Arterial Compliance is an Independent Factor Predicting Acute Hemodynamic Performance of Intra-aortic Balloon Counterpulsation

Data concerning the effect of arterial compliance (AC) on hemodynamics during intra-aortic balloon counterpulsation (IABC) are lacking. This study examines the effect of AC on acute hemodynamics induced by IABC in 15 patients with post-infarction cardiogenic shock. AC was estimated by aortic pulse wave analysis using the reflection time index (RTI). Measurements were obtained once per day during IABC. The % reduction in systolic aortic pressure (ΔSAP), end-diastolic aortic pressure (ΔEDAP) and the peak aortic diastolic augmentation (PADA) were used as performance indices of IABC; 107 sets of measurements were obtained. Multivariate analysis indicated an independent association of each IABC performance index with AC (p<0.05). A high AC group (RTI≤20.6%, n=40) and a low AC group (RTI>20.6%, n=67) were obtained. ΔSAP, ΔEDAP and PADA were significantly higher in the low AC group by almost 75%, 54.6% and 11,3% (p<0.03), while arterial blood pressure did not significantly differ. Arterial compliance is an independent factor affecting hemodynamics during IABC. RTI values higher than 20.6% may predict a better acute hemodynamic response to IABC.

A Decision Support System for the Treatment of Patients with Ventricular Assist Device Support

Background: Heart failure (HF) is affecting millions of people every year and it is characterized by impaired ventricular performance, exercise intolerance and shortened life expectancy. Despite significant advancements in drug therapy, mortality of the disease remains excessively high, as heart transplant remains the gold standard treatment for end-stage HF when no contraindications subsist. Traditionally, implanted Ventricular Assist Devices (VADs) have been employed in order to provide circulatory support to patients who cannot survive the waiting time to transplantation, reducing the workload imposed on the heart. In many cases that process could recover its contractility performance.

Objectives: The SensorART platform focuses on the management and remote treatment of patients suffering from HF. It provides an inter-operable, extendable and VAD-independent solution, which incorporates various hardware and software components in a holistic approach, in order to improve the quality of the patients’ treatment and the workflow of the specialists. This paper focuses on the description and analysis of Specialist’s Decision Support System (SDSS), an innovative component of the SensorART platform.

Methods: The SDSS is a Web-based tool that assists specialists on designing the therapy plan for their patients before and after VAD implantation, analyzing patients’ data, extracting new knowledge, and making informative decisions.

Results: SDSS offers support to medical and VAD experts through the different phases of VAD therapy, incorporating several tools covering all related fields; Statistics, Association Rules, Monitoring, Treatment, Weaning, Speed and Suction Detection.

Conclusions: SDSS and its modules have been tested in a number of patients and the results are encouraging.

Cardiosphere-derived progenitor cells for myocardial repair following myocardial infarction

In the recent years, the existence of cardiac regeneration in mammalian models and even humans has been confirmed in several, carefully designed and executed studies. However, the intrinsic rate of cardiomyocyte renewal is not sufficient to replenish the large number of cells lost after a major injury in the heart, such as myocardial infarction. Therefore, exogenously administered cells with progenitor properties have been used in order to augment this process. From the several candidate cell populations, cardiac derived progenitor cells appear particularly attractive for this purpose, based on data from many experimental studies but also preliminary clinical applications. Cardiosphere-derived cells are a mixed cell population that has shown great potential in stimulating endogenous mechanisms of cardiac repair and attenuating adverse remodeling of the heart. In the present review, we discuss in detail the existing evidence regarding the therapeutic role of cardiosphere-derived progenitor cell administration in the post-myocardial infarction setting. Proof-of-concept studies in rodents, as well as more clinically relevant experiments in large animal models, have provided consistent results regarding the potential of these cells to improve cardiac structure and function after myocardial infarction. Existing data about the underlying mechanisms that are implicated in myocardial regeneration triggered by these cells are presented, as well as preliminary data from clinical applications and future perspectives of this novel therapeutic option.

Beneficial effects of combined exercise training on early recovery cardiopulmonary exercise testing indices in patients with chronic heart failure

PURPOSE

Exercise training induces several beneficial effects in patients with chronic heart failure (CHF). This study investigated the effects of high-intensity aerobic interval training (AIT) compared with combined AIT and strength training (COM) on early ventilatory and metabolic recovery pattern after symptom-limited cardiopulmonary exercise testing (CPET) in CHF patients.

METHODS

Stable CHF patients (N = 42; 54 ± 10 years [mean ± SD], 35 males) participated in an exercise training program for 12 weeks, 3 times per week. Participants were randomly assigned to either AIT (n = 20) or COM group (n = 22). Cardiopulmonary exercise testing was performed before and after completion of the program. Primary measurements included absolute and percentage difference of oxygen uptake, carbon dioxide output, minute ventilation ((Equation is included in full-text article.)E), tidal volume (VT), respiratory rate, and the first-degree slope of oxygen uptake ((Equation is included in full-text article.)O2/t slope) and carbon dioxide output ((Equation is included in full-text article.)CO2/t slope) during the first minute of recovery after maximal exercise.

RESULTS

The COM group had a greater improvement in the absolute and the percentage difference of (Equation is included in full-text article.)E (P = .03 and P = .04, respectively) and respiratory rate (P = .02 and P = .01, respectively) during the first minute of recovery period after exercise compared with the AIT group alone. No significant changes were noted for VT measurements. A significant increase in (Equation is included in full-text article.)CO2/t slope was observed in COM compared with the AIT group (P = .01). There was a trend for a greater increase in (Equation is included in full-text article.)O2/t slope in the COM group (P = .07).

CONCLUSIONS

The addition of strength training to AIT induces significant beneficial effects in terms of ventilatory and metabolic recovery kinetics than AIT alone in CHF patients, possibly indicating greater ventilatory efficiency and metabolic improvement.

Neuroticism personality trait is associated with Quality of Life in patients with Chronic Heart Failure

AIM: To evaluate Quality of life (QoL) in chronic heart failure (CHF) in relation to Neuroticism personality trait and CHF severity.

METHODS: Thirty six consecutive, outpatients with Chronic Heart Failure (6 females and 30 males, mean age: 54 ± 12 years), with a left ventricular ejection fraction ≤ 45% at optimal medical treatment at the time of inclusion, were asked to answer the Kansas City Cardiomyopathy Questionnaire (KCCQ) for Quality of Life assessment and the NEO Five-Factor Personality Inventory for personality assessment. All patients underwent a symptom limited cardiopulmonary exercise testing on a cycle-ergometer, in order to access CHF severity. A multivariate linear regression analysis using simultaneous entry of predictors was performed to examine which of the CHF variables and of the personality variables were correlated independently to QoL scores in the two summary scales of the KCCQ, namely the Overall Summary Scale and the Clinical Summary Scale.

