The present study was designed to evaluate the influence of age on the cardiovascular response during postural change. Ninety-one healthy male subjects with age from nineteen to eighty-three years were divided into three age groups: young (19-39 yrs.), middle (40-59 yrs.), old (60-83 yrs.). Circulatory function was examined by noninvasive method before, during and after five minutes of 70°head-up tilt. Hemodynamic parameters observed were heart rate, blood pressure (BP), cardiac output by impedance cardiograph and systolic time intervals (STI) which included total electromechanical systole (QS
2), left ventricular ejection time (LVET), pre-ejection period (PEP) and the ratio of pre-ejection period to left ventricular ejection time (PEP/LVET). QS
2 and LVET were corrected for heart rate according to the following regression equations obtained in thirty young healthy men.
QS
2=-1.5 HR+482, LVET=-1.1 HR+360. Stroke volume (SV), cardiac output (CO) and total peripheral vascular resistance (TPR) were calculated in their relative changes with tilt. After one minute of tilt in the young group, there were increases in heart rate (11beats/min.), diastolic BP (4.9mmHg) and TPR (47%) and decreases in SV (39%) and CO (29%). AS to STI, QS
2 and ETI shortened, PEP lengthened and PEP/LVET ratio increased with tilt. Analyzing these changes in hemodynamic parameters with aging, following results were obtained.
1) Heart rate was little influenced by aging both in the supine and head-up tilt position.
2) Significant reversed correlation between the rise in diastolic BP and age was observed both after one minute and five minutes of tilt. The old group showed less rise in diastolic BP and greater fall in systolic BP than the young group.
3) The changes in TPR, CO and SV decreased in the old group. Reversed correlation between the changes in these hemodynamic parameters and age was observed.
4) In the resting supine position, QS
2I and PEP lengthened and PEP/LVET ratio increased with aging, but ETI was little influenced. In the head-up tilt position, there was no significant difference of STI among the three groups.
5) With regards to the change in STI to tilting, increase in PEP and in PEP/LVET ratio diminished with aging. In the old group increase in PEP and in PEP/LVET ratio was significantly lower than in the young group.
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