Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

The temporal burden of preparing catheters for re-use in adults with spinal cord injury: a cross-sectional study

STUDY DESIGN

Cross-sectional OBJECTIVES: Neurogenic lower urinary tract dysfunction is common among people with spinal cord injury (SCI). Although single-use clean intermittent catheterization is recommended to facilitate routine bladder emptying, catheter re-use is common. Barriers associated with the preparation (i.e., cleaning) of catheters for re-use are unknown. This study examined barriers to catheter re-use in adult individuals with SCI by assessing (1) the time needed to clean a catheter, and (2) the perceived difficulty of the catheter cleaning routine.

SETTING

Laboratory METHODS: Twenty individuals with chronic SCI ( ≥ 1 year since injury; Group 1 = 10 with tetraplegia; Group 2 = 10 with paraplegia) completed the study. Using a standardized cleaning procedure (i.e., Milton method), catheter cleaning was timed for each participant. Perceived difficulty was assessed using a 5-point Likert scale. Functional impairment was assessed with the Upper Extremity Motor Score (UEMS).

RESULTS

Significant between-group differences were observed for total cleaning time (Group 1 = 1584.1 ± 179.8 s; Group 2 = 1321.0 ± 93.8 s, p = 0.004) and perceived difficulty [Group 1 = 2.6 (2, 3); Group 2 = 2 (1.7, 2.3), p = 0.028]. Total cleaning time was significantly correlated with UEMS (ρ = -0.709, p ≤ 0.001) and perceived difficulty (ρ = 0.468, p = 0.037). UEMS emerged as an independent predictor of total cleaning time (R² = 0.745, β = -0.833, p ≤ 0.001).

CONCLUSIONS

Preparing catheters for re-use is time-intensive and difficult for people with higher SCI level, severity and more pronounced upper limb motor impairment, which was independently associated with total cleaning time. Performing this routine on a consistent basis would require a substantial time commitment and would have a profoundly negative impact on overall quality of life.

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion.

A Rare Case of COVID-19 Induced Multisystem Inflammatory Syndrome in Adult (MIS-A) Requiring Venoarterial Extracorporeal Membrane Oxygenation (VA-ECMO)

Introduction

MIS-A is a rare COVID-19 induced condition defined by fever, new-onset severe cardiac illness, rash, encephalopathy, and elevated inflammatory markers in the setting of positive serum COVID-19 antibodies. This inflammatory cascade can cause significant biventricular dysfunction and subsequent cardiogenic shock. Patients with MIS-A can require temporary cardiac support including VA-ECMO. We present a case of a patient requiring VA-ECMO secondary to MIS-A induced heart failure and cardiogenic shock, with eventual myocardial recovery.

Case Report

30-year-old male with type two diabetes was admitted with acute hypoxic respiratory failure, multiorgan failure, acute systolic biventricular heart failure, and COVID-19 infection four weeks prior. He was intubated and placed on vasopressors, antibiotics, and steroids for concerns for combined cardiogenic and septic shock. TTE noted global hypokinesis and 10-15% EF. EKG was sinus rhythm. He had mildly elevated troponins. Inflammatory markers including D-dimer, fibrinogen, and IL-6 were highly elevated. Despite antibiotics and supportive measures, the patient developed worsening hypoxia and hypotension. IVIG was also initiated, with deferral of plasmapheresis. At this time, MIS-A was suspected. The patient was approved for VA-ECMO as a means for bridging to cardiac recovery. He required VA-ECMO for four days, with ability to decannulate, extubate, and wean off vasopressors. COVID-19 antibody testing was positive. Infectious workup was negative, with the patient transitioned off antibiotics and steroid regimen after completing treatment course. Inflammatory markers improved. Repeat TTE noted 44% EF with improved biventricular function. Cardiac MRI one day later, noted 61% EF without evidence of scar, myocarditis, or perimyocarditis. He was discharged home after a total of 8 days of treatment with follow-ups scheduled.

Summary

This case highlights a severe presentation of MIS-A and showcases the benefit of VA-ECMO as a bridge to myocardial recovery. VA-ECMO has been shown to improve in-hospital survival and serve as a mechanism for cardiac recovery in acutely ill patients. Long-term cardiac effects and recovery rates post COVID-19 induced MIS-A remain unknown.

Relationship between bone strength index of the hemiparetic tibial diaphysis and muscle strength in people with chronic stroke: influence of muscle contraction type and speed

This study was conducted to examine the association between the tibial bone strength index and leg muscle strength of different contraction types and speeds among people with chronic stroke. We found that concentric muscle power at moderate speed was more associated with tibial bone strength index than other types.

