ECG: Ventricular Tachycardia (VT)

Summary

This video script focuses on the interpretation of ventricular tachycardia (VTAC), specifically wide complex VTAC. It explains the characteristics of VTAC, including rates, absent p-waves, and the importance of recognizing AV dissociation as diagnostic of VTAC. The script also touches on short runs of VTAC, clinical presentations ranging from asymptomatic to hemodynamically unstable, and the need for electrical therapy or ACLS management in severe cases. Key clinical signs and symptoms, such as shortness of breath, chest pain, and syncope, are highlighted for effective patient evaluation and treatment.

Takeaways

• 😀 VT (Ventricular Tachycardia) is a wide complex tachycardia with a heart rate typically between 120-150 bpm, but can occur as low as 100 bpm.
• 😀 Ventricular Flutter is a rapid form of VT with rates greater than 250 bpm.
• 😀 P-waves are absent in VT, but AV dissociation may result in P-waves that are slower than the QRS complex and not related to it.
• 😀 AV dissociation is diagnostic for VT, as P-waves are independent and not associated with the QRS complexes.
• 😀 In 50% of VT cases, both the SA node and a ventricular focus fire at different rates, leading to visible P-waves.
• 😀 In the other 50% of VT cases, only the ventricular focus depolarizes, causing an absence of P-waves.
• 😀 The QRS duration in VT is always wide, typically 0.12 seconds or more.
• 😀 Polymorphic VT involves multiple ectopic foci in the ventricles and includes conditions like Torsades de Pointes (twisting of the points).
• 😀 A short run of VT consists of three consecutive ventricular ectopic beats at a rate of 100 bpm or more.
• 😀 Clinical presentation of VT can vary from asymptomatic to hemodynamically unstable, requiring electrical therapy or even ACLS management.
• 😀 It’s essential to assess the duration and frequency of VT episodes, as well as the associated symptoms like chest pain, syncope, nausea, and shortness of breath.

Q & A

What is ventricular tachycardia (VTac), and what is its typical rate range?

Ventricular tachycardia (VTac) is a type of wide complex tachycardia. The typical rate range for VTac is between 120 and 150 beats per minute (bpm). However, VTac can also be classified as 'slow' when it occurs at rates between 100 and 120 bpm.

What happens if the rate of VTac exceeds 250 bpm?

When the rate of VTac exceeds 250 bpm, it is considered **ventricular flutter**, which is a more severe form of VTac.

Are P-waves present in VTac, and what does their absence indicate?

P-waves are typically absent in VTac. Their absence indicates that the rhythm originates from the ventricles rather than the atria. If P-waves are present and precede the QRS complex, the condition might be a supraventricular tachycardia with aberrancy rather than VTac.

What does it mean if you see P-waves that are equidistant and slower than the ventricular rate in VTac?

If you observe P-waves that are equidistant and firing at a slower rate than the ventricular rate, it indicates **AV dissociation**, which is **diagnostic of VTac**. This suggests that the atria and ventricles are functioning independently.

How does AV dissociation occur in VTac?

AV dissociation occurs when the **SA node** fires at a rate (e.g., 80 bpm) while a focus in the ventricles fires at a faster rate (e.g., 180 bpm), leading to independent contraction of the atria and ventricles, which is seen as equidistant P-waves that do not correspond with the QRS complexes.

What is the typical duration of a QRS complex in VTac?

The QRS complex in VTac is always wide, typically greater than 0.12 seconds, often around 0.14 seconds or more. This is one of the defining features of VTac on an ECG.

What is polymorphic VT, and how does it differ from regular VTac?

Polymorphic VT is a form of VTac where multiple ectopic foci in the ventricles cause a varying QRS morphology. An example of polymorphic VT is **Torsades de Pointes**, which involves a twisting of the QRS complexes.

What defines a short run of VTac?

A short run of VTac is defined as the occurrence of **three ventricular ectopic beats in a row** at a rate of **100 bpm or greater**.

How can patients with VTac present clinically?

Patients with VTac can present in various ways. Some may be asymptomatic and stable, while others may experience symptoms like shortness of breath, chest pain, or hemodynamic instability. In severe cases, they may present with full cardiac arrest, requiring ACLS management.

What clinical factors should be considered when assessing a patient with VTac?

When assessing a patient with VTac, it is important to consider the **duration and frequency of the episodes**, as well as the **patient’s symptoms**, such as syncope, chest discomfort, nausea, and shortness of breath. These factors help determine the severity of the condition and guide treatment decisions.