Deriving heart period variability from blood pressure waveforms

International standards for calculating heart period variability (HPV) from a series of R-wave intervals (R-R) in an electrocardiographic (ECG) recording have been widely accepted. It is possible, and potentially useful in various settings, to use systolic blood pressure waveform intervals to estimate HPV, but the validity of HPV derived from blood pressure (BP) waveforms has not been established. To test the reliability between BP- and ECG-derived HPV indexes, we evaluated data from 234 healthy adults in four studies of HPV reactivity to stress. Study conditions included resting baseline, arithmetic, Stroop test, speech presentation, and orthostatic tilt. Continuous ECG and BP recordings were sampled at a rate of 500 Hz, scored by the same methods, and used to calculate heart rate and time- and frequency-domain measures of HPV. Overall, reliability between the two methods was very high for computing heart rate and HPV indexes. High-frequency HPV indexes were somewhat less reliably computed. In conclusion, in healthy adults, with the use of appropriate methods, BP waveforms can produce reliable indexes of HPV.

Low arterial compliance in young African-American males

Hypertension remains a common public health challenge because of its prevalence and increase in co-morbid cardiovascular diseases. Black males have disproportionate pathophysiological consequences of hypertension compared with any other group in the United States. Alterations in arterial wall compliance and autonomic function often precede the onset of disease. Accordingly, our purpose was to investigate whether differences exist in arterial compliance and autonomic function between young, healthy African-American males without evidence of hypertension and age- and gender-matched non-African-American males. All procedures were carried out noninvasively following rest. Arterial compliance was calculated as the integrated area starting at the well-defined nadir of the incisura of the dicrotic notch to the end of diastole of the radial artery pulse wave. Power spectral analysis of heart rate and blood pressure variability provided distributions representative of parasympathetic and sympathetic modulations and sympathovagal balance. Baroreflex sensitivity (BRS) was calculated using the sequence method. Thirty-two African-American and twenty-nine non-African-American males were comparable in anthropometrics and negative family history of hypertension. t-Tests revealed lower arterial compliance (5.8 +/- 2.4 vs. 8.6 +/- 4.0 mmHg. s; P = 0.0017), parasympathetic modulation (8.9 +/- 1.1 vs. 9.7 +/- 1.1 ln ms2; P = 0.0063), and BRS (13.7 +/- 7.3 vs. 21.1 +/- 8.5 ms/mmHg; P = 0.0007) and higher sympathovagal balance (2.9 +/- 3.2 vs. 1.5 +/- 1.1; P = 0.03) in the African-American group. In summary, differences exist in arterial compliance and autonomic balance in African-American males. These alterations may be antecedent markers of disease and valuable in the detection of degenerative cardiovascular processes in individuals at risk.

Evaluation of blood pressure and baroreflex sensitivity by radial artery tonometry versus finger arteriolar photoplethysmography

BACKGROUND

Published normative data of noninvasive blood pressures (BPs) and autonomic modulations have been primarily derived from the finger arteriole using the Finapres (Ohmeda Co., Englewood, CO), a device that is no longer manufactured. Currently, beat-to-beat BP are obtained from the radial artery using the Colin tonometer.

METHODS

We compared BP and autonomic parameters in a crossover design between the two devices in 29 subjects during seated rest and a 0.1-Hz breathing protocol. In addition, we tested whether finger arteriolar BP differences were due to pressure changes exerted by the radial tonometer.

RESULTS

Uniformly, BP measured at the radial artery were significantly higher than those from the finger arteriole. Radial BP (106 +/- 19.5 mm Hg) were higher than finger arteriolar BP (95.8 +/- 13.7 mm Hg) (P <.005). Tonometric baroreflex sensitivity (BRS) (24.0 +/- 18 msec/mm Hg) was higher compared to photoplethysmographic BRS (12.0 +/- 7.7 msec/mm Hg; P <.0003). Systolic BP (radial artery) (115 +/- 25 mm Hg) were higher compared to finger arteriolar BP (97.7 +/- 19 mm Hg; P <.0025) during breathing, as was BRS (25.9 +/- 11.6 msec/mm Hg v 21.5 +/- 11.6 msec/mm Hg; P <.05). Differences in the low frequency systolic BP (LF(SBP)), representative of sympathetic vasomotor modulation, between the two methods, whether absolute, normalized, or log-transformed were not observed.

