Myocardial dysfunction in donor hearts. A possible etiology

Clinical pharmacology of cardiac cyclic AMP in human heart failure: too much or too little?

INTRODUCTION

Cyclic 3', 5'-adenosine monophosphate (cAMP) is a major signaling hub in cardiac physiology. Although cAMP signaling has been extensively studied in cardiac cells and animal models of heart failure (HF), not much is known about its actual amount present inside human failing or non-failing cardiomyocytes. Since many drugs used in HF work via cAMP, it is crucial to determine the status of its intracellular levels in failing vs. normal human hearts.

AREAS COVERED

Only studies performed on explanted/excised cardiac tissues from patients were examined. Studies that contained no data from human hearts or no data on cAMP levels per se were excluded from this perspective's analysis.

EXPERT OPINION

Currently, there is no consensus on the status of cAMP levels in human failing vs. non-failing hearts. Several studies on animal models may suggest maladaptive (e.g. pro-apoptotic) effects of cAMP on HF, advocating for cAMP lowering for therapy, but human studies almost universally indicate that myocardial cAMP levels are deficient in human failing hearts. It is the expert opinion of this perspective that intracellular cAMP levels are too low in human failing hearts, contributing to the disease. Strategies to increase (restore), not decrease, these levels should be pursued in human HF.

Cardiac RGS Proteins in Human Heart Failure and Atrial Fibrillation: Focus on RGS4

The regulator of G protein signaling (RGS) proteins are crucial for the termination of G protein signals elicited by G protein-coupled receptors (GPCRs). This superfamily of cell membrane receptors, by far the largest and most versatile in mammals, including humans, play pivotal roles in the regulation of cardiac function and homeostasis. Perturbations in both the activation and termination of their G protein-mediated signaling underlie numerous heart pathologies, including heart failure (HF) and atrial fibrillation (AFib). Therefore, RGS proteins play important roles in the pathophysiology of these two devasting cardiac diseases, and several of them could be targeted therapeutically. Although close to 40 human RGS proteins have been identified, each RGS protein seems to interact only with a specific set of G protein subunits and GPCR types/subtypes in any given tissue or cell type. Numerous in vitro and in vivo studies in animal models, and also in diseased human heart tissue obtained from transplantations or tissue banks, have provided substantial evidence of the roles various cardiomyocyte RGS proteins play in cardiac normal homeostasis as well as pathophysiology. One RGS protein in particular, RGS4, has been reported in what are now decades-old studies to be selectively upregulated in human HF. It has also been implicated in protection against AFib via knockout mice studies. This review summarizes the current understanding of the functional roles of cardiac RGS proteins and their implications for the treatment of HF and AFib, with a specific focus on RGS4 for the aforementioned reasons but also because it can be targeted successfully with small organic molecule inhibitors.

The therapeutic potential of targeting cardiac RGS4

G protein-coupled receptors (GPCRs) play pivotal roles in regulation of cardiac function and homeostasis. To function properly, every cell needs these receptors to be stimulated only when a specific extracellular stimulus is present, and to be silenced the moment that stimulus is removed. The regulator of G protein signaling (RGS) proteins are crucial for the latter to occur at the cell membrane, where the GPCR normally resides. Perturbations in both activation and termination of G protein signaling underlie numerous heart pathologies. Although more than 30 mammalian RGS proteins have been identified, each RGS protein seems to interact only with a specific set of G protein subunits and GPCR types/subtypes in any given tissue or cell type, and this applies to the myocardium as well. A large number of studies have provided substantial evidence for the roles various RGS proteins expressed in cardiomyocytes play in cardiac physiology and heart disease pathophysiology. This review summarizes the current understanding of the functional roles of cardiac RGS proteins and their implications for the treatment of specific heart diseases, such as heart failure and atrial fibrillation. We focus on cardiac RGS4 in particular, since this isoform appears to be selectively (among the RGS protein family) upregulated in human heart failure and is also the target of ongoing drug discovery efforts for the treatment of a variety of diseases.

Brain stem death induces pro-inflammatory cytokine production and cardiac dysfunction in sheep model

Introduction

Organs procured following brain stem death (BSD) are the main source of organ grafts for transplantation. However, BSD is associated with inflammatory responses that may damage the organ and affect both the quantity and quality of organs available for transplant. Therefore, we aimed to investigate plasma and bronchoalveolar lavage (BAL) pro-inflammatory cytokine profiles and cardiovascular physiology in a clinically relevant 6-h ovine model of BSD.

Methods

Twelve healthy female sheep (37–42 Kg) were anaesthetized and mechanically ventilated prior to undergoing BSD induction and then monitored for 6 h. Plasma and BAL endothelin-1 and cytokines (IL-1β, 6, 8 and tumour necrosis factor alpha (TNF-α)) were assessed by ELISA. Differential white blood cell counts were performed. Cardiac function during BSD was also examined using echocardiography, and cardiac biomarkers (A-type natriuretic peptide and troponin I were measured in plasma.

