Effect of head-up tilting on systolic time intervals in normal young volunteers.
Systolic time intervals (STI) are sensitive indices of myocardial function. Passive tilting is a rapidly reversible and non-invasive method for inducing cardiovascular stress. The present work was conducted to study the effect of graded head-up tilt (HUT) on STI. 20 male medical students were subjected to 30 degrees, 60 degrees and 80 degrees HUT on a tilting table. ECG, phonocardiogram and carotid pulse were recorded simultaneously on Grass polygraph. Electromechanical systole (QS2), left ventricular ejection time (LVET), pre-ejection period (PEP), PEP/LEVT ratio, heart rate (HR) and corrected STI were determined immediately after and at 1, 2, 3, 4 and 5 min after each angle tilt. HUT produced a decrease in QS2 which was more pronounced at higher angle tilt. LVET decreased after 60 degrees and 80 degrees HUT. PEP and PEP/LVET ratio decreased after each angle tilt. These changes in STI can be explained on the basis of sympathetic stimulation-induced increase in the inotropic state of the heart.
Vijayalakshmi
S
S
Department of Physiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry.
Mohan
M
M
Thombre
D P
DP
Balakumar
B
B
Krishnamurthy
N
N
D000293:Adolescent; D000328:Adult; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology*; D012016:Reference Values; D013599:Systole / Q000502:physiology*