Given the many possible causes of syncope, the diagnostic evaluation can be quite involved and expensive and the specific etiology may never be determined. Therefore, a carefully planned approach rather than a “shotgun” diagnostic strategy is important. The patient history, family history, physical examination, and an electrocardiogram are fundamental and direct the remainder of the evaluation. Table 17.2 details the components of a comprehensive syncope evaluation. The patient history is the cornerstone on which the syncope evaluation is constructed and the diagnosis depends; it is often, along with the physical examination and an ECG, all that is necessary. Important historical details from the patient include: the age of the patient (syncope is rare before 10 years of age except for breath-holding spells in the toddler), time of day of the event (early morning is typical), the state of hydration and nutrition at the time of the event (when last had fluid or food intake), the environmental conditions (i.e., ambient temperature), the patient’s activity or body position immediately prior to the syncopal episode, the frequency and duration of the episodes, and any aura, prodrome, or specific symptoms and signs prior to the episode. Witnesses, if available, should provide details regarding the patient’s condition prior to the syncope, duration of loss of consciousness, any injuries or seizure-like movements, heart rate during episode (rarely available), and duration and nature of recovery (often patients are sleepy after neurocardiogenic syncope (NCS)). Medications (prescriptions and/or over-the-counter) used by the patient are critical historical points particularly regarding proarrhythmic agents such as QT prolonging medications. Information regarding prior diagnostic reports and/or consultations can prevent duplicate testing.

Family history is vital in the evaluation of syncope. It is not uncommon to find a history of multiple family members who experienced syncope during adolescence. Many of the older family members may also report a history of low blood pressure, and many families limit salt due to a hypertensive family member who is on a salt-restricted diet. However, if the family history is positive for recurrent syncope, it is also important to consider other familial disorders by specific questioning about the presence of hypertrophic or dilated cardiomyopathy, long QT syndrome (and other ion channelopathies), primary pulmonary hypertension, or arrhythmogenic right ventricular dysplasia. Families should be queried regarding sudden unexplained death in children or young adults (i.e., drownings, sudden cardiac death, sudden infant death syndrome, and car accidents), seizures, or familial congenital deafness (Table 17.2). Noting the person or source providing the family history and an estimate of its reliability can be of future use; it may be helpful to request further details from additional family members, particularly if a genetic disorder is suspected. A genetic counselor can be invaluable in helping to sort out the family history.

During the patient examination, orthostatic vital signs (magnitude of decrease in blood pressure relative to change from supine to erect position and heart rate changes) should be obtained. Many patients will manifest a mild (up to a 30 mmHg drop in blood pressure) but asymptomatic orthostatic change with upright positioning. An ECG should be obtained on every patient who experiences syncope, particularly if it is recurrent, occurs with exercise, and is not associated with the characteristic symptoms of NCS. The ECG should be evaluated for heart rate, corrected QT interval (gender-related), T-wave morphologic changes (persistent so-called juvenile T waves in the older adolescent), T-wave alternans, or any ventricular arrhythmia. The ECG should also be evaluated for ventricular preexcitation syndromes, atrioventricular (AV) conduction, or features of Brugada syndrome (see Chaps. 4, 13–15, 18).

For the infrequent patient whose evaluation lacks internal consistency, other studies may be advisable, such as echocardiography to examine for cardiomyopathy, myocarditis, anomalous coronary arteries, pulmonary arterial hypertension, or arrhythmogenic right ventricular dysplasia. A rare patient may warrant cardiac catheterization, including hemodynamic, angiographic, and electrophysiologic evaluation, along with right ventricular endomyocardial biopsy, to exclude potential structural, functional, and arrhythmic abnormalities, particularly before clearance to resume activities.