Paroxysmal Supraventricular Tachycardia

Paroxysmal Supraventricular Tachycardia (PSVT) has two forms: AV nodal recurrent tachycardia and Atrioventricular recurrent tachycardia. Supraventricular tachycardia: Tachyarrhythmias rising above his bundle, mainly from the atria. Following are the types of supraventricular tachycardia:

• Atrial fibrillation
• Atrial flutter
• Paroxysmal supraventricular tachycardia
  • AV nodal reentrant tachycardia (AVNRT)
  • Atrioventricular reentrant tachycardia (AVRT)

AV Nodal Reentrant Tachycardia (AVNRT)

AV nodal reentrant tachycardia (AVNRT) has a Paroxysmal onset and is more common in women than in men.

Clinical Presentation of AV Nodal Reentrant Tachycardia (AVNRT)

• Palpitations are the most common clinical presentation. The heart rate can go upto 150-250/min. The heart rate will be Rapid and regular.
• The patient might sense an anxiety attack
• Pre-syncope/syncopal attack is due to the decreased stroke volume 
• Chest pain is present in underlined coronary artery disease patients 
• Dyspnea
• Pulmonary edema
• Polyuria 

Clinical Examination of AV Nodal Reentrant Tachycardia (AVNRT)

• Heart rate: 140-280/min and Regular

Pathways in AV node

The Two important functional pathways in AV Node are:

ECG Findings in AV Nodal Reentrant Tachycardia (AVNRT)

Slow fast AVNRT

Slow fast NRT Has very short QRS and P wave interval. The P wave is not visible as it is merged or hidden within the QRS complex, or the P wave appears after the QRS complex. QRS Complex is Narrow. RR interval is Reduced. ST segment depression is also seen.

Treatment of AVNRT is done by administration of 12 mg adenosine. The Pseudo P wave is absent.

Fast slow AVNRT

The P wave appears after the QRS complex. If a time interval is present between the QRS complex and the P wave, then a Diagnosis of Fast, slow AVNRT is made. It occurs in 10% of patients and is associated with a fast AV nodal pathway for Anterograde conduction.

Retrograde conduction is the Slow pathway, which is seen in lead 2.

Slow slow AVNRT

Slow slow AVNRT is also known as Atypical AVNRT. It is a Rare form (1-5%). Tachycardia with P wave seen in mid-diastole. It is often misinterpreted as the sinus tachycardia.

Treatment of Paroxysmal supraventricular tachycardia (PSVT)

There are three options for the treatment of AV Nodal Reentrant Tachycardia (AVNRT). Let us read briefly about them. These have been discussed in great detail on the PrepLadder app.

Mechanical measures

These medical treatments will Terminate arrhythmia in 25% of the patients. The main goal here is to Increase the vagal activity. The Manoeuvers include 

Valsalva maneuver

This is the most commonly followed medical management. The patient has to keep the syringe connected to the manometer. Blow the air until the reading reaches 40 mmHg. The individual's intrathoracic pressure rises. The patient should lie down at 45 degrees for 15 seconds.

The tube is Disconnected from the mouth. Then, the Patient should lie down in the supine position, and Passive leg raising is performed (15 sec). To Increase the effectiveness of the Valsalva maneuver, the Patient needs to sit in the initial position (45 degrees for 30 seconds). If the patient is not responding, the procedure is repeated a second time.

Carotid Sinus Massage

Massage is done either in the left or right carotid artery. Generally, it is done on the Right carotid first for  10-20 seconds. The only Contraindication to Carotid Sinus Massage is Carotid bruit. If Unsuccessful, then Left carotid sinus massage should be done. The patient should not exert pressure on both sides at the same time. 

Diving Reflex

Facial contact with cold water induces Transient bradycardia and Terminates PSVT.

Medical Therapy

If the mechanical measures fail then medical therepy is done. The Drugs include

• Adenosine (DOC)
• Non dihydropyridine calcium channel blockers
  • Verapamil
  • Diltiazem 
• Beta blockers
• Antiarrhythmic drugs

Adenosine

Adenosine is the First-line drug. It has a brief duration of action and has Minimal negative inotropic effect. The route of administration is IV and. The Half-life of Adenosine is 10 sec. The Dose given is 6 mg + 20 ml of normal saline (Bolus). The Second dose of 12 mg

Adenosine's mechanism of action is blocking the electrical conduction through the AV node. The Efficacy of the drug is 90%

Adenosine administration needs to be closely and continuously monitored. A Defibrillator should be available at all times.

Adverse effects of Adenosine are:

• Minor side effects
• Transient flushing
• Chest discomfort
• Headache
• Nausea 
• Excitation of atrial and ventricular tissues
  • Atrial fibrillation (12%)
  • Rarely ventricular fibrillation 
• Reactive airway disease as adenosine causes bronchospasm 

Contraindications of Adenosine is Bronchial asthma and COPD 

Cardioversion

Cardioversion is Preferred in two conditions:

• Hemodynamically unstable 
• Contraindication of adenosine/non dihydropyridine calcium channel blockers

Synchronized electrical cardioversion is given to the patient at a Dose of 100 J.

Prevention of PSVT

There are two methods used for the prevention of PSVT 

• Catheter ablation
• Medical management

Also Read: Takotsubo Cardiomyopathy : Definition, Pathogenesis

Frequently Asked Questions:

Q: Name a mechanical maneuver that terminates PSVT by increasing vagal activity.

Answer: Valsalva

Q: The primary symptom of PSVT.

Answer: palpitations

Q: Which type of PSVT involves reentry around the AV node?

Answer: AVNRT

Q: The type of tachycardia that raises above the bundle of His is known as?

Answer: Supraventricular

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