The stress clot: Mid-cavitary variant takotsubo cardiomyopathy with left ventricular thrombus.

Pregnancy and the post-partum period are known hypercoagulable states. Mid-cavitary variant Takotsubo cardiomyopathy (TCM) is uncommon and seen in only about 14% of all Takotsubo cases. Left ventricular thrombus (LVT) in the setting of mid-cavitary TCM is extremely rare, occurring in approximately 1% of cases. We describe a case of a young female, 1-week post-partum, with an acute LVT in the setting of mid-ventricular TCM, and we discuss the striking images and clinical management of this uncommon presentation.

MRI in Patients with Cardiovascular Implantable Electronic Devices and Fractured or Abandoned Leads.

Purpose To examine the clinical effect of lead length and lead orientation in patients with cardiac implantable electronic devices (CIEDs) and lead fragments or abandoned leads undergoing 1.5-T MRI. Materials and Methods This Health Insurance Portability and Accountability Act-compliant retrospective study included patients with CIEDs and abandoned leads or lead fragments undergoing 1.5-T MRI from March 2014 through July 2020. CIED settings before and after MRI were reviewed, with clinically significant variations defined as a composite of the change in capture threshold of at least 50%, in sensing of at least 40%, or in lead impedance of at least 30% between before MRI and after MRI interrogation. Adverse clinical events were assessed at MRI and up to 30 days after. Univariable and multivariable analysis was performed. Results Eighty patients with 126 abandoned CIED leads or lead fragments underwent 107 1.5-T MRI examinations. Sixty-seven patients (median age, 74 years; IQR, 66-78 years; 44 male patients, 23 female patients) had abandoned leads, and 13 (median age, 66 years; IQR, 52-74 years; nine male patients, four female patients) had lead fragments. There were no reported deaths, clinically significant arrhythmias, or adverse clinical events within 30 days of MRI. Three patients with abandoned leads had a significant change in the composite of capture threshold, sensing, or lead impedance. In a multivariable generalized estimating equation analysis, lead orientation, lead length, MRI type, and MRI duration were not associated with a significant change in the composite outcome. Conclusion Use of 1.5-T MRI in patients with abandoned CIED leads or lead fragments of varying length and orientation was not associated with adverse clinical events. Keywords: Cardiac Assist Devices, MRI, Cardiac Implantable Electronic Device Supplemental material is available for this article. © RSNA, 2024.

Effectiveness of exercise modalities on breast cancer patient outcomes: a systematic review and meta-analysis.

BACKGROUND: The effects of exercise in patients with breast cancer (BC), has shown some profit, but consistency and magnitude of benefit remains unclear. We aimed to conduct a meta-analysis to assess the benefits of varying types of exercises in patients with BC. METHODS: Literature search was conducted across five electronic databases (MEDLINE, Web of Science, Scopus, Google Scholar and Cochrane) from 1st January 2000 through 19th January 2024. Randomized controlled trials (RCTs) assessing the impact of different types of exercise on outcomes related to fitness and quality of life (QOL) in patients with BC were considered for inclusion. Outcomes of interest included cardiorespiratory fitness (CRF), health-related quality of life (HRQOL), muscle strength, fatigue and physical function. Evaluations were reported as mean differences (MDs) with 95% confidence intervals (CIs) and pooled using random effects model. A p value < 0.05 was considered significant. RESULTS: Thirty-one relevant articles were included in the final analysis. Exercise intervention did not significantly improved the CRF in patients with BC when compared with control according to treadmill ergometer scale (MD: 4.96; 95%Cl [-2.79, 12.70]; P = 0.21), however exercise significantly improved CRF according to cycle ergometer scales (MD 2.07; 95% Cl [1.03, 3.11]; P = 0.0001). Physical function was significantly improved as well in exercise group reported by 6-MWT scale (MD 80.72; 95% Cl [55.67, 105.77]; P < 0.00001). However, exercise did not significantly improve muscle strength assessed using the hand grip dynamometer (MD 0.55; 95% CI [-1.61, 2.71]; P = 0.62), and fatigue assessed using the MFI-20 (MD -0.09; 95% CI [-5.92, 5.74]; P = 0.98) and Revised Piper scales (MD -0.26; 95% CI [-1.06, 0.55] P = 0.53). Interestingly, exercise was found to improve HRQOL when assessed using the FACT-B scale (MD 8.57; 95% CI [4.53, 12.61]; P < 0.0001) but no significant improvements were noted with the EORTIC QLQ-C30 scale (MD 1.98; 95% CI [-1.43, 5.40]; P = 0.25). CONCLUSION: Overall exercise significantly improves the HRQOL, CRF and physical function in patients with BC. HRQOL was improved with all exercise types but the effects on CRF vary with cycle versus treadmill ergometer. Exercise failed to improve fatigue-related symptoms and muscle strength. Large RCTs are required to evaluate the effects of exercise in patients with BC in more detail.

