Coronary Microembolization-induced Heart Failure Research Articles

Intravenous Infusion of the β3-Adrenergic Receptor Antagonist APD418 Improves Left Ventricular Systolic Function in Dogs With Systolic Heart Failure

BackgroundUnlike β1- and β2-adrenergic receptors (ARs), β3-AR stimulation inhibits cardiac contractility and relaxation. In the failing left ventricular (LV) myocardium, β3-ARs are upregulated, and can be maladaptive in the setting of decompensation by contributing to LV dysfunction. This study examined the effects of intravenous infusions of the β3-AR antagonist APD418 on cardiovascular function and safety in dogs with systolic heart failure (HF). Methods and ResultsThree separate studies were performed in 21 dogs with coronary microembolization-induced HF (LV ejection fraction [LVEF] of approximately 35%). Studies 1 and 2 (n = 7 dogs each) were APD418 dose escalation studies (dosing range, 0.35–15.00 mg/kg/h) designed to identify an effective dose of APD418 to be used in study 3. Study 3, the sustained efficacy study, (n = 7 dogs) was a 6-hour constant intravenous infusion of APD418 at a dose of 4.224 mg/kg (0.70 mg/kg/h) measuring key hemodynamic endpoints (e.g., EF, cardiac output, the time velocity integral of the mitral inflow velocity waveform representing early filling to time-velocity integral representing left atrial contraction [Ei/Ai]). Studies 1 and 2 showed a dose-dependent increase of LVEF and Ei/Ai, the latter being an index of LV diastolic function. In study 3, infusion of APD418 over 6 hours increased LVEF from 31 ± 1% to 38 ± 1% (P < .05) and increased Ei/Ai from 3.4 ± 0.4 to 4.9 ± 0.5 (P < .05). Vehicle had no effect on the LVEF or Ei/Ai. In study 3, APD418 had no significant effects on the HR or the systemic blood pressure. ConclusionsIntravenous infusions of APD418 in dogs with systolic HF elicit significant positive inotropic and lusitropic effects. These findings support the development of APD418 for the in-hospital treatment of patients with an acute exacerbation of chronic HF.

Effects of Angiotensin-Neprilysin Inhibition in Canines with Experimentally Induced Cardiorenal Syndrome

BackgroundSacubitril/valsartan (Sac/Val), a combined angiotensin-II receptor blocker (Val) and neprilysin inhibitor (Sac) in a 1:1 molar ratio, was shown to decrease the risk of cardiovascular death or heart failure (HF) hospitalization in patients with HF and reduced left ventricular (LV) ejection fraction. This study examined the effects of Sac/Val on LV structure, function, and bioenergetics, and on biomarkers of kidney injury and kidney function in dogs with experimental cardiorenal syndrome. Methods and ResultsFourteen dogs with cardiorenal syndrome (coronary microembolization-induced HF and renal dysfunction) were randomized to 3 months Sac/Val therapy (100 mg once daily, n = 7) or no therapy (control, n = 7). LV ejection fraction and troponin-I, as well as biomarkers of kidney injury/function including serum creatinine and urinary kidney injury molecule-1 were measured before and at end of therapy and the change (treatment effect change) calculated. Mitochondrial function measures, including the maximum rate of adenosine triphosphate synthesis, were measured in isolated cardiomyocytes at end of therapy. In Sac/Val dogs, the change in ejection fraction increased compared with controls, 6.9 ± 1.4 vs 0.7 ± 0.6%, P < .002, whereas change in troponin I decreased, –0.16 ± 0.03 vs –0.03 ± 0.02 ng/mL, P < .001. Urinary change in kidney injury molecule 1 decreased in Sac/Val–treated dogs compared with controls, –17.2 ± 7.9 vs 7.7 ± 3.0 mg/mL, P < .007, whereas the change in serum creatinine was not significantly different. Treatment with Sac/Val increased adenosine triphosphate synthesis compared with controls, 3240 ± 121 vs 986 ± 84 RLU/µg protein, P < .05. ConclusionsIn dogs with cardiorenal syndrome, Sac/Val improves LV systolic function, improves mitochondrial function and decreases biomarkers of heart and kidney injury. The results offer mechanistic insights into the benefits of Sac/Val in HF with compromised renal function.

Effects of Intravenous Infusion of Vepoloxamer on Left Ventricular Function in Dogs with Advanced Heart Failure.

Vepoloxamer (VEPO), a rheologic agent, repairs damaged cell membranes, thus inhibiting unregulated Ca2+ entry into cardiomyocytes. This study examined the effects of i.v. infusion of VEPO on LV function in dogs with coronary microembolization-induced heart failure (HF) (LV ejection fraction, EF ~ 30%). Thirty-five HF dogs were studied. Study 1: 21 of 35 dogs were randomized to 2-h infusion of VEPO at dose of 450mg/kg (n = 7) or VEPO at 225mg/kg (n = 7) or normal saline (control, n = 7). Hemodynamics were measured at 2h, 24h, 1week, and 2weeks after infusion. Study 2: 14 HF dogs were randomized to 2-h infusions of VEPO (450mg/kg, n = 7) or normal saline (control, n = 7). Each dog received 2 infusions of VEPO or saline (pulsed therapy) 3weeks apart and hemodynamics measured at 24h, and 1, 2, and 3weeks after each infusion. In both studies, the change between pre-infusion measures and measures at other time points (treatment effect, Δ) was calculated. Study 1: compared to pre-infusion, high dose VEPO increased LVEF by 11 ± 2% at 2h, 8 ± 2% at 24h (p < 0.05), 8 ± 2% at 1week (p < 0.05), and 4 ± 2% at 2weeks. LV EF also increased with low-dose VEPO but not with saline. Study 2: VEPO but not saline significantly increased LVEF by 6.0 ± 0.7% at 2h (p< 0.05); 7.0 ± 0.7%% at 1week (p< 0.05); 1.0 ± 0.6% at 3weeks; 6.0 ± 1.3% at 4weeks (p< 0.05); and 5.9 ± 1.3% at 6weeks (p< 0.05). Intravenous VEPO improves LV function for at least 1week after infusion. The benefits can be extended with pulsed VEPO therapy. The results support development of VEPO for treating patients with acute on chronic HF.

