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Pseudo A-V block secondary to concealed junctional extrasystoles
Pseudo A-V Block Secondary to Concealed Junctional Extrasystoles Case Report and Review of the Literature
JONATHAN
ABRAM&
JAY R. DYKSTRA.
M.D.
M.D.
Albuquerque, New Mexico
A 23 year old woman, convalescing from a motorcycle accident, was noted to have a complex arrhythmia. Short bursts of apparent ventricular tachycardia, sudden P-R delays, and Mobitz I and Mobitz II block were observed as well as frequent junctional premature systoles. Careful analysis revealed that the rhythm disturbances were caused entirely by manifest and concealed atrioventricular (A-V) junctional extrasystoles. This case meets the criteria for concealed junctional extrasystoles producing “pseudo A-V block.” Pertinent literature is reviewed, and the manifestations of variable antegrade and retrograde conduction of A-V junctional extrasystoles are discussed. Increased awareness of this unusual rhythm disturbance can prevent unnecessary pacemaker therapy for apparent A-V block. In recent years experimental and clinical studies have done much to clarify abnormalities of impulse formation and conduction in the atrioventricular (A-V) junction [l-8]. Impulses arising in A-V junctional tissues, including the His bundle, can affect subsequent A-V conduction by concealed penetration into the A-V node and distal specialized conduction system [5,9-191; His bundle recordings have documented the effect of A-V junctional or His extrasystoles on the rhythm of the heart [9,12,20-221. Such A-V junctional extrasystoles can cause unexplained prolongation of the P-R interval, apparent blocked premature atrial contractions, atrial fusion beats, and electrocardiographic patterns resembling Mobitz I and II block [9,12-221. Recognition of these simulated conduction disturbances is most important to avoid placement of a temporary or permanent intracardiac pacemaker. The following case demonstrates multiple A-V junctional or His bundle extrasystoles, both manifest and concealed, producing a galaxy of rhythm disturbances, including apparent Wenckebach cycling, Mobitz II block and sudden P-R delays. Although His bundle recordings were not available, the features in this case are similar to those previously reported [ 16,19,20] and, as such, represent an unusual variety of “pseudo atrioventricular block.”
From the Cardiology Division, University of New Mexico School of Medicine, Albuquerque, New Mexico. Requests for reprints should be addressed to Dr. Jonathan Abrams. University of New Mexico School of Medicine, Department of Medicine, Albuquerque, New Mexico 87 131. Manuscript accepted September 18. 1976.
434
September 1977
CASE
REPORT
A 23 year old woman was admitted to Rehoboth Christian Hospital in Gallup, New Mexico,
on May 25, 1974, following a motorcycle
accident.
She sus-
tained multiple trauma, including fractures of the right femur and tibia, and a cerebral concussion. She underwent debridement the right femur and knee, and was placed in traction.
The American Journal of Medlclne
Volume 63
and surgical repair of
Two days after admis-
PSEUDO A-V BLOCK AND CONCEALED JUNCTIONAL
Figure 1. tracing, of frequently A-V block
EXTRASYSTOLES-ABRAMS,
DYKSTRA
lead electrocardiogram and rhythm strip taken on June 27, 1974, when the arrhythmia was first noted. The A poor quality, shows frequent atrioventricular junctional extrasystoles, some with aberrant conduction. The latter, occurring in couplets, were initially thought to be premature ventricular contractions. In addition. intermittent 2: I with a narrow QRS is seen with apparent Mobitz II configuration (rhythm strip).
sion, because of the sudden onset of dyspnea and confusion, she was believed to have suffered a fat embolus. She was treated with 10 per cent dextran and heparin, and the symptoms resolved without sequelae. Seventeen days after admission, she underwent debridement and grafting of the knee wound. On the 34th day of hospitalization, she was found to have an irregular pulse. An electrocardiogram (Figure 1) was interpreted as showing intermittent second degree heart block with supraventricular and ventricular extrasystoles; aside from the arrhythmias, the electrocardiogram was within normal limits. The patient complained of palpitations, but her condition was otherwise stable. The findings on cardiopulmonary examination remained within normal limits. Careful questioning revealed no history suggestive of cardiovascular disease, nor symptoms of palpitations in the past. A chest film and serum electrolytes were within normal limits. No specific antiarrhythmic treatment was given. The patient was continuously monitored; throughout the day she continued to manifest frequent premature ectopic supraventricular
beats, some with aberrant conduction of left bundle branch block configuration (Figure 2A and B). Occasional group beating of the aberrant extrasystoles occurred, simulating ventricular tachycardia (Figure 2C). She continued to have episodic arrhythmias, and two days later iapparent Mobitz type II block again developed, with sudden dropped beats, but with a narrow QRS (Figures 3A and 4C). In addition, sudden P-R delays occurred (Figure 38). and occasional Wenckebach periodicity (Mobitz type I) was noted (Figure 4A and B). At all times, there were numerous junctional premature systoles, both with a narrow QRS and, less commonly, with aberrant conduction (Figures 3 and 4). Later that day, a long run of apparent second degree A-V block with 2: 1 conduction occurred, interrupted by salvos of junctional extrasystoles of normal and wide QRS duration (Figure 5). During this time, the patient was noted to be depressed and was taking unknown amounts of Compoz@ (each tablet containing 0.15 mg of scopolamine, 15 mg of methapyrilene and 10 mg of pyrilamine maleate). This medication was
September 1977
The American Journal of Medicine
Volume 63
435
PSEUDO
A-V
BLOCK
AND
CONCEALED
JUNCTIONAL
EXTRASYSTOLES-ABRAM.
