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The Wenckebach phenomenon
The Journal of Emergency Medione, Vol 4, pp. 115-I 18. 1986
PrInted tn the USA
THE WENCKEBACH Gregg J. Fromell,
MD,
l
CopyrIght 0 1986 Pergamon Journals Ltd
PHENOMENON
Jonathan Root,
MD,
Robert Barish,
MD
Emergency Department, Urwersity of Maryland Hospital, Unwerslty of Maryland School of Medicine, Baltimore, MD 21201 Reprint address
Robert Barlsh, MD, Director, Emergency Medlclne, Unwerslty of Maryland 22 S. Greene Street, Baltimore. MD 21201
In 1906 similar observations of the jugular venous pulse led Wenckebach to the discovery of dropped beats preceded by a constant A wave-V wave interval. This same observation was made simultaneously and independently by Hay.3 Eighteen years later, after the development of the ECG machine, Mobitz classified these two types of AV block into types I and II, respectively.4
0 Abstract-The Wenckebach phenomenon, or type I AV block, refers to a progressive lengthening of impulse conduction time, followed by a nonconducted impulse, or dropped beat. It can occur in a variety of pathologic settings, especially inferior myocardial infarction. Although a temporary pacemaker may be required, full spontaneous recovery is the rule. 0 Keywords-heart block; Wenckebach; AV block; atrioventricular block; Mobitz type I AV block; conduction delay; myocardial infarction
Characteristics and Morphology
Definition
The Wenckebach phenomenon is a specific type of conduction abnormality involving impulse conduction from one area of the heart to another and therefore can involve any level of the conduction system. Although classically this phenomenon is described involving the AV node (type I AV block), the Wenckebach phenomenon can also involve the sinoatrial (SA) node, the His bundle, or the right bundle or left bundle of the cardiac conduction system.+8 This conduction block has also been reported during ventricular bigeminy with coupling interval prolongation.9 This dis-
The Wenckebach phenomenon, when it occurs in the atrioventricular (AV) node, is defined as intermittent failure of AV conduction marked by progressive lengthening of AV conduction time.’ This is manifested on the surface ECG by progressive lengthening of the PR interval followed by a nonconducted atria1 impulse. Wenckebach first observed this phenomenon in 1899, prior to the advent of the ECG machine, by studying jugular venous pulse tracings. He noted that a dropped beat was preceded by progressive prolongation of the interval between atria1 and ventricular contraction.* ECG Commentary, electrocardiographic
w
Hospital.
cussion is confined of the Wenckebach
to the general attributes phenomenon and spe-
a section devoted to review of the pattern recognition abnormalities,
is coordinated
by Ron Wds,
of selected MD, George Wash-
ington University.
RECEIVED: 24
February 1986; ACCEPTED: 27 February 1986 0736-4679/86 $3.00 + .OO 115
116
cific ECG findings when the block occurs at the AV node. The features of the Wenckebach phenomenon are well summarized by Cabeen et al6 and are as follows: 1. Progressive conduction delay from a proximal area, across a pathway, to a distal activation area. In AV Wenckebath, the proximal area is the atrium, and the conduction delay is manifested on the surface ECG by progressive PR prolongation with eventual failure of conduction, resulting in a dropped beat (Figure 1). 2. Progressive decrease in the increment of the conduction delay through the cycle leading up to the dropped beat. The amount by which the PR interval of each beat exceeds that of the preceding beat becomes less and less until total conduction failure occurs (Figure 1). 3. Progressive shortening of the activation interval. In AV Wenckebach, this is manifested by progressive shortening of the R-R interval. This phenomenon is a direct result of feature 2. Although the RR interval remains longer than the P-P interval, the additional delay of the R wave is less and less, resulting in shorter and shorter activation (R-R) intervals. 4. The pause after a dropped beat is less than twice the cycle length of the preceding proximal (P-P) or distal (R-R) interval.
