Identifying High Risk Patients With Syncope

BACKGROUND: Syncope is a common medical problem with up to 30 percent of normal individuals reporting one or more syncopal episodes. Thus, physicians of all specialties are frequently confronted by patients with syncope. The spectrum of diseases which may cause syncope is broad, ranging from common benign problems to severe life-threatening disorders. Because of the complexity of the clinical situation when an obvious cause for syncope is not found, patients may be subjected to a significant period of hospitalization and a large number of diagnostic tests. Retrospective and prospective studies have shown that many diagnostic tests are frequently employed but are infrequently diagnostic of a cause of syncope. Thus, studies have shown that when a cause is established or suggested, the majority of diagnoses are assigned based on initial history and physical examination. An initial electrocardiogram is helpful in assigning a cause of syncope in only approximately five percent of additional patients. In a prior study prolonged electrocardiographic monitoring was helpful in assigning a cause of syncope in approximately fifteen percent of patients. Other studies of prolonged electrocardiographic monitoring in patients with syncope reveal that arrhythmias as a potential cause of syncope are found in eleven to sixty-four percent of patients. Diagnostic procedures such as EEG, head CT scan, brain scan, cerebral angiography, echocardiography, and cardiac catheterization rarely establish a cause of syncope but are useful when employed selectively for diagnosis of specific etiologies of syncope. These studies of diagnostic evaluation of syncope, therefore, clearly indicate that there is a subgroup of patients with syncope who have arrhythmias as a cause of their syncope which were not apparent from initial history, physical examination, and EKG. Therefore, prolonged electrocardiographic monitoring has assumed a central role in the diagnostic evaluation of this group of patients for detection of arrhythmias. Because of the prognostic and therapeutic importance of arrhythmias causing syncope, it is important to identify patients who are likely to have arrhythmias from the data available at presentation. There were no studies prior to 1987 attempting to identify such patients at presentation. The predictors of diagnostic arrhythmias at presentation may be helpful for four reasons. First, the variables suggesting high likelihood of arrhythmias may provide a basis for decisions regarding the need for hospital admission. Secondly, predictors of diagnostic arrhythmias may identify patients who may need to be monitored immediately as opposed to electively. Thirdly, patients who have predictors of diagnostic arrhythmias may be more appropriate candidates for invasive diagnostic testing such as intracardiac electrophysiologic studies. Fourthly, since patients with arrhythmias are at high risk of sudden death, these predictors may identify an appropriate subset of patients for further studies involving therapeutic interventions. Since many patients with syncope have multiple risk factors for sudden death, the development of a multifactorial model to more effectively and expeditiously predict the degree of risk of sudden death may be important in the management of patients with syncope after initial presentation. DESIGN NARRATIVE: Two models were validated in this longitudinal study including one which predicted sudden death and one which predicted diagnostic arrhythmias on monitoring. The model for prediction of sudden death was developed in patients in whom a cause of syncope was not established by initial history and physical examination. The predictors in this model included a history of diabetes mellitus, renal insufficiency, left ventricular hypertrophy, left bundle branch block, and left axis deviation. The model of predictors of diagnostic arrhythmias was developed in patients in whom a cause of syncope was not established from initial history, physical examination, or EKG and included a history of ventricular tachycardia and an abnormal EKG by specific criteria. Patients with syncope were accrued from the emergency room, the inpatient services and the ambulatory clinics of the Presbyterian University Hospital of Pittsburgh. All patients underwent a basic standardized evaluation consisting of a history, physical examination, baseline laboratory tests, electrocardiogram, prolonged electrocardiographic monitoring, and special diagnostic tests as necessary. Diagnosis of a cause of syncope was assigned by standardized criteria. Follow-up information regarding sudden death and mortality was obtained at three-month intervals until the end of the study. Causes of death were assigned in a standardized manner. The study completion date listed in this record was obtained from the "End Date" entered in the Protocol Registration and Results System (PRS) record.