DYKSTRA
ICOPM
5110 PM
IOIICIPM
FIgwe 2. (A//monitor strips recorded on June 28, 7974.) A, siflus tachycardiawith frequent A-V junctional premature beats, many with narrow and wide QRS configuration. It is of interest that all but one of the aberrantly conducted extrasystoles follow a long R-R cycle. B, couplets of junctional extrasystoles resulting in a variant of trigeminy; the first of each extrasystole shows aberrant conduction (after a long R-R cycle). This sequence mimics premature interpolated beats, but careful analysis of the P waves suggests that the third beat of each triplet is premature, with a normal QRS; there is concealed retroconduction to the A-V node, resulting in failure of the subsequent sinus beat to conduct to the ventricles. C, frequent A-V junctional systoles in bursts of 2 and 3; three successive aberrantly conducted impulses simulate a salvo of ventricular tachycardia.
A.
100 AM
B.
4m
AM
C.
730
AM
A
I
I
A-V J V
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Figure 3. (Mon~or stnps recoraea on June W, 7974.) A, trequent A-V jUt?CtiOnal extrasystoles, i~CluUif?g one burst of irregular junctional tachycardia. Two cycles of 2: 1 A-V block of apparent Mobitz II type are seen. One aberrant extrasystole is seen following a long R-R cycle. Unexplained P-R delay occurs but is obvious only with the aid of the ladder diagram. B, sudden P-R delays, followed by manifest A-V junctional premature beats. This phenomenon is repetitive. It is possible that there is a completely concealed ectopic impulse with antegrade and retrograde exit block after every second extrasystole. C, frequent groupings of three beats are seen, at first glance due to couplets of extrasysfoles. The /adderdiagram suggests that the fhird complex of each triad is actually conduct&; if may also represent a true junctional extrasystole. There is intermittent aberrant conduction, simulating premature ventricular contractions. Note that the “coupling” interval of the second and third beats of each triad is similar, both when there is a narrow and wide QRS.
436
September
1977
The American Journal of Medicine
Volume 63
PSEUDO A-V BLOCK AND CONCEALED JUNCTIONAL EXTRASYSTOLES-ABRAM,
MOBITZ
DYKSTRA
I 3x45 PM
MOBITZ
II 2;oo PM
Figure 4. (Monytor strips recorded on June 30, 1974.) A, second degree A-V block with a 3:2 Wenckebach cycle is seen in the second and third complexes. Note the sudden P-R delay of the eighth complex, but rather than a subsequent nonconducted P wave, an (manifest) aberrant junctional extrasystole follows. Other narrow extrasystoles are seen, implying a high rate of ectopic pacemaker discharge. t3, more Wenckebach cycling, 3:2 and 4:3. The last two groupings are atypical in that there is no detectable P-R delay in the first two beats of each cycle. No manifest extrasystoles are seen. C, a run of 2: I A-V block is seen, initiated by sudden dropped beats (Mobitz II). Note the extrasystoles at the beginning and end.
supplied by friends and family. At times, she was noted to be hyperalert and excited: at no time did she complain of cardiac symptoms other than palpitations. One week after its onset, the arrhythmia completely disappeared and was never again noted. An electrocardiogram taken at that time showed no abnormalities except for slight T-wave lowering. Subsequently the patient underwent grafting of her skin wounds and open reduction of the right femur fracture. She was discharged 23 days after the last known arrhythmic episode and has had an uneventful recovery. COMMENTS
Arrhythmias Produced by Concealed A-V Junctional Extrasystoles. Review of the literature: In 1947, Langendorf and Mehlman [13] first suggested that premature impulses arising in the region of the A-V node could simulate heart block. They described a patient with A-V nodal premature beats, associated with episodes of sudden lengthening of the P-R interval, “dropped” beats and apparent blocked premature atrial contractions. They postulated intermittent antegrade and/or retrograde block of the nodal premature beats, with subsequent alteration in conduction of the next sinus impulse. If antegrade block occurred, only retro-
September
grade P waves were seen, simulating blocked premature atrial contractions: if both retrograde and antegrade block of the premature impulse ex.isted at any given moment, subsequent A-V conduction of the next sinus beat could be delayed or totally blocked due to concealed penetration of the A-V node ‘by the nonmanifest premature beat. In an early discussion of His bundle extrasystoles, Fletcher [ 141 described a patient with A-V conduction delay which he attributed to “fatigue” in the postextrasystolic beats. Langendorf later published a “most unusual” case of alternating P-R intervals due to blocked A-V nodal premature beats ([ 151, Case A7), and in the 1960s Need and Fisch reported a case of apparent heart block and blocked premature atrial contractions due to “concealed premature A-V node discharge” [ 161. Other sporadic reports suggested a similar mechanism whereby concealed conduction of junctional extrasystoles resulted in A-V conduction delays [ 17,181, including apparent Wenckebach periodicity [ 191. The advent of His bundle recordings has confirmed previous speculations regarding the effects of A-V junctional extrasystoles. Damato and associates were the first to document that nodal rhythms can originate in the His bundle [8], and they were able to produce
1977
The American
Journal of Medicine
Volume
63
437
PSEUDO
A-V
BLOCK
AND CONCEALED JUNCTIONAL EXTRASYSTOLES-ABRAM
DYKSTRA
I I Figure 5. (Monitor strips recorded on June 30, 1974.) A sustained run of 2: 7 A-V block is seen (much not mounted), briefly terminated by manifest extrasystoles, with normal and aberrant conduction.
