Catalin F. Baicu

Left Ventricular Systolic Performance, Function, and Contractility in Patients With Diastolic Heart Failure

Background—Patients with diastolic heart failure (DHF) have significant abnormalities in left ventricular (LV) diastolic function, including slow and delayed relaxation and increased chamber stiffness. Whether and to what extent these abnormalities in diastolic function occur in association with abnormalities in LV systolic performance, function, and contractility has not been investigated thoroughly. Methods and Results—The systolic properties of the LV were examined in 75 patients with heart failure and a normal ejection fraction (ie, DHF) and 75 normal control subjects with no evidence of cardiovascular disease. LV systolic properties were assessed with echocardiographic and cardiac catheterization data. Stroke work (an index of LV systolic performance), preload recruitable stroke work and ejection fraction (indices of LV systolic function), systolic stress-shortening relationship, end-systolic pressure-volume relationship, and peak (+)dP/dt (indices of LV contractility) were examined. The systolic properties of the LV were normal in patients with DHF. Stroke work was 8.4±2.3 in DHF versus 8.8±2.5 kg · cm in controls (P=0.26). Preload recruitable stroke work was 99±22 in DHF versus 109±18 g/cm2 in controls (P=0.13). The relationship between stroke work and end-diastolic volume was similar in DHF and controls. Peak (+) dP/dt was 1596±362 in DHF versus 1664±305 mm Hg/s in controls (P=0.54). The end-systolic pressure-volume relationship was increased in DHF. The systolic stress versus endocardial fractional shortening relationship was similar in DHF and controls. Conclusions—Patients with DHF had normal LV systolic performance, function, and contractility. The pathophysiology of DHF does not appear to be related to significant abnormalities in these systolic properties of the LV.

Prevalence and Significance of Alterations in Cardiac Structure and Function in Patients With Heart Failure and a Preserved Ejection Fraction

Background— The purpose of this study was to examine the prevalence of abnormalities in cardiac structure and function present in patients with heart failure and a preserved ejection fraction (HFPEF) and to determine whether these alterations in structure and function were associated with cardiovascular morbidity and mortality. Methods and Results— The Irbesartan in HFPEF trial (I-PRESERVE) enrolled 4128 patients; echocardiographic determination of left ventricular (LV) volume, mass, left atrial (LA) size, systolic function, and diastolic function were made at baseline in 745 patients. The primary end point was death or protocol-specific cardiovascular hospitalization. A secondary end point was the composite of heart failure death or heart failure hospitalization. Associations between baseline structure and function and patient outcomes were examined using univariate and multivariable Cox proportional hazard analyses. In this substudy, LV hypertrophy or concentric remodeling was present in 59%, LA enlargement was present in 66%, and diastolic dysfunction was present in 69% of the patients. Multivariable analyses controlling for 7 clinical variables (including log N-terminal pro-B–type natriuretic peptide) indicated that increased LV mass, mass/volume ratio, and LA size were independently associated with an increased risk of both primary and heart failure events (all P<0.05). Conclusions— Left ventricular hypertrophy or concentric remodeling, LA enlargement, and diastolic dysfunction were present in the majority of patients with HFPEF. Left ventricular mass and LA size were independently associated with an increased risk of morbidity and mortality. The presence of structural remodeling and diastolic dysfunction may be useful additions to diagnostic criteria and provide important prognostic insights in patients with HFPEF. Clinical Trial Registration— http://www.clinicaltrials.gov. Unique identifier: NCT00095238.

