EKGs: A Quick Review

Rate:

Count the # of large boxes between QRS complexes300-150-100-75-60-50 (bpm)

Rhythm:

P waves are present in all leads and upright in I and aVFNormal sinus rhythm

Look for missing P waves or QRS complexes as clues for dysrhythmias

Irregular rhythm, missing P waves, irregular QRS responseatrial fibrillation

Axis:

Upright (positive) QRS in leads I and aVFNormal axis

I is positive and aVF is negative Left axis deviation

I is negative and aVF is positiveRight axis deviation

P waves:

Tall/peaked p waves in limb or precordial leadsR atrial hypertrophy

Broad/notched p waves in limb leadsL atrial hypertrophy

“Sawtooth” appearance of p waves, atrial rate 25-350 bpm and atrioventricular conduction ratio 2:1 or 4:1atrial flutter

3 or more P wave morphologiesmultifocal atrial tachycardia

PR interval: normal=0.12-0.20 seconds

Short PRassociated with Wolf-Parkinson-White syndrome (WPW)

Long PR, > 0.20 seconds 1st degree heart block

PR interval lengthens until a QRS is dropped2nd degree block (Mobitz type I/Wenckebach)

Constant PR with QRS dropped at constant interval2nd degree block (Mobitz type II)

Complete AV dissociation3rd degree block

QRS complex: normal  0.12 seconds

Widened QRSbundle branch block (BBB)

Mnemonic for BBB: WiLLiaM MoRRoW

W pattern of QRS in V1-V2 and M pattern of QRS in V3-V6LBBB

M pattern (RSR’) of QRS in V1-2 and W pattern of QRS in V3-V6RBBB

Slurred upstroke of QRS (delta wave)WPW

R1>15mm, RI, II or aVF >20mmLeft ventricular hypertrophy

RV1>7mm, R axis deviationRight ventricular hypertrophy

ST segment:

T waves:

Tall, peaked T waves in precordial leads--> hyperkalemia

Sources:

Taylor, George J. 150 Practice ECGs: Interpretation and Review, 1997

Thaler, Malcom S. The Only EKG Book You’ll Ever Need, 4^th ed

Category: Cardiology Notes