Galectin-3 Expression in the Left Ventricular Interstitium of Dogs with Chronic Heart Failure: Association with Interstitial Fibrosis

Purpose Accumulation of collagen in the cardiac interstitium termed “reactive interstitial fibrosis (RIF)” occurs in heart failure (HF) with reduced ejection fraction (HFrEF) as well as in HF with preserved EF (HFpEF). This maladaptation leads to increased myocardial stiffness that negatively impacts ventricular filling. RIF also results in poor oxygen diffusion between capillaries and cardiomyocytes leading to cardiomyocyte hypoxia that promotes cellular contractile dysfunction and triggers programmed cell death. The protein galectin-3 (GAL-3) is a member of the lectin family. Increased expression of GAL-3 is implicated in the development of fibrosis in multiple organs including the heart. Elevated levels of GAL-3 are significantly associated with higher risk of death in patients with HF. In this study, we examined whether increased expression of GAL-3 occurs in the LV interstitium of dogs with chronic HF that also manifest increased levels of RIF. Methods Studies were performed in LV tissue obtained from 7 normal (NL) dogs and 7 dogs with coronary microembolization-induced HF. Frozen LV sections, 6 µm in thickness, were used for fluorescence immunostaining with antibodies against myosin heavy chain and GAL-3. DAPI (4′, 6-diamidino-2-phenylindole) was used to stain nuclei. Confocal images of stained sections were obtained with an Olympus Fluoview FV1000 laser scanning biological microscope. From each section, 4-6 fields, each ∼10 mm2, were randomly selected for laser scanning and subsequently used to calculate the percent area occupied by GAL-3 (%aGAL-3) from each field. The percent area occupied by RIF (%aRIF) was also calculated using frozen sections stained with fluorescein-labeled peanut agglutinin. Results In NL dogs, the %aRIF was 3.70 ± 0.07 and %aGAL-3 was 2.40 ± 0.45. In dogs with HF, the %aRIF increased significantly to 13.5 ± 0.57 (p Conclusion The results indicate that in dogs with HF, increased levels of RIF is associated with increased interstitial levels of GAL-3. The findings support the use of this dog model of HF to evaluate the effects of GAL-3 inhibitors for preventing or attenuating RIF that develops during the evolution of HF.

Chronic Therapy with Sacubitril/Valsartan Reduces Plasma Troponin-I Level in Dogs with Experimentally-Induced Cardiorenal Syndrome

Introduction Ongoing loss of cardiomyocytes occurs in heart failure (HF) and contributes to progressive worsening of the HF state. Sacubitril/Valsartan (S/Val), a combined angiotensin-II receptor blocker (Val) and neprilysin inhibitor (S) in a 1:1 molar ratio, was shown to reduce the risk of cardiovascular death or HF hospitalization in patients with HF and reduced left ventricular (LV) ejection fraction (EF). Chronic therapy with S/VAL was also shown to improve LV systolic function in dogs with experimentally-induced cardiorenal syndrome. Objective This study tested the hypothesis that chronic therapy with S/Val in dogs with cardiorenal syndrome ameliorates ongoing loss of cardiomyocytes as evidenced by lowering plasma levels of troponin-I (TnI). Methods 14 dogs with coronary microembolization-induced HF and renal dysfunction induced by unilateral nephrectomy with imposed stenosis of the contralateral renal vein, were randomized to 3 months therapy with S/Val (100 mg once daily, n=7) or no therapy (control, CON, n=7). LV EF was measured before (PRE) and at 12 weeks after initiating therapy with S/Val (POST). High sensitivity plasma TnI was measured when animals were normal (NL) and again after induction of cardiorenal syndrome and subsequently at 2, 4, and 12 weeks after initiating S/Val therapy. TnI levels were determined using a commercially available Ultra-Sensitive Dog Cardiac Troponin-I Elisa kit and the concentration was expressed in ng/ml. Results In CON dogs, LV EF was unchanged from PRE to POST (35 ± 1 vs. 36 ± 1 %) but increased significantly from PRE to POST in S/Val-treated dogs (34 ± 1 vs. 41 ± 2 %, p Table ) and remained elevated throughout the follow-up period. In contrast, in S/Val-treated dogs, TnI levels decreased gradually during the therapy period ( Table ). Conclusions In dogs with cardiorenal syndrome, S/Val reduces plasma TnI levels compared to untreated CON. This observations suggests that chronic therapy with S/Val attenuates or prevents ongoing loss cardiomyocytes, a characteristic feature of the HF state.

