Supraventricular Tachycardia

Question 1

What is the pathophysiology of supraventricular tachycardia

Answer 1

Supraventricular tachycardia (SVT) involves the rapid stimulation of atrial tissue at a rate of 100 to 280 beats/min in adults. During SVT, P waves may not be visible, especially if there is a 1:1 conduction with rapid rates, because the P waves are embedded in the preceding T wave. SVT may occur in healthy young people, especially women.

Question 2

What are some causes of supraventricular tachycardia?

Answer 2

SVT is usually caused by a re-entry mechanism in which one impulse circulates repeatedly throughout the atrial pathway, restimulating the atrial tissue at a rapid rate. The term paroxysmal supraventricular tachycardia (PSVT) is used when the rhythm is intermittent. It is initiated suddenly by a premature complex such as a PAC and terminated suddenly with or without intervention.

Question 3

What are signs and symptoms of supraventricular tachycardia?

Answer 3

Signs and symptoms depend on the duration of the SVT and the rate of the ventricular response. In patients with a sustained rapid ventricular response, assess for palpitations, chest pain, weakness, fatigue, shortness of breath, nervousness, anxiety, hypotension, and syncope. Cardiovascular deterioration may occur if the rate does not sustain adequate blood pressure. In that case, SVT can result in angina, heart failure, and cardiogenic shock. With a nonsustained or slower ventricular response, the patient may be asymptomatic except for occasional palpitations.

Question 4

What treatment is there for supraventricular tachycardia?

Answer 4

• If SVT occurs in a healthy person and stops on its own, no intervention may be needed other than eliminating identified causes. If it continues, the patient should be studied in the electrophysiology study (EPS) laboratory. The preferred treatment for recurrent SVT is radiofrequency catheter ablation, described later in this chapter with treatment of atrial fibrillation. In sustained SVT with a rapid ventricular response, the desired outcomes of treatment are to decrease the ventricular response, convert the dysrhythmia to a sinus rhythm, and treat the cause.
• Vagal maneuvers induce vagal stimulation of the cardiac conduction system, specifically the SA and AV nodes. Although not as common today, vagal maneuvers may be attempted to treat supraventricular tachydysrhythmias and include carotid sinus massage and Valsalva maneuvers. However, the results of these interventions are often temporary and may cause “rebound” tachycardia or severe bradycardia. Further therapy must be initiated.
• In carotid sinus massage, the health care provider massages over one carotid artery for a few seconds, observing for a change in cardiac rhythm. This intervention causes vagal stimulation, slowing SA and AV nodal conduction. Prepare the patient for the procedure. Instruct him or her to turn the head slightly away from the side to be massaged and observe the cardiac monitor for a change in rhythm. An ECG rhythm strip is recorded before, during, and after the procedure. After the procedure, assess vital signs and the level of consciousness. Complications include bradydysrhythmias, asystole, ventricular fibrillation (VF), and cerebral damage. Because of these risks, carotid massage is not commonly performed. A defibrillator and resuscitative equipment must be immediately available during the procedure.
• To stimulate a vagal reflex, the health care provider instructs the patient to bear down as if straining to have a bowel movement. Assess the patient’s heart rate, heart rhythm, and blood pressure. Observe the cardiac monitor and record an ECG rhythm strip before, during, and after the procedure to determine the effect of therapy.
• Drug therapy is prescribed for some patients to convert SVT to a normal sinus rhythm (NSR). Adenosine is used to terminate the acute episode and is given rapidly (over several seconds) followed by a normal saline bolus.