CONCLUSIONS

There were no differences in arteriolar BP values in the presence or absence of radial artery tonometric pressure. These findings indicate that differences exist in systolic BP and BRS using the tonometer (radial artery) versus the Finapres (Ohmeda Co.) (finger arteriole). Furthermore, these differences are not due to pressure exerted by the radial artery tonometer that supplies blood to the finger arteriole.

Effects of women's stress-elicited physiological activity and chronic anxiety on fetal heart rate

This study examined the effects of pregnant women's acute stress reactivity and chronic anxiety on fetal heart rate (HR). Thirty-two healthy third trimester pregnant women were instrumented to monitor continuous electrocardiography, blood pressure, respiration, and fetal HR. Subjects completed the trait anxiety subscale of the State Trait Anxiety Index, then rested quietly for a 5-minute baseline period, followed by a 5-minute Stroop color-word matching task and a 5-minute recovery period. Fetal HR changes during women's recovery from a stressful task were associated with the women's concurrently collected HR and blood pressure changes (r =.63, p <.05). Fetal HR changes during recovery, as well as during women's exposure to the Stroop task, were correlated with their mothers' trait anxiety scores (r =.39, p <.05 and r = -.52, p <.01, respectively). Finally, a combination of measures of women's cardiovascular activity during recovery and trait anxiety scores accounted for two thirds of the variance in fetal HR changes during the same recovery period (r =.69, p <.001). The results from this study link changes in fetal behavior with acute changes in women's cardiovascular activity after psychological stress and women's anxiety status. This indicates that variations in women's emotion-based physiological activity can affect the fetus and may be centrally important to fetal development.

Claims about religious involvement and health outcomes

Claims about religion, spirituality, and health have recently appeared with increasing frequency, in both the popular media and professional journals. These claims have asserted that there are a great many studies in the literature that have examined relations between religious involvement and health outcomes and that the majority of them have shown that religious people are healthier. We examined the validity of these claims in two ways: (a) To determine the percentage of articles in the literature that were potentially relevant to such a claim, we identified all English-language articles with published abstracts identified by a Medline search using the search term religion in the year 2000, and (b) to examine the quality of the data in articles cited as providing supportfor such a claim, we examined all articles in the area of cardiovascular disease and hypertension cited by two comprehensive reviews of the literature. Of the 266 articles published in the year 2000 and identified by the Medline search, only 17% were relevant to claims of health benefits associated with religious involvement. About half of the articles cited in the comprehensive reviews were irrelevant to these claims. Of those that actually were relevant, many either had significant methodological flaws or were misrepresented, leaving only afew articles that could truly be described as demonstrating beneficial effects of religious involvement. We conclude that there is little empirical basis for assertions that religious involvement or activity is associated with beneficial health outcomes.

Temporal stability of acute stress-induced changes in leukocyte subsets and cellular adhesion molecules in older adults

This study investigated the temporal stability of enumerative immune and catecholamine responses to acute psychosocial stress in 67 Alzheimer's caregivers ages 56-82 years (45 women and 22 men) who were required to prepare and deliver two 3-min speeches on three occasions at 2-week and 6-week intervals. All leukocyte subsets and adhesion molecules (CD62L and CD11a) changed significantly from rest to postspeak at each of the three testing sessions (p's <.0005). Responses showed moderate to high temporal stability across baseline and absolute task values (r's =.65-.96). Reliability was predictably lower for both forms of change scores (r's = -.16-.64). The level of temporal stability achieved is comparable to that seen previously in younger adults, indicating that acute psychosocial stress produces reliable changes in circulating leukocytes and cell adhesion molecules in older adults.

Relation between depression after coronary artery bypass surgery and 12-month outcome: a prospective study

BACKGROUND

The association of depression with cardiac events has been investigated mainly in community cohorts, in patients undergoing catheterisation, or in patients who have had myocardial infarction. We have assessed the effect of depression on outcomes after coronary artery bypass graft (CABG) surgery.

METHODS

In a prospective study, we followed up for 1 year 207 men and 102 women, who had undergone coronary artery bypass graft surgery. We assessed depression with a structured psychiatric interview (diagnostic interview schedule) and a questionnaire (Beck depression inventory) before discharge. Cardiac events included angina or heart failure that needed admission to hospital, myocardial infarction, cardiac arrest, percutaneous transluminal coronary angioplasty, repeat CABG, and cardiac mortality. Non-cardiac events consisted of all other reasons for mortality or readmission.

