Abstract
BackgroundThe impact of sex on cardiac morphology and function in chronic volume overload has been described in detail. However, the relation between sex and contractile properties at the actin-myosin level has not been well defined. Therefore, we evaluated the influence of sex on the contractile capacities of patients with chronic volume overload.MethodsIn 36 patients (18 males, 65 ± 9 years; 18 females, 65 ± 13 years) scheduled for elective mitral valve surgery due to severe mitral regurgitation (MR) with preserved left ventricular function, right auricle samples were obtained prior to extracorporal circulation. The fibers were prepared and skinned and exposed to a gradual increase in the calcium concentration (from pCa of 6.5–4.0) for calcium-induced force-developing measurements. Calcium sensitivity was also measured and recorded.ResultsThe pCa-force relationship of the fibers obtained from males and females was significantly different, with the force values of the female fibers greater than those of male fibers at maximum calcium concentrations (pCa of 4.0: 3.6 ± 0.3 mN versus 3.2 ± 0.4 mN, p 0.02) and pCa of 4.5 2.6 ± 0.6 versus 2.0 ± 0.5, p 0.002). In contrast, the force values of female fibers were lower at mean calcium concentrations compared to those of male fibers (at 5.5 and pCa of 6.0: 1.0 ± 0.3 mN versus 1.2 ± 0.5 mN, p 0.04; 0.61 ± 0.05 versus 0.88 ± 0.09, p 0.04).Calcium sensitivity was observed at pCa of 5.0 in females and pCa of 4.5 in males.ConclusionThis study demonstrated that female fibers from patients exposed to chronic volume overload developed higher force values at a given calcium concentration compared to fibers from male patients. We assume that female patients might tap the full force potential, which is required when exposed to the highest calcium concentrations in our experimental cycle. The calcium sensitivity among genders was significantly different, with the results suggesting that males have higher calcium sensitivity and might compensate for lower force values at maximal calcium concentrations by a higher affinity for calcium. Hence, female patients with MR seem to work more “energy efficient”.
Highlights
The impact of sex on cardiac morphology and function in chronic volume overload has been described in detail
Classical signs of heart failure are missing in female rats with induced volume overload
These data were supported by Dent and coworkers, who showed that volume overload in mice led to a greater increase in cardiac muscle mass and wall thickness than in female mice, without any changes in the ventricular diameter, whereas the ventricular dimensions increased and left ventricular end-diastolic pressure in male mice [11, 12]
Summary
The impact of sex on cardiac morphology and function in chronic volume overload has been described in detail. Evidence has long existed for sex differences in intrinsic cardiac contractile properties [5], positive inotropic responses to Ca2+ [6], Ca2+ channels in the heart [7], and hormone responsiveness [5, 8] In accordance with these results, recent studies suggested that sex Bening et al BMC Cardiovascular Disorders (2016) 16:197 hormones may attenuate remodeling processes in chronic volume overload and that sex may influence the development of cardiac pathologies in chronic volume overload [2, 3, 9–12]. Classical signs of heart failure are missing in female rats with induced volume overload These data were supported by Dent and coworkers, who showed that volume overload in mice led to a greater increase in cardiac muscle mass and wall thickness than in female mice, without any changes in the ventricular diameter, whereas the ventricular dimensions increased and left ventricular end-diastolic pressure in male mice [11, 12]. This demonstrates that sex modifies ventricular remodeling in rodents exposed to volume overload
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