The Role of the Myocardial Microvasculature in Mental Stress-Induced Myocardial Ischemia

Myocardial blood flow mechanism of mental stress-induced myocardial ischemia in women with ANOCA

Mental stress-induced myocardial ischemia (MSIMI) is linked to a 2-fold increase in cardiovascular events, but its underlying myocardial blood flow (MBF) mechanisms remain underexplored. Using nitrogen-13-ammonia cardiac positron emission tomography-computed tomography (PET-CT) assessing myocardial perfusion defect and MBF under resting, mental stress (MS), adenosine stress (AS) conditions, angina with no obstructive coronary artery disease (ANOCA) women showed a significantly higher prevalence of MSIMI compared to age-matched healthy controls (36/84 vs. 1/42, p < 0.001). The MBFAS and rate-pressure product-corrected MBFMS were consistently lower, especially in the left anterior descending artery territory, in participants with increased perfusion defect scores under MS. The lowest values of restricted coronary flow reserve and corrected MBFMS in participants of ANOCA&MSIMI+ group indicated that impaired coronary microvascular function and mismatch between myocardial blood supply and demand together constitute the pathogenic mechanism of MSIMI in ANOCA population. These findings deepen our understanding of the pathophysiological mechanisms of MSIMI and confirm the long-standing hypothesis of the involvement of impaired coronary microvascular function.

Mental Stress and Cardiovascular Health-Part I

Epidemiological studies have shown that a substantial proportion of acute coronary events occur in individuals who lack the traditional high-risk cardiovascular (CV) profile. Mental stress is an emerging risk and prognostic factor for coronary artery disease and stroke, independently of conventional risk factors. It is associated with an increased rate of CV events. Acute mental stress may develop as a result of anger, fear, or job strain, as well as consequence of earthquakes or hurricanes. Chronic stress may develop as a result of long-term or repetitive stress exposure, such as job-related stress, low socioeconomic status, financial problems, depression, and type A and type D personality. While the response to acute mental stress may result in acute coronary events, the relationship of chronic stress with increased risk of coronary artery disease (CAD) is mainly due to acceleration of atherosclerosis. Emotionally stressful stimuli are processed by a network of cortical and subcortical brain regions, including the prefrontal cortex, insula, amygdala, hypothalamus, and hippocampus. This system is involved in the interpretation of relevance of environmental stimuli, according to individual’s memory, past experience, and current context. The brain transduces the cognitive process of emotional stimuli into hemodynamic, neuroendocrine, and immune changes, called fight or flight response, through the autonomic nervous system and the hypothalamic–pituitary–adrenal axis. These changes may induce transient myocardial ischemia, defined as mental stress-induced myocardial ischemia (MSIMI) in patients with and without significant coronary obstruction. The clinical consequences may be angina, myocardial infarction, arrhythmias, and left ventricular dysfunction. Although MSIMI is associated with a substantial increase in CV mortality, it is usually underestimated because it arises without pain in most cases. MSIMI occurs at lower levels of cardiac work than exercise-induced ischemia, suggesting that the impairment of myocardial blood flow is mainly due to paradoxical coronary vasoconstriction and microvascular dysfunction.

Psychological factors of suspect coronary microvascular dysfunction in patients undergoing SPECT imaging

BACKGROUND

Patients with myocardial ischemia in the absence of obstructive coronary artery disease (CAD) often experience anginal complaints and are at risk of cardiac events. Stress-related psychological factors and acute negative emotions might play a role in these patients with suspect coronary microvascular dysfunction (CMD).

METHODS AND RESULTS

295 Patients (66.9 ± 8.7 years, 46% women) undergoing myocardial perfusion single-photon-emission computed tomography (MPI-SPECT), were divided as follows: (1) a non-ischemic reference group (n = 136); (2) patients without inducible ischemia, but with a history of CAD (n = 62); (3) ischemia and documented CAD (n = 52); and (4) ischemia and suspect CMD (n = 45). These four groups were compared with regard to psychological factors and acute emotions. Results revealed no differences between the groups in psychological factors (all P > .646, all effect sizes d < .015). State sadness was higher for patients with suspect CMD (16%) versus the other groups (P = .029). The groups did not differ in the association of psychological factors or emotions with anginal complaints (all P values > .448).

