ECG Lecture: Sinus arrest, sinoatrial exit block, AV block and escape rhythms
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The document outlines various cardiac conduction issues, including sinus arrest, sinoatrial exit block, and various degrees of atrioventricular (AV) block. It describes the definitions, characteristics, and potential symptoms associated with each condition, as well as how to identify them through electrocardiogram (ECG) readings. Additionally, it discusses escape rhythms and provides resources for further visual understanding of the concepts presented.
ECG Lecture: Sinus arrest, sinoatrial exit block, AV block and escape rhythms
- 1. Sinus arrest, Sinoatrial exit block, AV blocks, Escape Rhythms Dr. Michael-Joseph F. Agbayani, MD FPCP FPCC @HeartRhythmMD
- 2. Images used are mine or under a creative commons license or public domain.
- 5. SA node: 60 to 100 SA node: 60 to 100 bpm bpm AV Junction: 40 to AV Junction: 40 to 60 bpm 60 bpm Ventricle: <40 bpm Ventricle: <40 bpm
- 8. Sinoatrial Exit Block • Sinus node still firing • Impulse fails to conduct beyond SA node • Degrees – First degree SA exit block – Second degree SA exit block (Type 1 and type 2) – Third degree SA exit block
- 9. First degree sinoatrial block • First degree – Delay in conduction of sinus impulse – Not evident in a surface ECG
- 10. Second degree sinoatrial block • Intermittent failure of the sinus impulse to exit the node • Type 1 – Progressive delay in sinus impulse resulting in non-conducted impulse – Group beating (Wenckebach periodicity)
- 11. Second degree sinoatrial block type 1
- 12. Second-degree sinoatrial block • Type 2 – Failed conduction of sinus impulse without progressive prolongation of sinoatrial conduction time – Pause is a multiple of baseline P-P interval
- 14. Third-degree sinoatrial block • None of the sinus node impulses are able to exit the node • Absence of p waves • Indistinguishable from sinus arrest
- 15. Sinus Pause / Sinus Arrest • Sinus node doesn’t fire • P-P interval of the pause not a multiple of the baseline P-P interval • Usually said to be abnormal if > 3 seconds
- 18. First degree AV block • • • • PR interval is > 200 ms and is constant Each p wave is followed by QRS complex Marked first degree is >300 ms May be symptomatic
- 20. Second Degree AV Block • • • • One non-conducted p wave Mobitz Type 1 (Wenckebach Block) Mobitz Type 2 2:1 AV block
- 21. Mobitz Type 1 (Wenckebach) • Gradual prolongation of PR interval until nonconducted p wave • RP-PR reciprocity • Lengthening of the PR interval at progressively shorter decrements • Progressively shorter R-R intervals and group beating • Shortening back to baseline PR interval after the blocked cycle
- 24. Mobitz Type 2 • No change in PR before non-conducted P wave • Usually associated with His-Purkinje disease
- 28. 2:1 AV block • Second degree AV block • Every other beat is conducted • PR interval in conducted beats is usually constant
- 29. 2:1 AV block • Classifying into Mobitz Type 1 or type 2 is discouraged • Clues to level of block – Narrow vs wide complex – Long or short PRs in conducted beats – PR and RP relationship – Presence of Mobitz Type 1 block – Response to Atropine or exercise
- 30. 2:1 AV block
- 32. High Grade AV Block • At least 2 consecutive non-conducted P waves (3:1 AV Block) • Also called “advanced second-degree heart block” • Look at the PR interval of conducted beats: should be constant
- 33. 4:1 AV block
- 34. 3rd Degree or Complete Heart Block • None of the P waves are conducted • P waves and QRS complexes occur independently of each other • R-R intervals are usually regular (junctional or ventricular escape rhythm)
- 35. SA node: 60 to 100 SA node: 60 to 100 bpm bpm AV Junction: 40 to AV Junction: 40 to 60 bpm 60 bpm Ventricle: <40 bpm Ventricle: <40 bpm
- 37. • R-R intervals are usually regular (escape rhythm) • “PR” intervals are not constant / no pattern • Escape rhythm can be junctional or ventricular
- 38. Escape Rhythms • Atrial escape rhythm (<60 bpm) – P wave morphology abnormal • Junctional rhythm (40 to 60 bpm) – Narrow QRS – Retrograde P waves shortly before or after QRS, if any • Ventricular rhythm (<40 bpm) – Wide, “bizarre” QRS complexes
- 40. SA node: 60 to 100 SA node: 60 to 100 bpm bpm AV Junction: 40 to AV Junction: 40 to 60 bpm 60 bpm Ventricle: <40 bpm Ventricle: <40 bpm
- 44. Images • • • • • • • • • • • Heart image with conduction system: Public Domain image from Gray’s Anatomy QRS complex: Public Domain image from Wikipedia user http://en.wikipedia.org/wiki/User:Agateller Road Block sign: http://en.wikipedia.org/wiki/File:Road_block.jpg Traffic: http://en.wikipedia.org/wiki/File:Traffic_jam_on_Phu_Nhuan_district.JPG Sinoartial exit block: http://commons.wikimedia.org/wiki/User:Jer5150 First degree AV block: http://www.flickr.com/photos/popfossa/ Second Degree AV block Mobitz Type 1: http://commons.wikimedia.org/wiki/User:Jer5150 Mobitz type 2 and 2:1: http://commons.wikimedia.org/wiki/User:Jer5150 Complete heart block: http://commons.wikimedia.org/wiki/User:Jer5150 Complete heart block strip: http://en.wikipedia.org/wiki/User:MoodyGroove Junctional rhythm: http://www.flickr.com/photos/nottinghamvets/
- 45. Images • • • • • • • • Sinus pause: http://commons.wikimedia.org/wiki/User:Stevenfruitsmaak Mobitz Type 1 with escape: Michael Rosengarten BEng, MD.McGill (ecgpedia.org) SCT with Pause: Michael Rosengarten BEng, MD.McGill (ecgpedia.org) Mobitz type 1 and type 2 strips: Munther Homoud, M.D. (http://ocw.tufts.edu/) Mobitz Type II: http://lifeinthefastlane.com/author/edward-burns/ High Grade AV block: http://lifeinthefastlane.com/author/edward-burns/ Ventricular Escape rhythm: http://lifeinthefastlane.com/author/edwardburns/ Fixed ratio blocks: http://lifeinthefastlane.com/author/edward-burns/
- 46. SA exit block, Sinus Arrest, AV Blocks and Escape Rhythms ECG EXERCISE
- 56. Images • • • • • • • • • First Degree AV block: http://www.flickr.com/photos/popfossa/ 4:1 AV block: http://www.flickr.com/photos/popfossa/ Mobitz type 1: http://www.flickr.com/photos/popfossa/ First Degree AV block: http://www.flickr.com/photos/popfossa/ Type II Sinoatrial exit block: http://lifeinthefastlane.com/author/edward-burns/ Mobitz type 1: http://lifeinthefastlane.com/author/edward-burns/ Complete Heart Block; http://lifeinthefastlane.com/author/edward-burns/ Sinus arrest: http://lifeinthefastlane.com/author/edward-burns/ High grade Av block and Mobitz Type 2: http://lifeinthefastlane.com/author/edward-burns/
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