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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.
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Understanding ECG’s 2nd year student module John N. Hamaty D.O. FACC, FACOI
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 depolarization
ECG Interpretation • Rate • Rhythm • Axis • Intervals • Acute st-t changes • Age indeterminate events • R wave progression