Hemodynamic Reactivity to Mental Stress in Patients With Coronary Artery Disease

Importance

The clinical significance of hemodynamic reactivity to mental stress in the population with coronary artery disease (CAD) is unclear.

Objective

To investigate the association between hemodynamic reactivity to mental stress and the risk of adverse cardiovascular events in patients with stable CAD.

Design, Setting, and Participants

This cohort study included individuals with stable CAD from 2 prospective studies from a university-based hospital network: the Mental Stress Ischemia Prognosis Study (MIPS) and the Myocardial Infarction and Mental Stress Study 2 (MIMS2). Participants were enrolled between June 2011 and March 2016 and followed up for a median of 6.0 (IQR, 5.6-6.0) years in MIPS and 4.6 (IQR, 3.8-5.3) years in MIMS2. Data were analyzed from December 1, 2022, to February 15, 2023.

Exposures

The rate-pressure product (RPP) was calculated as the mean systolic blood pressure times the mean heart rate at rest. Rate-pressure product reactivity was calculated as the maximum RPP during a standardized mental stress test minus the RPP at rest.

Main Outcomes and Measures

The primary outcome was a composite of cardiovascular death or nonfatal myocardial infarction. The secondary end point additionally included hospitalizations for heart failure.

Results

From the total of 938 individuals from the pooled cohort (mean [SD] age, 60.2 [10.1] years; 611 [65.1%] men), 631 participated in MIPS and 307 in MIMS2. A total of 373 individuals (39.8%) were Black, 519 (55.3%) were White, and 46 (4.9%) were of unknown race or ethnicity. The RPP increased by a mean (SD) of 77.1% (23.1%) during mental stress (mean [SD] absolute change, 5651 [2878]). For every SD decrease in RPP reactivity with mental stress, the adjusted hazard ratios for the primary and secondary end points were 1.30 (95% CI, 1.04-1.72) and 1.30 (95% CI, 1.06-1.56), respectively, in MIPS and 1.41 (95% CI, 1.06-1.97) and 1.21 (95% CI, 1.02-1.60), respectively, in MIMS2. In the pooled sample, when RPP reactivity to mental stress was added to a model including traditional clinical risk characteristics, model discrimination for adverse events improved (increase in C statistic of 5% for the primary end point; P = .009).

Conclusions and Relevance

In this cohort study of individuals with stable CAD, a blunted cardiovascular reactivity to mental stress was associated with adverse outcomes. Future studies are needed to assess the clinical utility of mental stress reactivity testing in this population.

Pain is reduced by transcutaneous cervical vagus nerve stimulation and correlated with cardiorespiratory variability measures in the context of opioid withdrawal

Over 100,000 individuals in the United States lost their lives secondary to drug overdose in 2021, with opioid use disorder (OUD) being a leading cause. Pain is an important component of opioid withdrawal, which can complicate recovery from OUD. This study's objectives were to assess the effects of transcutaneous cervical vagus nerve stimulation (tcVNS), a technique shown to reduce sympathetic arousal in other populations, on pain during acute opioid withdrawal and to study pain's relationships with objective cardiorespiratory markers. Twenty patients with OUD underwent opioid withdrawal while participating in a two-hour protocol. The protocol involved opioid cues to induce opioid craving and neutral conditions for control purposes. Adhering to a double-blind design, patients were randomly assigned to receive active tcVNS (n = 9) or sham stimulation (n = 11) throughout the protocol. At the beginning and end of the protocol, patients' pain levels were assessed using the numerical rating scale (0–10 scale) for pain (NRS Pain). During the protocol, electrocardiogram and respiratory effort signals were measured, from which heart rate variability (HRV) and respiration pattern variability (RPV) were extracted. Pre- to post- changes (denoted with a Δ) were computed for all measures. Δ NRS Pain scores were lower (P = 0.045) for the active group (mean ± standard deviation: −0.8 ± 2.4) compared to the sham group (0.9 ± 1.0). A positive correlation existed between Δ NRS pain scores and Δ RPV (Spearman's ρ = 0.46; P = 0.04). Following adjustment for device group, a negative correlation existed between Δ HRV and Δ NRS Pain (Spearman's ρ = −0.43; P = 0.04). This randomized, double-blind, sham-controlled pilot study provides the first evidence of tcVNS-induced reductions in pain in patients with OUD experiencing opioid withdrawal. This study also provides the first quantitative evidence of an association between breathing irregularity and pain. The correlations between changes in pain and changes in objective physiological markers add validity to the data. Given the clinical importance of reducing pain non-pharmacologically, the findings support the need for further investigation of tcVNS and wearable cardiorespiratory sensing for pain monitoring and management in patients with OUD.

