Catheter Ablation for Supraventricular Tachycardia (SVT)

What does a catheter ablation procedure involve?

Catheter ablation is a minimally invasive procedure. The basic principle of the procedure is to identify the region of the heart where the abnormal electrical activity originates from and to modify the heart tissue in that region by delivering heat (radiofrequency energy) or in certain circumstances, freezing therapy (cryoablation). The end result of the modification is that the abnormal electrical activity, which may have been an abnormal ‘circuit’ or an abnormal ‘triggering switch’ is eliminated.

What are the success rates and potential risks?

The success rates associated with ablation of supraventricular tachycardia are 95%. In the remaining 5%, an additional procedure maybe necessary to eliminate the arrhythmia.

Complications associated with catheter ablation of SVT are rare however can be significant. Potential complications include:

  • Damage to the artery or vein at the access site (1 in 200 risk)
  • Buildup of fluid in the sac around the heart needing a drain to remove the fluid (1 in 500 risk)
  • Blood clots resulting in heart attack or stroke (1 in 1000 risk)
  • Need for permanent pacemaker (1 in 100 risk)

What is the procedure like from a patient’s perspective?

A catheter ablation procedure is performed in a specific environment within a hospital referred to as a cardiac catheterization laboratory. During the procedure, multiple members of a team will be involved, including the heart rhythm specialist doctor (who will perform the procedure), cardiac physiologists and cardiac nurses. The cardiac nurses assist with ensuring that the patient is comfortable and monitor vital signs while the physiologists monitor various technical parameters associated with the procedure. The procedure maybe performed with a patient under conscious sedation (awake with medications administered though the vein to help the patient to relax) or in certain circumstances, under general anaesthesia (in which case an anaesthetist will also be present).

The majority of SVT ablation procedures are performed under conscious sedation. After the sedative has taken effect, local anaesthetic will be injected using a small needle on the top of the leg to numb the puncture site. Once the area is numb, a needle will be used to puncture the vein. A hollow sheath will be introduced into the vein. Long thin tubes, called catheters are inserted into the into the hollow sheath and carefully advanced into the heart.

X-ray guidance and/or specialized electrical mapping systems will be used to guide the physician to target specific areas of the heart (where the abnormal impulses originate). In the majority of cases, patients are in a normal rhythm (sinus rhythm) at the start of the procedure. In order to investigate the exact mechanism of the SVT, an electrophysiology study is performed at the start of the procedure. The study involves generating artificial electrical impulses in the heart in order to start the patient’s SVT. One SVT starts, various measurements are taken from the electrical signals from within the heart in order to pinpoint where the abnormal electrical activity is originating from.

Once the source of the heart rhythm abnormality is identified, radiofrequency energy is applied to eliminate the abnormal electrical activity. Patients may experience mild discomfort during the ablation procedure. The procedure is predicted to last between 2-4 hours.

After the procedure, the catheters and sheaths will be removed, and manual pressure will be applied over the puncture site to stop bleeding. Patients are subsequently required to lie flat for a period of 2-4 hours to ensure that the bleeding remains controlled. During this period, nursing staff will monitor the puncture site and also vital signs.

What happens after hospital discharge?

The majority of patients are discharged after an overnight stay. Patients may return to work one week after the ablation procedure. However, if a patient’s occupation involves heavy lifting, the physician may recommend increasing the time off work to two weeks.

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