A-L’
NODE
ii IS
BUNDLE
EXTRASYSTOLES
-+-4-L-++-%%-AHV
+++--%+ AHV
A
.
.
HV
AHV
HA .
A HV
1
Figure 6. Effects of His bundle or A-V junctional extrasystoles on the scalar electrocardiogram and His bundle recording (see text). A, retrograde block. Antegrade conduction. B, retrograde block. Antegrade conduction with aberration. C, retrograde and antegrade block. Concealment in the A-V node producing a long P-R interval. D, retrograde and antegrade block. Concealment in A-V node resulting in complete block of conduction of the subsequent sinus P wave.
many ostensible A-V conduction disturbances in dogs by appropriately timed premature stimulation of the His bundle [I I]. intermittent antegrade and retrograde block of the premature His impulses was frequently seen. Clinical arrhythmias simulated in this manner include (1) nonconducted atrial bigeminy, (2) alternation of the P-R interval, (3) Mobitz type I and type II block, and
438
September
1977
The American
Journal of Medicine
(4) 2: 1 A-V block. Damato emphasized that, depending
on the state of refractoriness of the His-Purkinje tissue, a ventricular response may or may not be manifest; concealed retrograde penetration of the A-V node by the His extrasystole can subsequently produce conduction disturbances simulating A-V block. In 1970, Rosen et al. [20], using His bundle recordings, docu-
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63
PSEUDO A-V BLOCK AND CONCEALED JUNCTIONAL EXTRASYSTOLES-ABRAMS. DYKSTRA
mented a case very similar to the present one. A patient with sudden P-R interval delay, Mobitz type I and II second degree A-V block, and occasional junctional extrasystoles, was found to have frequent premature His spikes every several beats, with variable (nonfixed) coupling. In every instance of a conduction disturbance, a nonconducted premature His deflection was seen, which was usually concealed on the surface electrocardiogram. Retrograde penetration of the atrium was not found; antegrade conduction was seen in 18 per cent of the premature His deflections, producing a normal or aberrant QRS. Rosen emphasized that the presence of unexplained P-R prolongation or type I and type II A-V block with normal QRS duration, when associated with junctional premature beats, should suggest that His bundle extrasystoles are the sole cause of the arrhythmia. His bundle extrasystoles have been documented by His recordings to produce related arrhythmias in two other cases [21,22]. In one patient, nonconducted premature atrial beats were simulated by His premature beats with aberrant ventricular conduction [21]. Another patient with underlying prolongation of A-H and H-V conduction was found to have blocked premature atrial contractions, atrial fusion beats and apparent Mobitz type II block as a result of appropriately timed premature junctional depolarizations [22]. Two cases with apparent A-V conduction disturbance due to an A-V junctional parasystole with concealed junctional premature beats have been reported [ 17,181, but without His bundle recordings. Documented His bundle automaticity has also been implicated in other complex arrhythmias [9,23,24]. Concealed premature impulses arising beyond the His bundle bifurcation and resulting in abnormalities of A-V conduction have also been documented [ 25,261. Analysis of Present Case. The case reported here fits all the criteria suggested by others [ 10,13,20,21] as a primary junctional or His bundle arrhythmia producing A-V conduction disturbances. A His bundle recording was not available and could have firmly documented the proposed mechanism. However, the sudden P-R delays and apparent Mobitz I and II block, in the presence of frequent multiple junctional premature beats, point to a single mechanism. In addition, it would be most unusual to find Mobitz II block with a normal QRS interval in an otherwise normal young woman. The precise timing of the His or junctional premature beats, in relation to the state of refractoriness of the distal HisPurkinje conducting tissue, determines whether the premature discharge will be manifest or concealed [ 11,121. If the premature depolarization occurs well after the preceding QRS, and finds the distal conduction system fully recovered, a normal QRS will occur as a
