Circulation: Implantable cardiac monitor can detect presence, absence of a-fib
Use of an implantable leadless cardiac monitor (ICM) in patients can better detect and monitor atrial fibrillation (AF) due to an algorithm that can detect the presence or absence of the heart arrhythmia, a study published online in the Feb. 16 issue of Circulation: Arrhythmia and Electrophysiology found.

“Current methods for detecting AF have limited diagnostic yield,” the authors wrote. “Continuous monitoring with automatic arrhythmia detection and classification may improve detection of symptomatic and asymptomatic AF and subsequent patient management.”

Gerhard Hindricks, MD, PhD, of the University of Leipzig Heart Center in Germany, and colleagues evaluated the performance of the Reveal XT ICM device (Medtronic) implanted in 247 patients who demonstrated likely signs of paroxysmal AF.

The trial took place between September 2007 and July 2008. Study participants were all scheduled for either a pulmonary vein ablation or surgical rhythm control intervention or had documented AF or symptoms of AF.

Four to six weeks after being implanted with the ICM, subcutaneous ECG and sensing and arrhythmia classification markers were continuously recorded for 46 hours using a Holter device (DR220, NorthEast Monitoring) and two surface ECG leads in patients. Researchers then compared the recordings from the ICM  to that of the established method of Holter recordings -- this included the annotation of the surface ECGs on a beat-to-beat basis.

According to the researchers, the Reveal XT incorporates an algorithm that can detect bradyarrhythmias and ventricular tachyarrhythmias. “The dedicated AF detection algorithm uses irregularity and incoherence of RR intervals to identify and classify patterns in the ventricular conduction,” the authors wrote.

Of the 247 patients, 66.8 percent were male, 10.2 percent had a history of stroke of transient ischemic attack and all had an average age of 57. A Holter recording was performed in 235 patients, 206 recordings were suitable for evaluation.

Of these 206 patients, 76 had at least one episode of AF, 73 patients had one AF episode detected by the ICM and three had no detection of AF. Therefore, the researchers found that  the Reveal XT positively detected AF in 96.1 percent of all patients with AF.

According to the researchers, 130 patients had no classification of AF and of those, the ICM confirmed the absence of AF in 111 patients.

The authors said that limitations stem from the study not being generalizable to other ICM devices other than the Reveal XT.

“The technology seems to be promising to improve both the precise detection of AF and the confirmation or absence of AF during long-term follow up, as well as accurately assessing the AF burden," the authors concluded. “The ICM is a promising new diagnostic and monitoring tool for the clinician to manage AF patients independently of symptoms."

Medtronic funded the study.