Faye S. Routledge

Improvements in heart rate variability with exercise therapy

Heart rate variability (HRV) is a noninvasive, practical and reproducible measure of autonomic nervous system function. A heart rate that is variable and responsive to demands is believed to bestow a survival advantage, whereas reduced HRV may be associated with poorer cardiovascular health and outcomes. In recent years, many researchers have investigated the prognostic implications of HRV in a variety of clinical populations. Evidence suggests that reduced HRV has prognostic significance for individuals with myocardial infarction, chronic heart failure, unstable angina and diabetes mellitus. Interventions to increase HRV, such as exercise therapy, have also been examined. The findings of the present review suggest that exercise therapy may improve HRV in myocardial infarction, chronic heart failure and revascularization patients by increasing vagal tone and decreasing sympathetic activity. One hypothesis is that a shift toward greater vagal modulation may positively affect the prognosis of these individuals. While the underlying mechanisms by which exercise training improves vagal modulation are speculative at present, angiotensin II and nitric oxide may be potential mediators.

Nondipping Blood Pressure Patterns among Individuals with Essential Hypertension: A Review of the Literature

Background: Researchers have discovered that blood pressure (BP) varies in a diurnal manner throughout a 24-hour period, being higher during the day and lower at night. Most people have a dipping BP pattern characterized by a nighttime BP that is 10–20% lower than their daytime BP. Individuals who experience a less than 10% reduction in nighttime BP are described as having a nondipping BP pattern. Although controversial, there is a growing body of evidence suggesting that a nondipping BP pattern is associated with a greater risk of target organ damage among individuals with essential hypertension. Aim: To review the literature on the most common factors associated with nondipping BP patterns among individuals with essential hypertension. Methods: CINAHL (1982-March 2006), PubMed (1950-March 2006) and Cochrane Library (1966-March 2006) databases were searched using the keywords: dipper, dipping, nondipper, nondipping, ambulatory blood pressure monitoring, ABPM, hypertension, essential hypertension, high blood pressure, blood pressure, nocturnal blood pressure, nighttime blood pressure, diurnal blood pressure, and blood pressure patterns. Published studies, abstracts, dissertations as well as the reference lists of retrieved articles were reviewed. Studies were included if they involved subjects with only treated or untreated essential hypertension or those with samples of both nomotensive and treated or untreated essential hypertensive individuals. Additionally, studies needed to evaluate 24-hour, daytime and nighttime BP patterns. Results: There is some evidence to suggest advanced age, African-American ethnicity, female sex, postmenopausal status, sodium sensitivity, sleep apnea, sleep quality, anger, hostility, depression, stress, social support, and socioeconomic status have an association with nondipping BP patterns. Conclusion: Knowledge of the potential factors associated with an altered nighttime BP pattern is of importance because it can help identify persons at risk for nondipping BP patterns and potential target organ damage. Furthermore, knowledge of these factors associated with a nondipping BP profile will lay the foundation for interventions to prevent/treat alterations in nighttime BP patterns.

Blood pressure dipping: Ethnicity, sleep quality, and sympathetic nervous system activity

BACKGROUND Blunted blood pressure (BP) dipping is an established predictor of adverse cardiovascular outcomes. Although blunted BP dipping is more common in African Americans than whites, the factors contributing to this ethnic difference are not well understood. This study examined the relationships of BP dipping to ethnicity, body mass index (BMI), sleep quality, and fall in sympathetic nervous system (SNS) activity during the sleep-period. METHODS On three occasions, 128 participants with untreated high clinic BP (130-159/85-99 mm Hg) underwent assessments of 24-h ambulatory BP (ABP), sleep quality, (evaluated by sleep interview, self-report, actigraphy) and sleep-period fall in sympathetic activity (measured by waking/sleep urinary catecholamine excretion). RESULTS Compared to whites (n = 72), African Americans (n = 56) exhibited higher sleep-period systolic (SBP) (P = 0.01) and diastolic BP (DBP) (P < 0.001), blunted SBP dipping (P = 0.01), greater BMI (P = 0.049), and poorer sleep quality (P = 0.02). SBP dipping was correlated with BMI (r = -0.32, P < 0.001), sleep quality (r = 0.30, P < 0.001), and sleep-period fall in sympathetic activity (r = 0.30, P < 0.001). Multiple regression analyses indicated that these three factors were independent determinants of sleep-period SBP dipping; ethnic differences in dipping were attenuated when controlling for these factors. CONCLUSIONS Blunted BP dipping was related to higher BMI, poorer sleep quality, and a lesser decline in sleep-period SNS activity. Although African-American ethnicity also was associated with blunted dipping compared to whites in unadjusted analyses, this ethnic difference was diminished when BMI, sleep quality, and sympathetic activity were taken into account.