TABLE I
Possible Effects of Concealed Atrioventricular Junctional Extrasystoles
1. Unexpected P-R interval delay 2. 3. 4. 5. 6. 7.
Alteration of P-R intervals Type I second degree A-V block Type II second degree A-V block 2: 1 second degree A-V block Atrial fusion beats Simulate blocked premature atrial contractions
typical junctional or His extrasystole (Figure 6A). If the His ectopic beat is slightly earlier, or if the distal HisPurkinje tissue has not fully recovered, an aberrantly conducted QRS will be seen (Figure 6B). In these examples, there is complete retrograde block, without penetration beyond the A-V node. If ,the premature His beat occurs close to the following normal P wave, it may penetrate the A-V nodal tissue in a concealed fashion and either delay conduction of the next beat (Figure 6C), producing first degree A-V block, or totally block the next sinus impulse, producing the pattern of high-grade A-V block (Figure 6D). (In both of these examples, there is a total antegrade block, allowing the next sinus P wave to be clearly seen, rather than buried in the premature QRS or T wave.) Although in the present report, concealed retrograde block was complete at the A-V node, this is not always the case; negative P waves, simulating (blocked) premature atrial contractions or atrial fusion beats, can be seen when the His extrasystole retrogradely captures the atrium [8,13, 16,21,22]. When there is a regular discharge of the ectopic focus, e.g., every second beat, a sustained “pseudo” 2:l A-V block pattern can be seen, with failure of antegrade and retrograde conduction of the extrasystole every other beat (Figure 5). This arrhythmia was also produced by timed His bundle pacing in dogs by Damato et al. [ 111. Variations in timing and frequency of the premature discharge result in different patterns of A-V conduction disturbance and can simulate type I or type II A-V block [ 121, as in Figure 1. The various possible electrocardiographic manifestations of concealed A-V junctional extrasystoles are listed in Table I. Origin of Ectopic Impulses. Although the precise origin of the ectopic pacemaker is in questlion, it surely occurs in the region of the A-V junction. There is good evidence that ectopic impulse formation can occur in the His bundle [ 271, and some have suggested that most A-V junctional arrhythmias originate thelre [ 3,8]. There are conflicting opinions as to whether .the A-V node itself can initiate automatic rhythms [l-8 I. Hoffman and Cranefield [I] have shown that there is no pacemaker
September 1977
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439
PSEUDO A-V BLOCK AND CONCEALED JUNCTIONAL EXTRASYSTOLES-ABRAM&
in the N region of the A-V node, whereas Watanabe and Dreifus [6] have demonstrated potential automatic activity in the AH and NH regions of the rabbit A-V node. In any case, many investigators agree that His bundle extrasystoles, both manifest and concealed, do exist and can result in “pseudo” A-V block when properly timed and concealed [B- 13,16-221. Clinical Implications. It is important that clinicians become familiar with this unusual occurrence for several reasons. First, it is generally a benign phenomenon and apparently short-lived [ 17,18,20-221; second, proper recognition will avoid the necessity, cost and possible morbidity of erroneous pacemaker implantation for apparent heart block; and third, it serves to emphasize the electrophysiologic concepts of concealed conduction, antegrade and retrograde block, and the functional characteristics of the A-V junction. This mechanism should be particularly suspected whenever unusual A-V conduction disturbances occur in the presence of junctional extrasystoles, especially when activity
DYKSTRA
apparent type II A-V block is seen with a narrow QRS interval. ADDENDUM Since this manuscript was prepared, Fisch et al. 1281 published a series of 10 cases of concealed junctional ectopic impulses. His bundle recordings were found to be of little help in diagnosis. In addition to the manifestations already discussed, they made several new observations: (1) marked prolongation of the P-R interval, often greater than 400 msec; (2) persistence of this prolongation for more than one beat; (3) postponed compensatory pauses; (4) reciprocation due to concealed junctional discharge; and (5) varying P-R and R-P intervals suggesting supernormal conduction. ACKNOWLEDGMENT We would like to thank Ms. Audrey Tuck for her invaluable help in preparation of the manuscript and Dr. Barry W. Ramo for his helpful review.
REFERENCES
2. 3. 4.
5.
6.
7.
a. 3. 10.
11.
12.
13.
14.
440
Hoffman BF, Cranefield PF: The physiologic basis of cardiac arrhythmias. Am J Med 37: 670. 1964. Watanabe Y, Dreifus LS: Newer concepts in the genesis of cardiac arrhythmias. Am Heart J 76: 114, 1968. Hiejima K, Suzuki F, Sano T: Origin of “A-V nodal” rhythm. Jap Heart J 14: 273, 1973. de Azevedo IM, Watanabe Y, Dreifus LS: Atrioventricular junctional rhythm: classification and clinical significance. Chest 64: 732, 1973. Spear JF, Moore EN: lntranodal conduction, chap 2 1. Cardiac Arrhythmias (Dreifus LS. Likoff W, eds), New York, Grune & Stratton, Inc., 1973, p 238. Watanabe Y. Dreifus LS: Sites of impulse formation within the atrioventricolar junction of the rabbit. Circ Res 22: 717, 1968. Scherlag BJ, Abelleira JL, Yeh BK: Physiological differentiation of middle, lower A-V nodal and His bundle rhythms in the dog (abstract). Fed Proc 23: 587, 1970. Damato AN, Lau SH: His bundle rhythm. Circulation 40: 527, 1969. Massumi RA: Interpolated His bundle extrasystoles. Am J Med 49: 265, 1970. Damato AN, Gallagher JJ, Caracta AR, et al.: Subjunctional conduction, chap 26. Cardiac Arrhythmias (Dreifus LS, Likoff W. eds), New York, Grune 8 Stratton, Inc., 1973, p 371. Damato AN, Lau SH, Bobb G: Cardiac arrhythmias simulated by concealed bundle of His extrasystoles in the dog. Circ Res 28: 316, 1971. Moore EN, Spear JF: Local block and reentry, chap 5. Cardiac Arrhythmias (Dreifus LS, Likoff W, eds), New York, Grune & Stratton, Inc., 1973, p 76. Langendorf R, Mehlman JS: Blocked (nonconducted) A-V nodal premature systoles imitating first and second degree A-V block. Am Heart J 34: 500, 1947. Fletcher E: Extrasystoles arising from the main bundle of His. Br Heart J 17: 566, 1955.
