Translational large animal model of hibernating myocardium: characterization by serial multimodal imaging.

Nonrevascularizable coronary artery disease is a frequent cause of hibernating myocardium leading to heart failure (HF). Currently, there is a paucity of therapeutic options for patients with this condition. There is a lack of animal models resembling clinical features of hibernating myocardium. Here we present a large animal model of hibernating myocardium characterized by serial multimodality imaging. Yucatan minipigs underwent a surgical casein ameroid implant around the proximal left anterior descending coronary artery (LAD), resulting in a progressive obstruction of the vessel. Pigs underwent serial multimodality imaging including invasive coronary angiography, cardiac magnetic resonance (CMR), and hybrid 18F-Fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT). A total of 43 pigs were operated on and were followed for 120 ± 37 days with monthly multimodality imaging. 24 pigs (56%) died during the follow-up. Severe LAD luminal stenosis was documented in all survivors. In the group of 19 long-term survivors, 17 (90%) developed left ventricular systolic dysfunction [median LVEF of 35% (IQR 32.5-40.5%)]. In 17/17, at-risk territory was viable on CMR and 14 showed an increased glucose uptake in the at-risk myocardium on 18FDG-PET/CT. The present pig model resembles most of the human hibernated myocardium characteristics and associated heart failure (systolic dysfunction, viable myocardium, and metabolic switch to glucose). This human-like model might be used to test novel interventions for nonrevascularizable coronary artery disease and ischemia heart failure as a previous stage to clinical trials.

The mKATP Channels and protein-kinase C Are Involved in the Cardioprotective Effects of Genistein on Estrogen-Deficient Rat Hearts Exposed to Ischemia/Reperfusion: Energetic Study.

Estrogenic deficiency is considered a risk of coronary disease in women. The phytoestrogen genistein could be a safe preventive strategy. The first aim of this work was to validate a model of cardiac stunning in which natural estrogenic deficiency rats, ie, adult young male (YM) and aged female (AgF), are compared with young female rats (YF). The second aim was to study whether the in vivo administration of genistein prevents the stunning in estrogenic deficiency rats. The third aim was to evaluate whether in our estrogenic deficiency model exists a synergy between genistein and estradiol. The fourth aim was to characterize the underlying mechanisms of genistein. Stunning was induced by ischemia/reperfusion (I/R) in isolated hearts inside a calorimeter. The left ventricular pressure (P) and total heat rate (Ht) were simultaneously measured, while diastolic contracture and muscle economy (P/Ht) were calculated. During R, P/Ht and P recovered less in AgF and YM than in YF rat hearts. Genistein through i.p. (GST-ip) improved P and P/Ht in AgF and YM, but not in YF. In YM, the cardioprotections of GST-ip and estradiol were synergistic. After ischemia, GST-ip increased SR Ca leak causing diastolic contracture. The GST-ip cardioprotection neither was affected by blockade of PI3K-Akt, NO synthases, or phosphatases, but it was sensitive to blockade of protein-kinase C and mKATP channels. Results suggest that (1) estrogenic deficiency worsens cardiac stunning, (2) GST-ip was more cardioprotective in estrogenic deficiency and synergistic with estradiol, and (3) cardioprotection of GST-ip depends on the protein-kinase C and mKATP channel pathway activation.

Chemical chaperones improve the functional recovery of stunned myocardium by attenuating the endoplasmic reticulum stress.

AIM: Myocardial ischaemia/reperfusion (I/R) produces structural and functional alterations depending on the duration of ischaemia. Brief ischaemia followed by reperfusion causes reversible contractile dysfunction (stunned heart) but long-lasting ischaemia followed by reperfusion can result in irreversible injury with cell death. Events during I/R can alter endoplasmic reticulum (ER) function leading to the accumulation of unfolded/misfolded proteins. The resulting ER stress induces activation of several signal transduction pathways, known as unfolded protein response (UPR). Experimental evidence shows that UPR contributes to cell death in irreversible I/R injury; however, there is still uncertainty for its occurrence in the stunned myocardium. This study investigated the ER stress response and its functional impact on the post-ischaemic cardiac performance of the stunned heart. METHODS: Perfused rat hearts were subjected to 20 minutes of ischaemia followed by 30 minutes of reperfusion. UPR markers were evaluated by qRT-PCR and western blot. Post-ischaemic mechanical recovery was measured in absence and presence of two chemical chaperones: tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA). RESULTS: Analysis of mRNA and protein levels of various ER stress effectors demonstrated that different UPR signalling cascades, involving both pro-survival and pro-apoptotic pathways, are activated. Inhibition of the UPR with chemical chaperones improved the post-ischaemic recovery of cardiac mechanical function without affecting the I/R-induced increase in oxidative stress. CONCLUSION: Our results suggest that prevention of ER stress by chemical chaperones could be a therapeutic tool to limit deterioration of the contractile function in clinical settings in which the phenomenon of myocardial stunning is present.