Differential Diagnosis The differentiation of type I (Wenckebach) AV block from type II AV block is critical, since the latter often progresses to complete heart block, necessitating pacemaker placement.‘O,” ECG differentiation can be difficult in the context of second degree AV block with 2: 1 conduction. This is manifested by a fixed, prolonged PR interval with every other P wave failing to be conducted. The correct diagnosis can be made if areas of the ECG show typical Wenckebath block with 3 :2 or 4: 3 conduction
Gregg J. Fromell, Jonathan
Root, Robert Barish
prior to the development of 2: 1 block. A further aid is that inferior myocardial infarction (MI) is more commonly associated with Wenckebach AV block, whereas anterior MI is more commonly associated with type II AV block.lO,ll However, type II AV block can be seen in either setting. Wenckebach AV block can also be misdiagnosed as type II block in the setting of long cycles with many beats prior to the dropped beat. In this instance, the PR interval increment may be so small as to give the appearance of a constant PR interval. Careful measurement of the PR interval prior to the dropped beat will show it to be longer than the PR interval directly following the pause1 (Figure 2).
Significance Although Wenckebach AV block is associated with a number of conditions12-16(Table l), it is most commonly seen in the setting of acute inferior myocardial infarction.17,18 In this setting, Wenckebach block is usually a manifestation of transient AV nodal ischemia,” rarely requires intervention, and usually resolves rather than progressing to higher degree block. Wenckebach AV block is uncommon in the general population. However, it occurs with some frequency in young athletes and physically active middle-aged persons.” In asymptomatic athletes it is presumed to be a benign, vagus-nerve-mediated feature of the athlete’s heart. This does not require aggressive cardiac investigation, provided the patient is asymptomatic, has no cardiac pathology on ECG and echocardiogram, and demonstrates normalization of the conduction disturbance with sympathetic maneuvers (such as exercise or sympathomimetic/vagolytic drugs). l2
Treatment AV-nodal Wenckebach rarely requires treatment and usually resolves. However, when occurring in the context of acute inferior
Wenckebach
117
Phenomenon
I
A
1 108 I
AV
\1e
V
1
1
108
I
24.
116
I
1
108
I
28
112
I
1
I
108 30
110
1
I
\
200
108
I
108
I
\
“‘“I,,,,
1 I \
1
116
108
I
1 L \
112
Figure 1. ECG strip of AV node Wenckebach block, with ladder diagram. At the atrial level (A) note the constant cycle length. The atrioventrlcular level (AV) shows the progressive AV conduction delay with a decrease in increment of delay. The ventricular level (V) shows the decrease in ventricular cycle length with a pause that is less than twice the cycle length of either the atrial level or the ventricular level.
Figure 2. Mobitz type I AV block with a long cycle leading to the dropped beat. Although the PR interval appears almost constant during the last few beats before the dropped beat, the PR interval of the first beat following the pause is clearly shorter than that of the last beat preceding the pause.
118
Gregg J. Fromell, Jonathan Root, Robert Barish
Table 1. Causes of Wenckebach Acute myocardial infarction Increased vagal tone Rapid atrial pacing Digoxin intoxication Hyperkalemia Paroxysmal supraventricular Mitral commissurotomy Athlete’s heart
AV Block
-
Permanent pacing after recovery from heart block and inferior myocardial infarction (MI) is rarely needed.‘O,” Summary
tachycardia
Morphology:
myocardial infarction, temporary transvenous pacing may be indicated in the following circumstances.1o 1. Congestive heart failure 2. Signs of cardiogenic shock 3. Hemodynamically significant slow ventricular rate (< 50) 4. Persistent or recurring angina 5. Ventricular irritability
Gradually increasing PR interval followed by nonconducted P wave. R-R interval decreases prior to dropped beat. Pause after dropped beat is less than 2 times the preceding P-P interval or the following R-R interval. Differential diagnosis: May be confused with Mobitz II AV block when block is 2 : 1. Wenckebach more common with inferior MI. Look for varying degree of block. Significance: Usually seen with acute inferior MI. See also Table 1. Treatment: Consider pacemaker if acute inferior MI with congestive heart failure, cardiogenic shock, bradycardia, angina, or ventricular ectopy.
