Br Heart J: first published as 10.1136/hrt.38.12.1363 on 1 December 1976. Downloaded from

British Heart Journal, 1976, 38, 1363-1366. Pseudo second degree atrioventricular block with Successful treatment with quinidine

Raja W. Dhurandhar, F. J. Valen, and John Phillips From the Departments of of Touro Infirmary, Veterans Administration Hospital, and Tulane University School of Medicine, New Orleans, Louisiana, U.S.A.

Pseudo second degree atrioventricular block resulting from blocked His premature beats was successfully treated with quinidine. The diagnosis was proved by His bundle electrogram which showed both blocked and conducted His premature beats. The blocked His prematures produced second degree atrioventricular block by making the atrioventricular junction refractory. Quinidine abolished both conducted and blocked His extrasystoles. There has been no recurrence of during a one-year follow-up.

Langendorf and that there were no murmurs. The remainder of Mehlman (1947) suggested the copyright. non-conducted junctional premature beats might physical examination was normal. The electro- produce second degree atrioventricular block by cardiogram showed supraventricular premature blocking the sinus impulse following the premature beats with aberration and episodes of apparent beat. They suggested that the block was caused by Mobitz type II block (Fig. la). Apart from the junctional extrasystoles which were concealed arrhythmia, the electrocardiogram was normal. because of both anterograde and retrograde block. The patient was admitted for further evaluation and Rosen, Rahimtoola, and Gunnar (1970) showed, treatment of the arrhythmia. Initially he was given with His Bundle recordings, second degree atrio- tincture of belladonna, 1 ml, four times a day. The http://heart.bmj.com/ ventricular block resulting from blocked His pre- premature beats as well as periods of apparent mature beats. Since there was no intrinsic abnor- second degree atrioventricular block were unin- mality ofthe atrioventricular conduction, they called fluenced by this therapy. His bundle recordings the resulting block, 'pseudo-block'. were then made to clarify the nature of the We report here a patient with bradycardia re- arrhythmia. sulting from pseudo second degree atrioventricular block caused by blocked His premature beats: he Electrophysiological studies was successfully treated with quinidine. The His bundle electrogram was recorded simul- on September 24, 2021 by guest. Protected taneously with lead II of the surface electrocardio- Case report gram at a paper speed of 100 mm/s. Several hundred cardiac cycles were analysed. The majority of the A 54-year-old man reported to the hospital com- beats recorded were sinus beats, with normal AH plaining of tiredness and weakness. There was a and HV intervals. The QRS complex of these sinus history of heavy alcoholic intake, but the patient beats was normal in duration. Premature beats oc- had discontinued drinking a few months before. curred at an average frequency of 3 to 5 per minute. There was no history of palpitation or dizziness. These beats could be separated into two types ac- Physical examination revealed an irregular pulse, cording to the behaviour of the QRS complex. with a basic rate of about 70 beats a minute but with In the first type, there was a minor change in QRS periodic slowing to almost 30 beats a minute. The morphology but without significant increase in blood pressure was 120/80 mmHg (16-0/10-6 kPa). its duration. The second type showed wide QRS There was no evidence of . The heart complexes resembling ventricular ectopic beats. size was normal, no gallop rhythm was heard, and The simultaneous His electrogram, however, Br Heart J: first published as 10.1136/hrt.38.12.1363 on 1 December 1976. Downloaded from