RESULTS: The Neuroticism personality trait score had a significant inverse correlation with the Clinical Summary Score and Overall Summary Score of the KCCQ (r = -0.621, P < 0.05 and r = -0.543, P < 0.001, respectively). KCCQ summary scales did not show significant correlations with the personality traits of Extraversion, Openness, Conscientiousness and Agreeableness. Multivariate linear regression analysis using simultaneous entry of predictors was also conducted to determine the best linear combination of statistically significant univariate predictors such as Neuroticism, VE/VCO₂ slope and VO₂ peak, for predicting KCCQ Clinical Summary Score. The results show Neuroticism (β = -0.37, P < 0.05), VE/VCO₂ slope (β = -0.31, P < 0.05) and VO₂ peak (β = 0.37, P < 0.05) to be independent predictors of QoL. In multivariate regression analysis Neuroticism (b = -0.37, P < 0.05), the slope of ventilatory equivalent for carbon dioxide output during exercise, (VE/VCO₂ slope) (b = -0.31, P < 0.05) and peak oxygen uptake (VO₂ peak), (b = 0.37, P < 0.05) were independent predictors of QoL (adjusted R2 = 0.64; F = 18.89, P < 0.001).

CONCLUSION: Neuroticism is independently associated with QoL in CHF. QoL in CHF is not only determined by disease severity but also by the Neuroticism personality trait.

Abstract 19: Reversal of Adverse Remodeling in Chronic Rat Myocardial Infarction by Cardiospheres: Role of the Tgf-beta Pathway

Background: Self-assembling three-dimensional cardiospheres (CSps) are known to be effective in improving function and attenuating remodeling as adjunctive therapy in acute myocardial infarction (MI), and they exert functional benefits in large animals with convalescent MI. The effect of cardiospheres in chronically-remodeled myocardium post-MI, and the mechanisms of benefit are unknown.

Methods: We performed permanent LAD ligation in Wistar Kyoto female rats. One month later the animals underwent repeat thoracotomy and were randomly assigned to one of two groups: vehicle-treated controls, or CSp-treated, where CSps (at a seeding dose of 2X10 6 cells) were injected in the peri-infarct area. Mechanisms were also probed in vitro .

Results: CSps downregulated the canonical Tgfβ1-smad2/3 pathway in co-cultures with fibroblasts and reduced fibroblast proliferation in vitro . Soluble endoglin, abundantly expressed in CSps, was found to limit the Tgfβ1-induced fibrosis in a dose-dependent manner. In vivo , left ventricular function gradually increased one month post-CSp injection with further improvement after up to six months of follow up. Immunoblots verified Tgfβ1/smad cascade downregulation one month post-CSp injection and upregulation of soluble endoglin. In addition, scar mass was reduced one month post-CSp injection compared to controls. Collagen density was attenuated within the infarcted region of the treated group, while immunostaining showed enhanced vessel density in the same region. Six months post-transplantation, cardiomyocyte hypertrophy was reduced in the CSp-treated group compared to control.

Conclusions: CSps injected into the peri-infarct zone enhance angiogenesis and reduce established fibrosis in chronically-infarcted myocardium, thereby reversing, at least partially, adverse remodeling of the heart. The underlying mechanism involves modification of Tgfβ1/smad signaling, a key pathway in the cardiac response to injury.

Angiogenesis, cardiomyocyte proliferation and anti-fibrotic effects underlie structural preservation post-infarction by intramyocardially-injected cardiospheres

OBJECTIVE

We sought to understand the cellular and tissue-level changes underlying the attenuation of adverse remodeling by cardiosphere transplantation in acute myocardial infarction (MI).

BACKGROUND

Cardiospheres (CSps) are heart-derived multicellular clusters rich in stemness and capable of multilineage differentiation. Post-MI CSp transplantation improves left ventricular (LV) function and attenuates remodeling in both small and large animal studies. However, the mechanisms of benefit have not yet been fully elucidated.

METHODS

Four groups were studied: 1) "Sham" (Wistar Kyoto rats with thoracotomy and ligature without infarction); 2) "MI" (proximal LAD ligation with peri-infarct injection of vehicle); 3) "MI+CSp" (MI with cardiospheres injected in the peri-infarct area); 4) "Small MI" (mid-LAD ligation only).

RESULTS

In vivo 1 week after CSp transplantation, LV functional improvement was associated with an increase in cardiomyocyte proliferation. By 3 weeks, microvessel formation was enhanced, while cardiomyocyte hypertrophy and regional fibrosis were attenuated. Collagen deposition was reduced, collagen degradation was enhanced, and MMPs were upregulated. The beneficial effects of CSp transplantation were not observed in the Small MI group, indicating that the effects are not solely due to CSp-induced cardioprotection. In vitro, CSp-conditioned media reduced collagen production in coculture with fibroblasts and triggered neoangiogenesis in an ex vivo aortic ring assay.

CONCLUSION

Cardiospheres enhance cardiomyocyte proliferation and angiogenesis, and attenuate hypertrophy and fibrosis, in the ischemic myocardium. These synergistic effects underlie the attenuation of adverse remodeling by cardiospheres.

Respiratory drive and breathing pattern abnormalities are related to exercise intolerance in chronic heart failure patients

BACKGROUND

Patients with chronic heart failure (CHF) are characterized by exercise intolerance and ventilatory abnormalities that are related to poor prognosis. We hypothesized that CHF patients have increased respiratory drive and abnormal breathing pattern during exercise in relation to disease severity.

MATERIALS AND METHODS

The study population consisted of 219 stable CHF patients and 30 healthy control subjects. All subjects underwent a symptom-limited cardiopulmonary exercise testing (CPET), pulmonary function tests, measurement of the maximal inspiratory pressure (PImax) and respiratory drive (P0.1). Measurements included peak oxygen uptake ( [Formula: see text] peak, ml/kg/min). Respiratory drive was measured by mouth occlusion pressure P0.1 and P0.1/PImax ratio at rest, and by mean inspiratory flow (VT/TI) at rest and during exercise. CHF patients were divided into 3 groups according to [Formula: see text] peak (Group A: >20, Group B: 20-16 and Group C: <16ml/kg/min).

RESULTS

CHF patients presented higher P0.1/PImax (4.1±3.6 vs 3.0±1.5, p=0.007) and VT/TI at rest (0.48±0.14 vs 0.41±0.10, L/s respectively, p=0.004) and lower VT/TI at peak exercise (2.17±0.66 vs 2.56±0.73, L/s, p=0.009) compared to controls. P0.1/PImax was higher in CHF Group C vs B vs A (4.9±2.9 vs 3.6±1.8 vs 3.1±1.8, respectively, p<0.001), while VT/TI at peak exercise was lower (1.71±0.43 vs 2.15±0.52 vs 2.65±0.64, L/s, respectively, p<0.001).

CONCLUSIONS

CHF patients present increased respiratory drive at rest and abnormal breathing pattern during exercise in relation to CHF severity.

Peripheral muscle microcirculatory alterations in patients with pulmonary arterial hypertension: a pilot study

BACKGROUND

Pulmonary microcirculation abnormalities are the main determinants of pulmonary arterial hypertension (PAH) pathophysiology. We hypothesized that PAH patients have peripheral tissue microcirculation alterations that might benefit from hyperoxic breathing. We evaluated peripheral muscle microcirculation with near-infrared spectroscopy, before and after hyperoxic breathing.

