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The Wenckebach phenomenon in left bundle branch block
Diagnostic Shelf The Wenckebach
Phenomenon
in
Left Bundle Branch Block* H. DAVID FRIEDBERG, M.B., M.R.C.P. (LoNn.)t Milwaukee,
Wisconsin
and LEO SCHAMROTH,M.D., and Johnannesburg,
F.R.C.P.
(EDIN.),
F.A.c.c.~
South Africa
A case is described in wbicb the Wenckebacb phenomenon occurred in the left bundle branch. This manifested as a regularly repeated 3:2 conduction ratio. Successive beats showed normal intraventricular conduction, incomplete left bundle branch block and complete left bundle branch block. This case provides further evidence for the existence of the particular pattern of incomplete left bundle branch block. I
The tracing recorded on November 15 (Fig. 2) shows regular sinus tachycardia (rate 108/ min.). The P-R interval is constant at 20. Intraventricular conduction varies in a regularly recurring manner of groups of three. The sequence is as follows: The First Beat of the Sequence: In each lead of Figure 2 the second and fifth QRS complexes reflect relatively normal intraventricular conduction. The QRS duration is 10. The prominent Q waves in leads II, III and aVF suggest the presence of an old inferior wall myocardial infarction. Small but well defined normal q waves are present in leads V, and V,. The Second Beat of the Sequence: The ensuing beat (the third QRS complex in each lead of Fig. 2) reflects the pactern of incomplete left bundle branch block. The QRS duration is 11. The initial q waves in leads V, and V, have disappeared, and the beginning of the QRS complex in these leads is slurred. All leads reflect a change in the initial QRS forces. There are secondary S-T segment and T wave changes. The Third Beat of the Sequence: The first and fourth beats in each lead of Figure 2 show the typical pattern of complete left bundle
T
HE WENCKEBACH FORM of impaired conduction may occur in any of ‘the conducting tissues of the heart. These include the sinoatria1 junction, the atrioventricular junction, and an ectopic-myocardial junction-the junction between the ectopic focus and the sur-
rounding myocardium. The following is a report of a case in which the Wenckebach phenomenon occurred in the left bundle branch only. ANALYSIS OF ELECTROCARDIOGRAMS The electrocardiograms (Fig. 1 and 2) were obtained from a 46 year old man with carcinoma of the kidney and ischemic heart disease. The tracing recorded on October 30 (Fig. 1) shows sinus rhythm at a rate of lOO/min. The P-R interval measures 16.t Intraventricular conduction is nearly normal. The QRS duration is 9. The tracing recorded the next djay (Fig. 1) shows sinus tachycardima (rate llS/ min.). The P-R interval measures 18. Intraventricular conduction shows the classic abnormality of complete left bundle branch block. The QRS duration is 15.
t All time intervals are expressed in hundredths second.
of a
*From the Cardiovascular Department, Veterans Administration Center, Wood (Milwaukee), Wise., the Marquette School of Medicine, Milwaukee, Wisc.t and the University of the Witwatersrand, Johannesburg, South Africa.: Manuscript received April 9, 1969, accepted June 12, 1969. Address for reprints: H. David Friedberg, M.B., M.R.C.P., Cardiovascular Section, Veterans Administration Center, Wood, Wise. 53193. VOLUME
24,
OCTOBER
1969
591
592
Friedberg
and Scharnroth DISCUSSION
aVF
‘6
Figure 1. Electrocardiograms showing relatively normal intraventricular conduction (October 30) and complete left bundle branch block (October 31).
block. The QRS duration is 17. There are further secondary S-T segment and T wave changes. The pattern is similar to that shown in the tracing of October 31 (Fig. 1). This sequence of intraventricular conduction occurred repeatedly. branch
The traciugs of this man show differing patterns of irrtraventricular conduction. When there is a fast sinus rate (tracing of October 31), there is constant and complete left bundle branch block. When there is a relatively slower sinus rate (tracing of October SO), intraventricular conduction is constant and nearly normal (Fig. 1). At an intermediate rate of lOS/ min. (tracing of November 15) regular variation of intraventricular conduction appears (Fig. 2). This sequence of intraventricular conduction reflects relatively normal intraventricular conduction in the first beat, followed by incomplete left bundle branch block in the second beat, and complete left bundle branch block in the third beat. These changes of QRS-T pattern occur with a strictly regular rhythm, and so cannot be explained on the basis of rate-dependent aberrant vemricular conduction. Furthermore, the constant P-R interval shows that conduction through the A-V node was constant. These changes suggest increasing impairment of conduction through the left bundle branch. The near-normal conduction of the first beat is followed by impaired conduction in the second beat, which in turn is followed by complete block. The block allows recovery of the left bundle branch, and
Figure 2. Electrocardiogram recorded on November phenomenon in left bundle branch block. See text.
