Tricyclic Antidepressants, Cardiac Effects

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• QT interval prolongation

• QRS prolongation (> 100 ms) is a sign of toxicity

• Rightward deviation of terminal 40 ms of the QRS is the most sensitive marker of toxicity (rightward terminal R wave in aVR)

• Ventricular arrhythmias

GENERAL CONSIDERATIONS

• Properties are similar to those of class I antiarrhythmic agents

• Orthostatic hypotension secondary to alpha₁-adrenergic receptor blockade may cause frequent falls, particularly in the elderly

• Ventricular proarrhythmia may occur in patients with serious structural heart disease

• Tricyclic antidepressant overdose carries a mortality rate of 2–3% secondary to cardiac complications

  • – Generally considered second-line therapy for depression due to their cardiac and anticholinergic effects

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Dizziness, syncope

• Dry mouth

• Urinary hesitancy

• Muscle rigidity

• Incoordination

• Drowsiness

• Blurred vision

PHYSICAL EXAM FINDINGS

• Orthostatic hypotension

• Irregular pulse

• Low blood pressure

DIFFERENTIAL DIAGNOSIS

• Overdose of anticholinergic agents

• Brugada syndrome

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• Drug screen

ELECTROCARDIOGRAPHY

• QT, ORS prolongation

• Terminal R wave in aVR

• Ventricular arrhythmias

TREATMENT

CARDIOLOGY REFERRAL

• Ventricular arrhythmias

• Syncope

• Suspected tricyclic toxicity

HOSPITALIZATION CRITERIA

• Syncope

• Serious ventricular arrhythmias

• Suspected overdose

MEDICATIONS

• Aggressive supportive measures, such as gastric lavage, airway maintenance, and activated charcoal

• Alkalinization with IV bicarbonate for cardiac arrest, hypotension, arrhythmias, acidosis, and QRS prolongation

MONITORING

• ECG monitoring in hospital

DIET AND ACTIVITY

• Restricted activities until adverse effects are gone

ONGOING MANAGEMENT

HOSPITAL DISCHARGE CRITERIA

• Resolution of drug effects

COMPLICATIONS

• Sudden death

PROGNOSIS

• Excellent with early recognition and appropriate treatment

PREVENTION

• Patient education about drugs

RESOURCES

PRACTICE GUIDELINES

• Tricyclic antidepressant overdose almost always requires hospitalization

REFERENCE