Third degree AV block other diagnostic studies
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sara Zand, M.D.[2] Soroush Seifirad, M.D.[3]
Overview
Ambulatory monitoring is warranted in cases of possible transient heart block, or some other bradyarrhythmias that might be mistaken with third-degree AV block. Worsening atrioventricular block with isoproterenol and atropine may be suggestive of infranodal block. Improvement of atrioventricular conduction with carotid sinus massage may be observed in patients with infranodal atrioventricular block.
Other Diagnostic Studies
| Other diagnostic testing for bradycardia associated atrioventricular block |
| (Class IIa, Level of Evidence B): |
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❑Ambulatory electrocardiographic monitoring is recommended in the presence of first degree atrioventricular block or second degree atrioventricular block mobitz type 1 on ECG with symptoms of bradycardia (dizziness, faint) and unclear etiology, to establish correlation between symptoms and rhythm abnormalities. |
| (Class IIa, Level of Evidence C): |
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❑Exercise treadmill test is recommended in the presence of chest pain or shortness of breath during exercise and first degree or second degree atrioventricular block during rest ECG |
| (Class IIb, Level of Evidence B): |
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❑EPS is reasonable in second degree atrioventricular block for determining the level of block and benefit of PPM |
| (Class IIb, Level of Evidence C): |
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❑ Carotid sinus massage or pharmacological challenge with atropine or isoproterenol, procainamide can be used in patients with second degree atrioventricular block to determine the level of block and the need for PPM insertion |
Abbreviations:
PPM: Permanent pacemaker;
EPS: Electrophysiologic study
| The above table adopted from 2018 AHA/ACC/HRS Guideline[1] |
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Notes
- Third-degree or complete atrioventricular block suggests no conduction at all from atria to ventricles and may be paroxysmal or persistent and is usually associated with either a junctional or ventricular escape rhythm.
- Complete atrioventricular block may be identified in the setting of AF when the ventricular response is slow (<50 bpm) and regular. Also, junctional rhythm can be seen in complete heart block.
- Electrocardiographic monitoring can be used to identify the changes in QRS morphology such as alternating bundle branch block.
- Treadmill exercise stress testing can be used to identify the development of atrioventricular block and presence of ischemia as a precursor of atrioventricular block.[2]
- Exercise causes vagal withdrawal and increased sympathetic tone leading to improved atrioventricular nodal conduction.
- Exercise may worsen atrioventricular block by increased heart rate in the setting of infranodal atrioventricular block.[3]
- In the presence of bundle branch block or hemiblock on resting ECG, suspicion of episodic high-grade or complete atrioventricular block may raise.
- EPS can also determine the bradycardia due to extrasystole which is similar to atrioventricular block on resting ECG.
- Use of procainamide in patients with bifascicular block was associated with prolonged H-V interval indicating infranodal atrioventricular block. [4]
- Atropine may improve or have no change in atrioventricular conduction block if the block is at the level of the atrioventricular node but may worsen atrioventricular conduction block in the presence of intra-His or distal conduction disease.[5]
- Isoproterenol is useful to determine the underlying pathologic His-Purkinje disease by enhancing atrioventricular nodal and sinus conduction and precipitating heart block with faster heart rates.
- Worsening atrioventricular block with isoproterenol and atropine may be suggestive of infranodal block.
- Improvement of atrioventricular conduction with carotid sinus massage may be observed in patients with infranodal atrioventricular block.[5]
References
- ↑ Kusumoto, Fred M.; Schoenfeld, Mark H.; Barrett, Coletta; Edgerton, James R.; Ellenbogen, Kenneth A.; Gold, Michael R.; Goldschlager, Nora F.; Hamilton, Robert M.; Joglar, José A.; Kim, Robert J.; Lee, Richard; Marine, Joseph E.; McLeod, Christopher J.; Oken, Keith R.; Patton, Kristen K.; Pellegrini, Cara N.; Selzman, Kimberly A.; Thompson, Annemarie; Varosy, Paul D. (2019). "2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society". Circulation. 140 (8). doi:10.1161/CIR.0000000000000628. ISSN 0009-7322.
- ↑ Barold SS (November 2001). "Lingering misconceptions about type I second-degree atrioventricular block". Am J Cardiol. 88 (9): 1018–20. doi:10.1016/s0002-9149(01)01980-4. PMID 11703999.
- ↑ Bakst A, Goldberg B, Schamroth L (September 1975). "Significance of exercise-induced second degree atrioventricular block". Br Heart J. 37 (9): 984–6. doi:10.1136/hrt.37.9.984. PMC 482908. PMID 1191459.
- ↑ Twidale N, Heddle WF, Tonkin AM (October 1988). "Procainamide administration during electrophysiology study--utility as a provocative test for intermittent atrioventricular block". Pacing Clin Electrophysiol. 11 (10): 1388–97. PMID 2462213.
- ↑ 5.0 5.1 Mangiardi LM, Bonamini R, Conte M, Gaita F, Orzan F, Presbitero P, Brusca A (April 1982). "Bedside evaluation of atrioventricular block with narrow QRS complexes: usefulness of carotid sinus massage and atropine administration". Am J Cardiol. 49 (5): 1136–45. doi:10.1016/0002-9149(82)90037-6. PMID 7064840.