Prevalence and Localization of Hibernating Myocardium Among Patients with Left Ventricular Dysfunction.

OBJECTIVE: This study evaluated how much of the myocardium was hibernating in patients with left ventricle dysfunction and/or comorbidities who planned to undergo either surgical or interventional revascularization. Furthermore, this study also identified which irrigation areas of the coronary arteries presented more scar and hibernating tissue. METHODS: At rest, Tc-99m MIBI SPECT and cardiac F-18 FDG PET/CT images collected between March 2009 and September 2016 from 65 patients (55 men, 10 women, mean age 64±12) were retrospectively analyzed in order to evaluate myocardial viability. The areas with perfusion defects that were considered metabolic were accepted as hibernating myocardium, whereas areas with perfusion defects that were considered non-metabolic were accepted as scar tissue. RESULTS: Perfusion defects were observed in 26% of myocardium, on average 48% were associated with hibernation whereas other 52% were scar tissue. In the remaining Tc-99m MIBI images, perfusion defects were observed in the following areas in the left anterior descending artery (LAD; 31%), in the right coronary artery (RCA; 23%) and in the Left Circumflex Artery (LCx; 19%) irrigation areas. Hibernation areas were localized within the LAD (46%), LCx (54%), and RCA (64%) irrigation areas. Scar tissue was also localized within the LAD (54%), LCx (46%), and RCA (36%) irrigation areas. CONCLUSION: Perfusion defects are thought to be the result of half hibernating tissue and half scar tissue. The majority of perfusion defects was observed in the LAD irrigation area, whereas hibernation was most often observed in the RCA irrigation area. The scar tissue development was more common in the LAD irrigation zone.

Identification of new biophysical markers for pathological ventricular remodelling in tachycardia-induced dilated cardiomyopathy.

Our aim was to identify biophysical biomarkers of ventricular remodelling in tachycardia-induced dilated cardiomyopathy (DCM). Our study includes healthy controls (N = 7) and DCM pigs (N = 10). Molecular analysis showed global myocardial metabolic abnormalities, some of them related to myocardial hibernation in failing hearts, supporting the translationality of our model to study cardiac remodelling in dilated cardiomyopathy. Histological analysis showed unorganized and agglomerated collagen accumulation in the dilated ventricles and a higher percentage of fibrosis in the right (RV) than in the left (LV) ventricle (P = .016). The Fourier Transform Infrared Spectroscopy (FTIR) 1st and 2nd indicators, which are markers of the myofiber/collagen ratio, were reduced in dilated hearts, with the 1st indicator reduced by 45% and 53% in the RV and LV, respectively, and the 2nd indicator reduced by 25% in the RV. The 3rd FTIR indicator, a marker of the carbohydrate/lipid ratio, was up-regulated in the right and left dilated ventricles but to a greater extent in the RV (2.60-fold vs 1.61-fold, P = .049). Differential scanning calorimetry (DSC) showed a depression of the freezable water melting point in DCM ventricles - indicating structural changes in the tissue architecture - and lower protein stability. Our results suggest that the 1st, 2nd and 3rd FTIR indicators are useful markers of cardiac remodelling. Moreover, the 2nd and 3rd FITR indicators, which are altered to a greater extent in the right ventricle, are associated with greater fibrosis.

Baicalein Rescues Delayed Cooling via Preservation of Akt Activation and Akt-Mediated Phospholamban Phosphorylation.

