rate of 200 beats a minutethat sometimes shows 2: I exit block. Whenthe centre discharges freely at a rate of 200,there is a 2: I AV block, and we are faced witha supraventricular tachycardia with blockwhere it is impossible to tell whether the siteof origin is in the lower atrial or AV junctionalregions. However, when a 2:I exit blockdevelops we get an arrhythmia similar to whathas been termed 'non-paroxysmal nodaltachycardia' by Pick and Dominguez (I957).Here the AV junctional origin could be sug-gested depending on the temporal relation ofthe P following the QRS. In fact, exit block ofan AV junctional ectopic centre, as shownhere, is rare. We have found only 3 reportedcases of a similar condition, where exit blockwas shown in cases of paroxysmal atrial tachy-cardia (Calviino, Azan, and Castellanos, I957;Phibbs, I963; Dressler, Jonas, and Javier,1966). Cases of AV junctional arrhythmiadescribed as showing exit block (Pick et al.,I96I; Castellanos and Lemberg, I963; Pickand Langendorf, I968) are in fact wronglynamed. All these cases are associated withatrial fibrillation, and usually a completeblock exists between the fibrillating atria andthe AV junctional centre, while what is calledan exit block represents simply a form of for-ward block of a varying degree and does notdeserve the term of exit block as classicallyunderstood.

Atrial rate The rate of discharge of theectopic pacemaker in supraventricular tachy-cardia with block shows a wide range. Thehighest rate recorded in this series was 295beats a minute and the lowest rate in whichthe ectopic centre was still dominant was 72(Fig. 5). This is quite a slow rate for an ectopicatrial focus, and can only be explained byassuming a certain degree of depression of thesino-atrial node. Rates as high as 400 (Simon-son and Berman, I95I) and as low as io6(Lown et al., I960) have been reported. How-ever, in 86 per cent of the present series theatrial rate ranged between I20-250. It appearsthat there is a significant overlap betweensupraventricular tachycardia with block and4

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FIG. 2 The dynamic nature of the arrhyth-mia was fully shown during the routinerecording of the electrocardiogram by atechnician. The whole procedure usually took3-4 minutes during which several shortparoxysms of supraventricular tachycardiawith varying degree ofAV block were recorded,sometimes initiated by a premature atrialsystole (VI).

atrial flutter at the high rate levels, and be-tween it and sinus tachycardia or even normalsinus rhythm at the low rate levels; this makesit hazardous to depend solely on the atrialrate for their differentiation.

PP interval In one-third of our cases thePP cycles varied in their duration, the varia-tion ranging from o-oI to 0X22 of a second(Fig. 6 and 7B). Half of the cases of Lownet al. (I96o) showed variations of up to o0i2

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FIG. 3 Supraventricular tachycardia with block showing inverted P waves in diaphragmaticsurface leads. The blocked P waves are barely discernible; however, carotid sinus compression(CSC) gives rise to an increased degree of AV block and the atrial mechanism can easily be shown.

of a second. This phenomenon has variousexplanations: a commonly acceptable viewis the negative chronotropic effect of the ven-tricular systole (Rosenbaum and Lepeschkin,I955). Classical paroxysmal supraventriculartachycardia and atrial flutter, on the otherhand, are characterized by a regular PP cyclelength.

PP baseline An isoelectric baseline of o0o4sec. or more in every lead including the oeso-phageal leads is considered a sine qua non insupraventricular tachycardia with block, whileatrial flutter is characterized by an undulatingbaseline in one or more leads. Prinzmetal et al.(i95i) suggested that the undulating appear-ance of atrial flutter was due to the combina-tion of ectopic P waves and the oppositelydirected Ta waves. The more rapid the atrialrate, the larger the Ta wave. Rosner (I964)suggested that it was possible for paroxysmalatrial tachycardia with block associated withvery fast atrial rates to show continuous base-line activity as a result of atrial repolarizationbecoming electrically more prominent. Ken-namer and Prinzmetal (I954) have denied thatthe differentiation between paroxysmal atrial

tachycardia with block and atrial flutter canbe made by the presence of isoelectric inter-vals between P waves. On the other hand,Lown et al. (I960) think that rapid paroxys-mal atrial tachycardia with block and slowflutter usually retains the PP baseline charac-teristics. In our experience it is only the secondhalf of this view that holds true. While it ispractically always possible in the presence ofatrial rates below 200 to differentiate supra-ventricular tachycardia with block from atrialflutter, it is quite possible that above this rate- and especially above 250 beats a minute - thedecision concerning the presence or absenceof an isoelectric interval may be difficult tomake. There is always the subject of inter-individual and intraindividual variations ininterpretation (Prinzmetal et al., I952; Ep-stein et al., I96I; Caceres, I963).

