Lesson V (cont) - ECG Rhythm Abnormalities

Lesson V (cont) Introduction to ECG Rhythm Analysis

Frank G. Yanowitz, MD
Associate Professor of Medicine
University of Utah School of Medicine

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Things to Consider When Analyzing Arrhythmias

Arrhythmias may be seen on 12-lead ECGs or on strips of one or more leads. Some arrhythmias are obvious at first glance and don't require intense analysis. Others, however, are more fun! They require detective work, i.e., logical thinking based on a knowledge of cardiac electrophysiology. The analysis should begin with identifying characteristics of impulse formation (if known) as well as impulse conduction. Here are some things to think about:

Descriptors of impulse formation (i.e. the pacemaker)

Descriptors of impulse conduction (i.e., how it moves through the heart)

1. Descriptors of impulse formation

(i.e. the pacemaker or region of impulse formation)

Sinus Node (e.g., sinus tachycardia)

Atria (e.g., PAC)

AV junction (e.g., junctional escape rhythm)

Ventricles (e.g., PVC)

Accelerated - faster than expected (e.g., accelerated junctional rhythm @ 75bpm)

Slower than expected (e.g., marked sinus bradycardia @ 40bpm)

Normal (e.g., junctional escape rhythm)

Regular (e.g., PSVT)

Regular irregularity (e.g., ventricular bigeminy)

Irregular irregularity (e.g., atrial fibrillation or MAT)

Irregular (e.g., multifocal PVCs)

Active onset (i.e., begins prematurely as with PAC or PVC)

Passive onset (e.g., ventricular escape beat or rhythm)

2. Descriptors of impulse conduction

(i.e., how abnormal rhythm conducts through the heart)

Antegrade (forward) vs. retrograde (backward) conduction

Conduction delays or blocks: i.e., 1^st, 2^nd (type I or II), 3^rd degree blocks

Sites of potential conduction delay

Sino-Atrial (SA) exit block (can only recognize 2^nd degree SA block on ECG)
Intra-atrial delay (usually not recognized)

AV conduction delays (common)

IV blocks (e.g., bundle branch or fascicular blocks)

Now let's explore some real rhythm abnormalities.....

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