Coronary Venous Blood Research Articles

Role of potassium as a coronary metabolic vasodilator

K+ release from the myocardium is associated with decreased coronary vascular resistance. Accumulation of extracellular K+ has been linked to mechanisms of vasodilation in the coronary circulation including activation of the electrogenic Na+-K+ pump in smooth muscle (Murray and Sparks, Circ. Res. 1977) and endothelial-mediated hyperpolarization via Kir2.1 channels (Zhao et al., PNAS 2020). Our objective was to examine K+ as a coronary metabolic vasodilator in vivo. Further, we addressed two potential shortcomings of previous studies: the short duration of the bolus K+ stimulus employed and the seemingly high concentrations required to produce vasodilation. We hypothesized that continuous, steady-state intracoronary infusions of K+ would produce sustained coronary vasodilation in a concentration-dependent manner. Our methods involved instrumenting anesthetized, open-chest Yorkshire swine (male and female, 60 kg) for measurements of coronary blood flow, as well as arterial and coronary venous blood sampling. The left anterior descending coronary artery was cannulated and perfused under the control of a pressure servo, allowing us to determine flow and infuse K+. Our results show small, but statistically significant (* represents p < 0.05), effects of K+ on coronary hemodynamics. The coronary venous K+ concentration was 4.0 ± 0.1 mM at baseline. Infusing K+ into the coronary artery at increasing rates increased coronary venous K+ to 4.9 ± 0.2*, 6.4 ± 0.2*, and 7.9 ± 0.2* mM. Higher K+ concentrations caused fatal arrhythmias. Coronary blood flow was 0.73 ± 0.14 ml/min/g at baseline. Infusing K+ into the coronary artery at increasing rates increased coronary blood flow to 0.78 ± 0.14*, 0.82 ± 0.15*, and 0.86 ± 0.16* ml/min/g. These small coronary blood flow changes were sustained during continuous K+ infusion. We conclude that K+ is a coronary vasodilator, as has been demonstrated previously. Importantly, however, we emphasize that the effects of K+ are extremely modest and the concentrations required to produce physiologically significant vasodilation are life-threatening. With the assumption that the venous K+ concentration is in equilibrium with that surrounding the smooth muscle and cardiac muscle of the working heart, we urge caution in interpreting isolated artery studies that routinely use 15-20 mM K+ to elicit hyperpolarization and vasodilation. Our data do not support the idea that K+ plays a major role in regulating coronary vascular resistance. This work was supported by National Institutes of Health grant R01 HL158723. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 13: Myocardial Metabolic And Electrolyte Derangements Linked To PEA Rearrest

Background: Cardiac rearrest after return of spontaneous circulation (ROSC) is a significant barrier to successful resuscitation, making it a high priority for emergency care research. Regardless of initial arrest rhythm, rearrest is commonly due to pulseless electrical activity (PEA). However, mechanisms underlying PEA rearrest are poorly understood. Previously, myocardial contractile function during ischemia-reperfusion has been tied to alterations in extracellular sodium (Na+) and calcium (Ca2+) concentrations. Objective: To determine physiological predictors and explore potential mechanisms underlying susceptibility to PEA rearrest. Methods: Acute myocardial infarction (AMI) induced by left anterior descending artery (LAD) occlusion was followed by 8 min of VF, then pigs were resuscitated (defibrillation, CPR, epinephrine) to ROSC and the LAD was reperfused. Pigs were instrumented to measure metabolic variables from arterial and coronary sinus venous blood gases, electrolytes, and hemodynamics. Subjects that had PEA rearrest (n=7) were compared to those that did not rearrest (n=4). Results: Hemodynamic and primary arrest characteristics were similar between PEA and no rearrest groups, including ischemia duration, time to ROSC, CPR events, and epinephrine administration. At ROSC, hemodynamic and metabolic variables including pH, myocardial lactate consumption, myocardial arterial/venous oxygen difference were also similar between groups. Importantly, post-ROSC myocardial lactate consumption was significantly increased in the PEA group (3.9 vs. 0.5 mmol, p<0.03) as was coronary sinus Na+ (147 vs. 135 mEq/L, p<.03); however, coronary sinus Ca2+ was significantly reduced (1.9 vs. 2.3 mEq/L, p<.01 ). Taken together, these data suggest that metabolic substrate depletion may promote local electrolyte shifts contributing to mechanical dysfunction underlying PEA. Conclusion: PEA rearrest was associated with increased myocardial lactate consumption and derangements in cardiac Na+ and Ca2+ in a translational model with well controlled arrest characteristics. Improved understanding of mechanisms underlying post-ROSC electrolyte shifts may identify novel mechanisms and therapeutic approaches to prevent and treat PEA.

