title: Non-invasive evaluation of the effect of metoprolol on the atrioventricular node during permanent atrial fibrillation.
abstract: OBJECTIVE
  During atrial fibrillation (AF), conventional electrophysiological techniques for assessment of refractory period or conduction velocity of the atrioventricular (AV) node cannot be used. We aimed at evaluating changes in AV nodal properties during administration of metoprolol from electrocardiogram data, and to support our findings with simulated data based on results from an electrophysiological study.
  
  
  RESULTS
  Sixty patients (age 71 ± 9 years, 42 men) with permanent AF were included in the RATe control in Atrial Fibrillation (RATAF) study. Two 15 min segments, during baseline and metoprolol administration, starting at 2 pm were analysed in this study. Atrial fibrillatory rate (AFR), heart rate (HR), and AV nodal parameters were assessed. The AV nodal parameters account for the probability of an impulse not taking the fast pathway, the absolute refractory periods of the slow and fast pathways (aRPs and aRPf), representing the functional refractory period, and their respective prolongation in refractory period. In addition, simulated RR series were generated that mimic metoprolol administration through prolonged AV conduction interval and AV node effective refractory period. During metoprolol administration, AFR and HR were significantly decreased and aRP was significantly prolonged in both pathways (aRPs: 337 ± 60 vs. 398 ± 79 ms, P < 0.01; aRPf: 430 ± 91 vs. 517 ± 100 ms, P < 0.01). Similar results were found for the simulated RR series, both aRPs and aRPf being prolonged with metoprolol (aRPs: 413 ± 33 vs. 437 ± 43 ms, P = 0.01; aRPf: 465 ± 40 vs. 502 ± 69 ms, P = 0.02).
  
  
  CONCLUSIONS
  The AV nodal parameters reflect expected changes after metoprolol administration, i.e. a prolongation in functional refractory period. The simulations confirmed that aRPs and aRPf may serve as an estimate of the functional refractory period.
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Via Golgi 39, 20133 Milano, Italy valentina.corino@polimi.it.
authors.forename: Valentina D A
authors.initials: VD
authors.lastname: Corino
authors.affiliation: Department of Biomedical Engineering and Center for Integrative Electrocardiology at Lund University (CIEL), Lund University, SE-22100 Lund, Sweden.
authors.forename: Frida
authors.initials: F
authors.lastname: Sandberg
authors.affiliation: Center for Integrative Electrocardiology at Lund University (CIEL) and Arrhythmia Clinic, Skåne University Hospital, SE-22185 Lund, Sweden.
authors.forename: Pyotr G
authors.initials: PG
authors.lastname: Platonov
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Via Golgi 39, 20133 Milano, Italy.
authors.forename: Luca T
authors.initials: LT
authors.lastname: Mainardi
authors.affiliation: Department of Medical Research, Bærum Hospital, Vestre Viken Hospital Trust, Drammen, 3004 Norway.
authors.forename: Sara R
authors.initials: SR
authors.lastname: Ulimoen
authors.affiliation: Department of Medical Research, Bærum Hospital, Vestre Viken Hospital Trust, Drammen, 3004 Norway.
authors.forename: Steve
authors.initials: S
authors.lastname: Enger
authors.affiliation: Department of Medical Research, Bærum Hospital, Vestre Viken Hospital Trust, Drammen, 3004 Norway.
authors.forename: Arnljot
authors.initials: A
authors.lastname: Tveit
authors.affiliation: Department of Biomedical Engineering and Center for Integrative Electrocardiology at Lund University (CIEL), Lund University, SE-22100 Lund, Sweden.
authors.forename: Leif
authors.initials: L
authors.lastname: Sörnmo
mesh_terms: D000200:Action Potentials; D000368:Aged; D000369:Aged, 80 and over; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D001283:Atrioventricular Node / Q000187:drug effects* / Q000503:physiopathology; D003198:Computer Simulation; D018592:Cross-Over Studies; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000627:therapeutic use*; D008875:Middle Aged; D008955:Models, Cardiovascular; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012032:Refractory Period, Electrophysiological; D016896:Treatment Outcome
chemical_list: D000889:Anti-Arrhythmia Agents; D008790:Metoprolol
keywords: Atrial fibrillation; Atrioventricular node; Beta-blocker; Functional refractory period; Metoprolol; Rate control; Refractory period; Ventricular rate