title: Females have greater left ventricular twist mechanics than males during acute reductions to preload.
abstract: Compared to males, females have smaller left ventricular (LV) dimensions and volumes, higher ejection fractions (EF), and higher LV longitudinal and circumferential strain. LV twist mechanics determine ventricular function and are preload-dependent. Therefore, the sex differences in LV structure and myocardial function may result in different mechanics when preload is altered. This study investigated sex differences in LV mechanics during acute challenges to preload. With the use of conventional and speckle-tracking echocardiography, LV structure and function were assessed in 20 males (24 ± 6.2 yr) and 20 females (23 ± 3.1 yr) at baseline and during progressive levels of lower body negative pressure (LBNP). Fourteen participants (8 males, 6 females) were also assessed following a rapid infusion of saline. LV end-diastolic volume, end-systolic volume, stroke volume (SV), and EF were reduced in both groups during LBNP (P < 0.001). While males had greater absolute volumes (P < 0.001), there were no sex differences in allometrically scaled volumes at any stage. Sex differences were not detected at baseline in basal rotation, apical rotation, or twist. Apical rotation and twist increased in both groups (P < 0.001) with LBNP. At -60 mmHg, females had greater apical rotation (P = 0.009), twist (P = 0.008), and torsion (P = 0.002) and faster untwisting velocity (P = 0.02) than males. There were no differences in mechanics following saline infusion. Females have larger LV twist and a faster untwisting velocity than males during large reductions to preload, supporting that females have a greater reliance on LV twist mechanics to maintain SV during severe reductions to preload.
authors.affiliation: Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, The University of British Columbia, Kelowna, Canada; and.
authors.forename: Alexandra M
authors.initials: AM
authors.lastname: Williams
authors.affiliation: Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom.
authors.forename: Rob E
authors.initials: RE
authors.lastname: Shave
authors.affiliation: Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, The University of British Columbia, Kelowna, Canada; and Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom.
authors.forename: Mike
authors.initials: M
authors.lastname: Stembridge
authors.affiliation: Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, The University of British Columbia, Kelowna, Canada; and neil.eves@ubc.ca.
authors.forename: Neil D
authors.initials: ND
authors.lastname: Eves
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D062186:Arterial Pressure; D001696:Biomechanical Phenomena; D004452:Echocardiography; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008150:Lower Body Negative Pressure; D008297:Male; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D012737:Sex Factors; D012965:Sodium Chloride / Q000008:administration & dosage; D013318:Stroke Volume; D013997:Time Factors; D054159:Torsion, Mechanical; D016277:Ventricular Function, Left; D055815:Young Adult
chemical_list: D012965:Sodium Chloride
keywords: echocardiography; mechanics; sex