Normal ECG The P wave represents atrial activation the PR interval is the time from onset of atrial activation to onset of ventricular activation. Normal ECG The normal ECG has the following features: P wave - due to atrial depolarization PR interval (due to delayed conduction through the AV node) 0.12 - 0.20 seconds QRS complex - due to ventricular depolarization T wave due to ventricular repolarization ST segment Orientation of the 12 Lead ECG: It is important to remember that the 12-lead ECG provides spatial information about the heart's electrical activity in 3 approximately orthogonal directions: Each of the 12 leads represents a particular orientation in space, as indicated below (RA = right arm LA = left arm, LF = left foot) Bipolar limb leads (frontal plane): Lead I: RA (-) to LA (+) (Right Left, or lateral) Lead II: RA (-) to LF (+) (Superior Inferior) Lead III: LA (-) to LF (+) (Superior Inferior) Augmented unipolar limb leads (frontal plane): Lead aVR: RA (+) to (-) (Rightward) Lead aVL: LA (+) to (-) (Leftward) Lead aVF: LF (+) to (-) (Inferior) Unipolar (+) chest leads (horizontal plane): Leads V1, V2, V3: (Posterior Anterior) Leads V4, V5, V6:(Right Left, or lateral) Right Left Superior Inferior Anterior Posterior Arrive at final diagnoses by critically evaluating each abnormality in relationship to all others and any available clinical data. Evaluate each P wave, QRS, ST segment, T wave and U wave in the following lead order: I and aVL then II, III, and aVF then V1, V2, V3, V4, V5 and V6 (beginning with R wave progression), localizing and grouping all abnormalities. Consider the diagnostic possibilities suggested by abnormalities found, but do not make final diagnoses yet (except for left bundle branch block, which makes further interpretation impossible). A Sequential Approach to Reading EKG’s:Ī Sequential Approach to Reading EKG’s: 3. At each step consider the two main questions of rhythm interpretation: where has impulse formation occurred and how has conduction proceeded. For all rhythms, look for and evaluate P waves in the underlying rhythm first, and then in relation to any additional or dropped beats Look at QRS complex morphology, first in the underlying rhythm and then in any additional beats. For irregular rhythms determine if the rhythm is completely irregular ('irregularly irregular') or if the irregularity is caused by additional or dropped complexes superimposed on an underlying regular rhythm. Determine if the rhythm is regular or irregular. If this is not available, look at 'pieces' of the rhythm in each lead (II and V1 generally have prominent P waves). It is best to evaluate rhythm on a rhythm strip. Michael JacobsonĪ Sequential Approach to Reading EKG’s: Gain familiarity with the 'normal' EKG.

Electrocardiography Dr.S Kesanakurthy Reviewed by Dr.

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