Aortic stenosis and perioperative risk: the other obstructive defect .

Whilst the prevalence of aortic valve stenosis (AS) increases with age (1), surgery restores age-corrected survival to near normal. In parallel with senescence, comorbidities are present, one such example being chronic obstructive pulmonary disease (COPD), which causes significant disability and is the third leading cause of death in the United Sates (2). The presence of COPD is associated with increased perioperative complications, and serve as a reason to deny a patient surgical intervention because of the increased surgical risk (3).

Multiple symptomatic giant coronary aneurysms.

We describe a rare case of coronary artery aneurysms due to Kawasaki disease in an elderly patient. Our case presents multiple giant coronary artery aneurysms affecting the left coronary system which is less common compared with right coronary aneurysms. Giant coronary artery aneurysms are uncommon; even more rare is their association with ischemic symptoms, and treatment can be challenging. We describe a case of symptomatic multiple coronary artery aneurysms with symptom relief after coronary artery bypass grafting in an elderly patient.

Strangulation: A Cause or Mimicker of Global Myocardial Hypoxia on ECG.

ST segment changes are often associated with myocardial ischemia but may be mimickers. We present a 21-year-old male who suffered a cardiac arrest following a suicide attempt by strangulation. Initial ECG revealed diffuse ST depressions and ST elevation in augmented vector right (aVR), concerning myocardial ischemia. However, repeat ECG revealed normal ST segments and an echocardiogram revealed no wall motion abnormalities. This case highlights the effects of systemic hypoxia on cardiac muscle and the need for a broad differential diagnosis when interpreting an ECG. This is invaluable when ST segment changes mimic acute myocardial infarction, but the clinical scenario suggests global hypoxia.

Diagnosis, treatment, and management of pericardial effusion- review.

The hemodynamic stability of the heart and pericardium are maintained by the pericardial fluid of volume ∼10-50 ml. Pericardial effusion is associated with the abnormal accumulation of pericardial fluid in the pericardial cavity. Numerous imaging techniques are utilized to evaluate pericardial effusion including chest X-ray, electrocardiogram, transthoracic echocardiography, computed tomography scan, cardiac magnetic resonance imaging, and pericardiocentesis. Once diagnosed, there are numerous treatment options available for the management of patients with pericardial effusion. These include various invasive and non-invasive strategies such as pericardiocentesis, pericardial window, and sclerosing therapies. In recent times, few studies have been conducted to evaluate the safety and efficacy of each approach in routine clinical practice. In this review, we review the role of different modalities in the diagnosis of pericardial effusion while highlighting existing therapies aimed at the management and treatment of pericardial effusion.

Potential for sodium-glucose cotransporter-2 inhibitors in the management of metabolic syndrome: A systematic review and meta-analysis.

BACKGROUND: Landmark trials have established the benefits of sodium-glucose cotransporter-2 inhibitors (SGLT2-Is) in cardiovascular disease including heart failure with reduced and preserved ejection fraction and renal diseases regardless of the presence of diabetes mellitus. However, studies evaluating the role of SGLT2-Is in metabolic syndrome (MetS) are limited. AIM: This study primarily aimed to evaluate the impact of SGLT2-Is on the components of MetS. METHODS: Two independent reviewers and an experienced librarian searched Medline, Scopus and the Cochrane central from inception to December 9, 2021 to identify placebo controlled randomized controlled trials that evaluated the impact of SGLT2-Is on the components of MetS as an endpoint. Pre- and post-treatment data of each component were obtained. A meta-analysis was performed using the RevMan (version 5.3; Copenhagen: The Nordic Cochrane Center, The Cochrane Collaboration). RESULTS: Treatment with SGLT2-Is resulted in a decrease in fasting plasma glucose (-18.07 mg/dL; 95%CI: -25.32 to -10.82), systolic blood pressure (-1.37 mmHg; 95%CI: -2.08 to -0.65), and waist circumference (-1.28 cm; 95%CI: -1.39 to -1.18) compared to placebo. The impact on high-density lipoprotein cholesterol was similar to placebo (0.01 mg/dL; 95%CI: -0.05 to 0.07). CONCLUSION: SGLT2-Is have a promising role in the management of MetS.

