Versican accumulation drives Nos2 induction and aortic disease in Marfan syndrome via Akt activation

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening condition associated with Marfan syndrome (MFS), a disease caused by fibrillin-1 gene mutations. While various conditions causing TAAD exhibit aortic accumulation of the proteoglycans versican (Vcan) and aggrecan (Acan), it is unclear whether these ECM proteins are involved in aortic disease. Here, we find that Vcan, but not Acan, accumulated in Fbn1C1041G/+ aortas, a mouse model of MFS. Vcan haploinsufficiency protected MFS mice against aortic dilation, and its silencing reverted aortic disease by reducing Nos2 protein expression. Our results suggest that Acan is not an essential contributor to MFS aortopathy. We further demonstrate that Vcan triggers Akt activation and that pharmacological Akt pathway inhibition rapidly regresses aortic dilation and Nos2 expression in MFS mice. Analysis of aortic tissue from MFS human patients revealed accumulation of VCAN and elevated pAKT-S473 staining. Together, these findings reveal that Vcan plays a causative role in MFS aortic disease in vivo by inducing Nos2 via Akt activation and identify Akt signaling pathway components as candidate therapeutic targets.

Balance shift of activin/inhibin cytokines as part of the atrial structural remodelling of patients with aortic stenosis in atrial fibrillation

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto Salud Carlos III

Fondos Feder

INNVAL 18/20

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia, particularly in aortic stenosis (AS) patients. AF increases the risk of embolic stroke, heart failure, and mortality. The pathophysiological substrate for persistent AF is atrial fibrosis. Key players of fibrosis homeostasis are cytokines of the transforming growth factor-β (TFG-β) superfamily. In particular, dysregulation towards upregulating profibrotic TGF-β signalling versus antifibrotic bone morphogenetic protein 7 (BMP7) may result in pathological atrial remodelling and AF development in AS patients. However, the role of activins/inhibins in the clinical pathogenesis and vulnerability to AF remains unknown. In contrast to activins, inhibins do not signal directly but function by antagonizing activin signalling.

Purpose

To assess the contribution of activin A [homodimer of inhibin βA (INHβA)] and inhibin A [heterodimer of INHβA and inhibin α (INHα)] to the arrhythmogenic atrial remodelling and AF in AS patients.

Methods

The study was performed with intraoperative biopsies of the right atrium (RA) obtained from AS patients with AF (n=23) or sinus rhythm (SR) (n=23), matched for sex, age and systolic function. The specificity of the findings was validated in AF patients (n=10) without AS. mRNA (qPCR) and protein (co-immunoprecipitation and western blot) were quantified in  RA. Stepwise multiple logistic regression analysis was used to identify predictors of AF, including as independent variables the transcript levels of TGF-β family members and remodelling-related elements.

Results

INHβA and INHα transcripts were downregulated in the RA of AF compared to SR patients (INHβA: 0.52±0.1 vs 0.99±0.1**; INHα: 0.16±0.03 vs 0.59±0.1***). The fraction of INHβA protein co-immunoprecipitated with an antibody to INHα showed lower levels in AF than in SR patients (0.83±0.03 vs 1.21±0.09*). On the other hand, in the fraction of unbound proteins, INHβA did not differ between SR and AF patients. These results suggest that the INHβA subunits coupled into the antagonistic dimer inhibin A were downregulated in the RA from AS patients with AF.

Logistic regression analysis shows that RA transcript levels of TGF-ß1 (B=1.34) and COL1A1 (B=0.39) constituted significant positive predictors of AF, whereas INHβA (B=-6.8) and BMP-7 (B=-0.92) were significant negative predictors. A ROC analysis confirmed the accuracy of the model and yielded an area under the curve of 0.93 (CI 95% 0.86 to 1, ***). In addition, the variables determined as significant to predict presence of AF in patients with AS, did not constitute significant predictors of AF in patients with no LV pressure overload.

Conclusion

Our results provide new insights into a change in the balance between activin and inhibin cytokines in the atrial tissue that may have a pathogenetic role in the appearance of atrial fibrillation in valvular AS patients.