AV response All types ofAV block from firstdegree to complete were recorded, and inmany cases there was a shift from one type toanother (Fig. i and 2). The predominant typeof AV heart block was, however, second de-gree AV block, frequently as sustained 2:1block with the sporadic Wenckebach's phe-

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FIG. 4 Supraventricular tachycardia with exit block and double supraventricular tachycardias.Record A shows the development ofAVjunctional tachycardia with inverted P waves in lead IIafter the QRS complexes simulating terminal S waves. Record B shows the release of a 2:I exitblock giving rise to a supraventricular tachycardia with AV block; this is continued in record C.Record D shows a short paroxysm of tachycardia from the same atrial focus giving prematureatrial systoles marked X above.

nomenon. Vagal stimulation and carotid sinuscompression usually increase the degree ofAV block but have no effect on the atrial rate(Fig. 3 and 8). In a few instances pseudo-bigeminy was shown (Fig. 8). This uncom-mon type of AV conduction was originallydescribed in atrial flutter (Basoain-Santander,Pick, and Langendorf, 1950) but was notpreviously reported in supraventricular tachy-cardia with block. It is explained by the pre-sence of two levels of block in the AV junc-tional tissue, a 2:I conduction ratio in theupper region of the AV junction, and a 3:2conduction ratio in the lower region.

Supraventricular tachycardia with blockand other atrial arrhythmiasThe relation between supraventricular tachy-cardia with block and atrial flutter has been

mentioned during the discussion of the PPbaseline characteristics. Four patients in thepresent series have shown an increase in therate of discharge of the ectopic supraventricu-lar focus, with loss of the isoelectric baselinecharacteristics, either shortly after successfultherapeutic reversion of supraventriculartachycardia with block (Fig. 7c) or in the wakeof increase of the digitalis dosage and inten-sive diuretic therapy (Fig. 5). Whether thesecases represent instances of rapid supra-ventricular tachycardia with block or atrialflutter is difficult to tell. Rosner (I964) calledthose cases, consisting primarily of rapid atrialactivity but without any special appearance ofthe baseline or atrial wave form, 'atrial tachy-systole with block', and this has been takento favour the view that there is a continuumbetween supraventricular tachycardia and



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52 Nail El-Sherif

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rate which is higher than that of the ectopic centre in the second half of the record. The ectopiccentre was still dominant at a rate of 72 a minute (record 6). Record C was obtained shortlybefore the death of the patient, who was again under digitalis; it shows an atrial rate of 250 aminute and no PP isoelectric intervals.

atrial flutter, with an intermediate zone that digitalis-induced atrial flutter is a raritydefies exact differentiation. The present work (Delman and Stein, 1964).cannot prove or disprove this view. However, The mechanism preceding the onset ofwe think that in these cases the establishment supraventricular tachycardia with block wasof the role played by digitalis in the patho- generally normal sinus rhythm. However, in 5genesis of the arrhythmia will have a greater cases the arrhythmia developed on top ofrepercussion on both prognosis and manage- established atrial fibrillation. Though Lownment than the still biased theoretical discus- et al. (1960)mentionedthatasinusmechanismsion. It is pertinent to mention here that was restored irrespective of the antecedent

FIG. 6 Supraventricular tachycardia with bloch showing variable PP cycle lengths.

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54 Nabil El-Sherif

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FIG. 9 Supraventricular tachycardia with block on top of chronic atrial fibrillation. Record

A shows the development of supraventricular tachycardia with block in a patient known to have

chronic atrial fibrillation. Withholding digitalis and the administration of propranolol resulted in

re-establishment of atrial fibrillation (record B). It is interesting to observe that propranolol failed

to abolish the ventricular parasystolic focus present but slowed down its intrinsic rhythm. FB

represents fusion beats.

rhythm, this was not our experience where re-

establishment of atrial fibrillation was noticed

after control of the arrhythmia (Fig. 9).

