Syncope is broadly classified into reflex-mediated (60% to 70%), orthostatic (10%), and cardiac (10% to 20%). Cerebrovascular causes were removed from American and European guidelines (or listed as a rare cause). When working up syncope, a history and physical exam along with an electrocardiogram (ECG) will have a diagnostic yield of 88% for most cases of syncope, and this should be the starting point for most cases. An ECG is a class I recommendation in the guidelines for the workup of syncope. Orthostatic vitals are an underutilized part of the physical examination in syncope (only 27% to 38% in studies) and are also recommended for most cases.
Pulmonary embolism (PE) is an increasingly feared cause of syncope. The Pulmonary Embolism in Syncope Italian Trial, or PESIT, from 2016 found that 17% of admitted patients with a first-event syncope had a diagnosis of PE when tested. However, a large number of patients in that trial were discharged home from the emergency department after being diagnosed with reflex, drug-induced, or orthostatic syncopal events. Hence, only 3.8% of patients who presented to the hospital with syncope were found to have PE. Two-thirds of these patients had large-vessel PE, while one-fourth of the PE patients had no clinical manifestations of the disease (i.e., tachypnea, tachycardia, hypotension, or clinical signs of deep vein thrombosis). Other retrospective studies found a PE prevalence in syncope of 0.8% to 2.5%. The presenters concluded that it might be beneficial to get a Well’s Score and D-dimer in patients with the first episode of syncope unless an obvious reason is present. Imaging should be obtained depending on the score and or D-dimer.
Neurological testing for syncope, including routine computed tomography (CT) scan of the head and electroencephalogram (EEG) is done in more than 50% of patients in a retrospective cohort study with a diagnostic yield of just 1.5%. Most societies and guidelines recommend not pursuing any brain imaging (CT, MRI, carotid ultrasound, or EEG) in simple syncope with a normal neurological exam, no history of trauma, and the absence of seizure features (such as tongue bites).
The role of routine echocardiograms has always been questioned for syncope. A summary of multiple retrospective cohort studies revealed that the yield of an echocardiogram in patients with normal history, physical examination, and ECG was only about 1% while the cost was $1,500-$2,000 per study. The yield of an echocardiogram in patients with an abnormal ECG went up to about 17%. The guidelines currently support the use of an echocardiogram only if a structural abnormality of the heart is suspected.
While tilt table testing is not readily available in most inpatient units, its utility has always left something to be desired, outside of board exam questions. The presenters compared the traditional and fast versions of the test. Finally, they concluded that it was likely useful in cases where there is recurrent syncope of unclear origin as it might help diagnose reflex and delayed orthostatic syncope. However, it could be positive for cardiac cases as well.
Dr. Mehta
Dr. Mehta is an academic hospitalist and medical director, an assistant professor of medicine, and clinical core faculty with the internal medicine residency, and has roles in quality improvement, program evaluation, and improvement, and medical education at the University of Cincinnati.