AF ABLATION TECHNIQUES AND TECHNOLOGY
RADIOFREQUENCY VS CRYOBALLOON ABLATION
Multiple different energy sources can be used to achieve the desired ‘ablation’ of targeted cardiac tissue to treat AF.
Cryoballoon treatment uses a balloon designed to create a circular ablation ring around the opening (ostium) of the pulmonary veins and delivers deep freeze (very low temperatures) cryoablation to treat the tissue. The technique may commonly be called “one shot ablation” and is best suited to a first time pulmonary vein isolation procedure.
Radiofrequency treatment is most commonly applied through an accurate ‘pencil-like’ catheter tip. It can be used to create customized rings of ablation around the pulmonary veins, but is also very useful for targeting residual arrhythmia areas during repeat AF ablation procedures or for targeted treatment of other types of arrhythmias in the atria (or ventricles). There do not appear to be any significant differences in the success rates or possible overall complications between the different ablation energy types when used by a skilled ablation operator.
3D CARDIAC MAPPING SYSTEMS
Specialised cardiac navigation technology is utilised during catheter ablation procedures to provide an accurate 3D reconstruction of the heart’s anatomy, the electrical signals as they travel through the heart and the position of equipment inside the heart during the procedure. “Integration” of other cardiac imaging techniques with 3D mapping is also used including pre-procedural CT scans, intracardiac echocardiography and new force/ tissue contact sensing technologies.
The currently utilized 3D mapping systems include Ensite System (Abbott), Carto System (Biosense Webster) and the Rhythmia System (Boston Scientific). The different 3D mapping systems have varying features that make them best suited to individual patient cases.
Echocardiography uses ultrasound waves to visualise moving images of the heart. Intracardiac echocardiography (ICE) uses a miniaturised ultrasound transducer mounted on a wire, or catheter which is advanced inside the heart during a catheter ablation procedure. The use of ICE during catheter ablation may improve safety and procedure results and allows rapid identification of potential complications.
Dr Karen Phillips is a pioneer of ICE use in Australia.
ABLATION CATHETER FORCE AND TISSUE SENSING
Effective ablation treatment can be impacted by inconsistent energy delivery into the targeted heart tissue, particularly as catheter abltion procedures are performed via keyhole approach while the heart is still beating and moving.
Tissue contact and force-sensing technology in the tip of the catheter delivering the ablation energy tells the doctor when good catheter-heart tissue apposition is obtained. Too much force at the catheter tip can cause tissue injury and procedure complications, while too little force can lead to incomplete ablation, which essentially means that atrial fibrillation can recur down the road requiring a repeat ablation procedure.
This technology assists with more accurate, consistent and safer performance of the radiofrequency ablation treatment.
HIGH DENSITY MAPPING CATHETERS AND SYSTEMS
Patients with atrial fibrillation may also develop other types of arrhythmias in their atria (top chambers) over time – either as part of a natural progression of the underlying ‘heart condition’ or potentially arising from previous ablation procedures.
These arrhythmias may include atrial tachycardias (relatively focal source of rapid electrical firing in the left or right atrium) or atrial flutter (endless loop large circuit in the left or right atrium). These type of arrhythmias require a careful 3D mapping electrical study of the heart to correctly diagnose the arrhythmia and guide successful radiofrequency ablation treatment.
There have been recent advances with high density mapping catheters and 3D mapping system capabilities which have greatly improved the ability to treat these other arrhythmias that are common in AF patients.
Animation of left atrial flutter circuit rotating around the mitral valve