What is the role of implantable cardioverter-defibrillators in the treatment of ventricular tachycardia (VT)?

Updated: Dec 05, 2017
  • Author: Steven J Compton, MD, FACC, FACP, FHRS; Chief Editor: Jeffrey N Rottman, MD  more...
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Answer

The advent of the  implantable cardioverter-defibrillator (ICD) has changed the face of ventricular arrhythmia management. Like pacemakers, these devices can be implanted transvenously in a brief, low-risk procedure. Once implanted, the ICD can detect ventricular tachyarrhythmias and terminate them with defibrillation shocks or anti-tachycardia pacing algorithms (see the image below).

Termination of ventricular tachycardia (VT) with o Termination of ventricular tachycardia (VT) with overdrive pacing. This patient has reentrant VT, which is terminated automatically by pacing from an implantable cardioverter-defibrillator.

ICD therapy is used to augment medical management for the following individuals [4] :

  • Most patients with hemodynamically unstable VT
  • Most patients with prior myocardial infarction (MI) and hemodynamically stable sustained VT
  • Most cardiomyopathy patients with unexplained syncope (an arrhythmia is presumed)
  • Most patients with genetic sudden death syndromes when unexplained syncope is noted

In patients with prior VT or ventricular fibrillation (VF), the Antiarrhythmics Versus Implantable Defibrillators (AVID) study, the Canadian Implantable Defibrillator Study (CIDS), and the Cardiac Arrest Study, Hamburg (CASH), demonstrated better survival with ICD therapy than with antiarrhythmic therapy with amiodarone or sotalol. [77] The survival difference was statistically significant in AVID, of borderline significance in CIDS, and insignificant in CASH. A meta-analysis of the three trials found a 28% reduction in relative risk of death. [77]

Patients with nonischemic dilated cardiomyopathy and considerable left ventricular dysfunction, or arrhythmogenic right ventricular cardiomyopathy, who have sustained VT or VF should have ICD placement. These patients should also be receiving optimal long-term medical therapy and may reasonably be expected to survive with good functional status for longer than 1 year. [4]

ICDs are not used for the following individuals [46] :

  • Patients with VT or VF occurring during an acute ST-segment elevation MI (STEMI)
  • Patients with reversible, drug-induced VT
  • Patients with poor expected survival as a consequence of comorbid conditions

Because ICDs treat, rather than prevent, ventricular arrhythmias, as many as 50% of ICD recipients require therapy with antiarrhythmic drugs to reduce the potential for ICD shocks. Catheter ablation may be used in patients with an ICD who are receiving multiple shocks because of sustained VT that is not manageable by changing drug therapy or who do not wish to undergo long-term drug therapy. [40]

Prospective follow-up data from 2,352 patients in the Israeli ICD Registry suggest that the presence of anemia (hemoglobin [Hb] ≤12 g/dL) in patients with ICDs independently increases the risk for ventricular arrhythmias during long-term follow-up. [78]  At 2.5 years of follow-up, the rate of appropriate shocks in patients with low Hb levels (11%) was nearly double that of those with high Hb levels (6%) (log-rank P <0.005). Moreover, each 1 g/dL reduction in Hb was independently associated with a significant 8% increased risk for a first appropriate shock (P <0.03), and anemia increased the risk for all-cause mortality as well as heart failure hospitalizations or death, but not with inappropriate ICD shocks. [78]


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