ECGSysInterp1 - Systematic In terpretation of the 12-lead...

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Systematic Interpretation of the 12-lead ECG A. Analysis of Basic Parameters 1. Rate and Rhythm a. Normal P waves (lead II) followed by QRS? b. Regular Rate? Estimate: Find peak that lines up with thick line and count 300-150-100-75-60- 50 Exact calc: HR (beats/min) = 60 (sec/min) / RR (sec/beat) 1 box on ECG = 1mm = 0.04s Normal range = 60-100 (beats/min) Brady (<60/min): can be physiological; in healthy athletes Tachy (>100/min): can be physiological; due to increased sympathetic tone Arrhythmia: variation in RR interval >0.16 seconds. Most common form is respiratory sinus arrhythmia ( rate on inspiration) 2. Time Intervals a. RR interval = whole cycle from R wave to R wave = ?mm x 0.04 = X sec b. PR interval = P wave + PR segment Normal range = 0.12 – 0.20s Abnormal indicates 1 st degree AV block (delay in AV conduction) c. QRS interval = width of QRS complex Range: 0.09 is normal, 0.10-0.11 is unclear, 0.12 is abnormally prolonged Prolonged QRS (wider than 3 little boxes) indicates… decreased conduction velocity in ventricular myocytes i. severe hyperkalemia ii. class 1 antiarrhythmic drugs Asynchrony of ventricular depolarization
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i. Ventricular ectopic beats (see below) ii. Bundle branch block (see below to diagnose) d. QT interval = QRS interval + ST segment + T wave Range varies with HR, so use corrected QTc QTc = QT/ RR Normal QTc range = 0.35-0.44 e. Conduction disturbances 1 st degree AV block: delay in AV conduction Prolonged PR interval (>0.20 sec) Each P wave is followed by QRS complex 2 nd degree AV block: intermittent interruption in AV conduction Some P waves are not followed by a QRS complex; fraction of sinus impulses that reach the ventricle can be described by the conduction ratio
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ECGSysInterp1 - Systematic In terpretation of the 12-lead...

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