Date of Award

6-1998

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Nursing

Research Advisor

Kay F. Engelhardt

Committee

Raymond Ke Cheryl Stegbauer Peggy Tagg Veeser

Keywords

Cardiovascular rish factors, cardiac autonomic function, estrogen, heart, hypertension

Abstract

Minimal research has addressed effects of postmenopausal hormone replacement therapy (HRT) on heart rate variability (HRV), a measure of cardiovascular autonomic balance and a predictor of cardiac morbidity/mortality. Using an exploratory, pre-test/post-test design to describe HRV in postmenopausal women (PMW) before/after six weeks of HRT, twenty-four Black (n=15) and White (n=9) women, (mean age=55±4 years), were recruited from two primary care clinics (n=20) and one church population (n=4) in a large urban midsouth community. Cardiovascular risk factors for the sample included chronic illnesses of DM (n=8), HRT (n=11), both DM and HRT (n=4), smoking (n=9), non-exercise (n=11), and obesity quantified by sample mean BMI (mean=28±7.5). Twenty-four hour Holter monitoring and HRV analyses were done at first visit and following six weeks of oral self-administration of PremPro™ (estrogen: 0.625 mg; medroxyprogesterone acetate: 2.5 mg).

PMW demonstrated lower, but normal, HRV mean values than those for healthy female controls (n=118; age=35.6±11.8 years), Mean values were within normal limits established for the laboratory. Paired t-tests with significance at p? .10 demonstrated total group improvement for LowHertz (p=.06) and pNN50 (p=.10). HRV values improved for PMW with selected risk factors, consistently for values of TotalHertz and HighHertz, and, to a lesser extent, for values of PNN50 and rMSSD. Decreases in SDNN and SDANN were unexpected and merit further investigation.

White PMW showed no significant differences before/after HRT ; Black PMW demonstrated significant improvement in TotalHertz (p=.01), LowHertz (p=.03), HighHertz (p=.01), and rMSSD (p=.05. Correlational analyses of relationship for pre-/post-test HRV values to CV risk factors demonstrated significant (p?.10) relationships across HTN and years of menopause. Pre-/post-test significant differences were found for PMW with HTN for TotalHertz (p=.08), HighHertz (p=.04), pNN50 (p=.03), and rMSSD (p=.006), and PMW * 9 years menopausal for TotalHertz (p=.07), LowHertz (p=.01), pNN50 (p=.08), and SD (p=.07). Previous research findings suggested that PMW not on estrogen have a higher sympathetic mediation of autonomic function. Blacks and PMW < 55 years of age, following six-weeks of HRT, demonstrated a mediation in sympathetic/parasympathetic balance in post-test values. Because the study was exploratory with numerous analyses at p-value?.10, findings must be interpreted with caution.

DOI

10.21007/etd.cghs.1998.0235

Comments

Two year embargo expired June 2000

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