REFERENCES 1. El-Sharif N, Aranda J, Befeler B, et al: Atypical Wenckebach periodicity simulating Mobitz II AV block. Br Heart J 1978; 40:1376. 2. Wenckebach KF: Zur Analyse des umegelmassigen pulses. Z Klin Med 1899; 37~475. 3. Wenckebach KF: Bietrage zur kenntnis der mens&lichen Herztatigkeit. Arch Anat Physiol (Physiol Abt) 1906, 297. 4. Hay J: Bradycardia and cardia arrhythmia produced by depression of certain functions of the heart. Lancer 1906; 1:139. 5. Cabeen WR Jr, Roberts NK, Child JS: Recognition of the Wenckebach phenomenon. West JMed 1978; 129:521. 6. Carli AJ, Schrader DD, Suarez JE, et al: Concealed Wenckebach phenomenon in 3 : 1 AV block, conduction disturbances in the His bundle. Chest 1983; 84:96. 7. Niremberg V, Dubb A, Schamroth L: Right bundle branch block with Wenckebach conduction. Heart Lyng 1978; 8:136. 8. Izumi K: Direct Wenckebach periods in the left bundle branch during bradycardia-dependent left bundle branch block in a patient with sick sinus syndrome. J Electrocardiol 1980; 13~291. 9. Parasystole simulating ventricular bigeminy with Wenckebach-type coupling prolongation. J Electrocardiol 1978; 11:385. 10. Kastor JA: Atrioventricular block. NEngl Jh4ed 1975; 292~462.
11. Kastor JA: Atrioventricular block. NEnglJMed 1975; 292~572. 12. Zeppilli P, Fenici R, Sassara M, et al: Wenckebach second degree atrioventricular block in top-ranking athletes: an old problem revisited. Am Heart J 1980; 100:281. 13. Amat-y-Leon F, Chuquimia R, Wu D: Alternating Wenckebach periodicity: a common electrophysiologic response. Am J Cardiol 1975; 36~757. 14. Castellanos A, Sung RJ, Myerburg RJ: His bundle electrocardiography in digitais-induced “atrioventricular junctional: Wenckebach periods with irregular H-H intevals. Am JCardioll979; 43:653. 15. Schweitzer P, Choudhry M, Kunkis SH, et al: Extra AV nodal Wenckebach periodicity. J Electrocardiol 1981; 14:225. 16. DiMarco J, Sellers TD, Belardinelli L: Paroxysmal supraventricular tachycardia with Wenckebach block: evidence for reentry within the upper portion of the atrioventricular node. JACC 1984; 3:1551. 17. Vasudevan G, Brostoff P, Varat MA: Alternating Wenckebach periods with acute myocardial infarction. Chest 1979; 75~197. 18. Langendorf R, Pick A: Atrioventricular block, type II (Mobitz) - its nature and clinical significance. Circulation 1968; 38:819. 19. Braunwald E: Heart D&ewe-A Textbook of Cardiovascular Medicine WB Saunders Company, 1984, Vol 2, p 1287.
PrInted tn the USA
THE WENCKEBACH Gregg J. Fromell,
MD,
l
CopyrIght 0 1986 Pergamon Journals Ltd
PHENOMENON
Jonathan Root,
MD,
Robert Barish,
MD
Emergency Department, Urwersity of Maryland Hospital, Unwerslty of Maryland School of Medicine, Baltimore, MD 21201 Reprint address
Robert Barlsh, MD, Director, Emergency Medlclne, Unwerslty of Maryland 22 S. Greene Street, Baltimore. MD 21201
In 1906 similar observations of the jugular venous pulse led Wenckebach to the discovery of dropped beats preceded by a constant A wave-V wave interval. This same observation was made simultaneously and independently by Hay.3 Eighteen years later, after the development of the ECG machine, Mobitz classified these two types of AV block into types I and II, respectively.4
0 Abstract-The Wenckebach phenomenon, or type I AV block, refers to a progressive lengthening of impulse conduction time, followed by a nonconducted impulse, or dropped beat. It can occur in a variety of pathologic settings, especially inferior myocardial infarction. Although a temporary pacemaker may be required, full spontaneous recovery is the rule. 0 Keywords-heart block; Wenckebach; AV block; atrioventricular block; Mobitz type I AV block; conduction delay; myocardial infarction
Characteristics and Morphology
Definition
The Wenckebach phenomenon is a specific type of conduction abnormality involving impulse conduction from one area of the heart to another and therefore can involve any level of the conduction system. Although classically this phenomenon is described involving the AV node (type I AV block), the Wenckebach phenomenon can also involve the sinoatrial (SA) node, the His bundle, or the right bundle or left bundle of the cardiac conduction system.+8 This conduction block has also been reported during ventricular bigeminy with coupling interval prolongation.9 This dis-
The Wenckebach phenomenon, when it occurs in the atrioventricular (AV) node, is defined as intermittent failure of AV conduction marked by progressive lengthening of AV conduction time.’ This is manifested on the surface ECG by progressive lengthening of the PR interval followed by a nonconducted atria1 impulse. Wenckebach first observed this phenomenon in 1899, prior to the advent of the ECG machine, by studying jugular venous pulse tracings. He noted that a dropped beat was preceded by progressive prolongation of the interval between atria1 and ventricular contraction.* ECG Commentary, electrocardiographic
w
Hospital.
cussion is confined of the Wenckebach
to the general attributes phenomenon and spe-
a section devoted to review of the pattern recognition abnormalities,
is coordinated
by Ron Wds,
of selected MD, George Wash-
ington University.
