Telemedical cardiac risk assessment by implantable cardiac monitors in post-infarction patients with autonomic dysfunction (SMART-MI-DZHK9): gender differences and outcomes

Background

Cardiac autonomic dysfunction identifies high-risk patients after myocardial infarction (MI). Telemedical cardiac risk assessment by implantable cardiac monitors (ICM) after MI was recently identified as an effective method to early detect subclinical, but prognostically relevant serious arrhythmic events (SArE). Clinical complications in female patients after MI usually present with atypical symptoms. Therefore, early detection of prognostically relevant SArE in females would be of great clinical interest.

Purpose

In this pre-specified analysis of the SMART-MI trial we aimed to assess the impact of gender on detection of SArE and subsequent clinical complications.

Methods

SMART-MI was a prospective, randomised trial. Survivors of acute MI with preserved left-ventricular ejection fraction (LVEF 36–50%) and abnormal periodic repolarization dynamics (≥5.75deg2) and/or deceleration capacity (≤2.5ms) were randomly assigned to ICM-based telemedical monitoring or conventional follow-up. Primary endpoint was time to detection of SArE defined as the composite of atrial fibrillation ≥6 minutes, atrioventricular block ≥IIb, or fast non-sustained (>187 bpm;≥40 beats)/sustained ventricular tachycardia/fibrillation. Clinical complications were defined as the composite of mortality, stroke, systemic arterial thromboembolism, and hospitalization for decompensated heart failure. The effect of intervention on the primary endpoint was tested using Cox-regression analysis. The effect of SArE on clinical complications was evaluated by introducing SArE as time-dependent covariate.

Results

Between May 12, 2016, and July 20, 2020, 1305 individuals were screened and 400 patients were randomly assigned to ICM-implantation (N=201; 49 females) or conventional follow-up (control group; N=199; 29 females). During a median follow-up of 21±23 months, SArE were detected in 60 (30%; 12 females) patients in the ICM and 12 (6%; 1 female) patients in the control group. In both males and females ICM-implantation was associated with a higher detection rate of SArE (HR 6.33; 3.28–12.23; p<0.001 in males and HR 8.49; 1.10–65.66; p=0.040 in females; p-interaction = 0.790; Figure 1). In both male and female patients, detection of SArE was prognostic for subsequent clinical complications (HR 3.64; 1.89–7.02; p<0.001 in males and HR 16.19; 4.76–55.11 in females; p<0.001). The association between SArE and clinical complications was significantly higher in females than males. Among the 13 females with detected SArE, 6 developed clinical complications within a median period of 25±18 months, compared to 12 complications out of 59 SArE within 18±13 months among males (Figure 2; p-interaction = 0.030).

Conclusion

Telemedical monitoring with ICM was highly effective in early detection of subclinical, prognostically relevant SArE in both female and male patients. However, the association of a detected SArE with a subsequent clinical complication was significantly higher among females.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsches Zentrum für Herz und Kreislaufforschung (DZHK) and Medtronic Bakken Research Center