LOOP Studie

Diederichsen SZ et al.: Natural History of Subclinical Atrial Fibrillation Detected by Implanted Loop Recorders. J Am Coll Cardiol 74 (2019):2771-2781.

590 Risikopatienten (≥70 Jahre, ≥1 zusätzlicher Risikofaktor) wurden insgesamt 685.445 Tage lang mittels implantiertem Event-Recorder überwacht. VHF-Episoden ≥6 Min. wurden bei 205 Teilnehmern (35%) detektiert. Die mediane VHF-Last betrug 0.13 % der Zeit und steigerte sich mit jeder Verdopplung des NT-proBNP um den Faktor 1.31 (95% CI: 1.02 to 1.68). VHF-Episoden traten an 2.7 % der Tage auf. Bei 33 der VHF-Patienten (16 %) kam es zu einer Progression hin zu 24-Std.-Episoden, während 46 (22 %) in den letzten 6 Monaten (oder länger) keine VHF-Episoden mehr zeigten. 185 der VHF-Patienten (90 %) waren anfangs asymptomatisch und 178 (87 %) blieben es auch im Follow-Up. Die mittlere Herzfrequenz während VHF lag bei 96 min-1, 24 min-1 schneller als bei Sinusrhythmus tagsüber.

As new heart rhythm monitoring technologies emerge, subclinical atrial fibrillation (AF) signifies a future challenge to health care systems. The pathological characteristics of this condition are largely unknown.

This study sought to characterize the natural history of subclinical AF in at-risk patients from the general population.

The authors studied 590 individuals ≥70 years of age with ≥1 of hypertension, diabetes, previous stroke, or heart failure, without history of AF, undergoing long-term implantable loop recorder monitoring as part of the LOOP (Atrial Fibrillation Detected by Continuous ECG Monitoring Using Implantable Loop Recorder to Prevent Stroke in High-risk Individuals) study. Baseline assessments included N-terminal pro–B-type natriuretic peptide (NT-proBNP). All day-to-day heart rhythm and symptom data were extracted from the device. Endpoints included AF burden, AF progression, symptom reports, and heart rate during AF.

A total of 685,445 monitoring days were available for analysis. Adjudicated AF episodes lasting ≥6 min were detected in 205 participants (35%). The AF burden was median 0.13% (interquartile range: 0.03% to 1.05%) of the monitoring time and changed by a factor of 1.31 (95% CI: 1.02 to 1.68) per doubling of NT-proBNP. AF episodes were present 2.7% (interquartile range: 1.0% to 15.7%) of monitoring days after debut. Progression to 24-h episodes was seen in 33 of the AF patients (16%), whereas 46 (22%) had no AF episodes in the last 6 months of monitoring or longer. Symptoms were absent in 185 (90%) at debut, and 178 (87%) never reported AF-related symptoms during follow-up. The averaged heart rate during AF was 96 (interquartile range: 83 to 114) beats/min, 24 (interquartile range: 9 to 41) beats/min faster than daytime sinus rates.

Although previously unknown AF was highly prevalent, the burden was low, and progression was limited. In addition, symptoms were scarce, and the heart rate was only modestly elevated. (Atrial Fibrillation Detected by Continuous ECG Monitoring Using Implantable Loop Recorder to Prevent Stroke in High-risk Individuals [LOOP]

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