0071643192.pdf

Is the rhythm regular or irregular?

Regular rhythms include:

■ Sinus
■ Some AV-node blocks (first-degree AV block, second-degree AV block with
fixed conduction.)
■ Paroxysmal supraventricular tachycardia (PSVT)
■ Atrial flutter with fixed block
■ Atrial tachycardia
■ Ventricular tachycardia

Irregular rhythms include:

■ Atrial fibrillation
■ Atrial flutter with variable block
■ Multifocal atrial tachycardia with or without conduction blocks
■ Some AV-node blocks (Wenckebach, second-degree AV block with variable
conduction)

Are P waves present? If so, are they associated with QRS complexes?

The presence or absence of P waves as well as whether or not they conduct is
important to understanding the origin of the rhythm.

Once a rhythm is diagnosed, specific therapy may be instituted.

A 55-year-old male presents to the ED with acute onset of chest pain,

shortness of breath, and diaphoresis. His initial ECG shows acute ST eleva-

tion in the anterior leads. You initiate ACS protocols and activate the cath

lab. Shortly thereafter he complains of lightheadedness. The monitor now shows

third-degree AV block with a ventricular escape rhythm at 35 bpm. What should

you do first?

Anterior MI is associated with infranodal conduction damage that is often

permanent. Transcutaneous pacing should be initiated and the patient prepped

for transvenous pacer placement. Atropine may actually WORSEN the conduc-

tion ratio, and therefore should notbe used in this setting. Isoproterenol may

also be used to increase the ventricular rate.

CONDUCTIONABNORMALITIES

Conduction abnormalities can occur above the atrioventricular node (supran-
odal blocks), at the level of atrioventricular conduction, or within the ventricles
(intraventricular blocks). Intraventricular blocks are described in detail in the
section “ECG Essentials” in Chapter 2.

SUPRANODALBLOCKS

■ Sinoatrial block
■ Intra-atrial block

ATRIOVENTRICULAR(AV) BLOCKS

■ Involve the AV node and/or proximal His bundle (“infranodal” AV block)
■ Are measured as degrees with increasing conduction abnormality

RESUSCITATION

Unstable rhythm = rhythm

with associated signs or

symptoms of inadequate

cardiac output.

Unstable cardiac rhythms

require immediate

intervention. Stable rhythms

may be further delineated via

more investigation.

Rhythm with QRS≥ 0.12 sec =

wide complex.