Blood Cancer and the Heart: Light Chain Cardiomyopathy in Refractory Multiple Myeloma.

We report a case of a 57-year-old woman with a history of multiple myeloma (MM) and light chain (AL) amyloidosis who presented due to worsening dyspnea on exertion. Her MM has been refractory to multiple chemotherapy regimens and two autologous bone marrow transplantation. Diagnostic evaluations including serum kappa and lambda chains, echocardiogram, pyrophosphate cardiac scan, and cardiac magnetic resonance were indicative of a progression to AL cardiomyopathy. Addition of daratumumab to her regimen appeared to ameliorate the progression of AL cardiomyopathy. However, it was stopped due to adverse effects of pancytopenia and allergic reactions including skin rash and hives. She was hospitalized for heart failure exacerbation and died approximately 2 months following the discontinuation of daratumumab. This case highlights the late presentation of AL cardiomyopathy in refractory MM.

Virulent endocarditis due to Haemophilus parainfluenzae: A systematic review of the literature.

BACKGROUND: Haemophilus parainfluenzae (HPI) belongs to the HACEK (Haemophilus spp., Aggregatibacter spp., Cardiobacterium spp., Eikenella spp., and Kingella spp.) group of organisms. The HACEK group of organisms are a part of the oropharyngeal flora and can cause invasive opportunistic infection such infective endocarditis (IE) in hosts with compromised immunological barriers. AIM: To perform a 20-year systematic review of the literature characterizing the clinical presentation, epidemiology and prognosis of HPI IE. METHODS: We performed a systematic review of Medline, Pubmed, Scopus and Embase from 2000 to 2022 to identify all cases of HPI IE. RESULTS: Thirty-nine adult cases were identified. HPI IE was found to affect males slightly more than females and is common in patients with predisposing risk factors such as underlying valvular abnormalities. It mostly affected the mitral valve and had an indolent course; significantly sized vegetations (> 1 cm) developed in most cases. Central nervous system septic embolization was common. It had a favorable prognosis compared to staphylococcal and streptococcal IE. CONCLUSION: Clinicians should be attentive to the indolent course of HPI IE and the presence of predisposing risk factors in order to allow for timely management.

Massive Device-Related Thrombus After LAA Occlusion: Intraoperative Insights Into Mechanism.

In patients with a contraindication to oral anticoagulation, the left atrial appendage occlusion devices are an approved alternative. Device-related thrombus is a recognized complication, but underlying mechanisms are incompletely understood. In this case series, the authors describe potentially the same mechanism of thrombosis with intraoperative images of incomplete endothelialization. (Level of Difficulty: Intermediate.).

Does individualized guided selection of antiplatelet therapy improve outcomes after percutaneous coronary intervention? A systematic review and meta-analysis.

Background: The potential benefits of individualized guided selection of antiplatelet therapy over standard antiplatelet therapy in improving outcomes in patients undergoing percutaneous coronary intervention (PCI) have not been established. Therefore, we pooled evidence from available clinical trials to assess the effectiveness by comparing the two regimens in patients undergoing PCI. Methods: We queried two electronic databases, MEDLINE and Cochrane CENTRAL, from their inception to April 20, 2021 for published randomized controlled trials in any language that compared guided antiplatelet therapy, using either genetic testing or platelet function testing, versus standard antiplatelet therapy in patients undergoing PCI. The results from trials were presented as risk ratios (RRs) with 95% confidence intervals (CIs) and were pooled using a random-effects model. Results: Eleven eligible studies consisting of 18,465 patients undergoing PCI were included. Pooled results indicated that guided antiplatelet therapy, compared to standard therapy, was associated with a significant reduction in the incidence of MACE [RR 0·78, 95% CI (0·62-0·99), P = 0·04], MI [RR 0·73, 95% CI (0·56-0.96), P = 0·03], ST [RR 0·66, 95% CI (0·47-0.94), P = 0·02], stroke [RR 0·71, 95% CI (0·50-1.00), P = 0·05], and minor bleeding [RR 0·78, 95% CI (0·66-0.91), P = 0·003]. Conclusions: Individualized guided selection of antiplatelet therapy significantly reduced the incidence of MACE, MI, ST, stroke, and minor bleeding in adult patients when compared with standard antiplatelet therapy. Our findings support the implementation of genetic and platelet function testing to select the most beneficial antiplatelet agent.