INTRODUCTION

To compare the influence of muscle strength of different contraction types and speeds on the bone strength index of tibial diaphysis in people with chronic stroke.

METHODS

Eighty individuals with chronic stroke (age: 62.6 ± 8.0 years; men/women: 46/34; post-stroke duration: 9.0 ± 5.4 years) underwent scanning of the tibia at the 66% site on both sides using peripheral quantitative computed tomography. Each participant was also evaluated for isometric and dynamic (at 60°/s and 120°/s) strength of knee flexors/extensors and ankle dorsiflexors/plantarflexors using an isokinetic dynamometer. For a given contraction type and speed, the strength values of the four muscle groups were summed to yield a composite score. Multiple regression analysis was used to identify the association of the percent side-to-side difference (%SSD) in tibial polar-stress-strain index (p-SSI) with %SSD in muscle strength of different contraction types and speeds.

RESULTS

The p-SSI and all muscle strength parameters on the paretic side had lower values than the non-paretic side (p ≤ 0.001). The %SSD in concentric muscle power at angular speed of 60°/s (R² = 0.317, p = 0.006) and 120°/s (R² = 0.298, p = 0.020) remained independently associated with that in p-SSI, after controlling for age, sex, body mass index, post-stroke duration, motor impairment, spasticity, and physical activity level. The effect of isometric strength and eccentric muscle power was not significant in multivariate analysis.

CONCLUSIONS

Concentric muscle power was more predictive of %SSD in p-SSI at the tibial diaphysis than other contraction types and may be an important target for intervention to promote bone health in people with chronic stroke.

High-Brightness Continuous-Wave Electron Beams from Superconducting Radio-Frequency Photoemission Gun

Continuous-wave photoinjectors operating at high accelerating gradients promise to revolutionize many areas of science and applications. They can establish the basis for a new generation of monochromatic x-ray free electron lasers, high-brightness hadron beams, or a new generation of microchip production. In this Letter we report on the record-performing superconducting rf electron gun with CsK_{2}Sb photocathode. The gun is generating high charge electron bunches (up to 10  nC/bunch) and low transverse emittances, while operating for months with a single photocathode. This achievement opens a new era in generating high-power beams with a very high average brightness.

Experimental Demonstration of Hadron Beam Cooling Using Radio-Frequency Accelerated Electron Bunches

Cooling of beams of gold ions using electron bunches accelerated with radio-frequency systems was recently experimentally demonstrated in the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. Such an approach is new and opens the possibility of using this technique at higher energies than possible with electrostatic acceleration of electron beams. The challenges of this approach include generation of electron beams suitable for cooling, delivery of electron bunches of the required quality to the cooling sections without degradation of beam angular divergence and energy spread, achieving the required small angles between electron and ion trajectories in the cooling sections, precise velocity matching between the two beams, high-current operation of the electron accelerator, as well as several physics effects related to bunched-beam cooling. Here we report on the first demonstration of cooling hadron beams using this new approach.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Winter irruptive Snowy Owls (Bubo scandiacus) in North America are not starving

Winter irruptions, defined as irregular massive movement of individuals over large distances, have been linked to food supply. Two hypotheses have been put forward: the “lack-of-food” suggests that a shortage of food forces individuals to leave their regular winter range and the “breeding output” suggests that unusually large food supplies during the preceding breeding season allows production of a large number of offspring dispersing in winter. According to the breeding output hypothesis, irruptive Snowy Owls (Bubo scandiacus (Linnaeus, 1758)) in eastern North America should not exhibit a lower body condition than individuals in regular wintering regions and individuals on the breeding grounds. Additionally, body condition of irruptive individuals should be unrelated to irruption intensity. Although body condition of juveniles was generally lower than that of adults and improved during the winter, we measured a fair body condition in both juvenile and adult irruptive Snowy Owls across North America. The results showed that Snowy Owls are not in a starving state during winter and that body condition of all age classes was not related to winter irruption intensity. Those results support the breeding output hypothesis suggesting that winter irruptions seem to be primarily the result of a large number of offspring produced when food availability on the breeding grounds is high.