Results

Plasma concentrations big ET-1, IL-6, IL-8, TNF-α and BAL IL-8 were significantly (p < 0.01) increased over baseline at 6 h post-BSD. Increased numbers of neutrophils were observed in the whole blood (3.1 × 10⁹ cells/L [95% confidence interval (CI) 2.06–4.14] vs. 6 × 10⁹ cells/L [95%CI 3.92–7.97]; p < 0.01) and BAL (4.5 × 10⁹ cells/L [95%CI 0.41–9.41] vs. 26 [95%CI 12.29–39.80]; p = 0.03) after 6 h of BSD induction vs baseline. A significant increase in ANP production (20.28 pM [95%CI 16.18–24.37] vs. 78.68 pM [95%CI 53.16–104.21]; p < 0.0001) and cTnI release (0.039 ng/mL vs. 4.26 [95%CI 2.69–5.83] ng/mL; p < 0.0001), associated with a significant reduction in heart contractile function, were observed between baseline and 6 h.

Conclusions

BSD induced systemic pro-inflammatory responses, characterized by increased neutrophil infiltration and cytokine production in the circulation and BAL fluid, and associated with reduced heart contractile function in ovine model of BSD.

Concise Review: Criteria for Chamber-Specific Categorization of Human Cardiac Myocytes Derived from Pluripotent Stem Cells

Human pluripotent stem cell‐derived cardiomyocytes (PSC‐CMs) have great potential application in almost all areas of cardiovascular research. A current major goal of the field is to build on the past success of differentiation strategies to produce CMs with the properties of those originating from the different chambers of the adult human heart. With no anatomical origin or developmental pathway to draw on, the question of how to judge the success of such approaches and assess the chamber specificity of PSC‐CMs has become increasingly important; commonly used methods have substantial limitations and are based on limited evidence to form such an assessment. In this article, we discuss the need for chamber‐specific PSC‐CMs in a number of areas as well as current approaches used to assess these cells on their likeness to those from different chambers of the heart. Furthermore, describing in detail the structural and functional features that distinguish the different chamber‐specific human adult cardiac myocytes, we propose an evidence‐based tool to aid investigators in the phenotypic characterization of differentiated PSC‐CMs. Stem Cells2017;35:1881–1897

Management of Variations in Blood Pressure during Care of Organ Donors

The organ procurement coordinator commonly must correct and maintain the arterial blood pressure during donor care. This article reviews considerations in the accurate measurement of the blood pressure, causes of hypertension and hypotension, and desirable standards to use in order to provide adequate organ perfusion. Recommendations are presented for treatment of hypotension in a titrated response of intravenous fluids, inotropic support, and vasopressor infusion to maintain the mean arterial pressure above 65 mm Hg. Collaborative interaction between the coordinator and physician consultant remains important throughout management of blood pressure changes during donor care.

Effects of Gene Induction and Cytokine Production in Donor Care

Gene induction, cytokine production, and programmed neuronal and myocardial cell death are concerns that have entered the areas of donor evaluation and care over the past several years. Following ischemic or traumatic brain injury and the evolution of brain death, a large number of proteins (cytokines) are produced as part of a regional inflammatory response. These cytokines and related compounds appear to contribute to programmed death (apoptosis) of individual cells and the severe cardiac and hemodynamic changes often encountered during donor care. In addition, these cytokines and related compounds may sensitize donor organs so that a faster and more severe form of rejection occurs in the recipient. Although no directed therapy for these cytokine effects is presently available, the organ procurement coordinator should be aware of these issues and concerns as new treatment options evolve in the near future.

Treatment Goals during Care of Adult Donors That Can Influence Outcomes of Heart Transplantation

Myocardial dysfunction during care of adult donors can result from injury occurring before hospital admission or during the progression of brain death. Few evidence-based data correlate specific hemodynamic goals during donor care with outcomes of heart transplantation, although many recommendations exist. Spontaneous reversal of early heart damage or correction of poor cardiac performance can yield outcomes equivalent to outcomes in recipients who had ideal donors. Hemodynamic goals developed in the operating room can be applied in intensive care to improve outcomes of transplantation. These goals include maintenance of mean arterial pressure greater than 60 mm Hg, central venous pressure less than 12 mm Hg, cardiac output greater than 3.8 L/min, cardiac index greater than 2.1, and systemic vascular resistance between 800 and 1200 dyne · sec · cm−5. The ejection fraction and other echocardiographic data also provide helpful guidance when determining whether a heart is suitable for transplantation and during therapy. Titration of cardiovascular variables often requires invasive monitoring to ensure that cardiac preload, afterload, and contractility are optimal.