Creatine phosphate preconditioning reduces ischemiareperfusion injury in isolated rat heart

Aim . To study the effect of simultaneous administration of creatine phosphate immediately before ischemia on cardiodynamic parameters and biomarkers of oxidative stress in the coronary venous blood flow during retrograde perfusion in an isolated rat heart. Materials and methods . 20 Wistar albino rats were divided into 2 groups: group 1 (control) and group 2 (experimental), 10 rats per group. Cannulation and retrograde perfusion of aorta of an isolated rat heart with Krebs–Henseleit buffered solution by Landendorff was performed. Both groups underwent ischemia-reperfusion injury, which included global ischemia for 20 minutes followed by reperfusion for 30 minutes. The group 2 (experimental) was preconditioned with creatine phosphate at a dose of 0.2 mmol/l for 5 min before ischemia. We registered cardiodynamic parameters and indicators of oxidative stress at the point of stabilization, at the 1st and 30th minutes of reperfusion. Results . With the impact of creatine phosphate at the 30th minute of reperfusion in the group 2 in comparison with group 1, there was found an increase in the maximum and minimum speed of pressure elevation in the left ventricle (1.7 and 1.9 times, respectively), and of systolic and diastolic pressure in the left ventricle (1.5 and 1.6 times, respectively). Biomarkers of oxidative stress (lipid peroxidation index, nitrites, superoxide anion radical and hydrogen peroxide) were also statistically significantly lower in the group 2 after the 1st minute of reperfusion (by 1.2 times, by 1.4 times, by 2.8 times and 1.9 times, respectively), and after the 30th minute (1.3 times, 2.1 times, 1.9 times and 2.1 times, respectively). Conclusion . The administration of creatine phosphate into the coronary flow 5 minutes before the onset of ischemia has a protective effect on myocardial contractility. Reduction of oxidative stress and damage can be considered as a protective effect of creatine phosphate.

Epinephrine Exacerbates Myocyte Injury in a Porcine Model of Cardiac Arrest

ObjectiveAlthough circulating cardiac troponin (cTn) concentrations are often elevated in patients following resuscitation from cardiac arrest (CA), this finding is commonly attributed to myocyte injury caused by ongoing myocardial infarction (MI) and/or defibrillation during resuscitation. To determine whether measurable cTn elevations occur independently of these factors, we employed serial sampling of systemic and coronary venous blood to quantify cTn release in a porcine model of CA devoid of ongoing MI or multiple defibrillation attempts. In light of recent concerns regarding potential detrimental effects of epinephrine (EPI) in CA, cTn levels were compared in animals that were resuscitated with vs. without exogenous EPI.MethodsSwine (n=41) were subjected to 7 min CA via electrical induction of ventricular fibrillation (VF) followed by cardiopulmonary resuscitation (CPR) with manual chest compressions and mechanical ventilation for up to 20 min. Biphasic defibrillation (200 J) was performed 1 min after the start of CPR and a subset of animals (n=10) received intravenous EPI (0.015 mg/kg) 1 min later. After return of spontaneous circulation (ROSC; defined as unassisted systolic blood pressure >80 mmHg for 1 min), animals were followed for up to 4 hours with serial blood sampling from the jugular vein and coronary sinus for assessment of cTnI via a porcine‐specific ELISA.ResultsAmong the entire cohort, 1.2±0.1 defibrillator shocks were required to terminate VF, ROSC was achieved 175±7 seconds after the initiation of CPR, and 15 animals (38%) survived for the entire 4‐hour recovery period (2/10 with EPI, 13/31 without EPI). Despite the absence of ongoing MI or prolonged resuscitation efforts, a significant 5‐fold rise in coronary sinus (from 106±17 to 526±74 ng/L, p<0.01) and systemic (from 67±14 to 350±54 ng/L, p<0.01) cTnI concentrations was observed 15 min post‐ROSC (trans‐coronary cTnI gradient from 39±7 to 176±29 ng/L, p<0.01). Widening of the trans‐coronary cTnI gradient continued throughout the recovery period, reaching 795±164 ng/L 4 hours post‐ROSC and leading to a 16‐fold increase in circulating cTnI concentrations at this timepoint (1087±208 ng/L, p<0.01 vs. baseline). Exogenous EPI exacerbated myocyte injury, as EPI‐treated animals exhibited a significantly higher trans‐coronary cTnI gradient 30 min post‐ROSC that persisted throughout the recovery period and led to significantly higher circulating cTnI concentrations vs. animals resuscitated without EPI at each timepoint (Figure ).ConclusionsThese results demonstrate that resuscitation from CA is associated with measurable elevations in cTnI as early as 15 min post‐ROSC, even in the absence of ongoing MI or prolonged CPR with multiple defibrillator shocks. Thus, assessment of circulating cTnI following resuscitation from CA is unlikely to accurately identify patients suffering from an acute coronary syndrome. Administration of exogenous EPI during resuscitation exacerbates the extent of myocyte injury, which may contribute to poor long‐term outcomes.Support or Funding InformationFunding SourcesNIH, AHA, ZOLL Foundation, Pro‐Al Medico Technologies, Inc., UB CAT, NCATS, and the Dept. of Veterans Affairs.Figure 1

Ranolazine may exert its beneficial effects by increasing myocardial adenosine levels.

