The influence of adrenergic stimulation on sex differences in left ventricular twist mechanics

Abstract

Background. Sex differences in LV mechanics exist at rest and during acute physiological stress. Differences in cardiac autonomic and adrenergic control may contribute to sex differences in LV mechanics and LV hemodynamics. Accordingly, this study aimed to investigate sex differences in LV mechanics with altered adrenergic stimulation achieved through post handgrip exercise ischemia (PEI) and ß1-adrenergic receptor (AR) blockade. Methods and Results. 20 males (23±5 yr) and 20 females (22±3 yr) were specifically matched for LV length (males: 8.5±0.5 cm, females: 8.2±0.6 cm, p=0.163), and 2-dimensional speckle-tracking echocardiography was used to assess LV structure and function at baseline, during PEI and following administration of 5mg bisoprolol (ß1-AR antagonist). During PEI, LV end-diastolic volume and stroke volume were increased in both groups (p<0.001), as was end-systolic wall stress (p<0.001). LV twist and apical rotation weren’t altered from baseline or different between the sexes, however basal rotation increased in males (p=0.035). During ß1-AR blockade, LV volumes were unchanged but blood pressure and heart rate were reduced in both groups (p<0.001). LV apical rotation (p=0.036) and twist (p=0.029) were reduced in males with ß1-AR blockade but not females, resulting in lower apical rotation (males: 6.8±2.1º, females: 8.8±2.3º, p=0.007) and twist (males: 8.6±1.9º, females: 10.7±2.8º, p=0.008), and slower untwisting velocity (males: 68.2±22.1º⋅s-1, females: 82.0±18.7º⋅s-1, p=0.046) compared to females. Conclusions. LV twist mechanics are reduced in males compared to females during reductions to adrenergic stimulation, providing preliminary evidence that LV twist mechanics may be more sensitive to adrenergic control in males than in females.