Elamipretide Normalizes Protein and mRNA Expression Levels of Mitofilin in Left Ventricular Myocardium of Dogs with Advanced Heart Failure

Mitofilin (MF) is a protein of the inner mitochondrial (MITO) membrane and has critical functions in MITO morphology and MITO fusion and fission, specifically in the formation of tubular cristae and cristae junctions. MF also regulates cytochrome c release during apoptosis. Down-regulation of MF results in increased apoptosis and disorganization of the MITO inner membrane; abnormalities that are also manifested in the heart failure (HF). We showed that MF levels are markedly reduced in LV myocardium of dogs with HF as well as in explanted failed human heart. Elamipretide (ELAM), a novel MITO-targeting peptide, has been shown to improve MITO function and morphology in animals with experimental HF. This study tested the hypothesis that chronic therapy with ELAM can reverse the dysregulation of MF in LV myocardium of dogs with coronary microembolization-induced HF (LV ejection fraction ~30%).

Abstract 248: Elamipretide Reverses Dysregulation of mRNA Expression Levels of FoxO Transcription Factors 1, 3a and 4 in Left Ventricular Myocardium of Dogs with Advanced Heart Failure

Background: FoxO (Forkhead box) family of transcription factors play important roles in regulating the expression of genes involved in physiologic cellular functions that include 1) cell proliferation and growth, 2) oxidative stress and DNA repair, 3) apoptosis and autophagy, 4) energy metabolism and 5) immune system function. Many components of all 5 cellular functions are abnormal in the failing heart. FoxO1, FoxO3, and FoxO4 are members of the FoxO family and are expressed in adult cardiomyocytes. We previously showed that elamipretide (ELAM), a novel mitochondria-targeting peptide, reverses many of the abnormalities of the above captioned cellular function in dogs with advanced heart failure (HF). Abnormalities of expression and/or phosphorylation of FoxO1, FoxO3a and FoxO4 have been described in HF. Objective: This study examined the effects of chronic therapy with ELAM on levels of mRNA expression of FoxO1, FoxO3a and FoxO4 in LV myocardium of dogs with coronary microembolization-induced HF (LV ejection fraction ~30%). Methods: LV tissue from 14 HF dogs randomized to 3 months monotherapy with subcutaneous injections of ELAM (0.5 mg/kg once daily, n=7) or no therapy at all (control, CON, n=7) and tissue from 6 normal (NL) dogs was used in the study. Using specific primers, mRNA levels of FoxO1, FoxO3a, and FoxO4 normalized to β-actin, an internal control, were measured using real-time PCR in isolated RNA from LV tissue. Results: There were no differences in the levels of β-actin among the 3 study groups. mRNA expression levels of FoxO1 and 3a were significantly decreased and FoxO4 increased in HF-CON dogs compared to NL dogs (0.16, 0.19, and 2.48 fold change from NL respectively, p&lt;0.05). Treatment of HF dogs with ELAM restored the expression of all 3 FoxO transcription factors to near NL (0.53, 0.65, and 1.21 fold change from NL respectively, P&lt;0.05 vs. CON). Conclusions: mRNA levels of FoxO1 and FoxO3a are reduced and that of FoxO4 is increased in LV myocardium of HF dogs. Chronic therapy with ELAM normalizes expression of all 3 FoxO transcription factors. This improvement in FoxO expression is consistent with the observed reduction of oxidative stress, apoptosis and cytokines and improved energy metabolism in HF dogs following chronic therapy with ELAM.

Abstract 432: Elamipretide (BendaviaTM) Restores Aldehyde Dehydrogenase-2 Protein Levels and 4-Hydroxy-2-Nonenal Protein Adducts in Left Ventricular Myocardium of Dogs with Heart Failure

Background: Reactive aldehydes such as 4-hydroxy-2-nonenal (4-HNE) are generated in the failing heart and contribute to cardiomyocyte injury and death and progressive left ventricular (LV) dysfunction. Aldehyde dehydrogenase-2 (ALDH2) plays a pivotal role in detoxifying mitochondrial (MITO) reactive aldehydes. We previously showed that long-term therapy with Elamipretide (ELA, Bendavia TM ), a novel MITO targeting peptide, improves LV systolic function and normalizes MITO function and rate of ATP synthesis in dogs with heart failure (HF). In this study, we examined the effects of long-term treatment with ELA on protein levels of 4-HNE adducts and ALDH2 in LV myocardium of dogs with coronary microembolization-induced HF (LV ejection fraction ~30%). Methods: LV tissue from 14 HF dogs randomized to 3 months monotherapy with subcutaneous injections of ELA (0.5 mg/kg once daily, n=7) or saline (control, CTR, n=7) and tissue from 6 normal (NL) dogs was used in the study. Using LV tissue extracts, 4-HNE protein adducts levels were quantified using a commercially available Elisa kit and expressed as ng/mg. In isolated MITO fractions prepared from LV tissue, protein levels of ALDH2 and porin, the latter used as an internal loading control, were determined by Western blotting coupled with Chemiluminescence. Band intensity was expressed in densitometric units (DU). Results: No changes in protein level of porin was observed among the 3 study groups (NL: 0.26±0.02; CTR: 0.24±0.01; BEN: 0.26±0.01 DU). 4-HNE protein adducts levels were increased in CTR dogs compared to NL dogs and treatment with ELA partially restored 4-HNE to near normal levels (NL: 185±21; CTR: 399±35*; ELA: 252 ± 18† ng/mg, *=p&lt;0.05 vs. NL; †=p&lt;0.05 vs. CTR). Compared to NL, dogs, ALDH2 protein levels were significantly reduced in HF CTR dogs (0.49±0.02 vs. 1.16±0.10; p&lt;0.05). Treatment with ELA significantly increased ALDH2 protein compared to untreated CTR (0.74±0.02 DU, p&lt;0.05). Conclusions: Long-term therapy with ELA normalizes ALDH2 and 4-HNE levels in LV myocardium of dogs with HF. Improved protein levels of ALDH2 in HF after therapy with ELA can account, in part, for the observed improvement of global LV function elicited by long-term therapy with ELA.