We hypothesized that ranolazine-induced adenosine release is responsible for its beneficial effects in ischemic heart disease. Sixteen open-chest anesthetized dogs with noncritical coronary stenosis were studied at rest, during dobutamine stress, and during dobutamine stress with ranolazine. Six additional dogs without stenosis were studied only at rest. Regional myocardial function and perfusion were assessed. Coronary venous blood was drawn. Murine endothelial cells and cardiomyocytes were incubated with ranolazine and adenosine metabolic enzyme inhibitors, and adenosine levels were measured. Cardiomyocytes were also exposed to dobutamine and dobutamine with ranolazine. Modeling was employed to determine whether ranolazine can bind to an enzyme that alters adenosine stores. Ranolazine was associated with increased adenosine levels in the absence (21.7 ± 3.0 vs. 9.4 ± 2.1 ng/mL, P < 0.05) and presence of ischemia (43.1 ± 13.2 vs. 23.4 ± 5.3 ng/mL, P < 0.05). Left ventricular end-systolic wall stress decreased (49.85 ± 4.68 vs. 57.42 ± 3.73 dyn/cm2, P < 0.05) and endocardial-to-epicardial myocardial blood flow ratio tended to normalize (0.89 ± 0.08 vs. 0.76 ± 0.10, P = nonsignificant). Adenosine levels increased in cardiac endothelial cells and cardiomyocytes when incubated with ranolazine that was reversed when cytosolic-5'-nucleotidase (cN-II) was inhibited. Point mutation of cN-II aborted an increase in its specific activity by ranolazine. Similarly, adenosine levels did not increase when cardiomyocytes were incubated with dobutamine. Modeling demonstrated plausible binding of ranolazine to cN-II with a docking energy of -11.7 kcal/mol. We conclude that the anti-adrenergic and cardioprotective effects of ranolazine-induced increase in tissue adenosine levels, likely mediated by increasing cN-II activity, may contribute to its beneficial effects in ischemic heart disease.NEW & NOTEWORTHY Ranolazine is a drug used for treatment of angina pectoris in patients with ischemic heart disease. We discovered a novel mechanism by which this drug may exhibit its beneficial effects. It increases coronary venous levels of adenosine both at rest and during dobutamine-induced myocardial ischemia. Ranolazine also increases adenosine levels in endothelial cells and cardiomyocytes in vitro, by principally increasing activity of the enzyme cytosolic-5'-nucleotidase. Adenosine has well-known myocardial protective and anti-adrenergic properties that may explain, in part, ranolazine's beneficial effect in ischemic heart disease.

Modulation of Myocardial Oxygen Delivery in Response to Isovolemic Hemodilution

Background and Hypothesis: Prior studies have established that progressive increases in coronary blood flow are sufficient to maintain myocardial oxygen delivery in response to reductions in arterial oxygenation. However, the precise mechanisms responsible for anemic coronary vasodilation remain poorly understood. This investigation tested the hypothesis that autonomic neural pathways contribute to the maintenance of myocardial oxygen delivery in response to graded reductions in arterial hematocrit. &#x0D; Experimental Design: Experiments were conducted in open-chest anesthetized swine while assessing coronary blood flow and coronary arterial and venous blood gases in response to progressive hemodilution. Isovolemic hemodilution was achieved via simultaneous removal of 250mL of arterial blood and addition of 250mL of a synthetic plasma expander (Hespan) in swine that received either vehicle or a combination of atropine (0.5mg/kg) and propranolol (1mg/kg) (Atro/Pro). &#x0D; Results: Relative to vehicle control swine, treatment with Atro/Pro increased heart rate by ~50±4 beats/min and arterial pressure by ~10±1 mmHg. However, Atro/Pro did not significantly alter increases in coronary blood flow in response to isovolemic hemodilution (hematocrits ranging from ~35±1% to ~15±1%). Coronary venous PO2, an index of myocardial oxygenation, was also unchanged by hemodilution in both vehicle and Atro/Pro treated swine. &#x0D; Conclusion and Potential Impact: These data suggest that autonomic neural pathways do not play a significant role in the maintenance of myocardial oxygen delivery in response to graded reduction in arterial oxygen content. Understanding of how myocardial oxygen supply is ultimately sensed and regulated in response to reductions in tissue oxygenation remains elusive.

Acute molecular effects of pressure-controlled intermittent coronary sinus occlusion in patients with advanced heart failure.