Leveraging Accelerometry as a Prognostic Indicator for Increase in Opioid Withdrawal Symptoms

Treating opioid use disorder (OUD) is a significant healthcare challenge in the United States. Remaining abstinent from opioids is challenging for individuals with OUD due to withdrawal symptoms that include restlessness. However, to our knowledge, studies of acute withdrawal have not quantified restlessness using involuntary movements. We hypothesized that wearable accelerometry placed mid-sternum could be used to detect withdrawal-related restlessness in patients with OUD. To study this, 23 patients with OUD undergoing active withdrawal participated in a protocol involving wearable accelerometry, opioid cues to elicit craving, and non-invasive Vagal Nerve Stimulation (nVNS) to dampen withdrawal symptoms. Using accelerometry signals, we analyzed how movements correlated with changes in acute withdrawal severity, measured by the Clinical Opioid Withdrawal Scale (COWS). Our results revealed that patients demonstrating sinusoidal-i.e., predominantly single-frequency oscillation patterns in their motion almost exclusively demonstrated an increase in the COWS, and a strong relationship between the maximum power spectral density and increased withdrawal over time, measured by the COWS (R = 0.92, p = 0.029). Accelerometry may be used in an ambulatory setting to indicate the increased intensity of a patient's withdrawal symptoms, providing an objective, readily-measurable marker that may be captured ubiquitously.

Transcutaneous Cervical Vagus Nerve Stimulation Reduces Respiratory Variability in the Context of Opioid Withdrawal

Opioid withdrawal's physiological effects are a major impediment to recovery from opioid use disorder (OUD). Prior work has demonstrated that transcutaneous cervical vagus nerve stimulation (tcVNS) can counteract some of opioid withdrawal's physiological effects by reducing heart rate and perceived symptoms. The purpose of this study was to assess the effects of tcVNS on respiratory manifestations of opioid withdrawal - specifically, respiratory timings and their variability. Patients with OUD (N = 21) underwent acute opioid withdrawal over the course of a two-hour protocol. The protocol involved opioid cues to induce opioid craving and neutral conditions for control purposes. Patients were randomly assigned to receive double-blind active tcVNS (n = 10) or sham stimulation (n = 11) throughout the protocol. Respiratory effort and electrocardiogram-derived respiration signals were used to estimate inspiration time (T_i), expiration time (T_e), and respiration rate (RR), along with each measure's variability quantified via interquartile range (IQR). Comparing the active and sham groups, active tcVNS significantly reduced IQR(T_i) - a variability measure - compared to sham stimulation (p = .02). Relative to baseline, the active group's median change in IQR(T_i) was 500 ms less than the sham group's median change in IQR(T_i). Notably, IQR(T_i) was found to be positively associated with post-traumatic stress disorder symptoms in prior work. Therefore, a reduction in IQR(T_i) suggests that tcVNS downregulates the respiratory stress response associated with opioid withdrawal. Although further investigations are necessary, these results promisingly suggest that tcVNS - a non-pharmacologic, non-invasive, readily implemented neuromodulation approach - can serve as a novel therapy to mitigate opioid withdrawal symptoms.

Perceived Stress is Associated with Alzheimer's Disease Cerebrospinal Fluid Biomarkers in African Americans with Mild Cognitive Impairment

BACKGROUND

African Americans (AA) have a higher Alzheimer's disease (AD) prevalence and report more perceived stress than White Americans. The biological basis of the stress-AD link is unclear. This study investigates the connection between stress and AD biomarkers in a biracial cohort.

OBJECTIVE

Establish biomarker evidence for the observed association between stress and AD, especially in AA.

METHODS

A cross-sectional study (n = 364, 41.8% AA) administering cognitive tests and the perceived stress scale (PSS) questionnaire. A subset (n = 309) provided cerebrospinal fluid for measurement of Aβ42, Tau, Ptau, Tau/Aβ42 (TAR), and Ptau/Aβ42 (PTAR). Multivariate linear regression, including factors that confound racial differences in AD, was performed.

RESULTS

Higher PSS scores were associated with higher Ptau (β= 0.43, p = 0.01) and PTAR (β= 0.005, p = 0.03) in AA with impaired cognition (mild cognitive impairment).

CONCLUSION

Higher PSS scores were associated with Tau-related AD biomarker indices in AA/MCI, suggesting a potential biological connection for stress with AD and its racial disparity.

Circulating Progenitor Cells and Cognitive Impairment in Men and Women with Coronary Artery Disease

BACKGROUND

Circulating progenitor cells (CPC) have been associated with memory function and cognitive impairment in healthy adults. However, it is unclear whether such associations also exist in patients with coronary artery disease (CAD).

OBJECTIVE

To assess the association between CPCs and memory performance among individuals with CAD.

METHODS

We assessed cognitive function in 509 patients with CAD using the verbal and visual Memory subtests of the Wechsler memory scale-IV and the Trail Making Test parts A and B. CPCs were enumerated with flow cytometry as CD45med/CD34+ blood mononuclear cells, those co-expressing other epitopes representing populations enriched for hematopoietic and endothelial progenitors.

RESULTS

After adjusting for demographic and cardiovascular risk factors, lower number of endothelial progenitor cell counts were independently associated with lower visual and verbal memory scores (p for all < 0.05). There was a significant interaction in the magnitude of this association with race (p < 0.01), such that the association of verbal memory scores with endothelial progenitor subsets was present in Black but not in non-Black participants. No associations were present with the hematopoietic progenitor-enriched cells or with the Trail Making Tests.

