Influence of coronary artery disease risk factors on baroreflex sensitivity in the elderly

Abstract

In this study, we assessed whether baroreflex sensitivity (BRS) is influenced by risk factors of cardiovascular disease. Subjects of this study were 95 elderly people (40 males and 55 females; mean age +/- SD, 66.6+/-1.6 years) who underwent a medical check-up. BRS was determined as the gain of transfer function in baroreflex arc by spectral analysis of mean blood pressure and R-R interval variabilities in low-frequency band (0.04-0.15 Hz). Gender-related differences in BRS and relationships between BRS and various risk factors of cardiovascular disease were investigated. The value of BRS was significantly higher in males [10.7+/-3.7 (SD) ms/mmHg] than in females [9.0+/-4.0 ms/mmHg, p< 0.05]. However, this gender-related difference disappeared when other variables were taken into account in the multivariate model. Multiple regression analyses showed independent inverse relationships between BRS and heart rate [b=-0.016+/-0.004 (SE) bpm, beta=-0.39], and between BRS and platelet count [b=-0.002+/-0.001 x 103/ micro l, beta=-0.22]. Our results indicated that BRS is inversely related to platelet count in the elderly population. The precise mechanism of this correlation is unknown, but platelet factors released from platelet aggregates can potentially influence vascular function and modify BRS, or there is a common underlying determinant responsible for the covariation.

Determinants of baroreflex sensitivity in health and disease:

“…Results from previous studies suggest that in vivo platelet activation is related to platelet count and is enhanced in patients with coronary artery disease [4,25]. A significant number of subjects in the study by Yasumasu et al [29] were hyperlipidemic (63 %), hypertensive (48 %), and diabetic (11 %). Angina (5 subjects) and a previous myocardial infarction (one subject) were also noted.…”

“…The study by Yasumasu et al [29] demonstrates an association between platelet count and BRS, but cannot determine causality. Although the inverse relationship between platelet count and BRS may involve an effect of platelets on BRS, platelet count may also simply be a marker of an unidentified determinant of BRS.…”

“…The authors speculate that factors released from ag- gregating platelets may decrease BRS in subjects with high platelet counts [29]. How can this hypothesis be tested?…”

“…A large multi-center prospective trial (ATRAMI) recently demonstrated that measures of BRS provide independent prognostic value in predicting total cardiac and arrhythmic mortality after myocardial infarction [13,14]. Attempts are now underway to identify optimal predictors of decreased BRS in healthy subjects [7,8,11] and in patients prior to myocardial infarction or heart failure [9,12].The goal of the study by Yasumasu and colleagues reported in this issue of Clinical Autonomic Research [29], was to identify risk factors of cardiovascular disease that are associated with decreased BRS. The study population was restricted to elderly subjects (40 men and 55 women, 65-69 years old) to take advantage of the prevalence of risk factors in this population and to eliminate the established and possibly confounding effect of age on BRS.…”

“…The goal of the study by Yasumasu and colleagues reported in this issue of Clinical Autonomic Research [29], was to identify risk factors of cardiovascular disease that are associated with decreased BRS. The study population was restricted to elderly subjects (40 men and 55 women, 65-69 years old) to take advantage of the prevalence of risk factors in this population and to eliminate the established and possibly confounding effect of age on BRS.…”