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Dysrhythmias

Marianne Haughey, MD

Key Points

• Qu ickly address airway, breath ing, and circu lation

(the ABCs), provide supplemental 02, secure intravenous access, and in itiate continuous cardiac monitoring.

• Rapidly disti nguish between stable versus unstable

presentations, as unstable patients requ ire immediate

intervention.

INTRODUCTION

The recognition of dysrhythmia is an essential skill for all

emergency physicians, as patients presenting with dysrhythmias are relatively common and have the potential

for rapid hemodynamic deterioration. Clinically, dysrhythmias are classified as stable or unstable based on the

presence or absence of adequate end-organ perfusion

(ie, systemic hypotension, cardiac ischemia, pulmonary

edema, or mental status changes). Dysrhythrnias are fur ­

ther divided by their rate into either bradydysrhythrnias

(heart rate [HR] <60) or tachydysrhythmias (HR >100).

An additional subset of dysrhythmia, atrioventricular

blocks, can present with any HR and represent a malfunction in electrical conduction between the sinoatrial (SA)

node, atrioventricular (AV) node, and bilateral ventricles.

A thorough understanding of the origins of normal cardiac rhythm and electrical conduction is essential to properly comprehend cardiac dysrhythmia. Normal cardiac

conduction originates in the SA node and conducts through

the atria to the AV node. In the majority of patients, the AV

node is the only site where electrical signals can transmit

between the atria and ventricles and therefore functions as

the ultimate "gatekeeper" to the ventricles. Impulses then

travel sequentially from the AV node to the bundle of His,

the right and left bundle branches, the Purkinje fibers, and

ultimately the ventricular myocardium.

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