the multiple flutter waves that precede the QRS complexes.

The R-R intervals are usually regular unless there is variable conduction through the AV node. The most common

presenting rate is - 1 50 bpm and occurs when the flutter

waves are conducted through the AV node in a 2:1 ratio.

In addition to atrial flutter with a variable block, atrial

fibrillation (AF) and multifocal atrial tachycardia (MAT)

represent the irregular narrow QRS complex tachycardias.

AF can be identified by irregular R-R intervals without

discernible P waves. Although MAT is often confused with

AF, the distinction is critical, as the treatment varies markedly. MAT will have varying P wave morphologies and

irregular P-R and R-R intervals, but unlike AF, P waves will

precede each QRS. MAT is most common in patients with

underlying pulmonary disease, and as there is no specific

cardiac treatment. Focus on addressing the underlying

lung pathology.

Wide complex tachycardias typically require more

emergent intervention than their narrow complex coun ­

terparts and are often encountered in the unstable or "coding" patient. Besides the aforementioned SVT with

aberrancy, VT and ventricular fibrillation (VF) are the

remaining possibilities. VT presents with a rate > 1 20 bpm,

QRS intervals > 1 20 msec, and no discernible P waves.

Torsade de pointes is a unique subset of polymorphic

VT that features a beat to beat variation in QRS morphology with a progressive twist in QRS axis. This condition

usually arises from abnormal ventricular repolarization.

TREATMENT

Address patient airway, breathing, and circulation (ABCs),

provide supplemental 02, ensure adequate peripheral N

access, and initiate continuous cardiac monitoring. Tailor

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Figure 1 6-4. A. Sinus tachycardia. B. Supraventricu lar tachycardia. C. Atrial flutter. D. Atrial fibril lation.

E. Mu ltifoca l atrial tachycardia. F. Ventricular tachycardia. G. Ventricular fibril lation. (B., F. Reproduced with permission

from Ferry DR. Basic Electrocardiography in Ten Days. New York: McGraw-Hill, 2001 . E., G. Reproduced with

permission from Tintinalli JE, Kelen GO, Stapczynski JS. Emergency Medicine: A comprehensive study guide. 6th ed.

New York: McGraw-Hill, 2004.)

the remammg treatment to the patient's underlying

rhythm.

� Bradydysrhythmias

Unstable patients require immediate intervention. Treat those

who are unstable with IV doses of atropine (0.5-1.0 mg) and

epinephrine (0.3-0.5 mg over 2-3 minutes) if refractive.

Initiate transcutaneous pacing and consider placement

of an introducer catheter into the internal jugular or

subclavian vein for transvenous pacing in all patients

who fail to respond. Catecholamine infusions (eg, dopamine)

may be necessary to maintain an adequate HR and blood

pressure.

Whereas second-degree AV block Mobitz type I

typically requires no specific treatment, Mobitz type II and

third-degree heart block require emergent intervention.

Place transcutaneous pacer pads on the chest and initiate

pacing in those that become unstable. To do so, set your