Abstract 231: Bendavia, a Novel Mitochondria-Targeting Peptide, Improves Contraction and Relaxation of Failing Cardiomyocytes Isolated From Dogs With Chronic Heart Failure

Background: Mitochondria (MITO) of humans and dogs with heart failure (HF) manifest functional abnormalities characterized by poor respiration, reduced rate of ATP synthesis and increased production of reactive oxygen species (ROS) that adversely impact LV systolic and diastolic function. We previously showed that chronic therapy with Bendavia (BEN, MTP-131), a novel mitochondria-targeting peptide, improves global LV function in dogs with HF without affecting heart rate or blood pressure. This improvement was associated with a reversal of MITO abnormalities and normalization of rate of ATP synthesis. This study tested the hypothesis that the improvement in global LV function seen in dogs with HF during treatment with BEN results primarily from enhanced function of constituent LV cardiomyocytes. Methods: Cardiomyocytes were isolated from the LV free wall of 8 untreated dogs with coronary microembolization-induced HF (LV ejection fraction &lt;30%). A collagenase-based enzymatic process was used for the isolation and yielded ~70% viable rod-shaped cardiomyocytes that excluded trypan blue. Extent of cardiomyocytes shortening, shortening velocity and lengthening velocity were assessed during 1.0 Hz electrical field stimulation delivered via a MyoPacer (ION Optix). Measurements were made at baseline and were repeated after one hour of gradual exposure of the same cardiomyocytes to BEN at a concentration of 0.1 μM. Results: At baseline, the extent of cardiomyocyte shortening was 3.7 ± 0.8 μm, shortening velocity was 62.8 ± 16.9 μm /sec and lengthening velocity was -53.8 ± 16.5 μm/sec. Exposure of cardiomyocyte to BEN significantly increased the extent of cardiomyocyte shortening to 5.4 ± 1.1 μm (p&lt;0.012), shortening velocity to 94.5 ± 21.9 μm/sec (p&lt;0.020) and lengthening velocity to -96.8 ± 21.1 μm/sec (p&lt;0.016) compared to baseline. Conclusions: Exposure of failing isolated cardiomyocytes to BEN elicits improvements in the rate of cardiomyocyte shortening and re-lengthening indicative of improved cell contractility and relaxation. This improvement is likely mediated by increased availability of ATP along with reduced ROS production both secondary to improved mitochondrial function elicited by treatment with BEN.

Nitroxyl (HNO)

Background— The nitroxyl (HNO) donor, Angeli’s salt, exerts positive inotropic, lusitropic, and vasodilator effects in vivo that are cAMP independent. Its clinical usefulness is limited by chemical instability and cogeneration of nitrite which itself has vascular effects. Here, we report on effects of a novel, stable, pure HNO donor (CXL-1020) in isolated myoctyes and intact hearts in experimental models and in patients with heart failure (HF). Methods and Results— CXL-1020 converts solely to HNO and inactive CXL-1051 with a t 1/2 of 2 minutes. In adult mouse ventricular myocytes, it dose dependently increased sarcomere shortening by 75% to 210% (50–500 μmol/L), with a ≈30% rise in the peak Ca 2+ transient only at higher doses. Neither inhibition of protein kinase A nor soluble guanylate cyclase altered this contractile response. Unlike isoproterenol, CXL-1020 was equally effective in myocytes from normal or failing hearts. In anesthetized dogs with coronary microembolization-induced HF, CXL-1020 reduced left ventricular end-diastolic pressure and myocardial oxygen consumption while increasing ejection fraction from 27% to 40% and maximal ventricular power index by 42% (both P &lt;0.05). In conscious dogs with tachypacing-induced HF, CXL-1020 increased contractility assessed by end-systolic elastance and provided venoarterial dilation. Heart rate was minimally altered. In patients with systolic HF, CXL-1020 reduced both left and right heart filling pressures and systemic vascular resistance, while increasing cardiac and stroke volume index. Heart rate was unchanged, and arterial pressure declined modestly. Conclusions— These data show the functional efficacy of a novel pure HNO donor to enhance myocardial function and present first-in-man evidence for its potential usefulness in HF. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifiers: NCT01096043, NCT01092325.