15, 1968, showing the Wenckebach
THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Wenckebach the sequence is then repeated. Progressive impairment of conduction with recovery after a blocked impulse is the Wenckebach phenomenon. This tracing, thus, reflects a Wenckebach phenomenon with 3:2 block in the left bundle branch. Tlte existence of incomplete left bundle branch block has long been disputed. Grant1 in 1957 stated that “the proof ‘that a given conduction defect is due to a lesion of the left main bundle in man depends upon demonstrating that the prolongation was sudden in onset and associated with a change in the direction of the initial forces of the QRS interval . . . .” He further stated ‘I. . . so far there have been no cases published of QRS prolongation to only 0.10 to 0.11 sec. of the leftward type with pre-block and post-block tracings to prove that a lesion of the left main bundle was indeed responsible.” Experimentally, however, the existence of incomplete left bundle branch block in the dog had been demonstrated by Sodi-Pallares and associates” and by Rodriguez and Sodi-Pallares. In 1964, Schamroth and Bradlow first described all variations of incomplete left bundle branch block in the human heart. These variations were evident in a case of rate-dependent left bundle branch block, in which transition from normal intraven,tricular conduction to complete left bundle branch block was gradual, passing through all the phases of incomplete left bundle branch block. This case provides further evidence for the existence of incompIete left bundle branch block. Each Wenckebach sequence shows, in turn, normal intraventricular conduction, incomplete left bundle branch block and complete left bundle branch block. There are changes in the initial QRS vector and in the QRS duration of the blocked beats. Grant’s criteria are therefore satisfied. The features of incomplete Zeft bundle branch block, as shown in this case, are a disappearance of the small initial q wave in “left ventricular” leads and replacement by an initial slurring. The QRS complex is slightly prolonged. Note that intraventricular conduction in the tracing of October 30 (Fig. 1) is not quite normal. The q wave is less promi-
VOLUME 24, OCTOBER 1969
593
Phenomenon
nent in lead aVF and is absent in lead Vlj. This probably represents a very small degree of incomplete left bundle branch block. All these findings of incomplete left bundle branch block are in accord with the clinical and experimental criteria previously described.l-~a A Wenckcbach phenomenon confirwd to the left bundle branch is rare. It is thus noteworthy that the variations in conduction in this case can be localized to the left bundle branch, since conditions in other parts of the conducting system were remarkably constant. The sinus rate was strictly regular and the P-R interval was constant. This suggests that the impulses arrived with regularity at the left bundle branch, and that fluctuations in the sinus rate or in A-V nodal conduction, or in both, could not influence the genesis of the Wenckebach phenomenon in this case. The clearest published example of the Wenckebach phenomenon involving the bundle branches is that of Katz and Pick.” In their case, the Wenckebach phenomenon occurred in both branches in differing ratios. In Holzmann’s case,F progressive prolongation of the QRS duration and intensification of the pattern of right bundle branch block complicated an arrhythmia which was probably an A-V junctional tachycardia incompletely dissociated from atria1 fibrillation. So far as can be determined, there has been no previous report of the Wenckebach phenomenon involving the left bulndle branch alone.
REFERENCES 1. GRANT, R. T. Clinical Electrocardiography. p. 126. New York, 1957. McGraw-Hill. 2. SODI-PALLARES.D., ESTANDIA, A., SOEER~N, J. and RODRIGUEZ,M. I. The left intraventricular potential of the human heart. II. Criteria for diagnosis of incomplete bundle branch block. .47n. Heart J., 40:655. 1950. 3. RODRIGUEZ,M. I. and SODI-PALL~RES,D. The mechanism of complete and incomplete bundle branch block. .4m. Heart J., 44:715, 1952. 4. CCHAMROTH, L. and BRADLOW. B. A. Incomplete left bundle branch block. Brit. Heart J., 26:285, 1964. 5. KATZ, L. N. and PICK, A. Clinical Electrocardiography. Part 1: The Arrhythmias, p. 624. Philadelphia, 1956. Lea & Febiger. 6. HOLZMANN,M. Seltene Abarten van unbestindigem Schenkelblock. Cardiologin, 7: 113, 1943.
