Regulation of Coronary Blood Flow

Association between admission blood pressure and spontaneous reperfusion and long-term prognosis in STEMI patients: an observational and multicenter study

BACKGROUND

This study aims to assess the associations of admission systolic blood pressure (SBP) level with spontaneous reperfusion (SR) and long-term prognosis in ST-elevation myocardial infarction (STEMI) patients.

METHODS

Data from 3809 STEMI patients who underwent primary percutaneous coronary intervention within 24 h, as recorded in the Chinese STEMI PPCI Registry (NCT04996901), were analyzed. The primary endpoint was SR, defined as thrombolysis in myocardial infarction grade 2-3 flow of IRA according to emergency angiography. The second endpoint was 2-year all-cause mortality. The association between admission BP and outcomes was evaluated using Logistic regression or Cox proportional hazards models with restricted cubic splines, adjusting for clinical characteristics.

RESULTS

Admission SBP rather than diastolic BP was associated with SR after adjustment. Notably, this relationship exhibits a nonlinear pattern. Below 120mmHg, There existed a significant positive correlation between admission SBP and the incidence of SR (adjusted OR per 10-mmHg decrease for SBP ≤ 120 mm Hg: 0.800; 95% CI: 0.706-0.907; p<0.001); whereas above 120mmHg, no further improvement in SR was observed (adjusted OR per 10-mmHg increase for SBP >120 mm Hg: 1.019; 95% CI: 0.958-1.084, p = 0.552). In the analysis of the endpoint event of mortality, patients admitted with SBP ranging from 121 to 150 mmHg exhibited the lowest mortality compared with those SBP ≤ 120mmHg (adjusted HR: 0.653; 95% CI: 0.495-0.862; p = 0.003). In addition, subgroups analysis with Killip class I-II showed SBP ≤ 120mmHg was still associated with increased risk of mortality.

CONCLUSION

The present study revealed admission SBP above 120 mmHg was associated with higher SR,30-d and 2-y survival rate in STEMI patients. The admission SBP could be a marker to provide clinical assessment and treatment.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT04996901), 07/27/2021.

Small conductance calcium-activated potassium channel contributes to stress induced endothelial dysfunctions

Patients with Takotsubo syndrome displayed endothelial dysfunction, but underlying mechanisms have not been fully clarified. This study aimed to explore molecular signalling responsible for catecholamine excess induced endothelial dysfunction. Human cardiac microvascular endothelial cells were challenged by epinephrine to mimic catecholamine excess. Patch clamp, FACS, ELISA, PCR, and immunostaining were employed for the study. Epinephrine (Epi) enhanced small conductance calcium-activated potassium channel current (ISK1-3) through activating α1 adrenoceptor. Phenylephrine enhanced edothelin-1 (ET-1) and reactive oxygen species (ROS) production, and the effects involved contribution of ISK1-3. H2O2 enhanced ISK1-3 and ET-1 production. Enhancing ISK1-3 caused a hyperpolarization, which increases ROS and ET-1 production. BAPTA partially reduced phenylephrine-induced enhancement of ET-1 and ROS, suggesting that α1 receptor activation can enhance ROS/ET-1 generation in both calcium-dependent and calcium-independent ways. The study demonstrates that high concentration catecholamine can activate SK1-3 channels through α1 receptor-ROS signalling and increase ET-1 production, facilitating vasoconstriction.

Impaired balance between coronary blood flow and myocardial metabolism in postpartum swine

Understanding of the mechanisms contributing to the increased maternal susceptibility for major adverse cardiovascular events in the postpartum period remains poor. Accordingly, this study tested the hypothesis that the balance between coronary blood flow and myocardial metabolism is compromised during the puerperium period (35-45 days post-delivery) in swine. Systemic and coronary hemodynamic responses were assessed in anesthetized, open-chest control (nonpregnant) and puerperium/postpartum swine at baseline and in response to intravenous infusion of dobutamine (1-30 μg/kg/min). Blood pressure and heart rate were lower in postpartum swine at baseline and in response to dobutamine (P < 0.05). Coronary blood flow and myocardial oxygen delivery were significantly diminished at baseline in postpartum swine (P < 0.001), which corresponded with ∼35% reduction in myocardial oxygen consumption (MVO2) (P < 0.001). Postpartum swine displayed enhanced retrograde coronary flow, larger cardiomyocyte area (P < 0.01) and marked capillary rarefaction (P < 0.01). The relationship between coronary blood flow and heart rate (P < 0.05) or MVO2 (P < 0.001) was significantly diminished in postpartum swine as dobutamine increased MVO2 up to ∼135% in both groups. This reduction in myocardial perfusion was associated with decreases in myocardial lactate uptake (P < 0.001), increases in coronary venous PCO2 (P < 0.01) and decreased coronary venous pH (P < 0.01). These findings suggest an impaired balance between coronary blood flow and myocardial metabolism could contribute to the increased incidence of maternal myocardial ischemia and premature death in the postpartum period.

Numerical assessment of using various outlet boundary conditions on the hemodynamics of an idealized left coronary artery model

Vascular diseases are greatly influenced by the hemodynamic parameters and the accuracy of determining these parameters depends on the use of correct boundary conditions. The present work carries out a two-way fluid-structure interaction (FSI) simulation to investigate the effects of outlet pressure boundary conditions on the hemodynamics through the left coronary artery bifurcation with moderate stenosis (50%) in the left anterior descending (LAD) branch. The Carreau viscosity model is employed to characterise the shear-thinning behaviour of blood. The results of the study reveal that the employment of zero pressure at the outlet boundaries significantly overestimates the values of hemodynamic variables like wall shear stress (WSS), and time-averaged wall shear stress (TAWSS) compared with human healthy and pulsatile pressure outlet conditions. However, the difference between these variables is marginally low for human healthy and pulsatile pressure outlets. The oscillatory shear index (OSI) remains the same across all scenarios, indicating independence from the outlet boundary condition. Furthermore, the magnitude of negative axial velocity and pressure drop across the plaque are found to be higher at the zero pressure outlet boundary condition.

Perspectives on the History of Coronary Physiology: Discovery of Major Principles and Their Clinical Correlates

Coronary circulation plays an essential role in delivering oxygen and metabolic substrates to satisfy the considerable energy demand of the heart. This article reviews the history that led to the current understanding of coronary physiology, beginning with William Harvey's revolutionary discovery of systemic blood circulation in the 17th century, and extending through the 20th century when the major mechanisms regulating coronary blood flow (CBF) were elucidated: extravascular compressive forces, metabolic control, pressure-flow autoregulation, and neural pathways. Pivotal research studies providing evidence for each of these mechanisms are described, along with their clinical correlates. The authors describe the major role played by researchers in the 19th century, who formulated basic principles of hemodynamics, such as Poiseuille's law, which provided the conceptual foundation for experimental studies of CBF regulation. Targeted research studies in coronary physiology began in earnest around the turn of the 20th century. Despite reliance on crude experimental techniques, the pioneers in coronary physiology made groundbreaking discoveries upon which our current knowledge is predicated. Further advances in coronary physiology were facilitated by technological developments, including methods to measure phasic CBF and its regional distribution, and by biochemical discoveries, including endothelial vasoactive molecules and adrenergic receptor subtypes. The authors recognize the invaluable contribution made by basic scientists toward the understanding of CBF regulation, and the enormous impact that this fundamental information has had on improving clinical diagnosis, decision-making, and patient care.

Roles and Mechanisms of Dopamine Receptor Signaling in Catecholamine Excess Induced Endothelial Dysfunctions

Endothelial dysfunction may contribute to pathogenesis of Takotsubo cardiomyopathy, but mechanism underlying endothelial dysfunction in the setting of catecholamine excess has not been clarified. The study reports that D1/D5 dopamine receptor signaling and small conductance calcium-activated potassium channels contribute to high concentration catecholamine induced endothelial cell dysfunction. For mimicking catecholamine excess, 100 μM epinephrine (Epi) was used to treat human cardiac microvascular endothelial cells. Patch clamp, FACS, ELISA, PCR, western blot and immunostaining analyses were performed in the study. Epi enhanced small conductance calcium-activated potassium channel current (ISK1-3) without influencing the channel expression and the effect was attenuated by D1/D5 receptor blocker. D1/D5 agonists mimicked the Epi effect, suggesting involvement of D1/D5 receptors in Epi effects. The enhancement of ISK1-3 caused by D1/D5 activation involved roles of PKA, ROS and NADPH oxidases. Activation of D1/D5 and SK1-3 channels caused a hyperpolarization, reduced NO production and increased ROS production. The NO reduction was membrane potential independent, while ROS production was increased by the hyperpolarization. ROS (H2O2) suppressed NO production. The study demonstrates that high concentration catecholamine can activate D1/D5 and SK1-3 channels through NADPH-ROS and PKA signaling and reduce NO production, which may facilitate vasoconstriction in the setting of catecholamine excess.