AimsCardiac repair has steered clinical attention and remains an unmet need, because available regenerative therapies lack robust mechanistic evidence. Pressure‐controlled intermittent coronary sinus occlusion (PICSO), known to induce angiogenetic and vasoactive molecules as well as to reduce regional ischemia, may activate endogenous regenerative processes in failing myocardium. We aimed to investigate the effects of PICSO in patients with advanced heart failure undergoing cardiac resynchronization therapy.Methods and resultsEight out of 32 patients were treated with PICSO, and the remainder served as controls. After electrode testing including left ventricular leads, PICSO was performed for 20 min. To test immediate molecular responses, in both patient groups, coronary venous blood samples were taken at baseline and after 20 min, the time required for the intervention. Sera were tested for microRNAs and growth factors. To test the ability of up‐regulated soluble factors on cell proliferation and expression of transcription factors [e.g. Krüppel‐like factor 4 (KLF‐4)], sera were co‐cultured with human cardiomyocytes and fibroblasts. As compared with controls, significant differential expression (differences between pre‐values and post‐values in relation to both patient cohorts) of microRNA patterns associated with cardiac development was observed with PICSO. Importantly, miR‐143 (P < 0.048) and miR‐145 (P < 0,047) increased, both targeting a network of transcription factors (including KLF‐4) that promote differentiation and repress proliferation of vascular smooth muscle cells. Additionally, an increase of miR‐19b (P < 0.019) known to alleviate endothelial cell apoptosis was found, whereas disadvantageous miR‐320b (P < 0.023) suspect to impair expression of c‐myc, normally provoking cell cycle re‐entry in post‐mitotic myocytes and miR‐25 (P < 0.023), decreased, a target of anti‐miR application to improve contractility in the failing heart. Co‐cultured post‐PICSO sera significantly increased cellular proliferation both in fibroblasts (P < 0.001) and adult cardiomycytes (P < 0.004) sampled from a transplant recipient as compared with controls. Adult cardiomyocytes showed a seven‐fold increase of the transcription factor KLF‐4 protein when co‐cultured with treated sera as compared with controls.ConclusionsHere, we show for the first time that PICSO, a trans‐coronary sinus catheter intervention, is associated with an increase in morphogens secreted into cardiac veins, normally present during cardiac development, and a significant induction of cell proliferation. Present findings support the notion that epigenetic modifications, that is, haemodynamic stimuli on venous vascular cells, may reverse myocardial deterioration. Further investigations are needed to decipher the maze of complex interacting molecular pathways in failing myocardium and the potential role of PICSO to reinitiate developmental processes to prevent further myocardial decay eventually reaching clinical significance.

I.V. NIRS off-pump coronary artery ischemia monitoring bypass surgery

Background: Spectroscopic data were compared with hemodynamic parameters, electrocardiogram, transesophageal echocardiography and laboratory findings. A conversion to extracorporeal circulation was not necessary. The mean number of grafts per patient was 3.1±0.6. An intraoperative myocardial ischemia was not evident, as indicated by electrocardiogram and transesophageal echocardiography.Methods: Continuous spectroscopic analysis showed reproducible absorption spectra of coronary sinus blood. Due to uneventful intraoperative courses, clear ischemia-related changes could be detected in none of the patients. Present initial results show that intravascular near-infrared spectroscopy can reliably be used for an online intraoperative ischemia monitoring in off-pump coronary artery bypass surgery.Results: In 15 elective patients undergoing off-pump myocardial revascularization, intravascular near-infrared spectroscopic analysis of coronary venous blood was performed. NIR signals were transferred through a fiberoptic catheter for signal emission and collection. For data analysis and processing, a miniature spectrophotometer with multivariate statistical package was used. Signal acquisition and analysis were performed before and after revascularization. However, the method has to be further evaluated and standardized to determine the role of spectroscopy in off-pump coronary artery bypass surgery. In off-pump coronary artery bypass surgery, manipulations on the beating heart can lead to transient interruptions of myocardial oxygen supply, which can generate an accumulation of oxygen-dependent metabolites in coronary venous blood.Conclusions: The objective of this study was to evaluate the reliability of intravascular near-infrared spectroscopy as a monitoring method to detect possible ischemic events in off-pump coronary artery bypass procedures.

