The Comparative Efficacy of the Zio Patch vs Implantable Loop Recorder in Atrial Fibrillation

Summary Atrial fibrillation (AF) is the most common arrhythmia, increasing in prevalence with age characterized by chaotic contraction of the atrium. An estimated 2.2 million people in the United States and 4.5 million in the European Union have AF.[1,2] AF is associated with heart failure, hemodynamic impairment, and symptoms affecting quality of life. Patients have an increased risk of thromboembolic events, including stroke, resulting in significant morbidity, mortality, and costs. [1-5]

Diagnosis of atrial fibrillation is made via an electrocardiogram (ECG) recording. Any arrhythmia that has the ECG characteristics of AF and lasts sufficiently long for a 12-lead ECG to be recorded, or at least 30 seconds on a rhythm strip, should be considered an AF episode.[6] The diagnosis requires an ECG or rhythm strip demonstrating: 1) "absolutely" irregular RR intervals (in the absence of complete AV block), 2) Absence of distinct P waves on the surface ECG, and 3) an atrial cycle length (when visible) that is usually variable and less than 200 msec. [7]

During the past decade, catheter ablation of atrial fibrillation (AF) has evolved rapidly from an investigational procedure to its current status as a commonly performed ablation procedure in many major hospitals throughout the world. The goal of the ablation is to isolate the pulmonary veins from which in the majority of the population atrial fibrillation originates. During the past several years a large number of meta analyses have been performed in the hope of better defining the efficacy of AF ablation. Overall, the success rate was 77.8% in the ablation arm as compared with 23.3% in the control group.

Catheter ablation has decreased the recurrence of AF by 71% (relative risk 0.29). Several other meta analyses of randomized clinical trials have confirmed these findings [8-12].

Background and Significance Arrhythmia monitoring in patients undergoing atrial fibrillation ablation is challenging. Trans-telephonic monitors (TTMs) are cumbersome to use and provide limited, temporal assessment. Implantable loop recorders may overcome these limitations. The ABACUS study sought to evaluate the utility of implantable loop recorders (ILRs) versus conventional monitoring (CM) in patients undergoing AF ablation. In AF ablation patients, ILR detected more arrhythmias than CM. However, false detection remained a challenge including the inability to the ILR to detect atrial fibrillation less than 2 minutes in duration. The investigators concluded that with adequate oversight, ILRs may be useful in monitoring these patients after ablation. [13] ILR's have been convenient to patients due to the fact that they do not require electrodes or patches. In addition there is no external monitor that must be accompanied with the electrode adhesive pair.