Reviewer: Dr. Ersan Oflar

Name of the Study: BIO-GUARD-MI(The Clinical Effect Of Arrhythmia Monitoring After Myocardial Infarction)

Published in Congress: ACC 2022

Background
Even though the prognosis after myocardial infarction (MI) has improved much over recent decades due to improved and faster revascularization, platelet inhibition, and device therapy  a proportion of postacute MI (AMI) patients with additional risk factors remain at high risk, with 5-year mortality ranging from 15% to 45% depending on the population. Observational data have suggested that incident arrhythmias detected by an implantable cardiac monitor (ICM) are a better predictor of adverse cardiovascular events in patients suffering a myocardial infarction (MI).

Objective
The primary objective of the BIO-GUARD-MI study is to investigate whether the early diagnosis of cardiac arrhythmias provided by an ICM with automated daily remote monitoring(RM) and the consequent medical treatment will decrease the risk of MACEs in patients with previous AMI, LVEF > 35%, and a CHA2DS2-VASc risk score ? 4/5 (men/ women). Secondary objectives include the time to diagnosis of arrhythmias, each MACE component evaluated individually, the influence of each component of the CHA2DVASc score on MACEs, and quality of life.

Method
The BIO-GUARD-MI study is a multicenter, open, prospective, randomized controlled international study with an event-driven design. High-risk patients with recent or chronic MI are invited to participate. Patients who fulfill the enrollment criteria may be enrolled after conclusion of treatment for an AMI (if an ICD indication was excluded by a confirmed LVEF > 35%) or if they had a chronic MI. Patients are randomized in a 1:1 ratio to receive implantation of an ICM or conventional treatment.. Both investigator and patient are aware of the randomization result. All patients are discharged to the typical post-MI follow up. To assess the primary endpoint, all patients will receive telephone calls every 6 months from an independent Clinical Research Organization. If they report that they have been hospitalized, the investigational site is notified and reports the adverse event based on documentation requested from the relevant hospital. The telephone calls will be conducted in a way so as not to interfere in the normal healthcare (i.e., the patient will receive no medical advice of any kind but will only be asked about events of the preceding period). The primary endpoint is the time from randomization to the first MACE during the clinical investigation.

Results
An estimated 1400 patients were to be enrolled in study. A total of 790 post-MI patients (mean age 72 years; 72% men) (Average LVEF was 53%) were enrolled and randomised (1:1) to ICM implantation or not, stratified by the presence or absence of ST-segment elevation at the index MI (49%/51% STEMI/NSTEMI). Group assignment was open-label but outcome assessment blinded. The rate of treated arrhythmias were  higher in the ICM group (39% vs 6%; HR 5.9; P < 0.0001). The most common treatments applied in the ICM group were oral anticoagulation (40%), pacemakers (20%), and beta-blocker dose adjustments . compation ICM with usual follow-up, ICM monitoring led to more arrhythmias being picked up and treated, but it did not ultimately reduce the risk of CV mortality but significant decrease was seen in primary endpoint events with arrhythmia monitoring in the NSTEMI group (HR 0.69; 95% CI 0.49-0.98) but not the STEMI group (HR 1.10; 95% CI 0.72-1.69).

Conclusion
Implantable cardiac monitoring (ICM) of high-risk patients who had suffered a myocardial infarction (MI) did not reduce future cardiovascular events overall, but benefit was seen in NSTEMI patients compared with STEMI patients. NSTEMI patients who received an ICM were about 30% less likely to experience the primary composite endpoint.

Interpretation
There is little doubt that using implantable monitors to continuously monitor biological functions will increase in the future and to some extent reduce the need for in clinic controls. The BIOGUARD-MI trial is important as it is the first attempt to simplify the response to the highly complex nature of cardiac arrhythmias, although the results are negative.However, several open questions remain, including what to monitor and how frequent and how sensitive the monitoring should be..