title: Exercise-induced alterations of signal-averaged electrocardiograms in marathon runners.
abstract: Late potentials have been shown to predict malignant ventricular arrhythmias and sudden cardiac death. To determine whether prolonged, strenuous activity is associated with the development of ventricular late potentials, signal-averaged electrocardiography was performed on 30 marathon runners before, immediately after, and during a recovery period at least 1 week after they had a 26.2-mile race. The filtered QRS duration decreased immediately after the marathon to 94.4 +/- 10.0 msec from baseline values of 97.3 +/- 10.1 msec (p less than 0.005). Root mean square energy in the terminal 40 msec of the QRS complex increased immediately after the race from 60.4 +/- 35.6 uV to 71.0 +/- 41.7 uV (P less than 0.5). The duration of signals less than 40 uV in the terminal QRS were not appreciably altered. At the 1-week follow-up study, all parameters closely approximated the baseline values. No runner had a late potential after running the race. The one runner with a late potential at baseline had normal parameters immediately after the race. We conclude that signal-averaged ECG parameters are improved after a marathon is run, and the risk of an arrhythmic sudden death in adult runners without organic heart disease would seem to be low.
authors.affiliation: Section of Cardiovascular Diseases, University of Kansas Medical Center, Kansas City 66103.
authors.forename: G S
authors.initials: GS
authors.lastname: Smith
authors.forename: J L
authors.initials: JL
authors.lastname: Vacek
authors.forename: D B
authors.initials: DB
authors.lastname: Wilson
authors.forename: J W
authors.initials: JW
authors.lastname: Hawkins
authors.forename: T A
authors.initials: TA
authors.lastname: Boyer
mesh_terms: D000328:Adult; D004452:Echocardiography; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance; D012420:Running