Acute Response of Different High-Intensity Interval Training Protocols on Cardiac Auto-Regulation Using Wearable Device

The purpose of this study was to compare different high-intensity interval training (HIIT) protocols with different lengths of work and rest times for a single session (all three had identical work-to-rest ratios and exercise intensities) for cardiac auto-regulation using a wearable device. With a randomized counter-balanced crossover, 13 physically active young male adults (age: 19.4 years, BMI: 21.9 kg/m2) were included. The HIIT included a warm-up of at least 5 min and three protocols of 10 s/50 s (20 sets), 20 s/100 s (10 sets), and 40 s/200 s (5 sets), with intensities ranging from 115 to 130% Wattmax. Cardiac auto-regulation was measured using a non-invasive method and a wearable device, including HRV and vascular function. Immediately after the HIIT session, the 40 s/200 s protocol produced the most intense stimulation in R-R interval (Δ-33.5%), ln low-frequency domain (Δ-42.6%), ln high-frequency domain (Δ-73.4%), and ln LF/HF ratio (Δ416.7%, all p < 0.05) compared to other protocols of 10 s/50 s and 20 s/100 s. The post-exercise hypotension in the bilateral ankle area was observed in the 40 s/200 s protocol only at 5 min after HIIT (right: Δ-12.2%, left: Δ-12.6%, all p < 0.05). This study confirmed that a longer work time might be more effective in stimulating cardiac auto-regulation using a wearable device, despite identical work-to-rest ratios and exercise intensity. Additional studies with 24 h measurements of cardiac autoregulation using wearable devices in response to various HIIT protocols are warranted.

Integrated modeling and simulation of recruitment of myocardial perfusion and oxygen delivery in exercise

While exercise-mediated vasoregulation in the myocardium is understood to be governed by autonomic, myogenic, and metabolic-mediated mechanisms, we do not yet understand the spatial heterogeneity of vasodilation or its effects on microvascular flow patterns and oxygen delivery. This study uses a simulation and modeling approach to explore the mechanisms underlying the recruitment of myocardial perfusion and oxygen delivery in exercise. The simulation approach integrates model components representing: whole-body cardiovascular hemodynamics, cardiac mechanics and myocardial work; myocardial perfusion; and myocardial oxygen transport. Integrating these systems together, model simulations reveal: (1.) To match expected flow and transmural flow ratios at increasing levels of exercise, a greater degree of vasodilation must occur in the subendocardium compared to the subepicardium. (2.) Oxygen extraction and venous oxygenation are predicted to substantially decrease with increasing exercise level preferentially in the subendocardium, suggesting that an oxygen-dependent error signal driving metabolic mediated recruitment of flow would be operative only in the subendocardium. (3.) Under baseline physiological conditions approximately 4% of the oxygen delivered to the subendocardium may be supplied via retrograde flow from coronary veins.

Links Between Obstructive Sleep Apnea and Myocardial Blood Flow Changes Impacting Adverse Cardiovascular Disease-related Outcomes

PURPOSE OF REVIEW

Recent studies have demonstrated an association between obstructive sleep apnea (OSA) and abnormal myocardial blood flow (MBF), myocardial flow reserve (MFR), and coronary microvascular dysfunction (CMD). Here, we review the evidence and describe the potential underlying mechanisms linking OSA to abnormal MBF. Examining relevant studies, we assess the impact of OSA-specific therapy, such as continuous positive airway pressure (CPAP), on MBF.

RECENT FINDINGS

Recent studies suggest an association between moderate to severe OSA and abnormal MBF/MFR. OSA promotes functional and structural abnormalities of the coronary microcirculation. OSA also promotes the uncoupling of MBF to cardiac work. In a handful of studies with small sample sizes, CPAP therapy improved MBF/MFR. Moderate to severe OSA is associated with abnormal MFR, suggesting an association with CMD. Evidence suggests that CPAP therapy improves MBF. Future studies must determine the clinical impact of improved MBF with CPAP.

The Effect of Heat Exposure on Myocardial Blood Flow and Cardiovascular Function

BACKGROUND

Heat extremes are associated with greater risk for cardiovascular death. The pathophysiologic mechanisms mediating this association are unknown.

OBJECTIVE

To quantify the myocardial blood flow (MBF) requirements of heat exposure.

DESIGN

Experimental study. (ClinicalTrials.gov: NCT04549974).

SETTING

Laboratory-based.

PARTICIPANTS

61 participants, comprising 20 healthy young adults (mean age, 28 years), 21 healthy older adults (mean age, 67 years), and 20 older adults with coronary artery disease (CAD) (mean age, 70 years).

INTERVENTION

Participants were heated until their core temperature increased 1.5 °C; MBF was measured before heat exposure and at every increase of 0.5 °C in core temperature.

MEASUREMENTS

The primary outcome was MBF measured by positron emission tomography-computed tomography. Secondary outcomes included heart rate, blood pressure, and body weight change.

RESULTS

At a core temperature increase of 1.5 °C, MBF increased in healthy young adults (change, 0.8 mL/min/g [95% CI, 0.5 to 1.0 mL/min/g]), healthy older adults (change, 0.7 mL/min/g [CI, 0.5 to 0.9 mL/min/g]), and older adults with CAD (change, 0.6 mL/min/g [CI, 0.3 to 0.8 mL/min/g]). This represented a 2.08-fold (CI, 1.75- to 2.41-fold), 1.79-fold (CI, 1.59- to 1.98-fold), and 1.64-fold (CI, 1.41- to 1.87-fold) change, respectively, from preexposure values. Imaging evidence of asymptomatic heat-induced myocardial ischemia was seen in 7 adults with CAD (35%) in post hoc analyses.

LIMITATIONS

In this laboratory-based study, heating was limited to about 100 minutes and participants were restricted in movement and fluid intake. Participants refrained from strenuous exercise and smoking; stopped alcohol and caffeine intake; and withheld β-blockers, calcium-channel blockers, and nitroglycerin before heating.

CONCLUSION

Heat exposure that increases core temperature by 1.5 °C nearly doubles MBF. Changes in MBF did not differ by age or presence of CAD, but some older adults with CAD may experience asymptomatic myocardial ischemia.

PRIMARY FUNDING SOURCE

Canadian Institutes of Health Research.

Expanding landscape of coronary microvascular disease in co-morbid conditions: Metabolic disease and beyond

Coronary microvascular disease (CMD) and impaired coronary blood flow control are defects that occur early in the pathogenesis of heart failure in cardiometabolic conditions, prior to the onset of atherosclerosis. In fact, recent studies have shown that CMD is an independent predictor of cardiac morbidity and mortality in patients with obesity and metabolic disease. CMD is comprised of functional, structural, and mechanical impairments that synergize and ultimately reduce coronary blood flow in metabolic disease and in other co-morbid conditions, including transplant, autoimmune disorders, chemotherapy-induced cardiotoxicity, and remote injury-induced CMD. This review summarizes the contemporary state-of-the-field related to CMD in metabolic and these other co-morbid conditions based on mechanistic data derived mostly from preclinical small- and large-animal models in light of available clinical evidence and given the limitations of studying these mechanisms in humans. In addition, we also discuss gaps in current understanding, emerging areas of interest, and opportunities for future investigations in this field.

Kv beta complex facilitates exercise-induced augmentation of myocardial perfusion and cardiac growth

The oxygen sensitivity of voltage-gated potassium (Kv) channels regulates cardiovascular physiology. Members of the Kv1 family interact with intracellular Kvβ proteins, which exhibit aldo-keto reductase (AKR) activity and confer redox sensitivity to Kv channel gating. The Kvβ proteins contribute to vasoregulation by controlling outward K+ currents in smooth muscle upon changes in tissue oxygen consumption and demand. Considering exercise as a primary physiological stimulus of heightened oxygen demand, the current study tested the role of Kvβ proteins in exercise performance, exercise-induced adaptations in myocardial perfusion, and physiological cardiac growth. Our findings reveal that genetic ablation of Kvβ2 proteins diminishes baseline exercise capacity in mice and attenuates the enhancement in exercise performance observed after long-term training. Moreover, we demonstrate that Kvβ2 proteins are critical for exercise-mediated enhancement in myocardial perfusion during cardiac stress as well as adaptive changes in cardiac structure. Our results underscore the importance of Kvβ proteins in metabolic vasoregulation, highlighting their role in modulating both exercise capacity and cardiovascular benefits associated with training. Furthermore, our study sheds light on a novel molecular target for enhancing exercise performance and improving the health benefits associated with exercise training in patients with limited capacity for physical activity.

Pulse pressure modifies the association between diastolic blood pressure and decrease in kidney function: the Japan Specific Health Checkups Study

Background

Unlike systolic blood pressure (SBP), the prognostic value of diastolic blood pressure (DBP) in kidney function has not been established. We hypothesized that pulse pressure (PP), which is associated with arteriosclerosis, would affect the prognostic value of DBP.

Methods

This longitudinal study used data from the Japan Specific Health Checkups Study was conducted between 2008 and 2014. The participants were stratified into three PP subgroups (low PP ≤39, normal PP 40-59 and high PP ≥60 mmHg). The exposures of interest were SBP and DBP, and the association between SBP/DBP and kidney outcomes (30% decline in the estimated glomerular filtration rate from baseline) was examined in each PP subgroup using a Cox proportional hazards model.

Results

Among 725 022 participants, 20 414 (2.8%) developed kidney outcomes during a median follow-up period of 34.6 months. Higher SBP was consistently associated with a higher incidence of kidney outcome in all PP subgroups. Although DBP had a positive linear association with the incidence of kidney outcome in low- and normal-PP subgroups, both lower (≤60 mmHg) and higher (≥101 mmHg) DBP were associated with a higher incidence of kidney outcome in the high-PP subgroup, with a U-shaped curve. Hazard ratios (95% confidence intervals) of ≤60 mmHg (reference: 61-80 mmHg in normal-PP subgroup) and ≥101 mmHg were 1.26 (1.15-1.38) and 1.86 (1.62-2.14), respectively.

Conclusions

In this large population-based cohort, DBP was differently associated with kidney outcome by PP level; lower DBP was significantly associated with a higher incidence of kidney outcome in the high-PP subgroup but not in the low- and normal-PP subgroups.