CONCLUSION

Lower numbers of circulating endothelial progenitor cells are associated with cognitive impairment in patients with CAD, suggesting a protective effect of repair/regeneration processes in the maintenance of cognitive status. Impairment of verbal memory function was more strongly associated with lower CPC counts in Black compared to non-Black participants with CAD. Whether strategies designed to improve regenerative capacity will improve cognition needs further study.

Association Between Change in Circulating Progenitor Cells During Exercise Stress and Risk of Adverse Cardiovascular Events in Patients With Coronary Artery Disease

Importance

Stem and progenitor cells mobilize from the bone marrow in response to myocardial ischemia. However, the association between the change in circulating progenitor cell (CPC) counts and disease prognosis among patients with ischemia is unknown.

Objective

To investigate the association between the change in CPC counts during stress testing and the risk of adverse cardiovascular events in patients with stable coronary artery disease (CAD).

Design, Setting, and Participants

This prospective cohort study included a population-based sample of 454 patients with stable CAD who were recruited between June 1, 2011, and August 15, 2014, at Emory University-affiliated hospitals and followed up for 3 years. Data were analyzed from September 15, 2018, to October 15, 2018.

Exposures

Myocardial perfusion imaging with technetium Tc 99m sestamibi at rest and 30 to 60 minutes after conventional stress testing.

Main Outcomes and Measures

Circulating progenitor cells were enumerated with flow cytometry as CD34-expressing mononuclear cells (CD45med/CD34+), with additional quantification of subsets coexpressing the chemokine (C-X-C motif) receptor 4 (CD34+/CXCR4+). Changes in CPC counts were calculated as poststress minus resting CPC counts. Cox proportional hazards regression models were used to identify factors associated with the combined end point of cardiovascular death and myocardial infarction after adjusting for clinical covariates, including age, sex, race, smoking history, body mass index, and history of heart failure, hypertension, dyslipidemia, and diabetes.

Results

Of the 454 patients (mean [SD] age, 63 [9] years; 76% men) with stable CAD enrolled in the study, 142 (31.3%) had stress-induced ischemia and 312 (68.7%) did not, as measured by single-photon emission computed tomography. During stress testing, patients with stress-induced ischemia had a mean decrease of 20.2% (interquartile range [IQR], -45.3 to 5.5; P < .001) in their CD34+/CXCR4+ counts, and patients without stress-induced ischemia had a mean increase of 3.2% (IQR, -20.6 to 35.1; P < .001) in their CD34+/CXCR4+ counts. Twenty-four patients (5.2%) experienced adverse events. After adjustment, baseline CPC counts were associated with worse adverse outcomes, but this association was not present after stress-induced ischemia was included in the model. However, the change in CPC counts during exercise remained significantly associated with adverse events (hazard ratio, 2.59; 95% CI, 1.15-5.32, per 50% CD34+/CXCR4+ count decrease), even after adjustment for clinical variables and the presence of ischemia. The discrimination of risk factors associated with incident adverse events improved (increase in C statistic from 0.72 to 0.77; P = .003) with the addition of the change in CD34+/CXCR4+ counts to a model that included clinical characteristics, baseline CPC count, and ischemia.

Conclusions and Relevance

In this study of patients with CAD, a decrease in CPC counts during exercise is associated with a worse disease prognosis compared with the presence of stress-induced myocardial ischemia. Further studies are needed to evaluate whether strategies to improve CPC responses during exercise stress will be associated with improvements in the prognosis of patients with CAD.

Effects of Candesartan vs Lisinopril on Neurocognitive Function in Older Adults With Executive Mild Cognitive Impairment: A Randomized Clinical Trial

IMPORTANCE

Observational studies have suggested that angiotensin receptor blockers are associated with a unique cognitive protection. It is unclear if this is due to reduced blood pressure (BP) or angiotensin receptors type 1 blockade.

OBJECTIVE

To determine neurocognitive effects of candesartan vs lisinopril in older adults with mild cognitive impairment (MCI).

DESIGN, SETTING, AND PARTICIPANTS

This randomized clinical trial included participants aged 55 years or older with MCI and hypertension. Individuals were withdrawn from prior antihypertensive therapy and randomized in a 1 to 1 ratio to candesartan or lisinopril from June 2014 to December 2018. Participants underwent cognitive assessments at baseline and at 6 and 12 months. Brain magnetic resonance images were obtained at baseline and 12 months. This intent-to-treat study was double-blind and powered for a sample size accounting for 20% dropout. Data were analyzed from May to October 2019.

INTERVENTIONS

Escalating doses of oral candesartan (up to 32 mg) or lisinopril (up to 40 mg) once daily. Open-label antihypertensive drug treatments were added as needed to achieve BP less than 140/90 mm Hg.

MAIN OUTCOMES AND MEASURES

The primary outcome was executive function (measured using the Trail Making Test, Executive Abilities: Measures and Instruments for Neurobehavioral Evaluation and Research tool) and secondary outcomes were episodic memory (measured using the Hopkins Verbal Learning Test-Revised) and microvascular brain injury reflected by magnetic resonance images of white matter lesions.

