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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Heart rate 60–120 bpm

  • Atrioventricular (AV) dissociation

  • Gradual onset and termination

  • When rhythm is caused by digoxin, AV dissociation is common

  • Usually seen with organic heart disease

GENERAL CONSIDERATIONS

  • Causes include:

    • – Digoxin toxicity

    • – Inferior myocardial infarction

    • – Open-heart surgery

    • – Myocarditis

    • – Rarely congenital heart disease

  • This arrhythmia is not episodic

  • P waves may be before or after or buried in the QRS complex

  • Antegrade AV block and intermittent atrial capture may give the appearance of irregular rhythm

  • Enhanced vagal tone may slow the arrhythmia but not terminate it

  • Digoxin toxicity is the cause of 60% of cases

  • Regular ventricular rhythm in atrial fibrillation treated with digoxin should raise suspicion of this arrhythmia

  • Twenty percent of cases are secondary to inferior infarction and usually disappear within days

  • Valve surgery and myocarditis are other causes of this arrhythmia

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Depends on precipitating cause

  • Symptoms of digoxin toxicity may be present

  • Myocardial infarction or valve surgery history will be self-evident

PHYSICAL EXAM FINDINGS

  • Cannon a waves if there is AV dissociation

  • Variable S1 may be present

  • Other features depend on underlying cause

DIFFERENTIAL DIAGNOSIS

  • Atrial tachycardia

  • Atrioventricular nodal reentry tachycardia (AVNRT) (slower heart rate, gradual onset and termination, and lack of termination with vagal maneuvers differentiate the rhythm from AVNRT)

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • CBC, basic metabolic panel

ELECTROCARDIOGRAPHY

  • ECG to detect and document the rhythm

  • Continuous telemetry until the rhythm resolves

IMAGING STUDIES

  • Echocardiogram to evaluate left ventricular function

DIAGNOSTIC PROCEDURES

  • Overdrive pacing transiently suppresses the rhythm

TREATMENT

CARDIOLOGY REFERRAL

  • All patients should be evaluated by a cardiologist

HOSPITALIZATION CRITERIA

  • Most patients are hospitalized at the time of the arrhythmia

  • If patients present to the emergency room, they require hospitalization until the rhythm resolves

MEDICATIONS

  • No treatment is usually indicated

  • Rhythm spontaneously resolves as the inciting event subsides

  • If the rhythm is hemodynamically disturbing, AV sequential pacing at a rate faster than the tachycardia may suppress the rhythm and restore the atrial contribution to cardiac output

THERAPEUTIC PROCEDURES

  • None required

MONITORING

  • No need for monitoring after the rhythm resolves

ONGOING MANAGEMENT

HOSPITAL DISCHARGE CRITERIA

  • Once the rhythm resolves, provided that the patient is stable otherwise

FOLLOW-UP

  • Two ...

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