Myocardial Stiffness in Patients With Heart Failure and a Preserved Ejection Fraction Contributions of Collagen and Titin

Background— The purpose of this study was to determine whether patients with heart failure and a preserved ejection fraction (HFpEF) have an increase in passive myocardial stiffness and the extent to which discovered changes depend on changes in extracellular matrix fibrillar collagen and cardiomyocyte titin. Methods and Results— Seventy patients undergoing coronary artery bypass grafting underwent an echocardiogram, plasma biomarker determination, and intraoperative left ventricular epicardial anterior wall biopsy. Patients were divided into 3 groups: referent control (n=17, no hypertension or diabetes mellitus), hypertension (HTN) without (–) HFpEF (n=31), and HTN with (+) HFpEF (n=22). One or more of the following studies were performed on the biopsies: passive stiffness measurements to determine total, collagen-dependent and titin-dependent stiffness (differential extraction assay), collagen assays (biochemistry or histology), or titin isoform and phosphorylation assays. In comparison with controls, patients with HTN(–)HFpEF had no change in left ventricular end-diastolic pressure, myocardial passive stiffness, collagen, or titin phosphorylation but had an increase in biomarkers of inflammation (C-reactive protein, soluble ST2, tissue inhibitor of metalloproteinase 1). In comparison with both control and HTN(–)HFpEF, patients with HTN(+)HFpEF had increased left ventricular end-diastolic pressure, left atrial volume, N-terminal propeptide of brain natriuretic peptide, total, collagen-dependent, and titin-dependent stiffness, insoluble collagen, increased titin phosphorylation on PEVK S11878(S26), reduced phosphorylation on N2B S4185(S469), and increased biomarkers of inflammation. Conclusions— Hypertension in the absence of HFpEF did not alter passive myocardial stiffness. Patients with HTN(+)HFpEF had a significant increase in passive myocardial stiffness; collagen-dependent and titin-dependent stiffness were increased. These data suggest that the development of HFpEF depends on changes in both collagen and titin homeostasis.

Plasma Biomarkers That Reflect Determinants of Matrix Composition Identify the Presence of Left Ventricular Hypertrophy and Diastolic Heart Failure

Background— Chronic pressure overload (such as arterial hypertension) may cause left ventricular (LV) remodeling, alterations in cardiac function, and the development of diastolic heart failure. Changes in the composition of the myocardial extracellular matrix may contribute to the development of pressure-overload–induced LV remodeling. We hypothesized that a specific pattern of plasma biomarker expression that reflected changes in these pathophysiological mechanisms would have diagnostic application to identify (1) patients who have development of LV hypertrophy (LVH) and (2) patients with LVH who have development of diastolic heart failure. Methods and Results— Plasma concentration of 17 biomarkers (matrix metalloproteinase [MMP]-1, -2, -3, -7, -8, and -9; tissue inhibitors -1, -2, -3, and -4; N-terminal propeptide of brain natriuretic peptide (NT-proBNP); cardiotrophin; osteopontin; soluble receptor for advanced glycation end products; collagen I teleopeptide; collagen I NT-proBNP; and collagen III N-terminal propetide [PIIINP]), an echocardiogram, and 6-minute hall walk were performed on 241 referent control subjects, 144 patients with LVH but no evidence of heart failure, and 61 patients with LVH and diastolic heart failure (DHF). A plasma multibiomarker panel consisting of increased MMP-7, MMP-9, TIMP-1, PIIINP, and NT-proBNP predicted the presence of LVH with an area under the curve of 0.80. A plasma multibiomarker panel consisting of increased MMP-2, TIMP-4, PIIINP, and decreased MMP-8 predicted the presence of DHF with an area under the curve of 0.79. These multibiomarker panels performed better than any single biomarker including NT-proBNP and better than using clinical covariates alone (area under the curve, 0.73 for LVH and 0.68 for DHF). Conclusions— Plasma biomarkers reflecting changes in extracellular matrix fibrillar collagen homeostasis, combined into a multibiomarker panel, have discriminative value in identifying the presence of structural remodeling (LVH) and clinical disease (DHF).