Activation of bone morphogenetic protein type 1A receptors (BMPR1A) by THR184 halts the progression of the left ventricular remodelling under pressure overload

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by grants from Spain´s Ministerio de Economía y Competitividad [(PI18/00543, CIBERCV (CB16/11/00264), co-funded by Fondo Europeo de Desarrollo Regional (FEDER)]; Instituto de Investigación Sanitaria Marqués de Valdecilla, IDIVAL (INNVAL18/20; PREVAL18/03); Grants4Targets from BAYER AG (ID 2017-03-2088).

Background

Aortic valve stenosis (AS) confronts the left ventricle (LV) with a progressive pressure overload that leads to myocardial remodelling (hypertrophy and fibrosis) and ultimately to heart failure. BMP7, through BMPR1A-mediated pSMAD1/5/(8)9 signalling, protects the LV against maladaptive remodelling. Small BMP-based molecules for therapeutic applications are gaining momentum in different clinical fields. A synthetic peptide agonist of BMPR1A, THR184, has been reported to prevent and reverse experimental renal fibrotic processes.

Purpose

To assess the potential of THR184 to halt or reverse the LV pathological remodelling induced by pressure overload in mice and evaluate the mechanisms involved in cultured cells.

Methods and Results

Mice subjected to a 4-week transverse aortic constriction (TAC) period received daily i.p injections of THR184 (n=9) (5µg/g) or saline (n=10) during the 3rd and 4th weeks after TAC, when LV remodelling was already ongoing. LV morphology and function were assessed by echocardiography. LV samples were analysed by qPCR and Western blot. THR184 halted the LV morpho-functional deterioration developed four weeks after TAC as compared to the saline group: [LV mass: THR184, 3.74±0.27 mg vs saline, 4.44±0.71 mg*; long-axis systolic function (MAPSE): THR184, 0.60±0.04 mm vs saline, 0.49±0.06 mm*; LV filling pressures (E/e’): THR184, 36.92±5.41 vs saline, 58.41±19.34**]. Moreover, THR184 partially reverted LV dysfunction, both systolic (MAPSE: 4 wk, 0.60±0.04 mm vs 2 wk, 0.49±0.03 mm***) and diastolic (E/e’: 4 wk, 36.92±5.41 vs 2 wk, 46.87±10.04*). The myocardial overexpression of the remodelling-related genes induced by TAC was attenuated by THR184 compared to saline: [Collagen I (Col I): THR184, 6.77±1.72 vs saline, 14.61±1.94 ***); β myosin heavy chain (β-MHC): THR184, 3.08±1.52 vs saline, 5.67±1.14*]. The expression of pSMAD1/5/(8)9 was reduced in saline-treated TAC mice (TAC, 0.67±0.09 vs sham, 1.04±0.05*), while it was rescued in THR184-treated TAC mice (THR184, 1.11±0.14 vs saline, 0.67±0.09**). In cultured cells, THR184 reduced TGF-β1-mediated transcriptional activation of Col I in 3T3 fibroblasts (THR184, 2.40±0.45 vs TGF-β1, 4.34±0.55***) and β-MHC in H9C2 cardiomyocytes (THR184, 1.02±0.38 vs TGF-β1, 4.10±1.56*). The involvement of BMPR1A in the effects of THR184 was supported by the antagonism with LDN or DMH2.

Conclusion

THR184 activated BMPR1A signalling through pSMAD1/5/(8)9 to halt the maladaptive remodelling of the LV by counteracting TGF-β1-mediated pro-fibrotic and pro-hypertrophic actions. We provide a preclinical proof-of-concept on THR184, a BMP7-based BMPR1A agonist, to treat the deleterious consequences of LV pressure overload.

BMP7-based peptide agonists of BMPR1A protect the left ventricle against pathological remodeling induced by pressure overload

