Abstract Body (Do not enter title and authors here): Background: Growing evidence suggests that blunted blood pressure and heart rate responses to acute psychological stress independently associate with an increased risk of adverse outcomes in individuals with CHD, but assessment of mental stress reactivity in clinical settings is resource intensive. An alternative approach is to passively measure stress physiology at home with wearables, which is easier to translate into clinical practice. We tested the hypothesis that blunted mental-stress hemodynamic reactivity in the lab is associated with digital biomarkers of autonomic inflexibility at home.

Methods: We conducted a mental stress test in 239 participants (age < 60 years) with an MI within 8 months. Participants underwent a speech stressor task in front of an audience to induce mental stress, during which blood pressure and heart rate were measured repeatedly during a baseline 15-minute rest period and 5-minute stress challenge. Participants went home with a 7-day Holter monitor to measure autonomic function. We examined vagal autonomic inflexibility with deceleration capacity (DC), a digital biomarker calculated via phase rectified signal averaging of heart rate intervals. We also examined low frequency (LF) heart rate variability (HRV), an indirect measure of baroreceptor sensitivity. We measured mean values from 5-minute windows during sedentary periods only to avoid confounding due to physical activity. We used multivariable linear regression models to adjust for potential confounding due to age, beta-blockers, and sex.

Results: The mean age was 52 years, 51% were black, and 36% were women. Lower DC most strongly associated with a blunted change in heart rate during acute mental stress challenge (adjusted p<0.0001), followed by rate pressure product (p=0.01), systolic blood pressure (p=0.02), and diastolic blood pressure (p=0.035). The results were similar for LF HRV. We also found that the relationship was stronger in women than in men, especially for heart rate changes with stress and LF HRV (figure). Each 10 BPM reduction in heart rate reactivity associated with a 14% and 7% reduced DC in women and men, respectively. Corresponding reductions for LF HRV were 30% and 13% (p<0.05 for all).

Conclusions: In young and middle-aged individuals with recent MI, laboratory-induced hemodynamic changes with stress associate with digital biomarkers of autonomic inflexibility during sedentary periods, especially in women.