Cooling reduces the ischemia/reperfusion (I/R) injury seen in sudden cardiac arrest (SCA) by decreasing the burst of reactive oxygen species (ROS). Its cardioprotection is diminished when delay in reaching the target temperature occurs. Baicalein, a flavonoid derived from the root of ScutellariabaicalensisGeorgi, possesses antioxidant properties. Therefore, we hypothesized that baicalein can rescue cooling cardioprotection when cooling is delayed. Two murine cardiomyocyte models, an I/R model (90 min ischemia/3 h reperfusion) and stunning model (30 min ischemia/90 min reperfusion), were used to assess cell survival and contractility, respectively. Cooling (32 °C) was initiated either during ischemia or during reperfusion. Cell viability and ROS generation were measured. Cell contractility was evaluated by real-time phase-contrast imaging. Our results showed that cooling reduced cell death and ROS generation, and this effect was diminished when cooling was delayed. Baicalein (25 µM), given either at the start of reperfusion or start of cooling, resulted in a comparable reduction of cell death and ROS production. Baicalein improved phospholamban phosphorylation, contractility recovery, and cell survival. These effects were Akt-dependent. In addition, no synergistic effect was observed with the combined treatments of cooling and baicalein. Our data suggest that baicalein may serve as a novel adjunct therapeutic strategy for SCA resuscitation.

Mitochondrial Bioenergetics During Ischemia and Reperfusion.

During ischemia and reperfusion (I/R) mitochondria suffer a deficiency to supply the cardiomyocyte with chemical energy, but also contribute to the cytosolic ionic alterations especially of Ca2+. Their free calcium concentration ([Ca2+]m) mainly depends on mitochondrial entrance through the uniporter (UCam) and extrusion in exchange with Na+ (mNCX) driven by the electrochemical gradient (ΔΨm). Cardiac energetic is frequently estimated by the oxygen consumption, which determines metabolism coupled to ATP production and to the maintaining of ΔΨm. Nevertheless, a better estimation of heart energy consumption is the total heat release associated to ATP hydrolysis, metabolism, and binding reactions, which is measurable either in the presence or the absence of oxygenation or perfusion. Consequently, a mechano-calorimetrical approach on isolated hearts gives a tool to evaluate muscle economy. The mitochondrial role during I/R depends on the injury degree. We investigated the role of the mitochondrial Ca2+ transporters in the energetic of hearts stunned by a model of no-flow I/R in rat hearts. This chapter explores an integrated view of previous and new results which give evidences to the mitochondrial role in cardiac stunning by ischemia o hypoxia, and the influence of thyroid alterations and cardioprotective strategies, such as cardioplegic solutions (high K-low Ca, pyruvate) and the phytoestrogen genistein in both sex. Rat ventricles were perfused in a flow-calorimeter at either 30 °C or 37 °C to continuously measure the left ventricular pressure (LVP) and total heat rate (Ht). A pharmacological treatment was done before exposing to no-flow I and R. The post-ischemic contractile (PICR as %) and energetical (Ht) recovery and muscle economy (Eco: P/Ht) were determined during stunning. The functional interaction between mitochondria (Mit) and sarcoplasmic reticulum (SR) was evaluated with selective mitochondrial inhibitors in hearts reperfused with Krebs-10 mM caffeine-36 mM Na+. The caffeine induced contracture (CIC) was due to SR Ca2+ release, while relaxation mainly depends on mitochondrial Ca2+ uptake since neither SL-NCX nor SERCA are functional under this media. The ratio of area-under-curves over ischemic values (AUC-ΔHt/AUC-ΔLVP) estimates the energetical consumption (EC) to maintain CIC. Relaxation of CIC was accelerated by inhibition of mNCX or by adding the aerobic substrate pyruvate, while both increased EC. Contrarily, relaxation was slowed by cardioplegia (high K-low Ca Krebs) and by inhibition of UCam. Thus, Mit regulate the cytosolic [Ca2+] and SR Ca2+ content. Both, hyperthyroidism (HpT) and hypothyroidism (HypoT) reduced the peak of CIC but increased EC, in spite of improving PICR. Both, CIC and PICR in HpT were also sensitive to inhibition of mNCX or UCam, suggesting that Mit contribute to regulate the SR store and Ca2+ release. The interaction between mitochondria and SR and the energetic consequences were also analyzed for the effects of genistein in hearts exposed to I/R, and for the hypoxia/reoxygenation process. Our results give evidence about the mitochondrial regulation of both PICR and energetic consumption during stunning, through the Ca2+ movement.

