Optimization of Absolute Coronary Blood Flow Measurements to Assess Microvascular Function: In Vivo Validation of Hyperemia and Higher Infusion Speeds

BACKGROUND

Reliable assessment of coronary microvascular function is essential. Techniques to measure absolute coronary blood flow are promising but need validation. The objectives of this study were: first, to validate the potential of saline infusion to generate maximum hyperemia in vivo. Second, to validate absolute coronary blood flow measured with continuous coronary thermodilution at high (40-50 mL/min) infusion speeds and asses its safety.

METHODS

Fourteen closed-chest sheep underwent absolute coronary blood flow measurements with increasing saline infusion speeds at different dosages under general anesthesia. An additional 7 open-chest sheep underwent these measurements with epicardial Doppler flow probes. Coronary flows were compared with reactive hyperemia after 45 s of coronary occlusion.

RESULTS

Twenty milliliters per minute of saline infusion induced a significantly lower hyperemic coronary flow (140 versus 191 mL/min; P=0.0165), lower coronary flow reserve (1.82 versus 3.21; P≤0.0001), and higher coronary resistance (655 versus 422 woods units; P=0.0053) than coronary occlusion. On the other hand, 30 mL/min of saline infusion resulted in hyperemic coronary flow (196 versus 192 mL/min; P=0.8292), coronary flow reserve (2.77 versus 3.21; P=0.1107), and coronary resistance (415 versus 422 woods units; P=0.9181) that were not different from coronary occlusion. Hyperemic coronary flow was 40.7% with 5 mL/min, 40.8% with 10 mL/min, 73.1% with 20 mL/min, 102.3% with 30 mL/min, 99.0% with 40 mL/min, and 98.0% with 50 mL/min of saline infusion when compared with postocclusive hyperemic flow. There was a significant bias toward flow overestimation (Bland-Altman: bias±SD, -73.09±30.52; 95% limits of agreement, -132.9 to -13.27) with 40 to 50 mL/min of saline. Occasionally, ischemic changes resulted in ventricular fibrillation (9.5% with 50 mL/min) at higher infusion rates.

CONCLUSIONS

Continuous saline infusion of 30 mL/min but not 20 mL/min induced maximal hyperemia. Absolute coronary blood flow measured with saline infusion speeds of 40 to 50 mL/min was not accurate and not safe.

p53 Acetylation Exerts Critical Roles in Pressure Overload-Induced Coronary Microvascular Dysfunction and Heart Failure in Mice

BACKGROUND

Coronary microvascular dysfunction (CMD) has been shown to contribute to cardiac hypertrophy and heart failure (HF) with preserved ejection fraction. At this point, there are no proven treatments for CMD.

METHODS

We have shown that histone acetylation may play a critical role in the regulation of CMD. By using a mouse model that replaces lysine with arginine at residues K98, K117, K161, and K162R of p53 (p534KR), preventing acetylation at these sites, we test the hypothesis that acetylation-deficient p534KR could improve CMD and prevent the progression of hypertensive cardiac hypertrophy and HF. Wild-type and p534KR mice were subjected to pressure overload by transverse aortic constriction to induce cardiac hypertrophy and HF.

RESULTS

Echocardiography measurements revealed improved cardiac function together with a reduction of apoptosis and fibrosis in p534KR mice. Importantly, myocardial capillary density and coronary flow reserve were significantly improved in p534KR mice. Moreover, p534KR upregulated the expression of cardiac glycolytic enzymes and Gluts (glucose transporters), as well as the level of fructose-2,6-biphosphate; increased PFK-1 (phosphofructokinase 1) activity; and attenuated cardiac hypertrophy. These changes were accompanied by increased expression of HIF-1α (hypoxia-inducible factor-1α) and proangiogenic growth factors. Additionally, the levels of SERCA-2 were significantly upregulated in sham p534KR mice, as well as in p534KR mice after transverse aortic constriction. In vitro, p534KR significantly improved endothelial cell glycolytic function and mitochondrial respiration and enhanced endothelial cell proliferation and angiogenesis. Similarly, acetylation-deficient p534KR significantly improved coronary flow reserve and rescued cardiac dysfunction in SIRT3 (sirtuin 3) knockout mice.

CONCLUSIONS

Our data reveal the importance of p53 acetylation in coronary microvascular function, cardiac function, and remodeling and may provide a promising approach to improve hypertension-induced CMD and to prevent the transition of cardiac hypertrophy to HF.

Efficacy of catheter-based drug delivery in a hybrid in vitro model of cardiac microvascular obstruction with porcine microthrombi

Microvascular obstruction (MVO) often occurs in ST-elevation myocardial infarction (STEMI) patients after percutaneous coronary intervention (PCI). Diagnosis and treatment of MVO lack appropriate and established procedures. This study focused on two major points by using an in vitro multiscale flow model, which comprised an aortic root model with physiological blood flow and a microfluidic model of the microcirculation with vessel diameters down to 50 μm. First, the influence of porcine microthrombi (MT), injected into the fluidic microchip, on perfusion was investigated. We found that only 43 % of all injected MT were fully occlusive. Second, it could also be shown that the maximal concentration of a dye (representing therapeutic agent) during intracoronary infusion could be increased on average by 58 % , when proximally occluding the coronary artery by a balloon during drug infusion. The obtained results and insights enhance the understanding of perfusion in MVO-affected microcirculation and could lead to improved treatment methods for MVO patients.

ChaMP-CMD: A Phenotype-Blinded, Randomized Controlled, Cross-Over Trial

BACKGROUND

Angina with nonobstructive coronary arteries is a common condition for which no effective treatment has been established. We hypothesized that the measurement of coronary flow reserve (CFR) allows identification of patients with angina with nonobstructive coronary arteries who would benefit from anti-ischemic therapy.

METHODS

Patients with angina with nonobstructive coronary arteries underwent blinded invasive CFR measurement and were randomly assigned to receive 4 weeks of amlodipine or ranolazine. After a 1-week washout, they crossed over to the other drug for 4 weeks; final assessment was after the cessation of study medication for another 4 weeks. The primary outcome was change in treadmill exercise time, and the secondary outcome was change in Seattle Angina Questionnaire summary score in response to anti-ischemic therapy. Analysis was on a per protocol basis according to the following classification: coronary microvascular disease (CMD group) if CFR<2.5 and reference group if CFR≥2.5. The study protocol was registered before the first patient was enrolled (International Standard Randomised Controlled Trial Number: ISRCTN94728379).

RESULTS

Eighty-seven patients (61±8 years of age; 62% women) underwent random assignment (57 CMD group and 30 reference group). Baseline exercise time and Seattle Angina Questionnaire summary scores were similar between groups. The CMD group had a greater increment (delta) in exercise time than the reference group in response to both amlodipine (difference in delta, 82 s [95% CI, 37-126 s]; P<0.001) and ranolazine (difference in delta, 68 s [95% CI, 21-115 s]; P=0.005). The CMD group reported a greater increment (delta) in Seattle Angina Questionnaire summary score than the reference group in response to ranolazine (difference in delta, 7 points [95% CI, 0-15]; P=0.048), but not to amlodipine (difference in delta, 2 points [95% CI, -5 to 8]; P=0.549).

