Impact of Musculoskeletal Limitations on Cardiac Rehabilitation Participation.

Background: To help clarify a potential barrier to cardiac rehabilitation (CR) participation we sought to examine the association between musculoskeletal limitations (MSLs) and CR enrollment and participation. Methods: Consecutive CR eligible individuals hospitalized for a cardiac event (myocardial infarction, percutaneous coronary intervention, and/or coronary artery bypass graft) between the months of November 2007 and May 2008, were asked to complete a mailed survey within 2 weeks after hospital discharge, assessing demographic factors, Patient Health Questionnaire (PHQ-9), participation in CR and MSLs through a validated MSLs screening tool. CR enrollment rates were compared between patients with and without MSLs. Results: Three hundred and twenty-one (37%) of patients contacted responded to our survey, including 228 males (71%), with a mean age 68 ± 10.8 years, of whom 98% were Caucasian. Eighty-two percent of responders reported a musculoskeletal disorder at the time of hospital discharge. Arthritis was the most frequent diagnosis (45%). Muscle or joint pain sufficient to limit the ability to do moderate exercise was reported in 52% of the respondents. Problems with balance affected 37%, of whom 45% reported a fall within the previous year. No significant difference in CR enrollment was observed in respondents with and without MSLs [OR = 0.98, 95% CI (0.88-1.09), p = 0.750]. Similar results were found when severity and number of MSLs were taken into account. However, we found that when compared to those without MSLs, the presence of MSLs was associated with lower CR participation (OR = 0.80, 95%, CI: 0.65-0.97, p = 0.0252). Conclusion: Despite a high prevalence of MSLs among CR-eligible patients, we found no association between MSLs and CR enrollment. However, patients with MSLs attended significantly fewer CR sessions as compared to patients without them. CR programs should consider providing additional support and interventions to patients with MSLs in order to optimize their adherence to prescribed CR sessions.

[Ethics of stem cell therapy for heart failure]. / Terapia con células madre e insuficiencia cardiaca: aspectos éticos.

Heart failure is one of the first diseases in which stem cells were used for regenerative medicine. Since 2001, many publications have shown that stem cell therapy has the potential to mitigate heart diseases, but there is no solid scientific evidence to fully support its clinical application at present. The future of regenerative medicine requires validated clinical trials with standardized platforms and transdisciplinary efforts to enable the development of safe and effective regenerative therapies to protect patients and to promote the ethical application of this new and highly promising therapy. Doctors and scientists have a responsibility to discuss with patients the current reality of regenerative therapies. They also have a responsibility to discourage the indiscriminate and commercial use of these therapies, which are sometimes based on false hopes, since their inappropriate use can harm vulnerable patients as well as research efforts. Although regenerative medicine may be the medicine of the future and might bring the hope of cure for chronic diseases, it is not yet ready for its wide clinical application.

Terapia con células madre e insuficiencia cardiaca: aspectos éticos / Ethics of stem cell therapy for heart failure

Heart failure is one of the first diseases in which stem cells were used for regenerative medicine. Since 2001, many publications have shown that stem cell therapy has the potential to mitigate heart diseases, but there is no solid scientific evidence to fully support its clinical application at present. The future of regenerative medicine requires validated clinical trials with standardized platforms and transdisciplinary efforts to enable the development of safe and effective regenerative therapies to protect patients and to promote the ethical application of this new and highly promising therapy. Doctors and scientists have a responsibility to discuss with patients the current reality of regenerative therapies. They also have a responsibility to discourage the indiscriminate and commercial use of these therapies, which are sometimes based on false hopes, since their inappropriate use can harm vulnerable patients as well as research efforts. Although regenerative medicine may be the medicine of the future and might bring the hope of cure for chronic diseases, it is not yet ready for its wide clinical application.

Cardiac Rehabilitation for Women: A Systematic Review of Barriers and Solutions.

