- Email: [email protected]
Synchronization of auricular and ventricular beats during complete heart block
SYNCHRONIZATION OF AURICULAR BEATS DURING COMPLETE M. SEGERS, J. LEQUIME, BRUSSELS,
AND
AND HEART
VENTRICULAR BLOCK
H. DENOLIN
BELGIUM
experimental work, one of us has shown that, if two isolated frog hearts I NareANplaced in contact, there may occur a synchronization of their rhythm (Seger9); however, this phenomenon only occurs when the two hearts beat at almost the same rhythm. This proves that interreactions may be developed between neighboring tissues, even when no anatomic connections can be traced between them. It has been shown that such interreactions result from both anatomic and mechanical excitations which are exerted by each of the two hearts on the other. The existence of interreactions between distinct cellular elements placed in contact with each other is a well-known fact in regard to the nervous tissue. Jasper and Monnier3 have shown, for example, that an excitation can be transmitted from one neurone to another by simple contact. Phenomena of interneuronic synchronization have also been observed during rhythmic activity of peripheral nerves and in the central nervous system. In view of these facts, we had wondered whether similar interreactions might not occur between auricles and ventricles in patients presenting compIete A-V heart block. We were able to register such a phenomenon in the case which follows. REPORT
OF CASE
V. H., a. 77-year-old man,wasadmitted to the hospitalon Jan. 15, 1944. For six months he had been troubled by attacks of dizziness and unconsciousness, especially after exertion. On examination, the pulse was slow, with a rate of about 36 beats per minute. There was an occasional accentuation of the first sound. The roentgenogram showed an increase of all the diameters of the heart. Blood pressure was 220/120.
Electrocardiographic Findings.-Electrocardiograms were recorded daily with the patient at bed rest; they revealed an auriculoventricular block of a very peculiar type. The average duration of the P-P intervals was 0.85 second and that of the R-R intervals exactly twice as long, 1.70 seconds. These intervals changed spontaneously within limits that reached 10 per cent of their average duration. This fluctuation was independent of breathing, and irregular, but the auricular and ventricular rhythms always remained in a 2 :l ratio (Fig. 1). There From the Department of Medicine and Solvay Institute of Physiology, University of Brussels. Preliminary communication read at the Inter-American Congress of Cardiology, Mexico, D. F.. Oct. 5-12, 1946.
Fig. l.m--Record P-wave. marked by
of complete block a cross, remains in
--
-
.,
with A-V synchronizatiou. the close neighborhood
_.. -
Continuous tracing of R; the 3:l auriculoventricular
taken
with the patient synchronization
at hrd rest is obvious.
iT,rad
I\-
R).
EVWJ
l,ther
SEGERS
ET
AI,.
:
SYNCHROSIZATION
OF
AURICULAR
AND
VENTRICULAR
BEATS
687
was indeed a close correlation between the activities of the two pacemakers of the heart: in every other auricular cycle, the P wave occurred systematically a little before Or a little after the R wave. The respective positions of these two waves were not always the same: according to fluctuations of the rhythm, there was a constant wandering of the P position with respect to R, but the duration of the P-R or R-P interval never exceeded 0.18 second (Figs. 1 and 2). This connection was not fortuitous, for it was recorded daily in this patient, while he was at bed rest, in continuous tracings showing several hundred beats.
There interval
Fig. Z.-Positions of P with respect to R during 121 successive is a constant wandering of the position of the P wave with never exceeds 0.18 second.
ventricular respect
beats to R, but
(patient at rest). the P-R or R-P
The electrocardiograms had two characteristics. Whatever the duration of the recording, the auricular beats were always twice as numerous as the ventricular beats. Although there were slight fluctuations of the rhythm, every other P wave continued to be situated in close proximity to an R wave. However, this was not an incomplete dissociation of a 2:l type, since the P wave continuously changed its position with respect to the R wave. An exercise test produced an acceleration only of the auricular rhythm. With the increase in the auricular rate the symhronism of the two pacemakers disappeared (Fig. 4): but a few minutes after the exercise, the auricular rhythm slowed to its former rate and the 2:l synchronism reappeared. The fact that the auricular frequency could change without influencing either the rhythm or the form of the ventricular complexes shows that complete heart block existed. Either the 2:l auriculoventricular synchronism was merely fortuitous, or it was the result of neighborhood interreactions developing between the two pacemakers. The first hypothesis cannot be accepted, for several facts cannot be explained by chance alone. For instance, the fluctuations of the auricular and ventricular rhythms were not absolutely identical, but they did present a correlation, as is proved by the following numerical fact.s. The duration of two successive P-P intervals varied from 1.53 to 1.84 seconds; the R-R intervals varied from 1.54 to 1.80 seconds. If the two rhythms were independent, there could have been at times a difference of as much as 0.30 second in the duration of the simultaneous P-P-P and R-R intervals; this difference, however, never exceeded 0.10 second. In a more general way, if we measure systematically the difference between the simultaneous P-P-P and R-R intervals, we find a greater number of small values than could be attributed to chance alone (Fig. 3). This correla-
AMBHICAN
688
HEART
JOURNAL
tion between the fluctuations of the two rhythms cannot be attributed to a common vagosympathetic control, since an exercise test produced an acceleration of the auricular rhythm only. If the auriculoventricular synchronism was merely fortuitous, the I’ waves could have occupied any position relative to R; the fact is that the P-R or R-P This gives another proof intervals never became longer than 0.18 second at rest. of the correlation between the activities of the auricles and ventricles.
