+ All Categories
Home > Documents > ECG Tutorial_ Atrioventricular Block

ECG Tutorial_ Atrioventricular Block

Date post: 15-Dec-2015
Category:
Upload: williamraycassidy
View: 221 times
Download: 0 times
Share this document with a friend
Description:
ecg av block
Popular Tags:
13
Official reprint from UpToDate www.uptodate.com ©2015 UpToDate Author Jordan M Prutkin, MD, MHS, FHRS Section Editor Ary L Goldberger, MD Deputy Editor Gordon M Saperia, MD, FACC ECG tutorial: Atrioventricular block All topics are updated as new evidence becomes available and our peer review process is complete. Literature review current through: Jun 2015. | This topic last updated: Jan 23, 2014. INTRODUCTION — Atrioventricular (AV) block may manifest as conduction delay in the AV node, intermittent failure of conduction from the atria to the ventricles, or complete AV block. FIRST DEGREE ATRIOVENTRICULAR BLOCK — The PR interval (a measure of conduction between the atria and ventricles) includes the P wave (intraatrial conduction) and the PR segment (conduction within the atrioventricular [AV] node and HisPurkinje system). First degree AV block, defined as a prolonged PR interval (>0.20 seconds), is not a true block but is rather delayed or slowed AV conduction. The conduction delay is most frequently in the AV node but may also be in the HisPurkinje system (waveform 1 ). First degree AV block may result from the following: As there is no actual block of conduction between the atrium to the ventricle, it is more appropriate to use the term “prolonged AV conduction” rather than block. As the PR interval includes the P wave (interatrial conduction) and the PR segment, a prolonged PR interval may also be due to a delay or slowing in intraatrial conduction. (See "Etiology of atrioventricular block" and "First degree atrioventricular block" .) The PR interval generally varies with the heart rate; in the presence of sinus bradycardia (usually the result of enhanced vagal tone), the PR interval lengthens as conduction through the AV node slows. In contrast, the PR interval becomes shorter during sinus tachycardia, which is the result of enhanced sympathetic tone that enhances conduction through the AV node. At very fast heart rates or in those with AV node disease, however, the PR interval may lengthen due to decremental conduction. SECOND DEGREE ATRIOVENTRICULAR BLOCK — Second degree atrioventricular (AV) block is defined as an occasional nonconducted P wave, resulting in a long RR interval. Second degree AV block may either be Mobitz type I (Wenckebach) or Mobitz type II. Mobitz type I — Mobitz type I or Wenckebach second degree AV block is a result of intermittent block of the impulse within the AV node, with subsequent failure to conduct an atrial impulse from the atria to the ventricles. (See "Etiology of atrioventricular block" and "Second degree atrioventricular block: Mobitz type I (Wenckebach block)" .) Impaired AV nodal conduction is due to progressive slowing of each subsequent impulse in the AV node due to decremental conduction, until the node finally fails to conduct the impulse because it has arrived at a time when it is absolutely refractory. The result is no conduction to the ventricle and no QRS impulse on the electrocardiogram (ECG). The ECG correlates of these electrical events include the following (waveform 2 ): ® ® Underlying structural abnormalities of the node An increase in vagal tone that causes a reduction in the rate of impulse conduction Drugs that impair or slow nodal conduction including digoxin , beta blockers, and nondihydropyridine calcium channel blocking agents There is a progressive lengthening of the PR interval until a normally occurring P wave is not followed by a QRS complex because of failure of the node to conduct the impulse to the ventricle. There is only one nonconducted P wave. Any pattern of block (eg, 2:1, 3:2, 4:3, etc, or a variable pattern) may occur, depending upon the AV nodal electrophysiologic properties and the degree of vagal tone.
Transcript
Page 1: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_resul… 1/13

Official reprint from UpToDate www.uptodate.com ©2015 UpToDate

AuthorJordan M Prutkin, MD,MHS, FHRS

Section EditorAry L Goldberger, MD

Deputy EditorGordon M Saperia, MD,FACC

ECG tutorial: Atrioventricular block

All topics are updated as new evidence becomes available and our peer review process is complete.Literature review current through: Jun 2015. | This topic last updated: Jan 23, 2014.