Ceramide synthase 5 mediates lipid-induced autophagy and hypertrophy in cardiomyocytes

Diabetic cardiomyopathy (DbCM), which consists of cardiac hypertrophy and failure in the absence of traditional risk factors, is a major contributor to increased heart failure risk in type 2 diabetes patients. In rodent models of DbCM, cardiac hypertrophy and dysfunction have been shown to depend upon saturated fatty acid (SFA) oversupply and de novo sphingolipid synthesis. However, it is not known whether these effects are mediated by bulk SFAs and sphingolipids or by individual lipid species. In this report, we demonstrate that a diet high in SFA induced cardiac hypertrophy, left ventricular systolic and diastolic dysfunction, and autophagy in mice. Furthermore, treatment with the SFA myristate, but not palmitate, induced hypertrophy and autophagy in adult primary cardiomyocytes. De novo sphingolipid synthesis was required for induction of all pathological features observed both in vitro and in vivo, and autophagy was required for induction of hypertrophy in vitro. Finally, we implicated a specific ceramide N-acyl chain length in this process and demonstrated a requirement for (dihydro)ceramide synthase 5 in cardiomyocyte autophagy and myristate-mediated hypertrophy. Thus, this report reveals a requirement for a specific sphingolipid metabolic route and dietary SFAs in the molecular pathogenesis of lipotoxic cardiomyopathy and hypertrophy.

Age-dependent alterations in fibrillar collagen content and myocardial diastolic function: role of SPARC in post-synthetic procollagen processing

Advanced age, independent of concurrent cardiovascular disease, can be associated with increased extracellular matrix (ECM) fibrillar collagen content and abnormal diastolic function. However, the mechanisms causing this left ventricular (LV) remodeling remain incompletely defined. We hypothesized that one determinant of age-dependent remodeling is a change in the extent to which newly synthesized procollagen is processed into mature collagen fibrils. We further hypothesized that secreted protein acidic and rich in cysteine (SPARC) plays a key role in the changes in post-synthetic procollagen processing that occur in the aged myocardium. Young (3 mo old) and old (18-24 mo old) wild-type (WT) and SPARC-null mice were studied. LV collagen content was measured histologically by collagen volume fraction, collagen composition was measured by hydroxyproline assay as soluble collagen (1 M NaCl extractable) versus insoluble collagen (mature cross-linked), and collagen morphological structure was examined by scanning electron microscopy. SPARC expression was measured by immunoblot analysis. LV and myocardial structure and function were assessed using echocardiographic and papillary muscle experiments. In WT mice, advanced age increased SPARC expression, myocardial diastolic stiffness, fibrillar collagen content, and insoluble collagen. In SPARC-null mice, advanced age also increased myocardial diastolic stiffness, fibrillar collagen content, and insoluble collagen but significantly less than those seen in WT old mice. As a result, insoluble collagen and myocardial diastolic stiffness were lower in old SPARC-null mice (1.36 +/- 0.08 mg hydroxyproline/g dry wt and 0.04 +/- 0.005) than in old WT mice (1.70 +/- 0.10 mg hydroxyproline/g dry wt and 0.07 +/- 0.005, P < 0.05). In conclusion, the absence of SPARC reduced age-dependent alterations in ECM fibrillar collagen and diastolic function. These data support the hypothesis that SPARC plays a key role in post-synthetic procollagen processing and contributes to the increase in collagen content found in the aged myocardium.

Pressure Overload–Induced Alterations in Fibrillar Collagen Content and Myocardial Diastolic Function Role of Secreted Protein Acidic and Rich in Cysteine (SPARC) in Post–Synthetic Procollagen Processing

