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.