High-Risk Patients Post-MI With Reduced LVEF Identified With Loop Recorders

Wearable external loop recorder (ELR) applied at discharge in patients who have been hospitalized with acute myocardial infarction (MI) and left ventricular (LV) dysfunction is able to identify individuals at high risk for mortality. These findings were published in the Indian Heart Journal.

The prospective, multicenter, nonrandomized Identifying High Risk Patients Post Myocardial Infarction with Reduced Left Ventricular Function using External Loop Recorders (INSPIRE-ELR) clinical study was conducted in 11 hospitals in India. Researchers sought to determine the percentage of patients with significant arrhythmias early following an MI who have low left ventricular ejection fraction (LVEF) found at discharge, as well as the association with mortality during a 12-month follow-up.

A total of 249 patients diagnosed with acute MI (ST-elevation myocardial infarction [STEMI] or non-STEMI), which was documented within 10 days of symptom onset with an LVEF of 35% or less on echocardiography at discharge, were included in the study. All of the participants were enrolled prior to the ELR application. The phase 1 monitoring period was during the 7 days after ELR was applied at discharge. The phase 2 monitoring period was another 7 days at 8 to 10 weeks following the index MI.

The primary study objective was to evaluate the incidence of predefined clinically significant arrhythmias in the phase 1 monitoring period. Secondary objectives included the following:

• To evaluate the incidence of clinically significant arrhythmias, as recorded via ELR in the phase 2 monitoring period
• To describe all medical interventions conducted and/or indicated based on ELR findings during the phase 1 and phase 2 monitoring periods
• To determine whether patients with nonlethal arrhythmias documented by ELR during the phase 1 and phase 2 monitoring periods had a higher risk for all-cause mortality at 1 year
• To assess whether an association exists between ELR-reported arrhythmias and incidence of sudden cardiac death, resuscitated ventricular fibrillation (VF), and appropriate implantable cardioverter defibrillator shock

Clinically significant arrhythmia, which was predefined, included any episodes of VF, sustained and nonsustained ventricular tachycardia (VT), atrial fibrillation (AF), chronic atrial flutter, high-degree atrioventricular (AV) block, and complete heart block.

All of the 249 study participants received a wearable ELR 5±3 days following MI to monitor arrhythmias for 7 days. The mean patient age is 56±12 years and 86% of the participants are men. Reperfusion had been received by 82% of the participants, with all individuals receiving standard-of-care cardiovascular medications at hospital discharge. The median LVEF, which was measured at 5.1±3.0 days following MI, is 34%.

Of the 233 individuals who completed monitoring (mean monitoring duration, 7.1±1.5 days), a clinically significant arrhythmia is reported in 34.8% of them (95% CI, 28.9%-41.1%) during the phase 1 monitoring period. These arrhythmias include VT/VF in 10 participants, frequent premature ventricular contractions in 65 individuals, AF in 8 patients, chronic atrial flutter in 4 participants, second- or third-degree AV block in 4 individuals, and symptomatic bradycardia in 8 patients. Overall, 26 patients died.

At 12 months, mortality is significantly higher in participants with clinically significant arrhythmias compared with those without (23.6% vs 4.8%, respectively; 19 deaths vs 7 deaths, respectively; hazard ratio [HR], 5.5; 95% CI, 2.3-13.0; P <.0001). When the 9 participants with zero time at risk following acute ELR monitoring are excluded, mortality among those with clinically significant arrhythmias remains significantly higher than among those without (HR, 4.5; P <.001).

A major limitation of the study is the fact that it enrolled only 250 patients of the planned 300 patients. Thus, the CI for the percentage of patients with clinically significant arrhythmia is wider than that hypothesized per study design (12.2% vs 10.0%, respectively), due also to the higher-than-anticipated percentage of patients with arrhythmias (34.8% vs 25.0%, respectively).

“The INSPIRE-ELR study showed that there is high incidence of clinically significant arrhythmia early after MI detected by External Loop Recorder,” the study authors wrote. “ELR applied in patients with acute MI and LV dysfunction at the time of discharge identifies patients with high mortality risk.”

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference

Singh B, Rao HB, Pandurangi U, et al. Identifying high risk patients post myocardial infarction with reduced left ventricular function using loop recorders INSPIRE-ELR clinical study. Indian Heart J. Published online April 29, 2022. doi:10.1016/j.ihj.2022.04.010