We infused dobutamine (20 microgram/kg per min) intravenously, once before and once after coronary artery occlusion, in 10 chronically instrumented dogs. Both infusions increased cardiac output and left ventricular dP/dt and dP/dt/P, but divergent effects on heart rate and aortic blood pressure were observed. Dobutamine decreased heart rate and increased mean aortic blood pressure before coronary artery occlusion, whereas after occlusion it increased heart rate while mean aortic blood pressure remained unchanged. A greater decrease in total peripheral vascular resistance occurred during dobutamine infusion after coronary artery occlusion than before. These differences may relate to withdrawal of enhanced sympathetic tone after coronary occlusion. Similar infusions of normal saline (n = 9) produced no systemic hemodynamic changes either before or after coronary artery occlusion. Myocardial blood flow increased to both non-ischemic and ischemic regions of the heart during dobutamine infusion, but the endocardial:epicardial blood flow ratio did not change significantly. In addition, infarct size, measured by nitroblue tetrazolium stain, was smaller in the dobutamine group (10 +/- 1 g) than in the normal saline group (15 +/- 2 g). Neither left ventricular weight nor risk zone differed between the two groups. These results indicate that dobutamine may be a useful inotropic agent during acute myocardial infarction.

Our results provide evidence for localised arterial differences, which occur more extensively in peripheral vessels (brachial and femoral). Chronically, vascular remodelling may occur as a result of the specific haemodynamic conditions within each vessel, which likely differs depending on the mode of exercise. In the future, empirical research is needed to understand the effect of resistance training on chronic vascular remodelling, as this is not well documented.

Introduction: Post-menopausal women have lower resting cardiac function than premenopausal women, but whether the menopause influences maximal cardiac output and hence exercise capacity is unclear. It is possible that pre-and post-menopausal women achieve similar improvements in peak aerobic capacity (V O 2peak ) and cardiac output with exercise training via different regional left ventricular muscle function ("LV mechanics"), as suggested by in vitro and animal studies. The aim of this study was to investigate the effects of the menopause on LV mechanics and adaptations to exercise training. Methods: Twenty-five healthy untrained middle-aged women (age 45-58 years; 11 pre-menopausal, 14 post-menopausal) completed 12 weeks of exercise training. Before and after exercise training, (i)V O 2peak and blood volume were determined, and (ii) LV mechanics were assessed using echocardiography at rest and during two submaximal physiological tests -lower body negative pressure (LBNP) and supine cycling. Results: The increase in relativeV O 2peak after exercise training was 9% smaller in post-menopausal than premenopausal women, concomitant with a smaller increase in blood volume (P < 0.05).However, cardiac output and LV volumes were not different between pre-and postmenopausal women (P > 0.05) despite altered regional LV muscle function, as indicated by higher basal mechanics in pre-menopausal women during the physiological tests after exercise training (P < 0.05). Conclusion: These findings are the first to confirm altered LV mechanics in post-menopausal women. In addition, the reduced aerobic adaptability to exercise training in post-menopausal women does not appear to be a central cardiac limitation, and may be due to altered blood volume distribution and lower peripheral adaptations.1 removed: Twenty-five healthy untrained 2 removed: completed

Arterial wall mechanics likely play an integral role in arterial responses to acute physiological stress. Therefore, this study aimed to determine the impact of low and moderate intensity double‐leg press exercise on common carotid artery (CCA) wall mechanics using 2D vascular strain imaging. Short‐axis CCA ultrasound images were collected in 15 healthy men (age: 21 ± 3 years; stature: 176.5 ± 6.2 cm; body mass; 80.6 ± 15.3 kg) before, during, and immediately after short‐duration isometric double‐leg press exercise at 30% and 60% of participants' one‐repetition maximum (1RM: 317 ± 72 kg). Images were analyzed for peak circumferential strain (PCS), peak systolic and diastolic strain rate (S‐SR and D‐SR), and arterial diameter. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP) were simultaneously assessed and arterial stiffness indices were calculated post hoc. A two‐way repeated measures ANOVA revealed that during isometric contraction, PCS and S‐SR decreased significantly (P < 0.01) before increasing significantly above resting levels post exercise (P < 0.05 and P < 0.01, respectively). Conversely, D‐SR was unaltered throughout the protocol (P = 0.25). No significant differences were observed between the 30% and 60% 1RM trials. Multiple regression analysis highlighted that HR, BP, and arterial diameter did not fully explain the total variance in PCS, S‐SR, and D‐SR. Acute double‐leg press exercise is therefore associated with similar transient changes in CCA wall mechanics at low and moderate intensities. CCA wall mechanics likely provide additional insight into localized intrinsic vascular wall properties beyond current measures of arterial stiffness.