A Clinical Evaluation of ST Changes in a Group of Patients Having Ventricular Arrhythmias

The purpose of this investigation is to determine the prevalence of device-recorded ST segment changes occurring before appropriate Implantable Cardiac Defibrillator (ICD) therapies (ATP or Shock) and to define their temporal relationship to ventricular arrhythmias.

Sudden cardiac death due to cardiac arrhythmia is a devastating and unpredictable complication of coronary artery disease.

Implantation of automatic implantable cardioverter defibrillators (ICD) is a well established therapy for the treatment and prevention of sudden cardiac death. Evidence for the use of these devices has been provided by a number of landmark clinical trials over the last 16 years.

Reduction in ischemia can be achieved by coronary artery revascularization but in many patients may occur a gradual progression to recurrence of ischemia resulting in further life threatening arrhythmias. It is reasonable to assume that unchecked progression of ischemic heart disease may result in increased mortality in ICD patients. It has been shown that the long term mortality risk for ICD patients can be linked to the time since the last coronary revascularization procedure. Both MADIT-II and Sudden Cardiac Death in Heart Failure trial (SCD-HeFT) showed that patients receiving inappropriate ICD therapy have an increased risk of death. It has been speculated that this may be due to progression of the disease and recurrent ischemia.

A feature available in some ICDs manufactured by St Jude medical enables the constant beat to beat monitoring of the intra-cardiac ST segment using the implanted ICD leads. Similar systems have demonstrated this approach to be a reliable method of identifying ischemic events. However, the predictive value of the ST monitoring feature in identifying pending arrhythmic events has yet to be established. Prediction of worsening ischemia could play an important part in allowing physicians to identify ICD patients with greater mortality risk and allow them the time to personalize patient therapy in order to reduce that risk.

Eligibility Criteria:
Inclusion Criteria:

* The patient is implanted with an St Jude Medical (SJM) ICD with ST Monitoring and ShockGuard™ features (and remote care feature in case Merlin.net will be used)
* The patient, in the opinion of the investigator, will not require ventricular pacing for more than 20% of the time.
* The patient, in the opinion of the investigator, has or is at high risk of Coronary Artery Disease (CAD).
* The patient is ≥ 18 years of age.
* The patient is able to provide written Informed Consent prior to any investigational related procedure.

Exclusion Criteria:

* The patient has longstanding persistent Atrial Fibrillation (AF) /Atrial Flutter (AFl) or permanent AF/AFl
* The patient has documented complete heart block.
* The patient is known to have uncontrolled ventricular bigeminy or trigeminy (PVCs on regular basis).
* The patient has severe Left Ventricular Hypertrophy resulting in interventricular conduction defect (IVCD).
* The patient has intermittent bundle branch blocks (BBB).
* The patient is unable to comply with the follow up schedule.
* The patient is participating in another investigational device or drug investigation.
* The patient is pregnant or is planning to become pregnant during the duration of the investigation.