2-aminoaethanesulfonic acid compounds possess protective property in reperfusion-induced heart jnjury

The study aim was to explore pharmacological effects of 2-aminoaethansulfonic acid compounds in reperfusion-induced heart injury.&#x0D; Materials and methods. The study was performed on rats and dogs of both sexes, isolated rats’ hearts. Two compounds of 2-aminoethanesulfonic acid, magnesium-containing (LBK-527) and phenylacetamide-containing (LKhT-317) were investigated. Antiarrhythmic effects of the compounds were studied in coronary artery reperfusion 7, 30 and 120 min after acute myocardial ischemia modeling. The ability of the substances to limit the volume of reperfusion injury was investigated by differential indicator method. The influence of substances on the intensity of free radical processes in the myocardium, as well as the metabolic profile of coronary venous blood during reperfusion, was studied. Hemodynamic effects of the substances were studied during in vivo experiments, as well as on an isolated heart.&#x0D; Results and discussion. The compounds effectively prevent cardiac arrhythmias generation caused by myocardial reperfusion after 7, 30 and 120 minutes of ischemia. Prophylactic intravenous administration of LHT-317 and LBK-527 at higher therapeutic doses limit the size of rats’ heart necrosis zone after occlusion-reperfusion syndrome develops, prevent reperfusion-induced excessive activation of free-radical processes in rat myocardium, activate the antiradical activity of the heart tissues, and optimize [O2] and [CO2] in coronary venous sinus blood of dogs. Cardioprotective effect of the compounds manifests in preserving myocardium contractile function, maintaing BP and stabilizing heart chronotropic function.&#x0D; Conclusions. The study analysis shows that 2-aminoethanesulfonic acid compounds have cardioprotective effect in reperfusion syndrome.

Novel Synthesized Radical-Containing Nanoparticles Limit Infarct Size Following Ischemia and Reperfusion in Canine Hearts.

Although nitroxyl radicals such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) scavenge free radicals, their short half-life and considerable side effects such as systemic hypotension and bradycardia have limited their clinical application. Since a radical-containing nanoparticle (RNP) delivers nitroxyl radicals with a prolonged half-life specific to ischemic hearts, we investigated whether RNPs reduce infarct size without the occurrence of substantial side effects and whether nitric oxide (NO) contributes to the cardioprotective effects of RNPs. The left anterior descending coronary arteries of dogs were occluded for 90min, followed by reperfusion for 6h. Either RNPs, micelles (not containing TEMPO) (control), or 4-hydroxy-TEMPO (TEMPOL) was injected into a systemic vein for 5min before reperfusion. We evaluated the infarct size, myocardial apoptosis, plasma NO levels in coronary venous blood, and the RNP spectra using an electron paramagnetic resonance assay. RNPs reduced infarct size compared with the control group and TEMPOL group (19.5±3.3 vs. 42.2±3.7 vs. 30.2±3.4%). RNPs also reduced myocardial apoptosis compared with the control and TEMPOL group. Coronary venous NO levels increased in the RNP group. In conclusion, the administration of 2,2,6,6-tetramethylpiperidine-1-oxyl as a RNP exerted cardioprotective effects against ischemia and reperfusion injury in canine hearts without exerting unfavorable hemodynamic effects. RNPs may represent a promising new therapy for patients with acute myocardial infarction.

DNA Content in Extracellular Vesicles Isolated from Porcine Coronary Venous Blood Directly after Myocardial Ischemic Preconditioning

BackgroundExtracellular vesicles (EV) are nano-sized membranous structures released from most cells. They have the capacity to carry bioactive molecules and gene expression signals between cells, thus mediating intercellular communication. It is believed that EV confer protection after ischemic preconditioning (IPC). We hypothesize that myocardial ischemic preconditioning will lead to rapid alteration of EV DNA content in EV collected from coronary venous effluent.Materials and MethodsIn a porcine myocardial ischemic preconditioning model, EV were isolated from coronary venous blood before and after IPC by differential centrifugation steps culminating in preparative ultracentrifugation combined with density gradient ultracentrifugation. The EV preparation was validated, the DNA was extracted and further characterized by DNA sequencing followed by bioinformatics analysis.ResultsPorcine genomic DNA fragments representing each chromosome, including mitochondrial DNA sequences, were detected in EV isolated before and after IPC. There was no difference detected in the number of sequenced gene fragments (reads) or in the genomic coverage of the sequenced DNA fragments in EV isolated before and after IPC. Gene ontology analysis showed an enrichment of genes coding for ion channels, enzymes and proteins for basal metabolism and vesicle biogenesis and specific cardiac proteins.ConclusionsThis study demonstrates that porcine EV isolated from coronary venous blood plasma contain fragments of DNA from the entire genome, including the mitochondria. In this model we did not find specific qualitative or quantitative changes of the DNA content in EV collected immediately after an in vivo myocardial IPC provocation. This does not rule out the possibility that EV DNA content changes in response to myocardial IPC which could occur in a later time frame.

Open-loop (feed-forward) and feedback control of coronary blood flow during exercise, cardiac pacing, and pressure changes.