Fast readout algorithm for cylindrical beam position monitors providing good accuracy for particle bunches with large offsets

A simple, analytically correct algorithm is developed for calculating "pencil" relativistic beam coordinates using the signals from an ideal cylindrical particle beam position monitor (BPM) with four pickup electrodes (PUEs) of infinitesimal widths. The algorithm is then applied to simulations of realistic BPMs with finite width PUEs. Surprisingly small deviations are found. Simple empirically determined correction terms reduce the deviations even further. The algorithm is then tested with simulations for non-relativistic beams. As an example of the data acquisition speed advantage, a Field Programmable Gate Array-based BPM readout implementation of the new algorithm has been developed and characterized. Finally, the algorithm is tested with BPM data from the Cornell Preinjector.

Analysis of extensometer, photogrammetry and laser scanning monitoring techniques for measuring floor heave in an underground limestone mine

An underground limestone mine in eastern Ohio was experiencing significant floor heave and roof falls, attributed to high horizontal stresses. Areas of the mine showing floor heave were monitored with roof-to-floor extensometers and photogrammetry surveys to determine the rate and magnitude of heave. Extensometer data were recorded hourly at four locations across adjacent entries while photogrammetry surveys of the floor were performed at the same locations every two to five weeks. A final survey was performed using an I-Site 8200 laser scanner. Following instrumentation, floor heave up to 10.1 cm (4 in.) was measured by the extensometers, photogrammetric reconstructions and laser scanner over a six-month period. The extensometers were biased by the location where they were placed, failing to consistently capture the location and extent of floor heave and cracking. The photogrammetry surveys were not precise enough to capture small magnitude movements. Mining in the area was halted and within several months the floor movement and incidence of roof falls were significantly lessened.

Geographical differences in survival of dogs with non-Hodgkin lymphoma treated with a CHOP based chemotherapy protocol

BACKGROUND

In humans geographical differences in the incidence and presentation of various cancers have been reported. However, much of this information has not been collected in veterinary oncology.

AIM

The purpose of this study was to determine if a geographic difference in progression free survival exists for dogs with lymphoma treated within the US.

MATERIALS AND METHODS

Medical records of 775 cases of canine lymphoma from 3 US regions (west, south and north), treated with CHOP chemotherapy, were retrospectively evaluated. Cases were collected from referral institutions and were required to have received at least one doxorubicin treatment and have follow up information regarding time to progression.

RESULTS

Significant differences in sex (p = 0.05), weight (p = 0.049), stage (p < 0.001), immunophenotype (p = <0.001), and number of doxorubicin doses (p = 0.001) were seen between regions. Upon univariate analysis, progression free survival (PFS) differed by region (p = 0.006), stage (p = 0.009), sub-stage (p = 0.0005), and immunophenotype (p = 0.001). A multivariable Cox regression model showed that dogs in the western region had a significantly shorter PFS when compared to the south and east.

CONCLUSION

PFS was significantly affected by stage, sub-stage and phenotype.

Incidence and lifetime costs of injuries in the United States

BACKGROUND

Standardized methodologies for assessing economic burden of injury at the national or international level do not exist.

OBJECTIVE

To measure national incidence, medical costs, and productivity losses of medically treated injuries using the most recent data available in the United States, as a case study for similarly developed countries undertaking economic burden analyses.

METHOD

The authors combined several data sets to estimate the incidence of fatal and non-fatal injuries in 2000. They computed unit medical and productivity costs and multiplied these costs by corresponding incidence estimates to yield total lifetime costs of injuries occurring in 2000.

MAIN OUTCOME MEASURES

Incidence, medical costs, productivity losses, and total costs for injuries stratified by age group, sex, and mechanism.

RESULTS

More than 50 million Americans experienced a medically treated injury in 2000, resulting in lifetime costs of $406 billion; $80 billion for medical treatment and $326 billion for lost productivity. Males had a 20% higher rate of injury than females. Injuries resulting from falls or being struck by/against an object accounted for more than 44% of injuries. The rate of medically treated injuries declined by 15% from 1985 to 2000 in the US. For those aged 0-44, the incidence rate of injuries declined by more than 20%; while persons aged 75 and older experienced a 20% increase.

CONCLUSIONS

These national burden estimates provide unequivocal evidence of the large health and financial burden of injuries. This study can serve as a template for other countries or be used in intercountry comparisons.

Enhanced Recovery After Surgery (ERAS) for gastrointestinal surgery, part 2: consensus statement for anaesthesia practice

Background

The present interdisciplinary consensus review proposes clinical considerations and recommendations for anaesthetic practice in patients undergoing gastrointestinal surgery with an Enhanced Recovery after Surgery (ERAS) programme.

