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

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.