CONCLUSION

Suspect CMD was not associated with more negative psychological factors compared to other groups. State sadness was significantly higher for patients with suspect CMD, whereas no differences in state anxiety and other psychological factors were found.

Everyday Discrimination and Mental Stress-Induced Myocardial Ischemia

OBJECTIVE

Mental stress-induced myocardial ischemia (MSIMI), a transient myocardial ischemic response to mental stress, is associated with poorer outcomes among patients with coronary heart disease and is more likely to occur among women. However, predictors of MSIMI are not well explored. The current study investigated the association between experiences of everyday discrimination and MSIMI among patients with recent myocardial ischemia and contrasted the results with conventional stress-induced myocardial ischemia (CSIMI). We examined sex differences in associations.

METHODS

We studied 295 post-MI patients (145 women, 150 men). Provocation of myocardial ischemia with mental stress (speech task) and conventional stress (exercise or pharmacologic) was assessed by myocardial perfusion imaging. Frequency of exposure to everyday discrimination was assessed via questionnaire using the Everyday Discrimination Scale (EDS).

RESULTS

The mean age was 51 years in both women and men, and the EDS score ranged from 10 to 38 (mean [standard deviation] = 17 [6] years). After multivariable analysis, each standard deviation increase in the EDS score (more frequent exposure) was associated with an increased odds of MSIMI (odds ratio [OR] = 1.57 [1.10-2.23]). The EDS score was not associated with CSIMI (OR = 0.86 [0.64-1.17]). Women demonstrated a twofold increase (OR = 1.96 [1.13-3.38], p = .02) in the adjusted odds of MSIMI, with each standard deviation increase in the EDS score compared with a 1.4-fold increase (OR = 1.40 [0.80-2.44], p = .24) among men; however, interaction was not statistically significant.

CONCLUSIONS

Among post-MI patients, everyday discrimination was positively associated with occurrence of MSIMI, but not with CSIMI; associations were more pronounced among women.

The Impact of War-Related Stress on Coronary Artery Disease Severity in War Survivors: A SYNTAX Study

Background: Due to the strong relationship between stress and heart disease, particularly acute myocardial infarction (MI), this study investigated the complexity of coronary artery disease (CAD) among Syrian refugee patients referred to Jordan University Hospital and its relation to war-related stressors. Methods: This is a retrospective study that utilized the SYNTAX I score in order to evaluate all Syrian refugees that underwent coronary artery catheterization at Jordan University Hospital during the period between May of 2014 and December of 2017. Results: There was a significant association between war-related stressors and high SYNTAX score (SX score), thus indicating a higher complexity of CAD in Syrian war survivors with higher stress scores. The strongest war-related correlation was observed with crossing green-lines, in which Syrian refugee patients who had crossed such lines had significantly higher SYNTAX scores. Regression analysis demonstrated that war stressors were positive predictors of increased SYNTAX scores even when adjusted for conventional CAD risk factors. Surprisingly, none of the CAD risk factors were significantly associated with SYNTAX score. Conclusion: Our findings suggest that exposure to multiple war-related stressors may increase the complexity and severity of CAD in Syrian war survivors. Thus, special attention, efforts, and resources should be allocated to screen for such vulnerable patients in order to provide them with the appropriate healthcare.

Research progress regarding the diagnosis and treatment of mental stress-induced myocardial ischemia

Myocardial ischemia resulting from psychological stress [mental stress-induced myocardial ischemia (MSIMI)] refers to the condition wherein psychosocial and psychological stimulations cause myocardial ischemia in patients with coronary heart disease, which is different from drug-induced myocardial ischemia. Therefore, this condition often escapes diagnosis, portends clinical risk, and affects the quality of life of MSIMI survivors. MSIMI is closely related to the poor prognosis of cardiovascular diseases, especially in young women, according to recent randomized, controlled trials (RCTs) on MSIMI. These RCTs involved different sample sizes, interventional measures, and detection techniques. Moreover, differences exist regarding the prevalence rate, distribution characteristics, possible pathogenesis, and clinical significance. Nevertheless, currently, the diagnostic criteria, pathogenesis, and treatment of MSIMI are still in the clinical exploration stage. Hence, considering recent RCTs, this paper summarizes the research status of MSIMI from the aspects of pathogenesis, diagnosis, and treatment strategies to provide a theoretical basis for the follow-up diagnostic methods and treatment guidelines for MSIMI.

