Second 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]
Overview
Electrocardiographic monitoring can be used to identify the changes in QRS morphology such as alternating bundle branch block in the presence of atrioventricular conduction abnormalities. Also,Treadmill exercise stress testing may be diagnostic to differentiate that 2:1 atrioventricular block is Mobitz type I or II in some cases or identify the presence of infranodal disease. In addition, EPS may be helpful to determine the anatomic site of block in mobitz type 2 atrioventricular block including atrioventricular node, intra-His, or infra-His. Worsening atrioventricular block with isoproterenol and atropine may be suggestive of infranodal block. However, improvement of atrioventricular conduction with carotid sinus massage may be observed in patients with infranodal atrioventricular block.
Other diagnostic studies
| The above table adopted from 2018 AHA/ACC/HRS Guideline[1] |
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Notes
- Electrocardiographic monitoring can be used to identify the changes in QRS morphology such as alternating bundle branch block.
- Mobitz type1 atrioventricular block is much more associated with narrow QRS morphology and mobitz type 2 atrioventricular block usually has wide QRS morphology'
- In some cases, mobitz type 1 atrioventricular block and narrow QRS complex contributes with infranodal atrioventricular block.
- Event monitors, worn for 30 to 90 days, and ICDs, which can be left in place for >2 years, tend to have greater diagnostic results than 24-48 hour ambulatory electrocardiographic monitoring.[2]
- Treadmill exercise stress testing can be used to identify the development of atrioventricular block in the presence of ischemia.[3]
- Treadmill exercise stress testing may be diagnostic to differentiate that 2:1 atrioventricular block is Mobitz type I or II or identify the presence of infranodal disease.[4]
- Commonly, high-degree atrioventricular block is generally considered to be intra- or infra-Hisian.
- In rare cases (at night, with accompanying sinus slowing), high-grade AV block is due to increased vagal tone especially in the presence of narrow QRS complex.
- 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.[4]
- In the presence of bundle branch block or hemiblock on resting ECG, suspicion of episodic high-grade or complete atrioventricular block may raise.
- Electrophysiologic study may be helpful to determine the anatomic site of block in mobitz type 2 atrioventricular block including atrioventricular node, intra-His, or infra-His.[5]
- The site of block In 70% of cases of 2:1 atrioventricular block with bundle branch block is infranodal block, however, 15% to 20% of these patients can have block in the atrioventricular node.[6]
- EPS can also determine the bradycardia due to extrasystole which is similar to atrioventricular block on resting ECG.
- Carotid sinus massage is useful to determine the type of atrioventricular block When 2:1 atrioventricular block or Mobitz type I atrioventricular block in the setting of a wide QRS complex can not be differentiated on resting ECG.
- Use of procainamide in patients with bifascicular block was associated with prolonged H-V interval indicating infranodal atrioventricular block. [7]
- 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.[8]
- 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.[8]
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.
- ↑ Sivakumaran S, Krahn AD, Klein GJ, Finan J, Yee R, Renner S, Skanes AC (July 2003). "A prospective randomized comparison of loop recorders versus Holter monitors in patients with syncope or presyncope". Am J Med. 115 (1): 1–5. doi:10.1016/s0002-9343(03)00233-x. PMID 12867227.
- ↑ 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.
- ↑ 4.0 4.1 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.
- ↑ Fisher JD (1981). "Role of electrophysiologic testing in the diagnosis and treatment of patients with known and suspected bradycardias and tachycardias". Prog Cardiovasc Dis. 24 (1): 25–90. doi:10.1016/0033-0620(81)90026-8. PMID 7019962.
- ↑ Zipes DP (September 1979). "Second-degree atrioventricular block". Circulation. 60 (3): 465–72. doi:10.1161/01.cir.60.3.465. PMID 378457.
- ↑ 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.
- ↑ 8.0 8.1 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.