Abstract 11015: Effect of Vitamin C on Cardiac Performance Following Live Firefighting
Sudden cardiac events are the major cause of line-of-duty deaths among firefighters, and occur disproportionately during firefighting activity. Live firefighting combines heavy physical work with severe heat stress and may last for several hours, thus a decrease in cardiac performance similar to prolonged endurance exercise events might be expected. “Cardiac fatigue” following prolonged endurance exercise may be partly due to oxidative stress. We investigated the effect of acute anti-oxidant supplementation (2 gr vitamin C (vitC) prior to 3 hour live firefighting exercise on ventricular performance, using a double blind, randomized design. Ventricular performance was evaluated before and immediately after a 3 hour live firefighting exercise using high definition ultrasound. Standard M-mode and B-mode imaging coupled with tissue Doppler imaging (TDI) at the mitral annulus was performed in 69 male firefighters randomly assigned to vitC ( n=34; age=28; BMI=26.9) or placebo (n=35; age=28 yrs; BMI=27.0). Subjects were weighed without clothing before and after firefighting to assess dehydration and liquids were allowed ad libitum during the 3 hour firefighting bout. Results are presented in table 1 (mean (SD)). Most measures of both systolic and diastolic ventricular performance decreased significantly after firefighting, except for TDI S velocity, but there were no significant differences between groups. There was a 3% loss of body weight, in both groups, but controlling for dehydration did not alter our findings. The * denotes a significant change from pre to post (p<.05).
Our data show that prolonged live firefighting produces decreases cardiac performance, which were not entirely explained by changes in loading conditions, similar to observations following prolonged endurance events. Since ventricular velocity in systole was unaltered, systolic performance appears to be mostly preserved. Our data suggest oxidative stress may not produce these changes.
- © 2010 by American Heart Association, Inc.