CONCLUSIONS

Among phenotypically similar patients with angina with nonobstructive coronary arteries, only those with an impaired CFR derive benefit from anti-ischemic therapy. These findings support measurement of CFR to diagnose and guide management of this otherwise heterogeneous patient group.

[Computed tomography in cardiology: history and perspectives]

The review article highlights the main stages of the formation of computed tomography (CT) as a key method used in modern cardiology. The progress of CT scanners is directly related to the increase in the number of detectors, and thus, with an increase in the number of simultaneously collected projections. Modern developments and future technologies in the field of further development of the technique, including CT angiography and other new methods for assessing coronary blood flow, are discussed. The use of artificial intelligence technologies may make it possible to improve and accelerate the interpretation of the resulting images in the future, especially if it is economically justified.

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.

Detailed Morphometric Analysis on Left Coronary Artery in the Population of North-East India

Introduction The left ventricle, the cardiac chamber responsible for blood supply to the whole of systemic vasculature, receives most of its blood supply from the left coronary arteries (LCAs). Atherosclerosis of these vessels leading to myocardial infarction is a leading cause of death. Several invasive diagnostic or therapeutic coronary interventions are available for such patients. Just like any vascular procedure, a prior comprehensive knowledge of the dimensions of these vessels and their branching pattern is essential to perform these procedures uneventfully. No previous study in the population of North-Eastern India documents the population-specific reference for morphometric values of left coronary arteries and their anatomic variations. So, this study aims to fill up this lacuna. Methods This study was conducted in the Department of Anatomy in collaboration with the Catheterization Lab, Department of Cardiology, North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences (NEIGRIHMS), Shillong. Coronary angiograms (CAG) of 100 subjects - 38 females and 62 males - were obtained from the Cardiac Catheterization Lab. Coronary angiograms were studied for the normal variant anatomy and morphometry of the LCAs - the left main coronary artery (LMCA), left anterior descending (LAD), and left circumflex (LCX).  Results The mean length and luminal diameter of LMCA were found to be 9.13±3.23 mm and 4.38±0.58 mm, respectively. The mean length of LAD and LCX were 109.46±14.49 mm and 66.27±11.56 mm, respectively. Ramus intermedius was present in 32% of the subjects, whereas the remaining subjects had bifurcations of LMCA. We also found that 86% of patients had "wrap-around LAD", while in 11% of our subjects, LAD failed to reach the apex. Diagonal branches originating from LAD were single, duplicated, and multiple in 14%, 62%, and 24% respectively. The marginal branches were found to be single, double, and multiple in 20%, 51%, and 29% respectively. Conclusion This study establishes a baseline reference on morphometry of the left coronary artery specific to the population of North-East India. This study may be of assistance to radiologists and cardiologists when performing procedures on the left coronary arteries in the population of North-Eastern India, with respect to the prevalence of anatomic variations.

Ranolazine improved left ventricular diastolic functions and ventricular repolarization indexes in patients with coronary slow flow

Introduction

Coronary slow flow (CSF) is a condition commonly encountered during angiography. Recent studies have shown the adverse effects of CSF on left ventricular diastolic functions. CSF reportedly increases the novel ventricular repolarization parameters. Ranolazine is a preparation with a prominent anti-anginal activity that has positive effects on anti-arrhythmic and diastolic parameters. In this context, this study was carried out to investigate the effects of ranolazine on left ventricular diastolic functions and repolarization in patients with CSF.

Material and methods

Forty-six patients with CSF and 29 control subjects were included in the patient and control groups, respectively. Both groups received ranolazine for one month and were evaluated using 12-lead electrocardiography, conventional echocardiography, and tissue Doppler imaging at the baseline and after one month of ranolazine treatment.

Results

Corrected P, QT dispersion, and Tp-e interval values were significantly higher in the patient group than in the control group. There was a significant decrease in isovolumic relaxation time (IVRT) and deceleration time (DT) values after the ranolazine treatment compared to the baseline values in the patient group but not the control group. A significant increase was observed in the mean E and A velocities and the mean E/A ratio after the ranolazine treatment compared to the baseline values in the patient group. Additionally, there was a significant difference between the Tp-e interval and corrected P dispersion values measured after the ranolazine treatment compared to the baseline values in the patient group but not in the control group.

Conclusion

This study's findings demonstrated that ranolazine positively affected impaired diastolic functions and repolarization parameters, particularly in patients with CSF.

Myocardial Flow Reserve, an Independent Prognostic Marker of All-Cause Mortality Assessed by 82Rb PET Myocardial Perfusion Imaging: A Danish Multicenter Study

BACKGROUND

Rubidium-82 positron emission tomography (82Rb PET) myocardial perfusion imaging is used in clinical practice to quantify regional perfusion defects. Additionally, 82Rb PET provides a measure of absolute myocardial flow reserve (MFR), describing the vasculature state of health. We assessed whether 82Rb PET-derived MFR is associated with all-cause mortality independently of the extent of perfusion defects.

METHODS

We conducted a multicenter clinical registry-based study of patients undergoing 82Rb PET myocardial perfusion imaging on suspicion of chronic coronary syndromes. Patients were followed up in national registries for the primary outcome of all-cause mortality. Global MFR ≤2 was considered reduced.

RESULTS

Among 7169 patients studied, 38.1% were women, the median age was 69 (IQR, 61-76) years, and 39.0% had MFR ≤2. A total of 667 (9.3%) patients died during a median follow-up of 3.1 (IQR, 2.6-4.0) years, more in patients with MFR ≤2 versus MFR >2 (15.7% versus 5.2%; P<0.001). MFR ≤2 was associated with all-cause mortality across subgroups defined by the extent of perfusion defects (all P<0.05). In a Cox survival regression model adjusting for sex, age, comorbidities, kidney function, left ventricular ejection fraction, and perfusion defects, MFR ≤2 was a robust predictor of mortality with a hazard ratio of 1.62 (95% CI, 1.31-2.02; P<0.001). Among patients with no reversible perfusion defects (n=3101), MFR ≤2 remained strongly associated with mortality (hazard ratio, 1.86 [95% CI, 1.26-2.73]; P<0.01). The prognostic value of impaired MFR was similar for cardiac and noncardiac death.

CONCLUSIONS

MFR ≤2 predicts all-cause mortality independently of the extent of perfusion defects. Our results support the inclusion of MFR when assessing the prognosis of patients suspected of chronic coronary syndromes.

Coronary Reactivity Assessment Is Associated With Lower Health Care-Associated Costs in Patients Presenting With Angina and Nonobstructive Coronary Artery Disease

BACKGROUND

The financial burden linked to the diagnosis and treatment of patients with chest pain on the health care system is considerable. Angina and nonobstructive coronary artery disease (ANOCA) is common, associated with adverse cardiovascular events, and may lead to repeat testing or hospitalizations. Diagnostic certainty can be achieved in patients with ANOCA using coronary reactivity testing (CRT); however, its financial effect on the patient has not been studied. Our goal was to assess the effect of CRT on health care-related cost in patients with ANOCA.

