Prevalence of Cardiac Abnormalities in Male and Female College Athletes when Exposed to Physiological and Thermal Stressors

Cardiovascular pre-participation screening of collegiate student athletes is inadequate. Physiological stress in the form of submaximal exercise and heat exposure can both alter cardiovascular function, possibly elucidating an abnormality via electrocardiogram (ECG). Purpose. To investigate prevalence of cardiac abnormalities in college athletes when exposed to physiological and thermal stress. Methods. Eleven participants (males n=5; females n=6; 20.5 ± 1.4 yrs; 167.8 ± 4.8 cm; 60.0 ± 4.5 kg; 56.1 ± 12.2 ml/kg/min) currently participating at the NCAA Division I level volunteered for this study. Participants completed two submaximal treadmill tests (70% of VO2 max) in varying environmental conditions: thermoneutral (24.8 ± 1.6˚C) and hyperthermic (38˚C) for 30 minutes. ECGs were recorded at five minute intervals. PR interval duration, ST segment elevation/depression, and R and S wave voltage amplitude were measured; ECGs were further analyzed for abnormalities. A repeated measures ANOVA was used to test the effects of condition by time.Results. No significant condition by time interactions were found for any variable (p>0.05). Significance across time manifested as a decreased PR interval (p<0.05), R wave voltage, (p<0.05), and S wave voltage (p<0.05). No main effects (p>0.05) were found for ECG abnormalities however; high occurrences of incomplete left bundle branch block (ILBBB) were found. Conclusion. Submaximal exercise in the hyperthermic condition did not significantly alter cardiovascular function in the parameters measured; however, the total number of ECG readings with abnormalities was higher in the hyperthermic condition compared to thermoneutral), most notable in incidences of ILBBB.