METHODS

Eight PAH subjects, 8 healthy subjects (controls) matched for age, sex, and body mass index, and 16 subjects with chronic heart failure and matched for functional capacity with the PAH subjects underwent near-infrared spectroscopy. Tissue O(2) saturation, defined as the hemoglobin saturation (%) in the microvasculature compartments, was measured on the thenar muscle. Then the 3-min brachial artery occlusion technique was applied before, during, and after 15 min of breathing 100% O(2). We calculated the oxygen consumption rate (%/min), the reactive hyperemia time, and the time needed for tissue O(2) saturation to reach its baseline value after the release of the occlusion.

RESULTS

Compared to the controls, the PAH subjects had a significantly lower resting tissue O(2) saturation (65.8 ± 14.9% vs 82.1 ± 4.0%, P = .005), a trend toward a lower oxygen consumption rate (35.3 ± 9.1%/min vs 43.4 ± 19.7%/min, P = .60), and a significantly higher reactive hyperemia time (3.0 ± 0.6 min vs 2.0 ± 0.3 min, P < .001). The PAH subjects also had lower tissue O(2) saturation (P = .08), lower peripheral arterial oxygen saturation (P = .01), and higher reactive hyperemia time (P = .02) than the chronic heart failure subjects. After hyperoxic breathing, the PAH subjects had increased tissue O(2) saturation (65.8 ± 14.9% to 71.4 ± 14.5%, P = .01), decreased oxygen consumption rate (35.3 ± 9.1%/min to 25.1 ± 6.6%/min, P = .01), and further increased reactive hyperemia time (3.0 ± 0.6 min to 4.2 ± 0.7 min, P = .007).

CONCLUSIONS

The PAH subjects had substantial impairments of peripheral muscle microcirculation, decreased tissue O(2) saturation (possibly due to hypoxemia), slower reactive hyperemia time, (possibly due to endothelium dysfunction), and peripheral systemic vasoconstriction. Acute hyperoxic breathing improved resting tissue O(2) saturation (an expression of higher oxygen delivery) and decreased the oxygen consumption rate and reactive hyperemia time during reperfusion, possibly due to increased oxidative stress and evoked vasoconstriction.

Cardiomyocyte proliferation vs progenitor cells in myocardial regeneration: The debate continues

In recent years, several landmark studies have provided compelling evidence that cardiomyogenesis occurs in the adult mammalian heart. However, the rate of new cardiomyocyte formation is inadequate for complete restoration of the normal mass of myocardial tissue, should a significant myocardial injury occur, such as myocardial infarction. The cellular origin of postnatal cardiomyogenesis in mammals remains a controversial issue and two mechanisms seem to be participating, proliferation of pre-existing cardiomyocytes and myogenic differentiation of progenitor cells. We will discuss the relative importance of these two processes in different settings, such as normal ageing and post-myocardial injury, as well as the strengths and limitations of the existing experimental methodologies used in the relevant studies. Further clarification of the mechanisms underlying cardiomyogenesis in mammals will open the way for their therapeutic exploitation in the clinical field, with the scope of myocardial regeneration.

The Greek cardiac magnetic resonance experience: a comparison with the EuroCMR Registry

INTRODUCTION

We carried out an evaluation of Greek cardiovascular magnetic resonance (CMR) data in order to analyse the indications, safety, quality, and impact on management, in comparison with the EuroCMR registry.

METHODS

A retrospective analysis was performed of Greek CMR data from patients referred from 6 Greek cardiac clinics to 6 different MRI units in Athens that offer CMR services. A total of 10,000 CMR examinations carried out from 1995 to 2010 were evaluated retrospectively and included in the study.

RESULTS

Fifty percent of patients underwent evaluation for thalassaemic syndromes. In the remaining 50%, the most important indications were: a) workup of myocarditis/cardiomyopathies (40%), b) assessment of viability (5%), and c) congenital heart disease (5%). Image quality was good in 75%, moderate in 15%, and inadequate in 10% of cases. Complications occurred in 0.02%, including allergic reactions, dyspnoea, and panic attack. No death or cardiac complication was observed during or due to CMR; however, stress testing was not used in any of the cases. In 65% of all CMR studies, the initial diagnosis made by a non SCMR-trained person had no impact on the patients' management and did not offer any diagnostic contribution to referral clinicians, discouraging them from referring for CMR again. However, after the re-evaluation performed by an SCMR-trained person, the results of the Greek CMR were capable of satisfying all imaging needs in a percentage of patients equivalent to that presented in the EuroCMR registry (83% vs. 86%, p=NS), so that no further non-invasive imaging procedures would be required after CMR.

CONCLUSIONS

Thalassaemia and myocarditis were the most frequent CMR indications in Greece. However, the lack of training according to SCMR guidelines lowers the diagnostic efficacy significantly and leads to under-use of the technique.

Hormonal imbalance in relation to exercise intolerance and ventilatory inefficiency in chronic heart failure

BACKGROUND

Skeletal muscle wasting is associated with altered catabolic/anabolic balance and poor prognosis in patients with chronic heart failure (CHF). This study evaluated catabolic and anabolic abnormalities in relation to disease severity in CHF patients.

METHODS

Forty-two stable CHF patients (34 men; aged 56±12 years, body mass index, 27±5 kg/m2) receiving optimal medical treatment underwent incremental symptom-limited cardiopulmonary exercise testing on a cycle ergometer. Blood samples were drawn within 10 days to determine serum cortisol, plasma adrenocorticotropin (ACTH), and serum dehydroepiandrosterone sulfate, insulin-like growth factor 1, growth hormone, and total testosterone in men.

RESULTS

Patients with higher cortisol levels presented with impaired peak oxygen uptake (Vo2 peak: 18.3±3.9 vs. 14.2±3.7 ml/kg/min, p<0.01), ventilatory (Ve) response to exercise (Ve/carbon dioxide output [Vco2] slope: 36±6 vs 30±5, p<0.01), and chronotropic reserve ([peak heart rate [HR]--resting HR/220--age--resting HR]×100%: 40±19 vs. 58±18, p=0.01) compared with those with lower serum cortisol. Cortisol was inversely correlated with Vo2 peak, (r = -0.57; p<0.01) and was correlated with Ve/Vco2 slope (r = 0.47; p<0.01) and chronotropic reserve (r = 0.44; p = 0.017). In multivariate regression analysis, cortisol was an independent predictor of Vo2peak (R2 = 0.365, F = 12.5, SE = 3.4; p≤0.001) and Ve/Vco2 slope (R2 = 0.154; F = 8.5; SE = 5.96; p = 0.006), after accounting for age, body mass index, sex, CHF etiology, creatinine, left ventricular ejection fraction, and ACTH in all patients. In men, cortisol and dehydroepiandrosterone levels were both independent predictors of Vo2peak (R2 = 0.595, F = 24.53, SE = 2.76; p<0.001) after accounting also for all measured hormones, whereas cortisol remained the only independent predictor of Ve/Vco2 slope (R2 = 0.133; F = 6.1; SE = 6.2; p = 0.02).

CONCLUSIONS

Enhanced catabolic status is significantly associated with exercise intolerance, ventilatory inefficiency, and chronotropic incompetence in CHF patients, suggesting a significant contributing mechanism to their limited functional status.

Allogeneic cardiospheres safely boost cardiac function and attenuate adverse remodeling after myocardial infarction in immunologically mismatched rat strains

OBJECTIVES

We sought to characterize the immunologic profile of allogeneic cardiospheres, which are 3-dimensional, self-assembling, cardiac-derived microtissues, and to evaluate their safety and efficacy in repairing ischemic heart tissue.