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15. 16.
17.
18.
19.
20.
21
22.
23. 24. 25. 26.
27. 28.
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Langendorf R: Alternation of A-V conduction time. Am Heart J 55: 181, 1958. Need RL. Fisch C: Heart block resulting from concealed discharge of the atrioventricular node. Am J Cardiol 10: 138, 1962. Schamroth L, Surawicz B: Concealed interpolated A-V junctional extrasystoles and A-V junctional parasystole. Am J Cardiol 27: 703, 1971. Lindsay AE, Schamroth L: Atrioventricular junctional parasystole with concealed conduction simulating second degree atrioventricular block. Am J Cardiol 31: 397, 1973. Langendorf R, Pick A: Concealed conduction in the A-V junction. Cardiac arrhythmias (Dreifus LS, Likoff W, eds), New York, Grune 8 Stratton, Inc., 1966, p 337. Rosen KM, Rahimtoola SH, Gunnar RM: Pseudo A-V block secondary to premature nonpropagated His bundle depolarizations. Circulation 42: 367, 1970. Cannom DS, Gallagher JJ, Goldreyer BN, et al.: Concealed bundle of His extrasystoles simulating nonconducted atrial premature beats:Am Heart J 83: 777, 1972. Eugster GS, Godfrey CC, Brammell HL, et al.: Pseudo A-V block associated with A-H and KV conduction defects. Am Heart J 85: 789, 1973. Lightfoot PR: His bundle parasystole. A form of A-V junctional parasystole. Chest 66: 695, 1974. Gavrilescu S, Luca C: His bundle rhythms with retrograde conduction to the atria. Br Heart J 36: 468, 1974. Friedberg HD: Concealed extrasystoles. Am J Cardio124: 283, 1969. Castellanos A. Befeler B, Myerburg RJ: Pseudo A-V block produced by concealed extrasystoles below the bifurcation of the His bundle. Br Heart J 36: 457, 1974. Cranefield PF. Wit AL, Hoffman BF: Genesis of cardiac arrhythmias. Circulation 47: 190. 1973. Fisch C. Zipes DP. McHenry PL: Electrocardiographic manifestations of concealed junctional ectopic impulses. Circulation 53: 217. 1976.
JONATHAN
ABRAM&
JAY R. DYKSTRA.
M.D.
M.D.
Albuquerque, New Mexico
A 23 year old woman, convalescing from a motorcycle accident, was noted to have a complex arrhythmia. Short bursts of apparent ventricular tachycardia, sudden P-R delays, and Mobitz I and Mobitz II block were observed as well as frequent junctional premature systoles. Careful analysis revealed that the rhythm disturbances were caused entirely by manifest and concealed atrioventricular (A-V) junctional extrasystoles. This case meets the criteria for concealed junctional extrasystoles producing “pseudo A-V block.” Pertinent literature is reviewed, and the manifestations of variable antegrade and retrograde conduction of A-V junctional extrasystoles are discussed. Increased awareness of this unusual rhythm disturbance can prevent unnecessary pacemaker therapy for apparent A-V block. In recent years experimental and clinical studies have done much to clarify abnormalities of impulse formation and conduction in the atrioventricular (A-V) junction [l-8]. Impulses arising in A-V junctional tissues, including the His bundle, can affect subsequent A-V conduction by concealed penetration into the A-V node and distal specialized conduction system [5,9-191; His bundle recordings have documented the effect of A-V junctional or His extrasystoles on the rhythm of the heart [9,12,20-221. Such A-V junctional extrasystoles can cause unexplained prolongation of the P-R interval, apparent blocked premature atrial contractions, atrial fusion beats, and electrocardiographic patterns resembling Mobitz I and II block [9,12-221. Recognition of these simulated conduction disturbances is most important to avoid placement of a temporary or permanent intracardiac pacemaker. The following case demonstrates multiple A-V junctional or His bundle extrasystoles, both manifest and concealed, producing a galaxy of rhythm disturbances, including apparent Wenckebach cycling, Mobitz II block and sudden P-R delays. Although His bundle recordings were not available, the features in this case are similar to those previously reported [ 16,19,20] and, as such, represent an unusual variety of “pseudo atrioventricular block.”
From the Cardiology Division, University of New Mexico School of Medicine, Albuquerque, New Mexico. Requests for reprints should be addressed to Dr. Jonathan Abrams. University of New Mexico School of Medicine, Department of Medicine, Albuquerque, New Mexico 87 131. Manuscript accepted September 18. 1976.
434
September 1977
CASE
REPORT
A 23 year old woman was admitted to Rehoboth Christian Hospital in Gallup, New Mexico,
on May 25, 1974, following a motorcycle
accident.
She sus-
tained multiple trauma, including fractures of the right femur and tibia, and a cerebral concussion. She underwent debridement the right femur and knee, and was placed in traction.
