title: Baroreflex function during 45-degree passive head-up tilt before and after long-term thiazide therapy in the elderly with systolic systemic hypertension.
abstract: The ratio of the 30th to the 15th cardiac cycle duration on an electrocardiogram (30:15 ratio) immediately after active standing from the supine position has been used as one of the markers of baroreflex function. A ratio of < or = 1.0 has been suggested to indicate baroreflex dysfunction. Blood pressure (BP) changes were measured and the 30:15 ratio was calculated after standing and during 45-degree passive head-up tilt from the supine position in 10 nondiabetic men (mean age +/- SE 70.1 +/- 1.05 years, and BP < 150/90 mm Hg). After tilt the decrease in systolic BP (from 132 +/- 4.8 to 117 +/- 6.3 mm Hg; p < 0.001) appeared to be larger than that after standing (from 132 +/- 4.6 to 123 +/- 5.8 mm Hg; p < 0.01), whereas the 30:15 ratios were 0.965 +/- 0.006 and 0.970 +/- 0.014, respectively, which suggested baroreflex dysfunction. Although the mean of the 2 ratios did not differ, the variance appeared to be less during tilting than after standing. Thus, the 45-degree passive head-up tilt appeared to be a better and more uniform inducer of orthostatic stress than active standing. Therefore, 45-degree head-up tilt was used in a group of 10 nondiabetic male patients (aged 70 +/- 1.46 years) with isolated systolic hypertension (systolic BP > 160 mm Hg, diastolic BP of < 90 mm Hg) to assess their baroreflex function. Upon tilting, their systolic BP decreased from 190 +/- 5.5 to 179 +/- 5.8 mm Hg (p < 0.05) and their 30:15 ratio was 0.985 +/- 0.011.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, Veterans Administration Medical Center, Syracuse, New York 13210.
authors.forename: S
authors.initials: S
authors.lastname: Vardan
authors.forename: N E
authors.initials: NE
authors.lastname: Hill
authors.forename: K G
authors.initials: KG
authors.lastname: Mehrotra
authors.forename: S
authors.initials: S
authors.lastname: Mookherjee
authors.forename: H
authors.initials: H
authors.lastname: Smulyan
mesh_terms: D000368:Aged; D017704:Baroreflex / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D006852:Hydrochlorothiazide / Q000627:therapeutic use*; D006973:Hypertension / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D011187:Posture; D013599:Systole; D013997:Time Factors
chemical_list: D006852:Hydrochlorothiazide