Junctional Dysrhythmias 10 Junctional Dysrhythmias Fast & Easy ECGs – A Self-Paced Learning Program Q I A

Junctional Dysrhythmias Originate in AV junction (area around AV node and bundle of His)

Junctional Dysrhythmias Key characteristics P’ waves may be inverted with a short P’R interval, absent (as they are buried by the QRS complex), or follow QRS complexes QRS complexes usually normal unless there is an intraventricular conduction defect, aberrancy or preexcitation Instructional points: Because the AV junction is located in the middle of the heart the impulse travels upward and causes backward or retrograde depolarization of the atria. This results in an inverted P’ wave (when they would otherwise be upright) with a short P’R interval (less than 0.12 second in duration). At the same time the impulse travels down to the ventricles and depolarizes them. Junctional dysrhythmias will only have clinical consequences to the patient if cardiac output is adversely affected. I

Premature Junctional Complex (PJC) Single early electrical impulse that arises from the AV junction Question to ask the students: “How will the premature beat affect the P-P and R-R intervals?” Answer: With a premature beat the P-P and R-R interval is shorter between the beat that the premature beat follows and the premature beat. Instructional point: PJCs can also occur in bigeminal, trigeminal or quadrigeminal patterns. Q I

Premature Junctional Complex Instructional points: PJCs rarely cause any concern but could indicate increased sympathetic tone which should be investigated and corrected if possible. However, frequent PJCs can result in decreased stroke volume and lead to compromised cardiac output. PJCs are not usually followed by a compensatory pause. I

Premature Junctional Complex

Junctional Escape Rhythm Arises from AV junction at rate of 40 to 60 BPM Instructional point: Junctional Escape is potentially lethal because it indicates that the patient’s primary pacemaker is not functioning. These patients may require the placement of a pacemaker. Furthermore, the slow rate may adversely affect cardiac output. I

Junctional Escape Rhythm Question to ask the students “What is the key difference between junctional escape rhythm, accelerated junctional rhythm and junctional tachycardia?” Answer: The heart rate. Q

Junctional Escape Rhythm

Accelerated Junctional Rhythm Arises from AV junction at rate of 60 to 100 BPM Instructional point: Accelerated Junctional rhythm is a common rhythm seen following cardiac arrest resuscitation until the SA node awakens and takes control of the rate. The rate is increased because of either high sympathetic tone or the effects of the adrenergic agents such as epinephrine used during resuscitation. I

Accelerated Junctional Rhythm

Accelerated Junctional Rhythm

Junctional Tachycardia Fast ectopic rhythm that arises from bundle of His at rate of 100 to 180 BPM Instructional point: Junctional Tachycardia is relatively rare but when present may serious drop cardiac output because of the very fast rate. I

Junctional Tachycardia

Junctional Tachycardia

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 50 BPM, Ventricular rate 50 BPM, regular rhythm, inverted P′ wave preceding each QRS complex, normal QRS complexes at 0.10 seconds, PRI 0.10 seconds, QT 0.58 seconds. Junctional escape rhythm. I

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 188 BPM, Ventricular rate 188 BPM, regular rhythm, inverted P′ wave preceding each QRS complex, normal QRS complexes at 0.12 seconds, PRI 0.10 seconds, QT 0.24 seconds. Junctional tachycardia . I

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 79 BPM, Ventricular rate 79 BPM, occasionally irregular, upright and normal P waves in the underlying rhythm, P′ waves associated with premature beats are absent, QRS complexes are 0.10 seconds, PRI 0.16 seconds in underlying rhythm and immeasurable in the premature beats, QT 0.40 seconds. Normal sinus rhythm with 2 junctional complexes (PJCs) (6th and 8th complexes), this could be progressing into a junctional bigeminy. I

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 56 BPM, Ventricular rate 56 BPM, regular rhythm, P′ waves are absent, normal QRS complexes at 0.10 seconds, PRI is immeasurable, QT 0.40 seconds. Junctional escape rhythm. I

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 80 BPM, Ventricular rate 80 BPM, patterned irregularity, upright and normal P waves in the underlying rhythm, P′ waves associated with premature beats are absent, normal QRS complexes at 0.10 seconds, PRI 0.16 seconds in underlying rhythm and immeasurable in the premature beats, QT 0.40 seconds.Normal sinus rhythm with bigeminal premature junctional complexes (PJCs) (2nd, 4th, 6th and 8th complexes). I

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 120 BPM, Ventricular rate 120 BPM, regular rhythm, inverted P′ wave follows each QRS complex, normal QRS complexes at 0.08 seconds, P′RI 0.16 seconds, QT 0.36 seconds. Junctional tachycardia. I

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 82 BPM, Ventricular rate 82 BPM, regular rhythm, P′ waves are absent, normal QRS complexes at 0.10 seconds, P′RI is immeasurable, QT 0.34 seconds. Accelerated junctional rhythm. I

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 92 BPM, Ventricular rate 92 BPM, regular rhythm, P′ waves are absent, normal QRS complexes at 0.08 seconds, PRI is immeasurable, QT 0.36 seconds. Accelerated junctional rhythm. I

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 30 BPM, Ventricular rate 30 BPM, regular rhythm, inverted P′ wave follows each QRS complex, normal QRS complexes at 0.08 seconds, P′RI 0.18 seconds, QT 0.40 seconds. Slow junctional escape rhythm. I

Practice Makes Perfect Determine the type of dysrhythmia Answer: Atrial rate 82 BPM, Ventricular rate 82 BPM, regular rhythm, P′ waves are absent, normal QRS complexes at 0.10 seconds, P′RI is immeasurable, QT 0.34 seconds. Accelerated junctional rhythm. I

Summary Junctional rhythms originate in the AV junction. Impulses originating in the AV junction travel upward and cause backward or retrograde depolarization of the atria resulting in inverted P’ waves in lead II with a short P’R interval, absent P waves or P waves that follow the QRS complexes. With junctional dysrhythmias the QRS complexes are usually normal unless there is an intraventricular conduction defect, aberrancy or preexcitation.

Summary A premature junctional complex (PJC) is a single early electrical impulse that arises from the AV junction. Junctional escape rhythm arises from the AV junction at a rate of 40 to 60 beats per minute. Accelerated junctional rhythm arises from the AV junction at a rate of 60 to 100 beats per minute. Junctional tachycardia is a fast ectopic rhythm that arises from the bundle of His at a rate of between 100 and 180 beats per minute.