Implantable Cardioverter-Defibrillator, Frequent Discharges

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Appropriate therapy for recurrent ventricular arrhythmia

• Supraventricular arrhythmia including sinus tachycardia and atrial fibrillation with rapid ventricular response

• Frequent and inappropriate discharges of implantable cardioverter-defibrillator (ICD)

GENERAL CONSIDERATIONS

• Inappropriate programming can be a cause of frequent discharge

• Fracture of the ICD lead can result in oversensing and multiple inappropriate shocks

• Device–device interaction is becoming infrequent because almost all modern ICDs have intrinsic pacing

• Dual-chamber ICDs have refined programming choices to avoid inappropriate interpretation of supraventricular arrhythmia and therapy

• In patients with frequent appropriate shock therapy, investigate for the following:

  • – Progression or exacerbation of underlying heart disease

  • – Myocardial ischemia

  • – Metabolic disturbance and electrolyte derangement

  • – Thyroid dysfunction

  • – Medication interaction

• If shocks are inappropriate and/or frequent in a hospitalized setting, a magnet can be placed over the ICD to disable all tachycardia therapies until definitive therapy is accomplished

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Frequent shocks

PHYSICAL EXAM FINDINGS

• Clinical symptoms point to worsening of underlying heart condition, active ischemia, or metabolic abnormalities

DIFFERENTIAL DIAGNOSIS

• T-wave or P-wave oversensing

• Double counting of intrinsic wide QRS complex in biventricular defibrillator

• Myopotential oversensing (eg, diaphragm)

• Device malfunction

• Electromagnetic interference (very rare)

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• CBC, basic metabolic panel to evaluate serum potassium

• Serum thyroid-stimulating hormone to assess thyroid function

ELECTROCARDIOGRAPHY

• Device interrogation with the programmer will reveal the appropriateness and the reason for shocks

• ECG, if obtained during a shock, may be helpful

IMAGING STUDIES

• Echocardiogram to evaluate change in left ventricular function and regional wall motion if the shocks are appropriate

• Chest x-ray can infrequently identify lead fracture

DIAGNOSTIC PROCEDURES

• Device interrogation with the programmer

• Coronary angiogram if ischemia is considered a cause of appropriate shocks

TREATMENT

CARDIOLOGY REFERRAL

• All patients should be evaluated by a cardiac electrophysiologist

HOSPITALIZATION CRITERIA

• If there are more than 2 shocks within 24 hours, patients should be hospitalized for an evaluation

MEDICATIONS

• If appropriate, consider altering the substrate for arrhythmias with antiarrhythmic drugs

• Exclude or treat precipitating factors such as:

  • – Metabolic derangement

  • – Myocardial ischemia

  • – Thyroid dysfunction

THERAPEUTIC PROCEDURES

• Electrophysiology consultation, which may involve device reprogramming or replacing the malfunctioning ICD lead

SURGERY

• Rare

MONITORING

• Cardiac ...