INTRODUCTION — Atrioventricular (AV) block may manifest as conduction delay in the AV node,intermittent failure of conduction from the atria to the ventricles, or complete AV block.

FIRST DEGREE ATRIOVENTRICULAR BLOCK — The PR interval (a measure of conduction between theatria and ventricles) includes the P wave (intra­atrial conduction) and the PR segment (conduction within theatrioventricular [AV] node and His­Purkinje system). First degree AV block, defined as a prolonged PRinterval (>0.20 seconds), is not a true block but is rather delayed or slowed AV conduction. The conductiondelay is most frequently in the AV node but may also be in the His­Purkinje system (waveform 1). Firstdegree AV block may result from the following:

As there is no actual block of conduction between the atrium to the ventricle, it is more appropriate to usethe term “prolonged AV conduction” rather than block.

As the PR interval includes the P wave (interatrial conduction) and the PR segment, a prolonged PR intervalmay also be due to a delay or slowing in intraatrial conduction. (See "Etiology of atrioventricular block" and"First degree atrioventricular block".)

The PR interval generally varies with the heart rate; in the presence of sinus bradycardia (usually the resultof enhanced vagal tone), the PR interval lengthens as conduction through the AV node slows. In contrast,the PR interval becomes shorter during sinus tachycardia, which is the result of enhanced sympathetic tonethat enhances conduction through the AV node. At very fast heart rates or in those with AV node disease,however, the PR interval may lengthen due to decremental conduction.

SECOND DEGREE ATRIOVENTRICULAR BLOCK — Second degree atrioventricular (AV) block is definedas an occasional non­conducted P wave, resulting in a long RR interval. Second degree AV block may eitherbe Mobitz type I (Wenckebach) or Mobitz type II.

Mobitz type I — Mobitz type I or Wenckebach second degree AV block is a result of intermittent block of theimpulse within the AV node, with subsequent failure to conduct an atrial impulse from the atria to theventricles. (See "Etiology of atrioventricular block" and "Second degree atrioventricular block: Mobitz type I(Wenckebach block)".)

Impaired AV nodal conduction is due to progressive slowing of each subsequent impulse in the AV node dueto decremental conduction, until the node finally fails to conduct the impulse because it has arrived at a timewhen it is absolutely refractory. The result is no conduction to the ventricle and no QRS impulse on theelectrocardiogram (ECG).

The ECG correlates of these electrical events include the following (waveform 2):

®®

Underlying structural abnormalities of the nodeAn increase in vagal tone that causes a reduction in the rate of impulse conductionDrugs that impair or slow nodal conduction including digoxin, beta blockers, and non­dihydropyridinecalcium channel blocking agents

There is a progressive lengthening of the PR interval until a normally occurring P wave is not followedby a QRS complex because of failure of the node to conduct the impulse to the ventricle. There is onlyone non­conducted P wave. Any pattern of block (eg, 2:1, 3:2, 4:3, etc, or a variable pattern) mayoccur, depending upon the AV nodal electrophysiologic properties and the degree of vagal tone.

Page 2: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_resul… 2/13

All of these features may not be seen in each case of Mobitz type I second degree AV block.

Mobitz type II — Mobitz type II second degree AV block is usually indicative of underlying disease of theHis­Purkinje system that is characterized by episodic and unpredictable failure of the His­Purkinje pathwayto conduct the impulse from the atria to the ventricles. The block occurs below the AV node and within thebundle of His or both bundle branches. (See "Etiology of atrioventricular block" and "Second degreeatrioventricular block: Mobitz type II".)

In contrast to Mobitz type I, there is no change in the PR interval prior to or after the non­conducted P wave(waveform 3). This is because the His­Purkinje system is all or none, ie, it either conducts (always at thesame rate) or does not conduct an impulse. Mobitz type II has a higher risk of complete heart block thanMobitz type 1 and is usually an indication for a pacemaker, even if asymptomatic. If complete heart blockwere to develop, the escape rhythm is almost always ventricular and wide complex. (See "Permanentcardiac pacing: Indications".)

