Critical review of heart failure: the role of left ventricular remodeling in the therapeutic response

Empagliflozin maintains capillarization and improves cardiac function in a murine model of left ventricular pressure overload

Patients with type 2 diabetes treated with Sodium glucose transporter 2 (SGLT2) inhibitors show reduced mortality and hospitalization for heart failure (HF). SGLT2 inhibitors are considered to activate multiple cardioprotective pathways; however, underlying mechanisms are not fully described. This study aimed to elucidate the underlying mechanisms of the beneficial effects of SGLT2 inhibitors on the failing heart. We generated a left ventricular (LV) pressure overload model in C57BL/6NCrSlc mice by transverse aortic constriction (TAC) and examined the effects of empagliflozin (EMPA) in this model. We conducted metabolome and transcriptome analyses and histological and physiological examinations. EMPA administration ameliorated pressure overload-induced systolic dysfunction. Metabolomic studies showed that EMPA increased citrulline levels in cardiac tissue and reduced levels of arginine, indicating enhanced metabolism from arginine to citrulline and nitric oxide (NO). Transcriptome suggested possible involvement of the insulin/AKT pathway that could activate NO production through phosphorylation of endothelial NO synthase (eNOS). Histological examination of the mice showed capillary rarefaction and endothelial apoptosis after TAC, both of which were significantly improved by EMPA treatment. This improvement was associated with enhanced expression phospho-eNOS and NO production in cardiac endothelial cells. NOS inhibition attenuated these cardioprotective effects of EMPA. The in vitro studies showed that catecholamine-induced endothelial apoptosis was inhibited by NO, arginine, or AKT activator. EMPA activates the AKT/eNOS/NO pathway, which helps to suppress endothelial apoptosis, maintain capillarization and improve systolic dysfunction during LV pressure overload.

Cardiac mitofusin-1 is reduced in non-responding patients with idiopathic dilated cardiomyopathy

Prognosis of severe heart failure remains poor. Urgent new therapies are required. Some heart failure patients do not respond to established multidisciplinary treatment and are classified as “non-responders”. The outcome is especially poor for non-responders, and underlying mechanisms are largely unknown. Mitofusin-1 (Mfn1), a mitochondrial fusion protein, is significantly reduced in non-responding patients. This study aimed to elucidate the role of Mfn1 in the failing heart. Twenty-two idiopathic dilated cardiomyopathy (IDCM) patients who underwent endomyocardial biopsy of intraventricular septum were included. Of the 22 patients, 8 were non-responders (left ventricular (LV) ejection fraction (LVEF) of < 10% improvement at late phase follow-up). Electron microscopy (EM), quantitative PCR, and immunofluorescence studies were performed to explore the biological processes and molecules involved in failure to respond. Studies in cardiac specific Mfn1 knockout mice (c-Mfn1 KO), and in vitro studies with neonatal rat ventricular myocytes (NRVMs) were also conducted. A significant reduction in mitochondrial size in cardiomyocytes, and Mfn1, was observed in non-responders. A LV pressure overload with thoracic aortic constriction (TAC) c-Mfn1 KO mouse model was generated. Systolic function was reduced in c-Mfn1 KO mice, while mitochondria alteration in TAC c-Mfn1 KO mice increased. In vitro studies in NRVMs indicated negative regulation of Mfn1 by the β-AR/cAMP/PKA/miR-140-5p pathway resulting in significant reduction in mitochondrial respiration of NRVMs. The level of miR140-5p was increased in cardiac tissues of non-responders. Mfn1 is a biomarker of heart failure in non-responders. Therapies targeting mitochondrial dynamics and homeostasis are next generation therapy for non-responding heart failure patients.

Atlas-Based Ventricular Shape Analysis for Understanding Congenital Heart Disease

Congenital heart disease is associated with abnormal ventricular shape that can affect wall mechanics and may be predictive of long-term adverse outcomes. Atlas-based parametric shape analysis was used to analyze ventricular geometries of eight adolescent or adult single-ventricle CHD patients with tricuspid atresia and Fontans. These patients were compared with an "atlas" of non-congenital asymptomatic volunteers, resulting in a set of z-scores which quantify deviations from the control population distribution on a patient-by-patient basis. We examined the potential of these scores to: (1) quantify abnormalities of ventricular geometry in single ventricle physiologies relative to the normal population; (2) comprehensively quantify wall motion in CHD patients; and (3) identify possible relationships between ventricular shape and wall motion that may reflect underlying functional defects or remodeling in CHD patients. CHD ventricular geometries at end-diastole and end-systole were individually compared with statistical shape properties of an asymptomatic population from the Cardiac Atlas Project. Shape analysis-derived model properties, and myocardial wall motions between end-diastole and end-systole, were compared with physician observations of clinical functional parameters. Relationships between altered shape and altered function were evaluated via correlations between atlas-based shape and wall motion scores. Atlas-based shape analysis identified a diverse set of specific quantifiable abnormalities in ventricular geometry or myocardial wall motion in all subjects. Moreover, this initial cohort displayed significant relationships between specific shape abnormalities such as increased ventricular sphericity and functional defects in myocardial deformation, such as decreased long-axis wall motion. These findings suggest that atlas-based ventricular shape analysis may be a useful new tool in the management of patients with CHD who are at risk of impaired ventricular wall mechanics and chamber remodeling.