BACKGROUND

Intramyocardial injection of autologous cardiospheres ameliorates remodeling and improves global function in infarcted myocardium. It is as yet unknown whether allogeneic cardiospheres are similarly effective without eliciting deleterious immune reactions.

METHODS

We expanded cardiospheres from male Wistar Kyoto rat hearts and injected them surgically in the peri-infarct zone of Wistar Kyoto (syngeneic group, n = 28) and Brown Norway female rats (allogeneic group, n = 29). Female rats from both strains (n = 37) injected with normal saline served as controls.

RESULTS

In vitro, cardiospheres expressed a low immunogenic profile and inhibited proliferation of alloreactive T cells. In vivo, cell engraftment was similar in the syngeneic and allogeneic groups 1 week and 3 weeks after transplantation. Reductions in scar size and scar collagen content and increases in viable mass in the risk region were accompanied by improvements in left ventricular function and attenuation of left ventricle remodeling that were sustained during 6 months of follow up. Transplantation of allogeneic cardiospheres increased tissue expression of the regenerative growth factors vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1, stimulating angiogenesis. Syngeneic and allogeneic cardiospheres attenuated the inflammatory response observed histologically in the peri-infarct region.

CONCLUSIONS

Allogeneic cardiospheres increase viable myocardium, decrease scar, improve function, and attenuate adverse remodeling in the infarcted rat heart, without deleterious immunological sequelae. These observations lay the groundwork for developing cardiospheres as a novel off-the-shelf microtissue product for myocardial regeneration.

Cellular bioenergetics is an important determinant of the molecular imaging signal derived from luciferase and the sodium-iodide symporter

RATIONALE

Molecular imaging is useful for longitudinal assessment of engraftment. However, it is not known which factors, other than cell number, can influence the molecular imaging signal obtained from reporter genes.

OBJECTIVE

The effects of cell dissociation/suspension on cellular bioenergetics and the signal obtained by firefly luciferase and human sodium-iodide symporter labeling of cardiosphere-derived cells were investigated.

METHODS AND RESULTS

(18)Fluorodeoxyglucose uptake, ATP levels, (99m)Tc-pertechnetate uptake, and bioluminescence were measured in vitro in adherent and suspended cardiosphere-derived cells. In vivo dual-isotope single-photon emission computed tomography/computed tomography imaging or bioluminescence imaging (BLI) was performed 1 hour and 24 hours after cardiosphere-derived cell transplantation. Single-photon emission computed tomography quantification was performed using a phantom for signal calibration. Cell loss between 1 hour and 24 hours after transplantation was quantified by quantitative polymerase chain reaction and ex vivo luciferase assay. Cell dissociation followed by suspension for 1 hour resulted in decreased glucose uptake, cellular ATP, (99m)Tc uptake, and BLI signal by 82%, 43%, 42%, and 44%, respectively, compared with adherent cells, in vitro. In vivo (99m)Tc uptake was significantly lower at 1 hour compared with 24 hours after cell transplantation in the noninfarct (P<0.001; n=3) and infarct (P<0.001; n=4) models, despite significant cell loss during this period. The in vivo BLI signal was significantly higher at 1 hour than at 24 hours (P<0.01), with the BLI signal being higher when cardiosphere-derived cells were suspended in glucose-containing medium compared with saline (PBS).

CONCLUSIONS

Adhesion is an important determinant of cellular bioenergetics, (99m)Tc-pertechnetate uptake, and BLI signal. BLI and sodium-iodide symporter imaging may be useful for in vivo optimization of bioenergetics in transplanted cells.

Abstract 114: Allogeneic Cardiosphere-Derived Cells Are Safe and Effective in a Pig Model of Myocardial Infarction

Allogeneic cardiosphere-derived cells (CDCs) have proven safe and effective in a small animal model of myocardial infarction (MI), and have been shown to act primarily via paracrine mechanisms to stimulate endogenous regeneration. The present translational study tested allogeneic CDCs in a large animal model (mini-pigs).

To establish a robust allogeneic model, all pigs were swine leukocyte antigen (SLA) typed by PCR. A male donor and female recipients with full SLA I, II mismatch were used. Pigs underwent balloon occlusion of the LAD for 2.5 hours, followed by reperfusion. Two weeks later, 12.5 million CDCs (n=8) or vehicle (n=6) were infused. Animals were sacrificed 2 weeks or 2 months post-infusion to assess the cellular (histology using a clinical rejection scale) and humoral (donor-specific antibodies, complement-dependent cytotoxicity) immune responses, as well as cardiac function (left ventriculography, hemodynamics, morphometry). Numerous in-life assessments for safety were performed and CDC engraftment was assessed by FISH for Y chromosome.

All immunological assays indicated an undetectable response to CDCs. Cardiac enzymes and systemic inflammation showed no differences between groups. There were no systemic histological findings related to CDCs. CDCs did not permanently engraft, with <0.1% persisting 2 weeks post-infusion and none evident 2 months post. Despite evanescent engraftment, functional benefits were seen following infusion of CDCs. Ejection fraction (EF) and infarct size (IS) were significantly improved in CDC-treated animals compared to vehicle-treated 2 weeks post-infusion (EF: 48.6±2.1% vs 38.2±2.6%, p<0.05; IS: 9±2 vs 14±2%, p<0.05). At 2 months, EF still trended higher in CDC-treated animals (42±5 vs 32±10%, p=0.09), and IS still trended lower (14±4 vs 16±7%, p=0.60). Pressure-volume relationships revealed a trend for enhanced contractility in CDC-treated animals (Emax: 3.2±2.2 vs 1.0±1.1 mmHg/mL, p=0.26). The magnitude of the functional benefits was similar to that seen in a prior pig study using autologous CDCs.

Overall, results of the present study demonstrate that allogeneic CDCs are largely equivalent to autologous in terms of efficacy, and elicit no detectable immunological response or safety concern.

Direct comparison of different stem cell types and subpopulations reveals superior paracrine potency and myocardial repair efficacy with cardiosphere-derived cells

OBJECTIVES

The goal of this study was to conduct a direct head-to-head comparison of different stem cell types in vitro for various assays of potency and in vivo for functional myocardial repair in the same mouse model of myocardial infarction.

BACKGROUND

Adult stem cells of diverse origins (e.g., bone marrow, fat, heart) and antigenic identity have been studied for repair of the damaged heart, but the relative utility of the various cell types remains unclear.

METHODS

Human cardiosphere-derived cells (CDCs), bone marrow-derived mesenchymal stem cells, adipose tissue-derived mesenchymal stem cells, and bone marrow mononuclear cells were compared.

RESULTS

CDCs revealed a distinctive phenotype with uniform expression of CD105, partial expression of c-kit and CD90, and negligible expression of hematopoietic markers. In vitro, CDCs showed the greatest myogenic differentiation potency, highest angiogenic potential, and relatively high production of various angiogenic and antiapoptotic-secreted factors. In vivo, injection of CDCs into the infarcted mouse hearts resulted in superior improvement of cardiac function, the highest cell engraftment and myogenic differentiation rates, and the least-abnormal heart morphology 3 weeks after treatment. CDC-treated hearts also exhibited the lowest number of apoptotic cells. The c-kit(+) subpopulation purified from CDCs produced lower levels of paracrine factors and inferior functional benefit when compared with unsorted CDCs. To validate the comparison of cells from various human donors, selected results were confirmed in cells of different types derived from individual rats.