METHODS

Patients with ANOCA who underwent diagnostic coronary angiography (CAG) and CRT (CRT group) were matched to controls who had similar presentation but only underwent a CAG without CRT (CAG group). Standardized inflation-adjusted costs were collected and compared between the 2 groups on an annual basis for 2 years post the index date (CRT or CAG).

RESULTS

Two hundred seven CRT and 207 CAG patients were included in the study with an average age of 52.3±11.5 years and 76% females. The total cost was significantly higher in the CAG group as compared with the CRT group ($37 804 [$26 933-$48 674] versus $13 679 [$9447-$17 910]; P<0.001). When costs are itemized and divided based on the Berenson-Eggers Type of Service categorization, the largest cost difference occurred in imaging (any type, including CAG; P<0.001), procedures (eg, percutaneous coronary intervention/coronary artery bypass grafting/thrombectomy) (P=0.001), and test (eg, blood tests, EKG; P<0.001).

CONCLUSIONS

In this retrospective observational study, assessment of CRT in patients with ANOCA was associated with significantly reduced annual total costs and health care utilization. Therefore, the study may support the integration of CRT into clinical practice.

Cerebral and coronary circulation

In recent years, several works have addressed the problem of modeling blood flow phenomena in veins, as a response to increasing interest in modeling pathological conditions occurring in the venous network and their connection with the rest of the circulatory system. In this context, one-dimensional models have proven to be extremely efficient in delivering predictions in agreement with in-vivo observations. Pursuing the increase of anatomical accuracy and its connection to physiological principles in haemodynamics simulations, the main aim of this work is to describe a novel closed-loop Anatomically-Detailed Arterial-Venous Network (ADAVN) model. An extremely refined description of the arterial network consisting of 2,185 arterial vessels is coupled to a novel venous network featuring high level of anatomical detail in cerebral and coronary vascular territories. The entire venous network comprises 189 venous vessels, 79 of which drain the brain and 14 are coronary veins. Fundamental physiological mechanisms accounting for the interaction of brain blood flow with the cerebro-spinal fluid and of the coronary circulation with the cardiac mechanics are considered. Several issues related to the coupling of arterial and venous vessels at the microcirculation level are discussed in detail. Numerical simulations are compared to patient records published in the literature to show the descriptive capabilities of the model. Furthermore, a local sensitivity analysis is performed, evidencing the high impact of the venous circulation on main cardiovascular variables.

Coronary Microvascular Disease in Contemporary Clinical Practice

Coronary microvascular disease (CMD) causes myocardial ischemia in a variety of clinical scenarios. Clinical practice guidelines support routine testing for CMD in patients with ischemia with nonobstructive coronary artery disease. Invasive testing to identify CMD requires Doppler or thermodilution measures of flow to determine the coronary flow reserve and measures of microvascular resistance. Acetylcholine coronary reactivity testing identifies concomitant endothelial dysfunction, microvascular spasm, or epicardial coronary spasm. Comprehensive testing may improve symptoms, quality of life, and patient satisfaction by establishing a diagnosis and guiding-targeted medical therapy and lifestyle measures. Beyond ischemia with nonobstructive coronary artery disease, testing for CMD may play a role in patients with acute myocardial infarction, angina following coronary revascularization, heart failure with preserved ejection fraction, Takotsubo syndrome, and after heart transplantation. Additional education and provider awareness of CMD and its role in cardiovascular disease is needed to improve patient-centered outcomes of ischemic heart disease.

Effects of atorvastatin and rosuvastatin on dysfunctional coronary circulation in patients with ST-segment elevation myocardial infarction

OBJECTIVE

Evidence of therapy for dysfunctional coronary circulation in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI) is limited. This study was performed to compare the effects of atorvastatin and rosuvastatin on dysfunctional coronary circulation.

METHODS

This retrospective study enrolled 597 consecutive patients with STEMI who underwent pPCI in 3 centers from June 2016 to December 2019. Dysfunctional coronary circulation was defined by the thrombolysis in myocardial infarction (TIMI) grade and the TIMI myocardial perfusion grade (TMPG). Logistic regression analysis was used to evaluate the impact of different statin types on dysfunctional coronary circulation.

RESULTS

The incidence of TIMI no/slow reflow did not differ between the two groups, but the incidence of TMPG no/slow reflow was significantly lower in the atorvastatin than rosuvastatin group (44.58% vs. 57.69%, respectively). After multivariate adjustment, the odds ratio with 95% confidence interval of rosuvastatin was 1.72 (1.17-2.52) for after pretreatment TMPG no/slow reflow and 1.73 (1.16-2.58) for after stenting TMPG no/slow reflow. Atorvastatin and rosuvastatin showed no significant differences in clinical outcomes during hospitalization.

CONCLUSIONS

Compared with rosuvastatin, atorvastatin was associated with better coronary microcirculatory perfusion in patients with STEMI who underwent pPCI.

PET for Detection and Reporting Coronary Microvascular Dysfunction: A JACC: Cardiovascular Imaging Expert Panel Statement

Angina pectoris and dyspnea in patients with normal or nonobstructive coronary vessels remains a diagnostic challenge. Invasive coronary angiography may identify up to 60% of patients with nonobstructive coronary artery disease (CAD), of whom nearly two-thirds may, in fact, have coronary microvascular dysfunction (CMD) that may account for their symptoms. Positron emission tomography (PET) determined absolute quantitative myocardial blood flow (MBF) at rest and during hyperemic vasodilation with subsequent derivation of myocardial flow reserve (MFR) affords the noninvasive detection and delineation of CMD. Individualized or intensified medical therapies with nitrates, calcium-channel blockers, statins, angiotensin-converting enzyme inhibitors, angiotensin II type 1-receptor blockers, beta-blockers, ivabradine, or ranolazine may improve symptoms, quality of life, and outcome in these patients. Standardized diagnosis and reporting criteria for ischemic symptoms caused by CMD are critical for optimized and individualized treatment decisions in such patients. In this respect, it was proposed by the cardiovascular council leadership of the Society of Nuclear Medicine and Molecular Imaging to convene thoughtful leaders from around the world to serve as an independent expert panel to develop standardized diagnosis, nomenclature and nosology, and cardiac PET reporting criteria for CMD. This consensus document aims to provide an overview of the pathophysiology and clinical evidence of CMD, its invasive and noninvasive assessment, standardization of PET-determined MBFs and MFR into "classical" (predominantly related to hyperemic MBFs) and "endogen" (predominantly related to resting MBF) normal coronary microvascular function or CMD that may be critical for diagnosis of microvascular angina, subsequent patient care, and outcome of clinical CMD trials.

