Ventricular remodeling. Mechanisms and prevention

Cardioprotective effect of silicon-built restraint device (ASD), for left ventricular remodeling in rat heart failure model

This study aims to evaluate the feasibility and cardio-protective effects of biocompatible silicon-built restraint device (ASD) in the rat's heart failure (HF) model. The performance and compliance characteristics of the ASD device were assessed in vitro by adopting a pneumatic drive and ball burst test. Sprague-Dawley (SD) rats were divided into four groups (n = 6); control, HF, HF + CSD, and HF + ASD groups, respectively. Heart failure was developed by left anterior descending (LAD) coronary artery ligation in all groups except the control group. The ASD and CSD devices were implanted in the heart of HF + ASD and HF + CSD groups, respectively. The ASD's functional and expansion ability was found to be safe and suitable for attenuating ventricular remodeling. ASD-treated rats showed normal heart rhythm, demonstrated by smooth -ST and asymmetrical T-wave. At the same time, hemodynamic parameters of the HF + ASD group improved systolic and diastolic functions, reducing ventricular wall stress, which indicated reverse remodeling. The BNP values were reduced in the HF + ASD group, which confirmed ASD feasibility and reversed remodeling at a molecular level. Furthermore, the HF + ASD group with no fibrosis suggests that ASD has significant curative effects on the heart muscles. In conclusion, ASD was found to be a promising restraint therapy than the previously standard restraint therapies. Stepwise ASD fabrication process (a) 3D computer model of ASD was generated by using Rhinoceros 5.0 software (b) 3D blue wax model of ASD (c) Silicon was prepared by mixing the solutions (as per manufacturer instruction) (d) Blue wax model of ASD was immersed into liquid Silicon (e) ASD model was put into the oven for 3 hours at 50 °C. (f) Blue wax started melting from the ASD model (g) ASD model was built from pure silicon (h) Two access lines were linked to the ASD device, which was connected with an implantable catheter (Port-a-cath), scale bar 100 µm. (Nikon Ldx 2.0).

P16ink4a overexpression ameliorates cardiac remodeling of mouse following myocardial infarction via CDK4/pRb pathway

BACKGROUND

P16ink4a can accumulate in senescent cells and can be induced by different oncogenic stimulations. These functions make p16ink4a a biomarker of senescence and cancer. However, the exact role of p16ink4a remains unclear in cardiovascular disease. This study was aimed to investigate the role of p16ink4a in cardiac remodeling after myocardial infarction (MI).

METHODS

In vivo, gain and loss of function experiments using p16ink4a overexpression and knockdown adenovirus were induced to determine the effect of p16ink4a on cardiac structure and function after MI. The in vitro effects of p16ink4a were evaluated by overexpression and knockdown adenovirus of p16ink4a on isolated neonatal mouse cardiac myocytes (NMCMs) and neonatal mouse cardiac fibroblasts (NMCFs).

RESULTS

Expression level of p16ink4a was increased after MI and enriched in the infarction area. In vivo, overexpression of p16ink4a protected, while knockdown of p16ink4a worsened cardiac function. In vitro, p16ink4a did not influence the hypertrophy of NMCMs. Overexpression of p16ink4a inhibited the proliferation and migration of NMCFs and reduced the level of collagen I and α-SMA. Consistently, knockdown of p16ink4a in vitro displayed the opposite effects. Further mechanism studies revealed that p16ink4a affected the expression level of cyclin-dependent kinase 4 (CDK4) and phosphorylation of retinoblastoma (pRb), which could be a potential pathway in regulating cardiac remodeling after MI.

CONCLUSION

Overexpression of 16ink4a in cardiac fibroblasts can ameliorate cardiac dysfunction and attenuate pathological cardiac remodeling in mice after MI by regulating the p16ink4a/CDK4/pRb pathway.

Diagnostic performance of miR-214, BNP, NT-proBNP and soluble ST2 in acute heart failure

PURPOSE

This study aimed to investigate the potential diagnostic value of miR-214, B-type natriuretic peptide (BNP), N terminal-pro BNP (NT-proBNP) and soluble ST2 (sST2) in acute heart failure (AHF).

METHOD

This study included 176 patients as the AHF group and 60 healthy subjects as the control group from February 2018 to February 2020. Patients in the AHF group were classified according to the New York Heart Association (NYHA) functional classification, including 60 level II patients, 59 level III patients and 57 level IV patients. The expression level of miR-214, BNP, NT-proBNP and sST2 of both groups were recorded and analysed.

RESULTS

The morbidity of cardiovascular diseases was significantly higher in the AHF group than in the control group (P < .05). The expression level of miR-214, BNP, NT-proBNP and sST2 in the AHF group were all significantly higher than in the control group (P < .05). Besides, the expression level of all the molecules in level IV was significantly higher than that of level III and level II, respectively (P < .001, P < .001). In addition, the expression level of all the molecules in level III was significantly higher than that of level II (P < .001). The area under the ROC curve of miR-214, BNP, NT-proBNP and sST2 were 0.913, 0.836, 0.849 and 0.855, respectively, indicating good diagnostic value.

CONCLUSION

MiR-214, BNP, NT-proBNP and sST2 can be used as effective biomarkers for AHF, providing a new strategy for diagnosis and for judging the severity of AHF.

