Thursday, November 17, 2011

EKG Myth - "It's Too Fast for Ventricular Tachycardia"

This is part of a series of posts detailing common electrocardiogram myths.


Myth: Rate can help you rule out Ventricular Tachycardia

When differentiating a regular, wide-complex tachycardia some will look at the rate to rule out ventricular tachycardia. Studies have not found rate to be a predictive finding1.
...regarding ventricular rate, significant overlap unfortunately exists between VT and SVT such that rate is not a helpful criterion to differentiate origins2.
Ventricular tachycardia technically can range in rates from 100 bpm through 300 bpm. However, a practical definition of VT would place the lower bound around 120 bpm and the upper bound around 260 bpm3.

Common terminology includes rates slower than 120 as "Slow Ventricular Tachycardia", which most often is not true VT4. Rates upwards of 260 to 300 bpm are commonly termed "Ventricular Flutter"5.

Ventricular tachycardia at 130 bpm. (c) 2001 - 2011 Beth Israel Deaconess Medical Center.

Ventricular tachycardia at 206 bpm. (c) 2011 EMS 12-Lead Blog.

Ventricular tachycardia at 280 bpm. (c) 1994-2011 WebMD.

As a rule: a regular, wide-complex tachycardia should be treated as ventricular tachycardia in the field, until proven otherwise.

  1. Griffith MJ, et al. Multivariate analysis to simplify the differential diagnosis of broad complex tachycardia. Br Heart J (1991); 66:166-74. [PubMed]
  2. Hudson KB, et al. Electrocardiographic Manifestations: Ventricular Tachycardia. J Emerg Med (2003); 25:303-314. [PubMed]
  3. Surawicz B, Knilans TK. Chou's Electrocardiography in Clinical Practice: Adult and Pediatric, 6th ed. Philadelphia, PA. Saunders, 2008. 
  4. Mattu A. ECG PEARLS: Beware the Slow Mimics of Ventricular Tachycardia. Emergency Physicians Monthly, 24 August 2010. Retrieved Online 8 November 2011. [Free Full Text]
  5. Gurevitz O, et al. Long-term prognosis of inducible ventricular flutter: not an innocent finding. Am Heart J (2004); 147(4):649-54. [PubMed]

3 comments:

Mike said...

Beware of "Slow V-Tach" because it often isn't! Here is an article by Amal Mattu that outlines some things to consider before jumping on the V-Tach pathway.

http://www.epmonthly.com/clinical-skills/ekg/ecg-pearls-beware-the-slow-mimics-of-ventricular-tachycardia/

Christopher said...

Great point Mike, I probably should have mentioned that the differentials for "Slow Ventricular Tachycardia" includes more than SVT with Aberrancy and most likely should not treated as VT!

mb said...

Chris,
You know from attending my class the perils of using rate alone to determine the tachycardia. Morphological clues in specific leads, particularly aVR, are the best indicators, and they are accurate irrespective of rate. Excellent topic.