Unraveling the Gordian knot of coronary pressure-flow autoregulation

The coronary circulation has the inherent ability to maintain myocardial perfusion constant over a wide range of perfusion pressures. The phenomenon of pressure-flow autoregulation is crucial in response to flow-limiting atherosclerotic lesions which diminish coronary driving pressure and increase risk of myocardial ischemia and infarction. Despite well over half a century of devoted research, understanding of the mechanisms responsible for autoregulation remains one of the most fundamental and contested questions in the field today. The purpose of this review is to highlight current knowledge regarding the complex interrelationship between the pathways and mechanisms proposed to dictate the degree of coronary pressure-flow autoregulation. Our group recently likened the intertwined nature of the essential determinants of coronary flow control to the symbolically unsolvable "Gordian knot". To further efforts to unravel the autoregulatory "knot", we consider recent challenges to the local metabolic and myogenic hypotheses and the complicated dynamic structural and functional heterogeneity unique to the heart and coronary circulation. Additional consideration is given to interrogation of putative mediators, role of K+ and Ca2+ channels, and recent insights from computational modeling studies. Improved understanding of how specific vasoactive mediators, pathways, and underlying disease states influence coronary pressure-flow relations stands to significantly reduce morbidity and mortality for what remains the leading cause of death worldwide.

Review of cardiac-coronary interaction and insights from mathematical modeling

Cardiac-coronary interaction is fundamental to the function of the heart. As one of the highest metabolic organs in the body, the cardiac oxygen demand is met by blood perfusion through the coronary vasculature. The coronary vasculature is largely embedded within the myocardial tissue which is continually contracting and hence squeezing the blood vessels. The myocardium-coronary vessel interaction is two-ways and complex. Here, we review the different types of cardiac-coronary interactions with a focus on insights gained from mathematical models. Specifically, we will consider the following: (1) myocardial-vessel mechanical interaction; (2) metabolic-flow interaction and regulation; (3) perfusion-contraction matching, and (4) chronic interactions between the myocardium and coronary vasculature. We also provide a discussion of the relevant experimental and clinical studies of different types of cardiac-coronary interactions. Finally, we highlight knowledge gaps, key challenges, and limitations of existing mathematical models along with future research directions to understand the unique myocardium-coronary coupling in the heart. This article is categorized under: Cardiovascular Diseases > Computational Models Cardiovascular Diseases > Biomedical Engineering Cardiovascular Diseases > Molecular and Cellular Physiology.

Adaptive higher-order singular value decomposition clutter filter for ultrafast Doppler imaging of coronary flow under non-negligible tissue motion

BACKGROUND AND OBJECTIVE

With the development of advanced clutter-filtering techniques by singular value decomposition (SVD) and leveraging favorable acquisition settings such as open-chest imaging by a linear high-frequency probe and plane waves, several studies have shown the feasibility of cardiac flow measurements during the entire cardiac cycle, ranging from coronary flow to myocardial perfusion. When applying these techniques in a routine clinical setting, using transthoracic ultrasound imaging, new challenges emerge. Firstly, a smaller aperture is needed that can fit between ribs. Consequently, diverging waves are employed instead of plane waves to achieve an adequate field of view. Secondly, to ensure imaging at a larger depth, the maximum pulse repetition frequency has to be reduced. Lastly, in comparison to the open-chest scenario, tissue motion induced by the heartbeat is significantly stronger. The latter complicates substantially the distinction between clutter and blood signals.

METHODS

This study investigates a strategy to overcome these challenges by diverging wave imaging with an optimal number of tilt angles, in combination with dedicated clutter-filtering techniques. In particular, a novel, adaptive, higher-order SVD (HOSVD) clutter filter, which utilizes spatial, temporal, and angular information of the received ultrasound signals, is proposed to enhance clutter and blood separation.

RESULTS

When non-negligible tissue motion is present, using fewer tilt angles not only reduces the decorrelation between the received waveforms but also allows for collecting more temporal samples at a given ensemble duration, contributing to improved Doppler performance. The addition of a third angular dimension enables the application of HOSVD, providing greater flexibility in selecting blood separation thresholds from a 3-D tensor. This differs from the conventional threshold selection method in a 2-D spatiotemporal space using SVD. Exhaustive threshold search has shown a significant improvement in Contrast and Contrast-to-Noise ratio for Power Doppler images filtered with HOSVD compared to the SVD-based clutter filter.

CONCLUSION

With the improved settings, the obtained Power Doppler images show the feasibility of measuring coronary flow under the influence of non-negligible tissue motion in both in vitro and ex vivo.

Coronary microvascular dysfunction, arrythmias, and sudden cardiac death: A literature review

The coronary vascular system has a unique structure and function that is adaptive to myocardial demand. It is composed of a continuous network of vessels receding in size from epicardial arteries to the microvascular circulation. Failure to meet myocardial demand results in ischemia, angina, and adverse myocardial outcomes. It is evident that 50 % of patients with angina have a non-obstructive coronary disease and 66 % of these patients have coronary microvascular dysfunction (CMD). The impact of CMD on the atria and ventricles is exhibited through its association with atrial fibrillation and distortion of ventricular repolarization. Ultimately, this influence increases the risk of mortality, morbidity, and sudden cardiac arrest. CMD serves as an independent risk for atrial fibrillation, increases ventricular electrical inhomogeneity, and contributes to the progression of cardiac disease. The underlying pathogenesis may be attributed to oxidative stress evident through reactive oxygen species, impaired vasoactive function, and structural disorders such as fibrotic changes. Myocardial ischemia, brought about by a demand-supply mismatch in CMD, may create a milieu for ventricular arrythmia and sudden cardiac arrest through distortion of ventricular repolarization parameters such as QT dispersion and corrected QT dispersion.

Angiographic Coronary Slow Flow Is Not a Valid Surrogate for Invasively Diagnosed Coronary Microvascular Dysfunction

BACKGROUND

Ischemia with no obstructive coronary arteries is frequently caused by coronary microvascular dysfunction (CMD). Consensus diagnostic criteria for CMD include baseline angiographic slow flow by corrected TIMI (Thrombolysis In Myocardial Infarction) frame count (cTFC), but correlations between slow flow and CMD measured by invasive coronary function testing (CFT) are uncertain.

OBJECTIVES

The aim of this study was to investigate relationships between cTFC and invasive CFT for CMD.

METHODS

Adults with ischemia with no obstructive coronary arteries underwent invasive CFT with thermodilution-derived baseline coronary blood flow, coronary flow reserve (CFR), and index of microcirculatory resistance (IMR). CMD was defined as abnormal CFR (<2.5) and/or abnormal IMR (≥25). cTFC was measured from baseline angiography; slow flow was defined as cTFC >25. Correlations between cTFC and baseline coronary flow and between CFR and IMR and associations between slow flow and invasive measures of CMD were evaluated, adjusted for covariates. All patients provided consent.

RESULTS

Among 508 adults, 49% had coronary slow flow. Patients with slow flow were more likely to have abnormal IMR (36% vs 26%; P = 0.019) but less likely to have abnormal CFR (28% vs 42%; P = 0.001), with no difference in CMD (46% vs 51%). cTFC was weakly correlated with baseline coronary blood flow (r = -0.35; 95% CI: -0.42 to -0.27), CFR (r = 0.20; 95% CI: 0.12 to 0.28), and IMR (r = 0.16; 95% CI: 0.07-0.24). In multivariable models, slow flow was associated with lower odds of abnormal CFR (adjusted OR: 0.53; 95% CI: 0.35 to 0.80).

CONCLUSIONS

Coronary slow flow was weakly associated with results of invasive CFT and should not be used as a surrogate for the invasive diagnosis of CMD.

Pathophysiological mechanisms underlying increased circulating cardiac troponin in noncardiac surgery: a narrative review

Assay-specific increases in circulating cardiac troponin are observed in 20-40% of patients after noncardiac surgery, depending on patient age, type of surgery, and comorbidities. Increased cardiac troponin is consistently associated with excess morbidity and mortality after noncardiac surgery. Despite these findings, the underlying mechanisms are unclear. The majority of interventional trials have been designed on the premise that ischaemic cardiac disease drives elevated perioperative cardiac troponin concentrations. We consider data showing that elevated circulating cardiac troponin after surgery could be a nonspecific marker of cardiomyocyte stress. Elevated concentrations of circulating cardiac troponin could reflect coordinated pathological processes underpinning organ injury that are not necessarily caused by ischaemia. Laboratory studies suggest that matching of coronary artery autoregulation and myocardial perfusion-contraction coupling limit the impact of systemic haemodynamic changes in the myocardium, and that type 2 ischaemia might not be the likeliest explanation for cardiac troponin elevation in noncardiac surgery. The perioperative period triggers multiple pathological mechanisms that might cause cardiac troponin to cross the sarcolemma. A two-hit model involving two or more triggers including systemic inflammation, haemodynamic strain, adrenergic stress, and autonomic dysfunction might exacerbate or initiate acute myocardial injury directly in the absence of cell death. Consideration of these diverse mechanisms is pivotal for the design and interpretation of interventional perioperative trials.