RESULTS

Among 176 randomized participants (mean [SD] age, 66.0 [7.8] years; 101 [57.4%] women; 113 [64.2%] African American), 87 were assigned to candesartan and 89 were assigned to lisinopril. Among these, 141 participants completed the trial, including 77 in the candesartan group and 64 in the lisinopril group. Although the lisinopril vs candesartan groups achieved similar BP (12-month mean [SD] systolic BP: 130 [17] mm Hg vs 134 [20] mm Hg; P = .20; 12-month mean [SD] diastolic BP: 77 [10] mm Hg vs 78 [11] mm Hg; P = .52), candesartan was superior to lisinopril on the primary outcome of executive function measured by Trail Making Test Part B (effect size [ES] = -12.8 [95% CI, -22.5 to -3.1]) but not Executive Abilities: Measures and Instruments for Neurobehavioral Evaluation and Research score (ES = -0.03 [95% CI, -0.08 to 0.03]). Candesartan was also superior to lisinopril on the secondary outcome of Hopkins Verbal Learning Test-Revised delayed recall (ES = 0.4 [95% CI, 0.02 to 0.8]) and retention (ES = 5.1 [95% CI, 0.7 to 9.5]).

CONCLUSIONS AND RELEVANCE

These findings suggest that in older adults with MCI, 1-year treatment with candesartan had superior neurocognitive outcomes compared with lisinopril. These effects are likely independent of the BP-lowering effect of candesartan.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01984164.

Racial Disparity in Cerebrospinal Fluid Amyloid and Tau Biomarkers and Associated Cutoffs for Mild Cognitive Impairment

IMPORTANCE

Prior evidence suggests that racial differences exist in tau biomarkers in mild cognitive impairment (MCI) and Alzheimer disease (AD). Whether this reported disparity is associated with a differential level of neurodegeneration and disease stage or with underlying mechanisms separate from amyloid or tau is unclear.

OBJECTIVES

To compare cerebrospinal fluid (CSF) biomarkers in African American and white individuals with normal cognition and MCI, to estimate race-based cutoffs for these biomarkers that maximize diagnostic discrimination between normal cognition and MCI, and to study the association of demographic characteristics, cognitive performance, and common vascular risk factors with these differences.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study conducted from March 1, 2016, through January 31, 2019, included participants in the Brain Stress Hypertension and Aging Research Program cohort undergoing baseline assessment. Participants were 50 years or older and recruited from the Atlanta, Georgia, area.

EXPOSURES

Self-reported race and cognitive status categorized using modified Petersen criteria and clinical consensus diagnosis.

MAIN OUTCOMES AND MEASURES

Levels of β-amyloid 1-42 (Aβ1-42), tau, and phosphorylated tau 181 (pTau181), the ratio of tau or pTau181 to Aβ1-42, and hippocampal volume on magnetic resonance imaging of the brain.

RESULTS

Data from 362 study participants were analyzed (mean [SD] age, 65.6 [7.9] years), of whom 152 (42.0%) were African American, 230 (63.5%) were women, and 189 (52.2%) had MCI. After adjustment for demographic characteristics and cognitive performance, lower mean (SE) levels were observed in African American vs white individuals with MCI for tau (52.40 [5.90] vs 78.98 [5.02] pg/mL; P = .001) and pTau181 (15.42 [2.06] vs 25.24 [1.75] pg/mL; P = .001) and a lower pTau181 to Aβ1-42 ratio (0.07 [0.02] vs 0.14 [0.01]; P = .003). There were no racial differences in the normal cognition group or in hippocampal volumes in the MCI group. Cutoffs for CSF biomarkers were higher for Aβ1-42 in African American relative to white individuals (208 [95% CI, 126-321] vs 197 [95% CI, 183-245] pg/mL) and lower for tau (51 [95% CI, 31-59] vs 59 [95% CI, 56-92] pg/mL) and pTau181 (12 [95% CI, 12-19] vs 20 [95% CI, 12-27] pg/mL) levels. Cutoffs for the pTau181 to Aβ1-42 ratio were 0.05 (95% CI, 0.03-0.12) for African American participants and 0.05 (95% CI, 0.05-0.13) for white participants.

CONCLUSIONS AND RELEVANCE

This study found that African American individuals had lower levels of tau-based biomarkers that were not likely explained by the degree of disease stage or neurodegeneration reflected by hippocampal volumes. This study suggests that race is an important factor when interpreting CSF biomarkers, especially in the clinical diagnosis of prodromal AD. It appears that using the pTau181 to Aβ1-42 ratio may ameliorate these differences.

