Digoxin Toxicity

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