Assessment and relevance of ventricular wall stress in heart failure

Relation between right ventricular wall stress, fibrosis, and function in right ventricular pressure loading

Right ventricle (RV) pressure loading can lead to RV fibrosis and dysfunction. We previously found increased RV, septal hinge-point and left ventricle (LV) fibrosis in experimental RV pressure loading. However, the relation of RV wall stress to biventricular fibrosis and dysfunction is incompletely defined. Rabbits underwent progressive pulmonary artery banding (PAB) over 3 wk with hemodynamics, echocardiography, and myocardial samples obtained at a terminal experiment at 6 wk. An additional group received PAB and treatment with an endothelin receptor antagonist. The endocardial and epicardial borders of short-axis echo images were traced and analyzed with invasive pressures to yield regional end-diastolic (ED) and end-systolic (ES) wall stress. To increase clinical translation, computer model-derived wall stress was compared with Laplace wall stress. The relation of wall stress with fibrosis (picrosirius red staining) and ventricular function was analyzed. ED wall stress in all regions and RV and LV free-wall ES wall stress were increased in PAB rabbits versus sham animals. Laplace wall stress correlated well with computational models. In PAB, fibrosis was highest in the RV free wall, then septal hinge regions, and lowest in the septum and LV free wall. Fibrosis was moderately related to ED (r = 0.47, P = 0.0011), but not ES wall stress. RV ED wall stress was strongly related to echo indexes of function (strain rate: r = 0.71, P = 0.048; E', r = -0.75, P = 0.0077; tricuspid annular plane systolic excursion: r = 0.85, P = 0.0038) and RV fractional area change (r = 0.77, P = 0.027). ED, more than ES, wall stress is related moderately to fibrosis and strongly to function in experimental RV pressure loading, especially at the septal hinge-point regions, where fibrosis is prominent. This suggests that wall stress partially links RV pressure loading, fibrosis, and dysfunction and may be useful to follow clinically.NEW & NOTEWORTHY Biventricular fibrosis and dysfunction impact outcomes in RV pressure loading, but their relation to wall stress is poorly defined. Using a pulmonary artery band rabbit model, we entered echocardiography and catheter data into a computer model to yield regional end-diastolic (EDWS) and end-systolic (ESWS) wall stress. EDWS, more than ESWS, correlated with fibrosis and dysfunction, especially at the fibrosis-intense septal hinge-point regions. Thus, wall stress may be clinically useful in linking RV pressure loading to regional fibrosis and dysfunction.

Marine omega-3 highly unsaturated fatty acids: From mechanisms to clinical implications in heart failure and arrhythmias

Therapeutic implications of marine omega-3 highly unsaturated fatty acids (HUFA) in cardiovascular disease are still discussed controversially. Several clinical trials report divergent findings and thus leave ambiguity on the meaning of oral omega-3 therapy. Potential prognostic indications of HUFA treatment have been predominantly studied in coronary artery disease, sudden cardiac death, ventricular arrhythmias, atrial fibrillation and heart failure of various origin. It is suspected that increased ventricular wall stress is crucially involved in the prognosis of heart failure. Increased wall stress and an unfavorable myocardial remodeling is associated with an increased risk of arrhythmias by stretch-activated membrane ion channels. Integration of HUFA into the microenvironment of cardiomyocyte ion channels lead to allosteric changes and increase the electrical stability. Increased ventricular wall stress appears to be involved in the local myocardial as well as in the hepatic fatty acid metabolism, i.e. a cardio-hepatic syndrome. Influences of an altered endogenous HUFA metabolism and an inverse shift of the fatty acid profile was underrated in the past. A better understanding of these interacting endogenous mechanisms appears to be required for interpreting the findings of recent experimental and clinical studies. The present article critically reviews major studies on basic pathophysiological mechanisms and treatment effects in clinical trials.