Free breathing three-dimensional late gadolinium enhancement cardiovascular magnetic resonance using outer volume suppressed projection navigators.

PURPOSE: To develop a three-dimensional, free-breathing, late gadolinium enhancement (3D FB-LGE) cardiovascular magnetic resonance (CMR) technique, and to compare it with clinically used two-dimensional breath-hold LGE (2D BH-LGE). METHODS: The proposed 3D FB-LGE method consisted of inversion preparation, inversion delay, fat saturation, outer volume suppression, one-dimensional projection navigators, and a segmented stack of spirals acquisition. The 3D FB-LGE and 2D BH-LGE scans were performed on 29 cardiac patients. Qualitative analysis and quantitative analysis (in patients with scar) were performed. RESULTS: No significant differences were noted between the 3D FB-LGE and 2D BH-LGE data sets in terms of overall image quality score (2D: 4.69 ± 0.60 versus 3D: 4.55 ± 0.51, P = 0.46) and image artifact score (2D: 1.10 ± 0.31 versus 3D: 1.17 ± 0.38; P = 0.63). The average difference in fractional scar volume between the 3D and 2D methods was 1.9% (n = 5). Acquisition time was significantly shorter for the 3D FB-LGE over 2D BH-LGE by a factor of 2.83 ± 0.77 (P < 0.0001). CONCLUSIONS: The 3D FB-LGE is a viable option for patients, particularly in acute settings or in patients who are unable to comply with breath-hold instructions. Magn Reson Med 77:1533-1543, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Taxonomy of segmental myocardial systolic dysfunction.

The terms used to describe different states of myocardial health and disease are poorly defined. Imprecision and inconsistency in nomenclature can lead to difficulty in interpreting and applying trial outcomes to clinical practice. In particular, the terms 'viable' and 'hibernating' are commonly applied interchangeably and incorrectly to myocardium that exhibits chronic contractile dysfunction in patients with ischaemic heart disease. The range of inherent differences amongst imaging modalities used to define myocardial health and disease add further challenges to consistent definitions. The results of several large trials have led to renewed discussion about the classification of dysfunctional myocardial segments. This article aims to describe the diverse myocardial pathologies that may affect the myocardium in ischaemic heart disease and cardiomyopathy, and how they may be assessed with non-invasive imaging techniques in order to provide a taxonomy of myocardial dysfunction.

Clinical evaluation of three-dimensional late enhancement MRI.

PURPOSE: To assess the diagnostic value of three-dimensional late enhancement (3D-LGE) for the detection of myocardial necrosis in a routine clinical setting. 3D-LGE has been proposed as a novel magnetic resonance (MR) technique for the accurate detection of myocardial scar in both the ventricles and atria. Its performance in clinical practice has been poorly examined. MATERIALS AND METHODS: Fifty-seven patients referred for cardiac MR examination including scar imaging were prospectively enrolled. Gadolinium enhanced single breathhold 3D T1-weighted gradient-echo inversion recovery sequence and a conventional 2D-LGE sequence were performed using a 1.5 Tesla clinical MR imaging system. The presence, pattern and transmurality of LGE, diagnostic accuracy and level of diagnostic confidence as well as image quality (median quality, mean LGE signal intensity, sharpness, virtual scan time) were graded on a 4-point scale. RESULTS: Interpretable images were obtained in 52/57 2D-LGE and in 47/57 3D high-resolution exams. LGE was detected in 10 patients with ischemic pattern, 9 with nonischemic pattern, while it was absent in 28, resulting in a total of 47 complete datasets. The detection of global and segmental LGE as well as its transmural extent were similar for both techniques (P = 0.65, P = 0.305, and P = 0.15, respectively). Image quality (median quality, LGE/ myocardial and LGE/ blood pool sharpness) was similar for both techniques (P = 0.740, P = 0.34, and P = 1.00, respectively), but LGE signal intensity was higher with 2D (P = 0.020). CONCLUSION: 3D-LGE diagnostic and quality scores were comparable to 2D-LGE in a routine clinical setting. Further technical refinement is required for 3D LGE to offer a reliable alternative for high quality scar imaging. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;45:1675-1683.