Aortic stenosis (AS) exposes the left ventricle (LV) to pressure overload leading to detrimental LV remodeling and heart failure. In animal models of cardiac injury or hemodynamic stress, bone morphogenetic protein-7 (BMP7) protects LV against remodeling by counteracting TGF-β effects. BMP receptor 1A (BMPR1A) might mediate BMP7 antifibrotic effects. Herein we evaluated BMP7-based peptides, THR123 and THR184, agonists of BMPR1A, as cardioprotective drugs in a pressure overload model. We studied patients with AS, mice subjected to four-week transverse aortic constriction (TAC) and TAC release (de-TAC). The LV of AS patients and TAC mice featured Bmpr1a downregulation. Also, pSMAD1/5/(8)9 was reduced in TAC mice. Pre-emptive treatment of mice with THR123 and THR184, during the four-week TAC period, normalized pSMAD1/5/(8)9 levels in the LV, attenuated overexpression of remodeling-related genes (Col 1α1, β-MHC, BNP), palliated structural damage (hypertrophy and fibrosis) and alleviated LV dysfunction (systolic and diastolic). THR184 administration, starting fifteen days after TAC, halted the ongoing remodeling and partially reversed LV dysfunction. The reverse remodeling after pressure overload release was facilitated by THR184. Both peptides diminished the TGF-β1-induced hypertrophic gene program in cardiomyocytes, collagen transcriptional activation in fibroblasts, and differentiation of cardiac fibroblasts to myofibroblasts. Molecular docking suggests that both peptides bind with similar binding energies to the BMP7 binding domain at the BMPR1A. The present study results provide a preclinical proof-of-concept of potential therapeutic benefits of BMP7-based small peptides, which function as agonists of BMPR1A, against the pathological LV remodeling in the context of aortic stenosis.

Sirtuins: To Be or Not To Be in Diabetic Cardiomyopathy

Diabetic cardiomyopathy is the leading cause of death among people with diabetes. Despite its severity and poor prognosis, there are currently no approved specific drugs to prevent or even treat diabetic cardiomyopathy. There is a need to understand the pathogenic mechanisms underlying the development of diabetic cardiomyopathy to design new therapeutic strategies. These mechanisms are complex and intricate and include metabolic dysregulation, inflammation, oxidative stress, fibrosis, and apoptosis. Sirtuins, a group of deacetylase enzymes, play an important role in all these processes and are, therefore, potential molecular targets for treating this disease. In this review, we discuss the role of sirtuins in the heart, focusing on their contribution to the pathogenesis of diabetic cardiomyopathy and how their modulation could be therapeutically useful.

Extracellular Tuning of Mitochondrial Respiration Leads to Aortic Aneurysm

Supplemental Digital Content is available in the text.

Background:

Marfan syndrome (MFS) is an autosomal dominant disorder of the connective tissue caused by mutations in the FBN1 (fibrillin-1) gene encoding a large glycoprotein in the extracellular matrix called fibrillin-1. The major complication of this connective disorder is the risk to develop thoracic aortic aneurysm. To date, no effective pharmacologic therapies have been identified for the management of thoracic aortic disease and the only options capable of preventing aneurysm rupture are endovascular repair or open surgery. Here, we have studied the role of mitochondrial dysfunction in the progression of thoracic aortic aneurysm and mitochondrial boosting strategies as a potential treatment to managing aortic aneurysms.

Methods:

Combining transcriptomics and metabolic analysis of aortas from an MFS mouse model (Fbn1^c1039g/+) and MFS patients, we have identified mitochondrial dysfunction alongside with mtDNA depletion as a new hallmark of aortic aneurysm disease in MFS. To demonstrate the importance of mitochondrial decline in the development of aneurysms, we generated a conditional mouse model with mitochondrial dysfunction specifically in vascular smooth muscle cells (VSMC) by conditional depleting Tfam (mitochondrial transcription factor A; Myh11-Cre^ERT2Tfam^flox/flox mice). We used a mouse model of MFS to test for drugs that can revert aortic disease by enhancing Tfam levels and mitochondrial respiration.

Results:

The main canonical pathways highlighted in the transcriptomic analysis in aortas from Fbn1^c1039g/+ mice were those related to metabolic function, such as mitochondrial dysfunction. Mitochondrial complexes, whose transcription depends on Tfam and mitochondrial DNA content, were reduced in aortas from young Fbn1^c1039g/+ mice. In vitro experiments in Fbn1-silenced VSMCs presented increased lactate production and decreased oxygen consumption. Similar results were found in MFS patients. VSMCs seeded in matrices produced by Fbn1-deficient VSMCs undergo mitochondrial dysfunction. Conditional Tfam-deficient VSMC mice lose their contractile capacity, showed aortic aneurysms, and died prematurely. Restoring mitochondrial metabolism with the NAD precursor nicotinamide riboside rapidly reverses aortic aneurysm in Fbn1^c1039g/+ mice.