Electrocardiograms Do Not Detect Myocardial Ischemia in Patients With Williams Syndrome and Nonsyndromic Elastin Arteriopathy With Coronary Artery Stenosis

Coronary artery stenosis (CAS) may affect up to 27% of patients with Williams syndrome (WS), which may lead to myocardial ischemia. Patients with WS face a 25- to 100-fold greater risk of sudden cardiac death, frequently linked to anesthesia. Assessing CAS requires either imaging while under general anesthesia or intraoperative assessment, with the latter considered the gold standard. Our study aimed to identify electrocardiogram (ECG) markers of myocardial ischemia in patients with WS or nonsyndromic elastin arteriopathy and documented CAS. We retrospectively reviewed patients with WS/elastin arteriopathy who underwent supravalvar aortic stenosis surgery and CAS assessment from January 1, 2006 to April 30, 2021. A pediatric electrophysiologist, not aware of the patients' CAS status, reviewed their preoperative ECGs for markers of ischemia. We assessed associations of study parameters using Wilcoxon rank-sum and Fisher's exact tests. Of 34 patients, 62% were male, with a median age of 20 months (interquartile range: 8 to 34). CAS was present in 62% (21 of 34), 76% of whom (16 of 21) were male. There were no ECG indicators of myocardial ischemia in patients with CAS. In conclusion, CAS was present in >1/2 the children with WS/elastin arteriopathy who underwent repair of supravalvar aortic stenosis. CAS in WS/nonsyndromic elastin arteriopathy does not appear to exhibit typical ECG-detectable myocardial ischemia. ECGs are not a useful screening tool for CAS in WS/elastin arteriopathy. Given the high anesthesia-related cardiac arrest risk, other noninvasive indicators of CAS are needed.

Individualized Perioperative Hemodynamic Management Using Hypotension Prediction Index Software and the Dynamics of Troponin and NTproBNP Concentration Changes in Patients Undergoing Oncological Abdominal Surgery

INTRODUCTION

Abdominal oncologic surgeries pose significant risks due to the complexity of the surgery and patients' often weakened health, multiple comorbidities, and increased perioperative hazards. Hypotension is a major risk factor for perioperative cardiovascular complications, necessitating individualized management in modern anesthesiology.

AIM

This study aimed to determine the dynamics of changes in troponin and NTproBNP levels during the first two postoperative days in patients undergoing major cancer abdominal surgery with advanced hemodynamic monitoring including The AcumenTM Hypotension Prediction Index software (HPI) (Edwards Lifesciences, Irvine, CA, USA) and their association with the occurrence of postoperative cardiovascular complications.

METHODS

A prospective study was conducted, including 50 patients scheduled for abdominal cancer surgery who, due to the overall risk of perioperative complications (ASA class 3 or 4), were monitored using the HPI software. Hypotension was qualified as at least one ≥ 1 min episode of a MAP < 65 mm Hg. Preoperatively and 24 and 48 h after the procedure, the levels of NTproBNP and troponin were measured, and an ECG was performed.

RESULTS

We analyzed data from 46 patients and found that 82% experienced at least one episode of low blood pressure (MAP < 65 mmHg). However, the quality indices of hypotension were low, with a median time-weighted average MAP < 65 mmHg of 0.085 (0.03-0.19) mmHg and a median of 2 (2-1.17) minutes spent below MAP < 65 mmHg. Although the incidence of perioperative myocardial injury was 10%, there was no evidence to suggest a relationship with hypotension. Acute kidney injury was seen in 23.9% of patients, and it was significantly associated with a number of episodes of MAP < 50 mmHg. Levels of NTproBNP were significantly higher on the first postoperative day compared to preoperative values (285.8 [IQR: 679.8] vs. 183.9 [IQR: 428.1] pg/mL, p < 0.001). However, they decreased on the second day (276.65 [IQR: 609.4] pg/mL, p = 0.154). The dynamics of NTproBNP were similar for patients with and without heart failure, although those with heart failure had significantly higher preoperative concentrations (435.9 [IQR: 711.15] vs. 87 [IQR: 232.2] pg/mL, p < 0.001). Patients undergoing laparoscopic surgery showed a statistically significant increase in NTproBNP.

CONCLUSIONS

This study suggests that advanced HPI monitoring in abdominal cancer surgery effectively minimizes intraoperative hypotension with no significant NTproBNP or troponin perioperative dynamics, irrespective of preoperative heart failure.

Monitoring coronary blood flow by laser speckle contrast imaging after myocardial ischaemia reperfusion injury in adult and aged mice

Introduction

Investigating coronary microvascular perfusion responses after myocardial infarction (MI) would aid in the development of flow preserving therapies. Laser speckle contrast imaging (LSCI) is a powerful tool used for real-time, non-contact, full-field imaging of blood flow in various tissues/organs. However, its use in the beating heart has been limited due to motion artifacts.

Methods

In this paper, we report the novel use of LSCI, combined with custom speckle analysis software (SpAn), to visualise and quantitate changes in ventricular perfusion in adult and aged mice undergoing ischaemia-reperfusion (IR) injury. The therapeutic benefit of inhibiting the actions of the pro-inflammatory cytokine interleukin-36 (IL-36) was also investigated using an IL-36 receptor antagonist (IL-36Ra).

Results

Imaging from uncovered and covered regions of the left ventricle demonstrated that whilst part of the LSCI flux signal was derived from beating motion, a significant contributor to the flux signal came from ventricular microcirculatory blood flow. We show that a biphasic flux profile corresponding to diastolic and systolic phases of the cardiac cycle can be detected without mathematically processing the total flux data to denoise motion artifacts. Furthermore, perfusion responses to ischaemia and postischaemia were strong, reproducible and could easily be detected without the need to subtract motion-related flux signals. LSCI also identified significantly poorer ventricular perfusion in injured aged mice following IR injury which markedly improved with IL-36Ra.

Discussion

We therefore propose that LSCI of the heart is possible despite motion artifacts and may facilitate future investigations into the role of the coronary microcirculation in cardiovascular diseases and development of novel therapies.

Myocardial perfusion in cardiac amyloidosis

AIMS

Cardiac involvement is the main driver of clinical outcomes in systemic amyloidosis and preliminary studies support the hypothesis that myocardial ischaemia contributes to cellular damage. The aims of this study were to assess the presence and mechanisms of myocardial ischaemia using cardiovascular magnetic resonance (CMR) with multiparametric mapping and histopathological assessment.

METHODS AND RESULTS

Ninety-three patients with cardiac amyloidosis (CA) (light-chain amyloidosis n = 42, transthyretin amyloidosis n = 51) and 97 without CA (three-vessel coronary disease [3VD] n = 47, unobstructed coronary arteries n = 26, healthy volunteers [HV] n = 24) underwent quantitative stress perfusion CMR with myocardial blood flow (MBF) mapping. Twenty-four myocardial biopsies and three explanted hearts with CA were analysed histopathologically. Stress MBF was severely reduced in patients with CA with lower values than patients with 3VD, unobstructed coronary arteries and HV (CA: 1.04 ± 0.51 ml/min/g, 3VD: 1.35 ± 0.50 ml/min/g, unobstructed coronary arteries: 2.92 ± 0.52 ml/min/g, HV: 2.91 ± 0.73 ml/min/g; CA vs. 3VD p = 0.011, CA vs. unobstructed coronary arteries p < 0.001, CA vs. HV p < 0.001). Myocardial perfusion abnormalities correlated with amyloid burden, systolic and diastolic function, structural parameters and blood biomarkers (p < 0.05). Biopsies demonstrated abnormal vascular endothelial growth factor staining in cardiomyocytes and endothelial cells, which may be related to hypoxia conditions. Amyloid infiltration in intramural arteries was associated with severe lumen reduction and severe reduction in capillary density.

CONCLUSION

Cardiac amyloidosis is associated with severe inducible myocardial ischaemia demonstrable by histology and CMR stress perfusion mapping. Histological evaluation indicates a complex pathophysiology, where in addition to systolic and diastolic dysfunction, amyloid infiltration of the epicardial arteries and disruption and rarefaction of the capillaries play a role in contributing to myocardial ischaemia.

Longitudinal Strain Patterns in Stress (Takotsubo) Cardiomyopathy: Evidence of Global Myocardial Injury and Incomplete Recovery

Stress cardiomyopathy develops after abrupt sympathetic stimulation, likely from catecholamine-induced myocardial toxicity. The evolution of myocardial strain during and after an episode have not been previously characterized. We aimed to determine whether preexisting contractile abnormalities may explain the observed regional dysfunction during an acute episode and to investigate the persistence of strain abnormalities after clinical recovery. We identified patients who were diagnosed with stress cardiomyopathy and had an echocardiogram performed before their episode, during their episode, and within 1 year after. The diagnosis was confirmed based on the absence of obstructive coronary lesions. Left ventricular (LV) longitudinal strain was calculated using speckle-tracking software and compared between baseline, episode, and follow-up echocardiograms. The LV strain analysis was performed on 23 patients. The LV ejection fraction was 64 ± 8.7% at baseline, 45 ± 12% during the episode, and 5 9 ± 10% after a median follow-up of 46 days. The LV global longitudinal strain was 24 ± 4.7% at baseline, 11 ± 4.9% during the episode, and 19 ± 4.6% after the follow-up. The mean ejection fraction (p <0.01) and global longitudinal strain (p <0.001) remained below baseline levels at follow-up. Longitudinal strain was reduced (<18%) in 80 ± 23% of myocardial segments during an episode and 41 ± 21% of myocardial segments at follow-up. During the acute episode, 35 ± 6% of the abnormal segments were in the base, outside of the region of ballooning. Our findings suggests that stress cardiomyopathy is associated with global rather than regional myocardial injury and that contractile abnormalities persist after clinical improvement. These findings challenge our previous understanding of stress cardiomyopathy and may guide future pathophysiologic understanding of this complex disease.

Modelling coronary flow and myocardial perfusion by integrating a structured-tree coronary flow model and a hyperelastic left ventricle model

BACKGROUND AND OBJECTIVE

There is an increasing demand to establish integrated computational models that facilitate the exploration of coronary circulation in physiological and pathological contexts, particularly concerning interactions between coronary flow dynamics and myocardial motion. The field of cardiology has also demonstrated a trend toward personalised medicine, where these integrated models can be instrumental in integrating patient-specific data to improve therapeutic outcomes. Notably, incorporating a structured-tree model into such integrated models is currently absent in the literature, which presents a promising prospect. Thus, the goal here is to develop a novel computational framework that combines a 1D structured-tree model of coronary flow in human coronary vasculature with a 3D left ventricle model utilising a hyperelastic constitutive law, enabling the physiologically accurate simulation of coronary flow dynamics.