Various P-P-P
I durdtLonS
mtelvd:s
of’
the
:
2.::::
I.. . ,. ..I ., ,, ,.I. . . . .. . ,,.,*.a ..,. a... B .*.*.... . ,.*.,.4, . . ..s,.. . . .. * . . ., . . . . .s. . ,. . . . . ., . . .. . . .,.,.,.,.,*....,.. . . . . . . . . . . .. . . . . . . . . ... . . .. . .. . . .. .. . . . . . . . . . ..,,,.,... *a... . ,.,.,,..,.,,,.,,....,,..... 1 , I,‘sO lj’jO I.‘60 .
,
l
.
‘\
‘\
Fig. 3.-Statistical study of the fluctuations of the rhythm observed during 200 successive beats. A and B In A, B. and C the number of dots indicates the number of times each interval was observed. C concerns the differences show the frequency of appearance of the several P-P-P and R-R intervals. in duration between the simultaneous P-P-P and R-R intervals; the observed curve indicates how often The calculated curve shows how often these difl’erences would the various differences have been noted. appear if they were merely fortuitous; the curve is calculated according to the probabilities of combiThe number of small values is clearly higher than the nations between the numerical data of A and B. calculated one, which implies the existence of a correlation between the fluctuations of the P-P-P and R-R intervals.
As has been stated, after exercise the auricular rhythm was accelerated without a measurable increase of the ventricular rate; but even after exercise, the two pacemakers were not alwa,ys completely independent. When the increase in the auricular rate was not very much, the P waves did not constantly They did alter their relationchange their position with respect to the R waves. ship to R rapidly, from beat to beat, when the P waves were relatively far from
Fig. 4.-Complete block showing the claw and dependent association of P and R waves (ph&~onSne d’accrochage). Continuous tracing taken after light exertion. The dots mark the position of the P waves; the auricular and ventricular beats are numbered. The auricular waves indicated by an even number are “hooked” to the R wave during the first. twent.y ventricular beats. After a rapid change, the P waves marked with an uneven number assume the close association with R waves duringthe ventricular beats twenty-five to fifty. Then the same sequence of events takes place all over again.
the R waves, but they moved from the R waves slowly when the P-R or R-P intervals were small (Figs. 4 and 5). In other words, whenever the inter-\-al between the P and R waves was a small one, these waves had a tendency to remain closely associated or “hooked” together. This phenomenon undoubtedlyproves the presence of interreactiorrs between \-entricles and auricles which tends to synchronize their rhythms.
Fig. 5.-Position
of I’ with respect The wandering
to R during eighty successive ventricular of P becomes slower in the neighborhood
beats (after of R.
light
exertion).
DISCUSSION
The synchronization of auricular and ventricular rhythms during complete heart block is not a very frequent phenomenon, but when it occurs, it is not due merely to chance. That there exist neighborhood interreactions between auricles and ventricles is shown by the following facts: 1.
The auriculoventricular synchronism remains constant even when there are fluctuations of the rate amounting to as much as 10 per cent of the average rate. 2. The P waves remain always in close a,ssociation with the R waves. 3. Even when the synchronism is abolished by exercise, periodicahy the P and R waves may assume a close and apparently dependent association (phenomltne d’accrochage). The neighborhood interreactions responsible for the synchronization probably result from both mechanical and electrical excitation exerted by the ventricles on the auricles. But the relation so created is by no means as reliable as that normally assured by the bundle of His; indeed, slight exercise is sufficient to destroy the synchronization of the two pacemaSkers. Several authors”p4*6 have stated that, during complete heart block, the rhythms of the two pacemakers can remain synchronized in a 1 :1, 2 :l, or 3 :l ra; io. The case we have reported demonstrates this fact.
