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PRECLINICAL STUDIES

Real-Time Detection and Alerting for Acute ST-Segment Elevation Myocardial Ischemia Using an Implantable, High-Fidelity, Intracardiac Electrogram Monitoring System With Long-Range Telemetry in an Ambulatory Porcine Model

Tim A. Fischell, MD, FACC^_*,_*, David R. Fischell, PhD, Robert E. Fischell, DSc, Renu Virmani, MD, Jennifer J. DeVries, LATG, SRS and Mitchell W. Krucoff, MD, FACC^||

^_* Borgess Heart Institute, Kalamazoo, Michigan
AngelMed Systems, Inc., Tinton Falls, New Jersey
CV Path, Gaithersburg, Maryland
MPI Research, Mattawan, Michigan
^|| Duke Clinical Research Institute/Duke University Medical Center, Durham, North Carolina

Manuscript received January 6, 2006; revised manuscript received June 15, 2006, accepted July 23, 2006.

^_* Reprint requests and correspondence: Dr. Tim A. Fischell, Director, Heart Institute at Borgess Medical Center, Professor of Medicine, Michigan State University, 1521 Gull Road, Kalamazoo, Michigan 49048 (Email: taf1{at}net-link.net).

OBJECTIVES: The purpose of this study was to evaluate feasibility of using real-time, high-fidelity, intracardiac electrogram monitoring from a permanently implantable ischemia detection system (IIDS), with long-range telemetry capability to detect ST-segment shifts associated with acute or subacute coronary occlusion in a porcine model.

BACKGROUND: Early identification of coronary occlusion with ST-segment elevation could profoundly accelerate the timing of revascularization and improve clinical outcomes.

METHODS: This paper reports the first investigation using real-time, high-fidelity, intracardiac electrogram monitoring from a permanently IIDS, with long-range telemetry capability. This IIDS was tested in an ambulatory porcine model, with acute coronary occlusion precipitated by stent thrombosis. Two overlapping copper stents were implanted in the left anterior descending (n = 3), the circumflex (n = 3), or the right coronary artery (n = 2) of juvenile farm pigs. Monitoring was carried using telemetry from the IIDS.

RESULTS: All stented pigs had acute ST-segment elevation event(s) triggering the alerting thresholds of the IIDS. All triggered events were confirmed to be caused by thrombosis of the copper stent(s), and well correlated to infarct age and location. Four of the 8 pigs died from ventricular fibrillation, recorded by the IIDS at a mean time of 70 ± 121 h after ST-segment alert. The sensitivity and specificity of alerting for ST-segment shift, associated with thrombotic coronary occlusion, were 100% and 100%, respectively.

CONCLUSIONS: This study demonstrates the ability of an implantable ischemia detection system to detect ST-segment elevation from coronary occlusion in a porcine model of ST-segment elevation myocardial infarction. ST-segment elevation was sufficient to trigger alerting thresholds in all 3 epicardial coronary distributions. Such a system, with real-time alerting capability, could advance the time frame of reperfusion therapy and potentially prevent, rather than interrupt, acute myocardial infarction in patients with coronary artery disease.

Abbreviations and Acronyms   EXD = external alerting device   ICEG = intracardiac electrogram   IIDS = implantable ischemia detection system   IMD = implanted medical device   MI = myocardial infarction   PCI = percutaneous coronary intervention   STEMI = ST-segment elevation myocardial infarction