Relationship between QRS score and microvascular obstruction after acute anterior myocardial infarction.

BACKGROUND: The QRS score on electrocardiogram (ECG) in patients with myocardial infarction (MI) reportedly reflects the severity of myocardial damage. The presence of microvascular obstruction (MO) assessed by cardiac magnetic resonance (CMR) imaging is associated with irreversible myocardial damage. MO assessed by CMR is known to be a predictor for adverse clinical outcome after ST-elevation MI. The aim of the present study was to examine the relationship between QRS score and MO in acute anterior MI patients. METHODS: Sixty-two patients with first acute anterior MI who successfully underwent primary percutaneous coronary intervention (PCI) were enrolled. The QRS score after PCI on admission ECG was calculated by a Selvester-Wagner QRS scoring system. CMR imaging was performed at 11.4±3.9 days after MI. MO was defined as delayed enhancement with contrast-devoid core. Patients were divided into two groups as follows: 37 patients who showed MO (MO group) and 25 patients who did not show it (non-MO group). RESULTS: The QRS score was significantly greater in the MO group than in the non-MO group. The QRS score significantly correlated with MO volume (r=0.418, p=0.010). Multivariate analysis showed that the QRS score (odds ratio 1.362, 95% CI: 1.038-1.951, p=0.024) and the peak creatine kinase levels (odds ratio 1.001, 95% CI: 1.000-1.002, p<0.001) were independent predictors for MO. CONCLUSIONS: Our results indicate that the QRS score derived from simple and widely available ECG may be a useful parameter for assuring the presence of MO.

Sex differences in the mechano-energetic effects of genistein on stunned rat and guinea pig hearts.

Although the phytoestrogen genistein (Gen) is considered protective in cardiovascular diseases, its direct effects on stunned hearts after transient ischemia-reperfusion (I/R) are unknown. This report studied the effects of 20 µmol/L Gen on the mechano-calorimetric behaviour during I/R of rat and guinea pig hearts to evaluate the energetics of Ca(2+) homeostasis. Isolated beating hearts were perfused with control Krebs solution inside a calorimeter with or without perfusion of Gen before a transient period of I/R. Left ventricular pressure development (P) and total heat rate (Ht) were continuously measured. At 37°C, Gen did not change post-ischemic contractile recovery (PICR), but it increased the relaxation rate. However, PICR was reduced in hearts of male rats and guinea pigs at 30°C. Total muscle economy (P/Ht) showed the same behaviour as P at each temperature. Inhibition of phosphatases with orthovanadate during Gen perfusion prevented a decrease in PICR in male rat hearts, suggesting that this effect is due to tyrosine kinase inhibition. Reperfusing ischemic hearts with 10 mmol/L caffeine-36 mmol/L Na(+)-Krebs induced contracture dependent on the sarcoreticular Ca(2+) content. Contracture relaxation depends on mitochondrial Ca(2+) uptake and Gen reduced the relaxation rate. Moreover, Gen prevented the increase in Rhod-2 fluorescence (free [Ca(2+)]m) of rat cardiomyocytes. In guinea pig hearts, Gen maintained ischemic preconditioning, but was reduced by 5-hydroxydecanoate, suggesting the participation of mitochondrial adenosine triphosphate (ATP)-dependent K channels. Results suggest that Gen acts on several mechanisms that regulate myocardial calcium homeostasis and energetics during I/R, which differ in a temperature- and sex-dependent manner.

Subarachnoid Hemorrhage-Triggered Acute Hypotension Is Associated with Left Ventricular Cardiomyocyte Apoptosis in a Rat Model.