Integrated control of coronary blood flow in exercising swine by adenosine, nitric oxide, and KATP channels

The interplay of mechanisms regulating coronary blood flow (CBF) remains incompletely understood. Previous studies in dogs indicated that CBF regulation by K_ATP channels, adenosine, and nitric oxide (NO) follows a nonlinear redundancy design and fully accounted for exercise-induced coronary vasodilation. Conversely, in swine, these mechanisms appear to regulate CBF in a linear additive fashion with considerable exercise-induced vasodilation remaining when all three mechanisms are inhibited. A direct comparison between these studies is hampered by the different doses and administration routes (intravenous vs. intracoronary) of drugs inhibiting these mechanisms. Here, we investigated the role of K_ATP channels, adenosine, and NO in CBF regulation in swine using identical drug regimen as previously employed in dogs. Instrumented swine were exercised on a motor-driven treadmill, before and after blockade of K_ATP channels (glibenclamide, 50 µg/kg/min ic) and combination of inhibition of NO synthase (N^ω-nitro-l-arginine, NLA, 1.5 mg/kg ic) and adenosine receptors (8-phenyltheophylline, 8PT, 5 mg/kg iv) or their combination NLA + 8PT + glibenclamide. Glibenclamide and NLA + 8PT each produced coronary vasoconstriction both at rest and during exercise, whereas the combination of NLA + 8PT + glibenclamide resulted in a small further coronary vasoconstriction compared with NLA + 8PT that was, however, less than the sum of the vasoconstriction produced by NLA + 8PT and glibenclamide, each. Thus, in contrast to previous observations in the dog, 1) the coronary vasoconstrictor effect of glibenclamide was not enhanced in the presence of NLA + 8PT and 2) the exercise-induced increase in CBF was largely maintained. These findings show profound species differences in the mechanisms controlling CBF at rest and during exercise.NEW & NOTEWORTHY The present study demonstrates important species differences in the regulation of coronary blood flow by adenosine, NO, and K_ATP channels at rest and during exercise. In swine, these mechanisms follow a linear additive design, as opposed to dogs which follow a nonlinear redundant design. Simultaneous blockade of all three mechanisms virtually abolished exercise-induced coronary vasodilation in dogs, whereas a substantial vasodilator reserve could still be recruited during exercise in swine.

Aortopulmonary window and coronary anatomy - still a pre-operative diagnostic trouble!

We present a case of aortopulmonary window in which the diagnosis of anomalous left coronary artery originating from pulmonary artery was made intra-operatively even if the coronary arteries anatomy was correctly studied pre-operatively with echocardiography. No evidence of coronary anomalies or indirect sings of coronary anomalies has been noted. Should we improve our pre-operative diagnostic accuracy and how?

Surgery for Aneurysmal Coronary Artery Fistulas to the Coronary Sinus in Adults

Surgical treatment of aneurysmal distal congenital coronary artery fistulas depends on size and anatomy. From 2008 to 2021, we applied a new surgical technique in 7 adult patients: proximal and distal fistula closure, opening of aneurysmal artery, and revascularization of branches rising from the fistula under cardiopulmonary bypass and cardiac arrest. (Level of Difficulty: Intermediate.)

Coronary Venous Visualization During Deep Septal Lead Placement: An Unexpected Finding

Left bundle branch area pacing has emerged as a safe and feasible alternative to conventional pacing. Acute septal injury, septal perforation, and arteriovenous fistula are potential risks of deep septal implants. Contrast drainage through the lesser cardiac veins and subsequent filling of major epicardial vessels may be benign observations noted during forceful hand injection. (Level of Difficulty: Advanced.).

The coronary capillary bed and its role in blood flow and oxygen delivery: A review

The assumption that the coronary capillary blood flow is exclusively regulated by precapillary vessels is not supported by recent data. Rather, the complex coronary capillary bed has unique structural and geometric characteristics that invalidate many assumptions regarding red blood cell (RBC) transport, for example, data based on a single capillary or that increases in flow are the result of capillary recruitment. It is now recognized that all coronary capillaries are open and that their variations in flow are due to structural differences, local O₂ demand and delivery, and variations in hematocrit. Recent data reveal that local mechanisms within the capillary bed regulate flow via signaling mechanisms involving RBC signaling and endothelial-associated pericytes that contract and relax in response to humoral and neural signaling. The discovery that pericytes respond to vasoactive signals (e.g., nitric oxide, phenylephrine, and adenosine) underscores the role of these cells in regulating capillary diameter and consequently RBC flux and oxygen delivery. RBCs also affect blood flow by sensing <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>P</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:msub> </mml:math> and releasing nitric oxide to facilitate relaxation of pericytes and a consequential capillary dilation. New data indicate that these signaling mechanisms allow control of blood flow in specific coronary capillaries according to their oxygen requirements. In conclusion, mechanisms in the coronary capillary bed facilitate RBC density and transit time, hematocrit, blood flow and O₂ delivery, factors that decrease capillary heterogeneity. These findings have important clinical implications for myocardial ischemia and infarction, as well as other vascular diseases.

Sinoatrial Nodal Artery Arising from the Right Posterolateral Artery: A Rare Anatomical Variant

We discuss a case report of a 66-year-old male with no prior cardiac history who presented to the hospital with persistent hiccups and shortness of breath. Following a positive nuclear stress test and cardiac catheterization, a rare anatomical variant of a sinoatrial nodal artery originating from the right posterolateral artery was revealed.

Coronary circulatory function with increasing obesity: A complex U-turn

AIMS

The aim of this investigation was to explore and characterize alterations in coronary circulatory function in function of increasing body weight with medically controlled cardiovascular risk factors and, thus, "metabolically" unhealthy obesity.

MATERIALS AND METHODS

We prospectively enrolled 106 patients with suspected CAD but with normal stress-rest myocardial perfusion on ¹³ N-ammonia PET/CT and with medically controlled or no cardiovascular risk factors. ¹³ N-ammonia PET/CT concurrently determined myocardial blood flow (MBF) during pharmacologically induced hyperaemia and at rest. Based on body mass index (BMI), patients were grouped into normal weight (BMI: 20.0-24.9 kg/m² , n = 22), overweight (BMI: 25.0-29.9 kg/m² , n = 27), obese (BMI: 30.0-39.9 kg/m² , n = 31), and morbidly obese (BMI ≥ 40kg/m² , n = 26).

RESULTS

Resting MBF was comparable among groups (1.09 ± 0.18 vs. 1.00 ± 0.15 vs. 0.96 ± 0.18 vs.. 1.06 ± 0.31 ml/g/min; p = .279 by ANOVA). Compared to normal weight individuals, the hyperaemic MBF progressively decreased in in overweight and obese groups, respectively (2.54 ± 0.48 vs. 2.02 ± 0.27 and 1.75 ± 0.39 ml/g/min; p < .0001), while it increased again in the group of morbidly obese individuals comparable to normal weight (2.44 ± 0.41 vs. 2.54 ± 0.48 ml/g/min, p = .192). The BMI of the study population correlated with the hyperaemic MBF in a quadratic or U-turn fashion (r = .34, SEE = 0.46; p ≤ .002).