It is to be stressed here that when supraven-

tricular tachycardia with block develops on

top of atrial fibrillation, the atria stop fibrillat-

ing and begin to contract rhythmically in re-

sponse to the ectopic focus. This differs from

the admittedly more frequent manifestation

of digitalis toxidcity where enhancement of an

AV junctional pacemaker develops while an

area of block between the fibriltngara and

the-~ectopic centre is present.

The occurrence of 2 supraventricular pace-

makers competing for the atria was occasion-

ally observed as a transient phenomenon dur-

ing the evolution of the arrhythmia (Fig. 4).

Usually one of the pacemakers is ill sustained,

and this may explain why this phenomenon

of 2 supraventricular pacemakers both cap-

turing the atria was rarely recorded (Chungand Thomas, 1965). This differs from the

more frequent situation of double AV junc-

tional pacemakers, the upper one capturingthe atria while the lower one controls the ven-

tricles, producing a complete or incomplete

atrioventricular dissociation (Pick et al., i96i;Castellanos and Lemberg, i963).

Lastly, the presence of a supraventricular

tachycardia with latent AV block was rarely

mentioned. This arrhythmia is characterized

by an increase in atrial rate with an alteration

in P wave contour, and differs from supra-

ventricular tachycardia with overt block in

that the PP interval is normal and that AV

block is induced only by carotid sinus com-

pression (Bernstein and Stanzler, 1966)

and/or digitalization. This arrhythmia was

originally described by Lown and Levine

(i958) as a stage during the evolution and

recession ofparoxysmal atrial tachycardia with

block. However, this period as described by

Lown and Levine (i958) was brief, which

could be explained by the rapid nature of the

experiments undertaken (Bemnstein and Stanz-

ler, 1966). It is possible for this stage to be

prolonged if there is a gradual digitalis over-

dosage or potassiumn depletion. One of these

patients was noticed by Lown and Levine

(i958), and 2 more cases were later described

(Bernstein and Stanzler, 1966). One of our

cases helped to show classically this type of

arrhythmia (Fig. 5). This was a case of coron-

ary heart disease receiving combined digitalisand diuretic therapy for congestive failure,but the heart rate failed to slow down. An

electrocardiogram recorded one week after

admission showed an atrial rate Of Io5 a

minute and a change in the contour of the P

wave which was difficult to explain. A trial to

slow down the heart rate by carotid sinus

compression gave rise to AV block with little

B

24 6 -



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effect on the atrial rate. The significance ofthese changes was not grasped at that time,and more digitalis was given. However,clinical irregularity was observed in the pulseand an electrocardiogram I0 days later showedsupraventricular tachycardia with AV blockand an atrial rate of I90 a minute. The contourof the P waves was the same as that observedin the previous record which was now correct-ly interpreted as showing supraventriculartachycardia with latent block. When digitaliswas stopped and K infusion started the atrialrate regressed and sinus rhythm was estab-lished. It was interesting to observe that theectopic centre remained dominant at an atrialrate of 72/min.

Apparently these cases are relatively rare;however, recognition of their occasional rela-tion to a lesser degree of digitalis toxicity isimportant so that the more serious conse-quences of further digitalis administration orof potassium loss can be avoided.

DiagnosisAs a rule, the diagnosis of supraventriculartachycardia with block depends essentially onthe electrocardiogram, but even the tracingis sometimes missed or confused with otherarrhythmias. This is probably the result ofthe dynamic nature of the arrhythmia, andhence the varying phases that it may assumein its development or recession. The maindifficulty will arise from failure of recognitionof the atrial activity either because these arediminutive in the conventional leads takenor because of superimposition of some or allof atrial waves on the QRS-T complexes.This difficulty will be accentuated in thepresence of a varying degree of AV block.Sinus rhythm, sinus tachycardia, paroxysmalsupraventricular tachycardia, atrial flutter,atrial fibrillation, and ventricular tachycardiamay enter into the differential diagnosis atone time or another.Though the use of carotid sinus compres-

sion or right chest leads is sometimes highlyeffective in the diagnosis by clarifying theatrial mechanism, the best way of unravellingthe atrial activity is by the oesophagealelectrode (El Sherif, El-Ramli, and Sorour,I969), (Fig. 4).No essential electrocardiographic differ-

ences were found between cases of digitalis-induced supraventricular tachycardia withblock and those unrelated to digitalis. Thiscontrasts with previous claims (Oram, Resne-kov, and Davies, I96o).