Whether hypotension that occurs due to neurogenic stunned myocardium after subarachnoid hemorrhage (SAH) is associated with cardiomyocyte apoptotic cell death remains unknown. In this study, 18 male rats were subjected to sham or the endovascular perforation model of SAH surgery. Based on the mean arterial pressure (MAP) after SAH, rats were separated into SAH with hypotension (SAH hypotension) or SAH with blood pressure preservation (SAH BP preservation) groups. All animals were euthanized 2 h after the surgical procedure. Hearts were removed and separated transversely into base and apex parts, then Western blot analyses and immunohistochemistry were performed only in the apex part. One rat died as a result of severe SAH and two rats with mild SAH were excluded. We analyzed data from 15 rats that were divided into three groups: sham, SAH hypotension, and SAH BP preservation (n = 5, each). There was a significantly higher cleaved caspase-3/caspase-3 ratio in the SAH hypotension group compared with sham and the SAH BP preservation group. Cardiomyocyte apoptosis was demonstrated in the SAH rats. This is the first experimental report that describes SAH-induced neurogenic stunned myocardium with ensuing hypotension may result from the acute apoptotic cardiomyocyte cell death in the left ventricle.

Comparative Efficacy of Intracoronary Allogeneic Mesenchymal Stem Cells and Cardiosphere-Derived Cells in Swine with Hibernating Myocardium.

RATIONALE: Allogeneic bone marrow-derived mesenchymal stem cells (MSCs) and cardiosphere-derived cells (CDCs) have each entered clinical trials, but a direct comparison of these cell types has not been performed in a large animal model of hibernating myocardium. OBJECTIVE: Using completely blinded methodology, we compared the efficacy of global intracoronary allogeneic MSCs (icMSCs, ≈35×10(6)) and CDCs (icCDCs, ≈35×10(6)) versus vehicle in cyclosporine-immunosuppressed swine with a chronic left anterior descending coronary artery stenosis (n=26). METHODS AND RESULTS: Studies began 3 months after instrumentation when wall thickening was reduced (left anterior descending coronary artery % wall thickening [mean±SD], 38±11% versus 83±26% in remote; P<0.01) and similar among groups. Four weeks after treatment, left anterior descending coronary artery % wall thickening increased similarly after icCDCs and icMSCs, whereas it remained depressed in vehicle-treated controls (icMSCs, 51±13%; icCDCs, 51±17%; vehicle, 34±3%, treatments P<0.05 versus vehicle). There was no change in myocardial perfusion. Both icMSCs and icCDCs increased left anterior descending coronary artery myocyte nuclear density (icMSCs, 1601±279 nuclei/mm(2); icCDCs, 1569±294 nuclei/mm(2); vehicle, 973±181 nuclei/mm(2); treatments P<0.05 versus vehicle) and reduced myocyte diameter (icMSCs, 16.4±1.5 µm; icCDCs, 16.8±1.2 µm; vehicle, 20.2±3.7 µm; treatments P<0.05 versus vehicle) to the same extent. Similar changes in myocyte nuclear density and diameter were observed in the remote region of cell-treated animals. Cell fate analysis using Y-chromosome fluorescent in situ hybridization demonstrated rare cells from sex-mismatched donors. CONCLUSIONS: Allogeneic icMSCs and icCDCs exhibit comparable therapeutic efficacy in a large animal model of hibernating myocardium. Both cell types produced equivalent increases in regional function and stimulated myocyte regeneration in ischemic and remote myocardium. The activation of endogenous myocyte proliferation and regression of myocyte cellular hypertrophy support a common mechanism of cardiac repair.

Viability assessment after conventional coronary angiography using a novel cardiovascular interventional therapeutic CT system: Comparison with gross morphology in a subacute infarct swine model.