Neighborhood poverty and hemodynamic, neuroendocrine, and immune response to acute stress among patients with coronary artery disease

Living in neighborhoods characterized by poverty may act as a chronic stressor that results in physiological dysregulation of the sympathetic nervous system. No previous study has assessed neighborhood poverty with hemodynamic, neuroendocrine, and immune reactivity to stress. We used data from 632 patients with coronary artery disease. Patients' residential addresses were geocoded and merged with poverty data from the 2010 American Community Survey at the census-tract level. A z-transformation was calculated to classify census tracts (neighborhoods) as either having 'high' or 'low' poverty. Systolic blood pressure, diastolic blood pressure, heart rate, rate-pressure product, epinephrine, interleukin-6, and high-sensitivity C-reactive protein were measured before and after a public speaking stress task. Multilevel models were used for repeated measures and accounting for individuals nested within census tracts. Adjusted models included demographics, lifestyle and medical risk factors, and medication use. Another set of models included propensity scores weighted by the inverse probability of neighborhood status for sex, age, race, and individual-level income. The mean age was 63 years and 173 were women. After adjusting for potential confounders, participants living in high (vs. low) poverty neighborhoods had similar hemodynamic values at rest and lower values during mental stress for systolic blood pressure (157 mmHg vs. 161 mmHg; p = 0.07), heart rate (75 beats/min vs. 78 beats/min; p = 0.02) and rate-pressure product (11839 mmHg x beat/min vs 12579 mmHg x beat/min; p = 0.01). P-values for neighborhood poverty-by-time interactions were <0.05. Results were similar in the propensity weighted models. There were no significant differences in inflammatory and epinephrine responses to mental stress based on neighborhood poverty status. A blunted hemodynamic response to mental stress was observed among participants living in high poverty neighborhoods. Future studies should explore whether neighborhood poverty and blunted hemodynamic response to stress translate into differences in long-term cardiovascular outcomes.

Posttraumatic stress disorder is associated with enhanced interleukin-6 response to mental stress in subjects with a recent myocardial infarction

BACKGROUND

Posttraumatic Stress Disorder (PTSD) is prevalent among patients who survived an acute coronary syndrome, and is associated with adverse outcomes, but the mechanisms underlying these associations are unclear. Individuals with PTSD have enhanced sensitivity of the noradrenergic system to stress which may lead to immune activation. We hypothesized that survivors of a myocardial infarction (MI) who have PTSD would show an enhanced inflammatory response to acute psychological stress compared to those without PTSD.

METHODS

Individuals with a verified history of MI within 8 months and a clinical diagnosis of current PTSD underwent a mental stress speech task. Inflammatory biomarkers including interleukin-6 (IL-6), high-sensitivity C reactive protein (HsCRP), matrix metallopeptidase 9 (MMP-9), intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1 and monocyte chemoattractant protein (MCP)-1 were measured at rest and 90 min after mental stress.

RESULTS

Among 271 patients in the study (mean age 51 ± 7 years, 50% female, 60% African-American), the prevalence of PTSD was 12%. Mental stress resulted in a significant increase in IL-6, but the increase was more marked in patients with PTSD (126% increase) than those without (63% increase) (p = 0.001). MCP-1 showed a modest increase with stress which was similar in patients with PTSD (9% increase) and without PTSD (6% increase) (p = 0.35). CRP did not increase with stress in either group.

CONCLUSION

MI patients with current PTSD exhibit enhanced IL-6 response to psychosocial stress, suggesting a mechanistic link between PTSD and adverse cardiovascular outcomes as well as other diseases associated with inflammation.

Circulating Progenitor Cells and Racial Differences

RATIONALE

Blacks compared with whites have a greater risk of adverse cardiovascular outcomes. Impaired regenerative capacity, measured as lower levels of circulating progenitor cells (CPCs), is a novel determinant of adverse outcomes; however, little is known about racial differences in CPCs.

OBJECTIVE

To investigate the number of CPCs, PC-mobilizing factors, PC mobilization during acute myocardial infarction and the predictive value of CPC counts in blacks compared with whites.

METHODS AND RESULTS

CPCs were enumerated by flow cytometry as CD45med+ blood mononuclear cells expressing CD34+, CD133+, VEGF2R+, and CXCR4+ epitopes in 1747 subjects, mean age 58.4±13, 55% male, and 26% self-reported black. Patients presenting with acute myocardial infarction (n=91) were analyzed separately. Models were adjusted for relevant clinical variables. SDF-1α (stromal cell-derived factor-1α), VEGF (vascular endothelial growth factor), and MMP-9 (matrix metallopeptidase-9) levels were measured (n=561), and 623 patients were followed for median of 2.2 years for survival analysis. Blacks were younger, more often female, with a higher burden of cardiovascular risk, and lower CPC counts. Blacks had fewer CD34+ cells (-17.6%; [95% confidence interval (CI), -23.5% to -11.3%]; P<0.001), CD34+/CD133+ cells (-15.5%; [95% CI, -22.4% to -8.1%]; P<0.001), CD34+/CXCR4+ cells (-17.3%; [95% CI, -23.9% to -10.2%]; P<0.001), and CD34+/VEGF2R+ cells (-27.9%; [95% CI, -46.9% to -2.0%]; P=0.04) compared with whites. The association between lower CPC counts and black race was not affected by risk factors or cardiovascular disease. Results were validated in a separate cohort of 411 patients. Blacks with acute myocardial infarction had significantly fewer CPCs compared with whites ( P=0.02). Blacks had significantly lower plasma MMP-9 levels ( P<0.001) which attenuated the association between low CD34+ and black race by 19% (95% CI, 13%-33%). However, VEGF and SDF-1α levels were not significantly different between the races. Lower CD34+ counts were similarly predictive of mortality in blacks (hazard ratio, 2.83; [95% CI, 1.12-7.20]; P=0.03) and whites (hazard ratio, 1.79; [95% CI, 1.09-2.94]; P=0.02) without significant interaction.

