Current investigations used to assess syncope

Following a thorough history, physical examination, and electrocardiography, the cause of syncope remains undiagnosed in around 50% of patients.1 Diagnostic investigations are performed to confirm a suspected diagnosis or to explore another potential cause. When exploring the cause of syncope, features of the initial history and examination should direct the investigations wherever possible. The usefulness of a test can be described in various terms. The sensitivity of a test measures how effective it is in detecting those individuals who are truly diseased (true positives). The specificity of a test measures how effective it is in detecting those individuals who are not diseased (true negatives). The positive predictive value of a test is the probability of actually having a condition given that the test result is positive. The negative predictive value is the probability of not having the disease given that the test is negative. The diagnostic yield of a test is defined by the percentage of patients who receive a diagnosis or have a diagnosis confidently dismissed as a consequence of the test. That is the sum of the number of true positives and, if available, true negatives as a proportion of the total number of tests performed. Information gained from the history or physical examination usually indicates whether or not echocardiography would be useful. The diagnostic yield in the absence of historical, physical, or electocardiographic findings is low.2 However, when clinical heart disease is suspected the echocardiogram is very useful for confirming valvar abnormalities, ventricular hypertrophy, and ventricular dysfunction. Those who experience syncope on exertion in the absence of ventricular outflow tract obstruction should undergo exercise testing. During exercise, increased levels of circulating catecholamines may precipitate ventricular tachycardia in those with ischaemia or catecholamine sensitive ventricular tachycardia. Once again the history alone should direct the clinician towards …