In this article, we will discuss the Diagnosis of Acute Syncope/Faint. So, let’s get started.
Investigations
Blood levels: Measurements of electrolytes, hematocrit, glucose is indicated. Toxicological screens for alcohol and drugs if suspected. Hormonal levels if endocrine disorders is the cause.
Resting ECG and stress testing: Resting ECG may be helpful in diagnosis of arrhythmias or coronary artery disease. However, a normal ECG does not rule out these as a cause of syncope. ECG done during carotid sinus massage indicates positive response (vasodepressor syncope) if a sinus pause of 3 seconds or more is produced. Echocardiography should be performed in patients with history of heart disease or evidence on physical examination. Exercise testing can be done when symptoms are associated with exertion or stress.
Holter monitoring: Ambulatory ECG (Holter ECG) is mainly useful to correlate the symptoms with arrhythmias recorded on Holter ECG which could not be recorded on resting or serial ECGs. Continuous loop event recorders can be used for long-term monitoring for weeks to months. These are activated by the patient at the time of symptoms, freezing in its memory for analysis. In particularly difficult cases, tiny implantable ECG recorders may be used.
Signal average ECG: It is helpful in detecting the late potentials for predicting inducible sustained VT.
Electrophysiological studies: In cases with recurrent syncope of unknown etiology where Holter monitoring is non-contributory and there is underlying heart disease particularly ischemia or prior MI, the detailed electrophysiological studies like sinus node recovery time (for sick sinus syndrome). His bundle electrocardiography for conduction delays and inducible VT by prolonged stimulation may be helpful.
Electrophysiological clues to syncope
SNRT (sinus node recovery time) >3 seconds or more
Pacing induced infra nodal block
HV interval >100 msec on His bundle ECG
Paroxysmal SVT with symptoms
EEG and CT scan not helpful, except in differentiating syncope from epilepsy
Psychiatric evaluation for anxiety disorders, may reveal hyperventilation and syncope.