Benefit of SubQ Arrhythmia Monitoring Post-MI May Hinge on Risk: BIO|GUARD-MI

Jagmeet P. Singh, MD, MSc, DPhil; Christian Jøns, MD, PhD


April 06, 2022

This transcript has been edited for clarity.

Jagmeet P. Singh, MD, MSc, DPhil: Hello. I'm Jag Singh for Medscape Cardiology. I'm here at ACC 2022 in DC. I have with me here Dr Christian Jøns from the Rigshospitalet in Copenhagen, Denmark, who is here at the ACC presenting a late-breaking clinical trial. Welcome, Christian.

Christian Jøns, MD, PhD: Thank you very much.

Singh: Christian is presenting a late-breaking clinical trial looking at bio loop monitoring in patients post MI with a preserved ejection fraction. It's a really novel concept. Christian, can you give us an overview of the study and what you found?


Jøns: Yes, thank you. The background for the study was that we have seen in multiple trials that arrhythmias of all kinds are very predictive of major cardiac events in post-MI patients. Recently, we have seen in trials using implantable cardiac monitoring (ICM) devices that even the asymptomatic, shorter-lasting arrhythmias are very predictive. There have been no major trials investigating if we can actually respond to these arrhythmias and change the prognosis. That's why we designed the BIO|GUARD-MI trial.

Post-MI patients were randomized. We used the CHA2DS2-VASc score as an easily clinically useable risk factor score because we knew we had to use high-risk patients. They had to have a CHA2DS2-VASc score more than 4 in men and 5 in women, and then we randomized them to ICM implantation. Then we actually let them go and continue routine follow-up at their local hospital or cardiologist.

If we saw an arrhythmia, there was a central monitoring board that would adjudicate arrhythmias. We had prespecified arrhythmias in the protocol. If we saw an arrhythmia, the board would notify the site and we would record the time to respond and we also had prespecified an algorithm of responses. Then we would record if a major cardiac event happened later on. We had the arrhythmia and the time to respond, and what the response was to the arrhythmia. That was the concept of the trial.

Singh: How many patients did you recruit and what did you find within the subsets?

Jøns: We recruited 790 patients, so 398 had an ICM. The first interim analysis showed inconsistencies in the reporting of major cardiac events. There was an independent phone board that called patients every 6 months, and there were some events missing. The data safety monitoring board warned the sponsor and there was a large effort to find these events. Unfortunately, after 12 months of trying to find the endpoints, the trial was stopped prematurely. There were 218 of 372 expected events at that time.

When the trial ended, the main primary outcome among the entire cohort was not changed significantly. We did prespecify the type of infarction and we stratified patients per protocol into non-STEMI and STEMI patients. In the non-STEMI group, there was a significant reduction of more than 30% in the primary outcome, but not in the STEMI group.

Of course, we tried to look for the reason why there was this difference, and we noticed that there was a higher risk in the non-STEMI group. They had a 75% higher risk of the primary outcome than the STEMI patients, which makes sense because we had to have a risk that we could reduce. If there is no risk, then you can't reduce it.

It seemed that in this group, the ICM arrhythmias were associated with a worse outcome. When you intervened, it reduced it. The risk was not high enough in the STEMI group. We wondered if it was really related to the type of infarction or something else.

We looked for other high-risk groups. We tried to identify these factors in the control group and then apply them to the ICM group. For all high-risk groups, the picture was the same. If you have a high risk, then you benefit from intervening for these arrhythmias. If you have a low risk, then there's not enough risk to reduce to reduce the outcomes.

AF and Bradycardias Mainly

Singh: That's really interesting. Can I just take a step back? Can you tell us what arrhythmias you found within these patients that required an intervention? There were 790 patients substratified into ICM or no ICM and followed along. In the ICM group, you found some arrhythmias. What were those actionable arrhythmias?

Jøns: Yes, sure. As expected, the main intervention was starting anticoagulation for atrial fibrillation. There were many bradycardia events as well, so a large portion of pacemakers were put in and there were medication changes, mostly a decrease in beta-blockers. There were, I think, 11 ICDs and some ablations done, but that was not a major part of it.

The main outcomes of the primary endpoint, which was a combined endpoint, were new coronary events and the worsening of heart failures. Those were mainly present in the non-STEMI group. Those were the main endpoints we intervened for.

Singh: The non-STEMI people who had the ICM had an intervention and a changed outcome in those patients?

Jøns: Yes.

Singh: In the STEMI people, there were not enough events for a change in outcome?

Jøns: There were fewer events and less of an effect of doing anything with those arrhythmias.


Singh: Why this difference between non-STEMI and STEMI? Why do you think the non-STEMI people had this kind of response?

Jøns: This is purely hypothetical, and just my opinion, but I think they simply represent a later stage of disease. That could also mean that, had we followed the STEMI patients longer, we would see the same thing because they will just simply have the events later.

Singh: Were the non-STEMI patients overall sicker than the STEMI patients? Were they older? Did they have more comorbidities?

Jøns: We didn't find a strong signal toward that. They had twice the risk, were on fewer medications, and they had a slightly higher CHA2DS2-VASc score (not a lot). It's not a strong signal where we can say these points are important, it was just that they had a higher risk. Certainly, identifying the best high-risk groups is very important for this treatment strategy.

Singh: What is your take-home message from this? Should we be screening patients post MI and substratifying them into STEMI and non-STEMI groups, and then isolating the non-STEMI and implanting loop recorders proactively in these patients? Is there a subgroup within the non-STEMI that might be higher risk that we need to focus on? Any thoughts on that?

Jøns: That's a very good question. I think the first take-home message is that you can monitor anything in the body nowadays. You can monitor blood sugar and all these things. I think the trial shows that if you monitor for asymptomatic arrhythmias and intervene, then in the high-risk patients, you can actually prevent hospitalizations and other events.

We are looking into the right high-risk patients. Right now, the best group is the non-STEMI group because they seem to be more high risk, with a CHA2DS2-VASc score of 4 or more. We are certainly looking into presenting the right high-risk group.

Singh: That's terrific. I think the interesting thing is what you suggested. I like the name of your study — BIO|GUARD-MI — because what you're trying to show is that the arrhythmic events are serving like biomarkers, right, because the ones who had bradycardia or conduction block or atrial fibrillation…

Jøns: It's a sign of progression of heart disease.

Singh: Yeah, exactly, indicating that they probably have more worsened cardiac status as compared with the STEMI group. I think it really makes sense to consider at this stage before we decide and develop further strategies to validate what you've found to change clinical practice from that. Just a quick question. Do you think there's any role in wearables — watches and smart watches — in trying to be able to document some of these things?

Jøns: It's a very good question. Many of these asymptomatic arrhythmias occur at night so you would have to wear the watches at night. You also need a good noise-to-signal ratio and you need some good algorithms to take out the untrue arrhythmias. The future will show us what type of devices we're going to use for this intervention.

Singh: Fascinating. Christian, thank you so much for this phenomenal late breaker. Congratulations to you and your team for conducting such a tough study. I can only imagine how difficult this study was to do. I think it's certainly enlightening and potentially practice-changing. Thank you again for being here.

Jøns: Thank you very much.

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