title: Presyncopal cardiac contractility and autonomic activity in young healthy males.
abstract: We investigated non-invasively cardiac contractility and autonomic nervous activity during presyncopal orthostatic stress induced in healthy humans. A graded orthostatic stress (GOS) paradigm, consisting of head-up tilt (HUT) combined with lower body negative pressure (LBNP) of increasing magnitude, was used to reach a presyncopal end-point in 15 healthy adults. Continuous beat-to-beat hemodynamic and autonomic parameters were recorded. From supine control (C1) to presyncope (PS), total peripheral resistance index (TPRI) decreased from 2300+/-500 to 1910+/-320 dyne*s*m(2)/cm(5) (p=0.004), index of contractility (IC) from 59+/-14 to 27+/-6 1000/s (p<0.0001), left ventricular working index (LVWI) from 5.2+/-1.3 vs. 3.6+/-0.6 mmHg*L/(min*m(2)) (p=0.0001) and acceleration index (ACI) from 65+/-18 vs. 54+/-15 100/s(2) (p=0.04). Low frequency variation of diastolic blood pressure (LF(nu)dBP) increased from 51+/-14 to 67+/-11 % (p=0.0006) and of systolic blood pressure (LF(nu)sBP) from 50+/-6 vs. 67+/-8 % (p<0.0001). High frequency variation of RR-interval (HF(ms(2))RRI) decreased from 385+/-320 to 38+/-43 ms(2) (p=0.001). From late GOS (G3) to PS, TPRI decreased from 2540+/-640 to 1910+/-320 dyne*s*m(2)/cm(5) (p=0.003), IC from 35+/-6 to 27+/-6 1000/s (p=0.003), LVWI from 4.6+/-0.9 to 3.6+/-0.6 mmHg*L/(min/m(2)) (p=0.003), LF(nu)sBP from 71+/-8 to 67+/-8 % (p=0.03), LF(mmHg(2))dBP from 6.6+/-4.0 to 4.8+/-2.9 mmHg(2) (p=0.0001), LF(mmHg(2))sBP from 9.7+/-7.8 to 7.4+/-4.8 mmHg(2) (p=0.01). HF(nu)RRI increased from 19+/-8 to 28+/-13 % (p=0.008). Myocardial contractility indices and parameters of sympathetic activity were reduced in the presyncopal state, while parasympathic activity was increased. This suggests a decrease in cardiac contractility during orthostatically induced presyncope in healthy subjects.
authors.affiliation: Institute of Physiology, Center of Physiological Medicine, Medical University Graz, Graz, Austria.
authors.forename: E K
authors.initials: EK
authors.lastname: Grasser
authors.forename: N
authors.initials: N
authors.lastname: Goswami
authors.forename: H
authors.initials: H
authors.lastname: Hinghofer-Szalkay
mesh_terms: D000328:Adult; D001794:Blood Pressure; D004244:Dizziness / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D009200:Myocardial Contraction; D010275:Parasympathetic Nervous System / Q000503:physiopathology*; D016683:Supine Position; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013575:Syncope / Q000503:physiopathology*; D018667:Tilt-Table Test; D013997:Time Factors; D014655:Vascular Resistance; D016277:Ventricular Function, Left