SCAI: Implantable ischemia monitor alerts patients to MI, plaque rupture
SAN DIEGO--An implantable pacemaker-sized monitor that sounds an alarm when it senses abnormal changes in the heart’s electrical activity is proving an effective early warning system for patients at high risk of MI or plaque rupture, according to data presented Wednesday at the 33rd annual scientific sessions for the Society for Cardiovascular Angiography and Interventions (SCAI).
Early warning of MI and/or ST segment changes following vulnerable plaque rupture could allow prompt evaluation and treatment and improve clinical outcomes, according to the authors.
C. Michael Gibson, MD, director of clinical research for Beth Israel Deaconess Medical Center in Boston, and colleagues reviewed early findings from the first clinical human studies designed to investigate an implantable ST-segment monitoring system with ischemia detection.
The AngelMed Guardian ischemia monitor (Angel Medical Systems, Shrewsbury, N.J.) is implanted in the chest and connects to a pacemaker lead. It compares current data from the patient’s heart to prior data collected when the heart was normal. Using this comparison, the monitor can recognize abnormal shifts in the ST segment. Upon sensing an abnormal ST-segment change, the implanted device buzzes inside the patient’s chest and an external pager sounds an alert.
“Despite our best efforts, it still often takes two to three hours before patients come to the emergency room when they have heart attack symptoms,” said Gibson. “This device is tough to ignore, and it provides patients with greater certainty.”
The researchers implanted ischemia monitors in 37 patients at high risk for acute coronary syndromes. Continuous monitoring assessed the patients’ ST-segment data (from a conventional pacemaker RV apical lead) and detected ischemia when comparisons between ST-segments of sensed data and self-normative reference data from the prior 24 hours exceeded patient-specific ischemia detection thresholds, according to the researchers.
During the follow-up period (median 1.52 years), accurate detection of ruptured plaques using STEMI, angiographic and/or intravascular ultrasound documentation occurred in four patients who showed ST-shifts at normal heart rate ranges. Accurate alerting for heart-rate related ischemic events, reflective of flow-limiting coronary obstructions, also occurred in four patients.
Gibson and colleagues also reported two false positive emergency alerts related to arrhythmias and one due to a programming error. There were no false negative alerts. There were no deaths or Q-wave MIs, which the authors attributed in part to patients arriving at the emergency room an average of 19.5 minutes after an alarm sounded.
According to the investigators, the normal range of daily life ST-segment values was much less (e.g., ST-shift of 10 percent of R-wave height) than those during emergency alarms (e.g. ST-shift of 45 percent).
Based on their findings, the authors concluded that intracardiac ST-segment shift-based ischemia monitoring appears safe and can provide early warning of vulnerable plaque rupture and MI, which may be of particular value in high-risk patients, and in patients with silent ischemia.
Gibson and colleagues noted that chronic intracardiac ischemia monitoring may reduce symptom-to-door times for patients with recurrent acute coronary syndromes. “Every hour you delay getting to the hospital increases the odds of dying,” Gibson said.
An ongoing phase II study will enroll up to 1,000 high-risk patients, with the aim of documenting the effect of the ischemia monitor on survival and other outcomes.
Angel Medical Systems provided funding for the studies.
Early warning of MI and/or ST segment changes following vulnerable plaque rupture could allow prompt evaluation and treatment and improve clinical outcomes, according to the authors.
C. Michael Gibson, MD, director of clinical research for Beth Israel Deaconess Medical Center in Boston, and colleagues reviewed early findings from the first clinical human studies designed to investigate an implantable ST-segment monitoring system with ischemia detection.
The AngelMed Guardian ischemia monitor (Angel Medical Systems, Shrewsbury, N.J.) is implanted in the chest and connects to a pacemaker lead. It compares current data from the patient’s heart to prior data collected when the heart was normal. Using this comparison, the monitor can recognize abnormal shifts in the ST segment. Upon sensing an abnormal ST-segment change, the implanted device buzzes inside the patient’s chest and an external pager sounds an alert.
“Despite our best efforts, it still often takes two to three hours before patients come to the emergency room when they have heart attack symptoms,” said Gibson. “This device is tough to ignore, and it provides patients with greater certainty.”
The researchers implanted ischemia monitors in 37 patients at high risk for acute coronary syndromes. Continuous monitoring assessed the patients’ ST-segment data (from a conventional pacemaker RV apical lead) and detected ischemia when comparisons between ST-segments of sensed data and self-normative reference data from the prior 24 hours exceeded patient-specific ischemia detection thresholds, according to the researchers.
During the follow-up period (median 1.52 years), accurate detection of ruptured plaques using STEMI, angiographic and/or intravascular ultrasound documentation occurred in four patients who showed ST-shifts at normal heart rate ranges. Accurate alerting for heart-rate related ischemic events, reflective of flow-limiting coronary obstructions, also occurred in four patients.
Gibson and colleagues also reported two false positive emergency alerts related to arrhythmias and one due to a programming error. There were no false negative alerts. There were no deaths or Q-wave MIs, which the authors attributed in part to patients arriving at the emergency room an average of 19.5 minutes after an alarm sounded.
According to the investigators, the normal range of daily life ST-segment values was much less (e.g., ST-shift of 10 percent of R-wave height) than those during emergency alarms (e.g. ST-shift of 45 percent).
Based on their findings, the authors concluded that intracardiac ST-segment shift-based ischemia monitoring appears safe and can provide early warning of vulnerable plaque rupture and MI, which may be of particular value in high-risk patients, and in patients with silent ischemia.
Gibson and colleagues noted that chronic intracardiac ischemia monitoring may reduce symptom-to-door times for patients with recurrent acute coronary syndromes. “Every hour you delay getting to the hospital increases the odds of dying,” Gibson said.
An ongoing phase II study will enroll up to 1,000 high-risk patients, with the aim of documenting the effect of the ischemia monitor on survival and other outcomes.
Angel Medical Systems provided funding for the studies.