Altered Phosphatidylinositol 3-Kinase and Calcium Signaling in Cardiac Dysfunction After Brain Death in Rats

BACKGROUND

Phosphatidylinositol 3-kinase is involved in myocardial function, including contractility. To date, myocardial regulation by phosphatidylinositol 3-kinase after brain death has not been investigated. The present study using a brain death model was designed to examine the role of phosphatidylinositol 3-kinase in myocardial function after brain death.

METHODS

After anesthesia with sevoflurane, a Fogarty catheter was placed intracranially for induction of brain death. A conductance catheter was inserted into the left ventricle for measurement of myocardial function. Rats were assigned to the following groups: one group undergoing sham operation (with catheter placement but no brain death introduction); one group receiving saline before brain death; and one group receiving wortmannin, an inhibitor of phosphatidylinositol 3-kinase, before brain death. Various measurements, including mean blood pressure, heart rate, maximal rate of rise of left ventricular pressure, and ejection fraction, were obtained every 30 minutes for 6 hours after brain death. The phosphorylation status of Akt and phospholamban was determined 360 minutes after brain death.

RESULTS

After induction of brain death, rats showed significant decreases in blood pressure, maximal rate of rise of left ventricular pressure, and ejection fraction. Inhibition of phosphatidylinositol 3-kinase using wortmannin significantly improved these measurements, resulting in increased survival. Western blot analysis demonstrated that brain death increased Akt phosphorylation and decreased phospholamban phosphorylation; these effects were abolished by wortmannin.

CONCLUSIONS

Inhibition of phosphatidylinositol 3-kinase prevented myocardial dysfunction after brain death in association with inhibition of the decrease in phosphorylation of myocardial phospholamban, characteristic of brain death.

Brain-heart crosstalk: the many faces of stress-related cardiomyopathy syndromes in anaesthesia and intensive care

Neurogenic stress cardiomyopathy (NSC) is a well-known syndrome complicating the early phase after an acute brain injury, potentially affecting outcomes. This article is a review of recent data on the putative role of localization and lateralization of brain lesions in NSC, cardiac innervation abnormalities, and new polymorphisms and other genetic causes of the sympathetic nervous system over-activity. Concerns regarding the management of stress-related cardiomyopathy syndromes during the perioperative period are also discussed. Future clinical research should explore whether specific factors explain different patient susceptibilities to the disease and should be directed towards early identification and stratification of patients at risk, so that such patients can be more carefully monitored and appropriately managed in critical care and during the perioperative period.

Beta-adrenergic receptor polymorphisms and cardiac graft function in potential organ donors

Prior studies have demonstrated associations between beta-adrenergic receptor (βAR) polymorphisms and left ventricular dysfunction-an important cause of allograft nonutilization for transplantation. We hypothesized that βAR polymorphisms predispose donor hearts to LV dysfunction after brain death. A total of 1043 organ donors managed from 2001-2006 were initially studied. The following βAR single nucleotide polymorphisms were genotyped: β1AR 1165C/G (Arg389Gly), β1AR 145A/G (Ser49Gly), β2AR 46G/A (Gly16Arg) and β2AR 79C/G (Gln27Glu). In multivariable regression analyses, the β2AR46 SNP was significantly associated with LV systolic dysfunction, with each minor allele additively decreasing the odds for LV ejection fraction <50%. The β1AR1165 and β2AR46 SNPs were associated with higher dopamine requirement during the donor management period: donors with the GG and AA genotypes had ORs of 2.64 (95% CI 1.52-4.57) and 2.70 (1.07-2.74) respectively for requiring >10 μg/kg/min of dopamine compared to those with the CC and GG genotypes. However, no significant associations were found between βAR SNPs and cardiac dysfunction in 364 donors managed from 2007-2008, perhaps due to changes in donor management, lack of power in this validation cohort, or the absence of a true association. βAR polymorphisms may be associated with cardiac dysfunction after brain death, but these relationships require further study in independent donor cohorts.

A molecular approach to apoptosis in the human heart during brain death

BACKGROUND

Brain death induces changes in tissues and organs destined for transplant at the cell, molecular, and endocrine level including cell death through apoptosis. This study was designed to examine apoptotic damage in cardiac tissue obtained from brain dead donors.

METHODS

Fifty tissue specimens from the left ventricles of individual donors were processed to evaluate changes in the expression levels of five genes involved in apoptosis (BAX, BCL2, CASPASE 3, CYTOCHROME C, and FAS) using the real time-polymerase chain reaction technique. Expression levels were quantified by the relative standard method and results normalized to the levels recorded for the endogenous control peptidylprolyl isomerase A. The HIF1alpha gene was also determined to check for the possibility of hypoxic damage. Control ventricular tissue specimens were obtained from patients undergoing mitral valve replacement.