BACKGROUND: Given the lack of promptness and inevitable use of additional contrast agents, the myocardial viability imaging procedures have not been used widely for determining the need to performing revascularization. OBJECTIVE: This study is aimed to evaluate the feasibility of myocardial viability assessment, consecutively with diagnostic invasive coronary angiography (ICA) without use of additional contrast agent, using a novel hybrid system comprising ICA and multislice CT (MSCT). METHODS: In all, 14 Yucatan miniature swine models (female; age, 3 months; weight, 28-30 kg) were subjected to ICA followed by balloon occlusion (90 minutes) and reperfusion of the left anterior descending coronary artery. Two weeks after induction of myocardial infarction, delayed hyperenhancement (DHE) images were obtained, using a novel combined machine comprising ICA and 320-channel MSCT scanner (Aquilion ONE, Toshiba), after 2, 5, 7, 10, 15, and 20 minutes after conventional ICA. The heart was sliced in 10-mm consecutive sections in the short-axis plane and was embedded in a solution of 1% triphenyltetrazolium chloride (TTC). Infarct size was determined as TTC-negative areas as a percentage of total left ventricular area. On MSCT images, infarct size per slice was calculated by dividing the DHE area by the total slice area (%) and compared with histochemical analyses. RESULTS: Serial MSCT scans revealed a peak CT attenuation of the infarct area (222.5 ± 36.5 Hounsfield units) with a maximum mean difference in CT attenuation between the infarct areas and normal myocardium of at 2 minutes after contrast injection (106.4; P for difference = 0.002). Furthermore, the percentage difference of infarct size by MSCT vs histopathologic specimen was significantly lower at 2 (8.5% ± 1.8%) and 5 minutes (9.5% ± 1.9%) than those after 7 minutes. Direct comparisons of slice-matched DHE area by MSCT demonstrated excellent correlation with TTC-derived infarct size (r = 0.952; P < .001). Bland-Altman plots of the differences between DHE by MSCT and TTC-derived infarct measurements plotted against their means showed good agreement between the 2 methods. CONCLUSION: The feasibility of myocardial viability assessment by DHE using MSCT after conventional ICA was proven in experimental models, and the optimal viability images were obtained after 2 to 5 minutes after the final intracoronary injection of contrast agent for conventional ICA.

Revascularization of chronic hibernating myocardium stimulates myocyte proliferation and partially reverses chronic adaptations to ischemia.

BACKGROUND: The time course and extent of recovery after revascularization of viable dysfunctional myocardium are variable. Although fibrosis is a major determinant, myocyte structural and molecular remodeling may also play important roles. OBJECTIVES: This study sought to determine whether persistent myocyte loss and/or irreversibility of protein changes that develop in hibernating myocardium have an impact on functional recovery in the absence of infarction. METHODS: Swine implanted with a chronic left anterior descending artery (LAD) stenosis to produce hibernating myocardium underwent percutaneous revascularization, with serial functional recovery evaluated for 1 month (n = 12). Myocardial tissue was evaluated to assess myocyte size, nuclear density, and proliferation indexes in comparison with those of normal animals and nonrevascularized controls. Proteomic analysis by 2-dimensional differential in-gel electrophoresis was used to determine the reversibility of molecular adaptations of hibernating myocytes. RESULTS: At 3 months, physiological features of hibernating myocardium were confirmed, with depressed LAD wall thickening and no significant infarction. Revascularization normalized LAD flow reserve, with no immediate change in LAD wall thickening. Regional LAD wall thickening slowly improved but remained depressed 1 month post-percutaneous coronary intervention. Surprisingly, revascularization was associated with histological evidence of myocytes re-entering the growth phase of the cell cycle and increases in the number of c-Kit(+) cells. Myocyte nuclear density returned to normal, whereas regional myocyte hypertrophy regressed. Proteomic analysis demonstrated heterogeneous effects of revascularization. Up-regulated stress and cytoskeletal proteins normalized, whereas reduced contractile and metabolic proteins persisted. CONCLUSIONS: Delayed recovery of hibernating myocardium in the absence of scar may reflect persistent reductions in the amounts of contractile and metabolic proteins. Although revascularization appeared to stimulate myocyte proliferation, the persistence of small immature myocytes may have contributed to delayed functional recovery.

Super-resolution reconstruction of late gadolinium-enhanced MRI for improved myocardial scar assessment.

PURPOSE: To develop and validate a method for improving image resolution of late gadolinium-enhanced (LGE) magnetic resonance imaging (MRI) for accurate assessment of myocardial scar. MATERIALS AND METHODS: In a cohort of 37 postinfarction patients, LGE was performed prior to ventricular tachycardia catheter ablation therapy at 1.5T. A super-resolution reconstruction (SRR) technique was applied to the three anisotropic views: short-axis (SA), two-chamber, and four-chamber, to reconstruct a single isotropic volume. For compensation of the interscan heart motion, a joint localized gradient-correlation-based scheme was developed. Scar was identified as either core or gray zone in both the SRR and original SA volumes, and evaluated based on the clinically established bipolar voltage range of the in vivo electroanatomical voltage mapping (EAVM). RESULTS: Compared to the SA volume, the SRR method resulted in significantly (P < 0.05) reduced myocardial scar gray zone sizes (10.5 ± 8.8 g vs. 9.2 ± 8.1 g) and improved agreement of the bipolar voltage range of scar gray zone (0.99 ± 0.65 mV vs. 1.46 ± 1.15 mV). CONCLUSION: We propose an SRR method to automatically reconstruct a high-quality isotropic LGE volume from three orthogonal views. Analysis of the in vivo EAVM demonstrated improved myocardial scar assessment from the SRR volume compared with the SA LGE alone.

