ECG Blog #436 — Bigeminy or Alternans?

The ECG in Figure-1 — was obtained from an older man with known coronary disease. He was on a number of medications — including antiplatelet agents, a statin drug and Digoxin.

• The patient presented to the ED (Emergency Department) for an episode of syncope. He developed cardiac arrest shortly after the ECG in Figure-1 was recorded.

QUESTIONS:

• How would YOU interpret the ECG in Figure-1?
•   What is the most likely cause of this arrhythmia?

Figure-1: The initial ECG in today's case. (To improve visualization — I've digitized the original ECG using PMcardio). 

MY Thoughts on the ECG in Figure-1:

A repetitive bigeminal pattern is seen in Figure-1 — in which QRS morphology alternates with each beat. 

• There are 2 different QRS morphologies — both of which clearly manifest a wide QRS complex when this rhythm is viewed in certain leads. Thus, although one of these QRS morphologies looks narrow in lead V3 — a glance at leads III, aVR, aVL, V1 and V2 confirms that the QRS is wide!
• NOTE: Although QRS morphology from one-beat-to-the-next looks similar in certain leads (ie, in leads aVR, V4,V5,V6) — there can be no doubt about the presence of 2 distinct QRS morphologies when one looks at leads I, III, aVL, aVF — and leads V1,V2,V3.
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• The overall rate of the rhythm in Figure-1 is fast (at least 150/minute).
• There are no P waves.
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• And, the patient is older (ie, prone to reduced renal function) — and he is taking Digoxin.

IMPRESSION: Given the presence of a wide tachycardia — with 2 distinct QRS morphologies, and no sign of P waves — a presumed diagnosis of BiDirectional Ventricular Tachycardia has to be made.

• As discussed in ECG Blog #231 — Bidirectional VT is a special form of VT, in which there is beat-to-beat alternation of the QRS axis. This unique and very uncommon form of VT is distinguished from PMVT (PolyMorphic VT) and from pleomorphic VT — because a consistent pattern (ie, alternating long-short cycles) is usually seen throughout the VT episode. As implied in its name, there are 2 QRS morphologies in bidirectional VT — and they alternate every-other-beat (CLICK HERE — for this case report Review by Femenia et al on Bidirectional VT in a patient with CPVT = Catecholaminergic Polymorphic VT).
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• KEY Point: There are a limited number of causes of Bidirectional VT — with the 2 most common causes being Digoxin toxicity and CPVT. Given that today's patient was taking Digoxin — Digoxin Toxicity was immediately suspected as the most likely cause. 
• Since Digoxin is primarily renally excreted — older age, that is commonly associated with reduced renal function, would predispose to developing Digoxin toxicity.

As reviewed by Almarzuqi et al (Vasc Health Risk Mgmt 18:397-406, 2022) — Potential Causes of Bidirectional VT include:

• Digitalis toxicity.
• CPVT (Catecholaminergic PolyMorphic VT).
• Acute myocardial ischemia.
• Familial hypokalemic periodic paralysis.
• Cardiac Sarcoidosis.
• Primary Cardiac Tumors and/or Cardiac Metastasis.
• Andersen-Tawil Syndrome ( = Long QT Syndrome, Type 7).
• Acute Myocarditis.
• Certain drug overdoses (Aconitine poisoning, severe caffeine poisoning).

To Emphasize: Bidirectional VT is rare. That said, it does occur — and awareness of the entities associated with this diagnosis may be important in evaluation and treatment.

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CASE Conclusion:

As noted above — today's patient developed cardiac arrest shortly after arrival in the ED. Despite prolonged resuscitation with multiple defibrillation attempts — the patient could not be saved.

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Acknowledgment: My appreciation to Hafiz Abdul Mannan Shahid (from Lahore, Pakistan) for the case and these tracings.

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Related ECG Blog Posts to Today’s Case: 

• ECG Blog #36 — Reviews irregular wide tachycardias (with distinction between Torsades de Pointes vs Polymorphic VT discussed in Figure-3 in this post). 
• See My Comment in the June 1, 2020 post in Dr. Smith's ECG Blog — for review of Pleomorphic VT.
• ECG Blog #231 — for review on the types of VT (including monomorphic — polymorphic — pleomorphic — and bidirectional VT).
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• Bidirectional VT: Challenges and Solutions (Almarzuqi et al — Vasc Health Risk Mgmt 18:3997-406, 2022). 
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• Pleomorphic VT and Sudden Cardiac Death — Editorial by Liu and Josephson on potential mechanisms to explain the ECG appearance of Pleomorphic VT. 
• Case Report on BiDirectional VT — by Femenia et al on this patient with BiDirectional VT from CPVT (Catecholaminergic Polymorphic VT).
• ECG Blog #197 — Reviews the concept of Idiopathic VT (including recognition and treatment of Fascicular VT and RVOT VT).
• Multifocal vs Polymorphic VT — September 23, 2011 post from Dr. S. Venkatesan's insightful and user-friendly Cardiology Blog (from which I adapted his figures to derive my Figure-3).