Diagnostic Approach to Syncope

Initial Evaluation

The initial evaluation of syncope should include a careful history, physical examination including orthostatic blood pressure measurements, and a 12-lead electrocardiogram (ECG), which can establish a diagnosis in up to 50% of cases 1, 2, 3
A detailed history focusing on circumstances before the attack, precipitating events, prodromal symptoms, eyewitness account, and recovery phase symptoms is essential 1, 3
A comprehensive physical examination with focus on complete cardiovascular examination and orthostatic blood pressure measurements is crucial 1, 2
A 12-lead ECG should be obtained to identify arrhythmias, conduction abnormalities, and evidence of ischemia or prior infarction 1, 3

Neurally mediated syncope is the most common type, including classical vasovagal syncope and situational syncope 3
Orthostatic syncope is defined as a decrease in systolic BP ≥20 mmHg or decrease to <90 mmHg upon standing, and is common in elderly and those on medications causing hypotension 1, 3
Cardiac syncope can be due to arrhythmia-related causes, structural heart disease, or ischemia-related causes 3, 4

High-risk features include abnormal ECG findings, history of structural heart disease or heart failure, syncope during exertion or in supine position, absence of prodromal symptoms, family history of sudden cardiac death, older age, and low blood pressure 1
Low-risk features include younger age, no known cardiac disease, normal ECG, syncope only when standing, presence of prodromal symptoms, and specific situational triggers 1

If the initial evaluation is diagnostic, no further testing is needed for classical vasovagal syncope or situational syncope, but orthostatic syncope and cardiac syncope require confirmation with orthostatic BP measurements or ECG evidence of ischemia or arrhythmia 1, 3
If the initial evaluation suggests a diagnosis, further testing such as echocardiography, exercise stress testing, or prolonged ECG monitoring may be necessary 1

Targeted blood tests based on clinical assessment, such as CBC, electrolytes, or cardiac biomarkers, may be ordered 1
Brain imaging (CT/MRI) is not recommended routinely, but may be indicated with focal neurological findings, and has a low diagnostic yield 1
EEG is not recommended routinely, but may be indicated if seizure activity is suspected, and has a low diagnostic yield 1

Pediatric and young patients most commonly have neurocardiogenic syncope 4
Elderly patients have a higher frequency of cardiac causes and orthostatic hypotension 4
Patients with unexplained syncope and structural heart disease have a higher mortality risk 5