FINDINGS

63 patients (20%) met modified diagnostic statistical manual IV criteria for major depressive disorder. At 12 months, 17 (27%) of these patients had a cardiac event compared with 25 of 246 (10%) who were not depressed (p<0.0008). Five variables had significant univariate associations with cardiac events: sex, living alone, low ejection fraction (<0.35), length of hospital stay, and depression. In a Cox proportional-hazard model with these five and two other variables of cardiac severity, major depressive disorder (risk ratio 2.3 [95% CI 1.17-4.56]), low ejection fraction (2.3 [1.07-5.03]), and female sex (2.4 [1.24-4.44]) were associated with adverse outcomes. Depression did not predict deaths or admissions for non-cardiac events.

INTERPRETATION

Depression is an important independent risk factor for cardiac events after CABG surgery.

Vagal rebound and recovery from psychological stress

OBJECTIVE

To characterize cardiovascular recovery and examine the possible relationship of vagal activity and reflexes to risk for heart disease.

METHODS

Subjects performed cold pressor and mental arithmetic tasks. Heart rate, heart period variability, and pre-ejection period were obtained for 1 minute before, during, and after each task (Experiment 1). In the second experiment, subjects performed a Stroop color-word task and a mental arithmetic task. Heart rate, heart period variability, blood pressure, and baroreflex sensitivity were obtained during the 5-minute baseline, task, and recovery periods (Experiment 2).

RESULTS

In Experiment 1, heart rate during recovery was lower than baseline despite continued pre-ejection period shortening, whereas recovery heart period variability was higher than baseline. In Experiment 2, blood pressure increased throughout the session. However, recovery heart rate after mental arithmetic was lower than baseline heart rate, and heart period variability was higher during both recovery periods than during baseline. Vagal rebound, a sharp increase in variability in the first minute of recovery, was reduced in men in Experiment 1 and in individuals with a family history of cardiovascular disease in Experiment 2 and was associated with degree of change in baroreflex sensitivity between task and rest.

CONCLUSIONS

Cardiovascular recovery from stress is associated with increased vagal modulation despite residual sympathetic activation. Vagal rebound may be involved in mechanisms resetting the baroreflex sensitivity at the onset and offset of stress. Diminished vagal rebound during recovery from stress is associated with standard risk factors for cardiovascular disease. The results support an association between attenuated vagal reflexes and risk for cardiovascular disease.

Enhanced stress reactivity in paediatric anxiety disorders: implications for future cardiovascular health

The aim was to clarify the developmental nature of associations between psychiatric illness and risk for cardiovascular disease by investigating differences in cardiac functioning between youth with anxiety disorders and healthy controls. Twenty-two children meeting DSM-IV criteria for either separation anxiety disorder, overanxious disorder, panic disorder/panic attacks, or social phobia and 12 healthy controls underwent continuous electrocardiogram and respiration rate monitoring during a 15 min baseline period and 15 min of exposure to 5% CO(2). Heart rate (HR) and high frequency heart rate variability (HRV), a non-invasive measure of cardiac parasympathetic control, were calculated. Youth with anxiety disorders had higher and less fluctuating HR during baseline. Data also suggested that probands showed diminished overall changes in HRV during baseline and CO(2) inhalation relative to controls. However, as respiration rate affects HRV, these findings were confounded by changes in respiration elicited by CO(2) inhalation. The data suggest that youth with anxiety disorders experience an elevated and less fluctuating HR in the face of a novel situation, possibly due to a failure to appropriately modulate HRV. In adults, sustained elevations in HR in conjunction with deficient vagal modulation predicts risk for future cardiovascular disease. As such, the current data suggest that the presence of an anxiety disorder may identify youth who exhibit autonomic profiles that place them at risk for cardiac disease.

Hostility, gender, and cardiac autonomic control

OBJECTIVE

Although considerable evidence implicates hostility in the development of coronary artery disease (CAD), the pathogenic mechanisms remain poorly understood. We have developed a psychophysiological model that holds that altered autonomic nervous system function links psychological traits with CAD outcomes. In laboratory studies, stressors reduce high-frequency (HF) heart period variability, an index of cardiac vagal modulation. With ambulatory electrocardiographic recording, we demonstrated in a predominantly male sample that hostility was inversely associated with HF power, but only during waking hours. These findings are consistent with the hypothesis that hostile individuals experience multiple stressful interpersonal transactions each day, resulting in overall lower HF power during the day but not at night.

