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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 telemetry monitoring in hospital

DIET AND ACTIVITY

  • Usual cardiac diet

  • If sinus ...

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