Heart rate variability, the dynamic nature of the retinal microvasculature and cardiac stress: providing insight into the brain-retina-heart link: the SABPA study

BACKGROUND AND AIMS

Decreased heart-rate-variability (HRV) indicates increased sympathetic nervous system (SNS) activity and modulation with a shift in the sympatho-vagal balance towards SNS predominance. Increased SNS activity may precede volume-loading hypertension, contribute to increases in cardiac troponin T (cTnT), endothelial dysfunction and small vessel disease. Therefore, we investigated the retinal vasculature, HRV during flicker-light-induced-provocation (FLIP) and systemic cTnT, a marker of cardiac stress, to provide further evidence in support of the brain-retina-heart link.

METHODS

Cross-sectional observations were obtained from a bi-ethnic cohort (N = 264), aged 23-68 years. Fasting serum samples for cTnT were obtained. Retinal vascular calibres were quantified from mydriatic eye fundus images and dynamic retinal vessel calibre responses were determined during FLIP. Time-and frequency domain parameters of HRV were calculated during FLIP for each participant.

RESULTS

Africans had wider venules and attenuated time domain parameters during FLIP. In Africans, inverse associations emerged between arteriolar dilation and both cTnT and root-mean squared of the standard deviations of successive RR-intervals (rMSSD) (p = 0.030), and between arteriolar constriction and both low-frequency expressed in normalised units (LFnu) (p = 0.003) and high-frequency expressed in normalised units (p = 0.021). Wider venules inversely associated with standard deviation of the NN intervals (SDNN) as well as LFnu (p = 0.009) in Africans. An opposite profile was observed in Caucasians with both time-and frequency domain parameters of HRV in relation to retinal vessel structure and function.

CONCLUSION

FLIP elicited increased SNS activity and modulation in this bi-ethnic cohort. In Africans, decreased HRV during FLIP accompanied arteriolar and venular responses and elevated systemic levels of cTnT, implying that the SNS exerted a significant effect on the smooth muscle tone of the retinal vasculature. Disrupted retinal autoregulation may imply general autonomic nervous system dysfunction; exemplifying central control by the brain on all systemic regulatory functions, across different vascular beds.

The establishment of rat model in myocardial ischemia with psychological stress

BACKGROUND

Psychological stress can provoke and aggravate myocardial ischemia, and this stress can even trigger acute coronary syndromes or sudden cardiac death. Therefore, for the first time, this study aimed to investigate the method for establishing a rat model of myocardial ischemia with psychological stress and its evaluation.

METHODS

Forty male Wistar rats were randomly divided into the sham (S, n=10), myocardial infarct (MI, n=10), psychological stress (MODEL, n=10), and myocardial infarct with psychological stress (MI + MODEL, n=10) groups. The rat model of psychological stress was established by measuring the data from activity restriction for 6 hours and followed by tail clamp stimulation for 5 minutes every day for 14 days. The rat model of the myocardial infarct with psychological stress was established by occluding the left coronary anterior descending artery in the MODEL rats. The body weight of rats was measured daily, the behavior parameters were evaluated via open-field test and elevated plus-maze, tongue color and sublingual vein were observed, rats' acral blood flow perfusion was detected by PIM II (Perfusion Imager II), mesenteric microcirculation was measured by capillaroscopy, and hemodynamics was measured by a polygraph system. An automatic biochemical analyzer determined the content of serum cTnT (cardiac troponin T), Hcy (homocysteine), and activity of LDH (lactate dehydrogenase). Myocardial infarct size was measured with TTC (triphenyhetrazolium chloride) staining.

