Cardiac fatigue in long-distance runners is associated with ventricular repolarization abnormalities.
BACKGROUND
Prolonged exercise can induce cardiac fatigue, which is characterized by biomarker release and impaired myocardial function. The impact on ventricular electrophysiology is largely unknown.


OBJECTIVE
The objective of this study was to examine changes in ventricular repolarization after a 30-km cross-country race in runners aged >or=55 years.


METHODS
Fifteen healthy participants (62 +/- 5 years) were assessed using biomarkers (N-terminal pro-brain natriuretic peptide [NT-proBNP], troponin T [TnT]), tissue Doppler echocardiography, and vectorcardiography at baseline, within 1 hour postrace and on days 1 and 6 postrace.


RESULTS
During the race, NT-proBNP increased from 42 ng/L (interquartile range 25-117) to 187 ng/L (113-464), and TnT increased from undetectable levels to 0.03 microg/L (0.015-0.05). Global strain (19.1% +/- 2.2%) decreased on day 1 (17.2% +/- 1.8%) and day 6 (17.9% +/- 1.5%; P <.01). QT(c) increased from 431 +/- 15 ms prerace to 445 +/- 22 ms postrace and 445 +/- 15 ms on day 1 (P <.05), mainly because of an increased T(peak-end) interval (prerace 108 +/- 13 ms, postrace 127 +/- 43 ms, day 1 127 +/- 43 ms; P <.05). Postrace, T(area) (baseline 75 +/- 26 microVs) peaked on day 1 (105 +/- 42 microVs) and remained high on day 6 (89 +/- 37 microVs; P <.05). Runners with higher baseline NT-proBNP developed greater impairment of myocardial velocities (rho = -0.68 to -0.54; P <.05) and a larger increase in T(area) (rho = 0.73; P <.01).


CONCLUSIONS
Cardiac fatigue induced by prolonged exertion is associated with sustained abnormalities in ventricular repolarization. Runners with higher baseline NT-proBNP are especially liable to such alterations of cardiac function.
Sahlén
Anders
A
Department of Cardiology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
Rubulis
Aigars
A
Winter
Reidar
R
Jacobsen
Per-Herman
PH
Ståhlberg
Marcus
M
Tornvall
Per
P
Bergfeldt
Lennart
L
Braunschweig
Frieder
F