George W X Barker
Atrial fibrillation is a common supraventricular tachycardia that is associated with cardiovascular disease, hypertension and heart failure. It is caused by abnormal electrical activity in the atria, prevents coordinated atrial contractions, and can be split into three classes: paroxysmal, persistent and permanent. Treatment provided is in the form of rate or rhythm control. As atrial fibrillation can increase the risk of ischaemic strokes, anticoagulation is critical in preventing thrombotic sequalae, balanced against the risk of bleeding. Additionally, haemodynamically unstable atrial fibrillation is characterised by perfusion failure and must be managed urgently.
The space environment poses unique challenges in cardiovascular physiology, in part, due to the thoracic fluid shift experienced in microgravity. This is associated with a decreased plasma volume and left ventricular mass, and changes in heart structure have been linked to arrhythmia formation. High levels of radiation have been associated with the development of coronary artery disease. Whilst arrhythmias have been reported in astronauts, it is difficult to determine whether these are a direct result of the space environment.
With exploration class missions to Mars on the horizon, the detection, treatment and management of atrial fibrillation during long duration spaceflight must be considered. Recommendations include the use of intraosseous amiodarone because of difficulties associated with intravenous access and cardioversion in microgravity. Improved radiation shielding could prevent damage to coronary arteries. Increased medical autonomy and a medical practitioner aboard could lead to better outcomes through their ability to deliver higher level care, experience in clinical decision making, and a likely unavailability of evacuation capability. Astronaut selection, as a means of prevention, and increased cardiovascular monitoring could also be critical in the development of a complete management strategy for atrial fibrillation that protects astronauts’ health and helps ensure mission success.
The space environment poses unique challenges in heart physiology, in part, due to the fluid shifting from the lower body, to the upper body, which is experienced in microgravity. This is associated with a decreased total volume of blood being present in blood vessels, the left side of the hear growing in mass, and changes in heart structure have been linked to electrical disturbances, such as atrial fibrillation. High levels of radiation have been associated with the development of blood vessel disease. Whilst electrical abnormalities have been reported in astronauts, it is difficult to determine whether these are a direct result of the space environment.
With long missions to Mars on the horizon, the detection, treatment and management of atrial fibrillation during long duration spaceflight must be considered. Recommendations include the use of a rhythm controlling drug, amiodarone, given directly via a needle into the bone, because of difficulties associated with vascular access and emergency electrical treatment/defibrillation in microgravity. Improved radiation shielding could prevent damage to blood vessels. Increased autonomy and a doctor aboard could lead to better outcomes through their ability to deliver higher level care, experience in clinical decision making, and a likely unavailability of evacuation capability. Astronaut selection, as a means of prevention, and increased heart monitoring could also be critical in the development of a complete management strategy for atrial fibrillation that protects astronauts’ health and helps ensure mission success.