CONCLUSIONS

Black subjects have lower levels of CPCs compared with whites which is partially dependent on lower circulating MMP-9 levels. Impaired regenerative capacity is predictive of adverse outcomes in blacks and may partly account for their increased risk of cardiovascular events.

Progenitor Cells and Clinical Outcomes in Patients With Acute Coronary Syndromes

RATIONALE

Circulating progenitor cells (CPCs) mobilize in response to ischemic injury, but their predictive value remains unknown in acute coronary syndrome (ACS).

OBJECTIVE

We aimed to investigate the number of CPCs in ACS compared with those with stable coronary artery disease (CAD), relationship between bone marrow PCs and CPCs, and whether CPC counts predict mortality in patients with ACS.

METHODS AND RESULTS

In 2028 patients, 346 had unstable angina, 183 had an acute myocardial infarction (AMI), and the remaining 1499 patients had stable CAD. Patients with ACS were followed for the primary end point of all-cause death. CPCs were enumerated by flow cytometry as mononuclear cells expressing a combination of CD34+, CD133+, vascular endothelial growth factor receptor 2+, or chemokine (C-X-C motif) receptor 4+. CPC counts were higher in subjects with AMI compared those with stable CAD even after adjustment for age, sex, race, body mass index, renal function, hypertension, diabetes mellitus, hyperlipidemia, and smoking; CD34+, CD34+/CD133+, CD34+/CXCR4+, and CD34+/VEGFR2+ CPC counts were 19%, 25%, 28%, and 142% higher in those with AMI, respectively, compared with stable CAD. There were strong correlations between the concentrations of CPCs and the PC counts in bone marrow aspirates in 20 patients with AMI. During a 2 (interquartile range, 1.31-2.86)-year follow-up period of 529 patients with ACS, 12.4% died. In Cox regression models adjusted for age, sex, body mass index, heart failure history, estimated glomerular filtration rate, and AMI, subjects with low CD34+ cell counts had a 2.46-fold (95% confidence interval, 1.18-5.13) increase in all-cause mortality, P=0.01. CD34+/CD133+ and CD34+/CXCR4+, but not CD34+/VEGFR2+ PC counts, had similar associations with mortality. Results were validated in a separate cohort of 238 patients with ACS.

CONCLUSIONS

CPC levels are significantly higher in patients after an AMI compared with those with stable CAD and reflect bone marrow PC content. Among patients with ACS, a lower number of hematopoietic-enriched CPCs are associated with a higher mortality.

Mental Stress-Induced-Myocardial Ischemia in Young Patients With Recent Myocardial Infarction: Sex Differences and Mechanisms

BACKGROUND

Mental stress-induced myocardial ischemia (MSIMI) is frequent in patients with coronary artery disease and is associated with worse prognosis. Young women with a previous myocardial infarction (MI), a group with unexplained higher mortality than men of comparable age, have shown elevated rates of MSIMI, but the mechanisms are unknown.

METHODS

We studied 306 patients (150 women and 156 men) ≤61 years of age who were hospitalized for MI in the previous 8 months and 112 community controls (58 women and 54 men) frequency matched for sex and age to the patients with MI. Endothelium-dependent flow-mediated dilation and microvascular reactivity (reactive hyperemia index) were measured at rest and 30 minutes after mental stress. The digital vasomotor response to mental stress was assessed using peripheral arterial tonometry. Patients received 99mTc-sestamibi myocardial perfusion imaging at rest, with mental (speech task) and conventional (exercise/pharmacological) stress.

RESULTS

The mean age of the sample was 50 years (range, 22-61). In the MI group but not among controls, women had a more adverse socioeconomic and psychosocial profile than men. There were no sex differences in cardiovascular risk factors, and among patients with MI, clinical severity tended to be lower in women. Women in both groups showed a higher peripheral arterial tonometry ratio during mental stress but a lower reactive hyperemia index after mental stress, indicating enhanced microvascular dysfunction after stress. There were no sex differences in flow-mediated dilation changes with mental stress. The rate of MSIMI was twice as high in women as in men (22% versus 11%, P=0.009), and ischemia with conventional stress was similarly elevated (31% versus 16%, P=0.002). Psychosocial and clinical risk factors did not explain sex differences in inducible ischemia. Although vascular responses to mental stress (peripheral arterial tonometry ratio and reactive hyperemia index) also did not explain sex differences in MSIMI, they were predictive of MSIMI in women only.

CONCLUSIONS

Young women after MI have a 2-fold likelihood of developing MSIMI compared with men and a similar increase in conventional stress ischemia. Microvascular dysfunction and peripheral vasoconstriction with mental stress are implicated in MSIMI among women but not among men, perhaps reflecting women's proclivity toward ischemia because of microcirculatory abnormalities.