Organ-saving surgical alternatives to treatment of heart failure

Over time, various surgical treatment strategies have evolved to manage advanced heart failure (HF). Scientific and technological breakthroughs through the last 50 years have put forward various surgical alternatives to patients with advanced HF encompassing surgical ventricular restoration to surgical gene therapy and stem cell replacement of the diseased ventricles. Organ-saving surgical options which used to be promising included dynamic cardiomyoplasty, partial resection of ventricle and cardiac wrapping with Acorn CorCap cardiac support device. These procedures were eventually abandoned due to negative outcomes and without proven disadvantages. Another organ-saving surgical option currently being considered but still make little sense is cardiac regeneration by stem cell therapy, i.e., cardiomyocyte restoration and replacement. Presently, the organ-saving surgical alternatives to treat end-stage HF are revascularization for ischemic cardiomyopathy, mitral valve surgery (repair or replacement) for ischemic mitral incompetence (IMI), left ventricular (LV) aneurysmectomy (surgical ventricular restoration) and mitral valve repair for IMI. These aforementioned procedures have become quite established approaches and with increasing experience are continuously being modified to improve outcome. Various mechanical circulatory support systems have emerged over time to improve functional status of patients with advanced HF, either as a bridge to heart transplantation or as a bridge to myocardial recovery. Likewise offered in those with contraindications to transplantation. Ventricular assist devices (VAD) can keep patients alive until an eventual transplantation. This article reviews the variety of the myriad of alternative organ-saving surgical alternatives that have been available or are currently available provided to patients with end-stage HF, their advantages and deficiencies, as well as prospects in HF therapy.

Epinephrine soaked tampons induced transient acute dilated cardiomyopathy during FESS procedure

Background

Epinephrine, in all modes of use, may pose a wide range of cardiotoxic events, ranging from sinus tachycardia to heart failure, life threatening arrhythmias, and even death. Because of daily and extensive use of epinephrine, these unusual and rare events tend to be forgotten by physicians. We present a case of dilated cardiomyopathy that developed following routine use of epinephrine-impregnated tampons during function endoscopic sinus (FESS) surgery.

Case presentation

A healthy, 24-year-old man with no family history of heart disease has undergone elective surgery under general anesthesia to repair the paranasal sinuses using endoscopic approach. During surgery, soon after being treated with 1: 1000 diluted epinephrine-soaked tampons, an hypertensive crisis was noticed followed by pulseless electrical activity. An extensive examination led to the diagnosis of non-ischemic dilated cardiomyopathy. After several days of heart failure medical therapy, complete resolution of all structural and functional changes was achieved.

Conclusion

In our case, we present an unusual and rare event of acute dilated cardiomyopathy following the use of epinephrine-soaked tampons during elective FESS surgery. A prompt response was observed after several days of heart failure treatment. Awareness of the epinephrine cardiotoxic potential even in the form of soaked tampons is essential for proper diagnosis and prompt treatment.

Serum endotrophin levels in patients with heart failure with reduced and mid-range ejection fraction

BACKGROUND

Endotrophin, a type VI collagen cleavage product, has fibrosis, and insulin resistance effects. Type VI collagen also plays a role in cardiac fibrosis. In this study, we aimed to investigate the role of endotrophin in the pathogenesis of cardiac fibrosis by determining its levels in patients with heart failure with reduced and mid-range ejection fraction (EF). We also aimed to determine the possible association between endotrophin and treatment that prevents ventricular fibrosis.

METHODS

Sixty patients with heart failure with reduced and mid-range EF and 27 volunteers with no cardiac failure were included in this study. In both groups, biochemical tests, EF, and endotrophin levels were measured. ELISA was performed for the determination of endotrophin levels.

RESULTS

When compared with the control group, there was no significant difference for endotrophin levels in the patient group (p = .35). Participants in the study were divided into two groups according to their EFs, 40% and less, and 40-49%. They were classified according to their use of renin-angiotensin-aldosterone system (RAAS) blocking drugs. Endotrophin levels were significantly lower in patients with mid-range EFs between 40 and 49% (p = .03) using RAAS blockers.

CONCLUSION

This study is the first to evaluate the relationship between endotrophin and heart failure. Endotrophin levels were found to be low in patients with heart failure with mid-range EF who were using RAAS blockers. This suggests that RAAS blockers may influence endotrophin levels and thus could have a role in the prevention of remodelling.

Use of Multifactorial Treatments to Address the Challenge of Translating Experimental Myocardial Infarct Reduction Strategies

Myocardial tissue damage that occurs during an ischemic event leads to a spiraling deterioration of cardiac muscle structural and functional integrity. Reperfusion is the only known efficacious strategy and is the most commonly used treatment to reduce injury and prevent remodeling. However, timing is critical, and the procedure is not always feasible for a variety of reasons. The complex molecular basis for cardioprotection has been studied for decades but formulation of a viable therapeutic that can significantly attenuate myocardial injury remains elusive. In this review, we address barriers to the development of a fruitful approach that will substantially improve the prognosis of those suffering from this widespread and largely unmitigated disease. Furthermore, we proffer that ephrinA1, a candidate molecule that satisfies many of the important criteria discussed, possesses robust potential to overcome these hurdles and thus offers protection that surpasses the limitations currently observed.