sIEGERS
ET
>\I~. :
STSCElRC)XIZhTION
01:
AURICULAR
AND
VENTRICULAR
BEATS
691
The condition described by French authors as “isorhythmic dissociation” seems to be explained by a similar phenomenon. Of course, in the isorhythmic dissociation, the conduction in the bundle of His is generally not altered, but there exists an autonomous and synchronous activity of auricles and ventricles. This autonomy of the two pacemakers results from the mutual “extinction” of the normal and retrograde impulses in the bundle of His;l such a peculiar state can be maintained as long as the two pacemakers beat at t,he same rhythm. If our interpretation of the isorhythmic dissociation is accepted, the block of the bundle of His should thus not be a necessary condition for the appearance of a synchronization between two distinct pacemakers in the heart. SUMMARY
During complete heart block, the auricular and ventricular rhythms may in After some cases remain synchronized in a 2:l ratio during very long periods. exercise, the synchronization disappears, but a close association of a P wave and an R wave (ph&omPne d’accrochage) may occur. These facts must be attributed to neighborhood interreactions developing between ventricles and auricles, without any conduction pathwa.y. They are similar to the synchronization which is observed when two frog hearts are placed in contact. We therefore conclude that -the rhythms of auricles and ventricles are independent during complete heart block. not necessarily REFERENCES
1. 2. 3. 4. 5. 6.
Dressier,
W.: Dissoziationen und Interferenzen bei partiellem Herzblock, Ztschr. f. Med. 111:23, 1929. Ueber das Vorkommen einfacher zahlenm&siger Beziehungen zwischen Fischer, R.: Frequenz dissoziiert schlagender Herzabschnitte, Ztschr. f. klin. Med. 116:466, A. M.: Transmission of Excitation Between Excised Jasper, H., and Monnier, Mpelinated Nerves. An Artificial Synapse, J. Cell. & Comp. Physiol. 11:259, Kisch, B.: Beobachtungen bei einem Kranken mit totalem Block, Cardiologia 2:47, de synchronisation au niveau du coeur, Arch. internat. Segers, M . : Les phenomenes Physiol. 54:87, 1946. Van Buchem, F. S. P.: Dissoziation zwischen Atrium und Ventrikel. Erklgrung des tiellen Herzblocks, Ztschr. f. klin. Med. 110:401, 1929.
klin. der 1931. Non1938. 1938. de par.
AND
AND HEART
VENTRICULAR BLOCK
H. DENOLIN
BELGIUM
experimental work, one of us has shown that, if two isolated frog hearts I NareANplaced in contact, there may occur a synchronization of their rhythm (Seger9); however, this phenomenon only occurs when the two hearts beat at almost the same rhythm. This proves that interreactions may be developed between neighboring tissues, even when no anatomic connections can be traced between them. It has been shown that such interreactions result from both anatomic and mechanical excitations which are exerted by each of the two hearts on the other. The existence of interreactions between distinct cellular elements placed in contact with each other is a well-known fact in regard to the nervous tissue. Jasper and Monnier3 have shown, for example, that an excitation can be transmitted from one neurone to another by simple contact. Phenomena of interneuronic synchronization have also been observed during rhythmic activity of peripheral nerves and in the central nervous system. In view of these facts, we had wondered whether similar interreactions might not occur between auricles and ventricles in patients presenting compIete A-V heart block. We were able to register such a phenomenon in the case which follows. REPORT
OF CASE
V. H., a. 77-year-old man,wasadmitted to the hospitalon Jan. 15, 1944. For six months he had been troubled by attacks of dizziness and unconsciousness, especially after exertion. On examination, the pulse was slow, with a rate of about 36 beats per minute. There was an occasional accentuation of the first sound. The roentgenogram showed an increase of all the diameters of the heart. Blood pressure was 220/120.
Electrocardiographic Findings.-Electrocardiograms were recorded daily with the patient at bed rest; they revealed an auriculoventricular block of a very peculiar type. The average duration of the P-P intervals was 0.85 second and that of the R-R intervals exactly twice as long, 1.70 seconds. These intervals changed spontaneously within limits that reached 10 per cent of their average duration. This fluctuation was independent of breathing, and irregular, but the auricular and ventricular rhythms always remained in a 2 :l ratio (Fig. 1). There From the Department of Medicine and Solvay Institute of Physiology, University of Brussels. Preliminary communication read at the Inter-American Congress of Cardiology, Mexico, D. F.. Oct. 5-12, 1946.