Myocardial Ischemia and Mobilization of Circulating Progenitor Cells

Background

The response of progenitor cells (PCs) to transient myocardial ischemia in patients with coronary artery disease remains unknown. We aimed to investigate the PC response to exercise‐induced myocardial ischemia (ExMI) and compare it to flow mismatch during pharmacological stress testing.

Methods and Results

A total of 356 patients with stable coronary artery disease underwent 99mTc‐sestamibi myocardial perfusion imaging during exercise (69%) or pharmacological stress (31%). CD34⁺ and CD34⁺/chemokine (C‐X‐C motif) receptor 4 PCs were enumerated by flow cytometry. Change in PC count was compared between patients with and without myocardial ischemia using linear regression models. Vascular endothelial growth factor and stromal‐derived factor‐1α were quantified. Mean age was 63±9 years; 76% were men. The incidence of ExMI was 31% and 41% during exercise and pharmacological stress testing, respectively. Patients with ExMI had a significant decrease in CD34⁺/chemokine (C‐X‐C motif) receptor 4 (−18%, P=0.01) after stress that was inversely correlated with the magnitude of ischemia (r=−0.19, P=0.003). In contrast, patients without ExMI had an increase in CD34⁺/chemokine (C‐X‐C motif) receptor 4 (14.7%, P=0.02), and those undergoing pharmacological stress had no change. Plasma vascular endothelial growth factor levels increased (15%, P<0.001) in all patients undergoing exercise stress testing regardless of ischemia. However, the change in stromal‐derived factor‐1α level correlated inversely with the change in PC counts in those with ExMI (P=0.03), suggesting a greater decrease in PCs in those with a greater change in stromal‐derived factor‐1α level with exercise.

Conclusions

ExMI is associated with a significant decrease in circulating levels of CD34⁺/chemokine (C‐X‐C motif) receptor 4 PCs, likely attributable, at least in part, to stromal‐derived factor‐1α–mediated homing of PCs to the ischemic myocardium. The physiologic consequences of this uptake of PCs and their therapeutic implications need further investigation.

Inflammatory response to mental stress and mental stress induced myocardial ischemia

BACKGROUND

Mental stress-induced myocardial ischemia (MSIMI) is associated with increased risk of adverse cardiovascular outcomes, yet the underlying mechanisms are not well understood. We measured the inflammatory response to acute laboratory mental stress in patients with coronary artery disease (CAD) and its association with MSIMI. We hypothesized that patients with MSIMI would have a higher inflammatory response to mental stress in comparison to those without ischemia.

METHODS

Patients with stable CAD underwent 99mTc sestamibi myocardial perfusion imaging during mental stress testing using a public speaking stressor. MSIMI was determined as impaired myocardial perfusion using a 17-segment model. Inflammatory markers including interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), matrix metallopeptidase 9 (MMP-9) and high-sensitivity C reactive protein (hsCRP) were measured at rest and 90 min after mental stress. Results were validated in an independent sample of 228 post-myocardial infarction patients.

RESULTS

Of 607 patients analyzed in this study, (mean age 63 ± 9 years, 76% male), 99 (16.3%) developed MSIMI. Mental stress resulted in a significant increase in IL-6, MCP-1, and MMP-9 (all p <0.0001), but not hsCRP. However, the changes in these markers were similar in those with and without MSIMI. Neither resting levels of these biomarkers, nor their changes with mental stress were significantly associated with MSIMI. Results in the replication sample were similar.

CONCLUSION

Mental stress is associated with acute increases in several inflammatory markers. However, neither the baseline inflammatory status nor the magnitude of the inflammatory response to mental stress over 90 min were significantly associated with MSIMI.

Hemodynamic, catecholamine, vasomotor and vascular responses: Determinants of myocardial ischemia during mental stress

AIMS

Mental stress-induced myocardial ischemia (MSIMI) in patients with coronary artery disease (CAD) is associated with adverse cardiovascular outcomes. We aim to assess hemodynamic, neuro-hormonal, endothelial, vasomotor and vascular predictors of MSIMI.

METHODS AND RESULTS

We subjected 660 patients with stable CAD to 99mTc sestamibi myocardial perfusion imaging at rest, with mental (speech task) and with conventional (exercise/pharmacological) stress. Endothelium-dependent flow-mediated dilation (FMD), microvascular reactivity [reactive hyperemia index (RHI)] and arterial stiffness [pulse wave velocity (PWV)] were measured at rest and 30-min after mental stress. The digital microvascular vasomotor response during mental stress was assessed using peripheral arterial tonometry (PAT). A total of 106(16.1%) patients had MSIMI. Mental stress was accompanied by significant increases in rate-pressure-product (heart rate x systolic blood pressure; RPP), epinephrine levels and PWV, and significant decreases in FMD and PAT ratio denoting microvascular constriction. In comparison to those with no MSIMI, patients with MSIMI had higher hemodynamic and digital vasoconstrictive responses (p<0.05 for both), but did not differ in epinephrine, endothelial or macrovascular responses. Only presence of ischemia during conventional stress (OR of 7.1, 95%CI of 4.2, 11.9), high hemodynamic response (OR for RPP response≥vs<ROC cutoff of 1.8, 95%CI of 1.1, 2.8), and high digital vasoconstriction (OR for PAT ratio<vs≥ROC cutoff of 2.1, 95%CI of 1.3, 3.3) were independent predictors of MSIMI.