METHODS

To further evaluate this hypothesis, we screened 96 subjects using the Cook-Medley Hostility Scale and selected 15 men and 15 women representing a wide distribution of hostility. These subjects were studied in a laboratory session assessing reactivity to psychological and orthostatic challenges with continuous electrocardiographic, blood pressure, and respiration monitoring. We predicted that for men and women, hostility would be inversely related to reductions in HF power in response to challenge.

RESULTS

In response to mental stressors, all measures of heart period variability change were inversely related to hostility as predicted. No such relationships were found for responses to tilt. The data suggested a possible effect of gender on these relationships.

CONCLUSIONS

These data add to the growing body of evidence showing that hostility influences vagal modulation of the cardiovascular system and suggest that altered autonomic control is a pathogenic mechanism linking hostility and CAD.

Physiologic responses to cognitive challenge during pregnancy: effects of task and repeat testing

Physiological responses to stress during pregnancy are believed to influence birth outcomes. Researchers have studied pregnant women in laboratory stressor paradigms to investigate these associations, yet normative data on cardiovascular and respiratory responses to laboratory challenge during pregnancy are not yet established. To begin to establish such normative data, this study examined the effects of task and repeat stressor exposure on reactivity in third-trimester pregnant women. Thirty-one healthy pregnant women (mean age=27 years; range 18-36) between the 33rd and 39th week of pregnancy, were instrumented for continuous electrocardiography, blood pressure (BP), and respiration data. Subjects rested quietly for a 5-min baseline and then performed both a mental arithmetic stressor and a Stroop color-word-matching task, each 5 min in length and each followed by a 5-min recovery period. The order of the tasks was counterbalanced. After each 5-min period, subjects rated the period on a 10-point stress scale. Averaged across task type and challenge period, systolic and diastolic BP and respiration rate increased significantly in response to cognitive challenge, but heart rate (HR) did not. When data were examined for task and period effects, the following results emerged: the Stroop task elicited significantly greater systolic BP and HR reactivity than the arithmetic task, yet subjects rated the arithmetic task as more stressful. Averaged across task type, subjects showed greater systolic BP reactivity during the second challenge period compared to the first. Finally, women's BP tended to drift upward and did not return to baseline during the first recovery period. These findings indicate that averaging data across tasks and periods can obscure the time course of response patterns that may be important in the study of associations between maternal stress and perinatal development, as well as in other research on reactivity to repeat stress exposure.

Heart rate variability in depressive and anxiety disorders

Loss of normal autonomic nervous system control of heart rate and rhythm is an important risk factor for adverse cardiovascular events. After myocardial infarction, reduction in beat-to-beat heart rate variability, a measure of cardiac autonomic innervation by the brain, is a strong predictor of death. With loss of vagal innervation, as is noted in patients with severe neuropathy and in heart transplant recipients, there is loss of heart rate variability. It is speculated that decreased parasympathetic innervation exposes the heart to unopposed stimulation by sympathetic nerves. Individuals with high hostility scores and patients with anxiety or depressive disorders have low heart rate variability and may be at increased risk for cardiovascular death associated with coronary heart disease and arrhythmias. After myocardial infarction, depressed patients exhibit higher mortality rates compared with nondepressed patients. Men with "phobic anxiety," a construct that appears to overlap substantially with panic disorder, also have higher rates of sudden cardiac death and coronary artery disease than control populations. The reduction in autonomic nervous system control to the heart may be one link between psychopathology and heart disease. Although tricyclic antidepressants reduce heart rate variability, at least one study has suggested that, in patients with panic disorder, treatment with the selective serotonin reuptake inhibitor paroxetine normalizes heart rate variability. Hence there is potential for the treatment of psychiatric disorders to affect positively the development and course of cardiovascular disease.

Cerebral activation, hostility, and cardiovascular control during mental stress

OBJECTIVE

Hostility has been established as a risk factor for the development of coronary artery disease. Putatively pathogenic hemodynamic and neuroendocrine responses to psychological stressors are associated with hostility, but the cerebral effects of hostility and their relationship to these responses are unknown. This pilot study examined cardiovascular and cerebral blood flow responses to stress in subjects with high and low levels of trait hostility.

METHODS

Regional cerebral blood flow was measured by single-photon emission computed tomography (SPECT) during a control condition and in response to mental arithmetic stress.

RESULTS

The stressor was associated with reduced blood flow to the prefrontal cortex, and this reduction was greater in the high hostility subjects.