RESULTS

We found that rats in the psychological stress (MODEL) group were characterized by coarse hair, dark mucosa of the lips and claw, low spirit, decreased body weight, and increased anxiety. Compared with rats in the sham group, rats in the MODEL + MI group showed decreased mesenteric blood flow, narrowed arteriole and venule diameter, reduced acral blood flow perfusion, and LV ±dp/dtmax (the maximal rate of the increased and decrease of left ventricular pressure), as well as increased serum content of cTnT, Hcy, and LDH activity. Compared with the MI group, rats in the MODEL + MI group showed deteriorated microcirculation dysfunction manifested as a dark tongue color of deep purple, prominently extended and varicose sublingual vein, and aggravated myocardial damage in the form of increased infarct size and LDH leakage.

CONCLUSIONS

In conclusion, the rat model of myocardial ischemia with psychological stress was successfully established, and manifested as aggravating behavioral disorder, mesenteric microcirculation and left ventricular dysfunction, and myocardial damage.

Emerging misunderstood presentations of cardiovascular disease in young women

BACKGROUND

Cardiovascular disease (CVD) remains the leading cause of death for females in the United States accounting for over 412 000 female deaths in 2016. CVD mortality in young women <55 years old remains significantly high and greater than that in men.

HYPOTHESIS

There is a void with regards to awareness of CVD in women. Many traditional CVD risk estimate tools fail to identify the "at risk" female and is true for the young female patient. There needs to be a shift in focus from looking for the vulnerable plaque to looking for the "at risk" patient.

METHODS

This review outlines the emerging misunderstood presentations of CVD in young women which include certain categories of myocardial infarction (MI) with non-obstructive coronary arteries (MINOCA), such as spontaneous coronary artery dissection (SCAD), as well as the more stable myocardial ischemia with non-obstructive coronary arteries (INOCA) category focusing on mental stress-induced myocardial ischemia (MSIMI).

RESULTS

The prevalence of MINOCA in patients presenting with MI is greater in women. In younger women with CVD, SCAD is an emerging misunderstood presentation in this group of patients with type 2 SCAD being the most common form. MSIMI, a form of INOCA, is more common in women with CVD.

CONCLUSIONS

There are emerging misunderstood factors that are prevalent in young women, such as SCAD and MSIMI. It is important to recognize their presentations in young women to prevent misdiagnosis, missed diagnosis as well as mismanagement of these patients to improve their clinical outcomes.

Blockade of AT1 type receptors for angiotensin II prevents cardiac microvascular fibrosis induced by chronic stress in Sprague-Dawley rats

To test the effects of chronic-stress on the cardiovascular system, the model of chronic mild unpredictable stress (CMS) has been widely used. The CMS protocol consists of the random, intermittent, and unpredictable exposure of laboratory animals to a variety of stressors, during 3 consecutive weeks. In this study, we tested the hypothesis that exposure to the CMS protocol leads to left ventricle microcirculatory remodeling that can be attenuated by angiotensin II receptor blockade. Male Sprague-Dawley rats were randomly assigned into four groups: Control, Stress, Control + losartan, and Stress + losartan (N = 6, each group, losartan: 20 mg/kg/day). The rats were euthanized 15 days after CMS exposure, and blood samples and left ventricle were collected. Rats submitted to CMS presented increased glycemia, corticosterone, noradrenaline and adrenaline concentration, and losartan reduced the concentration of the circulating amines. Cardiac angiotensin II, measured by high-performance liquid chromatography (HPLC), was significantly increased in the CMS group, and losartan treatment reduced it, while angiotensin 1-7 was significantly higher in the CMS losartan-treated group as compared with CMS. Histological analysis, verified by transmission electron microscopy, showed that rats exposed to CMS presented increased perivascular collagen and losartan effectively prevented the development of this process. Hence, CMS induced a state of microvascular disease, with increased perivascular collagen deposition, that may be the trigger for further development of cardiovascular disease. In this case, CMS fibrosis is associated with increased production of catecholamines and with a disruption of renin-angiotensin system balance, which can be prevented by angiotensin II receptor blockade.