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Triple Ventricular Fusion in Wolff-Parkinson-White Pattern
electrocardiogram of the month
Triple Ventricular Fusion in WoIH-Parkinson-White Pattern* D. P. Myburgh, M.B., Ch.B.; J. Cartoon, M.B., B.Ch.; and
J. M. Schamroth, M.B., B.Ch.
T he
classic form of conduction in the WolffParkinson-White syndrome is reflected by a typical preexcitation fusion complex. The supraventricular front is conducted down both the anomalous pathway (Kent bundle) and the normal atrioventricular nodal pathway. The front is conducted without delay through the Kent bundle, and hence the very short P-R interval; however, on reaching the ventricle, further onward conduction is through ordinary myocardial tissue, a poor conducting medium. Conduction is thus slow and bizarre and is reflected by the delta wave. That part of the activation front which is conducted through the normal atrioventricular nodal pathway is subject to the normal atrioventricular nodal delay and, upon reaching the ventricles, is conducted through the highly efficient intraventricular conducting system of the bundle of His, the bundle "From the Department of Cardiology, Military Medical Institute, Verwoerdburg, Republic of South Africa. Reprint requests: Dr. Myburgh, Department of Cardiology, Military Medical Institute, Verwoerdburg, Republic of South Africa
branches, and Purkinje's fibers. This activation front thus completes ventricular activation in a rapid and coordinated manner, and hence the normal terminal part of the QRS complex. The typical preexcitation complex is thus, in effect, a fusion complex resulting from activation fronts which are conducted through two atrioventricular pathways, and each of the so divided fronts contribute to partial activation of the ventricles. The following presentation reflects a classic preexcitation fusion complex which is further modified by fusion from a coincidental ectopic ventricular escape pacemaker. CASE REPoRT
The electrocardiogram (Fig 1) is a continuous strip of a modified lead V6' recorded by continuous (Holter) monitoring from a 19-year-old male marathon runner . It shows the following five features: First, there is sinus bradycardia with marked sinus arrhythmia. The R-R intervals range from 1.01 to lAO second (not shown), representing a range for rate of 59 to 43 beats per minute. Secondly, there is Wolfl-Parkinson-White conduction. The
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CHEST, 77: 3, MARCH, 1980
TRIPLE VENTRICULAR FUSION IN WPW PATIERN 421
conducted sinus impulses are associated with Wolff-Parkinson-White conduction. This is exemplified by the first two beats in the upper and lower strips and is reflected by a short peR interval of 0.06 second and a delta wave which begins before the terminal part of the P wave has been completely inscribed. A type-A Wolff-Parkinson-White pattern was present on the 12-lead ECG. Thirdly, there is incomplete right bundle-branch block. This is reflected in the conducted sinus beats by a QRS width of 0.11 second (ie, excluding the delta wave) and a wide S wave in lead V6. Fourthly, ventricular escape beats are present. The bradycardiac phases of sinus arrhythmia are associated with venbicular escape beats, as reflected by the bizarre and widened QRS complexesresembling left bundle-branch block. The escape cycle is 1.26 second, representing a rate of 47 beats per minute. The escape rhythm is dissipated during the relatively faster phases of the sinus arrhythmia, as seen, for example, at the end of the middle strip (Fig 1). The configuration of the escape beat is modified by varying degrees of ventricular fusion. Fifthly, there is ventricular fusion. Since the ventricular escape beat has a configuration resembling left bundlebranch block, the ectopic focus giving rise to this escape beat is presumably located in the right ventricle. As noted previously, the conducted sinus impulse is associated with incomplete right bundle-branch block. Thus, when the sinus and ectopic ventricular impulses invade the ventricles synchronously and fortuitously, the ectopic activation &ont will complete venbicular activation distal to the block. This will thereby tend to normalize the QRS complex. Almost complete normalization of the terminal part of the
422 MYBURGH, CARTOON, SCHAIROTH
QRS complex is evident in the third and fourth beats of the middle strip (Fig 1). Varying degrees of normalization are evident in the fifth beat in the upper strip and the fourth beat in the lower strip (Fig 1). The "pure" ectopic beat is represented by the last beat in the top strip and the third beat in the lower strip, as reflected by the very tall and wide QRS complexes and by the depression and depth of the associated S-T segment and T wave. All of the other bizarre complexes show minor degrees of ventricular fusion, at times only evident by a shallower S-T segment and T wave as, for example, the third beat in the top strip and the second beat in the middle strip (Fig 1). DISCUSSION
This tracing (Fig 1) thus reflects the unusual feature of a triple fusion: the classic fusion of two pacemakers simultaneously invading the ventricles and, in this case, normalizing the complex by virtue of a fortuitous coincidental right bundle-branch block in association with a right ventricular ectopic pacemaker. This is further complicated by the classic form of Wolff-Parkinson-White fusion. An analogous example in association with a ventricular parasystolic pacemaker was reported by Dubb and Schamroth.' REFERENCE 1 Dubb A, Schamroth L. Ventricular parasystole with the Wolff-Parkinson-White syndrome. Chest 1979; 75:607-8.