Cardiac rehabilitation (CR) services improve various clinical outcomes in patients with cardiovascular disease, but such services are underutilized, particularly in women. The aim of this study was to identify evidence-based barriers and solutions for CR participation in women. A literature search was carried out using PubMed, EMBASE, Cochrane, OVID/Medline, and CINAHL to identify studies that have assessed barriers and/or solutions to CR participation. Titles and abstracts were screened, and then the full-text of articles that met study criteria were reviewed. We identified 24 studies that studied barriers to CR participation in women and 31 studies that assessed the impact of various interventions to improve CR referral, enrollment, and/or completion of CR in women. Patient-level barriers included lower education level, multiple comorbid conditions, non-English native language, lack of social support, and high burden of family responsibilities. We found support for the use of automatic referral and assisted enrollment to improve CR participation. A small number of studies suggest that incentive-based strategies, as well as home-based programs, may contribute to improving CR attendance and completion rates. A systematic approach to CR referral, including automatic CR referral, may help overcome barriers to CR referral in women and should be implemented in clinical practice. However, more studies are needed to help identify the best methods to improve CR attendance and completion of CR rates in women.

Calreticulin secures calcium-dependent nuclear pore competency required for cardiogenesis.

Calreticulin deficiency causes myocardial developmental defects that culminate in an embryonic lethal phenotype. Recent studies have linked loss of this calcium binding chaperone to failure in myofibrillogenesis through an as yet undefined mechanism. The purpose of the present study was to identify cellular processes corrupted by calreticulin deficiency that precipitate dysregulation of cardiac myofibrillogenesis related to acquisition of cardiac phenotype. In an embryonic stem cell knockout model, calreticulin deficit (crt(-/-)) compromised nucleocytoplasmic transport of nuclear localization signal-dependent and independent pathways, disrupting nuclear import of the cardiac transcription factor MEF2C. The expression of nucleoporins and associated nuclear transport proteins in derived crt(-/-) cardiomyocytes revealed an abnormal nuclear pore complex (NPC) configuration. Altered protein content in crt(-/-) cells resulted in remodeled NPC architecture that caused decreased pore diameter and diminished probability of central channel occupancy versus wild type counterparts. Ionophore treatment of impaired calcium handling in crt(-/-) cells corrected nuclear pore microarchitecture and rescued nuclear import resulting in normalized myofibrillogenesis. Thus, calreticulin deficiency alters nuclear pore function and structure, impeding myofibrillogenesis in nascent cardiomyocytes through a calcium dependent mechanism. This essential role of calreticulin in nucleocytoplasmic communication competency ties its regulatory action with proficiency of cardiac myofibrillogenesis essential for proper cardiac development.

Musclin is an activity-stimulated myokine that enhances physical endurance.

Exercise remains the most effective way to promote physical and metabolic wellbeing, but molecular mechanisms underlying exercise tolerance and its plasticity are only partially understood. In this study we identify musclin-a peptide with high homology to natriuretic peptides (NP)-as an exercise-responsive myokine that acts to enhance exercise capacity in mice. We use human primary myoblast culture and in vivo murine models to establish that the activity-related production of musclin is driven by Ca(2+)-dependent activation of Akt1 and the release of musclin-encoding gene (Ostn) transcription from forkhead box O1 transcription factor inhibition. Disruption of Ostn and elimination of musclin secretion in mice results in reduced exercise tolerance that can be rescued by treatment with recombinant musclin. Reduced exercise capacity in mice with disrupted musclin signaling is associated with a trend toward lower levels of plasma atrial NP (ANP) and significantly smaller levels of cyclic guanosine monophosphate (cGMP) and peroxisome proliferator-activated receptor gamma coactivator 1-α in skeletal muscles after exposure to exercise. Furthermore, in agreement with the established musclin ability to interact with NP clearance receptors, but not with NP guanyl cyclase-coupled signaling receptors, we demonstrate that musclin enhances cGMP production in cultured myoblasts only when applied together with ANP. Elimination of the activity-related musclin-dependent boost of ANP/cGMP signaling results in significantly lower maximum aerobic capacity, mitochondrial protein content, respiratory complex protein expression, and succinate dehydrogenase activity in skeletal muscles. Together, these data indicate that musclin enhances physical endurance by promoting mitochondrial biogenesis.

Systems biology surveillance decrypts pathological transcriptome remodeling.

