Left atrial strain in adults after the arterial switch operation for transposition of the great arteries.

BACKGROUND: No study has focused on left atrial (LA) function assessed by echocardiography in adult patients with simple D-TGA after arterial switch operation (ASO). We aimed to describe LA strain parameters in these patients. METHODS: A prospective cohort study including 42 adult patients with simple D-TGA after ASO and 33 aged-matched controls. Phasic LA and LV global longitudinal strain (GLS) were obtained by transthoracic 2D-speckle tracking echocardiography (STE). Volumetric and functional analysis of LA and LV were also evaluated by 2D and 3D analysis. A multivariable model was performed to investigate the variables that best differentiate patients with D-TGA from healthy controls. RESULTS: LA strain parameters in D-TGA patients were within the normal range described for healthy subjects. However, the three LA strain parameters (Reservoir, Conduit, and Contraction) were lower in patients (LASr: 31.13 ± 7.67 vs. 49.71 ± 8.38; LAS cd: -22.91 ± 5.69 vs. -34.55 ± 6.54; LASct: -8.14 ± 4.93 vs. -15.15 ± 6.07, p < .001 for all three comparisons). LA volumes were similar between patients and controls. LV-GLS remained significantly lower in the D-TGA group than in controls (-17.29 ± 2.68 vs. -21.98 ± 1.84, p < .001). D-TGA patients had evidence of worse LV ejection fraction measured by the Teichholz method (63.38 ± 8.23 vs. 69.28 ± 5.92, p = .001) and 3D analysis (57.97% ± 4.16 vs. 60.67 ± 3.39, p = .011) and diastolic dysfunction as compared to healthy controls. LV-GLS and conduit LAS were the variables best differentiating patients with D-TGA from healthy controls. CONCLUSIONS: LA strain is impaired in young adults with simple D-TGA late after the ASO, probably in agreement with some degree of LV dysfunction previously described.

Incidence and Risk Factors for Development of Cardiac Toxicity in Adult Patients with Newly Diagnosed Acute Myeloid Leukemia.

The incidence of cardiac morbimortality in acute myeloid leukemia (AML) is not well known. We aim to estimate the cumulative incidence (CI) of cardiac events in AML patients and to identify risk factors for their occurrence. Among 571 newly diagnosed AML patients, 26 (4.6%) developed fatal cardiac events, and among 525 treated patients, 19 (3.6%) experienced fatal cardiac events (CI: 2% at 6 months; 6.7% at 9 years). Prior heart disease was associated with the development of fatal cardiac events (hazard ratio (HR) = 6.9). The CI of non-fatal cardiac events was 43.7% at 6 months and 56.9% at 9 years. Age ≥ 65 (HR = 2.2), relevant cardiac antecedents (HR = 1.4), and non-intensive chemotherapy (HR = 1.8) were associated with non-fatal cardiac events. The 9-year CI of grade 1-2 QTcF prolongation was 11.2%, grade 3 was 2.7%, and no patient had grade 4-5 events. The 9-year CI of grade 1-2 cardiac failure was 1.3%, grade 3-4 was 15%, and grade 5 was 2.1%; of grade 1-2, arrhythmia was 1.9%, grade 3-4 was 9.1%, and grade 5 was 1%. Among 285 intensive therapy patients, median overall survival decreased in those experiencing grade 3-4 cardiac events (p < 0.001). We observed a high incidence of cardiac toxicity associated with significant mortality in AML.

Spatiotemporal Complexity of Vena Contracta and Mitral Regurgitation Grading Using Three-Dimensional Echocardiographic Analysis.

