Chapter 25: Cardiac Rhythms, ECG Characteristics, and Treatment Guide

Rate: 60-100 beats/min.

Rhythm: Regular.

P waves: Precede every QRS; consistent shape.

PR interval: 0.12-0.20 second.

QRS complex: 0.04-0.10 second.

None.

Rate: < 60 beats/min.

Rhythm: Regular.

P waves: Precede every QRS; consistent shape.

PR interval: Usually normal (0.12-0.20 second).

QRS complex: Usually normal (0.04-0.10 second).

Conduction: Normal through atria, AV node, bundle branches, and ventricles.

Treat only if symptomatic.

Atropine 0.5 mg IV.

Temporary pacing may be necessary until cause is corrected.

Rate: > 100 beats/min.

Rhythm: Regular.

P waves: Precede every QRS; consistent shape.

PR interval: Usually normal (0.12-0.20 second); may be difficult to measure if P waves are buried in T waves.

QRS complex: Usually normal (0.04-0.10 second).

Conduction: Normal through atria, AV node, bundle branches, and ventricles.

Treat underlying cause.

Rate: 60-100 beats/min.

Rhythm: Irregular; phasic increase and decrease in rate, which may or may not be related to respiration.

P waves: Precede every QRS; consistent shape.

PR interval: Usually normal.

QRS complex: Usually normal.

Conduction: Normal through atria, AV node, bundle branches, and ventricles.

Treatment is usually not required.

Rate: Usually within normal range, but may be in the bradycardia range.

Rhythm: Irregular due to absence of sinus node discharge.

P waves: Present when sinus node is firing and absent during periods of sinus arrest. When present, they precede every QRS complex and are consistent in shape.

PR interval: Usually normal when P waves are present.

QRS complex: Usually normal when sinus node is functioning and absent during periods of sinus arrest, unless escape beats occur.

Conduction: Normal through atria, AV node, bundle branches, and ventricles when sinus node is firing. When the sinus node fails to form impulses, there is no conduction through the atria.

Treat underlying cause.

Discontinue drugs that may be causative.

Minimize vagal stimulation.

For frequent sinus arrest causing hemodynamic compromise, atropine 0.5 mg IV may increase heart rate.

Pacemaker may be necessary for refractory cases.

Rate: Usually within normal range.

Rhythm: Usually regular except when PACs occur, resulting in early beats. PACs usually have a noncompensatory pause.

P waves: Precede every QRS. The configuration of the premature P wave differs from that of the sinus P waves.

PR interval: May be normal or long depending on the prematurity of the beat. Very early PACs may find the AV junction still partially refractory and unable to conduct at a normal rate, resulting in a prolonged PR interval.

QRS complex: May be normal, aberrant (wide), or absent, depending on the prematurity of the beat.

Conduction: PACs travel through the atria differently from sinus impulses because they originate from a different spot. Conduction through the AV node, bundle branches, and ventricles is usually normal unless the PAC is very early.

Treatment is usually not necessary.

Treat underlying cause.

Drugs (eg, beta-blockers, disopyramide, flecainide, propafenone) can be used if necessary.