Phenomenon
in
Left Bundle Branch Block* H. DAVID FRIEDBERG, M.B., M.R.C.P. (LoNn.)t Milwaukee,
Wisconsin
and LEO SCHAMROTH,M.D., and Johnannesburg,
F.R.C.P.
(EDIN.),
F.A.c.c.~
South Africa
A case is described in wbicb the Wenckebacb phenomenon occurred in the left bundle branch. This manifested as a regularly repeated 3:2 conduction ratio. Successive beats showed normal intraventricular conduction, incomplete left bundle branch block and complete left bundle branch block. This case provides further evidence for the existence of the particular pattern of incomplete left bundle branch block. I
The tracing recorded on November 15 (Fig. 2) shows regular sinus tachycardia (rate 108/ min.). The P-R interval is constant at 20. Intraventricular conduction varies in a regularly recurring manner of groups of three. The sequence is as follows: The First Beat of the Sequence: In each lead of Figure 2 the second and fifth QRS complexes reflect relatively normal intraventricular conduction. The QRS duration is 10. The prominent Q waves in leads II, III and aVF suggest the presence of an old inferior wall myocardial infarction. Small but well defined normal q waves are present in leads V, and V,. The Second Beat of the Sequence: The ensuing beat (the third QRS complex in each lead of Fig. 2) reflects the pactern of incomplete left bundle branch block. The QRS duration is 11. The initial q waves in leads V, and V, have disappeared, and the beginning of the QRS complex in these leads is slurred. All leads reflect a change in the initial QRS forces. There are secondary S-T segment and T wave changes. The Third Beat of the Sequence: The first and fourth beats in each lead of Figure 2 show the typical pattern of complete left bundle
T
HE WENCKEBACH FORM of impaired conduction may occur in any of ‘the conducting tissues of the heart. These include the sinoatria1 junction, the atrioventricular junction, and an ectopic-myocardial junction-the junction between the ectopic focus and the sur-
rounding myocardium. The following is a report of a case in which the Wenckebach phenomenon occurred in the left bundle branch only. ANALYSIS OF ELECTROCARDIOGRAMS The electrocardiograms (Fig. 1 and 2) were obtained from a 46 year old man with carcinoma of the kidney and ischemic heart disease. The tracing recorded on October 30 (Fig. 1) shows sinus rhythm at a rate of lOO/min. The P-R interval measures 16.t Intraventricular conduction is nearly normal. The QRS duration is 9. The tracing recorded the next djay (Fig. 1) shows sinus tachycardima (rate llS/ min.). The P-R interval measures 18. Intraventricular conduction shows the classic abnormality of complete left bundle branch block. The QRS duration is 15.
t All time intervals are expressed in hundredths second.
of a
*From the Cardiovascular Department, Veterans Administration Center, Wood (Milwaukee), Wise., the Marquette School of Medicine, Milwaukee, Wisc.t and the University of the Witwatersrand, Johannesburg, South Africa.: Manuscript received April 9, 1969, accepted June 12, 1969. Address for reprints: H. David Friedberg, M.B., M.R.C.P., Cardiovascular Section, Veterans Administration Center, Wood, Wise. 53193. VOLUME
24,
OCTOBER
1969
591
592
Friedberg
and Scharnroth DISCUSSION
aVF
‘6
Figure 1. Electrocardiograms showing relatively normal intraventricular conduction (October 30) and complete left bundle branch block (October 31).
block. The QRS duration is 17. There are further secondary S-T segment and T wave changes. The pattern is similar to that shown in the tracing of October 31 (Fig. 1). This sequence of intraventricular conduction occurred repeatedly. branch
The traciugs of this man show differing patterns of irrtraventricular conduction. When there is a fast sinus rate (tracing of October 31), there is constant and complete left bundle branch block. When there is a relatively slower sinus rate (tracing of October SO), intraventricular conduction is constant and nearly normal (Fig. 1). At an intermediate rate of lOS/ min. (tracing of November 15) regular variation of intraventricular conduction appears (Fig. 2). This sequence of intraventricular conduction reflects relatively normal intraventricular conduction in the first beat, followed by incomplete left bundle branch block in the second beat, and complete left bundle branch block in the third beat. These changes of QRS-T pattern occur with a strictly regular rhythm, and so cannot be explained on the basis of rate-dependent aberrant vemricular conduction. Furthermore, the constant P-R interval shows that conduction through the A-V node was constant. These changes suggest increasing impairment of conduction through the left bundle branch. The near-normal conduction of the first beat is followed by impaired conduction in the second beat, which in turn is followed by complete block. The block allows recovery of the left bundle branch, and
Figure 2. Electrocardiogram recorded on November phenomenon in left bundle branch block. See text.