BACKGROUND: Spatiotemporal complexity of the color Doppler vena contracta challenging the assumption of a circular and constant orifice may lead to mitral regurgitation (MR) grading inconsistencies. Using 3D transesophageal echocardiography, we characterized spatiotemporal vena contracta complexity and its impact on MR severity grading. METHODS: In 192 patients with suspected moderate or severe MR (100 primary MR [PMR]; 92 secondary MR [SMR]), we performed three-dimensional vena contracta area (VCA) quantification using single-frame (midsystolic or VCAmid, maximum or VCAmax) and multiframe (VCAmean) methods, as well as measures of orifice shape (shape index) and systolic variation of VCA. Vena contracta complexity and intermethod discrepancies were analyzed and correlated with functional class and pulmonary vein flow (PVF) patterns and with cardiac magnetic resonance (CMR) in a subset of cases (n = 20). RESULTS: The vena contracta was noncircular (shape index > 1.5) in 90% of patients. Severe noncircularity (shape index > 3) was more prevalent in SMR than in PMR (32.4% vs 14.6%). Variations of the VCA were more prominent in SMR than in PMR. VCAmid showed a low grading agreement with VCAmax (62%) and high grading agreement with VCAmean (83.3%). Pulmonary vein flow systolic reversal was associated with MR severity by VCA in SMR but not in PMR. VCAmid and VCAmean showed a stronger association with systolic flow reversal than VCAmax (area under the curve, 0.88, 0.86, and 0.79, respectively). In the subset of patients with CMR quantification, severe MR by VCAmax was graded as nonsevere by CMR more frequently compared with VCAmid and VCAmean. CONCLUSIONS: Highly prevalent spatiotemporal vena contracta complexity features in MR challenge the assumption of a circular and constant orifice. VCAmid seems the best single-frame approximation to multiframe quantification, and VCAmax may lead to severity overestimation.

Endobronchial Aerosolized AAV1.SERCA2a Gene Therapy in a Pulmonary Hypertension Pig Model: Addressing the Lung Delivery Bottleneck.

A disappointing number of new therapies for pulmonary hypertension (PH) have been successfully translated to the clinic. Adeno-associated viral (AAV) gene therapy has the potential to treat the underlying pathology of PH, but the challenge remains in efficient and safe delivery. The aims of this study were (1) to test the efficacy of endobronchial aerosolization delivery for AAV1-mediated sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) gene therapy in a PH pig model and (2) to identify the most efficient airway administration modality for in-lung gene therapy in PH. We hypothesized that delivery to the distal bronchi increases lung viral uptake and avoids virus loss in off-target compartments. In part 1 of the study, PH was induced in pigs by surgically banding the pulmonary veins. Two months postsurgery, 1 × 1013 viral genomes (vg) of AAV1.SERCA2a or saline was endobronchially aerosolized using a bronchoscope. Two months after aerosolization, high vg copies (vgc) were detected in the lungs, accompanied by functional and morphometrical amelioration of PH. In part 2 of the study, we directly compared the endobronchial aerosolization gene delivery to the intratracheal aerosolization in PH pigs. Endobronchial delivery demonstrated higher viral expression (6,719 ± 927 vs. 1,444 ± 402 vgc/100 ng DNA, p = 0.0017), suggesting this delivery modality is a promising method for clinical AAV gene therapy for PH.

Rationale and design of the pragmatic clinical trial tREatment with Beta-blockers after myOcardial infarction withOut reduced ejection fracTion (REBOOT).

AIMS: There is a lack of evidence regarding the benefits of ß-blocker treatment after invasively managed acute myocardial infarction (MI) without reduced left ventricular ejection fraction (LVEF). METHODS AND RESULTS: The tREatment with Beta-blockers after myOcardial infarction withOut reduced ejection fracTion (REBOOT) trial is a pragmatic, controlled, prospective, randomized, open-label blinded endpoint (PROBE design) clinical trial testing the benefits of ß-blocker maintenance therapy in patients discharged after MI with or without ST-segment elevation. Patients eligible for participation are those managed invasively during index hospitalization (coronary angiography), with LVEF >40%, and no history of heart failure (HF). At discharge, patients will be randomized 1:1 to ß-blocker therapy (agent and dose according to treating physician) or no ß-blocker therapy. The primary endpoint is a composite of all-cause death, non-fatal reinfarction, or HF hospitalization over a median follow-up period of 2.75 years (minimum 2 years, maximum 3 years). Key secondary endpoints include the incidence of the individual components of the primary composite endpoint, the incidence of cardiac death, and incidence of malignant ventricular arrhythmias or resuscitated cardiac arrest. The primary endpoint will be analysed according to the intention-to-treat principle. CONCLUSION: The REBOOT trial will provide robust evidence to guide the prescription of ß-blockers to patients discharged after MI without reduced LVEF.

Procedural-related coronary atrial branch occlusion during primary percutaneous coronary intervention for ST-segment elevation myocardial infarction and atrial arrhythmias at follow-up.

