Mixed Results for AngelMed Guardian in Acute MI Detection

WASHINGTON — The AngelMed Guardian implantable cardiac monitor did not meet its primary efficacy endpoint in the ALERTS trial, but did show it could detect silent MIs and pare down pre-hospital delays in ST-segment elevation MI (STEMI) care.

Regardless of whether the Guardian had been set to alerts off or alerts on, patients who had had a high-risk acute coronary syndrome (ACS) or coronary artery bypass grafting in the 6 months before device implantation had the same 7-day rates of cardiac or unexplained death, new Q-wave MI, or detection-to-presentation time over 2 hours in the case of an occlusive event (4.7% vs 3.1%, posterior probability=0.8833).

Yet devices with alerts enabled had more patients arriving at the hospital within 2 hours of an event (85% vs 5%), reported C. Michael Gibson, MS, MD, of Beth Israel Deaconess Medical Center and Harvard Medical School in Boston, at the Cardiovascular Research Technologies (CRT) meeting, and simultaneously in the Journal of the American College of Cardiology.

Moreover, an expanded analysis showed that the alarms alerted to 42 silent MIs once all patients had their alarms turned on at 6 months in the 907-person study.

“While the trial did not meet its pre-specified primary efficacy endpoint, results suggest the device may be beneficial among high risk subjects in potentially identifying asymptomatic events,” Gibson’s group concluded.

Study participants showed 96.7% freedom from system-related complications through 6 months, suggesting the device is “as safe as a pacemaker,” Gibson said at a CRT press conference.

He added that the trial is an “important proof of concept” that the device can detect silent MIs. “It may not be the final iteration of the technology. There may be subsequent iterations that are less invasive that may offer similar benefits,” he suggested.

Guardian was designed to notify patients early on of a detected acute MI, instead of relying on them to recognize their own symptoms. Each patient gets an implant that communicates wirelessly with a pager-like external medical device for alerts.

Despite its failure with regards to the primary efficacy endpoint, the Guardian is a “step forward to in detection and prompt management of ACS in high risk groups,” commented Elsayed Soliman, MD, of Wake Forest School of Medicine in Winston-Salem, North Carolina, who was not involved with the study.

However, cost-effectiveness must be considered along with the potential for false alarms, he told MedPage Today.

To that end, the authors noted that the false-positive rate was reduced in patients presenting due to alarms compared to patients presenting with symptoms alone (0.164 vs 0.678 per patient-year, P<0.001). Additionally, the system did not make patients ignore symptoms in the absence of a confirmatory alarm, as 625 symptom-only presentations in alarms-enabled patients were observed, according to Gibson and colleagues.

“The device certainly has potential to benefit the patients — the data showed it reduced the false-positive rate and the positive predictive value was increased [from 18.2% to 25.8%],” said Dipti Itchhaporia, MD, of Hoag Memorial Hospital Presbyterian, Newport Beach, California.

“We will still have to monitor the diagnostic accuracy of the device,” Itchhaporia, who was not involved in the study, cautioned.

The device was first rejected by the FDA in 2016 based on 6-month results. After accumulating 3 years of data, it was FDA-approved in 2018 for survivors of a previous ACS who remain at high risk for a recurrent event.

ALERTS randomized people at risk of a recurrent thrombotic event with diabetes, compromised renal function, or a TIMI Risk Score of ≥3 to one of two groups: those who had alerts turned on beginning at 7-14 days after implant, or at 6 months.

Gibson’s group reported similar baseline characteristics between groups.

The trial had originally been designed for 3,000 patients, but was stopped early in part because of discrepancies in ECG tracings found in which Q-waves appeared or disappeared between ECGs at implantation and at randomization. A low event rate also presumably made it harder to show benefits with the Guardian.