Treating Cardiac Arrhythmias with catheter ablation
September 30, 2014
By Adam H. Zivin, MD, FACC, FHRS
Cardiac catheter ablation is an invasive procedure done to treat abnormal rapid or irregular heart rhythms (arrhythmias). Ablation can be used to treat both supraventricular arrhythmias coming from the upper chambers of the heart (atria) including paroxysmal supraventricular tachycardia (PSVT), atrial flutter, and atrial fibrillation, and ventricular arrhythmias coming from the lower chambers (ventricles).
Different types of catheter ablation for cardiac arrhythmias
“Ablation” refers to localized destruction of tissue, so the area that is being ablated needs to be carefully targeted and the ablation closely controlled. The precise areas targeted for ablation depend on the type of arrhythmia, which sometimes is known before the procedure, but often needs to be clarified or confirmed invasively during the procedure. That being said, not all tachycardias are amenable to ablation or even require treatment, but when non-drug treatment of appropriate tachycardias is appropriate, catheter ablation can be an excellent option.
Ablation can be performed either with “heat” or cold. In Radiofrequency Ablation, radiofrequency energy is delivered from the tip of the ablation catheter, which causes the tissue to heat up, much like a microwave oven heats food. For cold, or “cryoablation”, an electrode or balloon at the catheter tip is cooled with liquid nitrous oxide to -35 degrees C or colder, destroying the tissue through frostbite.
The methods used depend on the arrhythmia being treated, its location, patient-specific factors, and physician preference. The majority of arrhythmias are ablated using radiofrequency energy (“heat”), though cryoablation (“cold”) may be used in selected cases, particularly in the pediatric population, and the Arctic Front cryoballoon has become an important first-line ablation technique for treating atrial fibrillation.
How we carefully target ablation for cardiac arrhythmias
Targeting and ablating the correct area within the heart requires the ability to steer the catheter, monitor its location, and map the electrical circuit.
Historically, monitoring the position of the catheters was done visually with Xray (fluoroscopy) and the “mapping” of the arrhythmia circuit was done by recording the electrical signals recorded by the catheters on what amounts to a multichannel oscilloscope. Over the past decade, however, the shift has been to use 3D non-fluoroscopic mapping. With these systems, the position of the catheter in the heart is determined in three dimensions through the use of electromagnetic fields. These systems also record the electrical activation within the heart recorded by the catheters and these data are displayed together in a color-coded 3 dimensional model. These mapping systems improve our ability to determine the electrical circuits and location for ablation, but also reduce the Xray exposure to both the patient and the medical staff.
Conventional ablation catheters are steered by pull-wires within the catheter controlled manually by the physician. Swedish also has a robotic system, called Stereotaxis, which steers radiofrequency-type catheters using large external magnets.
Why you should consider catheter ablation for cardiac arrhythmias
Catheter ablation of arrhythmias presents one of the few opportunities in cardiac medicine for a drug-free cure.