45yo Buddhist monk with no past medical history presents to the parkland ED with 1 week mild chest pain on exertion and palpitations. Initial ECG is shown below.
answer: RVOT ventricular tachycardia
Looking at the ECG a regular wide complex tachycardia (WCT) can be seen, a safe bet when seeing this pattern is to assume VT until proven otherwise. Fortunately he was sitting up talking in bed with a BP of 140/85 and in NAD, after putting pads on a little more history and ECG interpretation could be done.
The main differential for WCT is VT, SVT w/ abberancy, and antidromic AVRT (aka WPW). A nice review of the differential can be found here. http://en.ecgpedia.org/index.php?title=File:VT_algorithm_en.svg
Differentiation between these entities can be difficult, several criteria have been established to help including Brugada and Vereckei. A review is found here https://lifeinthefastlane.com/ecg-library/basics/vt_vs_svt/ with the main points of differentiation below.
Returning to our ECG one can see several of these features including AV dissocation and fusion beats, later EKGs also revealed capture beats. Highlights of AV dissociation (shorter red circles), fusion beat (tall red circle) and in second ECG capture beats are shown below.
Importantly this ECG displays a LBBB pattern with an inferior access insinuating that the focus of VT is coming from the right side of the heart and moving inferiorly therefore starting superiorly establishing the diagnosis of RVOT VT. Here is a brief review of RVOT VT https://lifeinthefastlane.com/ecg-library/rvo/ . cMRI can help differentiate arrhythmogenic right ventricular dysplasia vs idiopathic VT from RVOT source.
We used low dose beta blockers in our patient to suppress his VT with good results and proceeded to EP study with ablation in a non-emergent setting. We avoided using amio or procainamide as these can suppress the VT focus and make ablation much more difficult (half life of metop vs these agents allowed for use of metop over the weekend and holding on morning of ablation). He was discharged in excellent condition and will have cMRI as outpatient to further clarify RV dysplasia.
Important learning points
- VT can be difficult to differentiate from SVT w/ abberancy
- if stable you have time to contemplate the differential
- call EP before loading with anti-arrhythmics (if stable) as this will affect ablation plans
- use your ECG axis to determine where a rhythm is originating