Cardiac autonomic dysfunction in elderly women with myocardial infarction

AIMS: Elderly women with myocardial infarction (MI) show poorer outcomes than men. In patients with MI, reduced heart rate variability (HRV) is associated with an increased risk of mortality. Thus, we aimed to investigate HRV in elderly women with MI. METHODS: HRV indexes in women 50 years of age or older were compared to those in age-adjusted men with MI: geometric (triangular index), linear (low frequency [LF, ms(2)], high frequency [HF, ms(2)], standard deviation (SD) of normal R-R wave intervals [SDNN], square root of the mean of the sum of the squares of differences between adjacent normal R wave intervals [RMSSD]) and nonlinear Poincaré analysis [SD1 and SD2, ms]. RESULTS: Women had higher MI recurrence than men (11% vs. 5% with two MIs; 6% vs. 1% with three MIs). Overall HRV, the triangular index and SDNN were considerably lower in women than men (3.1 [2.5-4.4] vs. 4.5 [3.2-5.9] and 9.3 [6.9-15.8] vs. 19.2 [11.4-26.4] respectively; p < 0.001). Moreover, HRV indexes (HF, LF/HF, RMSSD, and SD1) were significantly lower in women (62.2%, 55.6%, 37.1%, and 37.2% respectively; p < 0.01). CONCLUSION: This study suggests that elderly women with MI may have a worse prognosis than men, indicated by cardiac autonomic dysfunction. Since our study is cross-sectional and cannot infer causality, causation should be confirmed in further longitudinal studies.