Acute hemodynamic effects of endogenous adenosine in patients with chronic heart failure

Stressing the Cardiopulmonary Vascular System: The Role of Echocardiography

The cardiopulmonary vascular system represents a key determinant of prognosis in several cardiorespiratory diseases. Although right heart catheterization is considered the gold standard for assessing pulmonary hemodynamics, a comprehensive noninvasive evaluation including left and right ventricular reserve and function and cardiopulmonary interactions remains highly attractive. Stress echocardiography is crucial in the evaluation of many cardiac conditions, typically coronary artery disease but also heart failure and valvular heart disease. In stress echocardiographic applications beyond coronary artery disease, the assessment of the cardiopulmonary vascular system is a cornerstone. The possibility of coupling the left and right ventricles with the pulmonary circuit during stress can provide significant insight into cardiopulmonary physiology in healthy and diseased subjects, can support the diagnosis of the etiology of pulmonary hypertension and other conditions, and can offer valuable prognostic information. In this state-of-the-art document, the topic of stress echocardiography applied to the cardiopulmonary vascular system is thoroughly addressed, from pathophysiology to different stress modalities and echocardiographic parameters, from clinical applications to limitations and future directions.

Cardiac purinergic signalling in health and disease

This review is a historical account about purinergic signalling in the heart, for readers to see how ideas and understanding have changed as new experimental results were published. Initially, the focus is on the nervous control of the heart by ATP as a cotransmitter in sympathetic, parasympathetic, and sensory nerves, as well as in intracardiac neurons. Control of the heart by centers in the brain and vagal cardiovascular reflexes involving purines are also discussed. The actions of adenine nucleotides and nucleosides on cardiomyocytes, atrioventricular and sinoatrial nodes, cardiac fibroblasts, and coronary blood vessels are described. Cardiac release and degradation of ATP are also described. Finally, the involvement of purinergic signalling and its therapeutic potential in cardiac pathophysiology is reviewed, including acute and chronic heart failure, ischemia, infarction, arrhythmias, cardiomyopathy, syncope, hypertrophy, coronary artery disease, angina, diabetic cardiomyopathy, as well as heart transplantation and coronary bypass grafts.

Development and application of a LC-MS/MS method to quantify basal adenosine concentration in human plasma from patients undergoing on-pump CABG surgery

A sensitive and robust LC-MS/MS method was developed to quantify basal adenosine concentrations in human plasma of patients undergoing on-pump coronary artery bypass grafting (CABG) surgery. A strong cation exchange (SCX) monolithic cartridge was used to enrich analyte, improve robustness, and reduce biological complexity. A simple modifier-free mobile phase was employed to improve sensitivity and reproducibility. This method exhibits consistent precision and accuracy, and the RSDs or REs of all the intraday and interday determinations were within 10%. The calibration curve was linear across the examined dynamic range from 1nM to 500nM (r(2)=0.996). LOD and LOQ were determined to be 0.257nM and 0.857nM respectively, while LLOQ was below 10nM. This method was used to monitor changes of adenosine levels in patient plasma drawn intraoperatively during on-pump CABG surgery. The analysis of 84 patients revealed that the mean concentration of adenosine in coronary sinus plasma after cardiopulmonary bypass (CPB) is higher than that in coronary sinus before CPB (p=0.0024; two-tailed t-test) and that in radial artery plasma after CPB (p=0.0409; two-tailed t-test). These findings suggest that the equilibrium between adenosine production and elimination has favored the elevation of adenosine basal level during on-pump CABG surgery and the change is specific to heart tissues. Evaluation of adenosine with a sensitive and robust analytical method has important implications on providing consistent results and meaningful insights into adenosine regulation, as well as its steady state and sustained action on the heart. Relating patient characteristics or clinical outcomes with basal adenosine concentration can be used to optimize the CABG-CPB maneuver by regulating adenosine level via pharmacological intervention, and differentiating adenosine's contribution to cardioprotection from other modulatory factors.

Activation of immune and inflammatory systems in chronic heart failure: novel therapeutic approaches

Despite extensive research and novel treatments, chronic heart failure (CHF) remains a cause of high morbidity and mortality. Mounting evidence suggested that immune activation and inflammation play critical roles in the pathogenesis of CHF. In this review, we examine the current evidence regarding this contemporary pathophysiological mechanism, and evaluate the effects of conventional and novel cardiovascular drugs, such as calcium sensitisers and statins, on the immune and inflammatory mediator's network. Although therapies, which specifically antagonise tumour necrosis factor-alpha have not demonstrated considerable benefit in patients with CHF, there is an increasing evidence to suggest greater value from non-specific anti-inflammatory approaches, including: pentoxifylline, intravenous immunoglobulin, immune modulation therapy, growth hormones, physical training and nutrition regulation. Several innovative therapeutic targets, such as peroxisome proliferator-activated receptor gamma activators, Rho-kinase, p38 mitogen-activated protein kinase, nuclear transcription factor NF-kappaB, recovering or augmenting parasympathetic tone, cardiac resynchronisation therapy, macrophage inhibitors and chemokine receptor antagonists, are briefly discussed in this review. While we have recently demonstrated the potential merits of combining low-dose methotrexate with conventional therapy, through extensively modulating the activated immune and inflammatory mediator's network, there is a need for further rigorous research of this complex network, especially involving current promising therapies which modulate this system. Such evidence has the potential to revolutionise changes for the management of this disorder. Based on the 'heterogeneity' of immune activation and inflammation among different CHF populations, an 'optimised combination treatment' may offer exciting benefits for individual therapy in the future.

