Cardiac Output

Right ventricular failure (RVF) is a common complication to cardiac surgery, which is associated to mortality, kidney failure, stroke, prolonged mechanical ventilation and ICU stay. The right ventricle is particularly vulnerable to an increased afterload. By increasing pulmonary vascular resistance (PVR), atelectasis might mitigate a negative effect on the right ventricle. Recruitment maneuvers have been shown to resolve atelectasis and improve hemodynamics by increasing cardiac output and lowering PVR. However these maneuvers transiently raise airway pressures, which in turn increases right ventricular afterload, a situation often poorly tolerated by patients with RVF. Prone position is used in patients with respiratory failure and has been shown to decrease mortality in patients with ARDS. Prone position decreases atelectasis and moves ventilation dorsally. In ARDS it also seems to mediate beneficial hemodynamic effects such as an increase in cardiac output and a decrease in PVR. The investigators hypothesis is that prone position early after cardiac surgery will increase cardiac output by recruitment of atelectasis and thereby decrease PVR.

The goal of this clinical trial is to learn whether temporary atrial pacing improves heart function after cardiac surgery under cardiopulmonary bypass (CPB). It will also help determine the best pacing rate during the first 24 hours after surgery. The main questions it aims to answer are: * Does atrial pacing improve cardiac output after surgery? * Is 70, 80, or 90 bpm the most effective pacing rate? * Does pacing reduce the risk of atrial fibrillation after surgery?

Based on the monitoring data of wearable devices, with cardiac output (CO) as the gold standard, this study intends to develop a non-invasive evaluation model of CO based on wearable data, and optimize the parameters to realize the cardiac capacity detection function in resting and exercise states on the wearable device.

Heat acclimation is when you repeatedly exposure yourself to heat so that your body adapts and better tolerates heat. This project will determine if completing a heat acclimation maintenance period after heat acclimation is more beneficial than heat acclimating alone for exercise performance in the heat. To determine this, participants will exercise in the heat before heat acclimation, after heat acclimation, and after heat acclimation maintenance. Researchers will assess the heart's pumping capacity, blood volume, body temperature, and exercise performance to determine which approach is more effective.

The goal of this clinical trial is to compare four different methods of reducing heart rate before cardiac imaging. The diagnostic imaging technique used in this study is called Computed Tomography (CT) of the coronary vessels (CCTA). Globally, approximately one-third of patients experience heart-related conditions. Because the heart is a moving organ, imaging presents challenges. A higher heart rate requires increased scanning power, which results in more images and, in some cases, higher radiation exposure that may be harmful. To address this issue, beta-blocker medication is administered before the examination to lower the heart rate. This medication can be given orally, intravenously, or both. While this approach is effective, the most optimal method remains uncertain. The objectives of this study are: * To determine whether oral administration of beta-blockers is as effective as intravenous administration in maintaining a stable heart rate during CT imaging. * To assess whether listening to music during the procedure improves patient comfort and overall experience. Participants will: * Be randomly assigned to one of four groups: * One group will receive beta-blocker medication orally. * Another group will receive beta-blocker medication intravenously. * One group will listen to music during the procedure. Participants will report their sensations and experiences before, during, and after the examination. The study investigators will compare the effectiveness of oral and intravenous beta-blockers, as well as the impact of music, in terms of: * Heart rate stability and reduction. * Participant-reported comfort and overall experience.