MR, CT, and PET imaging in pericardial disease

Although echocardiography remains the standard diagnostic tool for identifying pericardial diseases, procedures with better delineation of morphology and heart function are often required. The pericardium consists of an inner visceral (epicardium) and outer parietal layer (pericardium), which constitute for the pericardial cavity. Pericardial effusion can occur as transudate, exudate, pyopneumopericardium, or hemopericardium. Potential causes are inflammatory processes, that is, pericarditis due to autoimmune or infective reasons, neoplasms, irradiation, or systemic disorders, chronic renal failure, endocrine, or metabolic diseases. Pericardial fat can mimic pericardial effusion. Using various image-acquisition sequences, MRI allows identifying and separating fluid and solid structures. Fast spin-echo T1-weighted sequences with black-blood preparation are favourably used for morphological evaluation. Fast spin-echo T2-weighted sequences, particularly with fat saturation, and short-tau inversion-recovery sequences are useful to visualize oedema and inflammation. For further tissue characterization, delayed inversion-recovery imaging is used. Therefore, image acquisition is performed at 5-20 min subsequent to contrast agent administration, the so-called technique of late gadolinium enhancement. Ventricular volumes and myocardial mass can be assessed accurately by steady-state free-precession sequences, which is required to measure cardiac function and ventricular wall stress. Constrictive pericarditis usually results from chronic inflammatory processes leading to increased stiffness, which impedes the slippage of both pericardial layers and thereby the normal cardiac filling. CT imaging can favourably assess pericardial calcification. Thus, MR and CT imaging allow a comprehensive delineation of the pericardium. Superior to echocardiography, both methods provide a larger field of view and depiction of the complete chest including abnormalities of the surrounding mediastinum and lungs. PET provides unique information on the in vivo metabolism of 18-fluorodeoxyglucose that can be superimposed on CT findings and is useful for identifying inflammatory processes or masses, for example neoplasms. These imaging techniques provide advanced information of anatomy and cardiac function to optimize the pericardial access, for example by the AttachLifter system, for diagnosis and treatment.

Predictors and prevention of diabetic cardiomyopathy

Despite our cognizance that diabetes can enhance the chances of heart failure, causes multiorgan failure,and contributes to morbidity and mortality, it is rapidly increasing menace worldwide. Less attention has been paid to alert prediabetics through determining the comprehensive predictors of diabetic cardiomyopathy (DCM) and ameliorating DCM using novel approaches. DCM is recognized as asymptomatic progressing structural and functional remodeling in the heart of diabetics, in the absence of coronary atherosclerosis and hypertension. The three major stages of DCM are: (1) early stage, where cellular and metabolic changes occur without obvious systolic dysfunction; (2) middle stage, which is characterized by increased apoptosis, a slight increase in left ventricular size, and diastolic dysfunction and where ejection fraction (EF) is <50%; and (3) late stage, which is characterized by alteration in microvasculature compliance, an increase in left ventricular size, and a decrease in cardiac performance leading to heart failure. Recent investigations have revealed that DCM is multifactorial in nature and cellular, molecular, and metabolic perturbations predisposed and contributed to DCM. Differential expression of microRNA (miRNA), signaling molecules involved in glucose metabolism, hyperlipidemia, advanced glycogen end products, cardiac extracellular matrix remodeling, and alteration in survival and differentiation of resident cardiac stem cells are manifested in DCM. A sedentary lifestyle and high fat diet causes obesity and this leads to type 2 diabetes and DCM. However, exercise training improves insulin sensitivity, contractility of cardiomyocytes, and cardiac performance in type 2 diabetes. These findings provide new clues to diagnose and mitigate DCM. This review embodies developments in the field of DCM with the aim of elucidating the future perspectives of predictors and prevention of DCM.

Diabetic cardiomyopathy--fact or fiction?

Epidemiologic as well as clinical studies confirm the close link between diabetes mellitus and heart failure. Diabetic cardiomyopathy (DCM) is still a poorly understood "entity", however, with several contributing pathogenetic factors which lead in different stages of diabetes to characteristic clinical phenotypes. Hyperglycemia with a shift from glucose metabolism to increased beta-oxidation and consecutive free fatty acid damage (lipotoxicity) to the myocardium, insulin resistance, renin-angiotensin-aldosterone system (RAAS) activation, altered calcium homeostasis and structural changes from the natural collagen network to a stiffer matrix due to advanced glycation endproduct (AGE) formation, hypertrophy and fibrosis contribute to the respective clinical phenotypes of DCM. We propose the following classification of cardiomyopathy in diabetic patients: a) Diastolic heart failure with normal ejection fraction (HFNEF) in diabetic patients often associated with hypertrophy without relevant hypertension. Relevant coronary artery disease (CAD), valvular disease and uncontrolled hypertension are not present. This is referred to as stage 1 DCM. b) Systolic and diastolic heart failure with dilatation and reduced ejection (HFREF) in diabetic patients excluding relevant CAD, valvular disease and uncontrolled hypertension as stage 2 DCM. c) Systolic and/or diastolic heart failure in diabetic patients with small vessel disease (microvascular disease) and/or microbial infection and/or inflammation and/or hypertension but without CAD as stage 3 DCM. d) If heart failure may also be attributed to infarction or ischemia and remodeling in addition to stage 3 DCM the term should be heart failure in diabetes or stage 4 DCM. These clinical phenotypes of diabetic cardiomyopathy can be separated by biomarkers, non-invasive (echocardiography, cardiac magnetic resonance imaging) and invasive imaging methods (levocardiography, coronary angiography) and further analysed by endomyocardial biopsy for concomitant viral infection. The role of specific diabetic drivers to the clinical phenotypes, to macro- and microangiopathy as well as accompanying risk factors or confounders, e.g. hypertension, autoimmune factors or inflammation with or without viral persistence, need to be identified in each individual patient separately. Thus hyperglycemia, hyperinsulinemia and insulin resistance as well as lipotoxicity by free fatty acids (FFAs) are the factors responsible for diabetic cardiomyopathy. In stage 1 and 2 DCM diabetic cardiomyopathy is clearly a fact. However, precise determination of to what degree the various underlying pathogenetic processes are responsible for the overall heart failure phenotype remains a fiction.