Long-term therapy with Bendavia (MTP-131), a novel mitochondria-targeting peptide, improves left ventricular systolic function in dogs with chronic heart failure

Background: Mitochondria (MITO) of the failing heart manifest structural and functional abnormalities evidenced by hyperplasia, reduced organelle size and diminished respiration that lead to a defect in ATP synthesis. Bendavia (MTP-131), a novel, first in class, MITO-targeting peptide, improves the efficiency of mitochondria electron transfer chain and enhances ATP synthesis in multiple organs including heart, kidney and skeletal muscle. The present study examined the effects of long-term therapy with Bendavia on LV systolic function and ATP synthesis in dogs with chronic heart failure (HF) (LV ejection fraction, EF∼30%). Methods: Fourteen dogs with coronary microembolization-induced HF were randomized to 3 months therapy with subcutaneous injections of Bendavia (0.5 mg/kg once daily, n=7) or saline (Control, n=7). LV end-diastolic (EDV) and end-systolic (ESV) volumes, EF, heart rate (HR), mean aortic pressure (AP), LV end-diastolic pressure (EDP) and peak LV +dP/dt were measured before (PRE) and after 3 months of therapy (POST). Treatment effect Δ, within each group, was calculated as the difference between PRE and POST. MITO ATP synthesis and ATP/ADP ratio were measured in isolated LV cardiomyocytes obtained at the end of 3 months of therapy using the bioluminescent ApoSENSORTM ATP/ADP assay kit. Results: Bendavia had no effect on HR or mAP. Compared to Control, Bendavia decreased EDV, ESV and EDP, increased EF and peak LV +dP/dt and increased ATP synthesis and ratio of ATP/ADP (Table). View this table: Indexes of LV function and ATP Synthesis Conclusions: In HF dogs, long-term monotherapy with Bendavia improves LV systolic function without increasing HR or decreasing mAP. Bendavia increased ATP synthesis; a likely mediator of improved LV function.

Defects in Free Fatty Acid Oxidation and Glucose Oxidation Coexist in the Failing Heart

Purpose Abnormalities of energy substrate utilization exist in the failing heart and contribute to disease progression. These abnormalities are attributed by some to decreased glucose utilization and by others to reduced free fatty acid (FFA) oxidation. In the normal heart, recruitment of the glucose transport proteins GLUT-1 and -4 is a mechanism by which the heart increases glucose transport for metabolism while up- or down-expression of muscle carnitine palmitoyl transferase (mCPT-1) provides directionally concordant regulation of FFA oxidation. In the present study we tested the hypothesis that defects of both GLUT-1 and -4 and mCPT-1 coexist in the failing LV myocardium. Methods and Materials Studies were performed in LV tissue homogenate obtained from 6 normal (NL) donor human hearts, 6 explanted failing human hearts with dilated cardiomyopathy (DCM) and 6 failing human hearts with ischemic cardiomyopathy (ICM) and from 6 NL and 7 coronary microembolization-induced heart failure (HF) dogs. Protein levels of the glucose transporters, GLUT-1 and -4 where measured in human and dog hearts and mCPT-1 in dog hearts using specific antibodies and Western blotting and bands quantified in densitometric units (du). Results Compared to NL, protein levels of GLUT-1 and -4 were significantly decreased in DCM, ICM and HF dogs and mCPT-1 was significantly decreased in HF dogs (Table). Conclusions Abnormalities of key regulators of FFA oxidation and glucose oxidation coexist in the failing heart regardless of HF etiology and favor energy deprivation. Coexistence of these abnormalities in the failing heart can act to limit the benefits that may be derived from therapies that target. Protein Expression in LV MyocardiumNL-Human DonorDCMICMGLUT-1 (du)15.7 ± 0.910.6 ± 0.3 * 0.41 ± 0.02 * GLUT-4 (du)31.7 ± 1.719.5 ± 1.8 * 16.6 ± 1.4 * NL-DogHF-DogGLUT-1 (du)20.1 ± 3.04.7 ± 0.5 † GLUT-4 (du)24.5 ± 3.116.2 ± 0.8 † mCPT-1 (du)1.40 ± 0.070.53 ± 0.06 † *=p

Abstract 19183: Insulin Resistance Develops after the Onset of Heart Failure in Dogs

Background: Heart failure (HF) is a condition associated with increased plasma norepinephrine levels. Norepinephrine is known to affect glucose homeostasis by decreasing insulin sensitivity. We have previously reported an increase in plasma norepinephrine levels in coronary microembolization-induced HF dogs. However, the status of plasma insulin and glucose levels is unknown in large animal models of HF. In the present study, we examined insulin and glucose levels in fasted plasma from dogs before and after the onset of HF. Methods: 12 healthy mongrel dogs weighing 20-30 kg underwent serial coronary microembolization to produce HF. Embolization was performed every 1-2 weeks until angiographic left ventricular ejection fraction (LVEF) was &lt;35%. All procedures were performed during cardiac catheterization, under general anesthesia and sterile conditions. Fasted plasma was collected before and after inducing HF and was stored at -80 o C. Insulin and glucose levels were determined using commercially available ELISA kits for insulin and colorimetric assay kits for glucose, and expressed in microunits/mL and mg/dL, respectively. Homeostasis assessment model for insulin resistance (HOMA-IR) ([fasting insulin in microunits/mL * fasting glucose in mg/dL] * 0.5551/22.5) was calculated in all dogs at baseline and after inducing HF. Data were analyzed using paired t-tests. Results: Baseline LVEF was &gt; 55% in all dogs. Once HF was established, mean LVEF was 31 ± 1%. Baseline mean fasting blood glucose and fasting plasma insulin were 84 ± 17 mg/dL and 9.7 ± 3.6 microunits/mL, respectively. Once HF was established, fasting blood glucose rose to 161 ± 44 mg/dL (p&lt;0.0001) and fasting plasma insulin increased to 16.5 ± 4.0 microunits/mL (p=0.0008). HOMA-IR score increased from 2.0 ± 0.8 at baseline to 6.7 ± 3.0 with HF (p=0.0002). Conclusions: Hyperglycemia, hyperinsulinemia and insulin resistance develop after the onset of heart failure due to coronary microembolization in dogs consistent with observations previously reported in patients with chronic HF. This large animal model of HF can serve as a useful tool in exploring the underlying causes and consequences of insulin resistance in the setting of chronic HF.

