Ablation of atrial fibrillation
Ablation of atrial fibrillation is a more complex procedure than other procedures used to treat arrhythmias. It performs electric insulation of pulmonary veins using radiofrequency electricity supply.
What is ablation of atrial fibrillation?
Atrial fibrillation is a supraventricular arrhythmia that is triggered by electrical impulses from the myocardial muscle cells present at the junction of the four pulmonary veins, which carry oxygenated blood from the left pulmonary circulation, and the left atrium.
The aim of the procedure is to cause electrical isolation of the pulmonary veins creating a circular scar at the level of its outlet in the left atrium by delivering radiofrequency (electric energy).
The ablation procedure for atrial fibrillation is technically more complex than other techniques used to treat arrhythmias as it requires the passage of the ablation catheter from the right sections of the heart (which can be reached by venepuncture) to those of the left, which is achieved by passing through an orifice (the foramen ovale) that is closed by a fibrous membrane in adults. The membrane is penetrated with a small needle. After performing the steps in the left sections of the heart, four pulmonary veins are electrically isolated.
The lead guide is released under fluoroscopy (X-ray) based on the anatomical map obtained by a special software (CARTO 3), and the exposures of the images obtained by a CT scan of the heart (which all patients receive prior to the procedure). In view of the increased embolic risk due to the presence of the catheters in the left sections of the heart, patients are kept on anticoagulants for the entire duration of the procedure in order to maintain a high fluidity of blood and reduce the possibility of thrombus formation. The patients are monitored carefully and the blood values are checked regularly indicating the extent of anticoagulation.
How is the procedure performed?
The patient initially undergoes a transesophageal echocardiogram to rule out the presence of intracavitary thrombosis and a heart CT that overlays the carto mapping system. The procedure takes place in the operating room that houses the stereotaxis.
In view of the length of the procedure (up to 5 hours), patients are kept in deep sedation under monitored anaesthesia care. The main steps are finding a right femoral venous access, the introduction of venous catheters (the number 3) in the right-sided heart, execution of the trans-septal puncture (transition from the right heart to the left heart), the introduction of the leads in the left sections and finally the catheter ablation procedure by isolation of 4 circular ostia of the pulmonary veins. After the ablation procedure, the patient is slowly awakened. Considering the regime of anticoagulation, the catheters for venous access on the right femur are retained in place and removed after a few hours when there is a reduction in the size of anticoagulation; At this point the patient is removed from the operating room. In the absence of complications, discharge takes place the day after the procedure.
What are the advantages and disadvantages of the treatment?
The procedure for catheter ablation of atrial fibrillation leads, in a variable percentage between 75% and 90%, to a complete elimination of the arrhythmia; consequently, the same assumption of antiarrhythmic drugs can often be suspended. After monitoring the performance of the heart rhythm in the following months (also by implantation of a loop recorder) the condition can also be evaluated after the suspension of oral anticoagulation therapy. In contrast, in a small percentage of cases, there may be recurrent arrhythmias that require continued arrhythmia therapy and, in some cases, may benefit from a possible new ablation procedure.
Is ablation of atrial fibrillation painful or dangerous?
The procedure is generally well tolerated by patients since the greater part of it takes place in deep sedation. Some discomfort may stem from the procurement of the femoral vascular access (procedure sometimes performed while the patient is still awake).
Which patients can undergo the treatment?
Patients with paroxysmal or persistent atrial fibrillation, or all patients who have episodes of arrhythmias that is not well controlled by antiarrhythmic therapy or patients who do not want to take medications.
In order to monitor the performance of the heart rhythm, diagnose recurrence and guide treatment decisions in all patients undergoing ablation, the implementation of a system loop recorder is recommended. Alternatively, especially in the early stages it is important to perform an ECG monitoring at least quarterly.