CONCLUSION

These preliminary findings support the hypothesis that mental arithmetic stress is associated with reduced blood flow to prefrontal cortex, and that trait hostility is associated with a stronger effect.

Changes in autonomic regulation with age: implications for psychopharmacologic treatments in children and adolescents

Developmental changes in the cardiovascular system could have an impact on risks associated with psychopharmacological interventions. Children may be more vulnerable to adverse cardiac events due to immaturity in autonomic control of the heart. These changes are incompletely understood and are characterized in this study. A consecutive series of 70 boys, aged 6-14 years, was recruited. Developmental variation in the autonomic nervous system was evaluated by assessing heart period variability (HPV), pulse, and blood pressure in response to orthostasis. Increased age correlated significantly with greater heart rate and diastolic blood pressure response to orthostasis. HPV at rest and in response to tilt did not significantly correlate with age. Boys with family histories of hypertension had a significantly greater blood pressure response to orthostasis. These findings suggest that developmental age-related changes in the sympathetic nervous system, as reflected by changes of pulse and blood pressure response to tilt, occur across this age range. Parasympathetic changes, as reflected by HPV, do not. In light of these findings, more research is needed on children's and adolescents' relative cardiac risk with psychotropic medications as opposed to adults'.

Maternal stress responses and anxiety during pregnancy: effects on fetal heart rate

This study examined the effect of an acute maternal stress response and anxiety on fetal heart rate. Seventeen healthy, 3rd-trimester pregnant women (mean age = 26 +/- 6 years) were instrumented for continuous electrocardiography, blood pressure (BP), respiration, and fetal heart rate (HR). Subjects completed the state anxiety subscale of the State Trait Personality Inventory (STPI), then rested quietly in a semirecumbent position for a 5-min baseline period, followed by either a 5-min arithmetic or Stroop color-word task. Over the entire 5-min stress period and when averaged across all subjects, the stressors led to significant increases in maternal systolic BP and respiratory rate but changes in maternal HR, diastolic BP, and fetal HR were not significant. However, when subjects were dichotomized into groups that had above or below average anxiety scores [ANX(+) and ANX(-)], both groups had similar respiration rate increases to the stressors, but the BP and fetal heart rate (FHR) responses were significantly different. Women in the ANX(-) group had significantly greater BP responses compared to women in the ANX(+) group whereas the fetuses of ANX(+) women showed significant HR increases and the fetuses of ANX(-) women exhibited nonsignificant decreases. These findings suggest that women's acute emotional reactivity during pregnancy can influence fetal HR patterns and that a stress-induced increase in maternal BP is not the primary signal by which a women's stress response is transduced to her fetus. The results are consistent with the hypothesis that maternal psychological variables may shape the neurobehavioral development of the fetus.

Mixed-effects models in psychophysiology

The current methodological policy in Psychophysiology stipulates that repeated-measures designs be analyzed using either multivariate analysis of variance (ANOVA) or repeated-measures ANOVA with the Greenhouse-Geisser or Huynh-Feldt correction. Both techniques lead to appropriate type I error probabilities under general assumptions about the variance-covariance matrix of the data. This report introduces mixed-effects models as an alternative procedure for the analysis of repeated-measures data in Psychophysiology. Mixed-effects models have many advantages over the traditional methods: They handle missing data more effectively and are more efficient, parsimonious, and flexible. We described mixed-effects modeling and illustrated its applicability with a simple example.

Effects of desipramine on autonomic input to the heart

OBJECTIVE

To examine the impact of age on the effects of desipramine (DMI) on autonomic input to the heart.

METHOD

Twenty-four-hour electrocardiograms were obtained from 42 subjects, aged 7 to 66 years, while off and on DMI. To obtain measures of autonomic input to the heart, heart rate variability was assessed via spectral analysis of RR interval variability.

RESULTS

DMI treatment was associated with a significant increase in 24-hour mean heart rate and significant decreases in RR interval variability in all spectral bands, including in the high-frequency band, which provides a measure of parasympathetic input to the heart. RR interval variability was greater in younger individuals both off and on DMI.

CONCLUSIONS

DMI treatment was associated with a marked decline in RR interval variability, indicating that DMI affects autonomic input to the heart. Specifically, DMI reduced parasympathetic input, which, in theory, may increase vulnerability to arrhythmias. However, the magnitude of DMI's impact on RR interval variability did not vary with age.