RESULTS

Using a mixed linear model it was determined that the sample type (donor vs. control patient) significantly affected (P<0.0001) expression levels of the genes examined reflected by their Ct values. Three of the genes (BAX, CASPASE 3, and FAS) showed significantly higher (Student's t test, P<0.05) expression levels (4.89-, 7.85-, and 12.14-fold endogenous control values, respectively) in donors compared with control patients (2.31-, 2.64-, and 3.57-fold endogenous control values, respectively) indicating the activation of apoptosis during brain death.

CONCLUSION

Our findings suggest the possibility of using antiapoptosis agents to prevent cardiac injury and improve posttransplant behavior.

Improvement of Donor Myocardial Function after Treatment of Autonomic Storm During Brain Death

BACKGROUND

In experimental brain death models, autonomic storm (AS) triggers severe myocardial dysfunction, which can be attenuated by pharmacologic treatment. The aim of this study was to determine the incidence of AS in a cohort of human organ donors and to evaluate the potential interest of AS treatment on myocardial function, cardiac harvesting and transplantation.

METHODS

The cohort consisted of 152 patients. Among them, 46 patients were initially considered as potential cardiac donors (main criteria: age < 60 years, no history of cardiac disease). AS diagnosis included increased systolic arterial pressure > 200 mm Hg associated with tachycardia >140 beats/min. Heart acceptance criteria were associated creatine kinase (CK), troponin Ic, and left ventricle ejection fraction (LVEF) estimated by echocardiography and visual inspection.

RESULTS

AS was observed in 29 patients (63%). Hypertension was treated in 12 patients (esmolol n = 6, urapidil n = 5, nicardipine). Cardiac harvesting was performed in 28 donors (61%). LVEFs were significantly higher after AS treatment (no AS: 55.4 +/- 13.4%, untreated AS: 49.0 +/- 18.8%, treated AS: 63.9+ +/- 10.3%, P = 0.049). AS treatment was found to be independently associated with LVEF in > 50% of the cases (P = 0.034). Treatment of AS or the lack of AS were associated with an increased probability of successful cardiac transplantation (OR = 8.8; 95% CI 2.1-38.3, P = 0.002).

CONCLUSIONS

Treatment of hypertension during AS may attenuate brain death-induced myocardial dysfunction and increase the number of available cardiac grafts.

Left ventricular myofilament dysfunction in rat experimental hypertrophy and congestive heart failure

It is currently unclear whether left ventricular (LV) myofilament function is depressed in experimental LV hypertrophy (LVH) or congestive heart failure (CHF). To address this issue, we studied pressure overload-induced LV hypertrophy (POLVH) and myocardial infarction-elicited congestive heart failure (MICHF) in rats. LV myocytes were isolated from control, POLVH, and MICHF hearts by mechanical homogenization, skinned with Triton, and attached to micropipettes that projected from a sensitive force transducer and high-speed motor. A subset of cells was treated with either unphosphorylated, recombinant cardiac troponin (cTn) or cTn purified from either control or failing ventricles. LV myofilament function was characterized by the force-[Ca(2+)] relation yielding Ca(2+)-saturated maximal force (F(max)), myofilament Ca(2+) sensitivity (EC(50)), and cooperativity (Hill coefficient, n(H)) parameters. POLVH was associated with a 35% reduction in F(max) and 36% increase in EC(50). Similarly, MICHF resulted in a 42% reduction in F(max) and a 30% increase in EC(50). Incorporation of recombinant cTn or purified control cTn into failing cells restored myofilament Ca(2+) sensitivity toward levels observed in control cells. In contrast, integration of cTn purified from failing ventricles into control myocytes increased EC(50) to levels observed in failing myocytes. The F(max) parameter was not markedly affected by troponin exchange. cTnI phosphorylation was increased in both POLVH and MICHF left ventricles. We conclude that depressed myofilament Ca(2+) sensitivity in experimental LVH and CHF is due, in part, to a decreased functional role of cTn that likely involves augmented phosphorylation of cTnI.

Human cardiac myosin autoantibodies impair myocyte contractility: a cause‐and‐effect relationship