CONCLUSIONS

The U-turn of hyperaemic MBF from obesity to morbid obesity is likely to reflect contrasting effects of abdominal versus subcutaneous adipose tissue on coronary circulatory function indicative of two different disease entities, but needing further investigations.

Arterial Hypertension and the Hidden Disease of the Eye: Diagnostic Tools and Therapeutic Strategies

Hypertension is a major cardiovascular risk factor that is responsible for a heavy burden of morbidity and mortality worldwide. A critical aspect of cardiovascular risk estimation in hypertensive patients depends on the assessment of hypertension-mediated organ damage (HMOD), namely the generalized structural and functional changes in major organs induced by persistently elevated blood pressure values. The vasculature of the eye shares several common structural, functional, and embryological features with that of the heart, brain, and kidney. Since retinal microcirculation offers the unique advantage of being directly accessible to non-invasive and relatively simple investigation tools, there has been considerable interest in the development and modernization of techniques that allow the assessment of the retinal vessels’ structural and functional features in health and disease. With the advent of artificial intelligence and the application of sophisticated physics technologies to human sciences, consistent steps forward have been made in the study of the ocular fundus as a privileged site for diagnostic and prognostic assessment of diverse disease conditions. In this narrative review, we will recapitulate the main ocular imaging techniques that are currently relevant from a clinical and/or research standpoint, with reference to their pathophysiological basis and their possible diagnostic and prognostic relevance. A possible non pharmacological approach to prevent the onset and progression of retinopathy in the presence of hypertension and related cardiovascular risk factors and diseases will also be discussed.

Role of Quantitative Flow Ratio in Predicting Future Cardiac Allograft Vasculopathy in Heart Transplant Recipients

BACKGROUND

Coronary angiography is the gold standard for cardiac allograft vasculopathy (CAV) diagnosis, but it usually detects the disease at an advanced stage. We investigated the role of quantitative flow ratio (QFR), a noninvasive tool to identify potentially flow-limiting lesions, in predicting CAV development in heart transplant recipients.

METHODS

Consecutive heart transplant recipients with no evidence of angiographic CAV at baseline coronary angiography were retrospectively included between January 2010 and December 2015, and QFR computation was performed. The relationship between vessel QFR and the occurrence of angiographic vessel-related CAV (≥50% stenosis) was assessed.

RESULTS

One hundred forty-three patients were included and QFR computation was feasible in 241 vessels. The median value of QFR at baseline coronary angiography was 0.98 (interquartile range, 0.94-1.00). During a median follow-up of 6.0 years (interquartile range, 4.6-7.8 years), vessel-related CAV occurred in 25 (10.4%) vessels. Receiver-operating characteristic curve analysis identified a QFR best cutoff of ≤0.95 (area under the curve, 0.81 [95% CI, 0.71-0.90]; P<0.001). QFR≤0.95 was associated with an increased risk of vessel-related CAV (adjusted hazard ratio, 20.87 [95% CI, 5.35-81.43]; P<0.001). In an exploratory analysis, QFR≤0.95 in at least 2 vessels was associated with higher incidence of cardiovascular death or late graft dysfunction (71.4% in recipients with 2-3 vessels affected versus 5.1% in recipients with 0-1 vessels affected, P<0.001).

CONCLUSIONS

In a cohort of heart transplant recipients, QFR computation at baseline coronary angiography may be a safe and reliable tool to predict vessel-related CAV and clinical outcomes at long-term follow-up.

Guide-Extension Carlino: A novel technique for crossing a microcatheter uncrossable proximal cap during chronic total occlusion interventions

Balloon and microcatheter uncrossable chronic total occlusions can be challenging to treat. We present a novel technique for treating such lesions through contrast injection via a guide catheter extension wedged against the proximal cap. We named this technique "guide-extension Carlino."

A Closed-Loop Modeling Framework for Cardiac-to-Coronary Coupling

The mechanisms by which cardiac mechanics effect coronary perfusion (cardiac-to-coronary coupling) remain incompletely understood. Several coronary models have been proposed to deepen our understanding of coronary hemodynamics, but possibilities for in-depth studies on cardiac-to-coronary coupling are limited as mechanical properties like myocardial stress and strain are most often neglected. To overcome this limitation, a mathematical model of coronary mechanics and hemodynamics was implemented in the previously published multi-scale CircAdapt model of the closed-loop cardiovascular system. The coronary model consisted of a relatively simple one-dimensional network of the major conduit arteries and veins as well as a lumped parameter model with three transmural layers for the microcirculation. Intramyocardial pressure was assumed to arise from transmission of ventricular cavity pressure into the myocardial wall as well as myocardial stiffness, based on global pump mechanics and local myofiber mechanics. Model-predicted waveforms of global epicardial flow velocity, as well as of intramyocardial flow and diameter were qualitatively and quantitatively compared with reported data. Versatility of the model was demonstrated in a case study of aortic valve stenosis. The reference simulation correctly described the phasic pattern of coronary flow velocity, arterial flow impediment, and intramyocardial differences in coronary flow and diameter. Predicted retrograde flow during early systole in aortic valve stenosis was in agreement with measurements obtained in patients. In conclusion, we presented a powerful multi-scale modeling framework that enables realistic simulation of coronary mechanics and hemodynamics. This modeling framework can be used as a research platform for in-depth studies of cardiac-to-coronary coupling, enabling study of the effect of abnormal myocardial tissue properties on coronary hemodynamics.

Peripheral Coronary Artery Circulatory Dysfunction in Remote Stage Kawasaki Disease Patients Detected by Adenosine Stress 13N-Ammonia Myocardial Perfusion Positron Emission Tomography

Coronary peripheral circulatory disturbances in the remote stage of Kawasaki disease have been reported. In this study, of the 50 patients in the remote stage of Kawasaki disease who underwent coronary perfusion evaluation using adenosine-loaded ¹³N-ammonia positron emission tomography, 28 patients who did not have stenosis of ≥75% in the left coronary artery underwent an evaluation for myocardial flow reserve (MFR) of the left anterior descending artery (LAD) and left circumflex artery (LCx). Clinical findings were compared between patients with normal (≥2.0) and abnormal (<2.0) MFRs. In the group with an abnormal MFR in the LAD, the responsiveness of the coronary vascular resistance to adenosine stress decreased even in the LCx (3.50 ± 1.23 vs. 2.39 ± 0.25, p = 0.0100). In the group with an abnormal MFR in the LCx, the responsiveness of the coronary vascular resistance in the LAD also decreased (3.27 ± 1.39 vs. 2.03 ± 0.25, p = 0.0105), and the age of onset of Kawasaki disease tended to be younger in the group with abnormal MFR in the LAD and LCx. We found that the peripheral coronary circulation was extensively impaired in the remote stage of Kawasaki disease, suggesting that an early onset of Kawasaki disease may affect the peripheral coronary circulation in later years.