CONCLUSIONS

CDCs exhibited a balanced profile of paracrine factor production and, among various comparator cell types/subpopulations, provided the greatest functional benefit in experimental myocardial infarction.

Bone mass loss in chronic heart failure is associated with secondary hyperparathyroidism and has prognostic significance

AIMS

Chronic heart failure (CHF) is associated with increased risk of osteoporosis. We investigated the relationship between severity of CHF and bone loss, underlying pathophysiological mechanisms, and the prognostic significance of bone mass changes in heart failure.

METHODS AND RESULTS

Total body (TB) and femoral (F) bone mineral density (BMD), and T- and Z-scores in the femur were measured in 60 men with CHF (56 ± 11 years) and 13 age-matched men free from CHF. The composite study endpoint was death, implantation of a left ventricular assist device (LVAD), or inotrope dependency during a median 2-year follow-up. Parathyroid hormone (PTH) and vitamin D were measured in all subjects. TBBMD, FBMD, T-score, and Z-score were significantly lower in men with CHF. Their PTH levels were also significantly increased (111 ± 59 vs. 39 ± 14; P < 0.001). Patients in New York Heart Association classes III-IV compared with those in classes I-II demonstrated significantly lower TBBMD, FBMD, T-score, and Z-score, and higher PTH (136 ± 69 vs. 86 ± 31; P= 0.001). Increased PTH levels were correlated with reduced TBBMD (P = 0.003), FBMD (P = 0.002), and femur T-score (P = 0.001), reduced cardiac index (P = 0.01) and VO(2) peak (P < 0.0001), and increased wedge pressure (P = 0.001). Low TBBMD [hazard ratio (HR) 0.003, 95% confidence interval (CI) 0.00-0.58; P = 0.03] and Z-score (HR 0.56, 95% CI 0.35-0.90; P = 0.017) were associated with adverse outcome.

CONCLUSIONS

Secondary hyperparathyroidism and reduction in bone density occur in CHF patients and are associated with disease severity. Increased bone mass loss in CHF has prognostic significance.

Knowledge Editor and execution engine development for optimal ventricular assist device weaning

In this work, the weaning module of the SensorART specialist decision support system (SDSS) is presented. SensorART focuses on the treatment of patients suffering from end-stage heart failure (HF). The use of a ventricular assist device (VAD) is the main treatment for HF patients. However in certain cases, myocardial function recovers and VADs can be explanted after the patient is weaned. In that framework an efficient module is developed responsible for the selection of the most suitable candidates for VAD weaning. In this study we describe all technical specifications concerning its two main sub-modules of the weaning module, of the Clinical Knowledge Editor and the Knowledge Execution Engine.

Chronotropic incompetence and abnormal heart rate recovery early after left ventricular assist device implantation

BACKGROUND

Chronotropic response to exercise and heart rate recovery immediately after exercise (HRR(1) ) are valid prognostic markers in patients with chronic heart failure (CHF). The aim of this study was to evaluate heart rate profile during and after exercise in CHF patients early after left ventricular assist device (LVAD) implantation.

METHODS

We enrolled seven stable consecutive CHF patients (five males, mean age: 45 ± 16 years) after 1 month of LVAD (HeartMate II; Thoratec Corp, Pleasanton, CA, USA) implantation, seven healthy subjects, and 14 patients with advanced HF (HF control group) who performed an incremental symptom-limited cardiopulmonary exercise testing (CPET). CHF patients performed CPET at 1 and 3 months after LVAD. HRR(1) was defined as the HR difference from peak to 1 minute after exercise and chronotropic response to exercise as the chronotropic reserve ([CR, %]=[peak HR-resting HR/220-age-resting HR]× 100).

RESULTS

LVAD patients 3 months after implantation had a significantly different HR profile during exercise compared to healthy controls, with significantly lower CR (57 ± 31 vs 90 ± 14, %, P < 0.001) and HRR(1) (14 ± 6 vs 28 ± 8, bpm, P < 0.01). HR profile during exercise did not significantly change 1 and 3 months after LVAD implantation. There was no statistical difference compared to HF control group and LVAD group regarding cardiopulmonary parameters.

CONCLUSIONS

LVAD patients present an impaired CR and an abnormal HRR(1) after implantation, indicating significant cardiac autonomic abnormalities. These alterations seem to remain unaltered 3 months after LVAD implantation.

Skeletal muscle microcirculatory abnormalities are associated with exercise intolerance, ventilatory inefficiency, and impaired autonomic control in heart failure

BACKGROUND

Several skeletal muscle abnormalities have been identified in patients with chronic heart failure (CHF), including endothelial dysfunction. We hypothesized that skeletal muscle microcirculation, assessed by near-infrared spectroscopy (NIRS), is impaired in CHF patients and is associated with disease severity.

METHODS

Eighty-three stable patients with mild-moderate CHF (72 males, mean age 54 ± 14 years, body mass index 26.7 ± 3.4 kg/m(2)) and 8 healthy subjects, matched for age, gender and body mass index, underwent NIRS with the vascular occlusion technique and cardiopulmonary exercise testing (CPET) evaluation on the same day. Tissue oxygen saturation (StO(2), %), defined as the percentage of hemoglobin saturation in the microvasculature compartments, was measured in the thenar muscle by NIRS before, during and after 3-minute occlusion of the brachial artery. Measurements included StO(2), oxygen consumption rate (OCR, %/min) and reperfusion rate (RR, %/min). All subjects underwent a symptom-limited CPET on a cycle ergometer. Measurements included VO(2) at peak exercise (VO(2)peak, ml/kg/min) and anaerobic threshold (VO(2)AT, ml/kg/min), VE/VCO(2) slope, chronotropic reserve (CR, %) and heart rate recovery (HRR(1), bpm).

RESULTS

CHF patients had significantly lower StO(2) (75 ± 8.2 vs 80.3 ± 6, p < 0.05), lower OCR (32.3 ± 10.4 vs 37.7 ± 5.5, p < 0.05) and lower RR (10 ± 2.8 vs 15.7 ± 6.3, p < 0.05) compared with healthy controls. CHF patients with RR ≥9.5 had a significantly greater VO(2)peak (p < 0.001), VO(2)AT (p < 0.01), CR (p = 0.01) and HRR(1) (p = 0.01), and lower VE/VCO(2) slope (p = 0.001), compared to those with RR <9.5. In a multivariate analysis, RR was identified as an independent predictor of VO(2)peak, VE/VCO(2) slope and HRR(1).

CONCLUSIONS

Peripheral muscle microcirculation, as assessed by NIRS, is significantly impaired in CHF patients and is associated with disease severity.

Safety and efficacy of allogeneic cell therapy in infarcted rats transplanted with mismatched cardiosphere-derived cells

BACKGROUND

Cardiosphere-derived cells (CDCs) are an attractive cell type for tissue regeneration, and autologous CDCs are being tested clinically. However, autologous therapy necessitates patient-specific tissue harvesting and cell processing, with delays to therapy and possible variations in cell potency. The use of allogeneic CDCs, if safe and effective, would obviate such limitations. We compared syngeneic and allogeneic CDC transplantation in rats from immunologically-mismatched inbred strains.