Methods

Studies were selected with particular attention being paid to meta‐analyses, randomized controlled trials and large prospective cohort studies. For each item of the perioperative treatment pathway, available English‐language literature was examined and reviewed. The group reached a consensus recommendation after critical appraisal of the literature.

Results

This consensus statement demonstrates that anaesthesiologists control several preoperative, intraoperative and postoperative ERAS elements. Further research is needed to verify the strength of these recommendations.

Conclusions

Based on the evidence available for each element of perioperative care pathways, the Enhanced Recovery After Surgery (ERAS ^®) Society presents a comprehensive consensus review, clinical considerations and recommendations for anaesthesia care in patients undergoing gastrointestinal surgery within an ERAS programme. This unified protocol facilitates involvement of anaesthesiologists in the implementation of the ERAS programmes and allows for comparison between centres and it eventually might facilitate the design of multi‐institutional prospective and adequately powered randomized trials.

Donation After Circulatory Determination of Death Lung Transplantation for Pulmonary Arterial Hypertension: Passing the Toughest Test

Lung transplantation (LTx) is a therapeutic option for severe pulmonary arterial hypertension (PAH) patients failing optimal medical therapy. The use of donation after circulatory determination of death (DCDD) donor lungs for PAH LTx has rarely been reported, primarily reflecting concerns that DCDD lungs represent extended criteria donors, at risk of morbidity and mortality. A retrospective study of all Alfred Hospital DCDD and DNDD (donation after neurologic determination of death) PAH LTx was undertaken. Protocolized fluid/inotrope/ventilator and extracorporeal membrane oxygenation (ECMO) strategies were utilized. Since our first DCDD LTx in 2006, 512 LTx have been performed. Of 31 PAH recipients, 11 received DCDD lungs (11% of DCDD LTx) and 20 received DNDD lungs (5% of DNDD LTx) (p = 0.04). Only one PAH patient died on the LTx waiting list. Peri-LTx ECMO was utilized in 3/11 (27%) DCDD and 6/20 (30%) DNDD PAH LTx (p = 0.68). Primary graft dysfunction, intensive care, and overall stay were the same in both groups. Survival at 1 and 8 years was 100% and 80% for DCDD versus 100% and 70% for DNDD LTx (p = 0.88), respectively. In conclusion, excellent results can be achieved for PAH LTx. DCDD donor lungs are not extended lungs per se having passed the toughest test.

Photoemission Circular Dichroism and Spin Polarization of the Topological Surface States in Ultrathin Bi2Te3 Films

Circular dichroism (CD) observed by photoemission, being sensitive to the orbital and spin angular momenta of the electronic states, is a powerful probe of the nontrivial surface states of topological insulators, but the experimental results thus far have eluded a comprehensive description. We report a study of Bi2Te3 films with thicknesses ranging from one quintuple layer (two-dimensional limit) to 12 layers (bulk limit) over a wide range of incident photon energy. The data show complex variations in magnitude and sign reversals, which are nevertheless well described by a theoretical calculation including all three photoemission mechanisms: dipole transition, surface photoemission, and spin-orbit coupling. The results establish the nontrivial connection between the spin-orbit texture and CD.

Preserving knee function following osteoarthritis diagnosis: a sustainability theory and social ecology clinical commentary

To sustain natural systems, there must be an ongoing balance between environmental, social, and economic considerations. A key element of sustainability theory is to identify the most vulnerable surroundings. The most vulnerable knee tissue is the articular cartilage as it is the last line of osteoarthritis (OA) defense. This tissue has a poor capacity for healing. Based on sustainability theory and social ecology concepts we propose that several key factors contribute to knee function preservation. Factors include health history, genetic predisposition, personal behaviors, and socio-environmental factors in addition to local-regional-global physiological system function. Addressing only some of these factors or any one factor in isolation may lead to less than optimal treatment effectiveness. The purpose of this commentary is to introduce a medical, surgical and rehabilitation management approach for patients with knee OA that considers more than physical function improvement. This approach also considers social, emotional, and environmental factors to better ensure patient satisfaction, fulfilled expectations and successful outcomes. A clinical care pathway is presented for a 57-year-old patient with medial compartment knee OA who is contemplating early arthroplasty versus a knee function preservation treatment approach. Early arthroplasty refers to high revision likelihood based on a minimum 15 year prosthesis life-expectancy.

The association of flushing bother, impact, treatment satisfaction and discontinuation of niacin therapy

BACKGROUND

Niacin has lipid-modifying efficacy and cardiovascular benefit, but is underutilised because of niacin-induced flushing (NIF). This real-world, prospective, observational study characterised the severity and impact of NIF symptoms among participants who were newly prescribed extended-release (ER) niacin.