BACKGROUND: Pathological cardiac development is precipitated by dysregulation of calreticulin, an endoplasmic reticulum (ER)-resident calcium binding chaperone and critical contributor to cardiogenesis and embryonic viability. However, pleiotropic phenotype derangements induced by calreticulin deficiency challenge the identification of specific downstream transcriptome elements that direct proper cardiac formation. Here, differential transcriptome navigation was used to diagnose high priority calreticulin domain-specific gene expression changes and decrypt complex cardiac-specific molecular responses elicited by discrete functional regions of calreticulin. METHODS: Wild type (WT), calreticulin-deficient (CALR(-/-)), and calreticulin truncation variant (CALR(-/-)-NP and CALR(-/-)-PC) pluripotent stem cells were used to investigate molecular remodeling underlying a model of cardiopathology. Bioinformatic deconvolution of isolated transcriptomes was performed to identify predominant expression trends, gene ontology prioritizations, and molecular network features characteristic of discrete cell types. RESULTS: Stem cell lines with wild type (WT), calreticulin-deficient (CALR(-/-)) genomes, as well as calreticulin truncation variants exclusively expressing either the chaperoning (CALR(-/-)-NP) or the calcium binding (CALR(-/-)-PC) domain exhibited characteristic molecular signatures determined by unsupervised agglomerative clustering. Kohonen mapping of RNA expression changes identified transcriptome dynamics that segregated into 12 discrete gene expression meta-profiles which were enriched for regulation of Eukaryotic Initiation Factor 2 (EIF2) signaling. Focused examination of domain-specific gene ontology remodeling revealed a general enrichment of Cardiovascular Development in the truncation variants, with unique prioritization of "Cardiovascular Disease" exclusive to the cohort of down regulated genes of the PC truncation variant. Molecular cartography of genes that comprised this cardiopathological category revealed uncharacterized and novel gene relationships, with identification of Pitx2 as a critical hub within the topology of a CALR(-/-) compromised network. CONCLUSIONS: Diagnostic surveillance, through an algorithm that integrates pluripotent stem cell transcriptomes with advanced high throughput assays and computational bioinformatics, revealed collective gene expression network changes that underlie differential phenotype development. Stem cell transcriptomes provide a deep collective molecular index that reflects ad hoc robustness of the pluripotent gene network. Remodeling events such as monogenic lesions provide a background by which high priority candidate disease effectors and regulators can be identified, demonstrated here by a molecular profiling algorithm that decrypts pluripotent wild type versus disrupted genomes.

Regenerative Therapy Prevents Heart Failure Progression in Dyssynchronous Nonischemic Narrow QRS Cardiomyopathy.

BACKGROUND: Cardiac resynchronization therapy using bi-ventricular pacing is proven effective in the management of heart failure (HF) with a wide QRS-complex. In the absence of QRS prolongation, however, device-based resynchronization is reported unsuitable. As an alternative, the present study tests a regenerative cell-based approach in the setting of narrow QRS-complex HF. METHODS AND RESULTS: Progressive cardiac dyssynchrony was provoked in a chronic transgenic model of stress-triggered dilated cardiomyopathy. In contrast to rampant end-stage disease afflicting untreated cohorts, stem cell intervention early in disease, characterized by mechanical dyssynchrony and a narrow QRS-complex, aborted progressive dyssynchronous HF and prevented QRS widening. Stem cell-treated hearts acquired coordinated ventricular contraction and relaxation supporting systolic and diastolic performance. Rescue of contractile dynamics was underpinned by a halted left ventricular dilatation, limited hypertrophy, and reduced fibrosis. Reverse remodeling reflected a restored cardiomyopathic proteome, enforced at systems level through correction of the pathological molecular landscape and nullified adverse cardiac outcomes. Cell therapy of a dyssynchrony-prone cardiomyopathic cohort translated prospectively into improved exercise capacity and prolonged survivorship. CONCLUSIONS: In narrow QRS HF, a regenerative approach demonstrated functional and structural benefit, introducing the prospect of device-autonomous resynchronization therapy for refractory disease.

Cardiopoietic index predicts heart repair fitness of patient-derived stem cells.

BACKGROUND: Stem cell therapy shows promise for regeneration in heart disease, yet interpatient variability challenges implementation into practice. AIM: To establish a biomarker profile, predictive of reparative potential in patient-derived progenitors, human mesenchymal stem cells were isolated from patients undergoing coronary artery bypass grafting. MATERIALS & METHODS: Stem cell delivery postinfarction translated into divergent benefit, distinguishing reparative from nonreparative populations. RESULTS: While the nonreparative subtype was characterized by low expression of cardiac transcription factors, reparative human mesenchymal stem cells demonstrated high expression of cardiac transcription factors. CONCLUSION: This index of factors (cardiopoietic index) was found sensitive and specific in predicting impact of stem cell benefit on left ventricular function. The cardiopoietic index thus offers a tool to screen stem cell fitness for heart repair prior to intervention.

Regenerative principles enrich cardiac rehabilitation practice.