2:1 AV block — A specific form of second degree AV block is termed “2:1 AV block.” In this situation, everyother P wave is non­conducted, and it is not possible to determine if the block is Mobitz type I or Mobitz II.

The etiology can only be established when there are two or more sequentially conducted P waves, and,therefore, two or more PR intervals. This may occur spontaneously or when there are changes in the sinusrate, such as with activity or exercise. If there is progressive lengthening of the PR intervals on theconsecutive conducted beats, the etiology of the 2:1 AV block is presumed to be Mobitz type I. If the PRintervals are constant, the etiology is Mobitz type II.

High grade AV block — There may be more than one successive non­conducted P wave, resulting inseveral P waves in a row without QRS complexes, termed “advanced” or “high grade AV block.” The AVconduction ratio may or may not have a regular pattern (ie, 3:1, 4:1, etc). This is an advanced form of Mobitztype II second degree AV block.

Variable AV block — Variable AV block is usually used to describe a type of ventricular response to atrialflutter or atrial tachycardia (waveform 4). The AV conduction ratio varies between 2:1, 3:1, and higher, ie,there is more than one non­conducted P wave, but there is no reproducible pattern to the AV conduction.The PR interval of the conducted P waves is constant.

THIRD DEGREE ATRIOVENTRICULAR BLOCK — Third degree or complete atrioventricular (AV) blockoccurs when there is complete failure of the AV node to conduct any impulses from the atria to theventricles. This presents with AV dissociation (variable PR intervals) and an escape rhythm that is eitherjunctional or ventricular. The atrial rate is faster than the rate of the escape rhythm. (See "Third degree(complete) atrioventricular block".) This is the result of intrinsic AV nodal disease or disease of the His­Purkinje system. (See "Etiology of atrioventricular block".)

Causes include:

The completely blocked P wave is on time and all PP intervals are equal.

The impulse that arrives at the node following the completely blocked beat is conducted normally againbecause the node has had time to become totally repolarized. Thus, the PR interval after thenonconducted beat is less than the PR interval immediately preceding the nonconducted beat. The PRinterval following the pause is the baseline PR interval.

The baseline PR interval (ie, the PR interval after each pause) is usually normal duration, but may beprolonged, since both first degree AV block and Mobitz type 1 second degree AV block reflect diseasein the AV node.

The incremental lengthening of each successive PR interval becomes progressively lessened (eg,0.20, then 0.26, then 0.30 seconds, etc). The greatest increase in PR interval lengthening is from thefirst to second conducted beats, and all subsequent conducted beats have a PR interval that increasesless quickly. This results in a progressive shortening of successive RR intervals and is one of thecauses of grouped beating on the ECG.

Page 3: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_resul… 3/13

The P waves are completely dissociated from the QRS complexes on the electrocardiogram, ie, there is AVdissociation (waveform 5). Thus, the PR intervals are irregularly variable. The atrial and ventricular rates areboth stable; the former is faster than the latter. If there is AV dissociation with an atrial rate that is slowerthan the ventricular rate, this is not complete heart block but is an accelerated rhythm (either junctional orventricular).

If the complete heart block is the result of AV nodal disease, the dominant pacemaker activating theventricles is usually located in the lower portion of the AV junction below the block, resulting in a junctionalescape rhythm that is usually at a rate between 40 to 60 beats/minute. However, the location of the escaperhythm is established by the morphology of the QRS complexes and not the rate. With a junctional escaperhythm, the QRS complexes are narrow and resemble those of sinus rhythm. However, if there is coexistentdisease in the right or left bundle, the QRS complexes of the escape junctional rhythm will be widened,resembling a ventricular complex with a typical right or left bundle branch block configuration, which wouldalso be the QRS morphology seen during sinus rhythm.

The dominant pacemaker is within the ventricular myocardium if the block is below the junction within theHis­Purkinje system. This results in a ventricular escape rhythm with a wide QRS complex that does notresemble either a typical right or left bundle branch block. Although it usually is associated with a rate that isless than 40 beats/minute, it may be more rapid if there is sympathetic activation. Hence, the diagnosis of aventricular escape rhythm is based upon the morphology of the QRS complexes and the actual rate isdependent upon sympathetic­parasympathetic balance (waveform 6A­B).