Conclusions:

Mitochondrial function of VSMCs is controlled by the extracellular matrix and drives the development of aortic aneurysm in Marfan syndrome. Targeting vascular metabolism is a new available therapeutic strategy for managing aortic aneurysms associated with genetic disorders.

Experimental modelling of cardiac pressure overload hypertrophy: Modified technique for precise, reproducible, safe and easy aortic arch banding-debanding in mice

Pressure overload left ventricular hypertrophy is a known precursor of heart failure with ominous prognosis. The development of experimental models that reproduce this phenomenon is instrumental for the advancement in our understanding of its pathophysiology. The gold standard of these models is the controlled constriction of the mid aortic arch in mice according to Rockman's technique (RT). We developed a modified technique that allows individualized and fully controlled constriction of the aorta, improves efficiency and generates a reproducible stenosis that is technically easy to perform and release. An algorithm calculates, based on the echocardiographic arch diameter, the intended perimeter at the constriction, and a suture is prepared with two knots separated accordingly. The aorta is encircled twice with the suture and the loop is closed with a microclip under both knots. We performed controlled aortic constriction with Rockman's and the double loop-clip (DLC) techniques in mice. DLC proved superiority in efficiency (mortality and invalid experiments) and more homogeneity of the results (transcoarctational gradients, LV mass, cardiomyocyte hypertrophy, gene expression) than RT. DLC technique optimizes animal use and generates a consistent and customized aortic constriction with homogeneous LV pressure overload morphofunctional, structural, and molecular features.

Selective inhibition of plasma membrane calcium ATPase 4 improves angiogenesis and vascular reperfusion

AIMS

Ischaemic cardiovascular disease is a major cause of morbidity and mortality worldwide. Despite promising results from pre-clinical animal models, VEGF-based strategies for therapeutic angiogenesis have yet to achieve successful reperfusion of ischaemic tissues in patients. Failure to restore efficient VEGF activity in the ischaemic organ remains a major problem in current pro-angiogenic therapeutic approaches. Plasma membrane calcium ATPase 4 (PMCA4) negatively regulates VEGF-activated angiogenesis via inhibition of the calcineurin/NFAT signalling pathway. PMCA4 activity is inhibited by the small molecule aurintricarboxylic acid (ATA). We hypothesize that inhibition of PMCA4 with ATA might enhance VEGF-induced angiogenesis.

METHODS AND RESULTS

We show that inhibition of PMCA4 with ATA in endothelial cells triggers a marked increase in VEGF-activated calcineurin/NFAT signalling that translates into a strong increase in endothelial cell motility and blood vessel formation. ATA enhances VEGF-induced calcineurin signalling by disrupting the interaction between PMCA4 and calcineurin at the endothelial-cell membrane. ATA concentrations at the nanomolar range, that efficiently inhibit PMCA4, had no deleterious effect on endothelial-cell viability or zebrafish embryonic development. However, high ATA concentrations at the micromolar level impaired endothelial cell viability and tubular morphogenesis, and were associated with toxicity in zebrafish embryos. In mice undergoing experimentally-induced hindlimb ischaemia, ATA treatment significantly increased the reperfusion of post-ischaemic limbs.

CONCLUSIONS

Our study provides evidence for the therapeutic potential of targeting PMCA4 to improve VEGF-based pro-angiogenic interventions. This goal will require the development of refined, highly selective versions of ATA, or the identification of novel PMCA4 inhibitors.

p-SMAD2/3 and DICER promote pre-miR-21 processing during pressure overload-associated myocardial remodeling