METHODS AND RESULTS

In vitro, CDCs expressed major histocompatibility complex class I but not class II antigens or B7 costimulatory molecules. In mixed-lymphocyte cocultures, allogeneic CDCs elicited negligible lymphocyte proliferation and inflammatory cytokine secretion. In vivo, syngeneic and allogeneic CDCs survived at similar levels in the infarcted rat heart 1 week after delivery, but few syngeneic (and even fewer allogeneic) CDCs remained at 3 weeks. Allogeneic CDCs induced a transient, mild, local immune reaction in the heart, without histologically evident rejection or systemic immunogenicity. Improvements in cardiac structure and function, sustained for 6 months, were comparable with syngeneic and allogeneic CDCs. Allogeneic CDCs stimulated endogenous regenerative mechanisms (cardiomyocyte cycling, recruitment of c-kit(+) cells, angiogenesis) and increased myocardial vascular endothelial growth factor, insulin-like growth factor-1, and hepatocyte growth factor equally with syngeneic CDCs.

CONCLUSIONS

Allogeneic CDC transplantation without immunosuppression is safe, promotes cardiac regeneration, and improves heart function in a rat myocardial infarction model, mainly through stimulation of endogenous repair mechanisms. The indirect mechanism of action rationalizes the persistence of benefit despite the evanescence of transplanted cell survival. This work motivates the testing of allogeneic human CDCs as a potential off-the-shelf product for cellular cardiomyoplasty.

Myocardial substrate and route of administration determine acute cardiac retention and lung bio-distribution of cardiosphere-derived cells

BACKGROUND

Quantification of acute myocardial retention and lung bio-distribution of cardiosphere-derived cells (CDCs) following transplantation is important to improve engraftment.

METHODS AND RESULTS

We studied acute(1 hour) cardiac/lung retention in 4 groups (n = 25) of rats (normal--NL, acute ischemia-reperfusion--AI-RM, acute permanent ligation-PL, and chronic infarct by ischemia-reperfusion--CI-R) using intra-myocardial delivery, 1 group using intracoronary delivery (acute ischemia-reperfusion, AI-RC, n = 5) and 1 group using intravenous delivery (acute ischemia-reperfusion, AI-RV, n = 5) of CDCs by PET. Cardiac retention was similar in the NL, AI-RM, CI-R, and A-IRC groups (13.6% ± 2.3% vs. 12.0% ± 3.9% vs. 9.9 ± 2.8 vs. 15.4% ± 5.5%; P = NS), but higher in PL animals (22.9% ± 5.2%; P < .05). Low cardiac retention was associated with significantly higher lung activity in NL and AI-RM groups (43.3% ± 5.6% and 39.9% ± 9.3%), compared to PL (28.5% ± 5.9%), CI-R (20.2% ± 9.3%), and A-IRC (19.9% ± 5.6%) animals (P < .05 vs. AI-RM and NL). Lung activity was highest following intravenous CDC delivery (55.1% ± 9.3%, P < .001) and was associated with very low cardiac retention (0.8% ± 1.06%). Two-photon microscopy indicated that CDCs escaped to the lungs via the coronary veins following intra-myocardial injection.

CONCLUSIONS

Acute cardiac retention and lung bio-distribution vary with the myocardial substrate and injection route. Intra-myocardially injected CDCs escape into the lungs via coronary veins, an effect that is more pronounced in perfused myocardium.

Intramyocardial injection of autologous cardiospheres or cardiosphere-derived cells preserves function and minimizes adverse ventricular remodeling in pigs with heart failure post-myocardial infarction

OBJECTIVES

The purpose of this study was to test the safety and efficacy of direct injection of cardiosphere-derived cells (CDCs) and their 3-dimensional precursors, cardiospheres, for cellular cardiomyoplasty in a mini-pig model of heart failure after myocardial infarction.

BACKGROUND

Intracoronary administration of CDCs has been demonstrated to reduce infarct size and improve hemodynamic indexes in the mini-pig model, but intramyocardial injection of CDCs or cardiospheres has not been assessed in large animals.

METHODS

Autologous cardiospheres or CDCs grown from endomyocardial biopsies were injected through thoracotomy 4 weeks after anteroseptal myocardial infarction. Engraftment optimization with luciferase-labeled CDCs guided the choice of cell dose (0.5 million cells/site) and target tissue (20 peri-infarct sites). Pigs were randomly allocated to placebo (n = 11), cardiospheres (n = 8), or CDCs (n = 10). Functional data were acquired before injection and again 8 weeks later, after which organs were harvested for histopathology.

RESULTS

Beyond the immediate perioperative period, all animals survived to protocol completion. Ejection fraction was equivalent at baseline, but at 8 weeks was higher than placebo in both of the cell-treated groups (placebo vs. CDC, p = 0.01; placebo vs. cardiospheres, p = 0.01). Echocardiographic and hemodynamic indexes of efficacy improved disproportionately with cardiospheres; likewise, adverse remodeling was more attenuated with cardiospheres than with CDCs. Provocative electrophysiologic testing showed no differences among groups, and no tumors were found.

CONCLUSIONS

Dosage-optimized direct injection of cardiospheres or CDCs is safe and effective in preserving ventricular function in porcine ischemic cardiomyopathy. Although CDCs and cardiospheres have equivalent effects on left ventricular ejection fraction, cardiospheres are superior in improving hemodynamics and regional function, and in attenuating ventricular remodeling.

The addition of strength training to aerobic interval training: effects on muscle strength and body composition in CHF patients

PURPOSE

The loss of lean muscle mass and muscle strength is a common problem in chronic heart failure (CHF) patients. Endurance training is efficient in improving patient exercise capacity. This study sought to evaluate the additional effects of strength training on muscle strength and body composition in chf patients participating in an interval training program.

METHODS

Twenty consecutive, stable CHF patients participated in a rehabilitation program. Subjects were randomly assigned to aerobic (n = 10) or combined aerobic plus strength training group (n = 10). Aerobic group performed interval training on cycle ergometers. Strength training incorporated exercises for various muscle groups, including quadriceps, hamstrings, biceps brachii, and the deltoids. Both regimes were of the same duration. Body composition was evaluated by whole-body dual energy x-ray absorptiometry and quadriceps strength by the sum of the 2-repetition maximum (2-RM) test for each leg. Peak oxygen uptake (.VO(2peak)) and peak work load (W(peak)) as well as oxygen uptake (.VO(2AT)) and workload at anaerobic threshold (W(AT)) were evaluated by a symptom limited cardiopulmonary exercise testing.

RESULTS

Concerning leg lean mass, no significant within-subjects or between-groups changes were observed (P > .05). Both groups improved in 2-RM test (P < .05), while a significant difference was observed between groups (P < .05). .VO(2peak) and .VO(2AT) and W(peak) and W(AT) were equally improved between training groups (P < .05).

CONCLUSIONS

Combined aerobic interval and strength training induces a greater benefit than interval training alone on muscle strength in CHF patients. Adaptations other than hypertrophy, such as muscle fiber type alterations and/or neuromuscular adjustments, may account for these results.