Abstract P175: Selective Regional Injections of Alginate Hydrogel into Cardiac Veins Improve Left Ventricular Function and Reverse Chamber Remodeling in Dogs with Chronic Heart Failure

Background: Progressive LV enlargement and dysfunction are characteristics of heart failure (HF) and are associated with increased mortality and morbidity. We tested the hypothesis that selective regional injections of alginate hydrogel implants (AHI, Algisyl-LVR, Lonestar Heart, Inc.) into isolated segments of epicardial veins of the failing LV will increase LV wall thickness and lead to reduced LV size, lower LV wall stress and improved LV systolic and diastolic function. Methods: 12 dogs with coronary microembolization-induced HF (LV ejection fraction, EF&lt;30%) were studied. During an open-chest procedure, 1.5 to 2.0 cm segments of the 2 nd diagonal branch and the 2 nd marginal branch of the cardiac epicardial veins were isolated by ligation with silk sutures. In 6 dogs, the isolated segments were each injected with 1.0 ml of AHI and in 6 dogs with normal saline (controls). LV ED volume (EDV), ES volume (ESV), EF, stroke volume (SV), ED wall stress (EDWS), deceleration time of early mitral inflow velocity (DT), and severity of functional mitral regurgitation (MR) were measured before therapy (Pre) and at 6 months after AHI or saline delivery (Post). The treatment effect (Δ) was calculated as the difference between Pre and Post. Results: In preliminary we showed that an intravenous injection of 1.0 ml AHI increased regional LV end-diastolic (ED) and end-systolic (ES) wall thickness by 5.8 ± 0.7 % and 9.0 ± 1.0 %, respectively. Compared to saline controls, treatment of HF dogs with AHI prevented the increase in EDV and significantly decreased ESV, EDWS and severity of functional MR (Table). In addition, AHI significantly increased LV EF, SV and DT indicating improved LV systolic and diastolic function (Table). Treatment with Alginate implants also showed a safe and non-arrhythmogenic chronic profile. Conclusion: LV reconstruction using selective regional injections of AHI into epicardial cardiac veins represents a safe novel approach for the treatment of advanced chronic HF. Table 1. Hemodynamic and Ventriculographic Results Control (n=6) AHI (n=6) P-Value ΔEDV (ml) 2.5 ± 1.0 −1.1 ± 0.4 0.114 ΔESV (ml) 4.3 ± 1.7 −3.9 ± 0.4 0.001 ΔEF (%) −3.8 ± 1.5 5.0 ± 0.4 0.001 ΔSV (ml) −1.8 ± 0.8 0.11 ± 0.04 0.001 ΔEDWS (gm/cm²) 9.4 ± 6.5 −23.1 ± 4.6 0.006 ΔDT (msec) −4.7 ± 0.4 27.0 ± 4.4 0.001 ΔMR (%) 1.7 ± 0.8 −3.6 ±1.3 0.004

Chronic electrical stimulation of the carotid sinus baroreflex improves left ventricular function and promotes reversal of ventricular remodeling in dogs with advanced heart failure.

Autonomic abnormalities exist in heart failure and contribute to disease progression. Activation of the carotid sinus baroreflex (CSB) has been shown to reduce sympathetic outflow and augment parasympathetic vagal tone. This study tested the hypothesis that long-term electric activation of the CSB improves left ventricular (LV) function and attenuates progressive LV remodeling in dogs with advanced chronic heart failure. Studies were performed in 14 dogs with coronary microembolization-induced heart failure (LV ejection fraction ≈25%). Eight dogs were chronically instrumented for bilateral CSB activation using the Rheos System (CVRx Inc, Minneapolis, Minn) and 6 were not and served as controls. All dogs were followed for 3 months, and none received other background therapy. During follow-up, treatment with CSB increased LV ejection fraction 4.0±2.4% compared with a reduction in control dogs of −2.8±1.0% (P<0.05). Similarly, treatment with CSB decreased LV end-systolic volume -2.5±2.7 mL compared with an increase in control dogs of 6.7±2.9 mL (P<0.05). Compared with control, CSB activation significantly decreased LV end-diastolic pressure and circulating plasma norepinephrine, normalized expression of cardiac β(1)-adrenergic receptors, β-adrenergic receptor kinase, and nitric oxide synthase and reduced interstitial fibrosis and cardiomyocyte hypertrophy. In dogs with advanced heart failure, CSB activation improves global LV function and partially reverses LV remodeling both globally and at cellular and molecular levels.