METHODS

We adopted detailed geometric information from previous studies of both coronary vasculature and left ventricle to construct the coronary flow model and the left ventricle model. The structured-tree model for coronary flow was expanded to encompass the effect of time-varying intramyocardial pressure on intramyocardial blood vessels. Simultaneously, the left ventricle model served as a robust foundation for the calculation of intramyocardial pressure and subsequent quantitative evaluation of myocardial perfusion. A one-way coupling framework between the two models was established to enable the evaluation and examination of coronary flow dynamics and myocardial perfusion.

RESULTS

Our predicted coronary flow waveforms aligned well with published experimental data. Our model precisely captured the phasic pattern of coronary flow, including impeded or even reversed flow during systole. Moreover, our assessment of coronary flow, considering both globally and regionally averaged intramyocardial pressure, demonstrated that elevated intramyocardial pressure corresponds to increased impeding effects on coronary flow. Furthermore, myocardial blood flow simulated from our model was comparable with MRI perfusion data at rest, showcasing the capability of our model to predict myocardial perfusion.

CONCLUSIONS

The integrated model introduced in this study presents a novel approach to achieving physiologically accurate simulations of coronary flow and myocardial perfusion. It holds promise for its clinical applicability in diagnosing insufficient myocardial perfusion.

Association between peripheral endothelial function and myocardial perfusion in patients with coronary artery disease

Aims

Endothelial dysfunction is a systemic disorder and risk factor for atherosclerosis. Our aim was to assess whether there is a relation between peripheral endothelial function and myocardial perfusion in patients with coronary artery disease (CAD).

Methods and results

We prospectively studied 54 patients, who had a positive result for obstructive CAD in coronary CT angiography. Myocardial perfusion (15O)H2O positron emission tomography was imaged at rest and during adenosine-induced maximal vasodilation. Peripheral endothelial function was assessed by measuring flow-mediated dilation (FMD) with ultrasound from the left brachial artery. There was a statistically significant correlation between FMD and global hyperaemic myocardial blood flow (MBF; r = 0.308, P = 0.023). The correlation remained statistically significant when controlling for gender, height, and diastolic blood pressure at rest (r = 0.367, P = 0.008). Receiver operating character analysis, however, yielded an area under curve of only 0.559 (P = 0.492) when FMD was used to predict reduced MBF (below 2.3 mL/g/min). Patients with significantly decreased MBF (n = 14) underwent invasive coronary angiography. FMD showed an inverse correlation with the severity of the most significant stenosis (r = -0.687, P = 0.007).

Conclusion

Peripheral endothelial function is related with hyperaemic MBF and with the severity of CAD in invasive coronary angiography. Due to insufficient sensitivity and specificity in the identification of reduced MBF, FMD is not suitable for clinical practice at the individual level. However, it works at the population level as a research tool when assessing endothelial dysfunction in patients with CAD.

An in vivo investigation on the effects of stent implantation on hematological and hemorheological parameters

BACKGROUND

Even though cardiovascular stenting is widely used for the treatment of coronary artery disease, information on how it can affect the hematological and hemorheological profile is scarce in the literature. Most of the work on this issue is based on theoretical or computational fluid dynamics models, lacking in-depth in vitro and in vivo experimental verification.

OBJECTIVE

This work investigates, in an in vivo setting, the effects of stenting and the implantation time-course on hematological and hemorheological parameters that could potentially compromise the device's functionality and longevity.

METHODS

Custom-made self-expanding nitinol stents were implanted in the common carotid artery of male CD1 mice. Whole blood samples were collected from control (non-stented) and stented animals at 5 and 10 weeks post-implantation. Hematological measurements and blood viscosity, red blood cell aggregation, and deformability were performed using standard techniques.

RESULTS

Implant-induced changes were observed in some of the hematological and hemorheological indices. Blood viscosity seems to have been negatively affected by an increased hematocrit and reduced RBC deformability, at 10 weeks post-implantation, despite a slight decrease in RBC aggregation.

CONCLUSIONS

Although the alterations observed may be the result of the peri-implant inflammatory response, the physiological consequences due to hemorheological changes need to be further investigated.

Characteristics of the phenotype of mixed cardiomyopathy in patients with implantable cardioverter-defibrillators

BACKGROUND OR PURPOSE

The prognosis of m ixed cardiomyopathy (CMP) in patients with implanted cardioverter-defibrillators (ICDs) has not been investigated. We aim to study the demographic, clinical, device therapies and survival characteristics of mixed CMP in a cohort of patients implanted with a defibrillator.

METHODS

The term mixed CMP was used to categorise patients with impaired left ventricular ejection fraction attributed to documented non-ischemic triggers with concomitant moderate coronary artery disease. This is a single center observational cohort of 526 patients with a mean follow-up of 8.7 ± 3.5 years.

RESULTS

There were 42.5% patients with ischemic cardiomyopathy (ICM), 26.9% with non-ischemic cardiomyopathy (NICM) and 30.6% with mixed CMP. Mixed CMP, compared to NICM, was associated with higher mean age (69.1 ± 9.6 years), atrial fibrillation (55.3%) and greater incidence of comorbidities. The proportion of patients with mixed CMP receiving device shocks was 23.6%, compared to 18.4% in NICM and 27% in ICM. The VT cycle length recorded in mixed CMP (281.6 ± 43.1 ms) was comparable with ICM (282.5 ± 44 ms; p = 0.9) and lesser than NICM (297.7 ± 48.7 ms; p = 0.1). All-cause mortality in mixed CMP (21.1%) was similar to ICM (20.1%; p = 0.8) and higher than NICM (15.6%; p = 0.2). The Kaplan-Meier curves revealed hazards of 1.57 (95% CI: 0.91, 2.68) for mixed CMP compared to NICM.

CONCLUSION

In a cohort of patients with ICD, the group with mixed CMP represents a phenotype predominantly comprised of the elderly with a higher incidence of comorbidities. Mixed CMP resembles ICM in terms of number of device shocks and VT cycle length. Trends of long-term prognosis of patients with mixed CMP are worse than NICM and similar to ICM.

Large intercoronary communication between the right coronary artery and the left circumflex artery in a patient with late stent thrombosis: A case report

Intercoronary communication (ICC) is a very rare coronary artery anomaly that connects directly 2 coronary arteries. This anastomosis is found between 2 nonobstructed coronary arteries with unidirectional or bidirectional blood flow. We report a case of a large ICC between the right coronary artery and the left circumflex artery in a patient with late stent thrombosis. The electrocardiogram showed ST-segment elevation in the anterior leads. The echocardiography investigation revealed hypokinesis in the proximal, medial and apical segments of the interventricular septum and anterior wall as well as the apex. During invasive coronary examination a large ICC between the left circumflex artery (LCx) and the right coronary artery (RCA) was found. Furthermore, coronary angiography demonstrated proximal occlusion (stent thrombosis) of the left anterior descending artery (LAD), prompting the utilization of percutaneous intervention with a drug-eluting stent. The presence of a large intercoronary communication is an exceedingly uncommon anomaly of the coronary arteries, which has the potential to induce myocardial ischemia. In individuals with obstructive coronary artery disease, this anomaly can further worsen the existing condition.

Effects of alpha-adrenergic receptor blockade on coronary circulation in postmenopausal women

We sought to investigate the effect of the α1-adrenergic receptor blockade during handgrip exercise (Grip), isolated metaboreflex activation (Metabo), and cold pressor test (CPT) on coronary circulation in young (YW) and postmenopausal women (PMW). Ten YW and 9 PMW underwent two protocols: (1) 3 min of baseline followed by 3 min of CPT and (2) 3 min of rest, 3 min of Grip followed by 3 min of Metabo. Protocols were carried out under control conditions and α1-adrenergic receptor blockade (oral prazosin 0.03 mg·kg-1). Coronary blood velocity (CBV) and vascular conductance (CCI) were lower in PMW. Grip increased CBV only in YW (YW: Δ18.0 ± 21.1% vs. PMW: Δ4.2 ± 10.1%; p < 0.05), and the blockade did not change the CBV response to Grip in YW and PMW. During the Metabo, CBV returned to resting levels in YW and was unchanged from rest in PMW, before (YW:Δ1.7 ± 8.7% vs. PMW: Δ- 1.5 ± 8.6) and under the blockade (YW: Δ4.5 ± 14.8% vs. PMW: Δ9.1 ± 29.5%). CPT did not change CBV in both groups (YW: Δ3.9 ± 8.0 vs. PMW: Δ- 4.1 ± 6.2%), following the α1-blockade, CPT increased CBV only in YW (YW: Δ11.2 ± 12.8% vs. PMW: Δ2.2 ± 7.1%; p < 0.05 for group and condition). CCI decreased during Grip, Metabo, and CPT in YW and PMW, while the blockade prevented that decrease only in YW. The α1-adrenergic receptor plays a role in the control of coronary circulation in young women, evoking stronger vasoconstriction during CPT than Grip and Metabo in YW. PMW have impaired vasomotor control in the coronary circulation, which seems not to be caused by the α1-adrenergic receptor.