Does left ventricular shape influence clinical outcome in heart failure?

BACKGROUND

Left ventricular (LV) shape tends to become spherical in patients with dilated cardiomyopathy of diverse etiology. Clinical and echocardiographic factors which affect the degree of LV spherical distortion and the impact of altered LV shape on prognosis have not been studied adequately.

HYPOTHESIS

This study was undertaken to investigate the prognostic implications of altered LV shape on clinical outcome in dilated cardiomyopathy.

METHODS

In 112 patients with depressed LV ejection fraction (19 +/- 9%) and symptomatic heart failure, and in 10 age- and gender-matched normal controls, we performed 2-dimensional echocardiography to assess LV shape using the eccentricity index. Eccentricity index was defined as the ratio of the LV long axis to the LV transverse diameter, measured at end systole and end diastole in the apical four-chamber view. We sought univariate and multivariate clinical and echocardiographic correlates of LV shape. Further, we sought correlations between eccentricity index and clinical outcomes (death and composite outcome of death or emergent heart transplant).

RESULTS

Compared with controls, patients with cardiomyopathy had significantly lower systolic (2.04 vs. 1.56; p = 0.001) and diastolic (1.75 vs. 1.53; p = 0.003) eccentricity index, implying a more spherical LV shape. Of all clinical and echocardiographic variables tested, mitral regurgitation, right ventricular dysfunction, and increased LV mass were independently associated with spherical LV shape. At a follow-up period of 17 +/- 12 months, no correlation was found between eccentricity index and the occurrence of death or the combined endpoint of death or emergent heart transplant, in univariate or multivariate analysis.

CONCLUSIONS

In patients with dilated cardiomyopathy, the degree of spherical distortion of the LV does not correlate with prognosis.

Chronotropic response of cultured neonatal rat ventricular myocytes to short-term fluid shear

Ventricular myocytes are continuously exposed to fluid shear in vivo by relative movement of laminar sheets and adjacent cells. Preliminary observations have shown that neonatal myocytes respond to fluid shear by increasing their beating rate, which could have an arrhythmogenic effect under elevated shear conditions. The objective of this study is to investigate the characteristics of the fluid shear response in cultured myocytes and to study selected potential mechanisms. Cultured neonatal rat ventricular myocytes that were spontaneously beating were subjected to low shear rates (5-50/s) in a fluid flow chamber using standard culture medium. The beating rate was measured from digital microscopic recordings. The myocytes reacted to low shear rates by a graded and reversible increase in their spontaneous beating rate of up to 500%. The response to shear was substantially attenuated in the presence of the beta-adrenergic agonist isoproterenol (by 86+/-8%), as well as after incubation with integrin-blocking RGD peptides (by 92+/-8%). The results suggest that the beta-adrenergic signaling pathway and integrin activation, which are known to interact, may play an important role in the response mechanism.

An alternative to left ventricular volume reduction

BACKGROUND

Left ventricular (LV) remodeling leading to ventricular dilatation is ultimately a maladaptative process according to the law of Laplace. To counteract the wall stress increase, a new concept of reducing the LV cavity radius by changing the LV globular shape to a bilobular one through the insertion of transventricular splints has emerged. This procedure is tested in a model of congestive heart failure.

METHODS

A bovine model was used (n = 9). Following splint insertion through a sternotomy, boluses of 2 liters of crystalloid were injected. After every bolus, hemodynamic measurements were performed without and with the splints tightened to a 10% and 20% stress level reduction, respectively. Comparisons between the 3 measurements were performed with analysis of variance test (p < 0.05).

RESULTS

Splint tightening significantly reduced right and left heart pressures for central venous pressure (CVP) >10 mm Hg (CVP: 14.7 +/- 5.2, 12.1 +/- 5, 10.6 +/- 4.7 mm Hg, p < 0.001 for baseline, 10% and 20% stress level reduction, respectively; mean pulmonary artery pressure: 33.5 +/- 4.7, 31 +/- 4.4, 29.4 +/- 5.1 mm Hg, p < 0.001; pulmonary capillary wedge pressure: 20.5 +/- 2.8, 18.9 +/- 3.3, 17.5 +/- 3.1 mm Hg, p < 0.001). The same holds true for cardiac output (6.5 +/- 1.6, 6.7 +/- 1.4, 6.8 +/- 1.7 liter/minute, p < 0.001), whereas heart rate and mean arterial pressure were not affected. The systemic and pulmonary resistances did not vary significantly throughout the procedure. Importantly, none of the hemodynamic parameters worsened at any stage with the splints.

CONCLUSIONS

In this model, hemodynamic parameters are improved with the splints for higher values of CVP, supporting the concept of reshaping the remodeled LV. This technique has the potential to improve patients with congestive heart failure.