A control system model was developed to analyze data on in vivo coronary blood flow regulation and to probe how different mechanisms work together to control coronary flow from rest to exercise, and under a variety of experimental conditions, including cardiac pacing and with changes in coronary arterial pressure (autoregulation). In the model coronary flow is determined by the combined action of a feedback pathway signal that is determined by the level of plasma ATP in coronary venous blood, an adrenergic open-loop (feed-forward) signal that increases with exercise, and a contribution of pressure-mediated myogenic control. The model was identified based on data from exercise experiments where myocardial oxygen extraction, coronary flow, cardiac interstitial norepinephrine concentration, and arterial and coronary venous plasma ATP concentrations were measured during control and during adrenergic and purinergic receptor blockade conditions. The identified model was used to quantify the relative contributions of open-loop and feedback pathways and to illustrate the degree of redundancy in the control of coronary flow. The results indicate that the adrenergic open-loop control component is responsible for most of the increase in coronary blood flow that occurs during high levels of exercise. However, the adenine nucleotide-mediated metabolic feedback control component is essential. The model was evaluated by predicting coronary flow in cardiac pacing and autoregulation experiments with reasonable fits to the data. The analysis shows that a model in which coronary venous plasma adenine nucleotides are a signal in local metabolic feedback control of coronary flow is consistent with the available data.

Surgical Placement of Catheters for Long-term Cardiovascular Exercise Testing in Swine

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early cardiopulmonary dysfunction is difficult to diagnose, particularly in animal models, as cardiopulmonary function is often measured invasively, requiring anesthesia. As many anesthetic agents are cardiodepressive, subtle changes in cardiovascular function may be masked. In contrast, chronic instrumentation allows for measurement of cardiopulmonary function in the awake state, so that measurements can be obtained under quiet resting conditions, without the effects of anesthesia and acute surgical trauma. Furthermore, when animals are properly trained, measurements can also be obtained during graded treadmill exercise. Flow probes are placed around the aorta or pulmonary artery for measurement of cardiac output and around the left anterior descending coronary artery for measurement of coronary blood flow. Fluid-filled catheters are implanted in the aorta, pulmonary artery, left atrium, left ventricle and right ventricle for pressure measurement and blood sampling. In addition, a 20 G catheter is positioned in the anterior interventricular vein to allow coronary venous blood sampling. After a week of recovery, swine are placed on a motor-driven treadmill, the catheters are connected to pressure and flow meters, and swine are subjected to a five-stage progressive exercise protocol, with each stage lasting 3 min. Hemodynamic signals are continuously recorded and blood samples are taken during the last 30 sec of each exercise stage. The major advantage of studying chronically instrumented animals is that it allows serial assessment of cardiopulmonary function, not only at rest but also during physical stress such as exercise. Moreover, cardiopulmonary function can be assessed repeatedly during disease development and during chronic treatment, thereby increasing statistical power and hence limiting the number of animals required for a study.

Surgical Placement of Catheters for Long-term Cardiovascular Exercise Testing in Swine.

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early cardiopulmonary dysfunction is difficult to diagnose, particularly in animal models, as cardiopulmonary function is often measured invasively, requiring anesthesia. As many anesthetic agents are cardiodepressive, subtle changes in cardiovascular function may be masked. In contrast, chronic instrumentation allows for measurement of cardiopulmonary function in the awake state, so that measurements can be obtained under quiet resting conditions, without the effects of anesthesia and acute surgical trauma. Furthermore, when animals are properly trained, measurements can also be obtained during graded treadmill exercise. Flow probes are placed around the aorta or pulmonary artery for measurement of cardiac output and around the left anterior descending coronary artery for measurement of coronary blood flow. Fluid-filled catheters are implanted in the aorta, pulmonary artery, left atrium, left ventricle and right ventricle for pressure measurement and blood sampling. In addition, a 20 Gcatheter is positioned in the anterior interventricular vein to allow coronary venous blood sampling. After a week of recovery, swine are placed on a motor-driven treadmill, the catheters are connected to pressure and flow meters, and swine are subjected to a five-stage progressive exercise protocol, with each stage lasting 3 min. Hemodynamic signals are continuously recorded and blood samples are taken during the last 30 sec of each exercise stage. The major advantage of studying chronically instrumented animals is that it allows serial assessment of cardiopulmonary function, not only at rest but also during physical stress such as exercise. Moreover, cardiopulmonary function can be assessed repeatedly during disease development and during chronic treatment, thereby increasing statistical power and hence limiting the number of animals required for a study.

