Ectopic atrial rhyghms seen in
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Here is a complete, textbook-sourced answer on ectopic atrial rhythms:
Ectopic Atrial Rhythms
Definition
An ectopic atrial rhythm is a nonsinus atrial rhythm arising from a single focus outside the sinoatrial (SA) node, producing a single, consistent P wave morphology that differs from normal sinus P waves (i.e., P waves are not upright in leads I, II, and III). Rate is typically <100 bpm but faster than sinus rhythm. When the rate exceeds 100 bpm, it is called ectopic atrial tachycardia.
A wandering atrial pacemaker is a related condition with at least three distinct P wave morphologies at rates between 50-100 bpm, indicating multiple shifting ectopic foci.
- Goldman-Cecil Medicine, p. 566; Textbook of Family Medicine 9e, p. 720
Seen In (Clinical Associations)
| Category | Specific Causes |
|---|---|
| Drug toxicity | Digitalis (digoxin) toxicity - a classic cause |
| Pulmonary/Lung disease | COPD, cor pulmonale, hypoxia, hypercapnia |
| Heart disease | Rheumatic heart disease, cardiomyopathy, mitral valve disease, hypertrophic cardiomyopathy |
| Electrolyte disturbance | Hypokalemia, hypomagnesemia |
| Exogenous stimulants | Caffeine, tobacco, alcohol excess, sympathomimetic drugs |
| Structural/extrinsic | Extrinsic compression of the atrium by adjacent abnormal structures |
| Normal variant | Can be seen in otherwise healthy individuals - often asymptomatic |
| Sick sinus syndrome | SA node abnormally susceptible to suppression by ectopic atrial activity; ectopic rhythms emerge as escape |
- Textbook of Family Medicine 9e, p. 719-720; Bradley and Daroff's Neurology in Clinical Practice
ECG Findings
The P wave morphology is abnormal (not upright in limb leads I, II, III); P-P intervals are approximately equal; QRS is typically narrow unless aberrant conduction is present.
ECG: Ectopic atrial rhythm at 85 beats/min with negative P waves in lead II, replaced by slower sinus rhythm (upright P waves) mid-strip, then returning at the end. - Textbook of Family Medicine 9e, Fig. 27-39
Clinical Features
- Usually asymptomatic - often incidentally found on routine ECG or Holter monitoring
- Rarely, a very slow ectopic rhythm causes fatigue
- Incessant rapid ectopic atrial tachycardia can lead to tachycardia-induced (rate-related) cardiomyopathy
- In Wolff-Parkinson-White (WPW) syndrome or severe structural heart disease (e.g., HCM), a supraventricular arrhythmia can rarely precipitate cardiac arrest
Key Distinction from PACs
Multiple sequential PACs can mimic ectopic atrial rhythm. A consistent P wave morphology and regular P-P intervals distinguish a sustained ectopic atrial rhythm from sequential PACs. - Goldman-Cecil Medicine, p. 566
Treatment
- Asymptomatic: No specific treatment required
- Symptomatic/rapid: Beta-blockers or calcium channel blockers to reduce ectopy and slow ventricular response
- Incessant tachycardia with cardiomyopathy: Class Ia, Ic, or III antiarrhythmics; catheter ablation may be needed
- Very slow ectopic rhythm causing fatigue: Atrial pacing at a rate faster than the ectopic rhythm
Rsr pattern in v1 v2
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Here is a complete, textbook-sourced breakdown of the RSR' pattern in V1-V2:
RSR' Pattern in V1-V2
The RSR' (also written rSR', rsR', or "M-shaped" / "rabbit ears") pattern in leads V1-V2 reflects delayed right ventricular activation - the terminal QRS vector is oriented to the right and anteriorly, producing the characteristic double-peak in V1.
