Implantable Cardiac Monitor May Reduce Delays to Hospital in High-Risk ACS

An expanded analysis from ALERTS found that 77% of silent-MI patients presented within 2 hours of the alarm going off.

Implantable Cardiac Monitor May Reduce Delays to Hospital in High-Risk ACS

An implanted cardiac monitor that detects ST-segment shifts may be better than relying on symptoms and personal judgment alone when it comes to getting ACS patients to the hospital quickly. A new analysis from the ALERTS study shows that the alarm alone or in combination with symptoms shaved up to 6 hours off arrival times compared with patients who initiated medical contact on their own based on symptoms.

“Reduced delay facilitates opportunities to provide earlier diagnosis and care using guideline-directed therapy, and thus, has the potential to improve clinical outcome,” write David R. Holmes Jr, MD (Mayo Clinic, Rochester, MN), and colleagues in their study published October 14, 2019, in the Journal of the American College of Cardiology.

The device used in ALERTS, known as the Guardian System (Angel Medical Systems, Eatontown, NJ), was approved by the US Food and Drug Administration in 2018 for patients with prior ACS. But Michael J. Domanski, MD (University of Maryland School of Medicine, Baltimore, MD), notes in an accompanying editorial that while the data are “intriguing,” they remain scant. The study sponsor terminated ALERTS when fewer than half of the planned 3,000 patients had been enrolled, and an FDA advisory committee recommended against approving the device based on lack of data in support of efficacy.

“The absence of a demonstration of clinical benefit despite the demonstration of a low complication rate tempers enthusiasm,” Domanski writes. Still, the potential that an alarm could “take the critical diagnosis of the onset of an acute coronary syndrome out of the hands of patients” remains of potentially great value, he adds.

The implant vibrates when there is a sustained ST-segment shift of greater than 2 minutes occurring in beats within the patient’s normal resting heart rate range. Patients are also given an external personal device that alerts them by sounds and flashing lights to seek medical attention.

Erin Michos, MD (Johns Hopkins Medical Institute, Baltimore, MD), who was not involved in the study, said despite aggressive secondary prevention, patients like those enrolled in ALERTS—who have had a recent ACS or multivessel CABG and have at least one other clinical marker such as diabetes, chronic kidney disease, or TIMI score ≥ 3—remain at very high risk. Having an alarm that goes off “could be the nudge that patients need to seek urgent medical care,” she told TCTMD in an email.

Faster Arrival With the Alarm

The 6-month ALERTS pivotal study enrolled 907 patients who were randomized to a treatment group in which the implanted device was turned on or to a control group in which it was turned off. The study did not meet its primary efficacy endpoint of confirmed significant occlusive event within 7 days, which was not significantly reduced in the alarm-on group as compared with the alarm-off group (3.8% vs 4.9%; posterior probability = 0.786). After ALERTS was terminated, all patients had their alarms turned on and the group continued to be followed.

Holmes and colleagues found that when all alarms were turned on, there were 970 ED visits (20% ACS) compared with 181 (18% ACS) during the period when the control group’s alarms were off. Despite the larger number of visits when alarms were on, only 345 of the 970 visits were prompted by the alarm. Among all ACS event visits, 46% were prompted by the alarm, with or without accompanying symptoms, and the remaining 54% were prompted by symptoms only.

Median hospital arrival time was 1.7 hours when all alarms were on compared with 8.0 hours when the control group’s alarms were off (P < 0.0001). Median arrival times were 1.4 hours in the those who were prompted to seek medical care by the alarms only, 1.0 hour in those prompted by a combination of alarms and symptoms, and 4.6 hours in those prompted by symptoms alone. Whereas only 10% of patients arrived within 2 hours when the alarms were off in the control group, 55% arrived within that time frame when all alarms were on. This increased to 81% arriving within 2 hours when the analysis was restricted to visits prompted by the alarm, with or without symptoms.

The researchers say delays in patients with symptoms only, whether or not they had an alarm turned on, may be greater than typically expected due to the high-risk population, 47% of whom had diabetes.

When ED visits included an alarm, symptom-to-door times were 2 hours or less in 79% of ACS events and in 88% of MIs. In the STEMI subset, median symptom-to-door time was 45 minutes from the time the alarm went off. Additionally, 77% of silent MI patients, who had no discernable symptoms that would have prompted them to seek medical attention, presented within 2 hours of the alarm.

Michos noted that with about 30% of MIs being silent, the device may hold the most promise for reducing delays in that area.

Since device implantation is invasive and not without some risk, it is imperative that it be aligned with those who are most likely to benefit from it—subgroups within this high-risk population whose benefit clearly outweighs the potential for harm. Erin Michos

“I would like for the ALERTS trial investigators to do a bit more digging into their data results to help figure out which patient subgroups might benefit the most from the device,” she said. “Is it patients with diabetes or older patients who might be more likely to have silent events? What about women versus men? Since device implantation is invasive and not without some risk, it is imperative that it be aligned with those who are most likely to benefit from it—subgroups within this high-risk population whose benefit clearly outweighs the potential for harm.”

Many Unknowns, but Hope for the Future

Given the neutral results of the primary ALERTS trial, combined with a complication rate of 3.3% and a low positive predictive value, Michos said the net benefit is not entirely clear. Whether the reduction in prehospital delay actually translates into meaningful clinical benefit for hard outcomes like mortality remains unknown, as does the potential for long-term safety issues such as infection and device failure. Another area where data are needed, she added, is patient experience with the device.

“Does it improve quality of life? Does having the device cause them undue anxiety when an alarm goes off, or do they feel better by having some reassurances that they are being monitored?” she wondered.

Domanski noted that the available data are “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.”

Michos agreed, adding she looks for forward to the future and the next generation of these types of medical devices. “A noninvasive (ie, nonimplantable) version that has good sensitivity and specificity for ischemia detection would be highly appealing,” she said.

  • The study was funded by Angel Medical Systems.
  • Holmes, Domanski, and Michos report no relevant conflicts of interest.