VT vs SVT with aberrancy
Today's article is about VT vs SVT with aberrancy.
The precise electrocardiographic diagnosis of broad complex tachycardia is crucial for both immediate treatment during acute presentation and long-term management, as well as for prognostication. While individual algorithms are not flawless and may risk oversimplifying the clinical condition, it remains essential for every physician to have an initial strategy when confronted with a case of broad complex tachycardia.
Before continuing, it is necessary to refresh some basic concepts.
Supraventricular tachycardia (SVT) refers to any tachyarrhythmia (>100 bpm) arising at or from above the atrioventricular (AV) node.
Aberrant conduction is defined as supraventricular impulse with abnormal conduction through the atrioventricular node resulting resulting in a broader QRS complex. Aberrant conduction usually manifests either as left or right bundle branch block pattern.
Right bundle branch block (RBBB) aberrant conduction is the more common form of aberrancy than LBBB aberrant conduction because of the longer refractory period of the right bundle and is rate dependent.
The aim of this article is to provide basic clues on how to apply some of the most used criteria that might be helpful in diagnosing VT (ventricular tachycardia).
Note that the following features are suggestive of VT, but their absence does not necessary exclude VT. Also note that pre-existing LBBB or RBBB is exclude from this discussion.
History
In 1960 Dr. Alfred Pick and Dr. Richard Langendorf published, “Differentiation of supraventricular and ventricular tachycardia.” Sixty years later, differential diagnosis of wide QRS tachycardia on the electrocardiogram remains a challenging exercise.
Article: https://www.sciencedirect.com/science/article/abs/pii/S0033062060800011?via%3Dihub
In the past 40 years, several algorithms or criteria have been developed to differentiate VT from SVT. Here I show you some of them:
Article: https://pubmed.ncbi.nlm.nih.gov/3376886/
Article: https://www.heartrhythmjournal.com/article/S1547-5271(19)30854-9/abstract
Article: https://www.ahajournals.org/doi/abs/10.1161/01.CIR.83.5.1649
Article: https://www.heartrhythmjournal.com/article/S1547-5271(10)00216-X/abstract
Other criteria include: Vereckei 2007, Griffith 1994.
After having analyzed some criteria, let's review some electrocardiographic characteristics that suggest VT:
- AV dissociation
- Capture beats
- Fusion beats
- Precordial concordance
AV dissociation: Although the presence of AV dissociation is highly suggestive of VT, its absence does not exclude VT. A single dissociated P wave at the onset of WQRST could be a reflection of AV dissociation and thus suggestive of VT.
Precordial Concordance
During precordial concordance, there is no R/S transition and is suggestive of VT (PPV 90%–100%, sensitivity 88% [Miller JM. et al 2006]). Although precordial concordance is highly suggestive of VT, its absence does not exclude the diagnosis.
- Positive concordance (A): All the QRS complexes from V1 to V6 have positive polarity.
- Negative concordance (B): All the QRS complexes from V1 to V6 have negative polarity.
I think it's time to apply what we've learned.
- What criteria are present in the following EKG?
- This is VT?
- SVT with aberrancy?
Let's talk about "VT Mimics"
It is important to clarify that on many occasions we will face EKGs that may look like VT but are not, and are the so-called "VT Mimics". Let's look at some examples.
Flecainide overdose. Courtesy of Dr. Sergio Pinski
Severe hyperkalemia. Courtesy of Dr. Stephen W. Smith
Here is a sample of "Wide QRS Mimic" due to severe ST elevation in the setting of pLAD occlusion. Courtesy of Dr. Joshua Cooper.
Despite the presence of a wide variety of algorithms for differentiating broad complex tachycardia, the ability to make a rapid and accurate diagnosis of the condition remains a clinical challenge.
WELL, that's it for today's article. I hope it has been useful to you. If you have a friend or colleague who has asked you about this topic, send them this article. See you at the next one.
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