A Recipe for Success in the Treatment of Atrial Flutter

The treatment of certain arrhythmia substrates sometimes requires deeper and/or wider lesions than can be created with standard radiofrequency (RF) ablation. Typical atrial flutter is one of these substrates. The ablation of typical atrial flutter requires contiguous ablation of the tricuspid valve/inferior vena cava isthmus, which is a critical component of the atrial flutter circuit. In this instance, we have found that an ablation tool that can create larger than normal lesions can be beneficial. By delivering greater total lesion volume than standard ablation, case times can be decreased significantly and recurrence rates improved. Unfortunately, delivering higher power into the tissue can sometimes cause superheating at the endocardial surface, which can result in coagulum formation on the ablation catheter tip. Until recently, the primary method of managing coagulum formation on the tip of an ablation catheter has been through the use of temperature control. We know that by using temperature-guided automatic power modulation, near-boiling temperatures at the electrode/tissue interface can be avoided, thus minimizing the incidence of coagulum. However, this also limits the total amount of power delivered into the tissue and, in turn, overall lesion size. We believe that cooled ablation efficiently addresses both of these issues (Figure 1). By actively cooling the catheter tip, temperatures at the tissue surface can be minimized. Since boiling temperatures are avoided, coagulum formation is less likely to take place and greater total energy can be delivered to the tissue. This gives us the ability to deliver greater total energy which can facilitate wider, deeper lesions while reducing the overall incidence of coagulum formation. We have found that because energy delivery can be titrated to achieve the desired affect, cooled ablation can produce shallow and deep lesions alike. Physicians can control overall lesion size by minimizing, titrating and/or maximizing power delivery. The Electrophysiology Laboratory at North Ridge Medical Center in Fort Lauderdale, Florida is a busy, progressive, private practice facility presently serving five electrophysiologists. An estimated one-third of our total ablation volume represents the treatment of atrial flutter. In 1999, although his success rate was very high at the time, our current EP Lab Director, Murray Rosenbaum, MD, became interested in cooled ablation and agreed to evaluate the Chilli RF ablation system in the interests of decreasing case times and finding the most efficient and effective tool available to us for the treatment of atrial flutter. Later that year, we acquired the Boston Scientific/EP Technologies Chilli Generator. During our first case, we successfully ablated atrial flutter with a single drag lesion. We ve been using Chilli as the first line treatment for atrial flutter ever since. Dr. Rosenbaum s technique involves the use of a 90? long sheath for added stability. The sheath is inserted into the patient through the Right Femoral Vein and the sheath tip is pointed in the direction of the tricuspid valve. Next, a standard curve Chilli catheter is inserted into the sheath, slightly through the tricuspid valve. By delivering RF energy and slowly withdrawing the entire sheath assembly from the tricuspid valve into the inferior vena cava, an efficient linear lesion can be produced and bidirectional block achieved (Figure 2). Since the Chilli generator provides for up to 295 seconds of continuous power output, the resulting longer delivery durations lend themselves to larger lesions as well. In short, we have found that by delivering higher outputs for longer periods of time, less lesions are necessary to terminate conduction through the isthmus. Post ablation, Dr. Rosenbaum tests efficacy through the absence of any electrical activity along the ablation line and by testing for bidirectional block at the isthmus. He is convinced that the use of Chilli has contributed to both shorter case times (often less than 1 hour) and fewer recurrences. Our average atrial flutter ablation total case time is about 90 minutes and requires about 3 linear lesions per case. The need for larger lesions is not always quite so obvious, as with the instance of standard ablation of ischemic left ventricular tachycardia. Obviously, the thick nature of the ventricular wall presents a challenge for this kind of ablation. Stubborn AV nodes that would otherwise require arterial access to the left side of the heart can often be ablated from the right side with cooled ablation in an ablate-and-pace scenario for the treatment of atrial fibrillation. In truth, any substrate can be efficiently treated with cooled ablation. By titrating power outputs, our physicians safely create shallow lesions and larger lesions when necessary. This flexibility is very valuable in today s cost-conscious environment. Despite using Chilli for every atrial flutter, we have experienced no complications to date associated with the Chilli catheter. Moreover, the staff has embraced the technology because it is easy to use and has significantly contributed to shorter case times. In our opinion, closed-path cooling technology provides the benefits of cooled ablation without the potential complications of hypervolemia and pulmonary embolism. Using a hollow-tip electrode and lumens within the catheter shaft, saline is infused through the tip of the catheter at 0.6 ml/second and collected without infusing saline into the heart. The room-temperature saline carries heat away from the electrode/tissue interface and surface temperatures are minimized. The symmetric tip provides for lesion symmetry and the lack of saline infusion eliminates issues associated with the virtual electrode effect and hypervolemia. In summary, our success in treating atrial flutter has translated to happier patients. By using the most appropriate tool for the job at hand, we have improved patient outcomes and overall satisfaction. The benefits associated with the Chilli system are clear and represent a major contribution to the electrophysiology community. Based on our experience, we believe closed cooled ablation should be considered the standard of care for the treatment of typical atrial flutter.