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Catheter Ablation treatment for atrial flutter

What is atrial flutter?

Atrial flutter is an abnormal rhythm of the heart located in the atrium of the heart. It is characterized by atrial rates of 240 to 400 beats/min. However the heart rate that is measured at the peripheral pulse is not 240-400 beats/min because not every atrial beat is conducted through to the ventricles. The AV node prevents heart beats in excess of 180 beats/min. In a 2:1 atrial flutter, for example, only one atrial beat gets conducted to the ventricle for every 2 atrial beats. Thus, if the atrial rate is 300 beats/min, the heart rate detected at the peripheral pulses would be measured at about 150 beats/min.

Pathophysiology

Atrial flutter is caused by a reentrant rhythm in either the right or left atrium. An extra focus of electrical activity within the atrium creates a self-perpetuating loop that manifests as an extra atrial beat. The loop typically encircles an area of dead or scarred area in the heart.

Typical vs. Atypical flutter

In typical flutter the loop or circuit moves in a counterclockwise direction. In atypical flutter the circuit moves in a clockwise direction.

Catheter ablation procedure

The goal of ablation therapy is to stop the reentrant circuit that is causing the atrial flutter by either burning or freezing the area. This is accomplished by placing a catheter into the venous circulation either through the femoral or subclavian vein, and then guiding it into the atrium of the heart. The atrial flutter is localized using electrodes at the end of the catheter. The catheter is formed into a loop, similar to the circuit of the atrial flutter, and the electrodes then pick up the electrical signals of the atrial flutter as the charges move around the atrium. The electrodes are numbered 1-18, so one can determine the direction and location of the flutter based on when the electrodes “light up” on the screen.

Once the location of the atrial flutter circuit has been identified the goal of the treatment is to interrupt the circuit by essentially cutting one part of the loop so that electrical charges within the circuit can no longer revolve around the loop. Of note, in many areas of the circuit the charges are diffuse and spread out so they create a particularly large area. Theoretically one of these areas can be ablated but it would be much more difficult and take a much longer time. Thus, a particular area has been identified in which the electrical circuit narrows and passes through a much smaller area. This area is called the isthmus and it is located between the inferior vena cava and the tricuspid valve. Another name for it is the cavo-tricuspid isthmus (CTI). Targeting this much smaller area is far easier and takes much less time.

During the catheter ablation procedure the catheter is placed along the CTI and it then burns or freezes the area until the electrodes no longer detect an electrical circuit. Once this is done the procedure is complete and successful. Afterward the patient is continued on anti-coagulation therapy for one month until the heart completely returns to beating normally.

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