METHODS

Participants were surveyed daily during week 1 of therapy, at weeks 5, 9, 13, and at months 7, 10 and 13. Surveys included the Flushing Symptom Questionnaire (FSQ), which includes the Global Flushing Severity Score (GFSS) question, the Flushing Impact Questionnaire (FIQ) and the Treatment Satisfaction Questionnaire for Medication (TSQM).

RESULTS

Overall, 306 participants were enrolled. During week 1, 30.0% of participants reported a maximum GFSS ≥ 4 (moderate or greater). Mean FIQ domain scores increased with increasing flushing severity, primarily driven by the Irritation/Frustration domain. By week 13, only 2.5% of participants had attained a 2 g ER niacin dose. By month 13, 43.5% (n = 133) had discontinued ER niacin. At discontinuation, only 3.1% of participants had attained the 2 g dose. Over half of the participants who discontinued experienced flushing symptoms: 82% reported moderate to extreme flushing (GFSS ≥ 4), and 68% reported severe to extreme flushing (GFSS ≥ 7). Participants who discontinued and had flushing side effects reported high degrees of impact in the FIQ Irritation/Frustration domain, and high dissatisfaction as a result of side effects, as measured by the TSQM.

CONCLUSION

In a real-world setting, NIF side effects were bothersome and had an impact on the continuation of therapy.

Eddy viscosity in dense granular flows

We present a seminal set of experiments on dense granular flows in the stadium shear geometry. The advantage of this geometry is that it produces steady shear flow over large deformations, in which the shear stress is constant. The striking result is that the velocity profiles exhibit an S shape, and are not linear as local constitutive laws would predict. We propose a model that suggests this is a result of wall perturbations which span through the system due to the nonlocal behavior of the material. The model is analogous to that of eddy viscosity in turbulent boundary layers, in which the distance to the wall is introduced to predict velocity profiles. Our findings appear pivotal in a number of experimental and practical situations involving dense granular flows next to a boundary. They could further be adapted to other similar materials such as dense suspensions, foams, or emulsions.

Short communication: Streptococcus species isolated from mastitis milk samples in Germany and their resistance to antimicrobial agents

Mastitis is one of the most frequent infectious diseases in dairy cattle and is a reason for antimicrobial drug usage in dairy cows. The bacteria involved in bovine mastitis are mainly Streptococcus spp., Staphylococcus spp., and coliforms. The aim of this study was to determine antimicrobial resistance among Streptococcus spp. isolated from bovine mastitis milk. Antimicrobial resistance in Strep. uberis (n=227), Strep. dysgalactiae (n=49), and Strep. agalactiae (n=3) was determined for 9 antimicrobial agents using the broth microdilution method in accordance with Clinical and Laboratory Standards Institute recommendations. Of all Streptococcus spp., 13% were multidrug resistant. The rate of multidrug resistance was higher among Strep. uberis (15%) than among Strep. dysgalactiae (6%) and Strep. agalactiae (0%). Resistance to tetracycline was the most common, followed by resistance to erythromycin, pirlimycin, and gentamicin. Resistance rates were higher on farms with more than 80 cows compared with those with fewer than 20 cows. β-Lactams should remain the drugs of choice in the treatment of streptococcal mastitis. The slightly elevated minimum inhibitory concentrations determined for these antibiotics may indicate, however, the emergence of resistant streptococci. To identify such changes in susceptibility as early as possible, antimicrobial resistance in streptococci should be surveyed regularly.

SDF-1 in myocardial repair

Stem cell therapy for the prevention and treatment of cardiac dysfunction holds significant promise for patients with ischemic heart disease. Excitingly early clinical studies have demonstrated safety and some clinical feasibility, while at the same time studies in the laboratory have investigated mechanisms of action and strategies to optimize the effects of regenerative cardiac therapies. One of the key pathways that has been demonstrated critical in stem cell-based cardiac repair is (stromal cell-derived factor-1) SDF-1:CXCR4. SDF-1:CXCR4 has been shown to affect stem cell homing, cardiac myocyte survival and ventricular remodeling in animal studies of acute myocardial infarction and chronic heart failure. Recently released clinical data suggest that SDF-1 alone is sufficient to induce cardiac repair. Most importantly, studies like those on the SDF-1:CXCR4 axis have suggested mechanisms critical for cardiac regenerative therapies that if clinical investigators continue to ignore will result in poorly designed studies that will continue to yield negative results.