Closing a Right Coronary Artery Fistula Draining Into the Coronary Sinus Using a Covered Stent in the Coronary Sinus

This report describes the case of a symptomatic patient with a right coronary artery fistula draining into the coronary sinus who underwent transcatheter closure, which was deployed in the drainage site to seal off the exit of the fistula. (Level of Difficulty: Advanced.)

Extracardiac coronary steal induced by upper limb hyperemia: a feature of internal mammary artery arteriogenesis

Function of naturally existing internal mammary artery (IMA)-to-coronary artery anastomoses has been shown by augmented blood supply to the coronary collateral circulation in response to IMA occlusion. Theoretically, this beneficial functional connection is invertible and can be linked to coronary steal, the verification of whose hypothesis would provide alternate proof to the mentioned functional evidence. This was an observational study including 40 patients with chronic coronary syndrome, distal IMA occlusion, and upper limb hyperemia (verum group), and 40 propensity score matched controls (placebo group) without IMA occlusion or hyperemia. Primary study end point was the intergroup difference and temporal development in coronary collateral function (i.e., collateral flow index; CFI) as obtained at 30, 45, and 60 s following a proximal coronary artery balloon occlusion. CFI is the ratio between simultaneous mean coronary occlusive pressure divided by mean aortic pressure both subtracted by central venous pressure. To provoke a steal phenomenon, upper limb hyperemia was induced by upper arm blood pressure cuff deflation following a 5-min suprasystolic inflation ipsilateral to the sensor-wired coronary artery with release immediately after the first CFI measurement. Between the first and the second CFI measurement, CFI change (i.e., CFI@45s - CFI@30s) was absent in the verum group whereas there was CFI recruitment in the placebo group: 0.000 ± 0.023 and +0.009 ± 0.013, respectively; P = 0.032. Among patients with artificial distal IMA occlusion, induction of ipsilateral upper limb hyperemia provokes extracardiac coronary steal as expressed by temporarily absent collateral recruitment as it normally takes place without upper limb hyperemia.NEW & NOTEWORTHY Induction of ipsilateral upper limb hyperemia provokes extracardiac coronary steal among patients with artificial distal internal mammary artery occlusion. Coronary steal via the occluded internal mammary arteries serves as alternate proof of concept of the already existing evidence of their functional extracoronary collateral supply.

Accurate assessment of coronary blood flow by continuous thermodilution technique: Validation in a swine model

OBJECTIVE

To assess the accuracy of coronary thermodilution measurements made with the RayFlow® infusion catheter.

BACKGROUND

Measurements of absolute coronary blood flow (ABF) and absolute microvascular resistance (R_μ ) by continuous coronary thermodilution can be obtained in humans but their accuracy using a novel dedicated infusion catheter has not yet been validated. We compared ABF values obtained at different infusion rates to coronary blood flow (CBF) values obtained using flow probes, in swine.

METHODS

Twelve domestic swine were instrumented with coronary flow probes placed around the left anterior descending and circumflex coronary arteries. ABF was assessed with the RayFlow® infusion catheter during continuous saline infusion at fixed rates of 5 (n = 14), 10 (n = 15), 15 (n = 19), and 20 (n = 12) ml/min.

RESULTS

In the 60 measurements, ABF measured using thermodilution averaged 41 ± 17 ml/min (range from 17 to 90) and CBF values obtained with the coronary flow probes averaged 37 ± 18 ml/min (range from 8 to 87). The corresponding R_μ values were 1532 ± 791 (range from 323 to 5103) and 1903 ± 1162 (range from 287 to 6000) Woods units using thermodilution and coronary flow probe assessments, respectively. ABF and R_μ values measured using thermodilution were significantly correlated with the corresponding measurements obtained using coronary flow probes (R = 0.84 [0.73-0.95] and R = 0.80 [0.69-0.88], respectively).

CONCLUSIONS

ABF and R_μ assessed by continuous saline infusion through a RayFlow® catheter closely correlate with measurements obtained with the gold standard coronary flow probes in a swine model.

Rapid fall in circulating non-classical monocytes in ST elevation myocardial infarction patients correlates with cardiac injury

Myocardial infarction leads to a rapid innate immune response that is ultimately required for repair of damaged heart tissue. We therefore examined circulating monocyte dynamics immediately after reperfusion of the culprit coronary vessel in STEMI patients to determine whether this correlated with level of cardiac injury. A mouse model of cardiac ischemia/reperfusion injury was subsequently used to establish the degree of monocyte margination to the coronary vasculature that could potentially contribute to the drop in circulating monocytes. We retrospectively analyzed blood samples from 51 STEMI patients to assess the number of non-classical (NC), classical, and intermediate monocytes immediately following primary percutaneous coronary intervention. Classical and intermediate monocytes showed minimal change. On the other hand, circulating numbers of NC monocytes fell by approximately 50% at 90 minutes post-reperfusion. This rapid decrease in NC monocytes was greatest in patients with the largest infarct size (P < .05) and correlated inversely with left ventricular function (r = 0.41, P = .04). The early fall in NC monocytes post-reperfusion was confirmed in a second prospective study of 13 STEMI patients. Furthermore, in a mouse cardiac ischemia model, there was significant monocyte adhesion to coronary vessel endothelium at 2 hours post-reperfusion pointing to a specific and rapid vessel margination response to cardiac injury. In conclusion, rapid depletion of NC monocytes from the circulation in STEMI patients following coronary artery reperfusion correlates with the level of acute cardiac injury and involves rapid margination to the coronary vasculature.

On the relevance of boundary conditions and viscosity models in blood flow simulations in patient-specific aorto-coronary bypass models

Physiologically realistic results are the aim of every blood flow simulation. This is not different in aorto-coronary bypasses where the properties of the coronary circulation may significantly affect the relevance of the performed simulations. By considering three patient-specific bypass geometries, the present article focuses on two aspects of the coronary blood flow - its phasic flow pattern and its behaviour affected by blood rheology. For the phasic flow property, a multiscale modelling approach is chosen as a means to assess the ability of five different types of coronary boundary conditions (mean arterial pressure, Windkessel model and three lumped parameter models) to attain realistic coronary haemodynamics. From the analysed variants of boundary conditions, the best option in terms of physiological characteristics and its potential for use in patient-based simulations, is utilised to account for the effect of shear-dependent viscosity on the resulting haemodynamics and wall shear stress stimulation. Aside from the Newtonian model, the blood rheology is approximated by two non-Newtonian models in order to determine whether the choice of a viscosity model is important in simulations involving coronary circulation. A comprehensive analysis of obtained results demonstrated notable superiority of all lumped parameter models, especially in comparison to the constant outlet pressure, which regardless of bypass type gave overestimated and physiologically misleading results. In terms of rheology, it was noted that blood in undamaged coronary arteries behaves as a Newtonian fluid, whereas in vessels with atypical lumen geometry, such as that of anastomosis or stenosis, its shear-thinning behaviour should not be ignored.

