Understanding ECG’s 2 nd year student module John N. Hamaty D.O. FACC, FACOI

Practical Electrocardiography (9 th edition) Galen S. Wagner

The Electrocardiogram Gold standard for diagnosing rhythms Snap shot in time Detect coronary artery distribution of event

Vectors Anything going toward a lead is positively deflected Anything going away from a lead is negatively deflected (MI, position, lead placement)

P wave The first wave on the ECG Represents atrial activation Smooth Duration is less than 0.12 sec Amplitude is less than 0.25 mV Upright inferiorly

Q wave First negative deflection Normally very small in deflection If prominent, consider infarction

R Waves Precordial leads provide a panoramic view of electrical activity of thinner right ventricle across the thicker left ventricle. R wave amplitude increases from V1-V4 or V5

S Waves Large in V1 and V2 then progressively smaller to V6

T Wave Rounded symmetric Follow direction of QRS Represents myocardial repolarization

ECG Interpretation Rate Rhythm Axis Intervals Acute st-t changes Age indeterminate events R wave progression

End of ECG Part I