eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiology
Syncope: Differential Diagnoses & Workup
Updated: Nov 11, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Differential Diagnoses
Workup
Laboratory Studies
- If the physical examination findings are normal, an ECG is the only additional laboratory test required. Other laboratory tests are performed based on suspicious findings in both history and physical examination.
- Hypoglycemia, hypothyroidism, and anemia can cause syncope. Diabetes mellitus and Addison disease (primary adrenal insufficiency) may cause syncope through volume depletion. If any of these entities are suspected, appropriate laboratory workup should be performed.
Imaging Studies
- Echocardiography is indicated only in patients with abnormal ECG findings, abnormal physical examination findings, or other features suggestive of structural heart disease.
- Specific features to assess include coronary anatomy, right and left ventricular size and function, free wall and septal thickness, left ventricular outflow tract obstruction, presence of cardiac tumors, and pulmonary artery pressure.
Other Tests
- Electrocardiography: ECG is indicated in the assessment of syncope in children.
- Holter monitoring: This is indicated in pediatric patients with recurrent syncope, although the yield of true pathology is probably about 10%. Studies in adults suggest that a 48-hour period of monitoring is superior to a 24-hour period.
- Transtelephonic ECG: Event monitoring is useful for patients who have infrequent symptoms and when Holter monitoring has not been helpful in confirming a diagnosis. Event monitors can be applied only after the onset of symptoms and are not particularly useful, except perhaps in young children when the device is applied by the accompanying parent or caregiver. Even then, the cause of syncope may not be determined because the initiating cardiac rhythm is likely to have been missed.
- Loop recording: Continuously applied event monitors capture the cardiac rhythm into memory. They are particularly useful if symptoms occur 1-2 weeks preceding the event. After that period, compliance with wearing the device often decreases.
- Implantable loop recorder: Small implantable loop recorders may be subcutaneously applied in the anterior chest of children who have recurrent syncope that remains undiagnosed despite full evaluations. They are particularly useful to help unmask arrhythmias as a cause of unexplained syncope in children.11 The device continuously records a surface ECG. Using a patient activator at the time of event, retrospective electrocardiographic data can be stored into the device memory for a programmable number of minutes. This electrocardiographic recording can then be retrieved using a pacemaker programmer to interrogate the device.
- Exercise testing: The specific indications for and utility of exercise testing in pediatric syncope are not identified. Certainly, patients with events that appear to be related to stress or exercise should undergo an exercise evaluation if the patient is capable.
- Tilt table testing: Tilt table testing is a useful procedure for patients with undiagnosed syncope if the diagnosis has not yet been made based on a typical history and compatible physical findings. These tests are beginning to approach a standardized methodology. Typically, the patient is immobilized on a tilting bed, which is then brought to a 70° upright position for approximately 30 minutes while heart rate (ECG) and blood pressure are monitored. Following this, the patient may undergo a further tilt protocol while challenged with isoproterenol. Isoproterenol challenge decreases the rate of false-negative results but increases the rate of false-positive results of tilt table testing.
Procedures
- An electrophysiology study should be performed in patients with aborted sudden death if the diagnosis remains unclear. It may be considered in patients who have recurrent syncope not diagnosed based on noninvasive means.
- The protocol should include His bundle electrocardiography and atrial and ventricular protocols with up to 3 extrastimuli programmed down to refractoriness, including 2 drive train cycle lengths and 2 ventricular sites, with and without isoproterenol challenge.
- Ancillary catheter laboratory investigations including hemodynamic assessment, ventricular angiography, aortic angiography, coronary angiography, and endomyocardial biopsy should be considered and scheduled as indicated, along with the electrophysiologic procedure.
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 Differential Diagnoses & Workup: Syncope |
| Treatment & Medication: Syncope |
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Further Reading
Keywords
syncope, faint, common faint, loss of consciousness, vasovagal syncope, vasodepressor syncope, neuroregulatory syncope, neurogenic syncope, neurocardiogenic syncope, presyncope, atrial fibrillation, supraventricular tachycardia, SVT, pulmonary hypertension