Fig. l.m--Record P-wave. marked by
of complete block a cross, remains in
--
-
.,
with A-V synchronizatiou. the close neighborhood
_.. -
Continuous tracing of R; the 3:l auriculoventricular
taken
with the patient synchronization
at hrd rest is obvious.
iT,rad
I\-
R).
EVWJ
l,ther
SEGERS
ET
AI,.
:
SYNCHROSIZATION
OF
AURICULAR
AND
VENTRICULAR
BEATS
687
was indeed a close correlation between the activities of the two pacemakers of the heart: in every other auricular cycle, the P wave occurred systematically a little before Or a little after the R wave. The respective positions of these two waves were not always the same: according to fluctuations of the rhythm, there was a constant wandering of the P position with respect to R, but the duration of the P-R or R-P interval never exceeded 0.18 second (Figs. 1 and 2). This connection was not fortuitous, for it was recorded daily in this patient, while he was at bed rest, in continuous tracings showing several hundred beats.
There interval
Fig. Z.-Positions of P with respect to R during 121 successive is a constant wandering of the position of the P wave with never exceeds 0.18 second.
ventricular respect
beats to R, but
(patient at rest). the P-R or R-P
The electrocardiograms had two characteristics. Whatever the duration of the recording, the auricular beats were always twice as numerous as the ventricular beats. Although there were slight fluctuations of the rhythm, every other P wave continued to be situated in close proximity to an R wave. However, this was not an incomplete dissociation of a 2:l type, since the P wave continuously changed its position with respect to the R wave. An exercise test produced an acceleration only of the auricular rhythm. With the increase in the auricular rate the symhronism of the two pacemakers disappeared (Fig. 4): but a few minutes after the exercise, the auricular rhythm slowed to its former rate and the 2:l synchronism reappeared. The fact that the auricular frequency could change without influencing either the rhythm or the form of the ventricular complexes shows that complete heart block existed. Either the 2:l auriculoventricular synchronism was merely fortuitous, or it was the result of neighborhood interreactions developing between the two pacemakers. The first hypothesis cannot be accepted, for several facts cannot be explained by chance alone. For instance, the fluctuations of the auricular and ventricular rhythms were not absolutely identical, but they did present a correlation, as is proved by the following numerical fact.s. The duration of two successive P-P intervals varied from 1.53 to 1.84 seconds; the R-R intervals varied from 1.54 to 1.80 seconds. If the two rhythms were independent, there could have been at times a difference of as much as 0.30 second in the duration of the simultaneous P-P-P and R-R intervals; this difference, however, never exceeded 0.10 second. In a more general way, if we measure systematically the difference between the simultaneous P-P-P and R-R intervals, we find a greater number of small values than could be attributed to chance alone (Fig. 3). This correla-
AMBHICAN
688
HEART
JOURNAL
tion between the fluctuations of the two rhythms cannot be attributed to a common vagosympathetic control, since an exercise test produced an acceleration of the auricular rhythm only. If the auriculoventricular synchronism was merely fortuitous, the I’ waves could have occupied any position relative to R; the fact is that the P-R or R-P This gives another proof intervals never became longer than 0.18 second at rest. of the correlation between the activities of the auricles and ventricles.
Various P-P-P
I durdtLonS
mtelvd:s
of’
the
:
2.::::
I.. . ,. ..I ., ,, ,.I. . . . .. . ,,.,*.a ..,. a... B .*.*.... . ,.*.,.4, . . ..s,.. . . .. * . . ., . . . . .s. . ,. . . . . ., . . .. . . .,.,.,.,.,*....,.. . . . . . . . . . . .. . . . . . . . . ... . . .. . .. . . .. .. . . . . . . . . . ..,,,.,... *a... . ,.,.,,..,.,,,.,,....,,..... 1 , I,‘sO lj’jO I.‘60 .
,
l
.
‘\
‘\
Fig. 3.-Statistical study of the fluctuations of the rhythm observed during 200 successive beats. A and B In A, B. and C the number of dots indicates the number of times each interval was observed. C concerns the differences show the frequency of appearance of the several P-P-P and R-R intervals. in duration between the simultaneous P-P-P and R-R intervals; the observed curve indicates how often The calculated curve shows how often these difl’erences would the various differences have been noted. appear if they were merely fortuitous; the curve is calculated according to the probabilities of combiThe number of small values is clearly higher than the nations between the numerical data of A and B. calculated one, which implies the existence of a correlation between the fluctuations of the P-P-P and R-R intervals.