OBJECTIVES: To evaluate the frequency of procedural-related atrial branch occlusion in ST-segment elevation myocardial infarction (STEMI) patients and its association with atrial arrhythmias at 1-year follow-up. BACKGROUND: Atrial ischemia due to procedural-related coronary atrial branch occlusion in elective percutaneous coronary intervention (PCI) has been associated with atrial arrhythmias. Its role in a STEMI scenario is unknown. METHODS: STEMI patients treated with primary PCI were classified according to the loss or patency of an atrial branch at the end of the procedure. The occurrence of atrial arrhythmias was documented on 24-hr Holter-ECG at 3 and 6 months or on ECG during 1-year follow-up visits. RESULTS: Of 900 patients, 355 (age 61 ± 12 years, 79% male) underwent primary PCI involving the origin of an atrial branch. Procedural-related coronary atrial branch occlusion was observed in 18 (5%) individuals). During 1-year follow-up, 33% of patients with procedural-related atrial branch occlusion presented atrial arrhythmias, as compared with 55% in those with a patent atrial branch (p = .088). Age, no previous history of myocardial infarction, and a reduced flow in the culprit vessel were the only independent correlates of atrial arrhythmias. CONCLUSIONS: The frequency of procedural-related atrial branch occlusion during primary PCI is low (5%) and is not associated with increased frequency of atrial arrhythmias at 1-year follow-up.

Echocardiographic Left Ventricular Mass Estimation: Two-Dimensional Area-Length Method is Superior to M-Mode Linear Method in Swine Models of Cardiac Diseases.

Echocardiography offers rapid and cost-effective estimations of left ventricular (LV) mass, but its accuracy in patients with cardiac disease remains unclear. LV mass was measured by M-mode-based linear method and two-dimensional echocardiography (2DE)-based area-length method in pig models and correlation with actual LV weight was assessed. Twenty-six normal, 195 ischemic heart disease (IHD), and 33 non-IHD HF pigs were included. A strong positive linear relationship to the actual LV weight was found with 2DE-based area-length method (r = 0.82, p < 0.001), whereas a moderate relationship was found with M-mode method in the overall population (r = 0.68, p < 0.001). Two correlation coefficients were significantly different (p < 0.001), and were driven mainly by incremental overestimation of LV mass in heavier hearts using the M-mode method. IHD and LV dilation were the factors contributing to overestimation using M-mode method. 2DE-based area-length method provides a better estimation of LV weight in swine models of HF, particularly in those with IHD.

R2 prime (R2') magnetic resonance imaging for post-myocardial infarction intramyocardial haemorrhage quantification.

AIMS: To assess whether R2* is more accurate than T2* for the detection of intramyocardial haemorrhage (IMH) and to evaluate whether T2' (or R2') is less affected by oedema than T2* (R2*), and thus more suitable for the accurate identification of post-myocardial infarction (MI) IMH. METHODS AND RESULTS: Reperfused anterior MI was performed in 20 pigs, which were sacrificed at 120 min, 24 h, 4 days, and 7 days. At each time point, cardiac magnetic resonance (CMR) T2- and T2*-mapping scans were recorded, and myocardial tissue samples were collected to quantify IMH and myocardial water content. After normalization by the number of red blood cells in remote tissue, histological IMH increased 5.2-fold, 10.7-fold, and 4.1-fold at Days 1, 4, and 7, respectively. The presence of IMH was correlated more strongly with R2* (r = 0.69; P = 0.013) than with T2* (r = -0.50; P = 0.085). The correlation with IMH was even stronger for R2' (r = 0.72; P = 0.008). For myocardial oedema, the correlation was stronger for R2* (r = -0.63; P = 0.029) than for R2' (r = -0.50; P = 0.100). Multivariate linear regressions confirmed that R2* values were significantly explained by both IMH and oedema, whereas R2' values were mostly explained by histological IMH (P = 0.024) and were little influenced by myocardial oedema (P = 0.262). CONCLUSION: Using CMR mapping with histological validation in a pig model of reperfused MI, R2'more accurately detected IMH and was less influenced by oedema than R2* (and T2*). Further studies are needed to elucidate whether R2' is also better suited for the characterization of post-MI IMH in the clinical setting.

Quantitative Transthoracic Echocardiography of the Response to Dobutamine in Cardiac Surgery Patients With Low Cardiac Output Syndrome.

