Initial Management of Patients Receiving a Single Shock (IMPRESS) (IMPRESS)

The goal of this study is to determine the optimal treatment for patients who receive a single shock from their implantable cardioverter defibrillator (ICD). All participants in this study will be fitted with a special electrode vest to detect the origin of heart rhythm abnormalities and then they will undergo a procedure called Non-Invasive Programmed Stimulation (NIPS). This procedure involves sedating a participants with anesthesia and then using the participant's own ICD to try to stimulate the heart to go into ventricular tachycardia. If this procedure is unable to induce the participant into ventricular tachycardia, then the participant will just be managed with usual care and will not be placed on any additional medications and will not undergo an ablation. However, if the NIPS induces the ventricular tachycardia, the electrode vest will be used to determine the origin of the abnormal heart rhythm inside the heart. After a successful NIPS procedure, the participants will be randomly assigned to either be placed on medication therapy or undergo catheter ablation. The outcomes from all three groups will be compared and the researchers hope to better understand which participants are most likely to benefit from watchful waiting versus medication versus catheter ablation.

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.

Patients who have a positive NIPS study and are randomized to the medical therapy arm will either be initiated on antiarrhythmic therapy or will have their antiarrhythmic therapy intensified. All medication therapy is considered usual standard therapy.

Patients who have a positive NIPS study and are randomized to the ablation arm will undergo ventricular tachycardia ablation procedure guided by CardioInsight.

Patients who had a negative NIPS study will not be assigned to a treatment group and will be followed according to standard of care.

For the antiarrhythmic naïve patients, the attending physician may initiate therapy with sotalol or amiodarone. For patients already on therapy with sotalol or amiodarone, the attending physician may choose to either increase the dosage/ frequency of these medications and/or add mexiletine to the regimen. Other alterations to medical therapy, such as adjusting the dose of beta-blockers, calcium-channel blockers, anti-hypertensive, diuretic or anti-anginal medications may be performed at the discretion of the attending physician.

All patients will receive this procedure in attempt to induce ventricular tachycardia. The outcome of this procedure determines if a patient will be randomized.

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

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