EXTRA COPY — ECG Blog #533: A Wide Tachycardia — EXTRA COPY

The ECG in Figure-1 was obtained from a previously healthy 60-something year old patient — who sought medical care for the abrupt onset of tachycardia. The patient was hemdynamically stable at the time this ECG was recorded.

QUESTIONS:

• How would you interpret the ECG in Figure-1?
• What would you do? 

Figure-1: The initial ECG in today's case — obtained from 60-something year old patient (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts:

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Hi Arman. Regular WCT (Wide-Complex Tachycardia) at ~170/minute without sinus P waves.

• PINK arrows look like 1:1 VA conduction.
• QRS morphology is perfectly consistent with LBBB conduction (upright R waves in I,aVL,V6 — and very steep initial downslope in the anterior leads).
• So clearly could be a reentry SVT rhythm. If completely stable and presented to an ED — Could try Adenosine as a diagnostic/therapeutic trail (should cardiovert the patient if this is AVNRT or AVRT). For any concerns, or if at any time the patient became unstable — then cardiovert.
• Note: 1:1 VA conduction can occur with both reentry SVTs as well as with VT — so this finding does not help in diagnosis.
• Cannot rule out VT on this single ECG — but morphology suggests SVT more likely.

Figure-2: XXXX

 

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Acknowledgment: My appreciation to @PrecordialSwirl for submission of today's case with these tracings.

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MY REPLY: 

Hi Arman. Regular WCT (Wide-Complex Tachycardia) at ~170/minute without sinus P waves.

• PINK arrows look like 1:1 VA conduction.
• QRS morphology is perfectly consistent with LBBB conduction (upright R waves in I,aVL,V6 — and very steep initial downslope in the anterior leads).
• So clearly could be a reentry SVT rhythm. If completely stable and presented to an ED — Could try Adenosine as a diagnostic/therapeutic trail (should cardiovert the patient if this is AVNRT or AVRT). For any concerns, or if at any time the patient became unstable — then cardiovert.
• Note: 1:1 VA conduction can occur with both reentry SVTs as well as with VT — so this finding does not help in diagnosis.
• Cannot rule out VT on this single ECG — but morphology suggests SVT more likely.

 

Arman — I’d LOVE to use this case as an ECG Blog! (Readers always love the WCT cases!  — especially when you will be giving me follow-up and EP input! )

• I’d be happy to acknowledge you and/or any of your colleagues (Please tell me the city and country where you are from — OR, the case could be anonymous if you prefer). It may be a little while — as I have other cases to go before this one.
• P.S. — I’m curious — What is your medical specialty? — :)

ARMAN REPLY:

More background- the pt had an SVT ablation 5 years ago but developed palpitations again. Was evaluated outpatient and admitted for an elective ablation. Baseline ECG had no aberrancy. He developed this tachycardia in our ward, a day before his scheduled ablation. Good thing about a telemetry unit is that we could go back in time and see that it initiated with a PAC( I curse myself for not saving that strip). The tachycardia was terminated with 6 of adenosine.

EP results- concealed left lateral accessory pathway with no inducible tachycardia. Slow- Fast AVNRT induced and ablated. Rate related LBBB. 

Could this have been orthodromic AVRT? I dont think so, as I said, it initiated with a PAC.

However, I still don’t understand why LBB was refractory instead of the RBB, it’s usually the other way around.