When is an arrhythmia procedure necessary?
Arrhythmias can start in either the atria (the heart’s two upper chambers) or in the ventricles (the two lower, or pumping, chambers). Procedures can be performed for different types of arrhythmias, including:
- Atrial fibrillation, a type of supraventricular tachycardia. In a normal heartbeat, the heart’s electrical system causes the atria to contract (squeeze) first, followed by contraction of the ventricles, which pump blood to the body. In atrial fibrillation, electrical impulses don’t follow this route. Instead, fast and disorganized electrical impulses spread through the atria at different times, preventing the atria from contracting evenly. Thus, the atria cannot squeeze blood into the ventricle efficiently. Fibrillation is the act of the atria contracting irregularly. Atrial fibrillation can be ablated surgically by a procedure known as the Maze procedure.
- Atrial tachycardia, a sustained fast heart rate (160 to 190 beats per minute) originating from the atria. (A normal heart rate is 60 to 90 beats per minute.)
- Ventricular tachycardia, a sustained fast heart rate originating from the ventricles
- Supraventricular tachycardia (SVT), an arrhythmia that originates in the atria in which the heart beats faster than 100 beats per minute (which can cause an inadequate blood supply to the body). In SVT, the heart can beat up to 300 times per minute.
Some patients with SVT have what is called an accessory pathway, which is an abnormal muscle located between the atria and ventricles. Patients with accessory pathways may also have Wolff-Parkinson-White syndrome, which is a form of SVT in which abnormal electrical signals can re-enter the heart through the accessory pathway. This can cause dangerous arrhythmias that can increase the chances of sudden death.
In childhood, accessory connection-mediated tachycardia accounts for at least 80% of SVT. The goal of catheter ablation for Wolff-Parkinson-White syndrome is to ablate accessory connections that are responsible for the re-entry of the electrical signal and the tachycardia.
What is the Maze procedure?
A surgery called the Maze procedure was developed to ablate atrial fibrillation. In the Maze procedure, several incisions or lesions are created in the right and left atria in order to form scar tissue that blocks the chaotic electrical impulses from entering the heart. As a result, the electrical impulses are channeled into a single path to the atrioventricular (AV) node, as normal, to allow the atrium to contract uniformly. The AV node then sends the signal to the ventricles, causing them to contract.
Almost all of these surgical approaches include removal of the left atrial appendage, a small, ear-shaped flap of tissue located in the left atrium. The left atrial appendage is a potential source of blood clots in patients who have atrial fibrillation.
Advantages of the Maze procedure in patients who have atrial fibrillation are reduced risks of stroke, blood clots, and hemorrhage.
The traditional surgical Maze procedure is known as the "cut and sew Maze" because it relies on surgical incisions. It is difficult to perform and requires that the heart be stopped for 45 to 60 minutes, during which time a heart-lung machine is used to circulate blood.
Instead of cutting into the wall of the atria, newer techniques to perform Maze surgery use such techniques as radiofrequency, microwave, laser, ultrasound, or cryoablation (freezing). The Cox-Maze III procedure, for example, is a less invasive Maze procedure that uses a bipolar radiofrequency energy. It takes less time to perform than the traditional "cut and sew" Maze procedure.
In patients with atrial fibrillation who also have certain forms of structural heart disease, a modified Maze procedure using cryoablation lesions in addition to surgical lesions is effective at blocking abnormal electrical impulses from re-entering the heart.
What are the treatment options for ventricular arrhythmia?
Treatment options for ventricular tachycardia are more limited. Implantable defibrillators have been shown to prevent sudden cardiac death caused by ventricular tachycardia and fibrillation. An implantable defibrillator is an electronic device that constantly checks the patient’s heart rhythm. When it detects a very fast, abnormal heart rhythm, it delivers energy to the heart muscle, allowing the heart to beat in a normal rhythm again.
In children, pacemakers are sometimes implanted when a congenital heart defect is repaired and the patient has ventricular arrhythmias. It may also be used in cases in which the child has ventricular arrhythmias and a strong family history of sudden death.