Junctional Rhythms and SVT
Junctional Escape Rhythm
| Parameter | Definitions |
|---|---|
| HR | Between 40 and 60 |
| Regularity | Regular |
| P | Either inverted, absent, or retrograde (inverted after QRS) |
| QRS | Narrow QRS complexes |
| P:QRS Ratio | 1:1 if P wave comes before QRS complex |
Junctional Escape Rhythm occurs when the AV node has failed to receive an impulse from the SA node and triggers an impulse itself. The AV node naturally paces between 40 and 60 beats per minute. Since this impulse will travel "backwards" up to the atria, the P-wave will also appear inverted, either before or after the QRS complex. This is termed a retrograde P wave. The P-wave may also be absent if it occurs simultaneous to the QRS complex.
The likely cause of junctional escape rhythm are things to prevent the SA node from firing properly, such as electrolyte imbalances, heart failure, and an MI.
The mainstay "treatment" is to treat the underlying cause, or at least monitor that there's no ill effect if it was a known medication that caused this. If needed, atropine could be used to speed up the heart.
Accelerated Junctional Rhythm
| Parameter | Definitions |
|---|---|
| HR | Between 60 and 100 |
| Regularity | Regular |
| P | Either inverted, absent, or retrograde (inverted after QRS) |
| QRS | Narrow QRS complexes |
| P:QRS Ratio | 1:1 if P wave comes before QRS complex |
Accelerated Junctional Rhythm occurs when some sort of trigger overstimulates the AV node, causing it to overtake the SA node as the pacemaker of the heart. The most common triggers include medication toxicity and an MI.
The mainstay "treatment" is to treat the underlying cause. Treating the underlying cause often will resolve the issue.
Supraventricular Tachycardia (SVT)
| Parameter | Definitions |
|---|---|
| HR | Greater than 150 |
| Regularity | Typically regular |
| P | Not available |
| QRS | Narrow QRS complexes |
| P:QRS Ratio | Not available |
Supraventricular Tachycardia (SVT) is an umbrella term for a number of narrow-complex tachycardias that originated above the ventricles, but is most commonly used to refer to a specific type of tachycardia that involves the AV node. They classically present with a very fast heart rate, and a P wave that is hidden by either the QRS complex or the previous T wave.
Majority of patients with SVT are young and otherwise relatively healthy. They likely presented because of a sudden onset of palpitations or lightheadedness.
In the emergency department, Supraventricular Tachycardia is treated as per ACLS guidelines.