Cardioprotective effects of lysyl oxidase inhibition against volume overload-induced extracellular matrix remodeling

A hallmark of heart failure (HF) is adverse extracellular matrix (ECM) remodeling, which is regulated by the collagen cross-linking enzyme, lysyl oxidase (LOX). In this study, we evaluate the efficacy of LOX inhibition to prevent adverse left ventricular (LV) remodeling and dysfunction using an experimental model of HF. Sprague-Dawley rats were subjected to surgically induced volume overload (VO) by creation of aortocaval fistula (ACF). A LOX inhibitor, beta-aminopropionitrile (BAPN; 100 mg/kg/day), was administered to rats with ACF or sham surgery at eight weeks postsurgery. Echocardiography was used to assess progressive alterations in cardiac ventricular structure and function. Left ventricular (LV) catheterization was used to assess alterations in contractility, stiffness, LV pressure and volume, and other indices of cardiac function. The LV ECM alterations were assessed by: (a) histological staining of collagen, (b) protein expression of collagen types I and III, (c) hydroxyproline assay, and (d) cross-linking assay. LOX inhibition attenuated VO-induced increases in cardiac stress, and attenuated increases in interstitial myocardial collagen, total collagen, and protein levels of collagens I and III. Both echocardiography and catheterization measurements indicated improved cardiac function post-VO in BAPN treated rats vs. untreated. Inhibition of LOX attenuated VO-induced decreases in LV stiffness and cardiac function. Overall, our data indicate that LOX inhibition was cardioprotective in the volume overloaded heart.

Role of cardiac magnetic resonance in the evaluation of dilated cardiomyopathy: diagnostic contribution and prognostic significance

Dilated cardiomyopathy (DCM) represents the final common morphofunctional pathway of various pathological conditions in which a combination of myocyte injury and necrosis associated with tissue fibrosis results in impaired mechanical function. Recognition of the underlying aetiology of disease and accurate disease monitoring may be crucial to individually optimize therapeutic strategies and stratify patient's prognosis. In this regard, CMR has emerged as a new reference gold standard providing important information for differential diagnosis and new insight about individual risk stratification. The present review article will focus on the role of CMR in the evaluation of present condition, analysing respective strengths and limitations in the light of current literature and technological developments.

The cardiac expression of Mas receptor is responsive to different physiological and pathological stimuli

The Mas protooncogene encodes a G protein-coupled receptor that has been described as a functional receptor for the cardioprotective fragment of the renin-angiotensin system (RAS), Angiotensin (Ang)-(1-7). The aim of this current study was to evaluate the responsiveness of Mas expression in hearts during different physiological and pathological conditions in rats. Physical training was considered a physiological condition, while isoproterenol-induced hypertrophy, myocardial infarction and DOCA-salt model of hypertension were used as pathological models of heart injury. The expression of Mas was analyzed by western blotting. Although swim-trained rats presented significant cardiac hypertrophy, our physical training protocol was unable to induce changes in the expression of Mas. On the other hand, cardiac hypertrophy and damage elicited by isoproterenol treatment led to a reduction in Mas expression. Myocardial infarction also significantly decreased the expression of Mas after 21 days of myocardial ischemia. Additionally, Mas expression levels were increased in hearts of DOCA-salt rats. Our present data indicate that Mas expression is responsive to different pathological stimuli, thereby suggesting that Mas receptor is involved in the homeostasis of the heart, as well as in the establishment and progression of cardiac diseases.

Intramyocardial administration of chimeric ephrinA1-Fc promotes tissue salvage following myocardial infarction in mice

The purpose of this study was to investigate the role of intramyocardial administration of chimeric ephrinA1-Fc in modulating the extent of injury and inflammation in non reperfused myocardial infarction (MI). Our results show that intramyocardial injection of 6 μg ephrinA1-Fc into the border zone immediately after permanent coronary artery ligation in B6129s mice resulted in 50% reduction of infarct size, 64% less necrosis, 35% less chamber dilatation and 32% less left ventricular free wall thinning at 4 days post-MI. In the infarct zone, Ly6G+ neutrophil density was 57% reduced and CD45+ leukocyte density was 21% reduced. Myocyte damage was also reduced in ephrinA1-Fc-treated hearts, as evidenced by 54% reduced serum cardiac troponin I. Further, we observed decreased cleaved PARP, increased BAG-1 protein expression, increased phosphorylated AKT/total AKT protein, and reduced NF-κB protein with ephrinA1-Fc administration, indicating improved cellular survival. Of the eight EphA receptors known to be expressed in mice (A1–A8), RT-PCR revealed that A1–A4, A6 and A7 were expressed in the uninjured adult myocardium. Expression of EphA1–A3 and EphA7 were significantly increased following MI while EphA6 expression decreased. Treatment with ephrinA1-Fc further increased EphA1 and EphA2 gene expression and resulted in a 2-fold increase in EphA4. Upregulation and combinatorial activation of these receptors may promote tissue survival. We have identified a novel, beneficial role for ephrinA1-Fc administration at the time of MI, and propose this as a promising new target for infarct salvage in non reperfused MI. More experiments are in progress to identify receptor-expressing cell types as well as the functional implications of receptor activation.

