Efficacy of Delayed Enhancement MRI-Guided Ablation vs Conventional Catheter Ablation of Atrial Fibrillation: The DECAAF II Study

BACKGROUND AND INTRODUCTION:

Atrial fibrillation (AF) is the most common cardiac arrhythmia affecting millions of people in the US and around the world. Treating AF continues to be a challenge. Over the last 15 years, catheter based AF ablation procedure has been widely adopted. Approximately 50% of patients treated with catheter ablation present with a persistent type of the arrhythmia. Unfortunately, ablation results in this population have been dismal, not only because of low success rates in suppressing arrhythmias, but also from a healthcare cost point of view. In fact, the long-term success of such a procedure has been reported to be as low as 20%, and patients may need more than two ablation procedures to achieve temporary arrhythmia suppression. The cost of AF ablation among Medicare patients followed for a year after ablation was found to be US$16,049 ± 12,536 if ablation was successful versus US$19,997 ± 13,958 for failed ablation. A major issue contributing to the low success of catheter ablation is the lack of a protocol to appropriately select patients that would respond to this treatment. Currently, cardiologists base their decision to ablate persistent AF on various comorbidities, a concept that has not been proven successful. With the introduction of AF ablation as a first line therapy option in the recent guidelines, a better and more accurate selection protocol is urgently needed. There is a strong association between AF and atrial tissue fibrosis. Recently, a novel DE-MRI (Delayed-Enhancement MRI) based imaging modality has been demonstrated to reveal the degree of fibrotic atrial tissue in patients suffering from AF. When applied in various studies, including a multicenter study, extent of fibrotic atrial changes was shown to be the strongest independent predictor of a successful treatment in patients undergoing ablation of AF. Moreover, in the multicenter observational study DE-MRI Determinant of Successful Radiofrequency Catheter Ablation of Atrial Fibrillation (DECAAF), the strongest independent predictor of successful outcome was the surface area of fibrosis covered by ablation lesions. In fact, the number of encircled pulmonary veins, the most common adopted approach to ablate AF today, did not predict catheter ablation success.

The use of non-invasive ambulatory electrocardiography (ECG) devices including 24-48 hour Holter monitors and 30-day cardiac event monitors have been widely used for the detection of cardiac rhythm abnormalities. The duration of time for rhythm evaluation is key to detect arrhythmias and conduction abnormalities, as number of arrhythmia diagnoses increases with increasing duration of monitoring. The longer duration of monitoring occurs at the expense of patient comfort and patient compliance. Previous FDA- approved devices for standard of care monitoring are limited in the duration of monitoring. At many institutions, it is standard of care to wear a 60-day cardiac event monitor for the detection and evaluation of cardiac arrhythmias in the post-ablation blanking period.

The percentage of asymptomatic recurrences of AF drastically increases after ablation. Thus, post-procedure devices are necessary for close monitoring and detection of asymptomatic AF in ablation patients. Compliance with the current cardiac event monitors may be low for many reasons. Electrode intolerance due to skin rashes, irritation and/or breakdown, and the unwillingness for continuous devices to be worn are some known areas of non-compliance.

A higher level of monitoring can be provided with use of new wireless ECG technologies, specifically, the FDA approved ECG Check mobile heart monitor designed by Cardiac Designs. This mobile heart monitor will enable patients to record their heart rhythm anytime and anywhere. The device will automatically analyze the ECG for symptomatic or asymptomatic arrhythmias for the duration of their life as long as it is compatible with their current "smart phone" or tablet computer. This is a patient-owned monitor.