The American Journal of Medlclne
Volume 63
and surgical repair of
Two days after admis-
PSEUDO A-V BLOCK AND CONCEALED JUNCTIONAL
Figure 1. tracing, of frequently A-V block
EXTRASYSTOLES-ABRAMS,
DYKSTRA
lead electrocardiogram and rhythm strip taken on June 27, 1974, when the arrhythmia was first noted. The A poor quality, shows frequent atrioventricular junctional extrasystoles, some with aberrant conduction. The latter, occurring in couplets, were initially thought to be premature ventricular contractions. In addition. intermittent 2: I with a narrow QRS is seen with apparent Mobitz II configuration (rhythm strip).
sion, because of the sudden onset of dyspnea and confusion, she was believed to have suffered a fat embolus. She was treated with 10 per cent dextran and heparin, and the symptoms resolved without sequelae. Seventeen days after admission, she underwent debridement and grafting of the knee wound. On the 34th day of hospitalization, she was found to have an irregular pulse. An electrocardiogram (Figure 1) was interpreted as showing intermittent second degree heart block with supraventricular and ventricular extrasystoles; aside from the arrhythmias, the electrocardiogram was within normal limits. The patient complained of palpitations, but her condition was otherwise stable. The findings on cardiopulmonary examination remained within normal limits. Careful questioning revealed no history suggestive of cardiovascular disease, nor symptoms of palpitations in the past. A chest film and serum electrolytes were within normal limits. No specific antiarrhythmic treatment was given. The patient was continuously monitored; throughout the day she continued to manifest frequent premature ectopic supraventricular
beats, some with aberrant conduction of left bundle branch block configuration (Figure 2A and B). Occasional group beating of the aberrant extrasystoles occurred, simulating ventricular tachycardia (Figure 2C). She continued to have episodic arrhythmias, and two days later iapparent Mobitz type II block again developed, with sudden dropped beats, but with a narrow QRS (Figures 3A and 4C). In addition, sudden P-R delays occurred (Figure 38). and occasional Wenckebach periodicity (Mobitz type I) was noted (Figure 4A and B). At all times, there were numerous junctional premature systoles, both with a narrow QRS and, less commonly, with aberrant conduction (Figures 3 and 4). Later that day, a long run of apparent second degree A-V block with 2: 1 conduction occurred, interrupted by salvos of junctional extrasystoles of normal and wide QRS duration (Figure 5). During this time, the patient was noted to be depressed and was taking unknown amounts of Compoz@ (each tablet containing 0.15 mg of scopolamine, 15 mg of methapyrilene and 10 mg of pyrilamine maleate). This medication was
September 1977
The American Journal of Medicine
Volume 63
435
PSEUDO
A-V
BLOCK
AND
CONCEALED
JUNCTIONAL
EXTRASYSTOLES-ABRAM.
DYKSTRA
ICOPM
5110 PM
IOIICIPM
FIgwe 2. (A//monitor strips recorded on June 28, 7974.) A, siflus tachycardiawith frequent A-V junctional premature beats, many with narrow and wide QRS configuration. It is of interest that all but one of the aberrantly conducted extrasystoles follow a long R-R cycle. B, couplets of junctional extrasystoles resulting in a variant of trigeminy; the first of each extrasystole shows aberrant conduction (after a long R-R cycle). This sequence mimics premature interpolated beats, but careful analysis of the P waves suggests that the third beat of each triplet is premature, with a normal QRS; there is concealed retroconduction to the A-V node, resulting in failure of the subsequent sinus beat to conduct to the ventricles. C, frequent A-V junctional systoles in bursts of 2 and 3; three successive aberrantly conducted impulses simulate a salvo of ventricular tachycardia.
A.
100 AM
B.
4m
AM
C.
730
AM
A
I
I
A-V J V
\
\<\
I
I
I
\
\<\
I
I \i\
I
I \<\
I
I
I
\<
\,
-
Figure 3. (Mon~or stnps recoraea on June W, 7974.) A, trequent A-V jUt?CtiOnal extrasystoles, i~CluUif?g one burst of irregular junctional tachycardia. Two cycles of 2: 1 A-V block of apparent Mobitz II type are seen. One aberrant extrasystole is seen following a long R-R cycle. Unexplained P-R delay occurs but is obvious only with the aid of the ladder diagram. B, sudden P-R delays, followed by manifest A-V junctional premature beats. This phenomenon is repetitive. It is possible that there is a completely concealed ectopic impulse with antegrade and retrograde exit block after every second extrasystole. C, frequent groupings of three beats are seen, at first glance due to couplets of extrasysfoles. The /adderdiagram suggests that the fhird complex of each triad is actually conduct&; if may also represent a true junctional extrasystole. There is intermittent aberrant conduction, simulating premature ventricular contractions. Note that the “coupling” interval of the second and third beats of each triad is similar, both when there is a narrow and wide QRS.
