Characterisation of systolic and diastolic functions with echocardiography imaging in healthy populations subjected to stress manoeuvres

Normal ageing reduces the capacity of the heart as a pump. The hemodynamic consequences of ageing have been extensively investigated during maximal incremental exercise, however less in known about hemodynamics during submaximal steady-state exercise. In this regard, the exercise intensity at the gas exchange threshold (GET) is attractive as it discriminates the transition from moderate to heavy exercise. Moreover, Acute hypoxia (AH) is a challenge to the homeostasis of the cardiovascular system, especially during exercise. Research in this area is scarce. The aim of the present investigation was to compare the hemodynamics of healthy elderly and young subjects during an exercise bout conducted at the GET intensity and We aimed to ascertain whether echocardiographic, Doppler, and tissue Doppler measures were able to detect changes in systolic and diastolic functions during the recovery after mild exercise in AH. For the first research two groups of subjects were studied: the elderly group (EG), composed by 11 healthy physically active subjects older than 60 years, and the young group (YG), composed by 13 healthy subjects younger than 35 years. Both groups performed a 5-min rectangular exercise test (cycling) at the GET intensity. Hemodynamics were measured using an echocardiographic system. The main result was that the YG showed higher capacity to increase stroke volume than the EG (72.5 ± 16.7 vs. 52.4 ± 8.4 ml). This was the consequence of a higher capacity to increase cardiac pre-load and inotropism, and to a lower level in systemic vascular resistance. Moreover, the atrial contribution to ventricular diastolic filling was substantially higher in the YG with respect to the EG. These results suggest that normal ageing is characterised by several complex changes in hemodynamics during submaximal exercise and that all the main hemodynamic modulators (chronotropism, inotropism, pre-load, and afterload) are significantly affected by ageing. For the second study twelve healthy males (age 33.5 ± 4.8 years) completed a cardiopulmonary test on an electromagnetically braked cycle-ergometer to determine their maximum workload (Wmax). On separate days, participants performed randomly assigned two exercise sessions consisting in 3 min pedalling at 30% of Wmax: (1) one test was conducted in normoxia (NORMO) and (2) one in normobaric hypoxia with FiO2set to 13.5% (HYPO). Hemodynamics were assessed with an echocardiographic system. The main result was that the HYPO session increased parameters related to myocardial contractility such as pre-ejection period and systolic myocardial velocity with respect to the NORMO test. Moreover, the HYPO test enhanced early transmitral filling peak velocities. No effects were detected for left ventricular volumes, as end-diastolic, end-systolic, and stroke volume were similar between the NORMO and the HYPO test. Results of the present investigation support the hypothesis that a brief, mild exercise bout in acute normobaric hypoxia does not impair systolic or diastolic functions. Rather, it appears that stroke volume is well preserved and that systolic and early diastolic functions are enhanced by exercise in hypoxia. The general aim of both studies was to apply Doppler-Echocardiography tissue Doppler measures to investigate on systolic and diastolic functions during acute stressors in healthy populations. To this aim, submaximal exercise (study 1) and hypoxia (study 2) were applied. Taking together, both studies support the use of Echocardiography imaging to detect hemodynamic changes during manoeuvre able to stress the cardiovascular apparatus in healthy individuals.