OBJECTIVE: To quantify the acute effects of dobutamine in postoperative low cardiac output syndrome (LCOS) using transthoracic echocardiographic, hemodynamic, and blood biomarker monitoring and to assess its association with clinical outcomes. DESIGN: Observational prospective study. SETTING: Single university hospital. PARTICIPANTS: Patients undergoing elective cardiac surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Echocardiographic parameters, hemodynamic data, and plasma biomarkers were obtained before and early after inotrope initiation. The diagnostic value of transthoracic echocardiographic parameters and their association with clinical outcome were evaluated. Thirty-eight LCOS patients and 12 control patients were included. The left ventricular outflow tract velocity time integral was significantly lower in LCOS patients (11.75 v 19.08 cm; p < 0.001) and showed a marked improvement after dobutamine administration (∼37% increase). Dobutamine improved left and right ventricular function, increased mean arterial pressure and urine output, and lowered lactate levels. The duration of dobutamine support, but not in-hospital mortality, was associated with echocardiographic estimates of cardiac performance early after dobutamine initiation. CONCLUSIONS: Early transthoracic echocardiographic assessment and the acute response to inotropic therapy may provide rapid and highly valuable information in the diagnostic workup and risk evaluation of patients with suspected LCOS after cardiac surgery.

Sequential Bone-Marrow Cell Delivery of VEGFA/S1P Improves Vascularization and Limits Adverse Cardiac Remodeling After Myocardial Infarction in Mice.

Microvascular dysfunction and resulting tissue hypoxia is a major contributor to the pathogenesis and evolution of cardiovascular diseases (CVD). Diverse gene and cell therapies have been proposed to preserve the microvasculature or boost angiogenesis in CVD, with moderate benefit. This study tested in vivo the impact of sequential delivery by bone-marrow (BM) cells of the pro-angiogenic factors vascular endothelial growth factor (VEGFA) and sphingosine-1-phosphate (S1P) in a myocardial infarction model. For that, mouse BM cells were transduced with lentiviral vectors coding for VEGFA or sphingosine kinase (SPHK1), which catalyzes S1P production, and injected them intravenously 4 and 7 days after cardiac ischemia-reperfusion in mice. Sequential delivery by transduced BM cells of VEGFA and S1P led to increased endothelial cell numbers and shorter extravascular distances in the infarct zone, which support better oxygen diffusion 28 days post myocardial infarction, as shown by automated 3D image analysis of the microvasculature. Milder effects were observed in the remote zone, together with increased proportion of capillaries. BM cells delivering VEGFA and S1P also decreased myofibroblast abundance and restricted adverse cardiac remodeling without major impact on cardiac contractility. The results indicate that BM cells engineered to deliver VEGFA/S1P angiogenic factors sequentially may constitute a promising strategy to improve micro-vascularization and oxygen diffusion, thus limiting the adverse consequences of cardiac ischemia.

Serial Magnetic Resonance Imaging to Identify Early Stages of Anthracycline-Induced Cardiotoxicity.

BACKGROUND: Anthracycline-induced cardiotoxicity is a major clinical problem, and early cardiotoxicity markers are needed. OBJECTIVES: The purpose of this study was to identify early doxorubicin-induced cardiotoxicity by serial multiparametric cardiac magnetic resonance (CMR) and its pathological correlates in a large animal model. METHODS: Twenty pigs were included. Of these, 5 received 5 biweekly intracoronary doxorubicin doses (0.45 mg/kg/injection) and were followed until sacrifice at 16 weeks. Another 5 pigs received 3 biweekly doxorubicin doses and were followed to 16 weeks. A third group was sacrificed after the third dose. All groups underwent weekly CMR examinations including anatomical and T2 and T1 mapping (including extracellular volume [ECV] quantification). A control group was sacrificed after the initial CMR. RESULTS: The earliest doxorubicin-cardiotoxicity CMR parameter was T2 relaxation-time prolongation at week 6 (2 weeks after the third dose). T1 mapping, ECV, and left ventricular (LV) motion were unaffected. At this early time point, isolated T2 prolongation correlated with intracardiomyocyte edema secondary to vacuolization without extracellular space expansion. Subsequent development of T1 mapping and ECV abnormalities coincided with LV motion defects: LV ejection fraction declined from week 10 (2 weeks after the fifth and final doxorubicin dose). Stopping doxorubicin therapy upon detection of T2 prolongation halted progression to LV motion deterioration and resolved intracardiomyocyte vacuolization, demonstrating that early T2 prolongation occurs at a reversible disease stage. CONCLUSIONS: T2 mapping during treatment identifies intracardiomyocyte edema generation as the earliest marker of anthracycline-induced cardiotoxicity, in the absence of T1 mapping, ECV, or LV motion defects. The occurrence of these changes at a reversible disease stage shows the clinical potential of this CMR marker for tailored anthracycline therapy.

Changes in Adrenoceptor and GRK Expression in Patients With Chronic Pulmonary Regurgitation.