Pharmacological and mechanical properties of isolated pig coronary veins

Recent successful cardiac transplantation from pig to non-human primates and the first pig-to-human transplantation has put the focus on the properties of the pig heart. In contrast to the coronary arteries, the coronary veins are less well characterized and the aim was to examine the mechanical and pharmacological properties of coronary veins in comparison to the arteries. Vessel segments from the left anterior descending coronary artery (LAD) and the concomitant vein were isolated from pig hearts in cardioplegia and examined in vitro. The wall thickness, active tension and active stress at optimal circumference were lower in coronary veins, reflecting the lower intravascular pressure in vivo. Reverse transcription polymerase chain reaction (RT-PCR) analysis of myosin isoforms showed that the vein could be characterized as having a slower smooth muscle phenotype compared to the artery. Both vessel types contracted in response to the thromboxane agonist U46619 with EC50 values of about 20 nM. The artery contracted in response to acetylcholine. Precontracted arteries relaxed in noradrenaline and substance P. In contrast, the veins relaxed in acetylcholine, contracted in noradrenaline and were unresponsive to substance P. In conclusion, these results demonstrate significant differences between the coronary artery and vein in the smooth muscle properties and in the responses to sympathetic and parasympathetic stimuli.

Lumped-parameter model as a non-invasive tool to assess coronary blood flow in AAOCA patients

Anomalous aortic origin of the coronary artery (AAOCA) is a rare disease associated with sudden cardiac death, usually related to physical effort in young people. Clinical routine tests fail to assess the ischemic risk, calling for novel diagnostic approaches. To this aim, some recent studies propose to assess the coronary blood flow (CBF) in AAOCA by computational simulations but they are limited by the use of data from literature retrieved from normal subjects. To overcome this limitation and obtain a reliable assessment of CBF, we developed a fully patient-specific lumped parameter model based on clinical imaging and in-vivo data retrieved during invasive coronary functional assessment of subjects with AAOCA. In such a way, we can estimate the CBF replicating the two hemodynamic conditions in-vivo analyzed. The model can mimic the effective coronary behavior with high accuracy and could be a valuable tool to quantify CBF in AAOCA. It represents the first step required to move toward a future clinical application with the aim of improving patient care. The study was registered at Clinicaltrial.gov with (ID: NCT05159791, date 2021-12-16).

NTPDase1/CD39 Ectonucleotidase Is Necessary for Normal Arterial Diameter Adaptation to Flow

NTPDase1/CD39, the major vascular ectonucleotidase, exerts thrombo-immunoregulatory function by controlling endothelial P2 receptor activation. Despite the well-described release of ATP from endothelial cells, few data are available regarding the potential role of CD39 as a regulator of arterial diameter. We thus investigated the contribution of CD39 in short-term diameter adaptation and long-term arterial remodeling in response to flow using Entpd1-/- male mice. Compared to wild-type littermates, endothelial-dependent relaxation was modified in Entpd1-/- mice. Specifically, the vasorelaxation in response to ATP was potentiated in both conductance (aorta) and small resistance (mesenteric and coronary) arteries. By contrast, the relaxing responses to acetylcholine were supra-normalized in thoracic aortas while decreased in resistance arteries from Entpd1-/- mice. Acute flow-mediated dilation, measured via pressure myography, was dramatically diminished and outward remodeling induced by in vivo chronic increased shear stress was altered in the mesenteric resistance arteries isolated from Entpd1-/- mice compared to wild-types. Finally, changes in vascular reactivity in Entpd1-/- mice were also evidenced by a decrease in the coronary output measured in isolated perfused hearts compared to the wild-type mice. Our results highlight a key regulatory role for purinergic signaling and CD39 in endothelium-dependent short- and long-term arterial diameter adaptation to increased flow.

Total-Body Positron Emission Tomography: Adding New Perspectives to Cardiovascular Research

The recent advent of positron emission tomography (PET) scanners that can image the entire human body opens up intriguing possibilities for cardiovascular research and future clinical applications. These new systems permit radiotracer kinetics to be measured in all organs simultaneously. They are particularly well suited to study cardiovascular disease and its effects on the entire body. They could also play a role in quantitatively measuring physiologic, metabolic, and immunologic responses in healthy individuals to a variety of stressors and lifestyle interventions, and may ultimately be instrumental for evaluating novel therapeutic agents and their molecular effects across different tissues. In this review, we summarize recent progress in PET technology and methodology, discuss several emerging cardiovascular applications for total-body PET, and place this in the context of multiorgan and systems medicine. Finally, we discuss opportunities that will be enabled by the technology, while also pointing to some of the challenges that still need to be addressed.

[Anatomy-physiology considerations for cardiogenic shock with right ventricular involvement]

Since the discovery of right ventricular infarction, interest in the characteristics of the right ventricle has been increasing. Right ventricular function is now known to be a predictor of mortality in different settings. The right ventricle is a low-pressure, high-compliance, high-volume chamber. To carry out its normal function, it is coupled to the pulmonary circulation and the left ventricle. In the face of acute changes in pressure, volume overload and ischemia, it dilates to adapt to its new load. Its manifestation may be ventricular dysfunction and/or failure that will progress to cardiogenic shock due to right ventricular involvement. Various entities may be the cause of acute dysfunction: right ventricular infarction (alterations in contractility due to ischemia) and high-risk pulmonary thromboembolism (increased afterload). Both share a similar ventricular pathophysiology and high mortality without treatment. Understanding anatomy and physiology, dysfunction and acute ventricular failure are important to define a convenient diagnosis and treatment oriented towards pathophysiology. In this first part, the anatomy and physiology, acute right ventricular dysfunction/failure and cardiogenic shock are taken into consideration, from the perspective of these two entities. In another paper, treatment aimed at cardiogenic shock due to right ventricular involvement will be reviewed.

A new synergistic model for simulating exercise incorporating control mechanisms at cellular and organ scales

The physiological response of the cardio-vascular system (CVS) to physical activity is of great importance to those working in sporting research and has profound consequences for the health and well-being of people. Coronary vasodilation and the physiological mechanisms involved in exercise have frequently been the focus of numerical models for simulating exercise. This is partly achieved using the time-varying-elastance (TVE) theory, which prescribes the pressure-volume relationship of the ventricle as a periodic function of time, tuned using empirical data. The empirical foundations of the TVE method however, and its suitability for CVS modelling are frequently questioned. To overcome this challenge, we adopt a different synergistic approach in which a model for the microscale heart muscle (myofibers) activity is embedded within a macro organ-scale CVS model. We developed such a synergistic model by including the coronary flow and various control mechanisms at the circulation level through feedback and feedforward means, and at the microscale (contractile) through the regulation of ATP availability and myofiber force depending on exercise intensity or heart rate. The coronary flow produced by the model displays the well-known 2-phase character of the flow, which is preserved under exercise. The model is tested by simulating reactive hyperemia, which is a transient occlusion of the coronary flow, successfully reproducing the additional coronary flow following the block removal. On-transient exercise results reveal a rise in both cardiac output and mean ventricle pressure as expected. The stroke volume increases initially, but then declines during the latter period of HR rise, corresponding with one of the main physiological responses to exercise. The pressure-volume loop expands during exercise, as systolic pressure rises. The Myocardial oxygen demand increases during exercise and the coronary blood supply increases in response, causing an excess of oxygen supply to the heart. Off-transient exercise recovery is largely a reverse of this response, although the behaviour is slightly more varied, with sudden spikes in coronary resistance. Different levels of fitness and exercise intensity are tested and reveal that the stroke volume rises until a level of myocardial oxygen demand is reached at which point it declines. This level of demand is independent of fitness or exercise intensity. An advantage of our model is demonstrated in the correspondence between the micro and organ scale mechanics so that cellular pathologies can be traced from exercise performance with relatively little computational or experimental expense.

Myocardial perfusion and flow reserve in the asynchronous heart: mechanistic insight from a computational model

The tight coupling between myocardial oxygen demand and supply has been recognized for decades, but it remains controversial whether this coupling persists under asynchronous activation, such as during left bundle branch block (LBBB). Furthermore, it is unclear whether the amount of local cardiac wall growth, following longer-lasting asynchronous activation, can explain differences in myocardial perfusion distribution between subjects. For a better understanding of these matters, we built upon our existing modeling framework for cardiac mechanics-to-perfusion coupling by incorporating coronary autoregulation. Regional coronary flow was regulated with a vasodilator signal based on regional demand, as estimated from regional fiber stress-strain area. Volume of left ventricular wall segments was adapted with chronic asynchronous activation toward a homogeneous distribution of myocardial oxygen demand per tissue weight. Modeling results show that 1) both myocardial oxygen demand and supply are decreased in early activated regions and increased in late-activated regions; 2) but that regional hyperemic flow remains unaffected; while 3) regional myocardial flow reserve (the ratio of hyperemic to resting myocardial flow) decreases with increases in absolute regional myocardial oxygen demand as well as with decreases in wall thickness. These findings suggest that septal hypoperfusion in LBBB represents an autoregulatory response to reduced myocardial oxygen demand. Furthermore, oxygen demand-driven remodeling of wall mass can explain asymmetric hypertrophy and the related homogenization of myocardial perfusion and flow reserve. Finally, the inconsistent observations of myocardial perfusion distribution can primarily be explained by the degree of dyssynchrony, the degree of asymmetric hypertrophy, and the imaging modality used.NEW & NOTEWORTHY This versatile modeling framework couples myocardial oxygen demand to oxygen supply and myocardial growth, enabling simulation of resting and hyperemic myocardial flow during acute and chronic asynchronous ventricular activation. Model-based findings suggest that reported inconsistencies in myocardial perfusion and flow reserve responses with asynchronous ventricular activation between patients can primarily be explained by the degree of dyssynchrony and wall mass remodeling, which together determine the heterogeneity in regional oxygen demand and, hence, supply with autoregulation.

Sympathetic control of the coronary circulation during trigeminal nerve stimulation in humans

PURPOSE

We sought to investigate the sympathetic mechanism controlling coronary circulation during trigeminal nerve stimulation in healthy women.