Cardiovascular morbidity imposes a high degree of disability and mortality, with limited therapeutic options available in end-stage disease. Integral to standard of care, cardiac rehabilitation aims on improving quality-of-life and prolonging survival. The recent advent of regenerative technologies paves the way for a transformative era in rehabilitation medicine whereby, beyond controlling risk factors and disease progression, the prospect of curative solutions is increasingly tangible. To date, the spectrum of clinical experience in cardiac regenerative medicine relies on stem cell-based therapies delivered to the diseased myocardium either acutely/subacutely, after a coronary event, or in the setting of chronic heart failure. Application of autologous/allogeneic stem cell platforms has established safety and feasibility, with encouraging signals of efficacy. Newer protocols aim to purify cell populations in an attempt to eliminate nonregenerative and enrich for regenerative cell types before use. Most advanced technologies have been developed to isolate resident cell populations directly from the heart or, alternatively, condition cells from noncardiac sources to attain a disease-targeted lineage-specified phenotype for optimized outcome. Because a multiplicity of cell-based technologies has undergone phase I/II evaluation, pivotal trials are currently underway in larger patient populations. Translation of regenerative principles into clinical practice will increasingly involve rehabilitation providers across the continuum of patient care. Regenerative rehabilitation is thus an emerging multidisciplinary field, full of opportunities and ready to be explored.

Regenerative rehabilitation: a new future?

Modern rehabilitation medicine is propelled by newfound knowledge aimed at offering solutions for an increasingly aging population afflicted by chronic debilitating conditions. Considered a core component of future health care, the rollout of regenerative medicine underscores a paradigm shift in patient management targeted at restoring physiologic function and restituting normative impact. Nascent regenerative technologies offer unprecedented prospects in achieving repair of degenerated, diseased, or damaged tissues. In this context, principles of regenerative science are increasingly integrated in rehabilitation practices as illustrated in the present Supplement. Encompassing a growing multidisciplinary domain, the emergent era of "regenerative rehabilitation" brings radical innovations at the forefront of healthcare blueprints.

iPS cell-derived cardiogenicity is hindered by sustained integration of reprogramming transgenes.

BACKGROUND: Nuclear reprogramming inculcates pluripotent capacity by which de novo tissue differentiation is enabled. Yet, introduction of ectopic reprogramming factors may desynchronize natural developmental schedules. This study aims to evaluate the effect of imposed transgene load on the cardiogenic competency of induced pluripotent stem (iPS) cells. METHODS AND RESULTS: Targeted inclusion and exclusion of reprogramming transgenes (c-MYC, KLF4, OCT4, and SOX2) was achieved using a drug-inducible and removable cassette according to the piggyBac transposon/transposase system. Pulsed transgene overexpression, before iPS cell differentiation, hindered cardiogenic outcomes. Delayed in counterparts with maintained integrated transgenes, transgene removal enabled proficient differentiation of iPS cells into functional cardiac tissue. Transgene-free iPS cells generated reproducible beating activity with robust expression of cardiac α-actinin, connexin 43, myosin light chain 2a, α/ß-myosin heavy chain, and troponin I. Although operational excitation-contraction coupling was demonstrable in the presence or absence of transgenes, factor-free derivatives exhibited an expedited maturing phenotype with canonical responsiveness to adrenergic stimulation. CONCLUSIONS: A disproportionate stemness load, caused by integrated transgenes, affects the cardiogenic competency of iPS cells. Offload of transgenes in engineered iPS cells ensures integrity of cardiac developmental programs, underscoring the value of nonintegrative nuclear reprogramming for derivation of competent cardiogenic regenerative biologics.

Stem cell therapy for intervertebral disk regeneration.

Intervertebral disk degeneration has been considered an irreversible process characterized by a decrease in cell viability, attenuation of proteoglycan and type II collagen synthesis, and dehydration of nucleus pulposus. Stem cell therapy specifically addresses the degenerative process and offers a potentially effective treatment modality. Current preclinical studies show that mesenchymal stem cells have the capacity to repair degenerative disks by differentiation toward chondrocyte-like cells, which produce proteoglycans and type II collagen. There has been evidence that mesenchymal stem cell transplantation into the intervertebral disk increases the intradiskal magnetic resonance imaging T2 signal intensity, increases the disk height, and decreases the degenerative grade in animal models. Appropriate selection of cell carriers/matrix is important because it may prevent cell leakage into the spinal canal and provide an environment that facilitates cell proliferation and differentiation. Although human cell therapy trials for degenerative disk disease are on the horizon, potential issues might arise. The authors hereby review the current state of regenerative cell therapy in degenerative disk disease, with emphasis in cell source, techniques for cellular expansion, induction, transplantation, potential benefit, and risks of the use of this novel medical armamentarium in the treatment of degenerative disk disease.