INTRODUCTION AND OBJECTIVES: Pulmonary regurgitation (PR) is a frequent complication after repair of congenital heart disease. Lymphocyte expression of adrenoceptors (ß1 and ß2) and kinases (GRK2, GRK3, and GRK5) reflects the neurohumoral changes that occur in heart failure (HF). The main objective of this study was to describe the gene expression of these molecules in circulating lymphocytes in patients with severe PR. METHODS: A prospective study was conducted to analyze lymphocyte expression of these molecules in patients with severe PR and compare it with expression in healthy controls and patients with advanced HF. RESULTS: We studied 35 patients with severe PR, 22 healthy controls, and 13 patients with HF. Multiple comparisons analysis showed that ß2-adrenoceptor gene expression levels were higher in the control group than in patients in the PR and HF groups and that expression in the latter 2 groups was similar (748.49 [rank 1703.87] vs 402.80 [rank 1210.81] vs 287.46 [rank 685.69] P = .001). Similar findings were obtained in gene expression of GRK2 (760.89 [rank 1169.46] vs 445.17 [rank 1190.69] vs 284.09 [rank 585.27] P < .001). There were no differences in expression levels of these molecules according to clinical variables in patients with PR. CONCLUSIONS: The gene expression pattern of GRK2 and ß2-adrenoceptor as molecular markers of cardiac dysfunction was altered in patients with severe PR compared with controls and was similar to expression in patients with advanced HF.

Primary Effect of SERCA 2a Gene Transfer on Conduction Reserve in Chronic Myocardial Infarction.

Background SERCA 2a gene transfer ( GT ) improves mechano-electrical function in animal models of nonischemic heart failure Whether SERCA 2a GT reverses pre-established remodeling at an advanced stage of ischemic heart failure is unclear. We sought to uncover the electrophysiological effects of adeno-associated virus serotype 1. SERCA 2a GT following myocardial infarction ( MI ). Methods and Results Pigs developed mechanical dysfunction 1 month after anterior MI , at which point they received intracoronary adeno-associated virus serotype 1. SERCA 2a ( MI + SERCA 2a) or saline ( MI ) and were maintained for 2 months. Age-matched naive pigs served as controls (Control). In vivo ECG -and-hemodynamic properties were assessed before and after dobutamine stress. The electrophysiological substrate was measured using optical action potential ( AP ) mapping in controls, MI , and MI + SERCA 2a preparations. In vivo ECG measurements revealed comparable QT durations between groups. In contrast, prolonged QRS duration and increased frequency of R' waves were present in MI but not MI + SERCA 2a pigs relative to controls. SERCA 2a GT reduced in in vivo arrhythmias in response to dobutamine. Ex vivo preparations from MI but not MI + SERCA 2a or control pigs were prone to pacing-induced ventricular tachycardia and fibrillation. Underlying these arrhythmias was pronounced conduction velocity slowing in MI versus MI + SERCA 2a at elevated rates leading to ventricular tachycardia and fibrillation. Reduced susceptibility to ventricular tachycardia and fibrillation in MI + SERCA 2a pigs was not related to hemodynamic function, contractile reserve, fibrosis, or the expression of Cx43 and Nav1.5. Rather, SERCA 2a GT decreased phosphoactive CAMKII -delta levels by >50%, leading to improved excitability at fast rates. Conclusions SERCA 2a GT increases conduction velocity reserve, likely by preventing CAMKII overactivation. Our findings suggest a primary effect of SERCA 2a GT on myocardial excitability, independent of altered mechanical function.

Author Correction: Deciphering microvascular changes after myocardial infarction through 3D fully automated image analysis.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Safety and long-term efficacy of AAV1.SERCA2a using nebulizer delivery in a pig model of pulmonary hypertension.

Nebulization delivery of adeno-associated virus serotype 1 encoding sarcoplasmic reticulum Ca2+-ATPase2a (AAV1.SERCA2a) gene was examined in a Yukatan miniature swine model of chronic pulmonary hypertension (n = 13). Nebulization of AAV1.SERCA2a resulted in homogenous distribution of vectors, lower pulmonary vascular resistance, and a trend towards better long-term survival compared to control animals.

Chronic Pulmonary Artery Embolization Models in Large Animals.