DOACs or VKAs or LMWH - What is the optimal regimen for cancer-associated venous thromboembolism? A systematic review and meta-analysis.

Background: Clinical guidelines have supported the use of direct anticoagulants (DOACs) for the treatment of cancer-associated venous thromboembolism (Ca-VTE). However, recent trials have reported increased bleeding risks associated with DOACs usage, raising concerns regarding its efficacy. Objectives: The authors conducted a meta-analysis to study the efficacy and safety of DOACs for the treatment of VTE in cancer patients, compared with Low-weight molecular heparin (LMWH) and Vitamin-K antagonists (VKAs). Methods: PubMed, EMBASE, Cochrane Library, Cochrane Central Register of Controlled Trials (CENTRAL) were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines from inception to June 17th, 2021.The primary outcomes studied were VTE recurrence and major bleeding. Results: A total of 8 randomized controlled trials (RCTs) enrolling almost 7000 patients were included. Direct oral anticoagulants significantly reduced VTE Recurrence in cancer patients when compared to patients treated with LMWH or VKAs (Hazard ratio [HR] 0.62, 95% confidence interval [CI] 0.46-0.83; P = 0.002; I2 = 26%). There were no statistically significant differences for major bleeding (HR 0.86, 95% confidence interval [CI] 0.56-1.33; P = 0.50; I2 = 34%), clinically relevant non-major bleeding (HR 1.23, 95% confidence interval [CI] 0.79-1.91; P = 0.35; I2 = 66%), pulmonary embolism (HR 0.71, 95% confidence interval [CI] 0.47-1.06; P = 0.10; I2 = 7%), and all-cause mortality (HR 0.98, 95% confidence interval [CI] 0.86-1.12; P = 0.78; I2 = 1%), between DOACs and LMWH. Conclusion: This analysis shows that DOACs are the optimal regimen to treat Ca-VTE. They have a similar to slightly increased bleeding risk compared with LMWH and are a safer alternative to VKAs.

Global and Regional Variations in Transthyretin Cardiac Amyloidosis: A Comparison of Longitudinal Strain and 99mTc-Pyrophosphate Imaging.

There are limited data on the head-to-head comparison of 99mTc-pyrophosphate (99mTc-PYP) and echocardiographic strain imaging in the assessment of transthyretin (TTR) cardiac amyloidosis. Methods: At Mayo Clinic Arizona, patients who had undergone both a 99mTc-PYP scan and a transthoracic echocardiogram within a 90-d period were retrospectively identified for chart review and strain imaging analysis. Patients were divided into 2 groups according to their 99mTc-PYP results (PYP-positive [PYP+] or PYP-negative [PYP-]) for the comparison. A standard 17-segment model was used for segmental, regional, and global longitudinal strain comparison. A P value of less than 0.05 was deemed significant. Results: In total, 64 patients were included, the mean age was 75.1 ± 13.0 y, and 57 (89.1%) were male. Comparing the PYP+ to the PYP- group, the left ventricular global longitudinal strain was significantly worse in the former (PYP+ vs. PYP-, -10.5 ± 2.6 vs. -13.1 ± 4.1; P = 0.003). PYP+ patients also had worse regional basal strain (-4.6 ± 2.6 vs. -8.8 ± 4.0, P < 0.001) and a trend toward worse midventricular strain (-9.6 ± 4.0 vs. -11.7 ± 4.4, P = 0.07), but there was no statistical difference in the apical region (-17.6 ± 4.73 vs. -19.0 ± 6.46, P = 0.35). This is consistent with an apex-sparing pattern shown by the relative apical longitudinal strain index (1.3 ± 0.5 vs. 1.0 ± 0.3, P = 0.008). Segment-to-segment analysis demonstrated a significant difference in strain between PYP+ and PYP- segments in 4 segments: basal inferior (P = 0.006), basal anterolateral (P = 0.01), apical septal (P = 0.002), and apical inferior (P = 0.001). Left ventricular diastolic dysfunction was significantly different, with 17 (77.3%) patients in the PYP+ group versus 15 (36.6%) in PYP- participants (P = 0.002). Conclusion: Our study suggested that 99mTc-PYP uptake is related to overall worse LV segmental, regional, and global longitudinal strain function, as well as diastolic function, compared with patients without 99mTc-PYP uptake. These data are important for helping clinicians learn about the echocardiographic function features related to 99mTc-PYP uptake and can help generate hypotheses for future studies.

