Dizzy spells and syncope: investigation and management

Syncope is a common and important cause of morbidity that accounts for 3% of visits to A&E and 6% of all emergency admissions. The incidence rises with age (23% of those >65 years of age have experienced syncope) and recurrence is common (60% at one year). Most cases are mediated by inappropriate vasodilation – simple faints, situational syncope (e.g. micturition syncope), and the vasovagal syndrome. Cardiac syncope is strongly associated with structural heart disease and is due to a sudden drop in cardiac output that may be due to a mechanical problem (e.g. aortic stenosis) or an arrhythmia; it is relatively rare (approximately 10% of all causes of syncope) but is associated with an adverse prognosis. In most cases, a working diagnosis can be established on the basis of a careful history, clinical examination and simple investigations including carotid sinus massage and a 12-lead ECG. Identifying common pathology (e.g. cervical spondylosis) does not prove that this is responsible for the patients’ symptoms. Ambulatory ECG findings are of little value unless they coincide with typical symptoms. Obtaining a clear history and establishing whether or not there is evidence of structural heart disease are crucial early objectives. Tilt testing is often helpful in patients with recurrent unexplained syncope and a structurally normal heart; on the other hand, prolonged ECG monitoring is the key investigation in patients with unexplained syncope and co-existing heart disease.