Evaluation of right coronary vascular dysfunction in severe pulmonary hypertensive rats using synchrotron radiation microangiography

Pulmonary hypertension (PH) causes cardiac hypertrophy in the right ventricle (RV) and eventually leads to RV failure due to persistently elevated ventricular afterload. We hypothesized that the mechanical stress on the RV associated with increased afterload impairs vasodilator function of the right coronary artery (RCA) in PH. Coronary vascular response was assessed using microangiography with synchrotron radiation (SR) in two well-established PH rat models, monocrotaline injection or the combined exposure to chronic hypoxia and vascular endothelial growth factor receptor blockade with Su5416 (SuHx model). In the SuHx model, the effect of the treatment with the nonselective endothelin-1 receptor antagonist (ERA), macitentan, was also examined. Myocardial viability was determined in SuHx model rats, using 18F-FDG Positron emission tomography (PET) and magnetic resonance imaging (MRI). Endothelium-dependent and endothelium-independent vasodilator responses were significantly attenuated in the medium and small arteries of severe PH rats. ERA treatment significantly improved RCA vascular function compared with the untreated group. ERA treatment improved both the decrease in ejection fraction and the increased glucose uptake, and reduced RV remodeling. In addition, the upregulation of inflammatory genes in the RV was almost suppressed by ERA treatment. We found impairment of vasodilator responses in the RCA of severe PH rat models. Endothelin-1 activation in the RCA plays a major role in impaired vascular function in PH rats and is partially restored by ERA treatment. Treatment of PH with ERA may improve RV function in part by indirectly attenuating right heart afterload and in part by associated improvements in right coronary endothelial function.NEW & NOTEWORTHY We demonstrated for the first time the impairment of vascular responses in the right coronary artery (RCA) of the dysfunctional right heart in pulmonary hypertensive rats in vivo. Treatment with an endothelin-1 receptor antagonist ameliorated vascular dysfunction in the RCA, enabled tissue remodeling of the right heart, and improved cardiac function. Our results suggest that impaired RCA function might also contribute to the early progression to heart failure in patients with severe pulmonary arterial hypertension (PAH). The endothelium of the coronary vasculature might be considered as a potential target in treatments to prevent heart failure in severe patients with PAH.

Clinical significance of early systolic reverse flow in left anterior descending coronary artery on transthoracic echocardiography in patients with acute myocardial infarction

BACKGROUND

Predicting the cardiac function in chronic phase of acute myocardial infarction (AMI) patients is important. Previous studies showed that the presence of early systolic reverse flow (ESRF) in coronary flow measured with a Doppler guide wire is a predictor of worsening chronic phase function in patients with anterior AMI. We routinely examined the coronary flow velocity (CFV) of the distal left anterior descending artery (LAD) using transthoracic echocardiography (TTE) in AMI patients. The aim of this study is to investigate whether the ESRF in TTE is associated with the chronic cardiac function, recovery of cardiac function, and the incidence of major adverse cardiac events (MACE) in patients with anterior AMI.

METHODS

We enrolled 84 patients with their first anterior AMI. Using TTE, we recorded the CFV of distal LAD within 5 days after primary percutaneous coronary intervention. Patients were divided into two groups, ESRF + group (ESRF was detected in TTE: 21 cases) and ESRF- group (ESRF was not detected in TTE: 63 cases). We compared chronic cardiac function in TTE, changes in cardiac function in acute and chronic phase (ΔLVEF, ΔLVDd), and the incidence of MACE.

RESULTS

The incidence of MACE in ESRF-group was lower than that in ESRF + group (3.3% vs 19.1% P = .02). LVEF in chronic phase in ESRF- group was higher than that in ESRF + group (54.1 ± 5.6% vs 40.4 ± 6.2% P < .001). ΔLVDd was smaller in ESRF-group than ESRF + group (-0.62 ± 4.0 mm vs +5.06 ± 3.4 mm P = .003).

CONCLUSION

Early systolic reverse flow in TTE is a predictor of chronic cardiac function and incidence of MACE in patients with anterior AMI.

Metabolomics reveal dynamic changes in eicosanoid profile in patients with ST-elevation myocardial infarction after percutaneous coronary intervention

Eicosanoids play important roles in the cardiovascular system. The metabolic disorders involving some eicosanoids in the pathophysiologic process include myocardial infarction and myocardial ischaemia-reperfusion injury. Percutaneous coronary intervention (PCI) is often the first-choice strategy for acute ST-segment elevation myocardial infarction (STEMI) according to current guidelines. This study aimed to investigate the dynamic eicosanoid metabolic profile in STEMI patients after PCI. The eicosanoid profiles in plasma of 20 patients at seven times (30 minutes before surgery; 6, 12, 24, and 72 hours after surgery; 1 day before discharge; and 28 days after surgery) were studied by using metabolomics. Levels of PGE2, PGD2, and TXA2 were decreased significantly and EETs contents were increased significantly at 6 hours after PCI. EETs were hydrolysed to DHETs within a short time after surgery (12-72 hours). 20-HETE content was significantly increased. In samples taken at the time of discharge and at follow-up after discharge, LTB4 level continued to increase. This work suggests that change in content of some functional eicosanoids may be involved in cardiac injury and repair after PCI in a synergistic manner.

Myocardial Blood Flow Control by Oxygen Sensing Vascular Kvβ Proteins

[Figure: see text].

The value of coronary computed tomography angiography in assessing the cardiac circulation of an outpatient-based population

To evaluate the perfusion of coronary circulation and its related factors and the difference in the peak filling times in aortic sinus and coronary sinus by coronary computed tomography angiography (CCTA).From January 1 to August 1, 2018, 61 outpatients with angina pectoris were recruited, completed a questionnaire about risk factors and underwent CCTA, which was also used to assess the stenosis of different coronary artery segments.The duration of circulation was 9.50 ± 2.43 seconds in patients with flat T wave, which was shorter than the duration in normal subjects (P = .021). However, other cardiovascular risk factors showed no effect on the duration of circulation. In addition, the duration of circulation was closely related to the peak filling time of coronary sinus [r(s) = 0.681]. We further divided the circulation time difference (delta) values into 3 levels (<6, 6-12, and ≥12 seconds).It showed that the circulation duration (Y) was associated with:Therefore, the cardiac circulation duration was negatively related to the degree of stenosis in the 1 diagonal and proximal LCA.It compensates for the inability of CCTA to assess circulation at rest simply by determining the peak filling time in the aortic sinus and the coronary sinus. Moderate cardiac microcirculation duration was related to a low incidence of clinical symptoms and electrocardiogram disorders, which was determined mainly by the diagonal and left circumflex branch 1 of LCA.

Optimal Use of Vasodilators for Diagnosis of Microvascular Angina in the Cardiac Catheterization Laboratory

Among patients with angina and nonobstructive coronary artery disease, those with coronary microvascular dysfunction have a poor outcome. Coronary microvascular dysfunction is usually diagnosed by assessing flow reserve with an endothelium-independent vasodilator like adenosine, but the optimal diagnostic threshold is unclear. Furthermore, the incremental value of testing endothelial function has never been assessed before. We sought to determine what pharmacological thresholds correspond to exercise pathophysiology and myocardial ischemia in patients with coronary microvascular dysfunction.