CONCLUSION

Ischemia during conventional stress testing and hemodynamic and vasoconstrictive responses to mental stress can help predict subjects with CAD at greater risk of developing MSIMI.

Association Between High-Sensitivity Cardiac Troponin Levels and Myocardial Ischemia During Mental Stress and Conventional Stress

OBJECTIVES

This study sought to investigate whether patients with mental stress-induced myocardial ischemia will have high resting and post-mental stress high-sensitivity cardiac troponin I (hs-cTnI).

BACKGROUND

Hs-cTnI is a marker of myocardial necrosis, and its elevated levels are associated with adverse outcomes. Hs-cTnI levels may increase with exercise in patients with coronary artery disease. Mental stress-induced myocardial ischemia is also linked to adverse outcomes.

METHODS

In this study, 587 patients with stable coronary artery disease underwent technetium Tc 99m sestamibi-single-photon emission tomography myocardial perfusion imaging during mental stress testing using a public speaking task and during conventional (pharmacological/exercise) stress testing as a control condition. Ischemia was defined as new/worsening impairment in myocardial perfusion using a 17-segment model.

RESULTS

The median hs-cTnI resting level was 4.3 (interquartile range [IQR]: 2.9 to 7.3) pg/ml. Overall, 16% and 34.8% of patients developed myocardial ischemia during mental and conventional stress, respectively. Compared with those without ischemia, median resting hs-cTnI levels were higher in patients who developed ischemia either during mental stress (5.9 [IQR: 3.9 to 8.3] pg/ml vs. 4.1 [IQR: 2.7 to 7.0] pg/ml; p < 0.001) or during conventional stress (5.4 [IQR: 3.9 to 9.3] pg/ml vs. 3.9 [IQR: 2.5 to 6.5] pg/ml; p < 0.001). Patients with high hs-cTnI (cutoff of 4.6 pg/ml for men and 3.9 pg/ml for women) had greater odds of developing mental (odds ratio [OR]: 2.4; 95% confidence interval [CI]: 1.5 to 3.9; p < 0.001) and conventional (OR: 2.4; 95% CI: 1.7 to 3.4; p < 0.001) stress-induced ischemia. Although there was a significant increase in 45-min post-treadmill exercise hs-cTnI levels in those who developed ischemia, there was no significant increase after mental or pharmacological stress test.

CONCLUSIONS

In patients with coronary artery disease, myocardial ischemia during either mental stress or conventional stress is associated with higher resting levels of hs-cTnI. This suggests that hs-cTnI elevation is an indicator of chronic ischemic burden experienced during everyday life. Whether elevated hs-cTnI levels are an indicator of adverse prognosis beyond inducible ischemia or whether it is amenable to intervention requires further investigation.

Telomere Shortening, Regenerative Capacity, and Cardiovascular Outcomes

RATIONALE

Leukocyte telomere length (LTL) is a biological marker of aging, and shorter LTL is associated with adverse cardiovascular outcomes. Reduced regenerative capacity has been proposed as a mechanism. Bone marrow-derived circulating progenitor cells are involved in tissue repair and regeneration.

OBJECTIVE

Main objective of this study was to examine the relationship between LTL and progenitor cells and their impact on adverse cardiovascular outcomes.

METHODS AND RESULTS

We measured LTL by quantitative polymerase chain reaction in 566 outpatients (age: 63±9 years; 76% men) with coronary artery disease. Circulating progenitor cells were enumerated by flow cytometry. After adjustment for age, sex, race, body mass index, smoking status, and previous myocardial infarction, a shorter LTL was associated with a lower CD34⁺ cell count: for each 10% shorter LTL, CD34⁺ levels were 5.2% lower (P<0.001). After adjustment for the aforementioned factors, both short LTL (<Q1) and low CD34+ levels (<Q1) predicted adverse cardiovascular outcomes (death, myocardial infarction, coronary revascularization, or cerebrovascular events) independently of each other, with a hazard ratio of 1.8 and 95% confidence interval of 1.1 to 2.0, and a hazard ratio of 2.1 and 95% confidence interval of 1.3 to 3.0, respectively, comparing Q1 to Q2-4. Patients who had both short LTL (<Q1) and low CD34+ cell count (<Q1) had the greatest risk of adverse outcomes (hazard ratio =3.5; 95% confidence interval, 1.7-7.1).

CONCLUSIONS

Although shorter LTL is associated with decreased regenerative capacity, both LTL and circulating progenitor cell levels are independent and additive predictors of adverse cardiovascular outcomes in coronary artery disease patients. Our results suggest that both biological aging and reduced regenerative capacity contribute to cardiovascular events, independent of conventional risk factors.