An approach to the clinical assessment and management of syncope in adults

Abstract

Syncope, defined as a brief loss of consciousness due to an abrupt fall in cerebral perfusion, remains a frequent reason for medical presentation. The goals of the clinical assessment of a patient with syncope are twofold: (i) to identify the precise cause in order to implement a mechanism-specific and effective therapeutic strategy; and (ii) to quantify the risk to the patient, which depends on the underlying disease, rather than the mechanism of the syncope. Hence, a structured approach to the patient with syncope is required. History-taking remains the most important aspect of the clinical assessment. The classification of syncope is based on the underlying pathophysiological mechanism causing the event, and includes cardiac, orthostatic and reflex (neurally mediated) mechanisms. Reflex syncope can be categorised into vasovagal syncope (from emotional or orthostatic stress), situational syncope (due to specific situational stressors), carotid sinus syncope (from pressure on the carotid sinus, e.g. shaving or a tight collar), and atypical reflex syncope (episodes of syncope or reflex syncope that cannot be attributed to a specific trigger or syncope with an atypical presentation). Cardiovascular causes of syncope may be structural (mechanical) or electrical. Orthostatic hypotension is caused by an abnormal drop in systolic blood pressure upon standing, and is defined as a decrease of >20 mmHg in systolic blood pressure or a reflex tachycardia of >20 beats/minute within 3 minutes of standing. The main causes of orthostatic hypotension are autonomic nervous system failure and hypovolaemia. Patients with life-threatening causes of syncope should be managed urgently and appropriately. In patients with reflex or orthostatic syncope it is important to address any exacerbating medication and provide general measures to increase blood pressure, such as physical counter-pressure manoeuvres. Where heart disease is found to be the cause of the syncope, a specialist opinion is warranted and where possible the problem should be corrected. It is important to remember that in any patient presenting with syncope the main objectives of management are to prolong survival, limit physical injuries and prevent recurrences. This can only be done if a patient is appropriately assessed at presentation, investigated as clinically indicated, and subsequently referred to a cardiologist for appropriate management.