Causes (Most to Least Common)
1. Normal Variant / Incomplete RBBB
- An RSR' with QRS < 120 ms and R' amplitude NOT greater than the initial R wave = incomplete RBBB, which is a normal finding in young individuals and athletes
- Right ventricular conduction delay (RVCD) is more frequent in people under 21 years and in athletes
- Does not necessarily progress to complete RBBB
- Pfenninger and Fowler's Procedures for Primary Care, p. 4340
2. Complete Right Bundle Branch Block (RBBB)
- QRS ≥ 120 ms, rSR' in V1, wide terminal S wave in V5-V6
- The terminal QRS vector shifts right and anteriorly due to delayed right ventricular depolarization
- Occurs in:
- No structural disease (most common for RBBB vs LBBB)
- Congenital heart disease - especially atrial septal defect (ASD)
- Acquired heart disease - valvular, ischemic, cor pulmonale, myocarditis
- Trauma to the right bundle
- Harrison's Principles of Internal Medicine 22E, p. 1915; Pfenninger and Fowler, p. 4340
3. Atrial Septal Defect (ASD)
- A classic association - both incomplete and complete RBBB patterns with RSR' in V1 are seen
- Due to right ventricular volume overload from left-to-right shunting
- Fixed splitting of S2 is the clinical clue
- Harrison's 22E; Pfenninger and Fowler
4. Brugada Pattern / Brugada Syndrome
- Type 1 (diagnostic): Coved ST elevation ≥ 2 mm in V1-V2, downsloping, followed by T-wave inversion - the rSR'/Rsr' is part of this pattern
- Type 2: Saddle-back ST elevation with RSR' - not diagnostic alone
- Associated with risk of polymorphic VT/VF and sudden cardiac death in structurally normal heart
- Harrison's 22E - "a Brugada pattern of Rsr' with ST elevation in leads V1 or V2"
5. Right Ventricular Hypertrophy (RVH)
- RSR' in V1 with R' > 15 mm in infants or > 10 mm in children (after 1st year of life)
- Seen in: pulmonary hypertension, COPD, pulmonary valve stenosis, Eisenmenger syndrome
- Tintinalli's Emergency Medicine
6. Pulmonary Embolism (Acute)
- Acute right heart strain can produce transient RSR' or incomplete RBBB in V1
- Part of the S1Q3T3 pattern constellation (though RSR' may appear alone)
- Pfenninger and Fowler: "Any pulmonary disease process can be associated with RVCD, and RVCD can occur acutely with exacerbation of lung disease or pulmonary embolus"
7. Posterior Wall MI
- Posterior MI produces increased R wave in V1-V2 (reciprocal change), which can mimic RSR' morphology
- The R/S ratio in V1 becomes ≥ 1 with ST depression
8. Wolff-Parkinson-White (WPW) - Left-sided Accessory Pathway
- Left-sided pathways produce a dominant R in V1 that can superficially resemble RSR'
- Delta wave and short PR distinguish this
9. Hyperkalemia / Drug Toxicity
- Class Ia antiarrhythmics, tricyclic antidepressants, phenothiazines can slow right ventricular conduction and produce intraventricular conduction delay resembling RBBB pattern
- Harrison's 22E, p. 1916
Quick Memory Summary
| QRS Duration | Pattern | Think of |
|---|---|---|
| < 120 ms, small R' | Incomplete RBBB / RVCD | Normal variant, athlete, ASD, pulmonary disease |
| ≥ 120 ms | Complete RBBB | Organic heart disease, congenital, ischemia |
| RSR' + ST elevation (coved) V1-V2 | Brugada Type 1 | Sudden death risk - refer urgently |
| RSR' + right axis + fixed S2 split | ASD | Echo + bubble study |
| RSR' + acute dyspnea/hypoxia | Acute cor pulmonale / PE | CT-PA / V-Q scan |
Key point from Harrison's 22E: "A distinctive abnormality simulating right bundle branch block with ST-segment elevations in the right chest leads is seen with the Brugada pattern" - this must always be distinguished from benign RBBB.
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