Pulmonary Hemodynamic Effects of Dipyridamole Infusion in Patients with Normal and Elevated Pulmonary Artery Systolic Pressure Receiving PB127

BACKGROUND

Intravenous administration of microspheres used as ultrasound contrast agents may potentially alter pulmonary hemodynamics. PB127 (POINT Biomedical Corp., San Carlos, CA) is an investigational ultrasound perfusion-imaging agent used in conjunction with dipyridamole to diagnose coronary artery disease. The effects of PB127 alone or in combination with dipyridamole on pulmonary hemodynamics have not been described.

METHODS

We studied 20 patients, including 10 with elevated screening pulmonary artery systolic pressure (>35 mm Hg). Doppler-derived pulmonary hemodynamics were determined before and after continuous infusion of PB127 (0.175 mg/kg diluted in 5% dextrose) or 5% dextrose. Patients then received dipyridamole (0.56 mg/kg) and hemodynamics were again assessed.

RESULTS

During PB127/dextrose infusion, there were no significant changes in pulmonary hemodynamics compared with baseline. After dipyridamole, there were small increases in pulmonary artery systolic pressure and in pulmonary flow and a reduction in pulmonary vascular resistance. These changes occurred in patients with normal and elevated pulmonary artery systolic pressure.

CONCLUSION

PB127 infusion does not alter pulmonary hemodynamics. Mild alterations of pulmonary hemodynamics occur after dipyridamole administration.

Pharmacology of adenosine receptors in the vasculature

Adenosine is widely distributed in mammals. One of the primary roles of adenosine within the cardiovascular system is to directly control the functions of both cardiac and vascular tissues. Recently, there has been considerable interest in the subclassification of adenosine receptors. Characterization of a heterogeneous population of receptors for adenosine could provide an opportunity for the development of novel compounds of therapeutic value. Adenosine is released from cells as a result of metabolism, and its release can be increased dramatically from cells that are metabolically stressed. This implies that adenosine can be released from a variety of cells throughout the body, as a result of increased metabolic rates, in concentrations that can have a profound impact on blood vessel function and, consequently, blood flow. It is recognized that the actions of this nucleoside on the vasculature are most prominent when oxygen demand is high and there is a reduction in oxygen tension at the site in question. Therefore, it is not surprising that adenosine has been shown to be an important regulator of blood vessel tone under hypoxic conditions. Furthermore, the activation of adenosine receptors on blood vessels can result in relaxation and/or contractions. The nature of the response subsequent to the activation of adenosine receptors is primarily dependent on the type of blood vessel involved and basal tone. This review will focus on the characterization of subtypes of adenosine receptors in blood vessels, as well as the effect of the stimulation of adenosine receptors on the peripheral circulation.

Treatment of pulmonary hypertension during surgery with nitric oxide and vasodilators

PURPOSE

To describe the effects of the combination of several therapies on the pulmonary circulation and cardiac function in a patient with severe pulmonary hypertension.

CLINICAL FEATURES

We report the case of a female patient with chronic secondary pulmonary hypertension and cardiac failure who underwent right hemicolectomy under general anesthesia. Insertion of a pulmonary artery catheter before the operation revealed pulmonary artery pressure (PAP) of 55/24 mm Hg which was lowered moderately by 40 parts per million (ppm) inhNO. During surgery, the patient presented an episode of atrial fibrillation with a slow, irregular heart rate of 45-50 min(-1) and variable systemic pressure. A dipyridamole DPD (0.2 mg x kg(-1)) bolus stabilized systemic pressure and increased heart rate and cardiac output. However, PAP did not change. Nitroglycerine infusion was started at 10 mg x hr(-1) shortly after the initiation of DPD. The patient responded favourably to combined inhNO, intravenous DPD and NTG therapy with a marked and sustained reduction of PAP and a systemic hemodynamic stability.

CONCLUSION

We conclude that: 1) in combination with inhNO, DPD does not augment the inhNO-induced decrease in PAP; 2) DPD improves the hemodynamic profile and elevates cardiac output; 3) therapeutic combination (inhaled NO, NTG, DPD) has a potent effect on pulmonary pressure in cardiac failure patients.

The hemodynamic effects of adenosine infusion after experimental right heart infarct in young swine

The use of a vasodilator selective to the pulmonary circulation may be beneficial in cases with right-ventricle failure, as it will decrease right-heart afterload without concurrent systemic hypotension. Adenosine has recently been advocated as such a drug, although its clinical efficacy in this respect is still in question. We therefore devised an experimental protocol of right-heart infarct to test the efficacy of adenosine in alleviating symptoms of right-heart failure. Right-heart infarct was induced experimentally in 17 young pigs. After hemodynamics had stabilized, preload was optimized with a dextrose-based colloid solution. A continuous infusion of adenosine was then begun at doses of 25, 50, 75, and 100 microg/kg/min in a study group of 10 animals, while the remaining seven were monitored as controls. Hemodynamic parameters were followed throughout the study, with particular attention paid to pulmonary and systemic vascular resistance indices (PVRI and SVRI), right ventricle ejection fraction (REF), cardiac index (CI), and heart rate (HR). Cardiac index (CI) showed a tendency to increase during the adenosine infusion, as did REF and stroke index (SI), whereas PVRI and mean pulmonary pressure (MPAP) were decreased. There was a marked decrease in SVRI as a result of the adenosine, as there was in mean arterial pressure at the higher infusion rates. HR remained unchanged by the infusion. Discontinuation of the drug resulted in a rapid increase in MAP, SVRI, MPAP, HR, left ventricle stroke work index (LVSWI), and PVRI and in a modest decrease in CI. The continuous infusion of adenosine appears to cause an effective arterial vasodilation, with a consequent unloading of right-heart afterload. Its use may be beneficial in the treatment of increased pulmonary vascular resistance after right-heart failure.