PAROXYSMAL ATRIOVENTRICULAR BLOCK — Paroxysmal atrioventricular (AV) block is an unexpectedepisode of AV block occurring after a premature atrial or ventricular contraction leading to a prolonged pauseand ventricular asystole. It is thought to be due to a diseased His­Purkinje system, where there is anincreased rate of spontaneous Phase 4 depolarization. Normally, no ill effect is seen with abnormal Phase 4depolarization, but when there is a pause following a premature beat, this allows for more time for the cellmembrane to become less negative and development of sodium channel inactivation. Subsequent beats areunable to conduct through the His­Purkinje system. Only a properly timed escape or premature beat canreset the membrane potential to normal and allow for resumption of AV conduction. Most frequently, patientshave evidence of right or left bundle branch block or intraventricular conduction delay on the baselineelectrocardiogram.

VENTRICULOPHASIC SINUS ARRHYTHMIA — A ventriculophasic sinus arrhythmia may be seenwhenever there is second or third degree atrioventricular block with episodic or permanent failure ofantegrade conduction through the AV node. This is manifest as intermittent differences in the PP intervalsbased upon their relationship to the QRS complex (waveform 7). The two P waves surrounding a QRScomplex have a relatively shortened interval (ie, occur at a faster rate) when compared to two P waveswithout an intervening QRS complex. The reason for this change (shortening) in PP interval is not certain. It

Coronary artery diseaseDrugs that depress or block nodal conduction such as digoxin, beta blockers, or non­dihydropyridinecalcium channel blockers.

Enhanced vagal tone, such as that occurring during sleep.Congenital electrical heart disease. (See "Congenital third degree (complete) atrioventricular block".)Infranodal block occurring within the bundle of His or in both bundle branches. This is usually the resultof underlying structural heart disease, such as myocardial infarction, hypertrophy, inflammation, orinfiltration. On occasion, it is due to Lev’s or Lenegre’s disease (fibrosis or fibrocalcification of theconduction system).

Infectious heart disease, such as Lyme disease.Post­cardiac surgery.Cardiomyopathy.Rheumatologic and autoimmune diseases.Infiltrative diseases including amyloidosis and sarcoidosis.Certain types of muscular dystrophy.

Page 4: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_resul… 4/13

has been proposed that it is due to baroreceptor activation in the carotid sinus resulting from ventricularcontraction on the conducted beats, leading to a shortening of the subsequent PP interval. Anotherexplanation is that ventricular contraction causes both an increase in pulsatile blood flow through the sinusnodal artery and an increased stretch on the sinus node due to ventricular contraction which enhance nodalautomaticity.

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics”and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5 to 6grade reading level, and they answer the four or five key questions a patient might have about a givencondition. These articles are best for patients who want a general overview and who prefer short, easy­to­read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and moredetailed. These articles are written at the 10 to 12 grade reading level and are best for patients who wantin­depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e­mailthese topics to your patients. (You can also locate patient education articles on a variety of subjects bysearching on “patient info” and the keyword(s) of interest.)

SUMMARY

Use of UpToDate is subject to the Subscription and License Agreement.

Topic 2124 Version 7.0

th th

th th

Basics topic (see "Patient information: Heart block in adults (The Basics)")

First degree atrioventricular (AV) nodal block, defined as a prolonged PR interval (>0.20 seconds),occurs when there is a prolongation or delay in impulse conduction through the AV node (mostcommon) or His­Purkinje system (waveform 1). It is best termed prolonged AV conduction.

Second degree AV block, defined as an occasional long RR interval resulting from an occasional non­conducted P wave, may either be Mobitz type I or type II:

Mobitz type I (Wenkebach) second degree AV block is usually a result of progressive slowing ofAV conduction through the AV node with subsequent failure to conduct one atrial impulse fromthe atria to the ventricles (waveform 2). This is manifest as progressive PR prolongation beforethe dropped beat. There is only one non­conducted P wave.