Chronic hibernating myocardium in sheep can occur without degenerating events and is reversed after revascularization.

INTRODUCTION: Our goal was to show that blunting of myocardial flow reserve is mainly involved in adaptive chronic myocardial hibernation without apparent cardiomyocyte degeneration. METHODS AND RESULTS: Sheep chronically instrumented with critical multivessel stenosis and/or percutaneous transluminal coronary angioplasty (PTCA)-induced revascularization were allowed to run and feed in the open for 2 and 5 months, respectively. Regional myocardial blood flow (MBF) with colored microspheres, regional and global left ventricular function and dimensions (2D echocardiography), and myocardial structure were studied. In sheep with a critical stenosis, a progressive increase in left ventricular end-diastolic and end-systolic cavity area and a decrease in fractional area change were found. Fraction of wall thickness decreased in all left ventricular wall segments. MBF was slightly but not significantly decreased at rest at 2 months. Morphological quantification revealed a rather small but significant increase in diffusely distributed connective tissue, cardiomyocyte hypertrophy, and presence of viable myocardium of which almost 30 % of the myocytes showed depletion of sarcomeres and accumulation of glycogen. The extent of myolysis in the transmural layer correlated with the degree of left ventricular dilation. Structural degeneration of cardiomyocytes was not observed. Balloon dilatation (PTCA) of one of the coronary artery stenoses at 10 weeks revealed recovery of fraction of wall thickness and near normalization of global subcellular structure at 20 weeks. CONCLUSION: These data indicate that chronic reduction of coronary reserve by itself can induce ischemic cardiomyopathy characterized by left ventricular dilatation, depressed regional and global function, adaptive chronic myocardial hibernation, reactive fibrosis and cardiomyocyte hypertrophy in the absence of obvious degenerative phenomena. SUMMARY: Reduction of myocardial flow reserve due to chronic coronary artery stenosis in sheep induces adaptive myocardial hibernation without involvement of degenerative phenomena.

Regional mapping of myocardial hibernation phenotype in idiopathic end-stage dilated cardiomyopathy.

Myocardial hibernation (MH) is a well-known feature of human ischaemic cardiomyopathy (ICM), whereas its presence in human idiopathic dilated cardiomyopathy (DCM) is still controversial. We investigated the histological and molecular features of MH in left ventricle (LV) regions of failing DCM or ICM hearts. We examined failing hearts from DCM (n = 11; 41.9 ± 5.45 years; left ventricle-ejection fraction (LV-EF), 18 ± 3.16%) and ICM patients (n = 12; 58.08 ± 1.7 years; LVEF, 21.5 ± 6.08%) undergoing cardiac transplantation, and normal donor hearts (N, n = 8). LV inter-ventricular septum (IVS) and antero-lateral free wall (FW) were transmurally (i.e. sub-epicardial, mesocardial and sub-endocardial layers) analysed. LV glycogen content was shown to be increased in both DCM and ICM as compared with N hearts (P < 0.001), with a U-shaped transmural distribution (lower values in mesocardium). Capillary density was homogenously reduced in both DCM and ICM as compared with N (P < 0.05 versus N), with a lower decrease independent of the extent of fibrosis in sub-endocardial and sub-epicardial layers of DCM as compared with ICM. HIF1-α and nestin, recognized ischaemic molecular hallmarks, were similarly expressed in DCM-LV and ICM-LV myocardium. The proteomic profile was overlapping by ~50% in DCM and ICM groups. Morphological and molecular features of MH were detected in end-stage ICM as well as in end-stage DCM LV, despite epicardial coronary artery patency and lower fibrosis in DCM hearts. Unravelling the presence of MH in the absence of coronary stenosis may be helpful to design a novel approach in the clinical management of DCM.