The functional relevance of autoantibodies (Abs) against cardiac myosin (CM) in clinical idiopathic dilated cardiomyopathy (DCM) remains controversial. The study sought to determine effects of human Abs affinity-purified (AF) by immunoaffinity column chromotography on excitation-contraction coupling in isolated myocytes. Effects of CM-Abs from heart failure patients with DCM (n=19) and ischemic heart disease (IHD, n=19) on contractility, L-type Ca2+ current, and Ca2+ transients in continuously perfused rat ventricular myocytes were studied. Immunofluorescence studies using confocal microscopy were carried out to determine whether Abs were internalized. AF-Abs from either group did not differ in IgG titer but differed in their elution profiles. The IgG3 subclass response was higher in AF fractions from DCM (21%) than IHD (5%) patients. The Abs reduced the capacity of field-stimulated myocytes to contract in a dose-dependent manner. Inhibition of contraction, as a percentage of untreated cells, was greater with DCM than IHD-Abs (P=0.004), and the effect was independent of Ab titer. An increase in frequency of the beating myocytes (0.2 to 3.0 Hz) raised peak systolic and diastolic levels of [Ca2+]i of cells treated with DCM but not IHD-Abs (P<0.005). The AF-Abs were not internalized by myocytes and had no effect on L-type Ca2+ currents. The altered sensitivity of the myofilaments to [Ca2+]i by CM-Abs may represent a potential mechanism of autoantibody-mediated impairment in clinical DCM.

Transplantation using hearts from primary pulmonary hypertensive donors for recipients with a high pulmonary vascular resistance

BACKGROUND

Transplantation for patients with a high pulmonary vascular resistance (PVR) carries an increased risk of mortality and right heart failure following heart transplantation and continues to be a major problem. We evaluated the use of hearts from patients who underwent heart and lung transplantation for primary pulmonary hypertension (PPH) as part of a domino procedure because these hearts have hypertrophied right ventricles used to increased pulmonary pressures, but could have a compromised left ventricle or irreversible damage of the right ventricle.

METHODS

We reviewed 12 patients with PVR >4 Wood units who underwent orthotopic heart transplantation between 1989 and 1998 using hearts from donors with PPH as part of a domino procedure.

RESULTS

We studied 10 men and 2 women, mean age 42.9 years. Mean PVR was 5.3 (range, 4-9) Wood units. Mean ischemia time was 85.3 minutes, and mean donor age was 32 years. Actuarial survival was 75% at 1 year and 75% at 5 years. In the early post-operative period, 3 patients had temporary arrhythmias, 2 required permanent pacemaker implantation, 1 had atrial fibrillation, and 1 had ventricular tachycardia that required defibrillator implantation. At a mean follow-up of 7.8 years, 2 patients had developed asymptomatic transplant coronary disease (both at 8.5 years after transplantation), 1 moderate and 1 very mild; the rest had none. Mean left ventricular ejection fraction at latest follow-up was 70.1% (range, 63%-78%). Right ventricular function assessed clinically and by echocardiography was adequate in the short and long term.

CONCLUSIONS

Our results suggest that heart and lung recipients with PPH can provide useful donor hearts to patients with increased PVR and that these hearts function well in the intermediate and long term.

Renal effects of parenteral fish oil administered to heart-beating organ donors and renal-transplant recipients: a tolerance study

BACKGROUND & AIMS

Nutrition can interfere with organ function during the different stages of transplantation. Oral fish oil supplementation to kidney transplant recipients has been found to improve renal function. The aim of the present study was to determine the safety and tolerance of intravenous administration of fish-oil emulsion to heart-beating brain-dead donors and, subsequently, to the kidney recipients, and to assess its effects on renal function.

METHODS

A lipid emulsion enriched with omega-3 fatty acids (MLF 541) was given intravenously to 8 heart-beating, brain-dead organ donors for up to 4 h before organ harvesting and to the kidney recipients for 5 days postoperatively. Hemodynamic, biochemistry and hematological parameters were measured before and at the end of lipid administration in the donors and on posttransplantation days 1, 5, 30 and 180 in the recipients. Findings in the recipients were compared with a concurrent control group.

RESULTS

There were no significant changes in hemodynamic or laboratory parameters during the MLF infusion in the donors or the 5 days of MLF administration in the recipients. Blood urea nitrogen and serum creatinine levels decreased over time in both the study and control recipients (P < 0.05 for both), with no significant between-group difference at any of the time points studied.

CONCLUSIONS

Administration of MLF 541 is safe in organ donors and in kidney recipients. Further studies involving nutrients as pharmacological agents in organ transplantation are warranted.

Analyse des critères qui participent à la décision de prélèvement cardiaque chez les patients en état de mort encéphalique

OBJECTIVES

The number of cardiac transplantation procedures does not increase because of the lack of donor hearts despite an increase in the number of brain-dead organ donors. The criteria used to select a donor heart are not formally standardized. The aim of the present study was to analyze the criteria that contribute to the selection of a donor heart.

TYPE OF STUDY

Descriptive, retrospective study.

PATIENTS AND METHOD

Clinical parameters, the initial causes that lead to brain death, maximum doses of catecholamines, several biochemical markers of myocardial ischaemia/necrosis as well as several echocardiography criteria were extracted from a prospectively collected database. Univariate and multivariate (logistic regression) analyses were performed with the "harvested heart" as dependent variable and the above-cited independent variables.