Mobitz type II second degree AV block is usually indicative of underlying disease of the His­Purkinje conduction system and is characterized by episodic and unpredictable failure of the nodeto conduct the impulse (or more than one impulse) from the atria to the ventricles (waveform 3).The PR interval does not change prior to or after the dropped beats. There may be more than onenon­conducted P wave.

2:1 AV block is identified by the fact that every other P wave is non­conducted. This may be eitherMobitz I or Mobitz II.

Third degree or complete AV block occurs when there is complete failure of the AV node to conductany impulses from the atria to the ventricles, resulting in an escape rhythm (waveform 5). There is AVdissociation (ie, variable PR intervals) and the atrial rate is faster than the ventricular rate. The escaperhythm may be either junctional or ventricular and this is based on the QRS complex morphology andnot the rate of the escape rhythm.

Paroxysmal AV block is the development of complete heart block and ventricular asystole after apremature atrial or ventricular contraction. A properly timed escape or premature beat is able to resetthe rhythm and lead to resumption of AV conduction.

Page 5: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_resul… 5/13

GRAPHICS

First degree atrioventricular (AV) block

First degree AV block is caused by a prolongation or delay in impulse conductionthrough the AV node. It is defined as a PR interval >0.20 seconds. In this casethe PR interval (blue lines) is approximately 0.22 seconds.

Graphic 79990 Version 2.0

Sinus rhythm

The normal P wave in sinus rhythm is slightly notched since activationof the right atrium precedes that of the left atrium. The P wave isupright in a positive direction in leads I and II. A P wave with auniform morphology precedes each QRS complex. The rate is between60 and 100 beats per minute and the cycle length is uniform betweensequential P waves and QRS complexes. In addition, the P wavemorphology and PR intervals are identical from beat to beat.

Graphic 69872 Version 2.0

Page 6: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_resul… 6/13

Mobitz type I second degree atrioventricular (AV)block

Several characteristic features of Wenckebach second degree AV blockare noted on this ECG (P waves are marked by arrows): 1) The PRinterval after the second P wave is longer than the preceeding PRinterval; the third P wave is not conducted at all. 2) The PP intervals areconstant; however, the RR interval surrounding the completely blockedP wave is longer than the preceeding normal RR interval. 3) The fourthP wave (after the blocked beat) is conducted normally; this PR intervalis shorter than the PR interval that immediately preceeded the pause.

Graphic 71453 Version 3.0

Sinus rhythm

The normal P wave in sinus rhythm is slightly notched since activationof the right atrium precedes that of the left atrium. The P wave isupright in a positive direction in leads I and II. A P wave with auniform morphology precedes each QRS complex. The rate is between60 and 100 beats per minute and the cycle length is uniform betweensequential P waves and QRS complexes. In addition, the P wavemorphology and PR intervals are identical from beat to beat.

Graphic 69872 Version 2.0

Page 7: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_resul… 7/13

Mobitz type II second degree atrioventricular (AV)block

The third and sixth P waves are not conducted through the AV node (there isno associated QRS complex). The PR interval is constant prior to and after thenon­conducted beats.

Graphic 58649 Version 3.0

Sinus rhythm

The normal P wave in sinus rhythm is slightly notched since activationof the right atrium precedes that of the left atrium. The P wave isupright in a positive direction in leads I and II. A P wave with auniform morphology precedes each QRS complex. The rate is between60 and 100 beats per minute and the cycle length is uniform betweensequential P waves and QRS complexes. In addition, the P wavemorphology and PR intervals are identical from beat to beat.

Graphic 69872 Version 2.0

Page 8: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_resul… 8/13

Variable atrioventricular (AV) block

Atrial flutter is commonly associated with variable AV block. The AVconduction ratio varies between 2:1 and 3:1 in this case.

Graphic 74851 Version 2.0

Sinus rhythm

The normal P wave in sinus rhythm is slightly notched since activationof the right atrium precedes that of the left atrium. The P wave isupright in a positive direction in leads I and II. A P wave with auniform morphology precedes each QRS complex. The rate is between60 and 100 beats per minute and the cycle length is uniform betweensequential P waves and QRS complexes. In addition, the P wavemorphology and PR intervals are identical from beat to beat.