Synthesis, characterization and therapeutic efficacy of a biodegradable, thermoresponsive hydrogel designed for application in chronic infarcted myocardium

Injection of a bulking material into the ventricular wall has been proposed as a therapy to prevent progressive adverse remodeling due to high wall stresses that develop after myocardial infarction. Our objective was to design, synthesize and characterize a biodegradable, thermoresponsive hydrogel for this application based on copolymerization of N-isopropylacrylamide (NIPAAm), acrylic acid (AAc) and hydroxyethyl methacrylate-poly(trimethylene carbonate) (HEMAPTMC). By evaluating a range of monomer ratios, poly(NIPAAm-co-AAc-co-HEMAPTMC) at a feed ratio of 86/4/10 was shown to be ideal since it formed a hydrogel at 37 degrees C, and gradually became soluble over a 5 month period in vitro through hydrolytic cleavage of the PTMC residues. HEMAPTMC, copolymer and degradation product chemical structures were verified by NMR. No degradation product cytotoxicity was observed in vitro. In a rat chronic infarction model, the infarcted left ventricular (LV) wall was injected with the hydrogel or phosphate buffered saline (PBS). In the PBS group, LV cavity area increased and contractility decreased at 8 wk (p<0.05 versus pre-injection), while in the hydrogel group both parameters were preserved during this period. Tissue ingrowth was observed in the hydrogel injected area and a thicker LV wall and higher capillary density were found for the hydrogel versus PBS group. Smooth muscle cells with contractile phenotype were also identified in the hydrogel injected LV wall. The designed poly(NIPAAm-co-AAc-co-HEMAPTMC) hydrogel of this report may thus offer an attractive biomaterial-centered treatment option for ischemic cardiomyopathy.

Gene transfection with human hepatocyte growth factor complementary DNA plasmids attenuates cardiac remodeling after acute myocardial infarction in goat hearts implanted with ventricular assist devices

BACKGROUND

Although a left ventricular assist device is often used to provide circulatory support until transplantation in severe heart failure, the mortality of long-term use of left ventricular assist devices remains high. We have shown that hepatocyte growth factor causes angiogenesis, antifibrosis, and antiapoptosis in the myocardium. Therefore, gene therapy with hepatocyte growth factor-complementary DNA plasmids may enhance the chance of "bridge to recovery." In this study, we performed gene therapy with hepatocyte growth factor in the impaired goat heart with a left ventricular assist device.

METHODS

Cardiac impairment was induced in 6 adult goats (56-65 kg) by ligation of the coronary artery, and ventricular assist devices were installed. The hepatocyte growth factor group (HGF; n = 3) was administered human hepatocyte growth factor-complementary DNA plasmid (2.0 mg) in the myocardium. The control group (n = 3) was similarly administered beta-galactosidase plasmid. Four weeks after gene transfection, we attempted to wean all goats from the ventricular assist device.

RESULTS

The myocardia transfected with human hepatocyte growth factor-complementary DNA contained human hepatocyte growth factor protein at levels as high as 1.0 +/- 0.3 ng/g tissue 3 days after transfection. After weaning from the ventricular assist device, the HGF group showed good hemodynamics, whereas the control group showed deterioration. The percentage of fractional shortening was significantly higher in the HGF group than the control group (HGF vs control, 37.9% +/- 1.7% vs 26.4% +/- 0.3%, respectively; P < .01). Left ventricular dilatation associated with myocyte hypertrophy and fibrotic changes was detected in the control group but not in the HGF group. Vascular density was markedly increased in the HGF group.

CONCLUSIONS

These results suggest that gene therapy with human hepatocyte growth factor may enhance the chance of bridge to recovery in the impaired heart supported with a ventricular assist device.

Ascending Aorta Outflow Graft Location and Pulsatile Ventricular Assist Provide Optimal Hemodynamic Support in an Adult Mock Circulation

Although continuous flow (CF) and pulsatile flow (PF) ventricular assist devices (VADs) are being clinically used, their effects on aortic blood flow, as a measure of overall blood distribution, remain unclear. In acute VAD support animal experiments, our group has described a zone of turbulent mixing in the aortic arch. The objective of this study was to confirm this finding in the controlled setting of an adult mock circulation, simulating ventricular pathophysiologic states (normal and failing ventricle). CF and PF flow VADs were connected to ventricular apical inflow and ascending aorta (AA) or descending aorta (DA) outflow cannulae. Cardiovascular pressure and flow waveforms were recorded at varying levels of VAD bypass resulting in four test conditions: (i) CF-AA; (ii) CF-DA; (iii) PF-AA; and (iv) PF-DA. Confirming the animal data, no differences in mean aortic flow between CF and PF VADs were found, and significantly lower mean aortic arch flow with DA cannulation was noted. Mean aortic root flow decreased with increasing VAD bypass flow. As in the animal studies, despite similar mean flow rates, significant differences in waveform morphology were observed for AA and DA outflow graft locations and varying levels of VAD bypass. At 100% VAD support in the failing heart, PF restored waveform pulsatility to normal baseline while CF resulted in little pulsatility. These results confirm our earlier findings in the animal model, suggesting that outflow graft location may have a significant effect on aortic blood flow distribution. The long-term implications of these findings are being examined in ongoing studies.

Global Left Ventricular Remodeling with the Acorn Cardiac Support Device: Hemodynamic and Angiographic Findings in Dogs with Heart Failure

Preventing progressive left ventricular (LV) remodeling is paramount in the treatment of heart failure. In recent years, several surgical approaches have been implemented with the objective of improving LV function through amelioration of progressive LV remodeling. These included surgical reduction of LV size, the so-called Batista procedure, dynamic cardiomyoplasty and mitral valve repair to limit or eliminate functional mitral regurgitation. While the Batista procedure and dynamic cardiomyoplasty have for all practical purposes been abandoned, the lessons learned from these procedures gave rise to a new generation of devices aimed at preventing progressive LV dilation and restoring LV shape by passive mechanical containment of the failing LV. One such device is the Acorn Cardiac Support Device (CSD) or the CorCap. Studies in dogs with intracoronary microembolization-induced moderate and advanced heart failure have shown that long-term monotherapy with the CSD not only prevents progressive LV dilation but, in effect, partially reverses this phenotype. These studies have also shown that the CSD restores, albeit in part, progressive LV chamber sphericity and attenuates functional mitral regurgitation. These benefits were accompanied by improvement in global LV function along with improvements of remodeling at the cellular level. The findings were largely responsible for initiating safety and feasibility clinical trials with the CSD and ultimately, the initiation of the Acorn efficacy trial that was completed in 2004. This review will focus on studies conducted in dogs with heart failure and, specifically on hemodynamic, angiographic and echocardiographic results from these studies that provided support for the CSD as a successful technology targeting "reverse LV remodeling" for the treatment of heart failure.