METHODS

The protocol consisted of 3 min of trigeminal nerve stimulation (TGS) with cold stimuli to the face, in two conditions: (1) control and β-blockade (oral propranolol), and (2) control and α-blockade (oral prazosin).

RESULTS

Thirty-one healthy young subjects (women: n = 13; men: n = 18) participated in the study. By design, TGS decreased heart rate (HR), and increased blood pressure (BP) and cardiac output (CO). Before the β-blockade coronary blood velocity (CBV-Δ1.4 ± 1.3 cm s-1) increased along with the decrease of coronary vascular conductance index (CVCi-Δ-0.04 ± 0.04 cm s-1 mmHg-1) during TGS and the β-blockade abolished the CBV increase and a further decrease of CVCi was observed with TGS (Δ-0.06 ± 0.07 cm s-1 mmHg-1). During the α-blockade condition before the blockade, the CBV increased (Δ0.93 ± 1.48 cm s-1) along with the decrease of CVCi (Δ-0.05 ± 1.12 cm s-1 mmHg-1) during TGS, after the α-blockade CBV (Δ0.98 ± cm s-1) and CVCi (Δ-0.03 ± 0.06 cm s-1 mmHg-1) response to TGS did not change.

CONCLUSION

Coronary circulation increases during sympathetic stimulation even with a decrease in heart rate.

Increased nitric oxide availability worsens the cardiac performance during early re-perfusion period in adult rats

OBJECTIVES

Re-perfusion is the standard therapy for acute myocardial infarction, despite the associated pathologies that may contribute to irreversible myocardial injury. The present study aims to clarify the alterations in cardiac activities in response to experimental cardiac ischemic arrest followed by re-perfusion in isolated hearts perfused with nitric oxide (NO) donor, l-arginine, or NO inhibitor, Nω-Nitro-l-arginine methyl ester hydrochloride (l-NAME), to shed light on the possible role of NO in the re-perfusion process.

METHODS

Hearts isolated from adult Wistar rats were studied on Langendorff preparation under basal conditions and during 30 min re-perfusion following 30 min of total global ischemia. Rats were randomly divided into three groups; control and l-arginine or l-NAME infused heart groups. Cardiac tissue content of malondialdhyde, catalase and nitrite was also measured.

RESULTS

Compared to the control group, both l-arginine and l-NAME infused hearts showed increased basal chronotropy and myocardial flow rate. Following ischemia and during the whole period of re-perfusion, the three groups demonstrated significant deterioration in the inotropic activity and compromised myocardial flow rate. l-arginine infused hearts revealed depressed inotropy and chronotropy, weak systolic and diastolic functions with compromised myocardial flow at early 5 min of re-perfusion, yet with significantly higher myocardial flow rate by the end of re-perfusion.

CONCLUSIONS

Reducing NO availability by l-NAME revealed mild impact on the ischemia re-perfusion induced contractile dysfunction, whereas excess NO worsens cardiac performance at the early re-perfusion period.

Nanostructured Lipid Carriers to Enhance the Bioavailability and Solubility of Ranolazine: Statistical Optimization and Pharmacological Evaluations

Chronic stable angina pectoris is the primary indication for ranolazine (RZ), an anti-anginal drug. The drug has an anti-ischemic action that is unaffected by either blood pressure or heart rate. Due to the first-pass effect, the drug has a reduced bioavailability of 35 to 50%. The study emphasized developing a novel transdermal drug delivery system of nanostructured lipid carriers (NLCs) for delivering RZ. Many pharmaceutical companies employ lipid nanoparticles as biocompatible carriers for medicinal, cosmetic, and biochemical uses. These carriers are appropriate for many applications, such as topical, transdermal, parenteral, pulmonary, and oral administration, because of the large variety of lipids and surfactants that are readily available for manufacturing. RZ NLCs were made using high-pressure homogenization. Statistical analysis was utilized to find the best formula by varying the concentrations of Precirol ATO 5 (X1), oleic acid (X2), and Tween 80 (X3). Variables such as entrapment effectiveness (EE) (Y1), particle size (Y2), polydispersity index (PDI) (Y3), and zeta potential (Y4) were tested. A variety of tests were performed on the new formulation to ascertain how well it would be absorbed in the body. These tests included in vivo absorption studies, skin permeability assessments, in vitro drug release assessments, and physicochemical analyses. The particle size of RZ-NLCs was shown to be very small (118.4 ± 5.94 nm), with improved EE (88.39 ± 3.1%) and low ZP and PDI (-41.91 ± 0.38 and 0.118 ± 0.028). SEM and TEM analysis confirmed the structure of the NLCs and showed a smooth, spherical surface. Improved RZ-NLCs were used to create NLC gel, which was then tested for elasticity both physically and rheologically. The formulation's elasticity was investigated. Optimized RZ-NLCs and NLCG were found to have transdermal fluxes of 48.369 g/cm2/h and 38.383 g/cm2/h, respectively. These results showed that the transdermal delivery of RZ distribution through NLC's transdermal gel had more significant potential. According to in vivo experiments, the drug's bioavailability in Wistar rats increased when it was delivered through NLCs. The findings demonstrated that NLCs loaded with RZ successfully transported the RZ to the designated site with no interruptions and that a quadratic connection existed between the independent and dependent variables.

Biomechanics and clinical outcomes of various conduit configurations in valve sparing aortic root replacement

Background

Several conduit configurations, such as straight graft (SG), Valsalva graft (VG), anticommissural plication (ACP), and the Stanford modification (SMOD) technique, have been described for the valve-sparing aortic root replacement (VSARR) procedure. Prior ex vivo studies have evaluated the impact of conduit configurations on root biomechanics, but the mock coronary artery circuits used could not replicate the physical properties of native coronary arteries. Moreover, the individual leaflet's biomechanics, including the fluttering phenomenon, were unclear.

Methods

Porcine aortic roots with coronary arteries were explanted (n=5) and underwent VSARR using SG, VG, ACP, and SMOD for evaluation in an ex vivo left heart flow loop simulator. Additionally, 762 patients who underwent VSARR from 1993 through 2022 at our center were retrospectively reviewed. Analysis of variance was performed to evaluate differences between different conduit configurations, with post hoc Tukey's correction for pairwise testing.

Results

SG demonstrated lower rapid leaflet opening velocity compared with VG (P=0.001) and SMOD (P=0.045) in the left coronary cusp (LCC), lower rapid leaflet closing velocity compared with VG (P=0.04) in the right coronary cusp (RCC), and lower relative opening force compared with ACP (P=0.04) in the RCC. The flutter frequency was lower in baseline compared with VG (P=0.02) and in VG compared with ACP (P=0.03) in the LCC. Left coronary artery mean flow was higher in SG compared with SMOD (P=0.02) and ACP (P=0.05). Clinically, operations using SG compared with sinus-containing graft was associated with shorter aortic cross-clamp and cardiopulmonary bypass time (P<0.001, <0.001).

Conclusions

SG demonstrated hemodynamics and biomechanics most closely recapitulating those from the native root with significantly shorter intraoperative times compared with repair using sinus-containing graft. Future in vivo validation studies as well as correlation with comprehensive, comparative clinical study outcomes may provide additional invaluable insights regarding strategies to further enhance repair durability.

Renal Oxygen Demand and Nephron Function: Is Glucose a Friend or Foe?

The kidneys and heart work together to balance the body's circulation, and although their physiology is based on strict inter dependence, their performance fulfills different aims. While the heart can rapidly increase its own oxygen consumption to comply with the wide changes in metabolic demand linked to body function, the kidneys physiology are primarily designed to maintain a stable metabolic rate and have a limited capacity to cope with any steep increase in renal metabolism. In the kidneys, glomerular population filters a large amount of blood and the tubular system has been programmed to reabsorb 99% of filtrate by reabsorbing sodium together with other filtered substances, including all glucose molecules. Glucose reabsorption involves the sodium-glucose cotransporters SGLT2 and SGLT1 on the apical membrane in the proximal tubular section; it also enhances bicarbonate formation so as to preserve the acid-base balance. The complex work of reabsorption in the kidney is the main factor in renal oxygen consumption; analysis of the renal glucose transport in disease states provides a better understanding of the renal physiology changes that occur when clinical conditions alter the neurohormonal response leading to an increase in glomerular filtration pressure. In this circumstance, glomerular hyperfiltration occurs, imposing a higher metabolic demand on kidney physiology and causing progressive renal impairment. Albumin urination is the warning signal of renal engagement over exertion and most frequently heralds heart failure development, regardless of disease etiology. The review analyzes the mechanisms linked to renal oxygen consumption, focusing on sodium-glucose management.

Impact of TAVR on coronary artery hemodynamics using clinical measurements and image-based patient-specific in silico modeling

In recent years, transcatheter aortic valve replacement (TAVR) has become the leading method for treating aortic stenosis. While the procedure has improved dramatically in the past decade, there are still uncertainties about the impact of TAVR on coronary blood flow. Recent research has indicated that negative coronary events after TAVR may be partially driven by impaired coronary blood flow dynamics. Furthermore, the current technologies to rapidly obtain non-invasive coronary blood flow data are relatively limited. Herein, we present a lumped parameter computational model to simulate coronary blood flow in the main arteries as well as a series of cardiovascular hemodynamic metrics. The model was designed to only use a few inputs parameters from echocardiography, computed tomography and a sphygmomanometer. The novel computational model was then validated and applied to 19 patients undergoing TAVR to examine the impact of the procedure on coronary blood flow in the left anterior descending (LAD) artery, left circumflex (LCX) artery and right coronary artery (RCA) and various global hemodynamics metrics. Based on our findings, the changes in coronary blood flow after TAVR varied and were subject specific (37% had increased flow in all three coronary arteries, 32% had decreased flow in all coronary arteries, and 31% had both increased and decreased flow in different coronary arteries). Additionally, valvular pressure gradient, left ventricle (LV) workload and maximum LV pressure decreased by 61.5%, 4.5% and 13.0% respectively, while mean arterial pressure and cardiac output increased by 6.9% and 9.9% after TAVR. By applying this proof-of-concept computational model, a series of hemodynamic metrics were generated non-invasively which can help to better understand the individual relationships between TAVR and mean and peak coronary flow rates. In the future, tools such as these may play a vital role by providing clinicians with rapid insight into various cardiac and coronary metrics, rendering the planning for TAVR and other cardiovascular procedures more personalized.

