ECG Overview and Interpretation NUR 351/352 Professor Diane E. White RN MS CCRN

MEASUREMENTS 1.ECG PAPER Horizontal boxes measure time and the vertical boxes measure voltage or amplitude Small boxes =.04 seconds Large boxes =.20 second or 5 small boxes Hatch marks at top of paper = 3 seconds usually want a 6 second strip to analyze Low voltage is represented by small waves & vice versa Small waves from artria and large from ventricles

Waveforms & Intervals ** a flat baseline called isometric line means neither –/+ ** any waveform above the line is positive and below is negative P Wave: indicates atrial depolarization; upright in leads I and II PR Interval: connects P wave & QRS complex; measured from beginning of p wave where + deflection begins to where QRS begins; time it takes impulse to depolarize atria & travel to AV node and Bundle of His; normal seconds

QRS Complex: ventricular depolarization; Q wave is negative deflection after the p wave; the first positive following the p wave is the R wave, normally tall and positive in lead II; the S wave is a negative waveform that follows the R wave QRS Interval: measured from beginning to end of QRS complex; first deflection after the p wave is the beginning of the QRS complex and measured until final deflection returns to baseline; normally less than.12 seconds T Wave: represents ventricular repolarization and follows the QRS complex ST Segment: usually isoelectric; may be elevated or depressed

INTERPRETATION OF ECG 1.Rhythmicity: is the rate regular or irregular? 2.Rate: atrial (p waves) & ventricular rates (R waves) methods to determine rate: The rule of /#small boxes b/w 2 waves The rule of 10 - # of P or R waves in 6 second strip multiplied by 10 The rule of / # large boxes b/w 2 waves 3.Location: is there a P wave for every QRS? 4.Intervals: does the PR = & the QRS less than.12?

PRACTICE PRACTICE PRACTICE! MEMORIZE THE RULES FOR VARIOUS DYSRHYTHMIAS PRACTICE, PRACTICE, PRACTICE!

Normal Sinus

Sinus Bradycardia

Sinus Tachycardia

Sinus Arrhythmia