Overview
What is a second-degree atrioventricular (AV) block?
What are the signs and symptoms of second-degree atrioventricular (AV) block?
Which ECG findings are characteristic of Mobitz I second-degree atrioventricular (AV) block?
Which ECG findings are characteristic of Mobitz II second-degree atrioventricular (AV) block?
What are prognostic factors in second-degree atrioventricular (AV) block?
How is the site of a second-degree atrioventricular (AV) block indicated on ECG?
What is the role of lab testing in the evaluation of second-degree atrioventricular (AV) block?
How is a Mobitz type I second-degree atrioventricular (AV) block treated?
How is a Mobitz type II second-degree atrioventricular (AV) block treated?
When is permanent pacing unnecessary for the treatment of second-degree atrioventricular (AV) block?
What is second-degree atrioventricular (AV) block?
What are the types of second-degree atrioventricular (AV) block?
What is the pathophysiology of second-degree atrioventricular (AV) block?
What is the role of medications in the etiology of second-degree atrioventricular (AV) block?
Which conditions are associated with second-degree atrioventricular (AV) block?
What is the role of cardiac tumors in the etiology of second-degree atrioventricular (AV) block?
What is the role of catheter ablation in the etiology of second-degree atrioventricular (AV) block?
What is the role of muscular dystrophy in the etiology of second-degree atrioventricular (AV) block?
What is the role of ethanol poisoning in the etiology of second-degree atrioventricular (AV) block?
What is the role of genetics in the etiology of second-degree atrioventricular (AV) block?
What is the prevalence of second-degree atrioventricular (AV) block?
What is the prognosis of second-degree atrioventricular (AV) block?
Presentation
What are the signs and symptoms of second-degree atrioventricular (AV) block?
DDX
What are the differential diagnoses for Second-Degree Atrioventricular Block?
Workup
Which tests are performed in the workup of second-degree atrioventricular (AV) block?
Which ECG findings are characteristic of Mobitz I second-degree atrioventricular (AV) block?
Which ECG findings are characteristic of Mobitz II second-degree atrioventricular (AV) block?
Which ECG findings indicate an infranodal second-degree atrioventricular (AV) block?
Treatment
How is second-degree atrioventricular (AV) block treated?
How is Mobitz I second-degree atrioventricular (AV) block treated?
How is Mobitz II second-degree atrioventricular (AV) block treated?
What is the management for 2:1 second-degree atrioventricular (AV) block?
What is the role of permanent pacing in the treatment of second-degree atrioventricular (AV) block?
Medications
What is the role of atropine in the treatment of second-degree atrioventricular (AV) block?
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Typical Mobitz I atrioventricular block with progressive prolongation of PR interval before blocked P wave. Pauses are always less than sum of 2 preceding beats because PR interval after pause always shortens.
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Mobitz II atrioventricular (AV) block with intermittent periods of 2:1 AV block. If only 2:1 block was seen in beginning of strip, site of block could not be localized with certainty; however, single dropped QRS complex at end of strip with constant PR interval indicates that this block is localized in one of the bundle branches.
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Variable-ratio Mobitz I atrioventricular block. Note marked PR-interval prolongation in first beat of each cycle. Maximum prolongation of PR interval takes place in second beat of cycle, with much smaller increments in subsequent beats. Also, notice that R-R interval actually shortens with each beat—paradox of shortening R-R interval when PR interval increases by diminishing increments.
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Sinus rhythm with Mobitz I second-degree 3:2 infranodal atrioventricular (AV) block and bifascicular block. Note that AH interval (indicative of AV nodal conduction) remains constant. HV interval (indicative of His-Purkinje conduction) increases from 65 msec (after first P wave) to 185 msec (after second P wave). Third P wave is followed a His bundle deflection (H) but no QRS complex. AV block occurs in His-Purkinje system below site of recording of His bundle potential. Note shorter PR interval after nonconducted P wave, typical of Mobitz I AV block. HRA = high right atrial electrogram; A = atrial deflection; HB = His bundle electrogram, proximal and distal; H = His bundle deflection; RV = right ventricular electrogram; T = time line, 50 msec.
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Representative 12-lead electrocardiogram in asymptomatic 78-year-old woman during recent noncardiac surgery. Patient was referred for implantation of permanent pacemaker with diagnosis of sinus tachycardia with 2:1 atrioventricular (AV) block and narrow QRS complex. As sinus rate slowed, 1:1 AV conduction resumed. Intracardiac recordings confirmed diagnosis of infra-Hisian 2:1 AV block.
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Electrocardiogram of patient with Mobitz I (Wenckebach) second-degree atrioventricular block.
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Electrocardiogram of patient with Mobitz II second-degree atrioventricular block.