Third degree AV block: Difference between revisions
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==Background== | ==Background== | ||
* | [[File:Rhythm strip showing third degree heart block.jpg|thumb|Rhythm strip showing third degree AV block. Note that the P waves are not related to the QRS complexes (PP interval and QRS interval both constant), demonstrating that the atria are electrically disconnected from the ventricles.]] | ||
*Also known as complete heart block | |||
*No conduction through the AV node, causing the atria and ventricles beat completely independently from each other | |||
*The ventricular beat is an escape rhythm anywhere from the AV node to the bundle-branches (normally slow, varying from 35 to 45 beats per minute) | |||
===Causes=== | ===Causes=== | ||
*Congenital | *Congenital | ||
*Acquired | *Acquired | ||
**Ischemia | **[[Myocardial ischemia|Ischemia]] | ||
**Drugs | **Increased vagal tone | ||
**[[Hypothyroidism]] | |||
**[[Hyperkalemia]] | |||
**[[Toxicology (Main)|Drugs]] | |||
**Structural heart disease | **Structural heart disease | ||
==Clinical Features== | ==Clinical Features== | ||
*Dizziness | *[[Dizziness]] | ||
*[[Syncope]] | *[[Syncope]] | ||
*Hypotension | *[[Hypotension]] | ||
==Differential Diagnosis== | ==Differential Diagnosis== | ||
| Line 24: | Line 30: | ||
**QRS wide if block below bundle of His | **QRS wide if block below bundle of His | ||
**PR variable | **PR variable | ||
*Differentiate from AV dissociation without complete heart block | |||
[[File:AVD without CHB.png|thumbnail|AVD without CHB, courtesy of public access Amal Mattu EKG videos]] | |||
==Management== | ==Management== | ||
{{Heart block management}} | |||
==Disposition== | ==Disposition== | ||
*Admission | *Admission for [[Pacemaker (Basics)|pacemaker]] placement | ||
==See Also== | ==See Also== | ||
*[[ECG ( | *[[ECG (Main)]] | ||
==References== | ==References== | ||
Latest revision as of 15:10, 21 December 2020
Background
- Also known as complete heart block
- No conduction through the AV node, causing the atria and ventricles beat completely independently from each other
- The ventricular beat is an escape rhythm anywhere from the AV node to the bundle-branches (normally slow, varying from 35 to 45 beats per minute)
Causes
- Congenital
- Acquired
- Ischemia
- Increased vagal tone
- Hypothyroidism
- Hyperkalemia
- Drugs
- Structural heart disease
Clinical Features
Differential Diagnosis
AV blocks
- First degree AV block
- Second degree
- Third degree AV block
- AV dissociation without complete heart block
Evaluation
- No atrial impulses are conducted
- P waves normal and regular P-P intervals unrelated to slower regular R-R intervals
- QRS narrow if block above bundle of His
- QRS wide if block below bundle of His
- PR variable
- Differentiate from AV dissociation without complete heart block
Management
- If symptomatic, standard ACLS guidelines for symptomatic bradycardia to include[1]
- Atropine 0.5mg IV q3-5min PRN total dose of 3mg
- Transcutaneous pacing, followed by transvenous pacing
- Dopamine IV consider for low BP 3mcg/kg/minute titrate up to 20 mcg/kg/minute
- Dobutamine IV consider for heart failure at 5mcg/kg/minute titrate up to 20mcg/kg/minute if needed for HR and BP augmentation
- Treat underlying etiology
- Avoid AV nodal blocking agents (e.g. β-blockers)
Disposition
- Admission for pacemaker placement
See Also
References
- ↑ Sovari AA et al. Second-Degree Atrioventricular Block Treatment & Management. eMedicine. Apr 28, 2014. http://emedicine.medscape.com/article/161919-treatment#showall.