A wide range of approaches have been described to develop animal models of pulmonary vascular disease (PVD). Clinical heterogeneity in patients with pulmonary hypertension (PH) has prompted development of different techniques to create PH models in several animal species with the objective to recapitulate specific PH/PVD phenotypes. Chronic thromboembolic PH (CTEPH) is a clinically important phenotype of PH with a documented prevalence of 0.4-9.1% in patients with history of pulmonary embolism. A well-established large animal model of CTEPH is thus necessary for studying this disease in preclinical research. Different experimental protocols with inconsistent outcomes have been reported in the literature.We have focused on characterizing PH large animal models in a common framework; pulmonary hemodynamics, right ventricular (RV) function, and histological characterization of PVD. This research framework allows optimal evaluation of novel diagnostic tools, as well as new therapeutic strategies. The purpose of this protocol is to describe approaches to create experimental CTEPH models using recurrent pulmonary embolizations of dextran microspheres in swine. The key features of this experimental modeling approach are (1) nonsurgical, fully percutaneous techniques, (2) a minimum of four embolization procedures, with 1-2 month time period, (3) mild to moderate PH hemodynamics (mean PA pressure increase ~20-60%), (4) severe pulmonary vascular remodeling, (5) mild RV remodeling, and (6) a high reproducibility and low mortality (<10%).

Modeling Pulmonary Hypertension: A Pig Model of Postcapillary Pulmonary Hypertension.

Pulmonary hypertension (PH) is a pathophysiological condition defined as an increase in mean pulmonary arterial pressure ≥25 mmHg at rest assessed by right heart catheterization.Based on hemodynamic criteria, precapillary PH is characterized by a mean pulmonary capillary wedge pressure ≤15 mmHg as opposed to the postcapillary PH by >15 mmHg. Postcapillary PH is one of the most common forms of PH, often caused by left ventricular dysfunction and heart failure.In this chapter, we describe protocols for creating a large animal model of postcapillary PH. It is induced by open chest surgery (lateral thoracotomy) to band the pulmonary veins. The model is characterized by low mortality, relatively easy surgical procedure with well reproducible results, and pulmonary and cardiac remodeling at the structural, functional, and molecular levels. The presence of right ventricular (RV) remodeling is of significant importance since right heart failure is the main cause of death in patients suffering from PH. One of the advantages of the model described in this chapter is that both adaptive and maladaptive forms of RV remodeling can be observed during the progression of the disease. This can help understand the progressive pathophysiology of RV failure in humans. Besides the description of the model, a detailed guidance of the RV functional assessment in pigs for both invasive (heart catheterization) and noninvasive (echocardiography) approaches is provided.

Left Ventricular Unloading Using an Impella CP Improves Coronary Flow and Infarct Zone Perfusion in Ischemic Heart Failure.

BACKGROUND: Delivering therapeutic materials, like stem cells or gene vectors, to the myocardium is difficult in the setting of ischemic heart failure because of decreased coronary flow and impaired microvascular perfusion (MP). The aim of this study was to determine if mechanical left ventricular (LV) unloading with the Impella increases coronary flow and MP in a subacute myocardial infarction. METHODS AND RESULTS: Anterior transmural myocardial infarction (infarct size, 26.0±3.4%) was induced in Yorkshire pigs. At 2 weeks after myocardial infarction, 6 animals underwent mechanical LV unloading by Impella, whereas 4 animals underwent pharmacological LV unloading using sodium nitroprusside for 2 hours. LV unloading with Impella significantly reduced end-diastolic volume (-16±11mL, P=0.02) and end-diastolic pressure (EDP; -32±23 mm Hg, P=0.03), resulting in a significant decrease in LV end-diastolic wall stress (EDWS) (infarct: 71.6±14.7 to 43.3±10.8 kdynes/cm2 [P=0.02]; remote: 66.6±20.9 to 40.6±13.3 kdynes/cm2 [P=0.02]). Coronary flow increased immediately and remained elevated after 2 hours in Impella-treated pigs. Compared with the baseline, MP measured by fluorescent microspheres significantly increased within the infarct zone (109±81%, P=0.003), but not in the remote zone. Although sodium nitroprusside effectively reduced LV-EDWS, 2 (50%) of sodium nitroprusside-treated pigs developed profound systemic hypotension. A significant correlation was observed between the infarct MP and EDWS (r2=0.43, P=0.03), suggesting an important role of EDWS in regulating MP during LV unloading in the infarcted myocardium. CONCLUSIONS: LV unloading using an Impella decreased EDWS and increased infarct MP without hemodynamic decompensation. Mechanical LV unloading is a novel and efficient approach to increase infarct MP in patients with subacute myocardial infarction.