RESULTS

One hundred and eighty consecutive brain-dead patients admitted from 1st October 1998 to 31st December 2000 out of which 112 gave at least one organ were analyzed. Among these 112 patients, 59 (39 males and 20 females) were pre-selected as potential heart donors. Only 44 hearts were harvested. Logistic regression analysis showed that harvesting of the heart was more probable if the donor were a male, had no left ventricle systolic wall motion abnormalities, had low doses of norepinephrine and low serum troponin Ic concentrations.

CONCLUSION

After an initial phase of selection, the final decision to harvest a heart is based on several criteria. These results should be an incentive to conceive a score that could allow a more formal decision process for heart harvesting.

Exercise after heart transplantation

Exercise intolerance in heart transplant recipients (HTR) has a multifactorial origin, involving complex interactions among cardiac, neurohormonal, vascular, skeletal muscle and pulmonary abnormalities. However, the role of these abnormalities may differ as a function of time after transplantation and of many other variables. The present review is aimed at evaluating the role of cardiac, pulmonary and muscular factors in limiting maximal aerobic performance of HTR, and the benefits of chronic exercise. Whereas pulmonary function does not seem to affect gas exchange until a critical value of diffusing lung capacity is attained, cardiac and skeletal muscle function deterioration may represent relevant factors limiting maximal and submaximal aerobic performance. Cardiac function is mainly limited by chronotropic incompetence and diastolic dysfunction, whereas muscle activity seems to be limited by impaired oxygen supply as a consequence of the reduced capillary network. The latter may be due to either immunosuppressive regimen or deconditioning. Endurance and strength training may greatly improve muscle function and maximal aerobic performance of HTR, and may also reduce side effects of immunosuppressive therapy and control risk factors for cardiac allograft vasculopathy. For the above reasons exercise should be considered an important therapeutic tool in the long-term treatment of heart transplant recipients.

Temporal changes in left ventricular systolic function in heart donors: results of serial echocardiography

BACKGROUND

Heart donor availability continues to limit cardiac transplantation rates and many donor hearts are not transplanted because of left ventricular dysfunction. The aim of this study was to determine whether intensive donor management results in improved left ventricular systolic function as measured by serial echocardiography.

METHODS

Using the California Transplant Donor Network Database, all donors who underwent serial echocardiography during donor management (from 1996 to 2000) were identified. The study includes those donors with ejection fractions <50% or regional wall-motion abnormalities shown on the initial echocardiogram. The database provides clinical data describing donor characteristics, treatments, and recipient outcomes. The mean ejection fractions at the first and second echocardiograms were compared using the Wilcoxon signed rank test.

RESULTS

In 13 of 16 subjects, initial ejection fractions were <50% and improved in 12 subjects after intensive donor management. Seventy-five percent of the donors received high-dose corticosteroids, 15 of 16 received dopamine, and none received thyroid hormone. In 12 subjects, the donor hearts were transplanted with a survival rate of 92% at an average follow-up of 16 months.

CONCLUSIONS

This pilot study indicates that in some cases, intensive donor management is associated with improved donor left ventricular function. Prospective studies are indicated to determine the predictors of improved donor left ventricular dysfunction and of recipient survival when sub-optimal hearts are transplanted.

Heart and brain: a case of focal myocytolysis in severe pneumococcal meningoencephalitis with review of the contemporary literature

We report electrocardiographic changes mimicking myocardial ischaemia in a 73-year-old man with fatal pneumococcal meningoencephalitis, present the autopsy-confirmed histological picture of extensive focal myocytolysis (contraction band necrosis) without myocardial infarction or myocarditis, and review the contemporary literature. Potentially reversible, probably non-ischaemic myocardial dysfunction may occur in association with acute noncardiac illnesses, such as brain injuries. Biochemical and morphological abnormalities in acutely failing hearts from head-injured organ donors point to specific pathophysiological mechanisms, which are different from heart failure from other causes. Sepsis-related factors may add to the myocardial dysfunction in patients with brain injury from meningoencephalitis.

Effects of gene induction and cytokine production in donor care

Gene induction, cytokine production, and programmed neuronal and myocardial cell death are concerns that have entered the areas of donor evaluation and care over the past several years. Following ischemic or traumatic brain injury and the evolution of brain death, a large number of proteins (cytokines) are produced as part of a regional inflammatory response. These cytokines and related compounds appear to contribute to programmed death (apoptosis) of individual cells and the severe cardiac and hemodynamic changes often encountered during donor care. In addition, these cytokines and related compounds may sensitize donor organs so that a faster and more severe form of rejection occurs in the recipient. Although no directed therapy for these cytokine effects is presently available, the organ procurement coordinator should be aware of these issues and concerns as new treatment options evolve in the near future.

