The influence of training status and parasympathetic blockade on the cardiac rate, rhythm and functional response to autonomic stress


Author: Lindsey Berthelsen1, Andrew J M Douglas2, Tony Dawkins3,4, Bryony Curry3,5, Daniel Phillips6, Abbas Zaidi7, Zaheer Yousef8, Mike Stembridge9, Craig D Steinback10

Affiliation: <sup>1</sup> University of Alberta, 3158, Edmonton, Alberta, Canada; lberthel@ualberta.ca.

<sup>2</sup> Cardiff Metropolitan University - Cyncoed Campus, 440486, Cardiff, Cardiff, United Kingdom of Great Britain and Northern Ireland; st20114281@outlook.cardiffmet.ac.uk.

<sup>3</sup> Cardiff Metropolitan University - Cyncoed Campus, 440486, Cardiff, Cardiff, United Kingdom of Great Britain and Northern Ireland.

<sup>4</sup> The University of British Columbia Okanagan, 97950, Kelowna, British Columbia, Canada; tony.dawkins@ubc.ca.

<sup>5</sup> The University of British Columbia Okanagan, 97950, Kelowna, British Columbia, Canada; bcurry1@mail.ubc.ca.

<sup>6</sup> University Hospital of Wales, 97609, Cardiff, Cardiff, United Kingdom of Great Britain and Northern Ireland; danielphillips@doctors.org.uk.

<sup>7</sup> University Hospital of Wales, 97609, Cardiff, Cardiff, United Kingdom of Great Britain and Northern Ireland; Abbas.Zaidi@wales.nhs.uk.

<sup>8</sup> University Hospital of Wales, 97609, Cardiff, Cardiff, United Kingdom of Great Britain and Northern Ireland; Zaheer.Yousef@wales.nhs.uk.

<sup>9</sup> Cardiff Metropolitan University, School of Sport, Cardiff, United Kingdom of Great Britain and Northern Ireland; mstembridge@cardiffmet.ac.uk.

<sup>10</sup> University of Alberta, Faculty of Physical Education and Recreation, Edmonton, Alberta, Canada; steinbac@ualberta.ca.
Conference/Journal: Appl Physiol Nutr Metab
Date published: 2023 Jan 12
Other:
  Special Notes: doi: 10.1139/apnm-2022-0340.   ,  Word Count: 250  
    Apnea (breath-holding) elicits co-activation of sympathetic and parasympathetic nervous systems, affecting cardiac control. In situations of autonomic co-activation (e.g., cold water immersion), cardiac arrhythmias are observed during apnea. Chronic endurance training reduces resting heart rate in part via elevation in parasympathetic tone, and has been identified as a risk factor for development of arrhythmias. However, few studies have investigated autonomic control of the heart in trained athletes during stress. Therefore, we determined whether heightened vagal tone resulting from endurance training promotes a higher incidence of arrhythmia during apnea. We assessed the heart rate, rhythm (ECG lead II), and cardiac inotropic (speckle-tracking echocardiography) response to apnea in 10 endurance trained and 7 untrained participants. Participants performed an apnea at rest and following sympathetic activation using post-exercise circulatory occlusion (PECO). All apneas were performed prior to (CON) and following vagal block using glycopyrrolate (GLY). Trained participants had lower heart rates at rest (p=0.03) and during apneas (p=0.009) under CON. At rest, 3 trained participants exhibited instances of junctional rhythm and 4 trained participants developed ectopy during CON apneas, whereas 3 untrained participants developed ectopic beats only with concurrent sympathetic activation (PECO). Following GLY, no arrhythmias were noted in either group. Vagal block also revealed increased cardiac chronotropy (heart rate) and inotropy (strain rate) during apnea, demonstrating a greater sympathetic influence in the absence of parasympathetic drive. Our results highlight that endurance athletes may be more susceptible to ectopy via elevated vagal tone, whereas untrained participants may only develop ectopy through autonomic conflict. .





PMID: 36634321 DOI: 10.1139/apnm-2022-0340