The protective role of sex hormones in females and exercise prehabilitation in males on sternotomy-induced cranial hypoperfusion in aortic banded mini-swine

During cardiac surgery, specifically sternotomy, cranial hypoperfusion is linked to cerebral ischemia, increased risk of perioperative watershed stroke, and other neurocognitive complications. The purpose of this study was to retrospectively examine the effect of sex hormones in females and exercise prehabilitation in males on median sternotomyinduced changes in cranial perfusion in a large animal model of heart failure. Cranial blood flow (CBF) before and 10 and 60 min poststernotomy was analyzed in eight groups of Yucatan miniswine: female control, aortic banded, ovariectomized, and ovariectomized + aortic banded; male control, aortic banded, aortic banded + continuous exercise trained, and aortic banded + interval exercise trained. A median sternotomy decreased cranial perfusion during surgery in all pigs (similar to 24 +/- 2% relative to baseline; P <= 0.05). CBF was 30 +/- 7% lower across all time points in all females vs. all males (P <= 0.05) and sternotomy decreased cranial perfusion (P <= 0.05) independent of sex (females = 34 +/- 3% and males = 14 +/- 3%) and aortic banding (intact control = 31 +/- 5% and intact aortic banded = 31 +/- 4%). CBF recovery at 60 min tended to be better in females vs. males (relative to 10 min poststernotomy, females = 23 +/- 13% vs. males = -1 +/- 5%) and intact aortic banded vs. control pigs (relative to 10 min poststernotomy, aortic banded = 43 +/- 20% vs. control = 6 +/- 16%; P <= 0.05) at 60 min poststernotomy. Ovariectomy impaired CBF recovery during cranial reperfusion 60 min following sternotomy (relative to baseline, all intact females = -1 +/- 9% vs. all ovariectomized females = -15 +/- 4%; P <= 0.05). Chronic exercise training completely prevented significant sternotomy- induced cranial hypoperfusion independent of aortic banding (sternotomyinduced deficit, all sedentary males = -24 +/- 6% vs. all exercisetrained males = -7 +/- 3%; P <= 0.05). Female sex hormones protected against impaired CBF recovery during reperfusion, while chronic exercise training prevented sternotomy- induced cranial hypoperfusion despite cardiac pressure overload. NEW & NOTEWORTHY Our findings suggest a median sternotomy may predispose patients, possibly postmenopausal women and sedentary men, to perioperative cerebral ischemia, an increased risk of cardiac surgery-related stroke, and resulting neurocognitive impairments. Specifically, data from this common surgical procedure show:1) median sternotomy independently decreases cranial perfusion; 2) female sex hormones improve cranial blood flow recovery following sternotomy; and 3) exercise prehabilitation prevents sternotomy- induced cranial hypoperfusion. Exercise prehabilitation before cardiac surgery may be advantageous for capable patients.