Myocardial Interstitial Matrix Metalloproteinase Activity Is Altered by Mechanical Changes in LV Load

LV myocardial remodeling is a structural hallmark of hypertensive hypertrophy, but molecular mechanisms driving this process are not well understood. The matrix metalloproteinases (MMPs) can cause myocardial remodeling in chronic disease states, but how MMP activity is altered with a mechanical load remains unknown. The present study quantified interstitial MMP activity after a discrete increase in LV load and dissected out the contributory role of the angiotensin II Type 1 receptor (AT1R). Pigs (38 kg) were randomized to undergo (1) increased LV load by insertion of an intra-aortic balloon pump (IABP) triggered at systole for 3 hours, then deactivated (n=11); (2) IABP and AT1R blockade (AT1RB; valsartan, 3 ng/kg/hr; n=6). MMP activity was directly measured in the myocardial interstitium using a validated inline digital fluorogenic microdialysis system. IABP engagement increased LV peak pressure from 92+/-3 to 113+/-5 and 123+/-7 mm Hg in the vehicle and AR1RB group, respectively, and remained elevated throughout the IABP period (P<0.05). With IABP disengagement, segmental shortening (% change from baseline of 0) remained depressed in the vehicle group (-32.2+/-11.8%, P<0.05) but returned to baseline in the AT1RB group (2.3+/-12.5%). MMP activity decreased with IABP in both groups. At IABP disengagement, a surge in MMP activity occurred in the vehicle group that was abrogated with AT1RB (3.03+/-0.85 versus 0.07+/-1.55 MMP units/hr, P<0.05). A transient increase in LV load caused a cyclic variation in interstitial MMP activity that is regulated in part by the AT1R. These temporally dynamic changes in MMP activity likely influence myocardial function and structure with increased LV load.

Therapeutic left ventricular assist device and apheresis on dilated cardiomyopathy

Pathogenesis and therapies of dilated cardiomyopathy (DCM) have been discussed for a long time, but both of the ultimate answers are still unknown. In the last decade, the pathogenic role of immunological factors, such as cardiac autoimmune antibodies and cytokines, have been discussed attentively. This has led to one possible new therapy, immunoadsorption, which removes antibodies, and it has made a remarkable effect. However, there are other factors to remove. For the removal of cytokines and neurohormones, the most effective method is hemofiltration (HF). Also, double-filtration plasmapheresis (DFPP) removes immunoglobulin as well as low-density lipoprotein (LDL) and coagulation factors that may improve blood circulation, including the coronary arteries. Therefore, to eliminate all deteriorative factors, both apheresis therapies, HF and DFPP, should be performed. Due to the shortage of donor hearts, left ventricular assist systems (LVAD) have been used as a bridge to transplantation. It has now been reported that the total unloading of the left ventricle does not only maintain, but also recovers, the cardiac function, even from end-stage heart failure. However, the patients who have obtained a long-lasting recovery of cardiac function from an LVAD are still in a minority. To make this the majority, therapeutic LVAD should be combined with the apheresis therapies, DFPP and HF. We believe that this concept, a combination of HF and DFPP with therapeutic LVAD, will be the next generation of treatment that has a potential to postpone, or even avoid, heart transplantation.

Infarct resorption, compensatory hypertrophy, and differing patterns of ventricular remodeling following myocardial infarctions of varying size

OBJECTIVES

We sought to identify advantages of contrast-enhanced magnetic resonance imaging (MRI) in studying postinfarction ventricular remodeling.

BACKGROUND

Although sequential measurements of ventricular volumes, internal dimensions, and total ventricular mass have provided important insights into postinfarction left ventricular remodeling, it has not been possible to define serial, directionally opposite changes in resorption of infarcted tissue and hypertrophy of viable myocardium and effects of these changes on commonly used indices of remodeling.

METHODS

Using gadolinium-enhanced MRI, the time course and geometry of changes in infarcted and noninfarcted regions were assessed serially in dogs subjected to coronary occlusion for 45 min, 90 min, or permanently.

RESULTS

Infarct mass decreased progressively between three days and four to eight weeks following coronary occlusion; terminal values averaged 24 +/- 3% of those at three days. Radial infarct thickness also decreased progressively, whereas changes in circumferential and longitudinal extent of infarction were variable. The ability to define the circumferential endocardial and epicardial extents of infarction allowed radial thinning without epicardial expansion to be distinguished from true infarct expansion. The mass of noninfarcted myocardium increased by 15 +/- 2% following 90-min or permanent occlusion. However, the time course of growth of noninfarcted myocardium differed systematically from that of infarct resorption. Measurements of total ventricular mass frequently failed to reflect concurrent changes in infarcted and noninfarcted regions. Reperfusion accelerated infarct resorption. Histologic reductions in nucleus-to-cytoplasm ratios corresponded with increases in noninfarcted ventricular mass.