Poorly controlled hypertension is associated with increased coronary myogenic tone in patients undergoing cardiac surgery with cardiopulmonary bypass

OBJECTIVE

Cardioplegia and cardiopulmonary bypass dysregulate coronary vasomotor tone, which can be further affected by common comorbidities in patients undergoing cardiac surgery. This study investigates differences in coronary myogenic tone and vasomotor responses to phenylephrine before and after cardioplegia and cardiopulmonary bypass based on hypertension history.

METHODS

Coronary arterioles before and after cardioplegia and cardiopulmonary bypass were dissected from atrial tissue samples in patients with no hypertension, well-controlled hypertension, or uncontrolled hypertension, as determined by documented history of hypertension, antihypertensive agent use, and clinical blood pressure measurements averaged over 1 year. Myogenic tone in response to stepwise increases in intraluminal pressure was studied between pressure steps. Microvascular reactivity in response to phenylephrine was assessed via vessel myography. Protein expression was measured with immunoblotting.

RESULTS

Coronary myogenic tone was significantly increased in the uncontrolled hypertension group compared with the no hypertension and well-controlled hypertension groups before cardioplegia and cardiopulmonary bypass at higher intraluminal pressures, and after cardioplegia and cardiopulmonary bypass across all intraluminal pressures (P < .05). Contractile responses to phenylephrine were significantly enhanced in patients in the uncontrolled hypertension group compared with the well-controlled hypertension group before cardioplegia and cardiopulmonary bypass, and in the uncontrolled hypertension group compared with the no hypertension and well-controlled hyertension groups after cardioplegia and cardiopulmonary bypass (P < .05). There were no differences in myogenic tone or phenylephrine-induced reactivity between the no hypertension and well-controlled hypertension groups (P > .05). There was increased expression of phosphorylated protein kinase C alpha in the uncontrolled hypertension group after cardiopulmonary bypass compared with before cardiopulmonary bypass and increased phosphorylated extracellular signal-regulated kinase 1/2 in the uncontrolled hypertension compared with the no hypertension group after cardiopulmonary bypass (P < .05).

CONCLUSIONS

Uncontrolled hypertension is associated with increased coronary myogenic tone and vasoconstrictive response to phenylephrine that persists after cardioplegia and cardiopulmonary bypass.

Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA): Focus on Coronary Microvascular Dysfunction and Genetic Susceptibility

Among the most common causes of death worldwide, ischemic heart disease (IHD) is recognized to rank first. Even if atherosclerotic disease of the epicardial arteries is known as the leading cause of IHD, the presence of myocardial infarction with non-obstructive coronary artery disease (MINOCA) is increasingly recognized. Notwithstanding the increasing interest, MINOCA remains a puzzling clinical entity that can be classified by distinguishing different underlying mechanisms, which can be divided into atherosclerotic and non-atherosclerotic. In particular, coronary microvascular dysfunction (CMD), classifiable in non-atherosclerotic mechanisms, is a leading factor for the pathophysiology and prognosis of patients with MINOCA. Genetic susceptibility may have a role in primum movens in CMD. However, few results have been obtained for understanding the genetic mechanisms underlying CMD. Future studies are essential in order to find a deeper understanding of the role of multiple genetic variants in the genesis of microcirculation dysfunction. Progress in research would allow early identification of high-risk patients and the development of pharmacological, patient-tailored strategies. The aim of this review is to revise the pathophysiology and underlying mechanisms of MINOCA, focusing on CMD and actual knowledge about genetic predisposition to it.

Investigation of the Relationship Between Triglycerides-Glucose İndex and Coronary Slow Flow: A Retrospective Case-Control Study

BACKGROUND

Coronary slow flow (CSF) refers to delayed distal vessel opacification in the absence of epicardial coronary artery stenosis. The etiopathogenic mechanism of CSF is still unclear.

OBJECTIVES

This study investigates the relationship between CSF and the triglyceride-glucose (TyG) index.

METHODS

The study sample consisted of 118 CSF patients and 105 patients with normal coronary flow (NCF). The coronary flow rate was measured via the Thrombolysis in Myocardial Infarction (TIMI) frame count (TFC) method in all patients. The TyG index was calculated as the logarithm of the [fasting triglyceride (mg/dL)×fasting glucose (mg/dL)]/2 value. A significance level of < 0.05 was adopted as statistically significant.

RESULTS

The TyG index, low-density lipoprotein (LDL), body mass index (BMI), neutrophil-to-lymphocyte ratio (NLR) and TFC values, male ratio, and the ratio of smokers were higher, whereas high-density lipoprotein (HDL) levels were significantly lower in the CSF group compared to the NCF group (p<0,05). The correlation analysis revealed that CSF was significantly correlated with TyG index, BMI, NLR, and HDL values. The strongest of these correlations was between CSF and TyG index (r= 0.57, p<0.001). Additionally, the multivariate analysis revealed that TyG index, BMI, NLR ratio, and male gender were independent predictors for CSF (p<0.05). Receiver operating characteristic (ROC) curve analysis indicated that a cut-off value of ≥ 9.28 for the TyG index predicted CSF with a sensitivity of 78% and a specificity of 78.1% [Area under the curve (AUC): 0.868 and 95% Confidence Interval (CI): 0.823-0.914].

CONCLUSION

The findings of this study revealed a very strong relationship between CSF and TyG index.

Effect of Left Ventricular Unloading by Pump Speed Adjustment on Myocardial Flow in Continuous-flow Left Ventricular Assist Device Patients

Resting myocardial blood flow (MBF) and myocardial flow reserve (MFR) are reduced in heart failure (HF) patients supported by pulsatile left ventricular assist devices (LVADs). The effect of continuous-flow (CF) physiology on these parameters is underexplored in CF-LVAD patients. We investigated the impact of CF-LVADs on resting MBF and MFR under two left ventricular (LV) loading conditions. Nine HeartMate II patients (42 ± 12 years, 100% male) on support for 370 ± 281 days were enrolled. Results were compared with 9 HF patients (58 ± 13 years, 67% male, LV ejection fraction 27 ± 9%) and 10 healthy volunteers (56 ± 10 years, 20% male). CF-LVAD patients underwent transthoracic echocardiography with ramp study. MBF and MFR were measured utilizing positron emission/computed tomography imaging under two LV loading conditions: "high-speed" (HS), promoting aortic valve (AV) closure and LV unloading; "low-speed" (LS), promoting AV opening and LV loading. Global resting MBF was similar in HS, LS, HF, and healthy: 0.8 ± 0.3, 0.7 ± 0.3, 0.7 ± 0.1, 0.9 ± 0.2 ml/min/g, respectively; p = NS. HS global MFR was reduced compared with LS and HF: 1.6 ± 0.6 versus 1.9 ± 0.5, p = 0.004; 1.6 ± 0.6 versus 2.4 ± 0.5, p = 0.01, respectively. HS regional MFR was reduced compared with LS in the left anterior descending (1.7 ± 0.7 vs. 2.0 ± 0.6, p = 0.027) and left circumflex (1.8 ± 0.7 vs. 2.2 ± 0.9, p = 0.008), but not in right coronary artery (1.7 ± 0.7 vs. 1.7 ± 0.6, p = 0.76). Resting MBF is preserved among CF-LVAD patients and is similar to HF and healthy. Promoting LV ventricular unloading with higher speed was associated with lower global and regional left coronary MFR, while right coronary MFR did not change.

Protection against Ischemic Heart Disease: A Joint Role for eNOS and the KATP Channel

Genetic susceptibility may influence ischemic heart disease (IHD) predisposition and affect coronary blood flow (CBF) regulation mechanisms. The aim of this study was to investigate the association among single nucleotide polymorphisms (SNPs) of genes encoding for proteins involved in CBF regulation and IHD. A total of 468 consecutive patients were enrolled and divided into three groups according to coronary angiography and intracoronary functional tests results: G1, patients with coronary artery disease (CAD); G2, patients with coronary microvascular dysfunction (CMD); and G3, patients with angiographic and functionally normal coronary arteries. A genetic analysis of the SNPs rs5215 of the potassium inwardly rectifying channel subfamily J member 11 (KCNJ11) gene and rs1799983 of the nitric oxide synthase 3 (NOS3) gene, respectively encoding for the Kir6.2 subunit of ATP sensitive potassium (K_ATP) channels and nitric oxide synthase (eNOS), was performed on peripheral whole blood samples. A significant association of rs5215_G/G of KCNJ11 and rs1799983_T/T of NOS3 genes was detected in healthy controls compared with CAD and CMD patients. Based on univariable and multivariable analyses, the co-presence of rs5215_G/G of KCNJ11 and rs1799983_T/T of NOS3 may represent an independent protective factor against IHD, regardless of cardiovascular risk factors. This study supports the hypothesis that SNP association may influence the crosstalk between eNOS and the K_ATP channel that provides a potential protective effect against IHD.