Systolic time intervals in pilots and non-pilots during 70 degree head-up tilt.

Nine highly experienced Indian fighter pilots in current flying practice and 11 healthy non-pilots underwent head-up tilt (HUT) to 70 degrees for 20 min. Heart rate and blood pressure response to tilt stress was similar in the two groups as was the contractile function of the left ventricle measured by systolic time intervals. The highest PEP/LVET ratio of 0.402 seen at the end of HUT was considerably lower than the values seen in other studies (5,11). This suggests that myocardial contractility of Indians adjusts better to tilt stress than that of western subjects not adapted to heat.