Tuesday, December 6, 2011

EKG Myth - Ventricular tachycardia must have concordance

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


Myth: Ventricular Tachycardia must have precordial concordance

When differentiating a regular, wide-complex tachycardia some will look for precordial concordance to rule-in, or more importantly to rule-out ventricular tachycardia.

The absence of precordial concordance is not a reliable method of ruling out ventricular tachycardia:
Although the specificity of concordance for VT is high (>90%), the sensitivity is low (~20%)1.
It is generally thought that positive concordance indicates a posteriobasal left ventricular origin and negative concordance indicates an anterioapical left ventricular origin. However, in the case of positive concordance, SVT with a left-posterior accessory pathway is a known cause.

Until recently, negative concordance has been thought to be "virtually diagnostic" of ventricular tachycardia2. Multiple case reports have shown that certain configurations of accessory pathways can also cause negative concordance3,4,5.

The key takeaway is while this criteria is a useful tool to rule-in ventricular tachycardia (i.e. high specificity), it is not a useful tool to rule-out ventricular tachycardia (i.e. low sensitivity).

Ventricular tachycardia without precordial concordance6.
Ventricular tachycardia without precordial concordance. (c) 2011 EMS 12-Lead Blog.
WPW and Atrial flutter with positive concordance7.
While positive or negative concordance may strongly suggest ventricular tachycardia, providers should not rule-out ventricular tachycardia in its absence.

  1. Pellegrini CN, Scheinman MM. Clinical management of ventricular tachycardia. Curr Probl Cardiol. 2010; 35(9):453-504. [PubMed]
  2. Goldberger ZD, Rho RW, Page RL. Approach to the Diagnosis and Initial Management of the Stable Adult Patient With a Wide Complex Tachycardia. Am J Cardiol. 2008; 101:1456-1466. [Full Text]
  3. Pappas LK, et al. Wide QRS complex supraventricular tachycardia with negative precordial concordance. Am Heart Hosp J. 2009; 7(1):67-8. [PubMed]
  4. Kappos KG, et al. Wide QRS Complex tachycardia with a negative concordance pattern in the precordial leads: Are the ECG criteria always reliable? Pacing Clin Electrophys. 2006; 29:63-6. [PubMed]
  5. Volders PGA, et al. Wide QRS complex tachycardia with negative precordial concordance: Always a ventricular origin? J Cardio Electro. 2003; 14:109-111. [PubMed]
  6. Garmel GM. Wide Complex Tachycardias: Understanding this Complex Condition Part 1 - Epidemiology and Electrophysiology. W J Emerg Med. 2008; 9(1):28-39. [Full Text]
  7. Ibid. 1, Figure 3.

2 comments:

Brandon O said...

Seems like exactly what we need in many cases -- a reliable rule-in criteria. I'm not sure how often VT needs to be "ruled out" per se. If there's gross hemodynamic compromise, zap it. If the patient is doing more or less okay, that's when we'd perhaps ask whether this rhythm is VT (in which case we might be more concerned about deterioration) or another rhythm -- not that this distinction NECESSARILY changes treatment, but it might.

ECG Interpretation said...

GREAT post by Christopher! I'd add to Brandon's comment that the time when we would like to "rule out" VT is precisely when the patient is stable - given that some patients may remain alert and surprisingly "asymptomatic" in VT for hours (if not days = long beyond the EMS time with the patient). Treatment may differ - Verapamil/Cardizem are "No Nos" if there is any likelihood of the rhythm being VT (they vasodilate and facilitate deterioration to VF) - but might be great drugs when you have SVT with aberration not converting with adenosine. Granted - amiodarone & procainamide may work for both VT/SVT - but probably more tendency to cardiovert sooner if you KNOW the rhythm is VT ... AV Dissociation may "rule in" VT (though not usually seen) - but marked axis deviation (not just a little but total RAD or LAD) strongly suggests VT - as do certain specifics of QRS morphology (ie, lack of typical rSR' in V1; very negative QRS in V6; delayed nadir, etc.) - though nothing is truly perfect ...