Dr. M. S. Alam, MD, MBBS, CCFP, FCFP, Clinical Lecturer, Cumming School of Medicine, Calgary, University of Calgary, Family Medicine Department, Calgary, AB.

Abstract
Syncope is generally categorized by such known causes as vasovagal syncope, situational syncope, postural syncope, neurologic syncope, postural-orthostatic tachycardia syndrome, and unknown causes. The unknown causes of syncope can be challenging to diagnose and treat since possible causes can range from benign to life-threatening. This article will focus on unknown cases with no evident cause.
Key Words: syncope, unknown causes, diagnosis, treatment.

Syncope with unknown origin is challenging to treat in both family medicine and urgent and emergent care environments. Syncope accounts for 1%¹ of visits to urgent and emergency centres, and nearly 1%² of visits to family medicine practices in Canada. 30-40%³ of syncope-related cases result in hospital admission, causing undue economic burden to an already overtaxed healthcare system.

Generally, syncope is categorized by known or unknown causes. Cases in which causes are known include: vasovagal syncope (sudden drop in blood pressure); situational syncope (a result of pain, fear, hunger, dehydration, for example); postural syncope (sudden drop in blood pressure caused by a change in body position); neurologic syncope (associated with seizure, stroke, or transient ischemic attack); postural-orthostatic tachycardia syndrome (tachycardia that results from standing after sitting or lying in a prone position). In many instances, some or all of these causes must be eliminated before syncope is determined to be of unknown origin; this article will focus on cases with no evident cause.

One of the challenges associated with diagnosing and treating syncope is the plethora of possible causes that range from benign to life-threatening. Many patients who present with syncope present themselves to the emergency departments seeking treatment; however, several patients may seek assistance from their family physician. There are some decision rules and guidelines to help first responders categorize and triage syncope cases, but none of them is superior to the acumen of an experienced practitioner. Various risk stratification tools are available to highlight critical assessments and aid in selecting the proper diagnostic test.