Tips for you to differentiate Paroxysmal Supraventricular Tachycardia (PSVT) from Sinus Tachycardia

MD Tobias Araujo, specialized in Cardiology and Medicine Intensive

AHA Instructor (BLS, ACLS and PALS)

Patient was admitted to the Emergency Department complaining of palpitations for about 1 hour, associated with mild shortness of breath. The patient is 42 years old and has Systemic Arterial Hypertension and Dyslipidemia. The patient is concerned about the symptoms. BP: 190 / 105 mmHg; P: 165 bpm; RR: 18ipm; Cardiovascular and respiratory systems without alterations.

Patient’s ECG strips:

In view of the patient’s ECG strips and the patient's clinical history, the possible diagnoses were discussed:

Paroxysmal Supraventricular Tachycardia (PSVT) or Sinus Tachycardia?

PSVT is an abnormal type of tachycardia, considered a cardiac arrhythmia. Triggered after a short circuit in the upper part of the heart, above the ventricles, the electrical impulse generated has a reentrant mechanism (makes loops) before going to the ventricles. On an ECG strip or on a monitor, usually you see QRS followed by T waves (video bellow)

Sinus Tachy is a normal heart rhythm but with an abnormal high Heart Rate (HR) - above 100 bpm. On an ECG strip or on a monitor, usually you see P waves followed by QRSs and T waves (video below).

When there is a Sinus Tachy with too high HRs, the P wave merges with the T wave, giving the impression of absence of a P wave, confusing with PSVT. On the other hand, when there is a PSVT in which the P wave is found just before the QRS (in PSVP P waves can go before or within the QRS complex), one can confuse it with Sinus Tachy.

I will give you some tips on how to differentiate such diagnoses:

Although it is not a fixed rule, in most cases, patients with SVT have a higher HR, ranging from 150 to 250 bpm, while Sinus Tachy usually presents a HR up to 150-170 bpm. But remember: this is not a fixed rule.

PSVT is a tachyarrhythmia that begins and stops abruptly, while Sinus Tachycardia has gradual onset and end. For example, in a patient with sinus tachycardia due to infection, the HR increases as the infection worsens. In SVT, the arrhythmia mechanism happens suddenly.

In PSVT, the HR usually remains constant or varies a little when compared to Sinus Tachycardia, which the HR varies over seconds or minutes according to the worsening or improvement of the tachy cause (according to the body demanding).

In PSVT, you do not find any obvious reason for Sinus Tachy, such as fever, pain, anxiety crisis, infection, thyrotoxicose, dehydration, emotional stress etc

Sudden palpitations are frequent in PSVT, unlike Sinus Tachy, in which other symptoms (relating to the underlying cause) are more prominent. For example, in a patient with Sinus Tachy in the course of a respiratory infection, fever, cough, chills, shortness of breath can have more importance than palpitations.