EKG Basics

EKG graph paper:

• Small square = 1 mm or 0.04 sec

• Large square = 5 mm or 0.2 sec

Normal values:

· Heart Rate: 60 to 100 beats/min

· P Wave: width < 3 small boxes (0.12 sec) and height < 2.5 small boxes (0.25 mv)

· PR Interval: 3 to 5 small boxes (0.12 to 0.20 sec)

· QRS duration: < 3 small boxes (0.12 sec)

· T wave: < 5 small boxes in limb leads, < 10 small boxes in precordial leads

Heart rate estimation:

· Regular rhythm: Division of 300 by number of large squares between consecutive R waves

· Irregular rhythm: Number of QRS complexes (R waves) on the EKG strip x 10

Rhythm analysis:

· Regular rhythm: Interval between R waves is constant or varies by < 1.5 small boxes

· Irregular rhythm: Interval between R waves varies by > 1.5 small boxes

Systematic Interpretation:

· Read EKG strip from left to right

· Seven step approach

o Calculate heart rate

o Check rhythm

o Assess P Wave

• Present or absent?

• Occurring regularly or irregularly?

• P wave before each QRS or not?

• Shape

o Measure PR interval

• Beginning of P wave to onset of QRS complex

o Measure QRS duration

• Beginning of Q wave to end of S wave

o Look at ST segment

• Elevated, depressed or isoelectric to TP segment?

o T waves

• Tall, inverted or biphasic?

Sinus Rhythms (Impulse originates in SA node; normal P waves, normal QRS): <=click link

· Normal sinus rhythm

· Sinus bradycardia

· Sinus tachycardia

· Sinus arrhythmia

· Sinus pause/arrest

Atrial Rhythms: (Impulse originates in atrial tissue; +/− P waves, Normal QRS): <=click link

· Atrial flutter

· Atrial fibrillation (AFib)

· Supraventricular tachycardia (SVT)

· Premature atrial complexes (PACs)

· Multifocal atrial tachycardia (MAT)

Ventricular Rhythms (Impulse originates in ventricles; no P waves, Wide QRS): <=click link

· Ventricular tachycardia (VT)

· Premature ventricular complexes (PVCs)

· Torsades de Pointes

· Ventricular fibrillation (VFib)

Conduction blocks: <=click link

· First degree AV block

· Second degree AV block:

o Mobitz type I

o Mobitz type II

· Third degree AV block

· Right bundle branch block

· Left bundle branch block

EKG in myocardial infarction (MI): <=click link

· Criteria

· Contiguous leads

· STEMI evolution

· Old MI