Efficacy of Sodium-Glucose Cotransporter-2 inhibitors in heart failure patients treated with dual angiotensin receptor blocker-neprilysin inhibitor: An updated meta-analysis.

BACKGROUND: Recent data suggest that the prevalence of heart failure has increased to approximately 23 million people globally. With increasing advancement in pharmacotherapeutics, Sodium-Glucose Cotransporter-2 inhibitors (SGLT2i) have garnered attention among clinicians to treat Heart failure with reduced ejection fraction (HFrEF) in diabetic as well as non-diabetic patients. METHODS: MEDLINE, Scopus, Embase and Cochrane CENTRAL database were searched using relevant keywords and MeSH terms. Studies were considered only if they were randomized in nature and had a sample size >1000 HF patients. RESULTS: Our comprehensive search strategy yielded 864 articles, of which three RCTs met the inclusion criteria with a total population of 9696. Pooled analysis revealed an association between the use of SGLT2i and decreased frequency of primary outcome irrespective of background ARNI use (HR 0.73, 95% CI [0.58-0.93], p = 0.0106; HR 0.73, 95% CI [0.66-0.81], p < 0.0001). CONCLUSION: This meta-analysis provides substantial evidence, to safely use SGLT2i atop ARNI therapy in select HF patients to further improve outcomes.

Prevalence and Outcomes of Pericardial Effusion in Kidney Transplant Candidates.

Pericardial disease is a recognized manifestation of cardiovascular disease in the end-stage renal disease (ESRD) population, and can manifest as pericardial effusion, though the prognosis of pericardial disease in ESRD patients is unclear. In the modern era of renal replacement therapy, little is known about the prevalence and the implications of pericardial effusion in ESRD patients, its echocardiographic characteristics, and risk factors. We conducted a retrospective chart review on subjects > than 18 years of age with known ESRD who were undergoing outpatient evaluation for renal transplantation at Mayo Clinic Arizona between January 2001 and December 2015 and had baseline echocardiogram completed within 3 months of their initial evaluation. Patients with moderate sized pericardial effusions or larger were identified. The pericardial effusion cohort was age and gender matched with a cohort of patients with ESRD without pericardial effusion in a 1:2 fashion. 54 patients with moderate or greater sized pericardial effusion out of 2,820 patients that fit our inclusion criteria, corresponding to a prevalence of 1.9%. A total of 41 patients or 75.9%, had a moderate sized effusion. A total of 13 patients, or 24.1% had a large sized effusion, 7 of whom had tamponade physiology on echocardiography. The presence and size of the effusion was not predictive for worse outcomes. Hemodialysis duration was protective, but no other factors were predictive or protective in the development of moderate sized or larger pericardial effusions, including echocardiographic parameters.

Urinary Voiding as a Tool to Reduce Radiation Exposure in the Nuclear Stress Lab.

Nuclear stress testing is being increasingly justified in the cardiovascular risk stratification of patients. Radiation is an important consideration, and attempts to minimize exposure should be implemented. Efficiency and cost effectiveness are cornerstones in the delivery of quality patient care and should also be considered when implementing change. Methods: We studied 88 consecutive patients who presented to our stress lab for pharmacologic nuclear stress testing. A single-day rest-and-stress protocol with low-level exercise was used for all patients. After the stress portion of the examination, we measured Geiger counter activity above the bladder area to establish a baseline. Patients were then allowed to void, and repeat measurements were taken. Results: We detected a 16.9% reduction from baseline radiation levels above the bladder area after voiding. Conclusion: Urinary voiding is a simple, cost-effective strategy at reducing radiation exposure in the nuclear stress lab.

Effects of Pectus Excavatum Repair on Right and Left Ventricular Strain.