Inpatient rehabilitation outcomes for patients receiving left ventricular assist device.

OBJECTIVE: The aim of this study was to evaluate outcomes of patients participating in inpatient rehabilitation program after left ventricular assist device (LVAD) implantation. DESIGN: Medical records of 94 patients who received LVADs between January 1, 2008, and June 30, 2010, at the Mayo Clinic in Rochester, MN, were retrospectively reviewed for demographic data, and inpatient rehabilitation functional outcomes were measured by the Functional Independence Measure scale. RESULTS: After successful implantation of LVAD, the patients were either discharged directly home from acute care (44%) or admitted to inpatient rehabilitation (56%). The patients admitted to inpatient rehabilitation were older than those discharged home. They were also more medically complex and more likely to have the LVAD placed as destination therapy. At discharge, significant improvement occurred in 17 of the 18 activities evaluated by the Functional Independence Measure scale. The mean total Functional Independence Measure scale score at admission was 77.1 compared with a score of 95.2 at discharge (P < 0.0001). CONCLUSIONS: Approximately half of the patients who received LVAD therapy were admitted in the inpatient rehabilitation. After the implantation of LVAD and inpatient rehabilitation, significant functional improvements were observed. Further studies addressing the role of inpatient rehabilitation for LVAD patients are warranted.

Transcriptome from circulating cells suggests dysregulated pathways associated with long-term recurrent events following first-time myocardial infarction.

BACKGROUND: Whole-genome gene expression analysis has been successfully utilized to diagnose, prognosticate, and identify potential therapeutic targets for high-risk cardiovascular diseases. However, the feasibility of this approach to identify outcome-related genes and dysregulated pathways following first-time myocardial infarction (AMI) remains unknown and may offer a novel strategy to detect affected expressome networks that predict long-term outcome. METHODS AND RESULTS: Whole-genome expression microarray on blood samples from normal cardiac function controls (n=21) and first-time AMI patients (n=31) within 48-hours post-MI revealed expected differential gene expression profiles enriched for inflammation and immune-response pathways. To determine molecular signatures at the time of AMI associated with long-term outcomes, transcriptional profiles from sub-groups of AMI patients with (n=5) or without (n=22) any recurrent events over an 18-month follow-up were compared. This analysis identified 559 differentially-expressed genes. Bioinformatic analysis of this differential gene-set for associated pathways revealed 1) increasing disease severity in AMI patients is associated with a decreased expression of genes involved in the developmental epithelial-to-mesenchymal transition pathway, and 2) modulation of cholesterol transport genes that include ABCA1, CETP, APOA1, and LDLR is associated with clinical outcome. CONCLUSION: Differentially regulated genes and modulated pathways were identified that were associated with recurrent cardiovascular outcomes in first-time AMI patients. This cell-based approach for risk stratification in AMI could represent a novel, non-invasive platform to anticipate modifiable pathways and therapeutic targets to optimize long-term outcome for AMI patients and warrants further study to determine the role of metabolic remodeling and regenerative processes required for optimal outcomes.

Is exercise training safe and beneficial in patients receiving left ventricular assist device therapy?

Because a limited number of patients receive heart transplantation, alternative therapies, such as left ventricular assist device (LVAD) therapy, have emerged. Published studies have shown that LVAD implantation, by itself, improves exercise tolerance to the point where it is comparable to those with mild heart failure. The improvement in exercise capacity is maximally achieved 12 weeks after LVAD therapy and can continue even after explantation of the device. This effect varies, depending on the type of LVAD and exercise training. The available data in the literature on safety and benefits of exercise training in patients after LVAD implantation are limited, but the data that are available suggest that training trends to be safe and have an impact on exercise capacity in LVAD patients. Although no studies were identified on the role of cardiac rehabilitation programs in the management of LVAD patients, it appears that cardiac rehabilitation programs offer an ideal setting for the provision of supervised exercise training in this patient group.

Cardiac rehabilitation services in low- and middle-income countries: a scoping review.

