MDCalc Wars: Sorting Out Syncope – Which Rule Should You Trust?

Written by Eric Steinberg DO, MEHP
REBEL EM
Medical Category: Cardiovascular
Canadian Syncope Risk Score, Clinical Decision Rules, MDCalc, MDCalc Wars, San Francisco Syncope Rule, Syncope, Syncope Risk Tools

August 25, 2025

🗝️ Key Points

- ⚡ SFSR: Quick and simple to use, but poor external validation and inconsistent performance limit its reliability.
- 🧩 CSRS: Comprehensive and well-validated, providing stronger risk stratification for syncope patients.
- ⚖️ Trade-off: SFSR = speed and simplicity; CSRS = accuracy with more complexity and some subjectivity.
- 🩺 Bottom Line: Use decision rules as guides, not replacements, for clinical judgment.

🤕 Case

A 46-year-old male with hypertension and a fondness for double espressos and triple IPAs faints during his niece’s graduation in a sweltering gym. He has a quick recovery, is drenched in sweat, and no seizure activity was witnessed. Was it the beverages and boring speeches—or something more concerning?

🔨 Why Do We Need a Clinical Decision Rule?

Syncope is one of the most common complaints we face in the ED. Most patients do well, yet a small subset are harboring serious cardiac or neurologic disease. Admit everyone, and we waste beds and resources; discharge everyone, and we risk missing life-threatening disease. As always in emergency medicine, we’re searching for the needle in the haystack—the one patient out of hundreds who’s truly at risk.

You may have heard of the San Francisco Syncope Rule, but have you met its worthy opponent, the Canadian Syncope Risk Score? When syncope isn’t straightforward, which tool should you trust to guide disposition? Could these decision aids reveal risks you might otherwise miss?

🎯 Quick Hits

💬 Case Resolution

In the ED, his BP was 190/110, and his ECG showed nonspecific ST-T changes compared to his previous one. Labs were within normal limits. On MDCalc, the San Francisco Syncope Rule flagged him as not low-risk, and the Canadian Syncope Risk Score and your clinical gestalt pushed him into the intermediate category. Instead of discharge papers, he earned a telemetry observation stay—because sometimes it’s not just the “boring speeches!”

🚨 Clinical Bottom Line

The San Francisco Syncope Rule is quick and easy to apply, but its inconsistent performance and poor external validation limit its reliability as a stand-alone tool. In contrast, the Canadian Syncope Risk Score is more comprehensive and has been more robustly validated, offering stronger risk stratification. However, it comes with added complexity and a degree of subjectivity, reminding us that no decision tool replaces sound clinical judgment.

Post Peer Reviewed By: Marco Propersi, DO (Twitter/X: @Marco_Propersi), and Mark Ramzy, DO (X: @MRamzyDO)

🧭 Cheat Sheets

MDCalc Wars: Canadian Syncope Risk Score Prep Sheet

MDCalc Wars: San Francisco Syncope Rules Prep sheet

👤 Author

Eric Steinberg

DO, MEHP

Content Director, MDCalc, Residency Director, Emergency Medicine St. Joseph's University Medical Center, Paterson, NJ

Meet The Team

🔎 Your Deep-Dive Starts Here

Cite this article as: Eric Steinberg DO, MEHP, "MDCalc Wars: Sorting Out Syncope – Which Rule Should You Trust?", REBEL EM blog, August 25, 2025. Available at: https://rebelem.com/mdcalc-wars-sorting-out-syncope-which-rule-should-you-trust/.