Response to Letter Regarding Article “Large Animal Models of Heart Failure: A Critical Link in the Translation of Basic Science to Clinical Practice”

HomeCirculation: Heart FailureVol. 3, No. 2Response to Letter Regarding Article “Large Animal Models of Heart Failure: A Critical Link in the Translation of Basic Science to Clinical Practice” Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBResponse to Letter Regarding Article “Large Animal Models of Heart Failure: A Critical Link in the Translation of Basic Science to Clinical Practice” Jennifer A. Dixon, MD and Francis G. Spinale, MD, PhD Jennifer A. DixonJennifer A. Dixon Division of Cardiothoracic Surgery, Medical University of South Carolina, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC Search for more papers by this author and Francis G. SpinaleFrancis G. Spinale Division of Cardiothoracic Surgery, Medical University of South Carolina, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC Search for more papers by this author Originally published1 Mar 2010https://doi.org/10.1161/CIRCHEARTFAILURE.109.934430Circulation: Heart Failure. 2010;3:e4To the Editor:We thank Schmitto et al for the insightful response to our review “Large Animal Models of Heart Failure: A Critical Link in the Translation of Basic Science to Clinical Practice.”1 The thrust of this commentary was that the use of large animal models of microembolization to produce a chronic myocardial ischemia/heart failure model was not fully developed.The microembolization model may be useful for creating a relevant clinical phenotype of ischemic cardiomyopathy. Specifically, the work done by Schmitto et al2 in sheep provides a clinically relevant model of coronary microembolization-induced heart failure, which may be amenable to chronic studies. For example, Goldstein et al3 used an ovine microembolization-induced heart failure model to demonstrate that partial support with a centrifugal left ventricular assist device is sufficient to create significant reductions in left ventricular myocardial oxygen consumption. Huang et al4 correlated apoptotic markers with left ventricular wall stress in a chronic ovine microembolization-induced heart failure model. A porcine model of microembolization-induced heart failure was used by Buus et al5 to demonstrate the preservation of contractile function of the smooth muscle cells and endothelial production of nitric oxide in small coronary arteries. These studies exemplify the principle that although a multitude of large animal models of heart failure exist, it is crucial to select the model most appropriate to the clinical issue being investigated.Although we readily acknowledge that studies using large animal models of heart failure require special monetary and organizational investment, the earlier-mentioned work characterizes a tremendous potential for clinically translatable knowledge, which can be gained from this area of research.DisclosuresNone.FootnotesE-mail [email protected] References 1 Dixon JA, Spinale FG. Large animal models of heart failure: a critical link in the translation of basic science to clinical practice. Circ Heart Fail. 2009; 2: 262–271.LinkGoogle Scholar2 Schmitto JD, Coskun KO, Coskun ST, Ortmann P, Vorkamp T, Heidrich F, Sossalla S, Popov AF, Tirilomis T, Hinz J, Heuer J, Quintel M, Chen FY, Schöndube FA. Hemodynamic changes in a model of chronic heart failure induced by multiple sequential coronary microembolization in sheep. Artif Organs. 2009; 33: 947–952.CrossrefMedlineGoogle Scholar3 Goldstein AH, Monreal G, Kambara A, Spiwak AJ, Schlossberg ML, Abrishamchian AR, Gerhardt MA. Partial support with a centrifugal left ventricular assist device reduces myocardial oxygen consumption in chronic, ischemic heart failure. J Card Fail. 2005; 1: 142–151.Google Scholar4 Huang Y, Hunyor SN, Jiang L, Kawaguchi O, Shirota K, Ikeda Y, Yuasa T, Gallagher G, Zeng B, Zheng X. Remodeling of the chronic severely failing ischemic sheep heart after coronary microembolization: functional, energetic, structural, and cellular responses. Am J Physiol Heart Circ Physiol. 2004; 286: H2141–H2150.CrossrefMedlineGoogle Scholar5 Buus NH, Terp K, Baandrup U, Mulvany MJ, Nyborg NC. Pharmacological characterization of coronary small arteries from pigs with chronic ischaemic myocardial remodelling. Clin Sci (Lond). 1998; 94: 141–147.CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetails March 2010Vol 3, Issue 2 Advertisement Article InformationMetrics https://doi.org/10.1161/CIRCHEARTFAILURE.109.934430 Originally publishedMarch 1, 2010 PDF download Advertisement SubjectsHeart Failure

A Method for Automatically Optimizing Medical Devices for Treating Heart Failure: Designing Polymeric Injection Patterns

Heart failure continues to present a significant medical and economic burden throughout the developed world. Novel treatments involving the injection of polymeric materials into the myocardium of the failing left ventricle (LV) are currently being developed, which may reduce elevated myofiber stresses during the cardiac cycle and act to retard the progression of heart failure. A finite element (FE) simulation-based method was developed in this study that can automatically optimize the injection pattern of the polymeric "inclusions" according to a specific objective function, using commercially available software tools. The FE preprocessor TRUEGRID((R)) was used to create a parametric axisymmetric LV mesh matched to experimentally measured end-diastole and end-systole metrics from dogs with coronary microembolization-induced heart failure. Passive and active myocardial material properties were defined by a pseudo-elastic-strain energy function and a time-varying elastance model of active contraction, respectively, that were implemented in the FE software LS-DYNA. The companion optimization software LS-OPT was used to communicate directly with TRUEGRID((R)) to determine FE model parameters, such as defining the injection pattern and inclusion characteristics. The optimization resulted in an intuitive optimal injection pattern (i.e., the one with the greatest number of inclusions) when the objective function was weighted to minimize mean end-diastolic and end-systolic myofiber stress and ignore LV stroke volume. In contrast, the optimization resulted in a nonintuitive optimal pattern (i.e., 3 inclusions longitudinallyx6 inclusions circumferentially) when both myofiber stress and stroke volume were incorporated into the objective function with different weights.