BACKGROUND: The cardiopulmonary benefits of pectus excavatum repair have been debated. Echocardiographic speckle-tracking strain and strain rate have been used to evaluate and detect subclinical myocardial dysfunction in patients receiving cardiotoxic chemotherapy, and patients with valvular heart disease. This technology was applied to evaluate the effects of pectus excavatum surgery on left ventricular (LV) and right ventricular (RV) function. METHODS: Speckle tracing strain evaluation was performed on intraoperative transesophageal echocardiographic images acquired immediately before and after Nuss repair in adult patients (aged 18 years or more) from 2011 to 2014. Standard severity and compression indices were measured on chest imaging performed before pectus excavatum repair. RESULTS: In total, 165 patients with transesophageal echocardiographic images during repair were reviewed (71.5% male; mean age 33.0 years; range, 18 to 71; Haller index 5.7; range, 2.3 to 24.3). Significant improvement after repair was seen in global RV longitudinal strain (-13.5% ± 4.1% to -16.7% ± 4.4%, p < 0.0001) and strain rate (-1.3 ± 0.4 s-1 to -1.4 ± 0.4 s-1, p = 0.0102); LV global circumferential strain (-18.7% ± 5.7% to -23.5% ± 5.8%, p < 0.0001) and strain rate (-1.5 ± 0.5 s-1 to -1.9 ± 0.8 s-1, p = 0.0003); and LV radial strain (24.1% ± 13.5% to 31.1% ± 16.4%, p = 0.0050). There was a strong correlation between preoperative right atrial compression on transesophageal echocardiogram and improvement in RV global longitudinal strain rate immediately after pectus repair. CONCLUSIONS: Mechanical compression and impaired RV and LV strain is improved by Nuss surgical repair of pectus deformity.

Cardiorespiratory Fitness (Peak Oxygen Uptake): Safe and Effective Measure for Cardiovascular Screening Before Kidney Transplant.

BACKGROUND: Significant heterogeneity exists in practice patterns and algorithms used for cardiac screening before kidney transplant. Cardiorespiratory fitness, as measured by peak oxygen uptake (VO2peak), is an established validated predictor of future cardiovascular morbidity and mortality in both healthy and diseased populations. The literature supports its use among asymptomatic patients in abrogating the need for further cardiac testing. METHODS AND RESULTS: We outlined a pre-renal transplant screening algorithm to incorporate VO2peak testing among a population of asymptomatic high-risk patients (with diabetes mellitus and/or >50 years of age). Only those with VO2peak <17 mL/kg per minute (equivalent to <5 metabolic equivalents) underwent further noninvasive cardiac screening tests. We conducted a retrospective study of the a priori dichotomization of the VO2peak <17 versus ≥17 mL/kg per minute to determine negative and positive predictive value of future cardiac events and all-cause mortality. We report a high (>90%) negative predictive value, indicating that VO2peak ≥17 mL/kg per minute is effective to rule out future cardiac events and all-cause mortality. However, lower VO2peak had low positive predictive value and should not be used as a reliable metric to predict future cardiac events and/or mortality. In addition, a simple mathematical calculation documented a cost savings of ≈$272 600 in the cardiac screening among our study cohort of 637 patients undergoing evaluation for kidney and/or pancreas transplant. CONCLUSIONS: We conclude that incorporating an objective measure of cardiorespiratory fitness with VO2peak is safe and allows for a cost savings in the cardiovascular screening protocol among higher-risk phenotype (with diabetes mellitus and >50 years of age) being evaluated for kidney transplant.

SDF-1 recruits cardiac stem cell-like cells that depolarize in vivo.

Prolongation or reestablishment of stem cell homing through the expression of SDF-1 in the myocardium has been shown to lead to homing of endothelial progenitor cells to the infarct zone with a subsequent increase in vascular density and cardiac function. While the increase in vascular density is important, there could clearly be other mechanisms involved. In a recent study we demonstrated that the infusion of mesenchymal stem cells (MSC) and MSC that were engineered to overexpress SDF-1 led to significant decreases in cardiac myocyte apoptosis and increases in vascular density and cardiac function compared to control. In that study there was no evidence of cardiac regeneration from either endogenous stem cells or the infused mesenchymal stem cells. In this study we performed further detailed immunohistochemistry on these tissues and demonstrate that the overexpression of SDF-1 in the newly infracted myocardium led to recruitment of small cardiac myosin-expressing cells that had proliferated within 2 weeks of acute MI. These cells did not differentiate into mature cardiac myocytes, at least by 5 weeks after acute MI. However, based on optical mapping studies, these cells appear capable of depolarizing. We observed greater optical action potential amplitude in the infarct border in those animals that received SDF-1 overexpressing MSC than observed in noninfarcted animals and those that received control MSC. Further immunohistochemistry revealed that these proliferated cardiac myosin-positive cells did not express connexin 43, but did express connexin 45. In summary, our study suggests that the prolongation of SDF-1 expression at the time of acute MI leads to the recruitment of endogenous cardiac myosin stem cells that may represent cardiac stem cells. These cells are capable of depolarizing and thus may contribute to increased contractile function even in the absence of maturation into a mature cardiac myocyte.