Anti-arrhythmic Medication v. MRI-Merge Ablation in the Treatment of Ventricular Tachycardia

Ventricular tachycardia (VT) is a morbid arrhythmia responsible for many sudden deaths and
ICD shocks. Despite much progress in the treatment of arrhythmia, VT remains a therapeutic
challenge. Most patients with VT have an implantable cardioverter defibrillator (ICD) for
secondary prevention of sudden cardiac death, however, an ICD merely treats VT, it does not
prevent VT. In patients with recurrent VT and ICD shocks, two strategies are available to
decrease the burden of VT. The first is antiarrhythmic drugs, and the second is VT ablation.
The aim of this study is to compare the efficacy of antiarrhythmic drugs and VT ablation
guided by MRI. VT can sometimes be suppressed with antiarrhythmic medications, however,
these are often ineffective, and carry a high burden of side effects. Many forms of VT can
be cured by selective destruction of critical electrical pathways with catheter ablation. A
major limitation in the ablation of VT, however, is the time required to localize scar
tissue and important pathways for targeting of lesions. Magnetic resonance imaging can now
obtain reliable images of scar location within the ventricles. Recent advances in
electroanatomical mapping systems allow operators to import pre-acquired images into the
mapping system. The aim of this study is to examine the feasibility of importing historic
MRI scar maps of the ventricles into the electroanatomical system and using such images to
guide catheter ablation, as compared to antiarrhythmic drug suppression of VT. We suspect
that MRI guidance will be especially useful in patients with "unstable" VT, i.e. VT that
causes an abrupt drop in blood pressure, and thus cannot be maintained in the
electrophysiology (EP) lab for mapping and entertainment purposes. Patients referred for VT
ablation have ICDs. Through previously completed animal work (Circulation 2004; 110(5):
475-82) and a human trial (2006 Sep 19;114(12):1277-84) we have demonstrated the safety of
MRI in the setting of pacemakers and implantable defibrillators using appropriate
precautions. Through careful device programming and using MRI sequences with limited energy
exposure (specific absorption rate < 2 W/kg) we will study the pre procedural myocardial
anatomy of patients enrolled into this study.

The primary endpoint will be lack of VT documented by implantable defibrillator (when
present) interrogation or Holter monitoring 6 months post ablation. The secondary endpoints
will be comparison of inducible arrhythmia at the end of the procedure, procedure time,
comparison of endocardial voltage mapping to scar on delayed enhancement MRI images, and
complications in each study arm.