Skeletal Muscle Mitochondria in Microembolism‐induced Heart Failure

Bioenergetic failure is proposed as the primary mechanism responsible for the skeletal muscle myopathy in heart failure (HF). We analyzed the two populations of skeletal muscle mitochondria (subsarcolemmal, SSM, and interfibrillar, IFM) in moderately severe canine coronary microembolization‐induced HF. Activities of the electron transport chain (ETC) complexes, and integrated function (oxidative phosphorylation) in freshly isolated intact mitochondria were measured. The yield of SSM was unchanged while that of IFM was increased in HF. These IFM showed decreased oxidative phosphorylation with complex I substrates while respiratory rates with complexes II, III and IV substrates were normal. The activities of individual ETC complexes, including complex I, were normal. Thus, the content of skeletal muscle IFM is increased by HF, but these mitochondria have a selective defect in oxidative phosphorylation through complex I. We are exploring whether the organization of oxidative phosphorylation in supercomplexes (respirasomes) is disrupted in these skeletal muscle IFM in HF.

Acute Left Ventricular Unloading in Dogs With Chronic Heart Failure: Continuous Aortic Flow Augmentation Versus Intra-Aortic Balloon Pumping

Background Continuous aortic flow augmentation (CAFA) therapy with the Cancion System (Orqis Medical, Inc) was shown to effectively unload the left ventricle in dogs with chronic heart failure (HF). This study compared the extent of acute left ventricular (LV) unloading elicited by CAFA to that elicited by intra-aortic balloon counterpulsation (IABP) in normotensive dogs with coronary microembolization-induced HF. Methods and Results Seven HF dogs were studied with both CAFA and IABP in random order and 1 week apart. In both instances, active therapy was maintained for 4 hours. The Cancion system was positioned using a dual femoral approach configuration with a constant pump flow of 250 mL/min. In all dogs and with both devices, LV end-diastolic pressure (EDP), LV end-systolic volume (ESV), and LV ejection fraction (EF) were measured at baseline and at 2 and 4 hours after instituting CAFA or IABP. Plasma samples obtained at the end of 4 hours of therapy were used to measure a host of circulating biomarkers that included neurohormones, cytokines, and A-type and B-type natriuretic peptides. IABP had no significant effects on LVEDP, LVESV, and LVEF. In contrast, CAFA significantly decreased LVEDP and LVESV and increased LVEF. Compared with IABP, CAFA was accompanied by significant improvements in circulating levels of neurohormones, cytokines, and natriuretic peptides. Conclusions The results indicate that CAFA is more effective than IABP in achieving acute global LV unloading in dogs with chronic HF not complicated by ongoing myocardial ischemia or cardiogenic shock.

Abstract 2415: Long-Term Baroreflex Activation Therapy Increases the Threshold for the Induction of Lethal Ventricular Arrhythmias in Dogs with Chronic Advanced Heart Failure

Heart failure (HF) is associated with a high incidence of ventricular tachycardia (VT) and fibrillation (VF). Patients with HF in whom these lethal arrhythmias can be induced by electrophysiological (EP) testing carry a high risk of sudden cardiac death. We showed that chronic electrical carotid baroreflex activation therapy (BAT) with the Rheos® System (CVRx, Inc.) improves LV function, attenuates LV remodeling and restores autonomic sympathetic-parasympathetic balance in dogs with HF. This study examined the effects of long-term therapy with BAT on the induction of VT or VF in dogs with coronary microembolization-induced HF (LV ejection fraction ~20%). Eleven dogs with HF underwent EP testing at baseline prior to therapy and after 3 and 6 months of therapy with BAT and again 6 weeks after withdrawal of BAT therapy (n = 7) or no therapy at all (Control, n = 4). Programmed ventricular stimulation was performed from the right ventricular apex and included delivery of up to 4 extrastimuli at progressively shorter coupling intervals (in steps of 10 msec). The extrastimuli were delivered following 8 ventricular paced beats with a drive cycle length between 600 and 200 msec. If a sustained monomorphic VT or VF could not be induced, isoproterenol infusion was initiated to increase the sinus rate by ~30% and the EP stimulation protocol was repeated. At baseline, a sustained VT or VF was induced in all 11 dogs (100%). After 3 and 6 months of follow-up, all Control dogs (100%) were induced into sustained VT or VF. After 3 months of BAT, only 3 of 7 dogs (43%) were induced into sustained VT or VF. After 6 months of BAT, only 2 of 7 dogs (29%) were induced into sustained VT or VF. Finally after withdrawal of BAT therapy, all dogs (100%) were again induced into systained VT or VF. In addition to improving LV function and attenuating LV remodeling, long-term monotherapy with BAT markedly increases the threshold for lethal ventricular arrhythmias in dogs with chronic HF. This is a marked improvement over inducibility of lethal arrhythmias seen in historical untreated controls. This benefit of BAT supports the continued exploration of this device as a therapeutic modality for treating patients with chronic HF and increased risk of sudden cardiac death.