Arrhythmia Monitoring and Outcome after Myocardial Infarction (BIO|GUARD-MI): A Randomized Trial Provisionally Accepted

Christian Jøns^1* Poul Erik Bloch Thomsen² Sam Riahi² Tom Smilde³ Ulrich Bach⁴ Peter Karl Jacobsen⁵ Milos Taborsky⁶ Jozsef Faluközy⁷ Marcus Wiemer⁸ Per Dahl Christensen⁹ Attila Kónyi¹⁰ Dan Schelfaut¹¹ Alan Bulava^{12, 13} Marcin Grabowski¹⁴ Béla Merkely¹⁵ Dieter Nuyens¹⁶ Rajiv Mahajan^{17, 18} Patrick Nagel¹⁹ Roland Tilz²⁰ Jerzy Malczynski²¹ Clemens Steinwender²² Johannes Brachmann²³ Harvey Serota²⁴ Juergen Schrader²⁵ Peter Søgaard²⁶ Steffen Behrens^{4, 27}

• ¹Department of Cardiology, Rigshospitalet, University of Copenhagen, Denmark
• ²Aalborg University Hospital, Denmark
• ³Scheperziekenhuis, Treant Zorggroep, Netherlands
• ⁴Vivantes Humboldt-Klinikum, Germany
• ⁵Rigshospitalet, University of Copenhagen, Denmark
• ⁶University Hospital Olomouc, Czechia
• ⁷National Hospital of Cardiology, Hungary
• ⁸Johannes Wesling Klinik, Germany
• ⁹Regionshospitalet Viborg, Denmark
• ¹⁰Heart Institute, University of Pécs, Hungary
• ¹¹Cardiovascular Center, OLV Aalst, Belgium
• ¹²Ceske Budejovice Hospital, Czechia
• ¹³University of South Bohemia in České Budějovice, Czechia
• ¹⁴Medical University of Warsaw, Poland
• ¹⁵Faculty of Medicine, Semmelweis University, Hungary
• ¹⁶East Limburg Hospital, Belgium
• ¹⁷Lyell McEwin Hospital, Australia
• ¹⁸University of Adelaide, Australia
• ¹⁹Charité University Medicine Berlin, Germany
• ²⁰Universitätsklinikum Schleswig-Holstein, Germany
• ²¹Regionshospitalet Herning, Denmark
• ²²Kepler University Hospital GmbH, Austria
• ²³Klinikum Coburg, Germany
• ²⁴St. Louis Heart and Vascular, United States
• ²⁵Biotronik (Germany), Germany
• ²⁶Aalborg University, Denmark
• ²⁷Vivantes Klinikum Spandau, Germany

Objectives: Cardiac arrhythmias predict poor outcome after myocardial infarction (MI). We studied if arrhythmia monitoring with an insertable cardiac monitor (ICM) can improve treatment and outcome.Design: BIO|GUARD-MI was a randomized, international open-label study with blinded outcome assessment.Setting: Tertiary care facilities monitored the arrhythmias, while the follow-up remained with primary care physicians.Participants: Patients after ST-elevation (STEMI) or non-ST-elevation MI with an ejection fraction >35% and a CHA2DS2-VASc score ≥4 (men) or ≥5 (women).Interventions: Patients were randomly assigned to receive or not receive an ICM in addition to standard post-MI treatment. Device-detected arrhythmias triggered immediate guideline recommended therapy changes via remote monitoring.Main outcome measures: MACE, defined as a composite of cardiovascular death or acute unscheduled hospitalization for cardiovascular causes.Results: 790 patients (mean age 71 years, 72% male, 51% non-STEMI) of planned 1400 pts were enrolled and followed for a median of 31.6 months. At 2 years, 39.4% of the device group and 6.7% of the control group had their therapy adapted for an arrhythmia (hazard ratio [HR]=5.9, P<0.0001). Most frequent arrhythmias were atrial fibrillation, pauses and bradycardia. The use of an ICM did not improve outcome in the entire cohort (HR=0.84, 95%-CI: 0.65-1.10; P=0.21). In secondary analysis, a statistically significant interaction of the type of infarction suggests a benefit in the prespecified non-STEMI subgroup. Risk factor analysis indicates that this may be connected to the higher incidence of MACE in patients with non-STEMI.The burden of asymptomatic but actionable arrhythmias is large in postinfarction patients. However, arrhythmia monitoring with an ICM did not improve outcome in the entire cohort. Post-hoc analysis suggests that it may be beneficial in non-STEMI patients or other high-risk subgroups.