Optimizing the use of beta-blockers in the effective treatment and management of heart failure: a case study approach

Today, heart failure is an increasing concern in the United States. Its prognoses are poor and its treatment is a complicated endeavor, because heart failure is not a single disease state. Rather, it is a syndrome with a cyclic pathophysiology composed of multiple mechanisms. Effective case management of heart failure must address each of the many changes involved in this syndrome, and therapy must be individualized, especially because patients with heart failure often require regimens of five or more drugs. In special populations, such as the elderly and/or patients with concomitant diseases requiring added medication, polypharmacy becomes an important issue. Maintaining consistent compliance with the treatment regimen and patient education regarding symptoms of fluid retention can be critical. Currently, beta-blockers, in addition to standard therapy, are recommended as first-line treatment in mild-to-moderate heart failure. The three cases presented in this article illustrate some common scenarios encountered and clinical decisions made when beta-blockers are used in the management of heart failure.

Surviving heart failure: Robert L. Frye lecture

Heart failure is increasing in both incidence and prevalence and is associated with a high mortality. In patients with heart failure, coronary artery disease is the cause for about two thirds. Pathophysiologic changes have been linked to altered muscle function and hemodynamics, elevated neurohormones, and, more recently, cellular mechanisms, including apoptosis. Standard triple therapy for symptomatic heart failure consists of an angiotensin-converting enzyme (ACE) inhibitor, digoxin, and a diuretic. In patients with severe heart failure, spironolactone should be added. In large clinical trials, ACE inhibitors, spironolactone, and beta-blockers have reduced mortality. Other drugs may be helpful in the treatment of heart failure. Amiodarone is the antiarrhythmic drug of choice in patients with symptomatic arrhythmias and also has a role in the treatment of dilated cardiomyopathy. Angiotensin II receptor blockers are being compared with ACE inhibitors and appear promising. Newer agents being tested include antagonists to endothelin and tumor necrosis factor. Overall, it is clear that polypharmacy is the standard of care for patients with heart failure. A future challenge will be to prevent heart failure from occurring.

Neuropeptide Y receptor 1 (NPY-Y1) expression in human heart failure and heart transplantation

Neuropeptide Y (NPY) is a neurotransmitter released from cardiac sympathetic nerve terminals along with catecholamines. It influences vascular tone and cardiac function, probably through the receptor subtype Y1. The present study examined the expression of Y1 in patients with end-stage heart failure and in heart transplant recipients. Y1 mRNA was analyzed in right ventricular endomyocardial biopsies taken from 12 donor hearts prior to implantation (controls), 15 patients with end stage heart failure at time of transplantation, and 16 patients more than 1 year after transplantation. RT-PCR (reverse transcription polymerase chain reaction) was used to detect mRNA for the Y1 receptor, the beta1-adrenergic-receptor, and beta-actin. Y1 mRNA was present in biopsies of all donor hearts, but was observed significantly less frequently in the two patient groups; only 5 out of 15 (P < 0.01) heart failure and 9 out of 16 (P < 0.05) transplant recipients demonstrated visible PCR product. In contrast, mRNA for the beta1-adrenergic receptor and beta-actin were detected by RT-PCR in all samples. Our results provide the first evidence for altered regulation of the neuropeptide Y1 receptor in heart failure and transplant patients, and suggests that loss of signal transduction by this receptor may be adaptive in both groups.

Effect of exercise training on myocardial remodeling in patients with reduced left ventricular function after myocardial infarction: application of magnetic resonance imaging

BACKGROUND

There are conflicting reports on the effects of training on the remodeling process in post-myocardial infarction patients with ventricular damage.

METHODS AND RESULTS

Twenty-five patients with reduced ventricular function (mean ejection fraction, 32.3+/-6%) after an anteroseptal or inferolateral myocardial infarction were randomized to an exercise group (n=12) or a control group (n=13). Patients in the exercise group resided in a rehabilitation center for 2 months and underwent a training program consisting of two 1-hour sessions of walking daily, along with four monitored 45-minute sessions of stationary cycling weekly. Before and after the study period, maximal exercise testing and cardiac MRI were performed. Oxygen uptake increased 26% at maximal exercise (19.7+/-3 to 23.9+/-5, P<.05) and 39% at the lactate threshold (P<.01) in the exercise group, whereas control values did not change. No differences were observed within or between groups in MRI measures of end-diastolic (187+/-47 pre versus 196+/-35 mL post in the exercise group and 179+/-52 pre versus 180+/-51 mL post in the control group), end-systolic volume (118+/-41 pre versus 121+/-33 mL post in the exercise group and 119+/-54 pre versus 116+/-56 mL post in the control group), or ejection fraction (38.0+/-9 pre versus 38.2+/-10% post in the exercise group and 37.0+/-10 pre versus 38.3+/-13% post in the control group). Myocardial wall thickness measurements at end diastole and end systole and their difference in 80 myocardial segments determined by MRI yielded no significant interactions between groups. When myocardial wall thickness measurements were classified by infarct or noninfarct areas, no differences were observed between groups over the study period.

CONCLUSIONS

A high-intensity, 2-month residential cardiac rehabilitation program resulted in substantial increases in exercise capacity among patients with reduced left ventricular function. In contrast to some recent reports, the training program had no deleterious effects on left ventricular volume, function, or wall thickness regardless of infarct area.