RECEIVED: 24
February 1986; ACCEPTED: 27 February 1986 0736-4679/86 $3.00 + .OO 115
116
cific ECG findings when the block occurs at the AV node. The features of the Wenckebach phenomenon are well summarized by Cabeen et al6 and are as follows: 1. Progressive conduction delay from a proximal area, across a pathway, to a distal activation area. In AV Wenckebath, the proximal area is the atrium, and the conduction delay is manifested on the surface ECG by progressive PR prolongation with eventual failure of conduction, resulting in a dropped beat (Figure 1). 2. Progressive decrease in the increment of the conduction delay through the cycle leading up to the dropped beat. The amount by which the PR interval of each beat exceeds that of the preceding beat becomes less and less until total conduction failure occurs (Figure 1). 3. Progressive shortening of the activation interval. In AV Wenckebach, this is manifested by progressive shortening of the R-R interval. This phenomenon is a direct result of feature 2. Although the RR interval remains longer than the P-P interval, the additional delay of the R wave is less and less, resulting in shorter and shorter activation (R-R) intervals. 4. The pause after a dropped beat is less than twice the cycle length of the preceding proximal (P-P) or distal (R-R) interval.
Differential Diagnosis The differentiation of type I (Wenckebach) AV block from type II AV block is critical, since the latter often progresses to complete heart block, necessitating pacemaker placement.‘O,” ECG differentiation can be difficult in the context of second degree AV block with 2: 1 conduction. This is manifested by a fixed, prolonged PR interval with every other P wave failing to be conducted. The correct diagnosis can be made if areas of the ECG show typical Wenckebath block with 3 :2 or 4: 3 conduction
Gregg J. Fromell, Jonathan
Root, Robert Barish
prior to the development of 2: 1 block. A further aid is that inferior myocardial infarction (MI) is more commonly associated with Wenckebach AV block, whereas anterior MI is more commonly associated with type II AV block.lO,ll However, type II AV block can be seen in either setting. Wenckebach AV block can also be misdiagnosed as type II block in the setting of long cycles with many beats prior to the dropped beat. In this instance, the PR interval increment may be so small as to give the appearance of a constant PR interval. Careful measurement of the PR interval prior to the dropped beat will show it to be longer than the PR interval directly following the pause1 (Figure 2).
Significance Although Wenckebach AV block is associated with a number of conditions12-16(Table l), it is most commonly seen in the setting of acute inferior myocardial infarction.17,18 In this setting, Wenckebach block is usually a manifestation of transient AV nodal ischemia,” rarely requires intervention, and usually resolves rather than progressing to higher degree block. Wenckebach AV block is uncommon in the general population. However, it occurs with some frequency in young athletes and physically active middle-aged persons.” In asymptomatic athletes it is presumed to be a benign, vagus-nerve-mediated feature of the athlete’s heart. This does not require aggressive cardiac investigation, provided the patient is asymptomatic, has no cardiac pathology on ECG and echocardiogram, and demonstrates normalization of the conduction disturbance with sympathetic maneuvers (such as exercise or sympathomimetic/vagolytic drugs). l2
Treatment AV-nodal Wenckebach rarely requires treatment and usually resolves. However, when occurring in the context of acute inferior
Wenckebach
117
Phenomenon
I
A
1 108 I
AV
\1e
V
1
1
108
I
24.
116
I
1
108
I
28
112
I
1
I
108 30
110
1
I
\
200
108
I
108
I
\
“‘“I,,,,
1 I \
1
116
108
I
1 L \
112
Figure 1. ECG strip of AV node Wenckebach block, with ladder diagram. At the atrial level (A) note the constant cycle length. The atrioventrlcular level (AV) shows the progressive AV conduction delay with a decrease in increment of delay. The ventricular level (V) shows the decrease in ventricular cycle length with a pause that is less than twice the cycle length of either the atrial level or the ventricular level.
Figure 2. Mobitz type I AV block with a long cycle leading to the dropped beat. Although the PR interval appears almost constant during the last few beats before the dropped beat, the PR interval of the first beat following the pause is clearly shorter than that of the last beat preceding the pause.
