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ECG Interpretation. Chapter 22. ECG Interpretation. Axis Hypertrophy Blocks Infarct Ischemia. Rate Atrial rate: PP interval Ventricular rate: RR interval Rhythm P wave PR interval QRS voltage (height) width. Standardization. Standardization mark
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ECG Interpretation Chapter 22
ECG Interpretation Axis Hypertrophy Blocks Infarct Ischemia • Rate • Atrial rate: PP interval • Ventricular rate: RR interval • Rhythm • P wave • PR interval • QRS • voltage (height) • width
Standardization • Standardization mark • 10 mm vertical deflection = 1 mVolt
Rate • Ventricular rate (heart rate) • RR interval • Atrial rate • PP interval • 3rd degree AV block
Rhythm • Sinus rhythm - consistent P waves • Atrial rhythm - irregular P waves • Junctional/Nodal rhythm - no P waves, late P waves, or inverted P waves • Ventricular rhythm - no P waves, wide QRS
AV Junctional Rhythms • Retrograde P waves immediately preceding the QRS complexes in aVR and II. • Retrograde P waves immediately following the QRS complexes • Absent P waves
ECG Waves • P wave • atrial depolarization • ≤ 2.5 mm in amplitude • < 0.12 sec in width • PR interval (0.12 - 0.20 sec.) • time of stimulus through atria and AV node • prolonged interval = first-degree heart block
P wave • Tall = RAE • Wide = LAE
PR Interval • Long PR interval = first degree AV block • Short PR interval = WPW • Short PR interval with inverted P waves = ectopic atrial or junctional pacemaker
Wolff-White-Parkinson • Wide QRS • due to early depolarization • not due to a delay in depolarization • Shortened PR interval • Upstroke QRS complex is slurred; delta wave
ECG Waves • QRS • width 0.12 second or less
Normal QRS V6? V6? V1? V1? Fig. 4-6
Normal Q waves • Septal r wave • Septal q wave
Q Waves • Abnormal if wider than 0.04 sec • Leads I, II, III, aVf or leads V3 - V6. • Greater than 25% of the R wave • Note: Not all Q waves are abnormal, Not all Q waves are the result of MI.
QRS Width • Wide • RBBB or LBBB • Premature ventricular beats • WPW
QRS Voltage • RVH • LVH
ST Segments • J point: • end of QRS wave • beginning of ST segment • ST segment • beginning of ventricular repolarization • normally isoelectric (flat) • changes, elevation or depression, may indicate pathological condition
Subendocardial Ischemia • ST segment depression criteria • 1 mm or more • horizontal or downward • lasts 0.08 seconds • depression of only the J point with rapid upward sloping are considered normal.