Effects of BDF 9198 on left ventricular contractility in advanced spontaneously hypertensive rats with heart failure

In the first part of this study, we characterized 24-month-old Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs), their heart weights, and the responses of the isolated left ventricles to electrical stimulation. In the main part of the study, we tested whether the positive inotropic effects of BDF 9198, which prevents the closure of the cardiac sodium channel, were present in senescence and heart failure. Thus, we studied the effects of BDF 9198 on the left ventricle strips of 24-month-old WKy rats (senescence) and SHRs using contractility methods. In comparison with WKY rats, the left ventricles of 24-month-old SHRs were hypertrophied and had prolonged times to peak contraction. BDF 9198 (10(-8) to 10(-6) M) was a positive inotrope on the left ventricles of WKY rats, with a maximum augmenting effect of 122% with BDF 9198 at 10(-7) M. The magnitude of the augmenting effects of BDF 9198 were reduced in SHR heart failure, with a maximum augmenting effect of 26% at 10(-7) M. BDF 9198 at 10(-6) M attenuated the responses of the SHR left ventricle to electrical stimulation. In conclusion, the potential of drugs that prevent closure of the sodium channel as positive inotropes in the treatment of heart failure should be further considered.

Overexpression of the Na(+)/Ca(2+) exchanger and inhibition of the sarcoplasmic reticulum Ca(2+)-ATPase in ventricular myocytes from transgenic mice

BACKGROUND

Myocytes from failing hearts produce slower and smaller Ca(2+) transients associated with reduction in expression of sarcoplasmic reticulum (SR) Ca(2+) ATPase and an overexpression of Na(+)/Ca(2+) exchanger. Since the physiological role of both these proteins is competing for, and removing, Ca(2+) from the cytoplasm, overexpression of the exchanger may compensate for less effective SR Ca(2+) uptake. This study demonstrates this compensatory effect and provides a quantitative description of the results.

METHODS

Ventricular myocytes from transgenic mice overexpressing the Na(+)/Ca(2+) exchanger (TR) and nontransgenic littermates (NON) were used. Cell shortening, cytoplasmic [Ca] (using indo-1 AM) and electrophysiological parameters were monitored.

RESULTS

TR myocytes displayed faster Ca(2+) transients and twitches compared with NON myocytes. Superfusion with thapsigargin prolonged the time-course of Ca(2+) transients of TR myocytes until these were equal to the ones measured in NON myocytes. The amount of SR Ca(2+)-ATPase (SERCA) inhibition needed to obtain such transients was calculated as a function of V(max) for the Ca(2+) flux via SERCA and found to be 28%. In TR myocytes V(max) for the Ca(2+) flux via Na(+)/Ca(2+)exchange was 240% of NON myocytes. When Ca(2+) transients in TR myocytes were slowed by thapsigargin to similar values to the ones recorded in NON myocytes, SR Ca(2+) content was also correspondingly reduced.

CONCLUSIONS

The results suggest that in pathophysiological conditions where there is a reduction in SERCA function, overexpression of Na(+)/Ca(2+) exchanger can compensate and allow normal Ca(2+) homeostasis to be maintained. In mouse ventricular myocytes a 2.4-fold increase in Na(+)/Ca(2+) exchange activity compensates for a reduction in SERCA function by 28% so maintaining the duration of the Ca(2+) transient.

Activation of apoptotic and inflammatory pathways in dysfunctional donor hearts

BACKGROUND

Myocardial dysfunction is common after brain death, but the mechanisms remain unclear. Apoptosis is tightly regulated by enzymes termed the caspases. We have investigated the caspases involved in the terminal part of the apoptotic pathway in dysfunctional (nontransplanted) donor hearts and their relation to inflammatory markers and compared them to hearts with good ventricular function (transplanted donors).

METHODS

Thirty-one donor hearts assessed for transplantation were examined. Western blotting was used to measure pro-caspase-9, caspase-3, DFF45, the activated nuclease CPAN and poly (ADP-ribose) polymerase, a DNA repair enzyme inactivated by caspase-3. Caspase-3 activity was also measured. Histologic and immunocytochemical analysis for HLA Class II and Real Time polymerase chain reaction for tumor necrosis factor-alpha and interleukin 6 were performed to detect inflammatory activation.

RESULTS

Cleaved caspase-9 was higher (5.53+/-0.6 vs. 3.64+/-0.4 O.D. units, P<0.01) in nontransplanted compared with transplanted donors and there was a trend for higher pro-caspase-9 (5.20+/-1.0 vs. 4.22+/-0.4 O.D. units, P=NS). Levels of pro-caspase-3 were higher in nontransplanted (9.66+/-0.5 vs. 5.15+/-0.5 O.D. units, P<0.00001) donors and cleavage products of caspase-3 were elevated in 14 of 14 nontransplanted and 2 of 17 transplanted donors. Intact DFF-45 (8.94+/-0.36 vs. 6.14+/-0.30 O.D. units, P<0.000005), its spliced product (2.38+/-0.35 vs. 0.4+/-0.21 O.D. units, P=0.0001) and the nuclease caspase-activated nuclease (2.01+/-0.3 vs. 0.66+/-0.16 OD units, P=0.001) were higher in nontransplanted donors. The caspase-3 substrate poly (ADP-ribose) polymerase was higher in nontransplanted (1.16+/-0.13 vs. 0.61+/-0.22 O.D. units, P=0.57) donors.

