Advanced EKGs - Distinguishing VT from SVT with aberrancy

Summary

This video discusses how to differentiate between ventricular tachycardia (VT) and supraventricular tachycardia with aberrancy (SVT with aberrancy). The video explains key EKG features for identifying VT, such as AV dissociation, capture and fusion beats, long QRS duration, and various morphology criteria. It also covers algorithms like Brugada and Basel to aid in diagnosis. Additionally, it highlights the importance of clinical features, such as age, history of ischemic heart disease, and other conditions, to distinguish between VT and SVT with aberrancy, emphasizing the need for accurate diagnosis due to the differing treatments and urgency.

Takeaways

• 😀 Differentiating between VT and SVT with aberrancy is crucial as they require different treatments and have varying urgency levels.
• 😀 SVT refers to any tachycardia originating above the ventricles, while aberrancy refers to causes of wide QRS complexes unrelated to ventricular rhythm, like bundle branch blocks or electrolyte disorders.
• 😀 AV dissociation, where the atria and ventricles beat independently, is highly suggestive of VT and can be seen on an ECG as out-of-phase P waves and QRS complexes.
• 😀 Capture and fusion beats, which are narrow or hybrid QRS complexes within a wide complex tachycardia, may indicate VT but can also be seen in SVT with a pre-existing bundle branch block.
• 😀 A QRS duration over 160 ms and concordance in precordial leads (all leads V1–V6 either upright or downgoing) are key signs suggestive of VT.
• 😀 An extreme QRS axis between 180° and 270°, along with 'rabbit ears' in V1, can point toward VT rather than SVT with aberrancy.
• 😀 Bugatta sign (a prolonged R to S duration) and Josephson sign (notching on the S wave) are indicative of VT.
• 😀 The Brugada criteria, which incorporate AV dissociation, concordance, bugatta sign, and specific QRS morphology, are commonly referenced to identify VT, though they are not widely used in practice.
• 😀 Newer algorithms like the Basel algorithm are emerging to provide faster and more accurate identification of VT, with sensitivity and specificity values as high as 93% and 90%, respectively.
• 😀 Clinical features such as age over 35, a history of ischemic heart disease or MI, and a family history of sudden cardiac death increase the likelihood of VT over SVT with aberrancy.

Q & A

What is the importance of distinguishing between VT and SVT with aberrancy?

Distinguishing between VT (ventricular tachycardia) and SVT with aberrancy is crucial because they require different treatments both acutely and long term, and they carry different degrees of urgency.

What does the term 'SVT with aberrancy' mean in this context?

SVT refers to any supraventricular tachycardia originating above the ventricles, including sinus tachycardia. Aberrancy refers to a wide QRS complex caused by factors like bundle branch blocks, accessory pathways, or medication effects.

What is AV dissociation and how does it relate to VT?

AV dissociation occurs when the atria and ventricles beat independently, with P waves and QRS complexes occurring at different rates. This is highly suggestive of VT, as it often indicates that the rhythm is originating from the ventricles.

What are capture and fusion beats, and how are they useful in diagnosing VT?

Capture beats are narrow, normal-looking beats that occur during a run of wide complex tachycardia. Fusion beats are a hybrid of supraventricular and ventricular impulses. Both are particularly suggestive of VT but can occasionally occur in SVT with aberrancy.

What does a QRS duration greater than 160 milliseconds suggest?

A QRS duration over 160 milliseconds is typically seen in VT, as this indicates a prolonged depolarization time due to the rhythm originating from the ventricles.

What is the significance of 'concordance' in the precordial leads?

Concordance refers to the situation where all QRS complexes in the precordial leads (V1-V6) are either entirely upright or entirely downgoing. This pattern, along with a prolonged QRS, can be highly suggestive of VT.

How does the presence of a 'rabbit ear' pattern in V1 suggest VT?

A taller left 'rabbit ear' in V1, which is a notch or shoulder on the right side of the R wave, suggests VT. This is distinct from a typical right bundle branch block, where the right rabbit ear is taller.

What is Bugatta's sign, and how does it relate to VT diagnosis?

Bugatta's sign refers to a QRS duration from the onset of the QRS complex to the nadir of the S wave (R to S duration) greater than 100 milliseconds. It is a feature suggestive of VT.

What is the Basel algorithm, and how does it compare to the Brugada criteria?

The Basel algorithm is a new approach for diagnosing VT that combines high sensitivity and specificity, using clinical features like a history of MI and a timed first peak in leads II and AVR. It has been shown to be faster and more accurate than the Brugada criteria.

How do clinical features contribute to the diagnosis of VT over SVT?

Clinical features such as age over 35, a history of ischemic heart disease, prior MI, left ventricular hypertrophy, cardiomyopathy, or a family history of sudden cardiac death increase the likelihood that a wide complex tachycardia is VT.