Stress, menopausal status and nocturnal blood pressure dipping patterns among hypertensive women

BACKGROUND A less than 10% decline in blood pressure during the night is known as a nondipping blood pressure (BP) pattern. Nondipping BP has been shown to be associated with target organ damage and poorer cardiovascular outcomes. Additionally, some evidence suggests that hyper-tensive nondipping women are at greater risk for target organ damage than hypertensive nondipping men. OBJECTIVE To determine whether stress, demographics, menopausal status or sleep quality are associated with nondipping BP among hyperten-sive women. METHODS A cross-sectional study design was used to describe the rela-tionship between stress and dipping status among a sample of hypertensive women and to describe the sample by age, ethnicity, marital status, meno-pausal status, current medications and sleep quality. RESULTS The study sample consisted of 47 women (mean [+/- SD] age 57+/-13.9 years) with essential or office hypertension who underwent 24 h ambulatory BP monitoring, and completed stress and sleep quality measurements. Thirty-one women (66%) were classified as dippers and 16 (34%) were classified as nondippers. Nondippers were older (P=0.04), postmenopausal (P=0.003) and had lower stress scores (P=0.02) than their dipper counterparts. Postmenopausal status sig-nificantly predicted nondipping (OR 16; 95% CI 1.9 to 136.4). CONCLUSION These findings were of interest given that some women had a nondipping BP pattern and significantly lower stress scores. It is pos-sible that there are fundamentally different physiological mechanisms that explain this nondipping phenomenon. In the future, the identification of specific hemodynamic mechanisms associated with nondipping could potentially influence the choice of antihypertensive treatment regimens for nondipper hypertensive patients.

Nighttime Blood Pressure Dipping in Postmenopausal Women With Coronary Heart Disease

BACKGROUND Blunted nighttime blood pressure (BP) dipping is prognostic of cardiovascular morbidity and mortality. This relationship may be stronger among women than men. The present study hypothesized that coronary artery disease (CAD) and advancing age would be associated with reduced BP dipping in postmenopausal women. The effects of daytime physical activity and nighttime sleep quality on BP dipping were also examined. METHODS 54 postmenopausal women with CAD (≥50% occlusion of at least one major coronary vessel) and 48 age-matched (range 50-80 years) postmenopausal women without CAD (non-CAD) underwent 24-h ambulatory BP monitoring and actigraphic evaluations of daytime physical activity and nighttime sleep efficiency. RESULTS Women with CAD evidenced higher nighttime systolic BP (SBP) (P = 0.05) and blunted SBP dipping (P = 0.017), blunted diastolic BP (DBP) dipping (P = 0.047), and blunted pulse pressure dipping (P = 0.01), compared to non-CAD women. Multivariable regression models showed that the presence of CAD, age, daytime physical activity, and nighttime sleep efficiency were independently related to the magnitude of SBP dipping, together accounting for 25% of its variability. DBP dipping showed similar associations. CONCLUSIONS For postmenopausal women, the presence of CAD and advancing age are accompanied by blunted nighttime BP dipping, which may increase the risk of adverse cardiovascular events. Lifestyle changes that increase daytime physical activity and improve nighttime sleep quality may help improve cardiovascular risk by enhancing nighttime BP dipping.

Ambulatory Impedance Cardiography in Hypertension: A Validation Study

The management of hypertension is improved by knowledge of the hemodynamics underlying blood pressure. Impedance Cardiography (ICG) provides data on a range of hemodynamic variables that affect blood pressure. However, ICG captures only fixed descriptions of hemodynamic characteristics. Improvements in ambulatory technology have led to the development of the Ambulatory Impedance Monitor (AIM) which records hemodynamic data during the activities of daily living. The purpose of this study was to evaluate the sensitivity of the AIM to detect hemodynamic changes associated with postural shift in persons with hypertension. Using a repeated measures cross-over design, sitting and standing hemodynamic measures were taken in seventeen persons with hypertension while wearing the AIM-BpTRU system designed for standard office use and the AIM-Spacelabs system designed for ambulatory monitoring. Both AIM-blood pressure monitoring systems detected significant changes from sitting to standing posture in heart rate (p = 0.03), stroke volume (p = 0.002), left ventricular ejection time (p < 0.001), systemic vascular resistance (p = 0.03) and diastolic blood pressure (p < 0.001). Additionally, both systems generated measures of cardiac function that were positively correlated (p < 0.001) and not significantly different (p > 0.05). Our findings support previous work and demonstrate that the AIM provides valid and reliable estimates of cardiac function in persons with hypertension.

Coping Effectively With Heart Failure (COPE-HF): Design and Rationale of a Telephone-Based Coping Skills Intervention

BACKGROUND Coping Effectively with Heart Failure (COPE-HF) is an ongoing randomized clinical trial funded by the National Institutes of Health to evaluate if a coping skills training (CST) intervention will result in improved health status and quality of life as well as reduced mortality and hospitalizations compared with a heart failure education (HFE) intervention. METHODS AND RESULTS Two hundred heart failure (HF) patients recruited from the Duke University Medical Center and the University of North Carolina Hospital system will be randomized to a CST intervention (16 weekly 30-minute telephone counseling sessions including motivational interviewing and individually tailored cognitive behavioral therapy) or to an HFE intervention (16 weekly 30-minute telephone sessions including education and symptom monitoring). Primary outcomes will include postintervention effects on HF biomarkers (B-type natriuretic peptide, ejection fraction) and quality of life, as well as long-term clinical outcomes (hospitalizations and death). Secondary analyses will include an evaluation of treatment effects across subpopulations, and potential mechanisms by which CST may improve clinical outcomes. CONCLUSIONS COPE-HF is a proof-of-concept study that should provide important insights into the health benefits of a CST intervention designed to enhance HF self-management, improve health behaviors, and reduce psychologic distress.

