Implantable monitor alerts patients to asymptomatic ACS

An implantable cardiac monitor designed to alert patients with coronary artery disease to progressive, abnormal ST-segment shifts could expedite transport to the ED and reduce treatment delays during acute coronary syndromes (ACS), according to work published in the Journal of the American College of Cardiology.

The device in question—Angel Medical Systems’ implantable AngelMed Guardian system—was developed to detect imminent ACS events even when patients have no recognizable symptoms. The Guardian monitors patients’ hearts 24 hours a day, seven days a week, and vibrates when it detects any kind of abnormality in a patient’s resting heart rate.

David R. Holmes, Jr., MD, of the Mayo Clinic in Rochester, Minn., and colleagues said in JACC that a device like the Guardian could be particularly useful for ACS patients with suspected ST-segment elevation MI (STEMI), non-STEMI or unstable angina whose outcomes depend largely on timely presentation to a hospital. And that metric hinges on a host of other factors, like presence and recognition of symptoms, a patient’s decision to act on those symptoms and transport to the nearest medical facility.

“It is well-established that ACS symptoms are highly variable, if they occur at all, creating barriers to timeliness in patients taking action, and [there is an] ongoing dilemma of morbidity and mortality from asymptomatic myocardial infarctions,” Holmes and co-authors wrote. “Strategies to reduce pre-hospital delay times have been challenging.”

The team explored the efficacy of the Guardian in the FDA-approved ALERTS (AngelMed Early Recognition and Treatment of STEMI) pivotal trial, which enrolled 907 patients at a high risk for recurrent ACS events. Patients were randomized to one of two treatment groups: either six months of “alarms off” treatment followed by six months of “alarms on” treatment (control group), or “alarms on” treatment for a consecutive 12 months (treatment group).

The treatment group saw reduced delays in the ED compared to the control group, with 55% of ED visits for ACS events taking less than two hours compared to 10% of visits in the “alarms off” group. Average pre-hospital delay for MI for 12.7 hours for the control group and just 1.6 hours for the treatment group.

Holmes et al. also reported that the study’s median alarm-to-door delay for asymptomatic MI was 1.4 hours, and median symptom-to-door delay for symptoms-only MI in “alarms on” patients was 4.3 hours.

In a related editorial, Michael J. Domanski, MD, of the University of Maryland School of Medicine, criticized the study, noting the ALERTS trial had been terminated by its sponsor after just 1,020 patients had been recruited. The absence of a clinical benefit despite the demonstration of low complication rates “tempers enthusiasm,” he wrote, and “the data are too scant” to make any conclusions.

Domanski did say that Holmes and colleagues’ findings are a good base for further study, because an alert system like the Guardian holds a lot of potential for earlier diagnosis of life-threatening ACS events. The device’s ability to detect an ACS event when the patient has no physical or recognizable symptoms could be of great value, he said, especially since both vibrations and audible alarms enhance patient motivation to get to an ED.

“The marriage of advanced computational methods, such as machine learning, with implantable microelectronic devices will play an increasingly important role in diagnosis,” Domanski wrote. “This marriage of these computational techniques to implantable microelectronics is the exciting frontier in which this paper lives.

“This is not the most compelling support for the use of this particular device, and the original study design leaves questions open about the foray into advanced technology. However, there is adequate evidence to justify further study of this technology.”

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