BACKGROUND: Despite the decreasing rate of cardiovascular disease-related mortality in developed nations, low- and middle-income countries (LMICs) are experiencing an increase. Cardiac rehabilitation (CR) successfully addresses this burden; however, the availability and nature of CR service delivery in LMICs are not well known. OBJECTIVE: This scoping review examined the (1) presence and accessibility of CR services, (2) structure of CR services, and (3) effects of CR on patient outcomes in LMICs. METHODS: Search criteria consisted of (1) nations considered to be low- or middle-income according to World Bank criteria, (2) CR, defined as programs including exercise and education, and (3) adults with cardiovascular diseases. Literature was identified through searching (a) the MEDLINE and EMBASE electronic databases, (b) proceedings from international cardiac conferences, (c) the grey literature and (d) through consulting experts in the field. RESULTS: Thirty peer-reviewed publications were identified. Grey literature, including Web sites for individual CR programs, revealed that CR is available in 32 (22.1%) LMICs. The most comprehensive data on accessibility stem from Latin America and the Caribbean, where 56% of institutions with cardiac catheterization facilities offered CR. Literature showed that some programs offered exercise, dietary advice, education, and psychological support, to assist patients to resume work and other activities of daily living. Fifteen peer-reviewed studies reported on CR outcomes, most of which were positive. CONCLUSION: Although patients similarly benefit from CR, few programs are available in LMICs. Policies need to be implemented to increase provision of tailored CR models at the global and national level, with evaluation.

Mechanical dyssynchrony precedes QRS widening in ATP-sensitive K⁺ channel-deficient dilated cardiomyopathy.

BACKGROUND: Contractile discordance exacerbates cardiac dysfunction, aggravating heart failure outcome. Dissecting the genesis of mechanical dyssynchrony would enable an early diagnosis before advanced disease. METHODS AND RESULTS: High-resolution speckle-tracking echocardiography was applied in a knockout murine surrogate of adult-onset human cardiomyopathy caused by mutations in cardioprotective ATP-sensitive K(+) (K(ATP)) channels. Preceding the established criteria of cardiac dyssynchrony, multiparametric speckle-based strain resolved nascent erosion of dysfunctional regions within cardiomyopathic ventricles of the K(ATP) channel-null mutant exposed to hemodynamic stress. Not observed in wild-type counterparts, intraventricular disparity in wall motion, validated by the degree, direction, and delay of myocardial speckle patterns, unmasked the disease substrate from asymptomatic to overt heart failure. Mechanical dyssynchrony preceded widening of the QRS complex and exercise intolerance and progressed into global myocardial discoordination and decompensated cardiac pump function, precipitating a low output syndrome. CONCLUSIONS: The present study, with the use of high-resolution imaging, prospectively resolved the origin and extent of intraventricular motion disparity in a K(ATP) channel-knockout model of dilated cardiomyopathy. Mechanical dyssynchrony established as an early marker of cardiomyopathic disease offers novel insight into the pathodynamics of dyssynchronous heart failure.

CXCR4+ and FLK-1+ identify circulating cells associated with improved cardiac function in patients following myocardial infarction.

The biomarkers CXCR4/FLK-1 select cardiac progenitors from a stem cell pool in experimental models. However, the translational value of these cells in human ischemic heart disease is unknown. Here, flow-cytometry identified CD45(-)/CXCR4(+)/FLK-1(+) cells in 30 individuals without ischemic heart disease and 33 first-time acute myocardial infarction (AMI) patients. AMI patients had higher CD45(-)/CXCR4(+)/FLK-1(+) cell-load at 48-h and 3- and 6-months post-AMI (p = 0.003,0.04,0.04, respectively) than controls. Cardiovascular risk factors and left ventricular (LV) ejection fraction were not associated with cell-load. 2D-speckle-tracking strain echocardiography assessment of LV systolic function showed improvement in longitudinal strain and dyssynchrony during follow-up associated with longitudinal increases in and higher 48-h post-AMI CD45(-)/CXCR4(+)/FLK-1(+) cell-load (r = -0.525, p = 0.025; r = -0.457, p = 0.029, respectively). In conclusion, CD45(-)/CXCR4(+)/FLK-1(+) cells are present in adult human circulation, increased in AMI and associated with improved LV systolic function. Thus, CD45(-)/CXCR4(+)/FLK-1(+) cells may provide a diagnostic tool to follow cardiac regenerative capacity and potentially serve as a prognostic marker in AMI.