The Guardian: an implantable system for chronic ambulatory monitoring of acute myocardial infarction

Components of the implantable ischemia-detection system. Implantable components: the IMD, resembling a Ventricular Demand Inhibited Pacemaker (VVI) pacemaker, is shown (A), attached to the lead adapter (B) and a standard bipolar, screw-in, RV lead (C). External components: the external pager-sized alerting device (E) is attached using a cable (F) to the programmer (D) in order to permit IMD programming and data retrieval, via telemetry. In addition to sound cues, the EXD has 2 light-emitting diodes: red light for emergency alerts related to acute ischemia and severe cardiac event detection, and yellow light for “see your physician” alerts that are issued for lower priority events.

Guardian recordings from before (baseline) and 2 to 3 minutes after balloon inflation, which occurred during angioplasty (inflation). Data are shown from 3 patients (B7, B10, and B9, respectively) who underwent balloon occlusions of the LAD, LCX, and RCA, resulting in ST shifts of −42%, 34%, and 18%, respectively. In the LAD occlusion recording, the arrow points to the time at which the balloon was deflated. The negative ST shift begins to shift positive (toward the shape it demonstrated during the preocclusion baseline recording) within 2 beats.