ABC | Volume 115, Nº1, July 2020

Original Article Assessing Dynamic Atrioventricular Conduction Time to RR-interval Coupling in Athletes and Sedentary Subjects Paulo Roberto Benchimol-Barbosa, 1, 2 Olivassé Nasario-Junior, 2 Jurandir Nadal 2 Hospital Universitário Pedro Ernesto, 1 Coordenação Clínica, Rio de Janeiro, RJ – Brazil Universidade Federal do Rio de Janeiro, Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia, 2 Rio de Janeiro, RJ – Brazil Mailing Address: Paulo Roberto Benchimol-Barbosa • Hospital Universitário Pedro Ernesto – Boulevard Vinte e Oito de setembro, 77, Gabinete da Direção Geral, Térreo. Postal Code 20551-030, Rio de Janeiro, RJ – Brazil E-mail: ecgar@yahoo.com , benchimol@globo.com Manuscript received April 30, 2019, revised manuscript July 02, 019, accepted August 01, 2019 DOI: https://doi.org/10.36660/abc.20190281 Abstract Background: Atrioventricular conduction time ( AVCT ) is influenced by autonomic input and subject to physiological remodeling. Objective: To evaluate beat-by-beat AVCT and RR-interval variability in athletes and healthy sedentary subjects. Methods: Twenty adults, including 10 healthy sedentary (Controls) and 10 elite long-distance runners (Athletes), age, weight and height-adjusted, underwent maximal metabolic equivalent (MET) assessment, and 15-min supine resting ECG recording seven days later. The interval between P-wave and R-wave peaks defined the AVCT . Mean (M) and standard deviation (SD) of consecutive RR-intervals (RR) and coupled AVCT were calculated, as well as regression lines of RR vs. AVCT (RR-AVCT) . Concordant AV conduction was defined as positive RR-AVCT slope and discordant otherwise. A multivariate linear regression model was developed to explain MET based on AVCT and RR-interval variability parameters. Significance-level: 5 %. Results: In Athletes, M-RR and SD-RR values were higher than in Controls, whereas M-AVCT and SD-AVCT were not. RR-AVCT slopes were, respectively, 0.038 ± 0.022 and 0.0034 ± 0.017 (p < 0.05). Using a cut-off value of 0.0044 (AUC 0.92 ± 0.07; p < 0.001), RR-AVCT slope showed 100% specificity and 80% sensitivity. In a multivariate model, SD-RR and RR-AVCT slope were independent explanatory variables of MET (F-ratio: 17.2; p < 0.001), showing 100% specificity and 90% sensitivity (AUC 0.99 ± 0.02; p < 0.001). Conclusion: In elite runners, AVCT to RR -interval dynamic coupling shows spontaneous discordant AV conduction, characterized by negative AVCT vs. RR -interval regression line slope. RR -intervals standard deviation and AVCT vs. RR -interval regression line slope are independent explanatory variables of MET (Arq Bras Cardiol. 2020; 115(1):71-77) Keywords: Athletes; Adults; Resistance Training; Physical Fitness; Ventricular Remodeling; Sedentarism; Electrocardiography/methods; Heart Ventricles; Ventricular Function. Introduction Cardiac adaptation secondary to physical fitness is reflected in mechanical, electrical and autonomic remodeling of the heart, as a consequence of repeated high-demand activities. Well-trained athletes often have slight ventricular mass gain, increased ECGwave amplitude, early repolarization, reduction of resting heart rate and increased heart rate variability, related to the conditioning status. 1-7 Particularly, most autonomic heart remodeling in well- conditioned athletes is a consequence of increased vagal tonus and reduced sympathetic stimulation over the sinus and the atrioventricular (AV) nodes. 1,6 Although increased vagal tonus may be straightforwardly detected by measuring the resting heart rate, to differentiate between increased parasympathetic activity over the sinus node and the AV node on surface ECG may not be that simple. Frequently, high-demand athletes have atrioventricular (AV) node remodeling, characterized by several degrees of AV conduction block, non-sinus low atrial or junctional rhythm and, more rarely, complete AV block. 8-10 Those AV conduction disturbances depend on physical conditioning status and are related not only to increased parasympathetic activity over the AV node, but also to secondary remodeling of the AV node fibers and cell-to-cell coupling. 11-13 Although AV conduction disturbances have been repeatedly documented in athletes, the dynamic AV conduction adaptation to the cardiac cycle in this population still needs clarification. In the general population, AV duration varies dynamically according to RR-interval duration, characterizing a concertina-like effect. However, in athletes, autonomic remodeling may influence dynamic AV conduction to RR- interval adaptation, leading to a distinct behavior of AV conduction, in a time-related response to RR-interval variation. 71