CONCLUSIONS

Concurrent directionally opposite changes in infarcted and noninfarcted myocardium can be defined serially, noninvasively, and with high spatial resolution and full ventricular coverage following myocardial infarction.

Reverse Remodeling of the Failing Ventricle: Surgical Intervention With the Acorn Cardiac Support Device

Preclincial studies have shown that an innovative meshlike cardiac support device (CorCap, Acorn Cardiovascular, Inc., St. Paul, MN) can provide end diastolic support to reduce mechanical stress, improve function, and reverse cardiac remodeling. The CorCap device has been implanted worldwide in more than 130 patients with dilated cardiomyopathy (idiopathic or ischemic), with or without concomitant cardiac surgery. A series of 48 patients was implanted in initial safety and feasibility studies (33 received concomitant cardiac surgery, 15 patients received the CorCap device only). At implant, 33 patients were in New York Heart Association functional class III, 11 in class II, and four in class IV. There were no device-related intraoperative complications, deaths, or adverse events. Eight early and nine late deaths occurred during follow-up extending to 18-24 months. During follow-up, chamber dimensions decreased, and ejection fraction and New York Heart Association functional class improved. The CorCap device is correlated with improvements in patient functional status. Randomized clinical trials are underway in Europe, Australia, and North America.

Hemodynamic and Pressure–Volume Responses to Continuous and Pulsatile Ventricular Assist in an Adult Mock Circulation

This study investigated the hemodynamic and left ventricular (LV) pressure-volume loop responses to continuous versus pulsatile assist techniques at 50% and 100% bypass flow rates during simulated ventricular pathophysiologic states (normal, failing, recovery) with Starling response behavior in an adult mock circulation. The rationale for this approach was the desire to conduct a preliminary investigation in a well controlled environment that cannot be as easily produced in an animal model or clinical setting. Continuous and pulsatile flow ventricular assist devices (VADs) were connected to ventricular apical and aortic root return cannulae. The mock circulation was instrumented with a pressure-volume conductance catheter for simultaneous measurement of aortic root pressure and LV pressure and volume; a left atrial pressure catheter; a distal aortic pressure catheter; and aortic root, aortic distal, VAD output, and coronary flow probes. Filling pressures (mean left atrial and LV end diastolic) were reduced with each assist technique; continuous assist reduced filling pressures by 50% more than pulsatile. This reduction, however, was at the expense of a higher mean distal aortic pressure and lower diastolic to systolic coronary artery flow ratio. At full bypass flow (100%) for both assist devices, there was a pronounced effect on hemodynamic parameters, whereas the lesser bypass flow (50%) had only a slight influence. Hemodynamic responses to continuous and pulsatile assist during simulated heart failure differed from normal and recovery states. These findings suggest the potential for differences in endocardial perfusion between assist techniques that may warrant further investigation in an in vivo model, the need for controlling the amount of bypass flow, and the importance in considering the choice of in vivo model.

Global surgical experience with the Acorn cardiac support device

OBJECTIVE

Surgical intervention is an option for treating the remodeled and dilated left ventricles of patients with heart failure. Providing end-diastolic support with an innovative mesh-like cardiac support device reduces mechanical stress, improves function, and reverses cardiac remodeling in animal models without safety issues. The objective of this study was to review the global clinical safety and feasibility experience of this device.

METHODS

The Acorn CorCap cardiac support device (Acorn Cardiovascular, Inc, St Paul, Minn) has been implanted worldwide in more than 130 patients with dilated cardiomyopathy with or without concomitant cardiac surgery. The device is positioned around the ventricles and given a custom fit. A series of 48 patients were implanted with the device in initial safety and feasibility studies, of whom 33 also received concomitant cardiac surgery.

RESULTS

At implantation, 11 patients were in New York Heart Association class II, 33 were in class III, and 4 were in class IV. The average CorCap implantation time was 27 minutes. The mean intraoperative reduction in left ventricular end-diastolic dimension was 4.6% +/- 1%. There were no device-related intraoperative complications. Eight early and 9 late deaths occurred during follow-up extending to 24 months. Actuarial survival was 73% at 12 months and 68% at 24 months. There were no device-related adverse events or evidence of constrictive disease, and coronary artery flow reserve was maintained. Ventricular chamber dimensions decreased, whereas ejection fraction and New York Heart Association class were improved in patients overall and in those patients implanted with the CorCap device without concomitant operations.

CONCLUSIONS

The CorCap device appears safe for patients with dilated cardiomyopathy. Randomized clinical trials are underway in Europe, Australia, and North America.

Surgical Remodeling in Ischemic Cardiomyopathy

Ischemic cardiomyopathy has a very poor prognosis, despite significant advances in pharmacologic therapy in the past decade. Orthotopic heart transplantation is an option for only a small minority of patients. Due to donor shortage and a finite outcome after transplant, nontransplant surgical intervention should be intensively investigated. Coronary artery bypass grafting improves survival in patients with demonstrated myocardial viability. Despite this, patients with the greatest left ventricular volumes do not show an improvement in outcomes. Surgical remodeling results in an improved stress-strain relationship and favorable myocardial remodeling. This may lead to improved survival, improvement in ventricular anatomy, and better quality of life. Surgical remodeling is often combined with revascularization, valve repair, and cardiac resynchronization therapy, along with optimal pharmacologic regimens, to provide a comprehensive therapeutic strategy for patients with this infirmity.