The influence of coronary artery bypass graft harvest site on women's pain, functional status, and health services utilization throughout the first post-operative year: A longitudinal study

BACKGROUND Coronary artery bypass graft surgery is a commonly performed procedure aimed at managing coronary symptoms and prolonging life. Researchers have typically examined morbidity and mortality outcomes of predominantly male populations. Less is known about the influence of graft harvest site on recovery outcomes such as surgery-related pain, functional status, and health services utilization, especially in women. OBJECTIVES We aimed to examine the relationships between coronary artery bypass graft harvest site (saphenous vein, internal mammary arteries or both) and surgery-related pain, functional status, health services use at 6 weeks, 12 weeks and 12 months post-operatively. DESIGN Longitudinal extension survey following participation in a clinical trial. SETTING Ten Canadian centres. PARTICIPANTS Women (222) who participated in the Womens Recovery from Sternotomy Trial, underwent coronary artery bypass graft surgery with or without heart valve surgery, and completed the 12-month follow-up interview. METHODS Harvest site data were collected by health record audit at the time of hospital discharge. Surgery-related pain, functional status, pain medication use and health services use data were collected by standardized interview over the telephone at 6 weeks, 12 weeks and 12 months post-operatively. Surgery-related pain and functional status were measured using the short Health Assessment Questionnaire. Health services use was measured by questionnaire and recorded as reported by the participants. RESULTS Surgery-related pain, functional disability and health services use decreased over the first post-operative year. Participants who had left internal mammary artery grafts were more likely to have surgery-related pain (Adjusted Odds Ratio (AOR)=2.79; 95% Confidence Interval (CI) 1.40-5.70) and use pain medication (AOR=4.32; 95% CI 1.44-12.91) than those who had saphenous vein grafts. Conversely, participants who had saphenous vein grafts reported significantly more functional disability (AOR=2.63; 95% CI 1.16-6.25) over 12 months post-surgery than those with left internal mammary artery grafts. Participants who had pain over the course of follow-up were more likely to visit their family physician or nurse practitioner (p=0.017), visit another type of provider (i.e., naturopath or chiropractor, p=0.004), or use any health care service (p<0.0001). CONCLUSIONS Following coronary artery bypass graft surgery, women who had left internal mammary artery grafts reported more pain and health services use while those who had saphenous vein grafts were more functionally disabled. Women who reported surgery-related pain also used more health services.

Endothelial function in postmenopausal women with nighttime systolic hypertension

ObjectiveHypertension becomes more prevalent in women during their postmenopausal years. Nighttime systolic blood pressure (SBP) is especially predictive of adverse cardiac events, and the relationship between rising nighttime SBP and cardiovascular risk increases more rapidly in women compared with men. The reasons for the prognostic significance of nighttime SBP are not completely known but may involve vascular endothelial dysfunction. The purposes of this study were to examine the relationship between nighttime SBP and endothelial function, as assessed by brachial artery flow-mediated dilation (FMD), and to determine whether postmenopausal women with nighttime hypertension (SBP ≥120 mm Hg) evidenced greater endothelial dysfunction compared with women with normal nighttime SBP. MethodsOne hundred postmenopausal women (mean [SD] age, 65.8 [7.5] y; mean [SD] body mass index, 28.3 [4.7] kg/m2; hypertension, 47%; coronary artery disease, 51%; mean [SD] clinic SBP, 137 [17] mm Hg; mean [SD] clinic diastolic blood pressure, 67 [11] mm Hg; nighttime hypertension, 34 women) underwent 24-hour ambulatory blood pressure monitoring, actigraphy, and brachial artery FMD assessment. ResultsMultivariate regression models showed that higher nighttime SBP and larger baseline artery diameter were inversely related to FMD. Nighttime SBP and baseline artery diameter accounted for 23% of the variance in FMD. After adjustment for baseline artery diameter, women with nighttime hypertension had lower mean (SD) FMD than women with normal nighttime SBP (2.95% [0.65%] vs 5.52% [0.46%], P = 0.002). ConclusionsNighttime hypertension is associated with reduced endothelial function in postmenopausal women. Research examining the therapeutic benefits of nighttime hypertension treatment on endothelial function and future cardiovascular risk in postmenopausal women is warranted.

Sex Differences in the Endothelial Function of Untreated Hypertension

J Clin Hypertens (Greenwich). 2012;14:228–235. ©2012 Wiley Periodicals, Inc.