PrognosisThe prognosis in digitalis-induced paroxys-mal atrial tachycardia with block was con-sidered serious. The reported mortality ratevaried from 28 per cent (Freiermuth and Jick,1958) tO 58 per cent (Nadas, Rudolph, andReinhold, I953). This is undoubtedly relatedto the underlying serious heart disease (Lownet al., I960). It seems unlikely that thearrhythmia itself is directly detrimental to thecardiac function and cardiac output (Gold-berg et al., I960). In the present series themortality in the digitalis-induced supraven-tricular tachycardia with block was relativelyhigh (22%). However, most of the cases diedeither because the arrhythmia was not sus-pected, and therefore no specific managementwas undertaken, or because it was misdiag-nosed, usually as atrial flutter, and digitaliswas continued. Therefore, out of 42 cases ofthe digitalis-induced arrhythmia receivingspecific treatment, only 4 died during theperiod of observation (9%). On the otherhand, the prognosis was excellent in the minorgroup unrelated to digitalis, with no singlefatality during the observation period.

TherapyWhen the arrhythmia is due to digitalis, with-holding the drug may suffice by itself, butfrequently a potassium-losing state is presentand potassium has to be given. There are ingeneral two main routes for severe potassiumdepletion, namely intestinal and renal, ofwhich the renal loss through the indiscrimin-ate use of diuretics is the most important.But even potassium loss through haemodia-lysis has sometimes been implicated (Lownet al., I953). Either the oral or intravenousroutes may be chosen. Usually the atrial rateshows gradual slowing before reversion tosinus rhythm and sometimes I: i conduction,with paradoxical increase of the ventricularrate (Fig. 5). If potassium is contraindicatedor ineffective, other antiarrhythmic drugs canbe used. Procainamide, antazoline, phenytoin,and propranilol have all been tried with suc-cess in the present series (Table 3). A casereport of the successful use of DC shock afterfailure of other measures was given by Cor-win, Klein, and Friedberg (I963).On the other hand, when the arrhythmia is

unrelated to digitalis the various antiarrhyth-mic drugs can be tried. More important is thefact that digitalis can be successfully used.The aim of digitalization is usually the con-trol of heart failure and/or the rapid ventricu-lar rate. Digitalis was given to 6 patients inthe present series, and in all of them it suc-



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56 Nabil El-Sherif

cessfully controlled the failure and slowed theventricular response. The arrhythmia wasseen to disappear after the control of failurein 4 of them while they were still under digi-talis. The beneficial role of digitalis inparoxysmal atrial tachycardia with block notinduced by digitalis was observed as early as1943 by Barker et al., and was later stressedby Morgan and Breneman (I962).

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Goldberg, L. M., Bristow, J. D., Parker, B. M., andRitzmann, L. W. (I960). Paroxysmal atrial tachy-cardia with atrioventricular block; its frequentassociation with chronic pulmonary disease. Circu-lation, 21, 499.

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mias, Digitalis and Potassium. Landsberger MedicalBooks, New York.

-, Wyatt, N. F., Crocker, A. T., Goodale, W. T., andLevine, S. A. (1953). Interrelationship of digitalisand potassium in auricular tachycardia with block.American Heart Journal, 45, 589.-,- , and Levine, H. D. (I960). Paroxysmal

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Nadas, A. S., Rudolph, A. M., and Reinhold, J. D. L.(I953). The use of digitalis in infants and children.A clinical study of patients in congestive heartfailure. New England Journal of Medicine, 248, 98.

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, and Langendorf, R. (I968). Recent advances inthe differential diagnosis ofA-V junctional arrhyth-mias. American Heart_Journal, 76, 553.

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Fields, J., Kennamer, R., Osborne, J. A., Smith,L. A., Sellers, A. L., Flieg, W., and Finston, E.(195i). Auricular flutter. American_Journal ofMedi-cine, II, 410.

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Journal, Supraventricular tachycardia with AV block · Supraventricular tachycardia withAVblock NabilEl-Sherif Fromthe Cardiology Department, KasrEl-AiniFaculty ofMedicine, Cairo