15, 1968, showing the Wenckebach
THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Wenckebach the sequence is then repeated. Progressive impairment of conduction with recovery after a blocked impulse is the Wenckebach phenomenon. This tracing, thus, reflects a Wenckebach phenomenon with 3:2 block in the left bundle branch. Tlte existence of incomplete left bundle branch block has long been disputed. Grant1 in 1957 stated that “the proof ‘that a given conduction defect is due to a lesion of the left main bundle in man depends upon demonstrating that the prolongation was sudden in onset and associated with a change in the direction of the initial forces of the QRS interval . . . .” He further stated ‘I. . . so far there have been no cases published of QRS prolongation to only 0.10 to 0.11 sec. of the leftward type with pre-block and post-block tracings to prove that a lesion of the left main bundle was indeed responsible.” Experimentally, however, the existence of incomplete left bundle branch block in the dog had been demonstrated by Sodi-Pallares and associates” and by Rodriguez and Sodi-Pallares. In 1964, Schamroth and Bradlow first described all variations of incomplete left bundle branch block in the human heart. These variations were evident in a case of rate-dependent left bundle branch block, in which transition from normal intraven,tricular conduction to complete left bundle branch block was gradual, passing through all the phases of incomplete left bundle branch block. This case provides further evidence for the existence of incompIete left bundle branch block. Each Wenckebach sequence shows, in turn, normal intraventricular conduction, incomplete left bundle branch block and complete left bundle branch block. There are changes in the initial QRS vector and in the QRS duration of the blocked beats. Grant’s criteria are therefore satisfied. The features of incomplete Zeft bundle branch block, as shown in this case, are a disappearance of the small initial q wave in “left ventricular” leads and replacement by an initial slurring. The QRS complex is slightly prolonged. Note that intraventricular conduction in the tracing of October 30 (Fig. 1) is not quite normal. The q wave is less promi-
VOLUME 24, OCTOBER 1969
593
Phenomenon
nent in lead aVF and is absent in lead Vlj. This probably represents a very small degree of incomplete left bundle branch block. All these findings of incomplete left bundle branch block are in accord with the clinical and experimental criteria previously described.l-~a A Wenckcbach phenomenon confirwd to the left bundle branch is rare. It is thus noteworthy that the variations in conduction in this case can be localized to the left bundle branch, since conditions in other parts of the conducting system were remarkably constant. The sinus rate was strictly regular and the P-R interval was constant. This suggests that the impulses arrived with regularity at the left bundle branch, and that fluctuations in the sinus rate or in A-V nodal conduction, or in both, could not influence the genesis of the Wenckebach phenomenon in this case. The clearest published example of the Wenckebach phenomenon involving the bundle branches is that of Katz and Pick.” In their case, the Wenckebach phenomenon occurred in both branches in differing ratios. In Holzmann’s case,F progressive prolongation of the QRS duration and intensification of the pattern of right bundle branch block complicated an arrhythmia which was probably an A-V junctional tachycardia incompletely dissociated from atria1 fibrillation. So far as can be determined, there has been no previous report of the Wenckebach phenomenon involving the left bulndle branch alone.
REFERENCES 1. GRANT, R. T. Clinical Electrocardiography. p. 126. New York, 1957. McGraw-Hill. 2. SODI-PALLARES.D., ESTANDIA, A., SOEER~N, J. and RODRIGUEZ,M. I. The left intraventricular potential of the human heart. II. Criteria for diagnosis of incomplete bundle branch block. .47n. Heart J., 40:655. 1950. 3. RODRIGUEZ,M. I. and SODI-PALL~RES,D. The mechanism of complete and incomplete bundle branch block. .4m. Heart J., 44:715, 1952. 4. CCHAMROTH, L. and BRADLOW. B. A. Incomplete left bundle branch block. Brit. Heart J., 26:285, 1964. 5. KATZ, L. N. and PICK, A. Clinical Electrocardiography. Part 1: The Arrhythmias, p. 624. Philadelphia, 1956. Lea & Febiger. 6. HOLZMANN,M. Seltene Abarten van unbestindigem Schenkelblock. Cardiologin, 7: 113, 1943.