Isolation and expansion of functionally-competent cardiac progenitor cells directly from heart biopsies

The adult heart contains reservoirs of progenitor cells that express embryonic and stem cell-related antigens. While these antigenically-purified cells are promising candidates for autologous cell therapy, clinical application is hampered by their limited abundance and tedious isolation methods. Methods that involve an intermediate cardiosphere-forming step have proven successful and are being tested clinically, but it is unclear whether the cardiosphere step is necessary. Accordingly, we investigated the molecular profile and functional benefit of cells that spontaneously emigrate from cardiac tissue in primary culture. Adult Wistar-Kyoto rat hearts were minced, digested and cultured as separate anatomical regions. Loosely-adherent cells that surround the plated tissue were harvested weekly for a total of five harvests. Genetic lineage tracing demonstrated that a small proportion of the direct outgrowth from cardiac samples originates from myocardial cells. This outgrowth contains sub-populations of cells expressing embryonic (SSEA-1) and stem cell-related antigens (c-Kit, abcg2) that varied with time in culture but not with the cardiac chamber of origin. This direct outgrowth, and its expanded progeny, underwent marked in vitro angiogenic/cardiogenic differentiation and cytokine secretion (IGF-1, VGEF). In vivo effects included long-term functional benefits as gauged by MRI following cell injection in a rat model of myocardial infarction. Outgrowth cells afforded equivalent functional benefits to cardiosphere-derived cells, which require more processing steps to manufacture. These results provide the basis for a simplified and efficient process to generate autologous cardiac progenitor cells (and mesenchymal supporting cells) to augment clinically-relevant approaches for myocardial repair.

Noninvasive quantification and optimization of acute cell retention by in vivo positron emission tomography after intramyocardial cardiac-derived stem cell delivery

OBJECTIVES

The aim of this study was to quantify acute myocardial retention of cardiac-derived stem cells (CDCs) and evaluate different delivery methods with positron emission tomography (PET).

BACKGROUND

Success of stem cell transplantation for cardiac regeneration is partially limited by low retention/engraftment of the delivered cells. A clinically applicable method for accurate quantification of cell retention would enable optimization of cell delivery.

METHODS

The CDCs were derived from syngeneic, male Wistar Kyoto (WK) rats labeled with [(18)F]-fluoro-deoxy-glucose ((18)FDG) and injected intramyocardially into the ischemic region of female WK rats after permanent left coronary artery ligation. The effects of fibrin glue (FG), bradycardia (adenosine), and cardiac arrest were examined. Imaging with (18)FDG PET was performed for quantification of cell retention. Quantitative polymerase chain reaction (PCR) for the male-specific SRY gene was performed to validate the PET results.

RESULTS

Myocardial retention of cells suspended in phosphate-buffered saline 1 h after delivery was 17.6 +/- 11.5% by PCR and 17.8 +/- 7.3% by PET. When CDCs were injected immediately after induction of cardiac arrest, retention was increased to 75.6 +/- 18.6%. Adenosine slowed the ventricular rate and doubled CDC retention (35.4 +/- 5.3%). A similar increase in CDC retention was observed after epicardial application of FG at the injection site (37.5 +/- 8.2%). The PCR revealed a significant increase in 3-week cell engraftment in the FG animals (22.1 +/- 18.6% and 5.3 +/- 3.1%, for FG and phosphate-buffered saline, respectively).

CONCLUSIONS

In vivo PET permits accurate measurement of CDC retention early after intramyocardial delivery. Sealing injection sites with FG or lowering ventricular rate by adenosine might be clinically translatable methods for improving stem cell engraftment in a beating heart.

Validation of the cardiosphere method to culture cardiac progenitor cells from myocardial tissue

Background

At least four laboratories have shown that endogenous cardiac progenitor cells (CPCs) can be grown directly from adult heart tissue in primary culture, as cardiospheres or their progeny (cardiosphere-derived cells, CDCs). Indeed, CDCs are already being tested in a clinical trial for cardiac regeneration. Nevertheless, the validity of the cardiosphere strategy to generate CPCs has been called into question by reports based on variant methods. In those reports, cardiospheres are argued to be cardiomyogenic only because of retained cardiomyocytes, and stem cell activity has been proposed to reflect hematological contamination. We use a variety of approaches (including genetic lineage tracing) to show that neither artifact is applicable to cardiospheres and CDCs grown using established methods, and we further document the stem cell characteristics (namely, clonogenicity and multilineage potential) of CDCs.

Methodology/Principal Findings

CPCs were expanded from human endomyocardial biopsies (n = 160), adult bi-transgenic MerCreMer-Z/EG mice (n = 6), adult C57BL/6 mice (n = 18), adult GFP⁺ C57BL/6 transgenic mice (n = 3), Yucatan mini pigs (n = 67), adult SCID beige mice (n = 8), and adult Wistar-Kyoto rats (n = 80). Cellular yield was enhanced by collagenase digestion and process standardization; yield was reduced in altered media and in specific animal strains. Heparinization/retrograde organ perfusion did not alter the ability to generate outgrowth from myocardial sample. The initial outgrowth from myocardial samples was enriched for sub-populations of CPCs (c-Kit⁺), endothelial cells (CD31⁺, CD34⁺), and mesenchymal cells (CD90⁺). Lineage tracing using MerCreMer-Z/EG transgenic mice revealed that the presence of cardiomyocytes in the cellular outgrowth is not required for the generation of CPCs. Rat CDCs are shown to be clonogenic, and cloned CDCs exhibit spontaneous multineage potential.

Conclusions/Significance

This study demonstrates that direct culture and expansion of CPCs from myocardial tissue is simple, straightforward, and reproducible when appropriate techniques are used.

Ectopic expression of the sodium-iodide symporter enables imaging of transplanted cardiac stem cells in vivo by single-photon emission computed tomography or positron emission tomography

OBJECTIVES

We examined the sodium-iodide symporter (NIS), which promotes in vivo cellular uptake of technetium 99m ((99m)Tc) or iodine 124 ((124)I), as a reporter gene for cell tracking by single-photon emission computed tomography (SPECT) or positron emission tomography (PET) imaging.

BACKGROUND

Stem cells offer the promise of cardiac repair. Stem cell labeling is a prerequisite to tracking cell fate in vivo.

METHODS

The human NIS complementary deoxyribonucleic acid was transduced into rat cardiac-derived stem cells (rCDCs) using lentiviral vectors. Rats were injected intramyocardially with up to 4 million NIS(+)-rCDCs immediately after left anterior descending coronary artery ligation. Dual isotope SPECT (or PET) imaging was performed, using (99m)Tc (or (124)I) for cell detection and thallium 201 (or ammonia 13) for myocardial delineation. In a subset of animals, high resolution ex vivo SPECT scans of explanted hearts were obtained to confirm that in vivo signals were derived from the cell injection site.

RESULTS

NIS expression in rCDCs did not affect cell viability and proliferation. NIS activity was verified in isolated transduced cells by measuring (99m)Tc uptake. NIS(+) rCDCs were visualized in vivo as regions of (99m)Tc or (124)I uptake within a perfusion deficit in the SPECT and PET images, respectively. Cells could be visualized by SPECT up to 6 days post-injection. Ex vivo SPECT confirmed that in vivo (99m)Tc signals were localized to the cell injection sites.

