There are some things in medicine that I feel require a standardized approach for rapid diagnosis & management, especially in the face of an unstable patient & you have a little sweat on your brow. The following are two somewhat straight forward cases that got me thinking …
66 year old self presents to ED following 4 hours of palpitations. She has had no chest pain, dyspnoea or pre-syncope. She has had this before.
HR 170. BP 128 systolic. Speaking full sentences with a clear chest. Sats 98%.
This is her ECG…
84 year old transferred to ED from the dialysis suite with 30mins of palpitations that commenced towards the end of his haemodialysis. He has no chest pain, dyspnoea or pre-syncope. He has had this before.
HR 160. BP 118 systolic. Speaking in phrases but clear chest. He looks grey & slightly clammy.
This is his ECG…
… both are broad, fast & regular leading me to investigate “Ventricular Tachycardia vs SVT with Aberrancy”
There are several suggested criteria to use to help differentiate these two ECG diagnoses including Wellen’s Criteria, the Griffith Approach and of course the Brugada Approach.
Below is a summary of the pertinent points that I found helpful and have subsequently taken to the bedside.
First things first… If the patient is the same colour as your underpants or if they tick the boxes for instability (hypotension, chest pain suggestive of ischaemia, dyspnoea or pulmonary oedema and altered mental state) then head to your defibrillator and shock !!
If the patient is well enough take a closer look…
The following features are suggestive of VT:
- Age > 50 years
- Hx of AMI / CCF / Bypass surgery
- Previous VT.
SVT with aberrancy is suggested (but not confirmed) by:
- Age < 35.
- No prior significant pathology
- Hx of previous SVT.
The presence of Cannon A waves, variation in arterial pulse or a variable 1st heart sound strongly suggest VT.
Examination is not helpful in ruling in SVT with aberrancy.
SVT with aberrancy is possible in the setting of QRS complexes consistent with classic bundle-branch block patterns.
VT has a long list of associated ECG changes that include but are not limited to:
- Fusion beats (a hybrid of a ectopic ventricular beat with a normally conducted QRS)
- AV-dissociation: presence of P-waves (at a different rate to the QRS complexes) & Capture beats (a normal P-QRS sequence).
- QRS > 140 msec.
- Extreme left axis deviation (or North-West axis).
- Presence of either ‘all R-waves’ or ‘all S-waves’ throughout all precordial leads.
- In RBBB pattern (V1): single smooth monophasic R-wave or notched upslope to R-wave (tall left rabbit ear) or a qR complex (small Q-wave, large R-wave)
- In RBBB pattern (V6): QS complex without an R-wave or R/S ratio <1 (small R-wave, deep S-wave).
- In LBBB pattern (V1): Initial R-wave > 30-40 msec or a notching or slurring in the S-wave or an RS interval (onset of R-wave to nadir of S-wave) of > 60-70 msec.
- In LBBB pattern (V6): QS waves or qR pattern (small Q-wave, large R-wave).
Remember: if in doubt, or patient unstable then treat as VT !!
So what happened for our mischievous duo….
Case 1 conclusion:
ECG: Regular broad complex tachycardia. Rate 166bpm. QRS ~120 msec. No P-waves. Left axis deviation. No evidence of AV dissociation. No capture or fusion beats. Typical LBBB pattern. Very likely to be SVT with aberrancy.
Her old notes rapidly arrive & these QRS complexes are identical to previous sinus ECGs.
She receives 6mg IV Adenosine & reverts to sinus rhythm. She is discharged shortly after.
Case 2 conclusion:
ECG: Regular broad complex tachycardia. Rate 150bpm. QRS ~160msec. Extreme (north-west) axis. ?Capture beat (3rd & 9th complex), suggesting AV dissociation. RBBB pattern in V1 with notching (left rabbit ear up) with very small R/S ratio in V6. This is VT.
The issue: profound allergy to Amiodarone !! ( & he ate a hamburger whilst dialysing). ?Lignocaine ?Intubate & defibrillate…
The patient declared himself for us by dropping his BP to 70 systolic.
He receives a small dose of midazolam & receives a 200J synchronized shock.
He reverts temporarily but eventually requires further cardioversion. Following 100mg of IV lignocaine he stays in sinus & is admitted to Coronary Care.
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