Correlation of Sex Hormones and Contractile Function of Patients Undergoing CABG Procedure

Objective: Testosterone has been shown to impact cardiac contractility in males since its deficiency decreases the contraction and relaxation of the heart. Low testosterone levels are associated with coronary heart disease morbidity and mortality in men. However, in women the impact of sex hormones on cardiac contractility is more conflicting since studies are opposing. To clarify an association of sex hormones and myofilament function, we tested calcium-induced force development and assessed sex hormone levels in 107 patients undergoing coronary artery bypass grafting (CABG).

Methods: 93 male and 14 female patients, scheduled for elective coronary artery bypass grafting (CABG), were included in this study. Left and right atrial auricle tissue was harvested and prepared for skinned fiber measurements. The skinned myofilaments were exposed to stepwise increase of calcium concentration (pCa) and force values were recorded. Pre- and postoperatively 17ßEstradiol and testosterone levels were assessed.

Results: Preoperative testosterone levels were significant different between male and female patients (Males 4.09 ± 0.4 µg/l vs. females 0.69 ± 0.008 µg/l, p 0.01). Preoperative 17ßEstradiol levels were also significant different (males vs. females 42.93 ± 3.5 ng/l vs. 7.3 ± 2.54 ng/l, p 0.00001). In females, force values of LAA myofilaments correlated significantly with preoperative 17ßEstradiol levels at all steps of pCa (p < 0.05), but in RAA myofilaments (p > 0.05), there was no correlation with testosterone levels preoperatively. In males the force values of LAA and RAA myofilaments correlated significantly with preoperative testosterone and 17ßEstradiol levels (p < 0.05). Calcium induced force levels were not statistically significant among groups.

Conclusion: These preliminary results indicate a correlation between sex hormones and contractile properties in left and right atrial auricle fibers. In males we observed a positive correlation of force values with testosterone and 17ßEstradiol in LAA and RAA myofilaments, whereas in females force values showed a positive correlation only with 17ßEstradiol in LAA myofilaments. Considering the significant decreased 17ßEstradiol values in females compared with males as well as the similar force development in both groups, the female „advantage“ seems to revoked in postmenopausal women.