Initial Management of Patients Receiving a Single Shock (IMPRESS)

Patients with a history of ventricular tachycardia requiring defibrillation or who are at
risk for developing ventricular tachycardia will undergo placement of an implantable
cardioverter defibrillator (ICD) for purposes of prevention of sudden cardiac arrest. While
the ICD is lifesaving, if a patient receives a shock from their ICD it is painful and the
entire experience is very traumatic. Traditionally, the management of these patients who
receive a single shock from their ICD is variable because it is not known if the patient will
continue to experience further shocks or not. Some physicians will initiate antiarrhythmic
medical therapy after only a single shock, whereas others will wait until the patient has
recurrent ICD shocks before initiating therapy. All patients should be counseled to not drive
for 6 months following a shock. Ventricular tachycardia ablation, a procedure involving
placing catheters from the groin into the chambers of the heart to isolate the source of
ventricular tachycardia and eliminate these foci through delivery of radiofrequency energy,
is typically reserved for patients with multiple recurrent cases of ventricular tachycardia.
While some studies have shown that ventricular tachycardia ablations can be done safely at an
earlier course of the disease and this procedure has been demonstrated to reduce further ICD
shocks, this practice is not commonplace.

Patients who undergo a ventricular tachycardia ablation procedure, will initially have
catheters placed into the ventricular chambers of the heart and these catheters will be used
to stimulate the heart in an attempt to induce the ventricular tachycardia, a process known
as programmed stimulation. One major limitation of a ventricular tachycardia ablation
procedure is the need to be able to induce the ventricular tachycardia rhythm via programmed
stimulation. If this rhythm cannot be induced then it is very difficult to perform the
ventricular tachycardia ablation procedure. Non-invasive programmed stimulation (NIPS) is a
means of performing programmed stimulation using the patient's own ICD and does not involve
placing catheters into the heart.

Aim: The aim of this study is to investigate if non-invasive programmed stimulation (NIPS)
can be used to risk stratify patients determine if earlier intervention with either
antiarrhythmic medications or ablation in patients with recurrent ventricular tachycardia
that received ICD shocks would help decrease further ICD shocks and hospitalizations for
ventricular arrhythmias.

Primary hypothesis: Patients receiving a single ICD shock for ventricular tachycardia who
undergo a non-invasive programmed stimulation (NIPS) that fails to induce any sustained
ventricular tachycardia, are at low likelihood of experiencing recurrent ICD shocks within
the next year.

Secondary hypothesis: For patients receiving a single ICD shock for ventricular tachycardia
who undergo non-invasive programmed stimulation (NIPS) that induces a sustained, monomorphic
ventricular tachycardia rhythm, the performance of ventricular tachycardia ablation will
reduce the incidence of recurrent ICD shocks within the next year, as compared to
antiarrhythmic therapy alone.

Inclusion Criteria:

- 18-80 years old, both males and females

- Single or dual chamber ICD or BiVentricular ICD in situ

- Ischemic or non-ischemic cardiomyopathy

- Receive a single shock from their ICD for monomorphic ventricular tachycardia

Exclusion Criteria:

- ICD shock for polymorphic VT/VF or inappropriate shock

- Previous ventricular tachycardia ablation within 1 year

- NYHA Class IV heart failure or current inotrope therapy

- Ventricular tachycardia storm

- Listed for heart transplant or LVAD

- Pregnant as determined by urine pregnancy test prior to NIPS