CHEST, 77: 3, MARCH, 1980
Triple Ventricular Fusion in WoIH-Parkinson-White Pattern* D. P. Myburgh, M.B., Ch.B.; J. Cartoon, M.B., B.Ch.; and
J. M. Schamroth, M.B., B.Ch.
T he
classic form of conduction in the WolffParkinson-White syndrome is reflected by a typical preexcitation fusion complex. The supraventricular front is conducted down both the anomalous pathway (Kent bundle) and the normal atrioventricular nodal pathway. The front is conducted without delay through the Kent bundle, and hence the very short P-R interval; however, on reaching the ventricle, further onward conduction is through ordinary myocardial tissue, a poor conducting medium. Conduction is thus slow and bizarre and is reflected by the delta wave. That part of the activation front which is conducted through the normal atrioventricular nodal pathway is subject to the normal atrioventricular nodal delay and, upon reaching the ventricles, is conducted through the highly efficient intraventricular conducting system of the bundle of His, the bundle "From the Department of Cardiology, Military Medical Institute, Verwoerdburg, Republic of South Africa. Reprint requests: Dr. Myburgh, Department of Cardiology, Military Medical Institute, Verwoerdburg, Republic of South Africa
branches, and Purkinje's fibers. This activation front thus completes ventricular activation in a rapid and coordinated manner, and hence the normal terminal part of the QRS complex. The typical preexcitation complex is thus, in effect, a fusion complex resulting from activation fronts which are conducted through two atrioventricular pathways, and each of the so divided fronts contribute to partial activation of the ventricles. The following presentation reflects a classic preexcitation fusion complex which is further modified by fusion from a coincidental ectopic ventricular escape pacemaker. CASE REPoRT
The electrocardiogram (Fig 1) is a continuous strip of a modified lead V6' recorded by continuous (Holter) monitoring from a 19-year-old male marathon runner . It shows the following five features: First, there is sinus bradycardia with marked sinus arrhythmia. The R-R intervals range from 1.01 to lAO second (not shown), representing a range for rate of 59 to 43 beats per minute. Secondly, there is Wolfl-Parkinson-White conduction. The
)~
-
I 'L ...._ .--I ./1 W
l...._ _
~rJ.
\.
J ,)
I \,-_ _
~
L-J ;
.J FIGURE 1. Continuous recording of modified lead VG'
CHEST, 77: 3, MARCH, 1980
TRIPLE VENTRICULAR FUSION IN WPW PATIERN 421
conducted sinus impulses are associated with Wolff-Parkinson-White conduction. This is exemplified by the first two beats in the upper and lower strips and is reflected by a short peR interval of 0.06 second and a delta wave which begins before the terminal part of the P wave has been completely inscribed. A type-A Wolff-Parkinson-White pattern was present on the 12-lead ECG. Thirdly, there is incomplete right bundle-branch block. This is reflected in the conducted sinus beats by a QRS width of 0.11 second (ie, excluding the delta wave) and a wide S wave in lead V6. Fourthly, ventricular escape beats are present. The bradycardiac phases of sinus arrhythmia are associated with venbicular escape beats, as reflected by the bizarre and widened QRS complexesresembling left bundle-branch block. The escape cycle is 1.26 second, representing a rate of 47 beats per minute. The escape rhythm is dissipated during the relatively faster phases of the sinus arrhythmia, as seen, for example, at the end of the middle strip (Fig 1). The configuration of the escape beat is modified by varying degrees of ventricular fusion. Fifthly, there is ventricular fusion. Since the ventricular escape beat has a configuration resembling left bundlebranch block, the ectopic focus giving rise to this escape beat is presumably located in the right ventricle. As noted previously, the conducted sinus impulse is associated with incomplete right bundle-branch block. Thus, when the sinus and ectopic ventricular impulses invade the ventricles synchronously and fortuitously, the ectopic activation &ont will complete venbicular activation distal to the block. This will thereby tend to normalize the QRS complex. Almost complete normalization of the terminal part of the
422 MYBURGH, CARTOON, SCHAIROTH
QRS complex is evident in the third and fourth beats of the middle strip (Fig 1). Varying degrees of normalization are evident in the fifth beat in the upper strip and the fourth beat in the lower strip (Fig 1). The "pure" ectopic beat is represented by the last beat in the top strip and the third beat in the lower strip, as reflected by the very tall and wide QRS complexes and by the depression and depth of the associated S-T segment and T wave. All of the other bizarre complexes show minor degrees of ventricular fusion, at times only evident by a shallower S-T segment and T wave as, for example, the third beat in the top strip and the second beat in the middle strip (Fig 1). DISCUSSION
This tracing (Fig 1) thus reflects the unusual feature of a triple fusion: the classic fusion of two pacemakers simultaneously invading the ventricles and, in this case, normalizing the complex by virtue of a fortuitous coincidental right bundle-branch block in association with a right ventricular ectopic pacemaker. This is further complicated by the classic form of Wolff-Parkinson-White fusion. An analogous example in association with a ventricular parasystolic pacemaker was reported by Dubb and Schamroth.' REFERENCE 1 Dubb A, Schamroth L. Ventricular parasystole with the Wolff-Parkinson-White syndrome. Chest 1979; 75:607-8.
CHEST, 77: 3, MARCH, 1980