title: Smart detection of atrial fibrillation†.
abstract: OBJECTIVE
  Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice, and its paroxysmal nature makes its detection challenging. In this trial, we evaluated a novel App for its accuracy to differentiate between patients in AF and patients in sinus rhythm (SR) using the plethysmographic sensor of an iPhone 4S and the integrated LED only.
  
  
  RESULTS
  For signal acquisition, we used an iPhone 4S, positioned with the camera lens and LED light on the index fingertip. A 5 min video file was recorded with the pulse wave extracted from the green light spectrum of the signal. RR intervals were automatically identified. For discrimination between AF and SR, we tested three different statistical methods. Normalized root mean square of successive difference of RR intervals (nRMSSD), Shannon entropy (ShE), and SD1/SD2 index extracted from a Poincaré plot. Eighty patients were included in the study (40 patients in AF and 40 patients in SR at the time of examination). For discrimination between AF and SR, ShE yielded the highest sensitivity and specificity with 85 and 95%, respectively. Applying a tachogram filter resulted in an improved sensitivity of 87.5%, when combining ShE and nRMSSD, while specificity remained stable at 95%. A combination of SD1/SD2 index and nRMSSD led to further improvement and resulted in a sensitivity and specificity of 95%.
  
  
  CONCLUSIONS
  The algorithm tested reliably discriminated between SR and AF based on pulse wave signals from a smartphone camera only. Implementation of this algorithm into a smartwatch is the next logical step.
authors.affiliation: Department of Internal Medicine, Basel University Hospital, Petersgraben 4, Basel 4031, Switzerland.|Department of Cardiology, Bern University Hospital, Freiburgstrasse 10, Bern 3010, Switzerland.
authors.forename: Lian
authors.initials: L
authors.lastname: Krivoshei
authors.affiliation: Department of Internal Medicine, University Hospital Regensburg, Franz-Josef-Strauß-Allee 11, Regensburg 93053, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Weber
authors.affiliation: Medical Outpatient Clinic, Basel University Hospital, Petersgraben 4, Basel 4031, Switzerland.
authors.forename: Thilo
authors.initials: T
authors.lastname: Burkard
authors.affiliation: Department of Internal Medicine, Basel University Hospital, Petersgraben 4, Basel 4031, Switzerland.
authors.forename: Anna
authors.initials: A
authors.lastname: Maseli
authors.affiliation: Department of Internal Medicine, Basel University Hospital, Petersgraben 4, Basel 4031, Switzerland.
authors.forename: Noe
authors.initials: N
authors.lastname: Brasier
authors.affiliation: Department of Cardiology, Basel University Hospital, Petersgraben 4, Basel 4031, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Kühne
authors.affiliation: Department of Internal Medicine, Basel University Hospital, Petersgraben 4, Basel 4031, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Conen
authors.affiliation: Preventicus GmbH, Tatzendpromenade 2, Jena 07745, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Huebner
authors.affiliation: Preventicus GmbH, Tatzendpromenade 2, Jena 07745, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Seeck
authors.affiliation: Department of Internal Medicine, Basel University Hospital, Petersgraben 4, Basel 4031, Switzerland.
authors.forename: Jens
authors.initials: J
authors.lastname: Eckstein
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000175:diagnosis*; D003936:Diagnosis, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008875:Middle Aged; D063731:Mobile Applications; D017156:Photoplethysmography / Q000295:instrumentation* / Q000379:methods; D063177:Pulse Wave Analysis / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000068997:Smartphone; D014584:User-Computer Interface
keywords: Atrial fibrillation; Pulse wave analysis; Rhythm monitoring; Smartphone