Graphic 69872 Version 2.0

Page 9: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_resul… 9/13

Third degree (complete) atrioventricular block withnarrow QRS escape rhythm

The P waves are completely dissociated from the QRS complexes. The QRScomplexes are narrow, indicating a junctional escape rhythm. The atrial andventricular rates are stable; the former is faster than the latter.

Graphic 65545 Version 5.0

Normal rhythm strip

Normal rhythm strip in lead II. The PR interval is 0.15 sec and theQRS duration is 0.08 sec. Both the P and T waves are upright.

Courtesy of Morton F Arnsdorf, MD.

Graphic 59022 Version 3.0

Page 10: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_res… 10/13

Complete heart block: Sinus rhythm with slow junctionalor idioventricular escape rhythym

Multiple successive QRS complexes appear that are of ventricular origin andoccur at a rate which is slower than the underlying sinus rhythm. The presenceof P waves that occur independent of the QRS complexes is evidence ofatrioventricular dissociation.

Graphic 54024 Version 4.0

Sinus rhythm

The normal P wave in sinus rhythm is slightly notched since activationof the right atrium precedes that of the left atrium. The P wave isupright in a positive direction in leads I and II. A P wave with auniform morphology precedes each QRS complex. The rate is between60 and 100 beats per minute and the cycle length is uniform betweensequential P waves and QRS complexes. In addition, the P wavemorphology and PR intervals are identical from beat to beat.

Graphic 69872 Version 2.0

Page 11: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_res… 11/13

Third degree (complete) atrioventricular blockwith wide QRS escape rhythm

The P waves are completely dissociated from the QRS complexes andthe PR intervals are variable. The atrial or PP rate (75 beats per minute)is faster than the ventricular or RR rate (30 beats per minute),establishing complete atrioventricular nodal blockade as the etiology.The QRS complexes are wide indicating that the escape rhythm isventricular.

Graphic 51446 Version 4.0

Normal rhythm strip

Normal rhythm strip in lead II. The PR interval is 0.15 sec and theQRS duration is 0.08 sec. Both the P and T waves are upright.

Courtesy of Morton F Arnsdorf, MD.

Graphic 59022 Version 3.0

Page 12: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_res… 12/13

Ventriculophasic sinus arrhythmia

A ventriculophasic sinus arrhythmia is characterized by episodic orpermanent failure of conduction throught the atrioventricular (AV) node.In contrast to the typical second or third degree AV block, the PPintervals are not constant; the two P waves surrounding a QRS complexhave a shortened interval or occur at a faster rate when compared totwo P waves that occur sequentially without an intervening QRScomplex.

Graphic 75898 Version 2.0

Sinus rhythm

The normal P wave in sinus rhythm is slightly notched since activationof the right atrium precedes that of the left atrium. The P wave isupright in a positive direction in leads I and II. A P wave with auniform morphology precedes each QRS complex. The rate is between60 and 100 beats per minute and the cycle length is uniform betweensequential P waves and QRS complexes. In addition, the P wavemorphology and PR intervals are identical from beat to beat.

Graphic 69872 Version 2.0

Page 13: ECG Tutorial_ Atrioventricular Block

7/12/2015 ECG tutorial: Atrioventricular block

http://www.uptodate.com.ezproxy.ugm.ac.id/contents/ecg-tutorial-atrioventricular-block?topicKey=CARD%2F2124&elapsedTimeMs=0&source=search_res… 13/13

Disclosures: Jordan M Prutkin, MD, MHS, FHRS Grant/Research/Clinical Trial Support: BostonScientific [Heart block (Pacemakers and ICDs)]; St. Jude Medical [Sudden death (Pacemakers andICDs)]. Ary L Goldberger, MD Nothing to disclose. Gordon M Saperia, MD, FACC Nothing to disclose.Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these areaddressed by vetting through a multi­level review process, and through requirements for references to beprovided to support the content. Appropriately referenced content is required of all authors and mustconform to UpToDate standards of evidence.Conflict of interest policy

Disclosures


Recommended