Cardiovascular ECG

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jknell
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209484
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Cardiovascular ECG
Updated:
2013-03-26 16:42:55
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Cardio ECG
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    • Limb leads
    • - → + gives a positive deflection
    • + → - gives a negative deflection
  1. Augmented limb leads
  2. Precordial leads
  3. ECG leads
    anatomical representation, coronary artery responsible
    • Anteroseptal leads: V1, V→ LAD
    • Anteroapical leads: V3, V→ LAD (distal)
    • Anterolateral leads: I, aVL, V5, V6 → CFX
    • Inferior leads: II, III, avF → RCA
    • Posterior: V1, V2 (tall R wave, not Q wave) → RCA
    • P wave: atrial depolarization; atrial repolarization is masked by QRS complex
    • PR interval: conduction delay through AV node (nl < 200 msec)
    • QRS complex: ventricular depolarization (nl <120 msec)
    • QT interval: mechanical contraction of the ventricle
    • T wave: ventricular repolarization; T wave inversion may indicate recent MI
    • ST segment: isoelectric, ventricles depolarized
    • U wave: caused by hypokalemia, bradycardia
  4. Sequence of ECG Interpretation
    • 1. Calibration
    • 2. Rhythm
    •      -Sinus if:
    •           -each P wave is followed by QRS; each QRS is preceded by P wave
    •           -P wave is upright in leads I, II, and III
    •           -PR interval is >0.12 sec (3 small boxes)
    •      -If not, determine type of arrhythmia
    • 3. Heart rate
    •      - Large box: 300-150-100-75-60-50
    •           - (HR = 300/# of large boxes)
    •           - nl, tachycardia, bradycardia
    • 4. Intervals
    •      - PR = 0.12-0.2 sec (3-5 small boxes)
    •      - QRS ≤ 0.10 sec (≤~3 small boxes)
    •      - QT ≤ half the R-R interval, if heart rate is normal 
    • 5. Mean QRS axis
    •      -Nl if QRS is primarily upright in leads I and II (between +90° to -30°)
    •      -abnl: determine axis by isoelectric/perpendicular method
    • 6. P wave abnormalities
    •      -P waves in leads II and V1 for left and right atrial enlargement
    • 7. QRS wave abnormalities
    •      - Left and right ventricular hypertrophy
    •      - Bundle branch block
    •      - pathologic Q waves; what's the anatomica distribution
    • 8. ST segment or T wave abnormalities
    •      - ST elevations:
    •           - ST segment elevation MI
    •           - pericarditis
    •      - ST depression or T wave inversions:
    •           - Myocardial ischemia or non-ST elevation MI
    •           -Usual accompany ventricular hypertrophy or bundle branch blocks
    •           -Metabolic or chemical abnormalities
    • 9. Compare pt's previous ECG
  5. Mean QRS axis
    Normal: -30° to +90°

    • Left axis deviation: more negative than -30°
    • -Inferior wall MI
    • -Left anterior fascicular block
    • -Left ventricular hypertrophy (sometimes)

    • Right axis deviation: more positive than +90°
    • -Right ventricular hypertrophy
    • -Acute right heart strain (e.g. massive pulmonary embolism)
    • -Left posterior fascicular block
    • Right ventricular hypertrophy
    • -R > S in lead V1
    • -Right axis deviation

    *The large R wave of V1 gets progressively smaller from V2 to V3 to V4 etc.
    • Left ventricular hypertrophy
    • -S in V1 + R in V5 or V6 > 35mm 
    • OR
    • -R in aVL > 11mm
    • OR
    • -R in lead I > 15mm
  6. Atrial hypertrophy
    Diphasic P wave (both positive and negative)

    • Right atrial hypertrophy:
    • -initial component of diphasic P wave (in lead V1) is larger
    • *Right atria has the SA node; it gets depolarized first

    • Left atrial hypertrophy:
    • -terminal portion of a diphasic P wave in V1 is large and wide
    • *Mitral stenosis can cause left atrial enlargment
    • *systemic hypertension is the most common cause

  7. Bundle branch block
    • RBBB:
    • -Widened QRS
    • -RSR' in V1 ("Rabbit ears")
    • -Prominent S in V6

    • LBBB:
    • -Widened QRS
    • -Broad, notched R in V6
    • -Absent R and prominent S in V1


