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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Atrial rate of 150–250 bpm

  • Atrioventricular (AV) block of 2:1

  • Often associated with digitalis toxicity

GENERAL CONSIDERATIONS

  • Increasingly seen in advanced organic heart disease and severe pulmonary disease

  • Digoxin toxicity must be suspected

  • A ventriculophasic response is often seen (P-P intervals containing QRS complexes are shorter than those that do not)

  • May be secondary to automaticity or triggered activity

  • Exacerbated by hypokalemia, particularly when associated with digoxin excess

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Related underlying cardiac disease and ventricular rate

  • Shortness of breath

  • Rarely chest pain

  • Palpitations

  • Gastrointestinal symptoms secondary to digitalis toxicity

PHYSICAL EXAM FINDINGS

  • Varying S1

  • Disproportionate jugular a waves compared with pulse (2:1)

  • Carotid sinus massage may slow pulse rate (not advised in digitalis toxicity owing to induction of serious ventricular arrhythmia)

DIFFERENTIAL DIAGNOSIS

  • Other forms of atrial tachycardia

  • Atypical AV nodal reentrant tachycardia

  • Atrial flutter

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • CBC, basic metabolic panel

  • Serum digoxin level (may not correlate with toxicity, which is a clinical diagnosis)

  • Arterial blood gas analysis if there is evidence of advanced lung disease

ELECTROCARDIOGRAPHY

  • Shows atrial tachycardia usually with 2:1 AV block

  • The ventricular rate is often within the normal range

  • Varying block may also be noted

IMAGING STUDIES

  • Echocardiogram to assess underlying heart disease

DIAGNOSTIC PROCEDURES

  • None required

TREATMENT

CARDIOLOGY REFERRAL

  • When secondary to digitalis toxicity usually can be managed by a generalist

  • When tachycardia is persistent with advanced heart disease, cardiology referral is required

HOSPITALIZATION CRITERIA

  • Almost all patients require hospitalization secondary to advanced nature of underlying disease

MEDICATIONS

  • Withdraw digoxin when appropriate

  • In life-threatening conditions, consider digoxin (Digibind) 228 mg (6 vials); life-threatening ingestions may require more

  • Correct electrolyte abnormalities

  • Therapies targeted at abolishing the arrhythmia are unrewarding

  • In persistent cases, AV block with medication may be achieved to control ventricular rate

THERAPEUTIC PROCEDURES

  • If the tachycardia is secondary to advanced heart disease and not related to digitalis toxicity, then radiofrequency ablation may be attempted with a mapping (contact or noncontact) system

SURGERY

  • Usually not required

MONITORING

  • ECG monitoring in hospital

  • Digoxin level monitoring during Digibind therapy

DIET AND ACTIVITY

  • Related to underlying heart disease

ONGOING MANAGEMENT

HOSPITAL DISCHARGE CRITERIA

  • Resolution of arrhythmia

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