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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Elevated serum level of digoxin

  • Gastrointestinal symptoms with altered color vision

  • Cardiac arrhythmias, especially premature ventricular beats and heart block

GENERAL CONSIDERATIONS

  • May occur in up to 10% of patients hospitalized for heart failure

  • Common clinical features:

    • – Nausea and vomiting

    • – Anorexia

    • – Malaise

    • – Drowsiness

    • – Headache

    • – Insomnia

    • – Altered color vision

    • – Arrhythmia

  • Almost all known cardiac arrhythmias may be caused by digoxin toxicity

  • Toxicity is facilitated by hypokalemia

    • – Severe digoxin toxicity causes hyperkalemia secondary to paralysis of Na+/K+ exchange pump

  • Diuretics cause hypokalemia and thus facilitate digitalis toxicity

  • Other drugs, such as amiodarone and verapamil, increase digitalis serum levels

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Nausea, vomiting, diarrhea, anorexia

  • Drowsiness, malaise, headache, altered color vision

  • Palpitation

PHYSICAL EXAM FINDINGS

  • Bradycardia is common

  • Tachycardia can occur

DIFFERENTIAL DIAGNOSIS

  • Arrhythmias secondary to underlying heart disease

  • Gastrointestinal disorders

  • Central nervous system disorders

  • Ingestion of digoxin-like compounds, such as bufadienolides found in some Chinese aphrodisiacs, and digitalis compounds found in plants, such as foxglove and oleander

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • Low potassium (common)

  • Reduced renal function—may contribute

  • Creatinine level: elevated

  • Digoxin level: outside therapeutic range

ELECTROCARDIOGRAPHY

  • Characteristic downward scooped ST segment

  • Premature ventricular contractions

  • First-, second-, and third-degree heart block

  • Atrial tachycardia with 2:1 block

  • Alternating ventricular tachycardia

  • Junctional tachycardia, often with atrial fibrillation

TREATMENT

CARDIOLOGY REFERRAL

  • Suspected digoxin toxicity

  • Serious ventricular arrhythmias

  • Symptomatic bradycardia

HOSPITALIZATION CRITERIA

  • Serious ventricular arrhythmias

  • Second- or third-degree heart block

  • Need for digoxin antibody therapy

MEDICATIONS

  • Reversal of symptoms or cessation of arrhythmia occurs after withdrawal of digoxin for 48 hours

  • Ventricular arrhythmia may require lidocaine 100 mg IV

  • Antidigoxin immunotherapy may be used, particularly if hyperkalemia is present

MONITORING

  • ECG monitoring in hospital

ONGOING MANAGEMENT

HOSPITAL DISCHARGE CRITERIA

  • Resolution of problem

  • Digoxin level in therapeutic range

FOLLOW-UP

  • Serum digoxin level and ECG 10–14 days after new dosage

COMPLICATIONS

  • Cardiac arrest

  • Syncope

PROGNOSIS

  • Excellent with appropriate treatment

PREVENTION

  • Reduce digoxin dose if renal function decreases

  • Reduce digoxin dose when starting drugs that interact with it and recheck digoxin levels in 2 weeks

RESOURCES

PRACTICE GUIDELINES

  • The safest way to initiate digoxin therapy is ...

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