Sex-related differences in heart failure

Heart failure (HF) is a complex syndrome that is generally defined as cardiac output not adequate to meet the circulatory demands of the body. HF is at the end of the continuum of cardiovascular disease and preceded by an initiating event such as myocardial infarction, untreated hypertension, idiopathic cause, congenital heart disease, or pulmonary hypertension. In recent years, research has revealed differences in various aspects of HF between men and women including risk factors, pathophysiology, clinical manifestations, and response to treatment. Therefore, the purpose of this review is to review these sex-related differences between men and women who live with HF.

Surgical methods to reverse left ventricular remodeling in congestive heart failure

In this review article, we describe the most common surgical procedures currently used to reverse or arrest remodeling of the left ventricle in patients with congestive heart failure (CHF). The selection of the appropriate operation in a patient is a complex decision-making process, rigorously based on pathophysiologic considerations. In this population, all factors affecting the surgical risk should be carefully evaluated preoperatively, and surgery should be recommended when definite benefits in survival and quality of life can be reasonably predicted. Quite often, patients with CHF require a combination of different procedures to address all the pathophysiologic components determining the clinical picture. In particular, in this review we describe the surgical restoration of the left ventricle, the isolated coronary artery bypass graft procedure, the correction of mitral regurgitation, diastolic support (from dynamic cardiomyoplasty to passive containment), and mechanical assist devices. Moreover, in the future, the role of surgery in the treatment of CHF will be strongly modified by the advent of gene therapy, cell therapy, and engineered artificial myocardial tissue.

Left ventricular assist devices: an alternative to medical therapy for end-stage heart failure

Although aggressive medical therapy and ultimately cardiac transplantation have long been the therapeutic mainstays for patients with end-stage heart failure, the left ventricular assist device (LVAD), which was originally used clinically as a bridge to transplantation, may also be used as destination therapy. LVAD therapy for selected patients has been shown in the REMATCH trial to be superior to medical therapy in ameliorating symptoms and improving outcome in patients with terminal heart failure. LVAD therapy has also proved useful in improving native heart function by neuroendocrine modulation and reverse remodeling. Furthermore, current evidence suggests that when LVAD therapy is utilized to improve ventricular function, it may be further enhanced when combined with aggressive medical therapy.

Pathogenetic basis of myocardial dysfunction and amenability to reversal

As the role of the LVAD graduates from the "bridge-to-transplant" to the "bridge-to-recovery," several important issues need to be answered. Such a paradigm would require a definition of appropriate candidates for LVAD implantation, the most appropriate time for LVAD placement during the management of end-stage CHF, reliable histologic, biochemical, and imaging markers of recovery, and the optimum duration of LVAD support. The device technology must be refined further to reduce the morbidity associated with the device itself, and to make the device smaller, less invasive, and less thrombogenic. It will be a challenge to identify the role for concomitant drug therapy and to develop weaning programs for device support. Finally, guidelines will have to be developed to monitor and manage these patients after explantation of LVAD.

Left ventricular assist device as a bridge to recovery: present status

A new application for left ventricular assist devices (LVAD) is as a bridge to recovery. In the settings of myocarditis and dilated cardiomyopathy, LVAD support is accompanied by marked hemodynamic, neurohormonal, physiologic, cellular, and molecular changes indicative of recovery. Despite these changes, experience with clinical successes is limited. Further studies of topics such as the timing of LVAD implantation and explantation, adjunct medical and surgical therapy, and optimum LVAD weaning protocols might help improve the success of this promising technology.

Reverse remodeling and enhanced adrenergic reserve from passive external support in experimental dilated heart failure

OBJECTIVES

We sought to test the efficacy of a passive elastic containment device to reverse chronic chamber remodeling and adrenergic down-regulation in the failing heart, yet still maintaining preload reserve.

BACKGROUND

Progressive cardiac remodeling due to heart failure is thought to exacerbate underlying myocardial dysfunction. In a pressure-volume analysis, we tested the impact of limiting progressive cardiac dilation by an externally applied passive containment device on both basal and adrenergic-stimulated function in failing canine hearts.

METHODS

Ischemic dilated cardiomyopathy was induced by repeated intracoronary microembolizations in six dogs. The animals were studied before and three to six months after surgical implantation of a thin polyester mesh (cardiac support device [CSD]) that surrounded both cardiac ventricles. Pressure-volume relations were measured by a conductance micromanometer catheter.

RESULTS

Long-term use of the CSD lowered end-diastolic and end-systolic volumes by -19 +/- 4% and -22 +/- 8%, respectively (both p < 0.0001) and shifted the end-systolic pressure-volume relation to the left (p < 0.01), compatible with reverse remodeling. End-diastolic pressure and chamber diastolic stiffness did not significantly change. The systolic response to dobutamine markedly improved after CSD implantation (55 +/- 8% rise in ejection fraction after CSD vs. -10 +/- 8% before CSD, p < 0.05), in conjunction with a heightened adenylyl cyclase response to isoproterenol. There was no change in the density or affinity of beta-adrenergic receptors. Diastolic compliance was not adversely affected, and preload-recruitable function was preserved with the CSD, consistent with a lack of constriction.

CONCLUSIONS

Reverse remodeling with reduced systolic wall stress and improved adrenergic signaling can be achieved by passive external support that does not generate diastolic constriction. This approach may prove useful in the treatment of chronic heart failure.

TrueFISP: assessment of accuracy for measurement of left ventricular mass in an animal model

PURPOSE

To test the accuracy of a high performance true fast imaging with steady-state precession (TrueFISP) pulse sequence for the assessment of left ventricular (LV) mass in a large animal model on 1.5-T scanners.