Intrapericardial procedures for cardiac regeneration by stem cells: need for minimal invasive access (AttachLifter) to the normal pericardial cavity

In view of the only modest functional and anatomical improvements achieved by bone marrow-derived cell transplantation in patients with heart disease, the question was addressed whether the intracoronary, transcoronary-venous, and intramyocardial delivery routes are adequate. It is hypothesized that an intrapericardial delivery of stem cells or activators of resident cardiac stem cells increases therapeutic benefits. From such an intrapericardial depot, cells or modulating factors, such as thymosin β4 or Ac-SDKP, are expected to reach the myocardium with sustained kinetics. Novel tools which provide access to the pericardial space even in the absence of pericardial effusion are, therefore, described. When the pericardium becomes attached to the suction head (monitored by an increase in negative pressure), the pericardium is lifted from the epicardium ("AttachLifter"). The opening of the suction head ("Attacher") is narrowed by flexible clamps which grab the tissue and improve the vacuum seal in the case of uneven tissue. A ridge, i.e.,"needle guidance", on the suction head excludes injury to the epicardium, whereby the pericardium is punctured by a needle which resides outside the suction head. A fiberscope can be used to inspect the pericardium prior to puncture. Based on these procedures, the role of the pericardial space and the presence of pericardial effusion in cardiac regeneration can be assessed.

Association of hyperhomocysteinemia with left ventricular dilatation and mass in human heart

BACKGROUND

Hyperhomocysteinemia is a risk factor for ischemic heart disease. Several other mechanisms apply also to dilative types of heart failure of various, non-ischemic etiologies. We hypothesized that hyperhomocysteinemia is associated with left ventricular (LV) dilatation and hypertrophy in dilative cardiomyopathy.

METHODS

Homocysteine was measured in 66 individuals with suspected cardiomyopathy. Cardiac magnetic resonance imaging was used to assess LV volume, mass, and wall stress.

RESULTS

Hyperhomocysteinemia (> 12 micromol/L) was found in 45 patients (68%). LV mass was greater in these patients compared with individuals with normal homocysteine (83+/-27 vs. 67+/-19 g/m(2); p<0.02). Homocysteine was increased in patients with increased brain natriuretic peptide > or = 100 pg/mL (18.3+/-5.9 vs. 14.9+/-5.1 micromol/L; p=0.018). LV mass, LV end-diastolic and end-systolic volume (LVEDV, LVESV) were significantly increased in individuals in the upper quartile compared with the lower quartile (90+/-25 vs. 65+/-18 g/m(2), p=0.021; 114+/-50 vs. 71+/-23 mL/m(2), p=0.042; 76+/-51 vs. 36+/-22 mL/m(2), p=0.045). LV dilatation (LVEDV > or = 90 mL/m(2)) was more common in hyperhomocysteinemia (> 12 micromol/L, p=0.0166). Normalized LV mass was correlated with homocysteine (r=0.346, p=0.065). Homocysteine was not significantly correlated with LVEDV (r=0.229, p=0.065), LV end-diastolic wall stress (r=0.226, p=0.069) and LV ejection fraction.

CONCLUSIONS

Hyperhomocysteinemia appears to be, at least in part, involved in a disproportional LV dilatation, where the ensuing hypertrophy is not sufficient to compensate for the increased wall stress. A potential mechanism is the hyperhomocysteinemia associated increase in oxidative stress that favors muscle fiber slippage.

Protein NMR in biomedical research

Nuclear magnetic resonance (NMR) spectroscopy is a versatile biophysical technique with wide applicability in drug discovery research, particularly for the detection and characterization of molecular interactions. This review highlights in a comprehensive manner the aspects of biomolecular NMR which are most beneficial for pharmaceutical research and presents them as contributions to the different stages of a drug discovery program: target selection, assay development, lead generation and lead optimization. Emphasis is put on the concept of the particular NMR application, rather than on technical details, and on recent examples. Finally, an appendix of frequently asked questions is given.