CONCLUSIONS

Ectopic NIS expression allows noninvasive in vivo stem cell tracking in the myocardium, using either SPECT or PET. The general approach shows significant promise in tracking the fate of transplanted cells participating in cardiac regeneration, given its ability to observe living cells using clinically applicable imaging modalities.

Magnetic resonance imaging overestimates ferumoxide-labeled stem cell survival after transplantation in the heart

BACKGROUND

Stem cell labeling with iron oxide (ferumoxide) particles allows labeled cells to be detected by magnetic resonance imaging (MRI) and is commonly used to track stem cell engraftment. However, the validity of MRI for distinguishing surviving ferumoxide-labeled cells from other sources of MRI signal, for example, macrophages containing ferumoxides released from nonsurviving cells, has not been thoroughly investigated. We sought to determine the relationship between the persistence of iron-dependent MRI signals and cell survival 3 weeks after injection of syngeneic or xenogeneic ferumoxides-labeled stem cells (cardiac-derived stem cells) in rats.

METHODS AND RESULTS

We studied nonimmunoprivileged human and rat cardiac-derived stem cells and human mesenchymal stem cells doubly labeled with ferumoxides and beta-galactosidase and injected intramyocardially into immunocompetent Wistar-Kyoto rats. Animals were imaged at 2 days and 3 weeks after stem cell injection in a clinical 3-T MRI scanner. At 2 days, injection sites of xenogeneic and syngeneic cells (cardiac-derived stem cells and mesenchymal stem cells) were identified by MRI as large intramyocardial signal voids that persisted at 3 weeks (50% to 90% of initial signal). Histology (at 3 weeks) revealed the presence of iron-containing macrophages at the injection site, identified by CD68 staining, but very few or no beta-galactosidase-positive stem cells in the animals transplanted with syngeneic or xenogeneic cells, respectively.

CONCLUSIONS

The persistence of significant iron-dependent MRI signal derived from ferumoxide-containing macrophages despite few or no viable stem cells 3 weeks after transplantation indicates that MRI of ferumoxide-labeled cells does not reliably report long-term stem cell engraftment in the heart.

No effect of stem cell mobilization with GM-CSF on infarct size and left ventricular function in experimental acute myocardial infarction

OBJECTIVES

To evaluate the effect of bone marrow pluripotent stem cell mobilization with granulocyte-monocyte colony stimulating factor (GMCSF) on infarct size and left ventricular function, in the setting of acute myocardial infarction, with a protocol easily applicable in clinical practice.

METHODS

Ten pigs underwent left thoracotomy and left anterior descending coronary artery occlusion for 1 h, followed by reperfusion. After 50 min of arterial occlusion, the animals were randomly divided between treatment with placebo (Group 1) and subcutaneous GM-CSF (Group 2). The thoracotomy was closed and the animals recovered. In Group 2, GM-CSF, 20 microg/kg, was administered daily, 5 days/week, for 3 weeks. Echocardiograms were obtained at 5 and 28 days after acute myocardial infarction. At 30 days, infarct size, expressed as a percentage of the whole left ventricular mass, was measured.

RESULTS

The white blood cell count increased from 13000 +/- 3338/ microl to 28700 +/- 4916/ microl (p = 0.001) in the GM-CSF-treated group. Infarct size was 7.8 +/- 6.1% in Group 1 vs 7.5 +/- 7.7% in Group 2 (ns). Similarly, no significant difference was observed between the 2 study groups in any of the echocardiographic measurements made at 28 days.

CONCLUSIONS

Subcutaneous GMCSF administered during the early post acute myocardial infarction period neither decreased infarct size nor improved left ventricular function. Other protocols for mobilization of stem cells and their concentration in the injured area should be developed to combine efficacy and clinical applicability.

Indium-111 monoclonal antimyosin cardiac scintigraphy in suspected acute myocarditis: evolution and diagnostic impact

BACKGROUND

This study examined the evolution of the heart to lung (H/L) ratio of monoclonal antimyosin antibody (MAA) uptake in patients with suspected acute myocarditis (AM) and its time-dependent diagnostic value in conjunction with echocardiographic findings.

METHODS

The study included 20 patients with a short history (<4 months) of heart failure symptoms and normal coronary arteries. All patients underwent cardiac antimyosin scintigraphy, echocardiography, right-heart catheterization and endomyocardial biopsy. Patients who survived beyond 1 year were reevaluated with a cardiac antimyosin scintigraphy and an echocardiographic study.

RESULTS

Endomyocardial biopsy in 8/20 patients revealed findings compatible with the diagnosis of idiopathic dilated cardiomyopathy (group I) and in the remaining 12/20 was diagnostic of AM (group II). At baseline evaluation of the antimyosin H/L ratio uptake was similar in groups I and II, at 1.95+/-0.19 and 2.16+/-0.51, respectively (P=0.222), while the left ventricular end diastolic diameter (LVEDd) was significantly higher in group I (68+/-12 mm) than in group II (56+/-11 mm, P=0.041). In these patients an initial positive MAA scintigraphy (H/L ratio>1.55) associated with an LVEDd<or=62 mm was diagnostic of AM with a sensitivity of 67%, a specificity of 63% and a positive predictive value of 65%. Upon restudy, the H/L ratio of MAA uptake was significantly decreased in both groups, reaching almost identical levels. No difference was found in the LVEDd between the two groups. The positivity of cardiac antimyosin scintigraphy in conjunction with an LVEDd<or=62 mm had a sensitivity of 45% and a specificity of 88% for the diagnosis of myocarditis.

CONCLUSIONS

In patients with suspected AM a positive antimyosin scintigraphy accompanied by a non-dilated left ventricle is highly suggestive of AM, both at the early phase and 1 year after disease onset.

Heart rate effect on hemodynamics during mechanical assistance by the intra-aortic balloon pump

Heart rate (HR) has been characterized as an important cardiovascular parameter that affects acute hemodynamic performance of intra-aortic balloon counterpulsation (IABC). However, the effect of HR on hemodynamics during mechanical assistance by the IABC has neither been clarified nor quantified. We sought to evaluate the relationship between IABC and HR and also to examine whether there is a range of HR with optimum hemodynamic response to IABC.

METHODS

20 patients (14 males--6 females, mean age 64.4 +/- 11.4 years) with post-infarction cardiogenic shock undergoing IABC treatment were evaluated. Hemodynamics were recorded for each patient once per day during the assistance period; 131 measurements were taken and thus a wide range of heart rates was obtained (64-141 bpm). The following changes in aortic pressures were used to evaluate acute IABC performance on: a) the maximal increase of diastolic aortic pressure induced by IABC and b) the reduction in systolic and end-diastolic aortic pressure.

RESULTS

Non-linear regression analysis and analysis of variance revealed that a significant correlation exists between IABC performance indices and heart rate. At HR<80 bpm, IABC performance tended to be reduced, whereas the increase in HR above 110 bpm resulted in a significant reduction of all IABC performance indices. In contrast, IABC operating at 80-110 bpm resulted in optimum hemodynamic performance. In conclusion, the effect of heart rate on IABC performance is non-linear indicating that IABC may be more effective when operating within 80-110 bpm.