118
Gregg J. Fromell, Jonathan Root, Robert Barish
Table 1. Causes of Wenckebach Acute myocardial infarction Increased vagal tone Rapid atrial pacing Digoxin intoxication Hyperkalemia Paroxysmal supraventricular Mitral commissurotomy Athlete’s heart
AV Block
-
Permanent pacing after recovery from heart block and inferior myocardial infarction (MI) is rarely needed.‘O,” Summary
tachycardia
Morphology:
myocardial infarction, temporary transvenous pacing may be indicated in the following circumstances.1o 1. Congestive heart failure 2. Signs of cardiogenic shock 3. Hemodynamically significant slow ventricular rate (< 50) 4. Persistent or recurring angina 5. Ventricular irritability
Gradually increasing PR interval followed by nonconducted P wave. R-R interval decreases prior to dropped beat. Pause after dropped beat is less than 2 times the preceding P-P interval or the following R-R interval. Differential diagnosis: May be confused with Mobitz II AV block when block is 2 : 1. Wenckebach more common with inferior MI. Look for varying degree of block. Significance: Usually seen with acute inferior MI. See also Table 1. Treatment: Consider pacemaker if acute inferior MI with congestive heart failure, cardiogenic shock, bradycardia, angina, or ventricular ectopy.
REFERENCES 1. El-Sharif N, Aranda J, Befeler B, et al: Atypical Wenckebach periodicity simulating Mobitz II AV block. Br Heart J 1978; 40:1376. 2. Wenckebach KF: Zur Analyse des umegelmassigen pulses. Z Klin Med 1899; 37~475. 3. Wenckebach KF: Bietrage zur kenntnis der mens&lichen Herztatigkeit. Arch Anat Physiol (Physiol Abt) 1906, 297. 4. Hay J: Bradycardia and cardia arrhythmia produced by depression of certain functions of the heart. Lancer 1906; 1:139. 5. Cabeen WR Jr, Roberts NK, Child JS: Recognition of the Wenckebach phenomenon. West JMed 1978; 129:521. 6. Carli AJ, Schrader DD, Suarez JE, et al: Concealed Wenckebach phenomenon in 3 : 1 AV block, conduction disturbances in the His bundle. Chest 1983; 84:96. 7. Niremberg V, Dubb A, Schamroth L: Right bundle branch block with Wenckebach conduction. Heart Lyng 1978; 8:136. 8. Izumi K: Direct Wenckebach periods in the left bundle branch during bradycardia-dependent left bundle branch block in a patient with sick sinus syndrome. J Electrocardiol 1980; 13~291. 9. Parasystole simulating ventricular bigeminy with Wenckebach-type coupling prolongation. J Electrocardiol 1978; 11:385. 10. Kastor JA: Atrioventricular block. NEngl Jh4ed 1975; 292~462.
11. Kastor JA: Atrioventricular block. NEnglJMed 1975; 292~572. 12. Zeppilli P, Fenici R, Sassara M, et al: Wenckebach second degree atrioventricular block in top-ranking athletes: an old problem revisited. Am Heart J 1980; 100:281. 13. Amat-y-Leon F, Chuquimia R, Wu D: Alternating Wenckebach periodicity: a common electrophysiologic response. Am J Cardiol 1975; 36~757. 14. Castellanos A, Sung RJ, Myerburg RJ: His bundle electrocardiography in digitais-induced “atrioventricular junctional: Wenckebach periods with irregular H-H intevals. Am JCardioll979; 43:653. 15. Schweitzer P, Choudhry M, Kunkis SH, et al: Extra AV nodal Wenckebach periodicity. J Electrocardiol 1981; 14:225. 16. DiMarco J, Sellers TD, Belardinelli L: Paroxysmal supraventricular tachycardia with Wenckebach block: evidence for reentry within the upper portion of the atrioventricular node. JACC 1984; 3:1551. 17. Vasudevan G, Brostoff P, Varat MA: Alternating Wenckebach periods with acute myocardial infarction. Chest 1979; 75~197. 18. Langendorf R, Pick A: Atrioventricular block, type II (Mobitz) - its nature and clinical significance. Circulation 1968; 38:819. 19. Braunwald E: Heart D&ewe-A Textbook of Cardiovascular Medicine WB Saunders Company, 1984, Vol 2, p 1287.