1364 Dhurandhar, Valen, and Phillips

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Pseudo second degree AV block with bradycardia 1365 showed a consistent presence of a His spike pre- 1000 ceding the V deflection in both types of premature beats localizing their origin to the His bundle (Fig. Ic, d). These two types ofpremature beats were 900 His extrasystoles, one type with slight and the 0 other with more aberrant ventricular conduction. 6 Periods of second degree atrioventricular block with 800 0 non-conducted normal P waves occurred at 0O frequency of about 10 a minute. The surface A 0 El electrocardiogram showed that the block was type la 0 0 II in nature and occurred without a change in PR 700 interval of the preceding sinus beats. At no time B. Q Blocked H' was more than one beat blocked in succession. His o{ H ' conducted with obvious bundle recordings during these periods showed 600' aberration spikes preceding the blocked A deflection (Fig. lb). 0{ H' conducted with slight The latter corresponded to the non-conducted ab erration normal P waves. As the patient had conducted His 500 premature beats throughout the recording, it is reasonable to conclude that these spikes represented His premature beats with both retrograde and 400 500 boo 7' 0 800 anterograde block. These spikes will be designated H- H' Interval (ims) as H'. H'-A interval varied between 94 and 304 ms F I G 2 The effect of timing of H' on conduction to with an average interval of 212 ms. Every blocked the ventricles. Abscissa: H-H' intervals; Ordinate: sinus beat was preceded by H'. The behaviour ofthe preceding H-H intervals Note that His premature His premature beat was determined primarily by the beats with short H-H' interval are blocked while those interval between the H spike of the preceding sinus with long H-H' interval are conducted with slight copyright. beat and the H'. The His extrasystoles with short aberration. His prematures with obvious aberration H-H' intervals were blocked, while those with long fall in between these two groups. The preceding H-H H-H' intervals were conducted with slight aberra- intervals do not appear to influence the behaviour tion. The H-H' interval of the premature beats with of the His extrasystoles. greater degree of aberration fell between these 2 groups. These three types of His premature beats could clearly be separated into three groups, de- treatment of apparent second degree atrioventricular http://heart.bmj.com/ termined by the length of the H-H' interval (Fig. block with quinidine, a drug which normally would 2). be considered contraindicated in atrioventricular block. It is important to recognize the 'pseudo' Hospital course nature of the block. The diagnosis should be sus- Quinidine sulphate, 200 mg, four times a day was pected when a patient presents with apparent given in an attempt to suppress the premature beats. type II atrioventricular block with narrow QRS Within 24 hours, the premature beats as well as complexes but who also shows junctional premature

periods of pseudo atrioventricular block were com- beats elsewhere in the electrocardiogram. The usual on September 24, 2021 by guest. Protected pletely abolished and did not recur during a seven- day period of observation with continuous electro- On quinidine Lead II cardiographic monitoring (Fig. 3). Quinidine was then stopped, and within 12 hours the premature beats as well as the pseudo second degree atrio- ~~'' ventricular block reappeared. The arrhythmia con- tinued for 36 hours until quinidine therapy was re- started, at which time the arrhythmia again dis- appeared. During a one-year follow-up under quinidine therapy, there has been no recurrence of the arrhythmia. F IG 3 The electrocardiogram recorded after quini- Discussion dine therapy was started The premature beats as well as periods of second degree atrioventricular block are This case is an interesting example of successful no longer present. Br Heart J: first published as 10.1136/hrt.38.12.1363 on 1 December 1976. Downloaded from

1366 Dhurandhar, Valen, and Phillips settings for atrioventricular block, such as myo- conduction within the atrioventricular junction. We cardial infarction and digitalis toxicity, may not be did not encounter any sinus beats conducted to the present. The presence of His premature beats ventricles with prolonged AH interval following the showing both retrograde and anterograde block blocked H', as described by Rosen et al. (1970). The should be shown by His electrogram before em- unique success of quinidine in abolishing the barking on a trial of quinidine. significant bradyarrhythmia in this patient elimi- In our patient, the reason for occurrence of His nated the need for implanting a permanent pace- premature beats was not clear. They did not appear maker. to be re-entrant beats, as the coupling interval varied. The premature beats occurred irregularly and did not appear to arise from a parasystolic focus. References Blocked premature beats may arise from any part Langendorf, R., and Mehlman, J. S. (1947). Blocked (non- of the His-Purkinje system but the presence of con- conducted) A-V nodal premature systoles imitating first ducted premature beats preceded by a His spike and second degree A-V block. American Heart Journal, 34, 500. localized their origin to the His bundle. The interval Rosen, K. M., Rahimtoola, S. H., and Gunnar, R. M. (1970). between the H deflection ofthe preceding sinus beat Pseudo A-V block secondary to premature nonpropagated and the H' determined the conduction of the pre- His bundle depolarizations. Circulation, 42, 367. mature beats to the ventricles. With shorter H-H' intervals the premature beats showed both retro- Requests for reprints to Dr. R. W. Dhurandhar, grade and anterograde block, and consistently Touro Infirmary, 1401 Foucher Street, New blocked the following sinus impulse by concealed Orleans, Louisiana 70115, U.S.A. copyright. http://heart.bmj.com/ on September 24, 2021 by guest. Protected