Abstract 17400: Catecholamine Release Triggered by Epicardial Absolute Refractory Period Stimulation Augments Global Left Ventricular Function

Background: Biventricular epicardial (Epi) pacing can augment left ventricular (LV) function in heart failure. We postulated that these beneficial effects could involve catecholamine release from local autonomic nerve activation. This hypothesis was tested by applying Epi pacing stimuli during the muscle’s absolute refractory period (ARP) thereby activating intrinsic nerves without altering activation sequence. Methods: Anesthetized farm pigs (n=5) were instrumented with a LV high-fidelity pressure transducer, left atrial and LV Epi pacing electrodes, and sonomicrometer segment length (SL) gauges placed proximal and distal to the LV stimulation site. A small catheter was placed into the great cardiac vein adjacent to the LV pacing site for blood sampling. During atrial pacing at constant rate, 3 electrical pulses (0.8ms, 2-3x threshold volts) were applied to the LV Epi electrodes during the ARP. An experimental run consisted of baseline measurements, with 10 minutes of stimulation followed by 5 minutes of recovery repeated 3 times before and with ß- receptor blockade (BB, metoprolol, 5 mg). Coronary venous blood was sampled at baseline and at 5 and 10 minutes of stimulation for norepinephrine analysis (NE by ELISA). Results: ARP stimulation produced a significant increase in coronary venous NE levels (p&lt; 0.01) accompanied by a significant 10-15% increase in LV dP/dt max (p&lt; 0.01). Segment length vs. LV pressure loop area proximal to the stimulus site was significantly decreased (29.8 ± 10.9 mmHg*mm) compared to baseline (92.6 ± 8.2 mmHg*mm) but was unchanged at the distal site. BB abolished the changes in segment function and blocked the increase in LV dP/dt despite continued NE release. Conclusion: These results demonstrate that ARP EPI pacing induces NE release and augments global LV function. This effect may contribute to the beneficial effect of biventricular Epi pacing in some patients with heart failure.

Clinical Features and Surgical Outcomes of Coronary Sinus Orifice Atresia.

This study aimed to review clinical features and surgical outcomes of coronary sinus orifice atresia (CSOA). From 2003 to 2015, 6 patients were diagnosed with CSOA. Median age at diagnosis was 2 years (range 0.2-73). CSOA was preoperatively diagnosed in 2 patients, intraoperatively in 3, and postoperatively in 1. Coronary venous blood flow drained into innominate vein through the left superior vena cava (LSVC) in 2, into the atrium through Thebesian veins in 2, and into both in 2. Three patients required surgical treatment. The first patient with a congenitally corrected transposition of great arteries had undergone ligation of the LSVC and a cutback of the proximal LSVC into the functional right atrium during the double-switch operation. The second patient with tricuspid atresia gradually developed hypoxia after the Fontan operation due to the increase in veno-venous shunt blood flow from the Fontan pathway to the right atrium through the LSVC and Thebesian veins, so that the LSVC was ligated and the coronary sinus was unroofed 6 years after Fontan operation. The other functional single ventricle patient had undergone ligation of the LSVC and a cutback of the proximal LSVC into the left atrium during the Fontan operation. There were no mortalities at the median follow-up of 9 years (1-11). CSOA should be suspected when the LSVC and usual-sized innominate vein were presented. Surgical treatment is required if the postoperative hemodynamics would affect coronary venous perfusion, like single ventricular palliation (244 words).

Myocardial ischemic preconditioning in a porcine model leads to rapid changes in cardiac extracellular vesicle messenger RNA content

BackgroundExtracellular vesicles (EVs) are thought to exert protective effects after ischemic and remote ischemic preconditioning. It is not well understood which EV content factors are most relevant for protective effects. We hypothesize that ischemic preconditioning leads to qualitative changes in EV mRNA content and quantitative changes in EV size and number. MethodsUsing an in vivo porcine ischemic preconditioning model, EVs were collected from coronary venous blood, and isolated by differential ultracentrifugations. The presence and purity of EV were verified by electron microscopy and Western blot, and EV number was assessed by nanoparticle tracking analysis. The mRNA EV was identified by microarray. ResultsGene ontology analysis showed enrichment of EV mRNA coding for proteins associated with regulation of transcription, translation, extracellular matrix, morphogenic development and feeding behavior. There were 11,678 different mRNA transcripts detected in EV, where a total of 1103 was significantly increased or decreased after preconditioning, of which 638 mRNA sequences were up-regulated and/or emerged due to preconditioning. Several of them have known association with ischemic preconditioning. There was no significant difference in EV quantity or size before and after preconditioning. ConclusionsThese findings demonstrate in an in vivo model that myocardial ischemic preconditioning influences the composition of mRNA in EV, including gene transcripts for proteins associated with the protective effect of ischemic preconditioning. The finding that preconditioned parental cells release EV containing mRNA that is qualitatively different from those released by non-preconditioned cells shows the importance of the external milieu on parental cell EV production.

