AngelMed Guardian system (Angel Medical Systems, Eatontown, New Jersey) is an implantable device which detects ischemic events using a pacemaker lead positioned at right ventricular apex . The device detects ischemic events by analyzing shifts in ST segment. It compares ST deviation of a 10 second electrogram with baseline data. If the shift in ST segment is greater than the heart rate dependent programmable threshold, an emergency alert signal is generated. The implantable device gives a vibratory alert and an external associated device gives auditory and visual alert.
ALERTS (AngelMed for Early Recognition and Treatment of STEMI) trial was a multicenter, randomized trial of the device . Nine hundred and seven high risk acute coronary syndrome patients were randomized to a control group in which alarms are deactivated and a treatment group in which alarms were active, for a period of 6 months. Absence of system related complications was the primary safety endpoint. Composite primary efficacy endpoint was cardiac/unexplained death, new Q wave myocardial infarction or detection to presentation time of more than 2 hours. Safety was achieved with 96.7% freedom from system-related complications.
Detection-to-door delay among the treatment group patients was 51 minutes. Detection-to-door time was more than 30 hours in the control group. Aggressive follow up with device interrogation was needed to capture all silent myocardial infarctions in the control group.
An important limitation of the study was an unanticipated low event rate. This could be the reason for no significant difference in the hard clinical outcome of cardiovascular or unexplained death.
Hopenfeld B, John MS, Fischell DR, Medeiros P, Guimarães HP, Piegas LS. The Guardian: an implantable system for chronic ambulatory monitoring of acute myocardial infarction. J Electrocardiol. 2009 Nov-Dec;42(6):481-6.