As has been stated, after exercise the auricular rhythm was accelerated without a measurable increase of the ventricular rate; but even after exercise, the two pacemakers were not alwa,ys completely independent. When the increase in the auricular rate was not very much, the P waves did not constantly They did alter their relationchange their position with respect to the R waves. ship to R rapidly, from beat to beat, when the P waves were relatively far from
Fig. 4.-Complete block showing the claw and dependent association of P and R waves (ph&~onSne d’accrochage). Continuous tracing taken after light exertion. The dots mark the position of the P waves; the auricular and ventricular beats are numbered. The auricular waves indicated by an even number are “hooked” to the R wave during the first. twent.y ventricular beats. After a rapid change, the P waves marked with an uneven number assume the close association with R waves duringthe ventricular beats twenty-five to fifty. Then the same sequence of events takes place all over again.
the R waves, but they moved from the R waves slowly when the P-R or R-P intervals were small (Figs. 4 and 5). In other words, whenever the inter-\-al between the P and R waves was a small one, these waves had a tendency to remain closely associated or “hooked” together. This phenomenon undoubtedlyproves the presence of interreactiorrs between \-entricles and auricles which tends to synchronize their rhythms.
Fig. 5.-Position
of I’ with respect The wandering
to R during eighty successive ventricular of P becomes slower in the neighborhood
beats (after of R.
light
exertion).
DISCUSSION
The synchronization of auricular and ventricular rhythms during complete heart block is not a very frequent phenomenon, but when it occurs, it is not due merely to chance. That there exist neighborhood interreactions between auricles and ventricles is shown by the following facts: 1.
The auriculoventricular synchronism remains constant even when there are fluctuations of the rate amounting to as much as 10 per cent of the average rate. 2. The P waves remain always in close a,ssociation with the R waves. 3. Even when the synchronism is abolished by exercise, periodicahy the P and R waves may assume a close and apparently dependent association (phenomltne d’accrochage). The neighborhood interreactions responsible for the synchronization probably result from both mechanical and electrical excitation exerted by the ventricles on the auricles. But the relation so created is by no means as reliable as that normally assured by the bundle of His; indeed, slight exercise is sufficient to destroy the synchronization of the two pacemaSkers. Several authors”p4*6 have stated that, during complete heart block, the rhythms of the two pacemakers can remain synchronized in a 1 :1, 2 :l, or 3 :l ra; io. The case we have reported demonstrates this fact.
sIEGERS
ET
>\I~. :
STSCElRC)XIZhTION
01:
AURICULAR
AND
VENTRICULAR
BEATS
691
The condition described by French authors as “isorhythmic dissociation” seems to be explained by a similar phenomenon. Of course, in the isorhythmic dissociation, the conduction in the bundle of His is generally not altered, but there exists an autonomous and synchronous activity of auricles and ventricles. This autonomy of the two pacemakers results from the mutual “extinction” of the normal and retrograde impulses in the bundle of His;l such a peculiar state can be maintained as long as the two pacemakers beat at t,he same rhythm. If our interpretation of the isorhythmic dissociation is accepted, the block of the bundle of His should thus not be a necessary condition for the appearance of a synchronization between two distinct pacemakers in the heart. SUMMARY
During complete heart block, the auricular and ventricular rhythms may in After some cases remain synchronized in a 2:l ratio during very long periods. exercise, the synchronization disappears, but a close association of a P wave and an R wave (ph&omPne d’accrochage) may occur. These facts must be attributed to neighborhood interreactions developing between ventricles and auricles, without any conduction pathwa.y. They are similar to the synchronization which is observed when two frog hearts are placed in contact. We therefore conclude that -the rhythms of auricles and ventricles are independent during complete heart block. not necessarily REFERENCES
1. 2. 3. 4. 5. 6.
Dressier,
W.: Dissoziationen und Interferenzen bei partiellem Herzblock, Ztschr. f. Med. 111:23, 1929. Ueber das Vorkommen einfacher zahlenm&siger Beziehungen zwischen Fischer, R.: Frequenz dissoziiert schlagender Herzabschnitte, Ztschr. f. klin. Med. 116:466, A. M.: Transmission of Excitation Between Excised Jasper, H., and Monnier, Mpelinated Nerves. An Artificial Synapse, J. Cell. & Comp. Physiol. 11:259, Kisch, B.: Beobachtungen bei einem Kranken mit totalem Block, Cardiologia 2:47, de synchronisation au niveau du coeur, Arch. internat. Segers, M . : Les phenomenes Physiol. 54:87, 1946. Van Buchem, F. S. P.: Dissoziation zwischen Atrium und Ventrikel. Erklgrung des tiellen Herzblocks, Ztschr. f. klin. Med. 110:401, 1929.
klin. der 1931. Non1938. 1938. de par.