Severe aortic stenosis (AS) poses the greatest perioperative risk. This is because, if hypotension occurs during anaesthesia and surgery, it can be a difficult problem to correct. AS is a fixed obstruction and limits maximum cardiac output during stress. Patients cannot respond normally to the peripheral dilation associated with anaesthesia and blood pressure can fall dramatically. This causes myocardial ischaemia, as the myocardial hypertrophy seen in AS is associated with increased oxygen demand. AS may be asymptomatic and patients with severe stenosis do not necessarily exhibit classical features on examination. According to the Helsinki Ageing Study, 3% people aged 75-85 have critical aortic stenosis.
It is also important to recognise mitral stenosis because it is necessary to control the heart rate in order to preserve diastole. This aids filling of the left atrium and generates enough pressure to squeeze blood through the stenosed valve. The presence of any murmur requires a preoperative echocardiogram, and antibiotic prophylaxis is required for most patients with valve disease undergoing surgery.
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