Background— Chronic pressure overload causes myocardial hypertrophy, increased fibrillar collagen content, and abnormal diastolic function. We hypothesized that one determinant of these pressure overload–induced changes is the extracellular processing of newly synthesized procollagen into mature collagen fibrils. We further hypothesized that secreted protein acidic and rich in cysteine (SPARC) plays a key role in post–synthetic procollagen processing in normal and pressure-overloaded myocardium. Methods and Results— To determine whether pressure overload–induced changes in collagen content and diastolic function are affected by the absence of SPARC, age-matched wild-type (WT) and SPARC-null mice underwent either transverse aortic constriction (TAC) for 4 weeks or served as nonoperated controls. Left ventricular (LV) collagen content was measured histologically by collagen volume fraction, collagen composition was measured by hydroxyproline assay as soluble collagen (1 mol/L NaCl extractable) versus insoluble collagen (mature cross-linked collagen), and collagen morphological structure was examined by scanning electron microscopy. SPARC expression was measured by immunoblot. LV, myocardial, and cardiomyocyte structure and function were assessed by echocardiographic, papillary muscle, and isolated cardiomyocyte studies. In WT mice, TAC increased LV mass, SPARC expression, myocardial diastolic stiffness, fibrillar collagen content, and soluble and insoluble collagen. In SPARC-null mice, TAC increased LV mass to an extent similar to WT mice. In addition, in SPARC-null mice, TAC increased fibrillar collagen content, albeit significantly less than that seen in WT TAC mice. Furthermore, the proportion of LV collagen that was insoluble was less in the SPARC-null TAC mice (86±2%) than in WT TAC mice (99±2%, P<0.05), and the proportion of collagen that was soluble was greater in the SPARC-null TAC mice (14±2%) than in WT TAC mice (1±2%, P<0.05) As a result, myocardial diastolic stiffness was lower in SPARC-null TAC mice (0.075±0.005) than in WT TAC mice (0.045±0.005, P<0.05). Conclusions— The absence of SPARC reduced pressure overload–induced alterations in extracellular matrix fibrillar collagen and diastolic function. These data support the hypothesis that SPARC plays a key role in post–synthetic procollagen processing and the development of mature cross-linked collagen fibrils in normal and pressure-overloaded myocardium.

Cardiac extracellular matrix remodeling: Fibrillar collagens and Secreted Protein Acidic and Rich in Cysteine (SPARC)

The cardiac interstitium is a unique and adaptable extracellular matrix (ECM) that provides a milieu in which myocytes, fibroblasts, and endothelial cells communicate and function. The composition of the ECM in the heart includes structural proteins such as fibrillar collagens and matricellular proteins that modulate cell:ECM interaction. Secreted Protein Acidic and Rich in Cysteine (SPARC), a collagen-binding matricellular protein, serves a key role in collagen assembly into the ECM. Recent results demonstrated increased cardiac rupture, dysfunction and mortality in SPARC-null mice in response to myocardial infarction that was associated with a decreased capacity to generate organized, mature collagen fibers. In response to pressure overload induced-hypertrophy, the decrease in insoluble collagen incorporation in the left ventricle of SPARC-null hearts was coincident with diminished ventricular stiffness in comparison to WT mice with pressure overload. This review will focus on the role of SPARC in the regulation of interstitial collagen during cardiac remodeling following myocardial infarction and pressure overload with a discussion of potential cellular mechanisms that control SPARC-dependent collagen assembly in the heart.

A Novel Tubular Scaffold for Cardiovascular Tissue Engineering

We have developed a counter rotating cone extrusion device to produce the next generation of three-dimensional collagen scaffold for tissue engineering. The device can produce a continuously varying fibril angle from the lumen to the outside of a 5-mm-diameter collagen tube, similar to the pattern of heart muscle cells in the intact heart. Our scaffold is a novel, oriented, type I collagen, tubular scaffold. We selected collagen because we believe there are important signals from the collagen both geometrically and biochemically that elicit the in vivo -like phenotypic response from the cardiomyocytes. We have shown that cardiomyocytes can be cultured in these tubes and resemble an in vivo phenotype. This new model system will provide important information leading to the design and construction of a functional, biologically based assist device.

Quantification of Protein Expression Changes in the Aging Left Ventricle of Rattus norvegicus

As the heart ages, electrophysiological and biochemical changes can occur, and the ventricle in many cases loses distensibility, impairing diastolic function. How the proteomic signature of the aged ventricle is unique in comparison to young hearts is still under active investigation. We have undertaken a quantitative proteomics study of aging left ventricles (LVs) utilizing the isobaric Tagging for Relative and Absolute Quantification (iTRAQ) methodology. Differential protein expression was observed for 117 proteins including proteins involved in cell signaling, the immune response, structural proteins, and proteins mediating responses to oxidative stress. For many of these proteins, this is the first report of an association with the aged myocardium. Additionally, two proteins of unknown function were identified. This work serves as the basis for making future comparisons of the aged left ventricle proteome to that of left ventricles obtained from other models of disease and heart failure.