Estrogen increases exercise capacity in cardiac syndrome x: Role of oxidative stress

Abstract

Background: Cardiac syndrome X (CSX) or exertional angina despite normally appearing coronaries more often occurs in women, especially postmenopausal women (PMW), than in men. Estrogen Replacement Therapy (ERT) has been shown to alleviate CSX symptoms. We hypothesized that ERT would improve exercise capacity in postmenopausal women (PMW) having CSX via a possible restoration of vasoregulatory function as cardiopulmonary function is otherwise normal in CSX. Methods: Spiroergometry (rising workload by 25 Watt every three minutes until exhausted or symptomatic) was performed in 12 PMW with CSX before and after a 48-days period of ERT (2mg/d estradiol), other medications remained unchanged. Ventilatory threshold (VO2vt)- and peak oxygen consumption (VO2max) were determined as measures of exercise capacity. The diagnosis CSX was established previously by normal coronary angiograms, yet angina-limited stress tests. Results: VO2vt and VO2max (mean±SEM, ml/kg/min) were significantly increased after 48 days of ERT. VO2vt before: 12.3±0.6, after ERT:14.4±0.6 (p=0.01). VO2max before ERT: 18.2±1.1, after ERT: 21.8±1.2 (p<0.03). The increase in aerobic capacity was not obscured by a 1.7%±0.7% (p=0.04) weight gain during ERT. Plasma malondialdehyde as a marker of oxidative stress decreased by 18% (±9.5%, p=0.06). Conclusions: For the first time, ERT was shown to increase exercise capacity in CSX. Antioxidant estrogenic actions may affect endothelial function and, thereby, coronary regulation.