  8. STEMI
  9. Digoxin therapy
    • ST "scooped" depression
    • Mild PR prolongation
  10. Hyperkalemia, Severe hyperkalemia, Hypokalemia
    • Hyperkalemia: Peaked T waves
    • Severe hyperkalemia: Flattened P; Widened QRS
    • Hypokalemia:ST depression, flattened T; Prominent U wave
  11. Hypercalcemia, Hypocalcemia
    • Hypercalcemia: Shortened QT interval
    • Hypocalcemia: Prolonged QT interval
    • Torsades de pointes
    • -Ventricular tachycardia, characteriezed by shifting sinusoidal waveforms on ECG
    • -Can progress to V fibrillation
    • *Anything that prolongs QT interval can predispose to torsades de pointes
    • Tx: magnesium sulfate
    • **Congenital long QT syndromes are most often due to defects in cardiac sodium or potassium channels
    • --Can present with severe congenital sensorineural deafness (Jervell and Lange-Nielsen syndrome)
    • Atrial fibrillation
    • Chaotic, erratic baseline (irregularly irregular) with no discrete P waves in between irregularly spaced QRS complexes
    • Atrial stasis → clotting → stroke
    • Tx: rate control, anticoagulation, possible cardioversion
    • Atrial flutter:
    • Rapid succession of identical, back-to-back atrial depolarization waves
    • "Sawtooth" appearance
    • Tx:
    • -pharmacologic conversion to sinus rhythm: class IA, IC, or III antiarrhythmiccs
    • -Rate control: β-blockers or calcium channel blockers
    • Ventricular fibrillation:
    • Completely erratic rhythm with no identifiable waves
    • Fatal arrhythmia without immediate CPR and defibrillation
  12. AV block
    • 1st degree: PR interval is prolonged (>200 msec). Asymptomatic
    • 2nd degree (Mobitz type I): Progressive lengthening of PR interval until a beat is dropped. Usually asymptomatic 
    • 2nd degree (Mobitz type II): Dropped beats that are not preceded by a change in the length of the PR interval. Pathologic, may progress; pacemaker
    • 3rd degree (complete): Atria nd ventricles beat independently of each other. Pathologic; pacemaker
    • First degree AV block
    • Asymptomatic
    • prolonged PR interval
    • 2nd degree
    • Mobitz type I
    • Wenckebach
    • Progressive lengthening of PR interval, until beat is dropped
    • Asymptomatic (usually)
    • 2nd degree 
    • Mobitz type II
    • Abrupt, nonconductant P waves result in pathologic condition
    • Often found as 2:1 block; 2 or more P waves to 1 QRS complex
    • May progress to 3rd degree block
    • Tx: pacemaker
    • 3rd degree (complete)
    • Atreia and ventricles beat independently
    • atrial rate is faster than ventricular rate
    • Tx: pacemaker
    • **Lyme disease can result in 3rd degree heart block
  13. Common bradyarrhythmias
    location
    • SA node:
    • -sinus bradycardia
    • -sick sinus syndrome

    • AV node:
    • -Conduction bocks
    • -Junctional escape rhythm

    • Ventricles:
    • -Ventricular escape rhythm
    • Sick sinus syndrome
    • Presentation: dizziness, confusion, syncope; elderly patients
    • Tx: IV anticholinergic (atropine) or β-adrenergic agents (isoproterenol)
    • *pts susceptible to SVTs: combination is bradycardia-tachycardia syndrome
    • Junctional escape rhythm
    • Arises from the AV node or proximal bundle of His
    • 40-60bpm
    • normal, narrow QRS complex
    • Ventricular escape rhythm
    • Slower rates (30-40bpm)
    • widened QRS complex
  14. Common Tachyarrhythmias
    Location
    • SA node:
    • -Sinus tachycardia

    • Atria:
    • -Atrial premature beats
    • -Atrial flutter
    • -Atrial fibrillation
    • -Paradoxysmal supraventricular tachycardias
    • -Focal atrial tachycardia
    • -Multifocal atrial tachycardias

    • AV node:
    • -Paroxysmal reentrant tachycardias (AV or AV nodal)

    • Ventricles:
    • -Ventricular premature beats
    • -Ventricular tachycardia
    • -Torsades de pointes
    • Ventricular fibrillation
  15. Supraventricular tachyarrhythmias
    Regular vs irregular rhythm
    • Regular rhythm:
    • -Sinus tachycardia
    • -Reentrant SVTs (AVNRT, AVRT)
    • -Focal atrial tachycardia
    • -Atrial flutter

    • Irregular rhythm:
    • -Multifocal atrial tachycardia
    • -Atrial fibrillation
  16. SVT with regular rhythm
    • Sinus Tach:
    • -100-180
    • -normal p waves
    • -atrial may slow in response to carotid massage

    • Reentrant SVTs:
    • 140-250 bpm
    • -P wave: hidden or retrograde
    • -May abruptly terminate with carotid sinus massage

    • Focal atrial tachycardia:
    • 130-250
    • P waves differ from normal
    • AV block may increase; doesn't usually revert with carotid sinus massage

    • Atrial flutter:
    • -180-350
    • -Saw toothed p waves
    • -AV block may increase with carotid sinus massage
    • Atrial premature beats:
    • Atrial focus outside the SA node
    • Common in normal and diseasesd hearts
    • Atrial flutter
    • Rate: 180-350bpm
    • P wave: "saw-toothed"
    • Carotid massage: AV block may increase
  17. Wolfff-parkinson-white syndrome
    • ECG: characteristic delta wave indicates pre-excitation of the ventricles
    • Shortened PR interval
  18. Multifocal atrial tachycardia
    • Irregular rhythm
    • Each QRS is preceded by a P wave
    • P waves vary in morphology
  19. Ventricular tachycardias
    • Monomorphic VTs:
    • -structural abnormality that supports a reentry circuit

    • Polymorphic VTs:
    • -multiple ectopic foci or continually changing reentry circuit

    • Torsades de pointes:
    • -most common cause of polymorphic VT

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