436
September
1977
The American Journal of Medicine
Volume 63
PSEUDO A-V BLOCK AND CONCEALED JUNCTIONAL EXTRASYSTOLES-ABRAM,
MOBITZ
DYKSTRA
I 3x45 PM
MOBITZ
II 2;oo PM
Figure 4. (Monytor strips recorded on June 30, 1974.) A, second degree A-V block with a 3:2 Wenckebach cycle is seen in the second and third complexes. Note the sudden P-R delay of the eighth complex, but rather than a subsequent nonconducted P wave, an (manifest) aberrant junctional extrasystole follows. Other narrow extrasystoles are seen, implying a high rate of ectopic pacemaker discharge. t3, more Wenckebach cycling, 3:2 and 4:3. The last two groupings are atypical in that there is no detectable P-R delay in the first two beats of each cycle. No manifest extrasystoles are seen. C, a run of 2: I A-V block is seen, initiated by sudden dropped beats (Mobitz II). Note the extrasystoles at the beginning and end.
supplied by friends and family. At times, she was noted to be hyperalert and excited: at no time did she complain of cardiac symptoms other than palpitations. One week after its onset, the arrhythmia completely disappeared and was never again noted. An electrocardiogram taken at that time showed no abnormalities except for slight T-wave lowering. Subsequently the patient underwent grafting of her skin wounds and open reduction of the right femur fracture. She was discharged 23 days after the last known arrhythmic episode and has had an uneventful recovery. COMMENTS
Arrhythmias Produced by Concealed A-V Junctional Extrasystoles. Review of the literature: In 1947, Langendorf and Mehlman [13] first suggested that premature impulses arising in the region of the A-V node could simulate heart block. They described a patient with A-V nodal premature beats, associated with episodes of sudden lengthening of the P-R interval, “dropped” beats and apparent blocked premature atrial contractions. They postulated intermittent antegrade and/or retrograde block of the nodal premature beats, with subsequent alteration in conduction of the next sinus impulse. If antegrade block occurred, only retro-
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grade P waves were seen, simulating blocked premature atrial contractions: if both retrograde and antegrade block of the premature impulse ex.isted at any given moment, subsequent A-V conduction of the next sinus beat could be delayed or totally blocked due to concealed penetration of the A-V node ‘by the nonmanifest premature beat. In an early discussion of His bundle extrasystoles, Fletcher [ 141 described a patient with A-V conduction delay which he attributed to “fatigue” in the postextrasystolic beats. Langendorf later published a “most unusual” case of alternating P-R intervals due to blocked A-V nodal premature beats ([ 151, Case A7), and in the 1960s Need and Fisch reported a case of apparent heart block and blocked premature atrial contractions due to “concealed premature A-V node discharge” [ 161. Other sporadic reports suggested a similar mechanism whereby concealed conduction of junctional extrasystoles resulted in A-V conduction delays [ 17,181, including apparent Wenckebach periodicity [ 191. The advent of His bundle recordings has confirmed previous speculations regarding the effects of A-V junctional extrasystoles. Damato and associates were the first to document that nodal rhythms can originate in the His bundle [8], and they were able to produce
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DYKSTRA
I I Figure 5. (Monitor strips recorded on June 30, 1974.) A sustained run of 2: 7 A-V block is seen (much not mounted), briefly terminated by manifest extrasystoles, with normal and aberrant conduction.
A-L’
NODE
ii IS
BUNDLE
EXTRASYSTOLES
-+-4-L-++-%%-AHV
+++--%+ AHV
A
.
.
HV
AHV
HA .
A HV
1
Figure 6. Effects of His bundle or A-V junctional extrasystoles on the scalar electrocardiogram and His bundle recording (see text). A, retrograde block. Antegrade conduction. B, retrograde block. Antegrade conduction with aberration. C, retrograde and antegrade block. Concealment in the A-V node producing a long P-R interval. D, retrograde and antegrade block. Concealment in A-V node resulting in complete block of conduction of the subsequent sinus P wave.
many ostensible A-V conduction disturbances in dogs by appropriately timed premature stimulation of the His bundle [I I]. intermittent antegrade and retrograde block of the premature His impulses was frequently seen. Clinical arrhythmias simulated in this manner include (1) nonconducted atrial bigeminy, (2) alternation of the P-R interval, (3) Mobitz type I and type II block, and
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(4) 2: 1 A-V block. Damato emphasized that, depending
on the state of refractoriness of the His-Purkinje tissue, a ventricular response may or may not be manifest; concealed retrograde penetration of the A-V node by the His extrasystole can subsequently produce conduction disturbances simulating A-V block. In 1970, Rosen et al. [20], using His bundle recordings, docu-
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mented a case very similar to the present one. A patient with sudden P-R interval delay, Mobitz type I and II second degree A-V block, and occasional junctional extrasystoles, was found to have frequent premature His spikes every several beats, with variable (nonfixed) coupling. In every instance of a conduction disturbance, a nonconducted premature His deflection was seen, which was usually concealed on the surface electrocardiogram. Retrograde penetration of the atrium was not found; antegrade conduction was seen in 18 per cent of the premature His deflections, producing a normal or aberrant QRS. Rosen emphasized that the presence of unexplained P-R prolongation or type I and type II A-V block with normal QRS duration, when associated with junctional premature beats, should suggest that His bundle extrasystoles are the sole cause of the arrhythmia. His bundle extrasystoles have been documented by His recordings to produce related arrhythmias in two other cases [21,22]. In one patient, nonconducted premature atrial beats were simulated by His premature beats with aberrant ventricular conduction [21]. Another patient with underlying prolongation of A-H and H-V conduction was found to have blocked premature atrial contractions, atrial fusion beats and apparent Mobitz type II block as a result of appropriately timed premature junctional depolarizations [22]. Two cases with apparent A-V conduction disturbance due to an A-V junctional parasystole with concealed junctional premature beats have been reported [ 17,181, but without His bundle recordings. Documented His bundle automaticity has also been implicated in other complex arrhythmias [9,23,24]. Concealed premature impulses arising beyond the His bundle bifurcation and resulting in abnormalities of A-V conduction have also been documented [ 25,261. Analysis of Present Case. The case reported here fits all the criteria suggested by others [ 10,13,20,21] as a primary junctional or His bundle arrhythmia producing A-V conduction disturbances. A His bundle recording was not available and could have firmly documented the proposed mechanism. However, the sudden P-R delays and apparent Mobitz I and II block, in the presence of frequent multiple junctional premature beats, point to a single mechanism. In addition, it would be most unusual to find Mobitz II block with a normal QRS interval in an otherwise normal young woman. The precise timing of the His or junctional premature beats, in relation to the state of refractoriness of the distal HisPurkinje conducting tissue, determines whether the premature discharge will be manifest or concealed [ 11,121. If the premature depolarization occurs well after the preceding QRS, and finds the distal conduction system fully recovered, a normal QRS will occur as a