Histone Deacetylase Inhibitor Treatment Increases Coronary t-PA Release in a Porcine Ischemia Model

BackgroundThe expression of the tissue plasminogen activator gene can be affected by histone deacetylation inhibition and thus appears to be under epigenetic control.ObjectivesThe study aimed to test if in vivo pharmacological intervention by valproic acid treatment would lead to increase in tissue plasminogen activator release capacity.MethodsIn an anaesthetized pig model, a controlled transient coronary occlusion was used to stimulate coronary tissue plasminogen activator release in a valproic acid treated (one week) and a non-treated group. Coronary venous blood samples from the ischemic region were collected, great cardiac vein thermodilution flow measurements were performed, and trans-coronary tissue plasminogen activator fluxes were calculated. Plasminogen activator inhibitor-1 was also measured.ResultsAdequate sampling from the affected area after the 10 minute ischemic period was confirmed by lactate measurements. Fluxes for tissue plasminogen activator at minutes 1, 3, 5, 7 and 10 were measured and then used to present cumulative net tissue plasminogen activator release for the whole measurement period for both groups. Area under the curve was higher for the valproic acid treated group at 10 minutes; 932±173 nanograms (n = 12) compared to the non-treated group, 451±78 nanograms (n = 10, p = 0.023). There was no difference in levels of plasminogen activator inhibitor-1 between groups.ConclusionsThese findings support a proof of concept for histone deacetylation inhibition positive effect on tissue plasminogen activator expression in an in vivo setting. Further studies are needed to find an optimal way to implement histone deacetylation inhibition to achieve desired clinical changes in tissue plasminogen activator expression.

Carperitide induces coronary vasodilation and limits infarct size in canine ischemic hearts: role of NO

Carperitide is effective for heart failure (HF) owing to its diuretic and vasodilatory effects. This recombinant peptide may also have direct cardioprotective effects because carperitide reduces the severity of heart failure and limits infarct size. Because coronary vasodilation is an important cardioprotective treatment modality, we investigated whether carperitide increased coronary blood flow (CBF) and improved myocardial metabolic and contractile dysfunction during ischemia in canine hearts. We also tested whether carperitide is directly responsible for limiting the infarct size. We infused carperitide at 0.025-0.2 μg kg(-1) min(-1) into the canine coronary artery. A minimum dose of 0.1 μg kg(-1) min(-1) was required to obtain maximal vasodilation. To test the effects of carperitide on ischemic hearts, we reduced perfusion pressure in the left anterior descending coronary artery such that CBF decreased to one-third of the baseline value. At 10 min after carperitide was infused at a dose of 0.1 μg kg(-1) min(-1), we observed increases in CBF, fractional shortening (FS) and pH levels in coronary venous blood without concomitant increases in cardiac nitric oxide (NO) levels; these changes were attenuated using either the atrial natriuretic peptide receptor antagonist HS-142-1 or the NO synthase inhibitor L(ω)-nitroarginine methyl ester (L-NAME). Cyclic guanosine monophosphate (GMP) levels in the coronary artery were elevated in response to carperitide that also limited the infarct size after 90 min of ischemia and subsequent reperfusion. Again, these effects were blunted by L-NAME. Carperitide increases CBF, reduces myocardial contractile and metabolic dysfunction and limits infarct size. In addition, NO is necessary for carperitide-induced vasodilation and cardioprotection in ischemic hearts.

Relationship of left atrial global peak systolic strain with left ventricular diastolic dysfunction and brain natriuretic peptide level in patients presenting with non-ST elevation myocardial infarction.

BackgroundIn patients presenting with non-ST elevation myocardial infarction, we investigated the relationship of left atrial deformational parameters evaluated by 2-dimensional speckle tracking imaging (2D-STI) with conventional echocardiographic diastolic dysfunction parameters and brain natriuretic peptide level.Material/MethodsWe enrolled 74 non-ST segment elevation myocardial infarction patients who were treated with percutaneous coronary intervention and 58 healthy control subjects. Non-ST segment elevation myocardial infarction patients had echocardiographic examination 48 h after the percutaneous coronary intervention procedure and venous blood samples were drawn simultaneously. In addition to conventional echocardiographic parameters, left atrial strain curves were obtained for each patient. Average peak left atrial strain values during left ventricular systole were measured.ResultsBNP values were higher in non-ST segment elevation myocardial infarction patients compared to controls. Mean left atrium peak systolic global longitudinal strain in Group 2 (the control group) was higher than in the non-ST segment elevation myocardial infarction group. Left atrium peak systolic global longitudinal strain was significantly correlated with left ventricular ejection fraction. There was a significant inverse correlation between left atrium peak systolic global longitudinal strain and brain natriuretic peptide level, left atrium volume maximum, and left atrium volume minimum.ConclusionsOur study shows that Left atrium peak systolic global longitudinal strain values decreased consistently with deteriorating systolic and diastolic function in non-ST segment elevation myocardial infarction patients treated with percutaneous coronary intervention. Left atrium peak systolic global longitudinal strain measurements may be helpful as a complimentary method to evaluate diastolic function in this patient population.