Understanding Supraventricular Tachycardia (SVT)

Summary

This video from Zero to Finals explains supraventricular tachycardia (SVT), a condition where abnormal electrical signals above the ventricles cause a fast heart rate. The pathophysiology is described, along with different types of SVT, such as atrioventricular nodal reentrant tachycardia and Wolf-Parkinson-White syndrome. It covers how to identify SVT on an ECG, manage stable and unstable patients, and treat recurrent cases through medications or radiofrequency ablation. The video emphasizes that the content is for exam preparation, not clinical practice, and encourages consulting guidelines and seniors for patient care.

Takeaways

• ⚡ Supraventricular tachycardia (SVT) is a rapid heart rate caused by abnormal electrical signals originating from above the ventricles, typically in the atria.
• 🔄 SVT often occurs due to an electrical re-entry loop, where signals re-enter the atria from the ventricles, causing continuous heart contractions.
• ⏳ Paroxysmal SVT refers to recurrent episodes of SVT that come and go, with periods of normal heart rhythm in between.
• 📉 SVT typically presents as a narrow complex tachycardia on an ECG, with a QRS complex duration of less than 0.12 seconds.
• 🔬 Differentiating between sinus tachycardia, atrial fibrillation, atrial flutter, and SVT is crucial for accurate diagnosis and treatment.
• 💉 Initial management of stable SVT includes non-invasive methods like the Valsalva maneuver and carotid sinus massage, followed by adenosine if necessary.
• 💊 Adenosine is a common drug used to reset the heart’s rhythm in SVT but should be avoided in patients with asthma, COPD, or heart conditions.
• ⚡ Synchronized cardioversion is used in unstable SVT patients, delivering electrical shocks to restore normal rhythm in a controlled manner.
• 🧠 Long-term management of paroxysmal SVT may involve medications (beta blockers, calcium channel blockers, or amiodarone) or catheter ablation for more permanent solutions.
• 🩺 Radiofrequency ablation targets abnormal electrical pathways in the heart, potentially curing certain arrhythmias like SVT, WPW syndrome, and atrial flutter.

Q & A

What is supraventricular tachycardia (SVT)?

Supraventricular tachycardia (SVT) refers to a fast heart rate caused by abnormal electrical signals originating from above the ventricles, typically in the atria.

How does the normal electrical conduction in the heart occur?

In normal conditions, the electrical signals in the heart start in the sinoatrial node, causing atrial contraction. The signals then travel through the atrioventricular (AV) node to the ventricles, resulting in ventricular contraction.

What causes SVT, and how does it affect the heart's electrical activity?

SVT is typically caused by the re-entry of electrical signals from the ventricles back into the atria. This forms a continuous loop, leading to a fast, narrow complex tachycardia.

What are the four main differentials for a narrow complex tachycardia?

The four main differentials are sinus tachycardia, SVT, atrial fibrillation, and atrial flutter. Each has distinguishing features on an ECG.

What distinguishes sinus tachycardia from SVT on an ECG?

Sinus tachycardia shows a normal P wave, QRS, and T wave pattern, whereas SVT causes regular QRS complexes without the classic P wave pattern and results from abnormal electrical re-entry.

What is the difference between atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT)?

AVNRT is when the re-entry occurs through the AV node, while AVRT involves an accessory electrical pathway outside the AV node that allows signals to pass between the atria and ventricles.

What is Wolff-Parkinson-White (WPW) syndrome, and how is it related to SVT?

WPW syndrome is a condition where an accessory electrical pathway exists in the heart, which can cause episodes of SVT. It is characterized by a delta wave on an ECG and a short PR interval.

What is the recommended first-line treatment for stable patients with SVT?

In stable patients with SVT, the first-line treatments include the Valsalva maneuver and carotid sinus massage to attempt to revert the heart back to sinus rhythm.

How does adenosine work in managing SVT, and what are some considerations when administering it?

Adenosine works by slowing cardiac conduction through the AV node, interrupting the reentrant circuit to restore sinus rhythm. It must be administered rapidly and can cause brief periods of asystole or bradycardia. It is contraindicated in patients with asthma, COPD, or heart block.

What are the long-term management options for patients with paroxysmal SVT?

Long-term management includes medications like beta-blockers, calcium channel blockers, or amiodarone, and radiofrequency ablation, which can potentially cure the arrhythmia by eliminating the abnormal electrical pathway.