CONCLUSIONS

The caspases are elevated in dysfunctional donor hearts compared with hearts with good ventricular function with a possible link to inflammatory activation supporting the concept that brain death causes inflammatory activation which can lead to apoptosis with a possible important effect on function.

Sarcolemmal Na+/H+ exchanger activity and expression in human ventricular myocardium

OBJECTIVES

To determine sarcolemmal Na+/H+ exchanger (NHE) activity and expression in human ventricular myocardium.

BACKGROUND

Although the sarcolemmal NHE has been implicated in various physiological and pathophysiological phenomena in animal studies, its activity and expression in human myocardium have not been studied.

METHODS

Ventricular myocardium was obtained from unused donor hearts with acute myocardial dysfunction (n = 5) and recipient hearts with chronic end stage heart failure (n = 11) through a transplantation program. Intracellular pH (pHi) was monitored in enzymatically isolated single ventricular myocytes by microepifluorescence. As the index of sarcolemmal NHE activity, the rate of H+ efflux at a pHi of 6.90 J(H6.9)) was determined after the induction of intracellular acidosis in bicarbonate-free medium. Na+/H+ exchanger isoform 1 (NHE1) expression in ventricular myocardium was determined by immunoblot analysis.

RESULTS

Human ventricular myocytes exhibited readily detectable sarcolemmal NHE activity after the induction of intracellular acidosis, and this activity was suppressed by the NHE1-selective inhibitor HOE-642 (cariporide) at 1 micromol/L. Sarcolemmal NHE activity of myocytes was significantly greater in recipient hearts (JH6.9 = 1.95+/-0.18 mmol/L/min) than it was in unused donor hearts (J(H6.9 = 1.06+/-0.15 mmol/L/min). In contrast, NHE1 protein was expressed in similar abundance in ventricular myocardium from both recipient and unused donor hearts.

CONCLUSIONS

Sarcolemmal NHE activity of human ventricular myocytes arises from the NHE1 isoform and is inhibited by HOE-642. Sarcolemmal NHE activity is significantly greater in recipient hearts with chronic end-stage heart failure than it is in unused donor hearts, and this difference is likely to arise from altered posttranslational regulation.

Biphasic response after brain death induction: prominent part of catecholamines release in this phenomenon

BACKGROUND

The physiopathology of hemodynamic instability that occurs after brain death remains unknown. The aim of this study was to examine the initial response to brain death induction.

METHODS

After anesthesia and monitoring, 16 pigs were randomized into a control group (C, n = 8) and a brain death group (BD, n = 8). We inflated a subdural catheter balloon to induce brain death. We analyzed hemodynamic and plasmatic biochemical data for 180 minutes after brain death induction. Energetic compounds were measured. We expressed the results in comparison with the C group.

RESULTS

The C group remained stable. One minute after brain death, the Cushing reflex appeared, with a hyperdynamic response to plasma catecholamines levels increasing (norepinephrine and epinephrine, 3.1-fold, p = 0. 02, and 3.8-fold, p = 0.07, respectively). After a return to baseline, we recorded a second hyperdynamic profile 120 minutes later. At this time, a second peak of catecholamines appeared (6. 3-fold, p = 0.04, and 9.1-fold, p = 0.02, concerning norepinephrine and epinephrine). At the same time, we observed brief myocardial lactate production (+175%, p < 0.01), with a rise of troponine I (+64%, p = 0.03). The energetic index was similar in both groups: 0. 85 (+/-0.02) in the C group vs 0.87 (+/-0.02) in the BD group.

CONCLUSIONS

In this model, biphasic plasmatic catecholamine release appears to primarily explain the physiopathology of the hemodynamic response to brain death induction.

Management of variations in blood pressure during care of organ donors

The organ procurement coordinator commonly must correct and maintain the arterial blood pressure during donor care. This article reviews considerations in the accurate measurement of the blood pressure, causes of hypertension and hypotension, and desirable standards to use in order to provide adequate organ perfusion. Recommendations are presented for treatment of hypotension in a titrated response of intravenous fluids, inotropic support, and vasopressor infusion to maintain the mean arterial pressure above 65 mm Hg. Collaborative interaction between the coordinator and physician consultant remains important throughout management of blood pressure changes during donor care.