MATERIALS AND METHODS

We imaged dogs (N = 10) on a clinical 1.5-T clinical scanner using electrocardiogram (ECG)-gated TrueFISP. In all animals, contiguous segmented k-space cine images were acquired from base to apex (in-plane resolution 1 x 1 mm(2), slice thickness 5 mm, TR = 4.8 msec, TE = 1.6 msec) during repeated breath-holds. In nine of the 10 animals, single-shot images gated to end-diastole were also acquired from base to apex in a single breath-hold (in-plane resolution 1 x 1 mm(2), slice thickness 5 mm, TR = 3.2 msec, TE = 1.6 msec). After imaging, animals were killed, the left ventricle was isolated, and the true mass of the left ventricle (free wall and septum) was determined. Independently, two observers blinded to the post-mortem results computed LV masses based on analysis of the magnetic resonance (MR) images.

RESULTS

Comparison of the computed LV mass using TrueFISP to the actual mass showed excellent agreement. Cine-systole was the most accurate technique (mass = 98.6% +/- 4.5% actual, bias = 1.2 +/- 3.4 g) followed by cine-diastole (mass = 97.9% +/- 5.3% actual, bias = 1.8 +/- 4.1 g) and single shot (mass = 94.7% +/- 7.9% actual, bias = 4.2 +/- 6.3 g). Inter- and intra-observer variabilities were low (5.8% +/- 7.1% and 0.4% +/- 4.8%, respectively).

CONCLUSION

We conclude that TrueFISP imaging is an accurate, rapid method to determine ventricular mass. In single-shot mode, TrueFISP requires only one breath-hold to estimate the mass of the heart within 6% of the actual value, whereas the segmented k-space implementation measured LV mass to within 3% of the true value.

Activation and release of degradative proteinases within the myocardium are the trigger for ventricular remodeling in chronic heart failure

Our conceptual framework of chronic heart failure is based upon the neurohormonal model. In this construct, neurohormonal systems that provide short-term homeostasis remain activated after a myocardial injury, producing progressive ventricular dysfunction and worsening heart failure. However, this model fails to explain several aspects of the pathophysiology of heart failure, including the mechanisms that trigger neurohoromone release and those that lead to ventricular dysfunction in the absence of a large myocardial infarction. These gaps in our understanding can be explained by an expanded model of heart failure, which focuses on myocardial matrix events as the triggers for disease progression. This model embraces the neurohormonal model, and integrates the roles of the immune system and the myocardial fibroblast, within the matrix, to more fully describe the initiation and progression of the disease.

Passive ventricular constraint for the treatment of congestive heart failure

Progressive heart failure is characterized by loss of cardiac function associated with maladaptive changes in myocardial gene expression and neuroendocrine activity, leading to progressive increases in heart size. Elevated ventricular wall stress results from an increase in chamber size, and is thought to play a role in furthering development towards end-stage disease. Reduction of wall stress and stress mediated myocardial stretch may be an important means for mitigating heart failure progression. One possible approach to accomplish this goal is through passive support of the heart with the Cardiac Support Device. Results from preclinical and clinical evaluation give support to this premise.

Healing the heart with ventricular assist device therapy: mechanisms of cardiac recovery

As experience has grown with the use of mechanical circulatory support systems in patients with cardiogenic shock, many anecdotes have been noted where myocardial recovery occurred and devices could be removed with reasonable residual cardiovascular performance and resolution of the shock syndrome. Indeed, when first used, ventricular assist devices were inserted to bridge patients unable to be separated from cardiopulmonary bypass to eventual recovery. Many successes with ventricular support systems have been recorded in individuals with postcardiotomy cardiogenic shock, acute myocarditis, and in the periinfarction period where stunning of potentially viable myocardial tissue contributed to severe heart failure. From an experimental standpoint, recovery of myocyte function and restoration of more normal myocardial geometry and constitution have been noted. There are many explanations for this, but principally, benefit is related to amelioration of circulatory insufficiency with attenuation of perturbed humoral networks and reduction of myocardial wall stress. It is important to understand how ventricular assist device implantation in select advanced heart failure patients might precipitate recovery of depressed myocardial function.

Left ventricular assist device bridge to recovery: a review of the current status

The use of the left ventricular assist device as a bridge to recovery represents a new phenomenon. This article focuses on bridge-to-recovery in the settings of myocarditis and dilated cardiomyopathy with a review of the hemodynamic, neurohormonal, physiologic, cellular, and molecular changes of recovery during left ventricular assist device support. Despite numerous markers of success, there is a disconnect from the limited clinical successes that are reviewed. The current status and future options to increase the chances of success are highlighted.

Cellular events linked to cardiac remodeling in heart failure: targets for pharmacologic intervention

Over the past decade, there has been a paradigm shift in the understanding of heart failure pathophysiology. Heart failure is no longer conceptualized as a hemodynamic disorder resulting from changes in renal and hormonal function. Rather, the syndrome of heart failure is more complex and is characterized by abnormal myocyte growth, proliferation of cells in the extracellular matrix, and myocyte cell loss (apoptosis)--all of which culminate in significant structural remodeling of the heart and loss of ventricular function. The loss of ventricle function is preceded by an initiating event such as myocardial infarction, which leads to changes in cell function, activation of specific neurohormones and peptides, which in turn are linked to the remodeling of the ventricle, and progression of heart failure. This article discusses how changes in myocyte and nonmyocyte structure may contribute to the progression of heart failure. Insight into these mechanisms will provide a better understanding of newer pharmacologic approaches in the treatment of heart failure.