What is the Difference Between Sinus Tach and SVT?

The main difference between sinus tachycardia (sinus tach) and supraventricular tachycardia (SVT) lies in their origin, rate, and ECG characteristics. Here are some key distinctions between the two:

1. Origins: Sinus tachycardia is a normal physiological response to stress, fever, dehydration, or strenuous physical activity, while SVT is an abnormal fast heart rhythm starting in the upper chambers (atria) of the heart.
2. Rate: Sinus tachycardia has a heart rate of 100 to 150 beats per minute, whereas SVT has a heart rate of 151 to 250 beats per minute.
3. P wave visibility: In sinus tachycardia, P waves are clearly visible and positive (upright) in leads I and aVF. In SVT, P waves are often difficult to see or absent.
4. Variability: Sinus tachycardia has a variable heart rate that often responds to stimuli or treatment of the underlying cause, while SVT has minimal variability with change in stimulation.
5. Response to vagal maneuvers: The response to vagal maneuvers may only be seen temporarily in sinus tachycardia, while SVT may be terminated by such maneuvers.

To differentiate between sinus tachycardia and SVT, it is essential to consider the patient's presenting complaint, the heart rate, the visibility of P waves on the ECG, the variability of the heart rate, and the response to vagal maneuvers.

Comparative Table: Sinus Tach vs SVT

Here is a table comparing the differences between Sinus Tachycardia and Supraventricular Tachycardia (SVT):

Sinus Tachycardia is characterized by an elevated heart rate of 100-150 beats/min, with P waves being visible and upright in leads I and aVF. It is typically associated with untreated underlying causes like hypovolemic shock. On the other hand, SVT is characterized by a heart rate of 151-250 beats/min, with P waves that may be visible but retrograde and negative in inferior leads - II, III, and aVF. SVT is due to primary electrical abnormalities and is often more symptomatic than Sinus Tachycardia.