TABLE I
Possible Effects of Concealed Atrioventricular Junctional Extrasystoles
1. Unexpected P-R interval delay 2. 3. 4. 5. 6. 7.
Alteration of P-R intervals Type I second degree A-V block Type II second degree A-V block 2: 1 second degree A-V block Atrial fusion beats Simulate blocked premature atrial contractions
typical junctional or His extrasystole (Figure 6A). If the His ectopic beat is slightly earlier, or if the distal HisPurkinje tissue has not fully recovered, an aberrantly conducted QRS will be seen (Figure 6B). In these examples, there is complete retrograde block, without penetration beyond the A-V node. If ,the premature His beat occurs close to the following normal P wave, it may penetrate the A-V nodal tissue in a concealed fashion and either delay conduction of the next beat (Figure 6C), producing first degree A-V block, or totally block the next sinus impulse, producing the pattern of high-grade A-V block (Figure 6D). (In both of these examples, there is a total antegrade block, allowing the next sinus P wave to be clearly seen, rather than buried in the premature QRS or T wave.) Although in the present report, concealed retrograde block was complete at the A-V node, this is not always the case; negative P waves, simulating (blocked) premature atrial contractions or atrial fusion beats, can be seen when the His extrasystole retrogradely captures the atrium [8,13, 16,21,22]. When there is a regular discharge of the ectopic focus, e.g., every second beat, a sustained “pseudo” 2:l A-V block pattern can be seen, with failure of antegrade and retrograde conduction of the extrasystole every other beat (Figure 5). This arrhythmia was also produced by timed His bundle pacing in dogs by Damato et al. [ 111. Variations in timing and frequency of the premature discharge result in different patterns of A-V conduction disturbance and can simulate type I or type II A-V block [ 121, as in Figure 1. The various possible electrocardiographic manifestations of concealed A-V junctional extrasystoles are listed in Table I. Origin of Ectopic Impulses. Although the precise origin of the ectopic pacemaker is in questlion, it surely occurs in the region of the A-V junction. There is good evidence that ectopic impulse formation can occur in the His bundle [ 271, and some have suggested that most A-V junctional arrhythmias originate thelre [ 3,8]. There are conflicting opinions as to whether .the A-V node itself can initiate automatic rhythms [l-8 I. Hoffman and Cranefield [I] have shown that there is no pacemaker
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in the N region of the A-V node, whereas Watanabe and Dreifus [6] have demonstrated potential automatic activity in the AH and NH regions of the rabbit A-V node. In any case, many investigators agree that His bundle extrasystoles, both manifest and concealed, do exist and can result in “pseudo” A-V block when properly timed and concealed [B- 13,16-221. Clinical Implications. It is important that clinicians become familiar with this unusual occurrence for several reasons. First, it is generally a benign phenomenon and apparently short-lived [ 17,18,20-221; second, proper recognition will avoid the necessity, cost and possible morbidity of erroneous pacemaker implantation for apparent heart block; and third, it serves to emphasize the electrophysiologic concepts of concealed conduction, antegrade and retrograde block, and the functional characteristics of the A-V junction. This mechanism should be particularly suspected whenever unusual A-V conduction disturbances occur in the presence of junctional extrasystoles, especially when activity
DYKSTRA
apparent type II A-V block is seen with a narrow QRS interval. ADDENDUM Since this manuscript was prepared, Fisch et al. 1281 published a series of 10 cases of concealed junctional ectopic impulses. His bundle recordings were found to be of little help in diagnosis. In addition to the manifestations already discussed, they made several new observations: (1) marked prolongation of the P-R interval, often greater than 400 msec; (2) persistence of this prolongation for more than one beat; (3) postponed compensatory pauses; (4) reciprocation due to concealed junctional discharge; and (5) varying P-R and R-P intervals suggesting supernormal conduction. ACKNOWLEDGMENT We would like to thank Ms. Audrey Tuck for her invaluable help in preparation of the manuscript and Dr. Barry W. Ramo for his helpful review.
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