Selective perfusion of coronary vasculature in preterm sheep: a methodological innovation undermined by unfavourable operation of the foramen ovale

Antenatal cardiac intervention affords new prospects for hypoplastic left heart syndrome. Its success, however, may come not only from absence of impediments to blood flow but also from a sufficiently developed cardiac wall. Here, we examined the feasibility to perfuse selectively the fetal coronary circulation for treatment with growth promoting agents. Pregnant sheep (94-114 days gestation, term 145 days) were used. An aortic stop-flow procedure was developed for intracoronary access in the nonexposed fetus and human mesenchymal stem cells and their exosomes served as test agents. We found that aortic stop-flow ensures preferential distribution of fluorescent microspheres to the heart. However, intracoronary administration of stem cells or exosomes was detrimental, with fetal demise occurring around surgery or at variable intervals afterwards. Coincidentally, stop-flow caused by itself a marked rise of intraluminal pressure within the occluded aorta along with histological signs of coronary obstruction. We conclude that it is feasible to perfuse selectively the coronary circulation of the preterm fetus, but treatments are not compatible with survival of the animals. The cause for failure is found in the absence of hemodynamic compensation to stop-flow via a left-to-right shunt. This unexpected event is attributed to a largely membranous foramen ovale, characteristic of sheep, that collapses under pressure.

Coronary Disease-Associated Gene TCF21 Inhibits Smooth Muscle Cell Differentiation by Blocking the Myocardin-Serum Response Factor Pathway

RATIONALE

The gene encoding TCF21 (transcription factor 21) has been linked to coronary artery disease risk by human genome-wide association studies in multiple racial ethnic groups. In murine models, Tcf21 is required for phenotypic modulation of smooth muscle cells (SMCs) in atherosclerotic tissues and promotes a fibroblast phenotype in these cells. In humans, TCF21 expression inhibits risk for coronary artery disease. The molecular mechanism by which TCF21 regulates SMC phenotype is not known.

OBJECTIVE

To better understand how TCF21 affects the SMC phenotype, we sought to investigate the possible mechanisms by which it regulates the lineage determining MYOCD (myocardin)-SRF (serum response factor) pathway.

METHODS AND RESULTS

Modulation of TCF21 expression in human coronary artery SMC revealed that TCF21 suppresses a broad range of SMC markers, as well as key SMC transcription factors MYOCD and SRF, at the RNA and protein level. We conducted chromatin immunoprecipitation-sequencing to map SRF-binding sites in human coronary artery SMC, showing that binding is colocalized in the genome with TCF21, including at a novel enhancer in the SRF gene, and at the MYOCD gene promoter. In vitro genome editing indicated that the SRF enhancer CArG box regulates transcription of the SRF gene, and mutation of this conserved motif in the orthologous mouse SRF enhancer revealed decreased SRF expression in aorta and heart tissues. Direct TCF21 binding and transcriptional inhibition at colocalized sites were established by reporter gene transfection assays. Chromatin immunoprecipitation and protein coimmunoprecipitation studies provided evidence that TCF21 blocks MYOCD and SRF association by direct TCF21-MYOCD interaction.

CONCLUSIONS

These data indicate that TCF21 antagonizes the MYOCD-SRF pathway through multiple mechanisms, further establishing a role for this coronary artery disease-associated gene in fundamental SMC processes and indicating the importance of smooth muscle response to vascular stress and phenotypic modulation of this cell type in coronary artery disease risk.

First-in-Human Endo-Bentall Procedure for Simultaneous Treatment of the Ascending Aorta and Aortic Valve

We describe the endovascular management of a middle-aged woman who developed a bleeding suprasternal fistula after conventional aortic valve replacement. The patient's condition was considered inoperable. A customized stent attached to a transcatheter valve was successfully used to treat the individual, this being the first-in-human case of the promising Endo-Bentall procedure. (Level of Difficulty: Advanced.).

Topologic and Hemodynamic Characteristics of the Human Coronary Arterial Circulation

Background

Many processes contributing to the functional and structural regulation of the coronary circulation have been identified. A proper understanding of the complex interplay of these processes requires a quantitative systems approach that includes the complexity of the coronary network. The purpose of this study was to provide a detailed quantification of the branching characteristics and local hemodynamics of the human coronary circulation.

Methods

The coronary arteries of a human heart were filled post-mortem with fluorescent replica material. The frozen heart was alternately cut and block-face imaged using a high-resolution imaging cryomicrotome. From the resulting 3D reconstruction of the left coronary circulation, topological (node and loop characteristics), topographic (diameters and length of segments), and geometric (position) properties were analyzed, along with predictions of local hemodynamics (pressure and flow).

Results

The reconstructed left coronary tree consisted of 202,184 segments with diameters ranging from 30 μm to 4 mm. Most segments were between 100 μm and 1 mm long. The median segment length was similar for diameters ranging between 75 and 200 μm. 91% of the nodes were bifurcations. These bifurcations were more symmetric and less variable in smaller vessels. Most of the pressure drop occurred in vessels between 200 μm and 1 mm in diameter. Downstream conductance variability affected neither local pressure nor median local flow and added limited extra variation of local flow. The left coronary circulation perfused 358 cm³ of myocardium. Median perfused volume at a truncation level of 100 to 200 μm was 20 mm³ with a median perfusion of 5.6 ml/min/g and a high local heterogeneity.

Conclusion

This study provides the branching characteristics and hemodynamic analysis of the left coronary arterial circulation of a human heart. The resulting model can be deployed for further hemodynamic studies at the whole organ and local level.

An advanced mock circulation loop for in vitro cardiovascular device evaluation

Controlled and repeatable in vitro evaluation of cardiovascular devices using a mock circulation loop (MCL) is essential prior to in vivo or clinical trials. MCLs often consist of only a systemic circulation with no autoregulatory responses and limited validation. This study aimed to develop, and validate against human data, an advanced MCL with systemic, pulmonary, cerebral, and coronary circulations with autoregulatory responses. The biventricular MCL was constructed with pneumatically controlled hydraulic circulations with Starling responsive ventricles and autoregulatory cerebral and coronary circulations. Hemodynamic repeatability was assessed and complemented by validation using impedance cardiography data from 50 healthy humans. The MCL successfully simulated patient scenarios including rest, exercise, and left heart failure with and without cardiovascular device support. End-systolic pressure-volume relationships for respective healthy and heart failure conditions had slopes of 1.27 and 0.54 mm Hg mL^-1 (left ventricle), and 0.18 and 0.10 mm Hg mL^-1 (right ventricle), aligning with the literature. Coronary and cerebral autoregulation showed a strong correlation (R² : .99) between theoretical and experimentally derived circuit flow. MCL repeatability was demonstrated with correlation coefficients being statistically significant (P < .05) for all simulated conditions while MCL hemodynamics aligned well with human data. This advanced MCL is a valuable tool for inexpensive and controlled evaluation of cardiovascular devices.