Remote monitoring of implantable cardiac monitors (ICMs) can help to detect serious arrhythmias in high-risk post-infarction patients with cardiac autonomic dysfunction and moderately reduced ejection fraction, according to a study presented in a Hot Line session at ESC Congress.

The SMART-MI trial was conducted between May 2016 and February 2021 at 33 centres in Germany and Austria. The study enrolled MI survivors with left ventricular ejection fraction (LVEF) 36–50% and cardiac autonomic dysfunction, which is associated with poor outcomes after myocardial infarction (MI), including arrhythmias and sudden death, independently of ejection fraction.

In total, 400 patients were randomly allocated to ICM implantation and remote monitoring or conventional follow-up at a 1:1 ratio. Using a minimally invasive procedure, the monitor was implanted subcutaneously. A telemonitoring system then transmitted a daily report to an ICM core lab.

Implantable cardiac monitors (ICMs) were found to predict complications

The primary endpoint was time to detection of serious arrhythmic events (including, atrial fibrillation lasting 6 minutes or longer, higher-degree atrioventricular block, fast non-sustained ventricular tachycardia (VT), and sustained VT/ventricular fibrillation) all of which have been associated with poor outcomes or would trigger appropriate therapies in patients with an ICD.

During a median follow-up of 21 months, the primary endpoint occurred in 30% of patients in the ICM group and 6% of patients in the control group. The cumulative 3-year detection rate of serious arrhythmic events was 41.2% in the ICM group compared to 10.7% in the control group.

Secondary endpoints included major adverse cardiac and cerebrovascular events (MACCE; cardiovascular mortality, stroke, systemic arterial thromboembolism and unplanned hospitalisation for decompensated heart failure). Detection of serious arrhythmic events strongly predicted subsequent MACCE in both the ICM group and the control group.

Adverse outcomes were three times more likely to be detected early in the ICM group

Principal investigator Professor Axel Bauer of the Medical University of Innsbruck, Austria noted that although the prognostic impact of serious arrhythmic events was not related to the mode of detection, the sensitivity in detection was three times higher in the ICM group compared to the control group, meaning adverse outcomes were three times more likely to be detected early in the ICM group.

“The study found that post-infarction patients with cardiac autonomic dysfunction and only moderately reduced LVEF developed a high number of serious subclinical arrhythmic events that could be detected early and effectively with ICMs.

“The spectrum and frequency of arrhythmias in these patients was comparable to that of post-infarction patients with reduced LVEF, who are currently candidates for prophylactic ICD therapy. Our study supports the use of ICMs in high-risk post-MI patients with moderately reduced LVEF and cardiac autonomic dysfunction as a sensitive tool for continuous risk assessment,” said Prof Bauer.

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