Transforming growth factor-β (TGF-β) induces miR-21 expression which contributes to fibrotic events in the left ventricle (LV) under pressure overload. SMAD effectors of TGF-β signaling interact with DROSHA to promote primary miR-21 processing into precursor miR-21 (pre-miR-21). We hypothesize that p-SMAD-2 and -3 also interact with DICER1 to regulate the processing of pre-miR-21 to mature miR-21 in cardiac fibroblasts under experimental and clinical pressure overload. The subjects of the study were mice undergoing transverse aortic constriction (TAC) and patients with aortic stenosis (AS). In vitro, NIH-3T3 fibroblasts transfected with pre-miR-21 responded to TGF-β1 stimulation by overexpressing miR-21. Overexpression and silencing of SMAD2/3 resulted in higher and lower production of mature miR-21, respectively. DICER1 co-precipitated along with SMAD2/3 and both proteins were up-regulated in the LV from TAC-mice. Pre-miR-21 was isolated bound to the DICER1 maturation complex. Immunofluorescence analysis revealed co-localization of p-SMAD2/3 and DICER1 in NIH-3T3 and mouse cardiac fibroblasts. DICER1-p-SMAD2/3 protein-protein interaction was confirmed by in situ proximity ligation assay. Myocardial up-regulation of DICER1 constituted a response to pressure overload in TAC-mice. DICER mRNA levels correlated directly with those of TGF-β1, SMAD2 and SMAD3. In the LV from AS patients, DICER mRNA was up-regulated and its transcript levels correlated directly with TGF-β1, SMAD2, and SMAD3. Our results support that p-SMAD2/3 interacts with DICER1 to promote pre-miR-21 processing to mature miR-21. This new TGFβ-dependent regulatory mechanism is involved in miR-21 overexpression in cultured fibroblasts, and in the pressure overloaded LV of mice and human patients.

Circulating levels of miR-133a predict the regression potential of left ventricular hypertrophy after valve replacement surgery in patients with aortic stenosis

Background

Myocardial microRNA‐133a (miR‐133a) is directly related to reverse remodeling after pressure overload release in aortic stenosis patients. Herein, we assessed the significance of plasma miR‐133a as an accessible biomarker with prognostic value in predicting the reversibility potential of LV hypertrophy after aortic valve replacement (AVR) in these patients.

Methods and Results

The expressions of miR‐133a and its targets were measured in LV biopsies from 74 aortic stenosis patients. Circulating miR‐133a was measured in peripheral and coronary sinus blood. LV mass reduction was determined echocardiographically. Myocardial and plasma levels of miR‐133a correlated directly (r=0.46, P<0.001) supporting the myocardium as a relevant source of plasma miR‐133a. Accordingly, a significant gradient of miR‐133a was found between coronary and systemic venous blood. The preoperative plasma level of miR‐133a was higher in the patients who normalized LV mass 1 year after AVR than in those exhibiting residual hypertrophy. Logistic regression analysis identified plasma miR‐133a as a positive predictor of the hypertrophy reversibility after surgery. The discrimination of the model yielded an area under the receiver operator characteristic curve of 0.89 (P<0.001). Multiple linear regression analysis revealed plasma miR‐133a and its myocardial target Wolf‐Hirschhorn syndrome candidate 2/Negative elongation factor A as opposite predictors of the LV mass loss (g) after AVR.

Conclusions

Preoperative plasma levels of miR‐133a reflect their myocardial expression and predict the regression potential of LV hypertrophy after AVR. The value of this bedside information for the surgical timing, particularly in asymptomatic aortic stenosis patients, deserves confirmation in further clinical studies.

Myocardial and circulating levels of microRNA-21 reflect left ventricular fibrosis in aortic stenosis patients

BACKGROUND

Various human cardiovascular pathophysiological conditions associate aberrant expression of microRNAs (miRNAs) and circulating miRNAs are emerging as promising biomarkers. In mice, myocardial miR-21 overexpression is related to cardiac fibrosis elicited by pressure overload. This study was designed to determine the role of myocardial and plasmatic miR-21 in the maladaptive remodeling of the extracellular matrix induced by pressure overload in aortic stenosis (AS) patients and the clinical value of miR-21 as a biomarker for pathological myocardial fibrosis.

METHODS

In left ventricular biopsies from 75 AS patients and 32 surgical controls, we quantified the myocardial transcript levels of miR-21, miR-21-targets and ECM- and TGF-β-signaling-related elements. miR-21 plasma levels were determined in 25 healthy volunteers and in AS patients. In situ hybridization of miR-21 was performed in myocardial sections.

RESULTS

The myocardial and plasma levels of miR-21 were significantly higher in the AS patients compared with the controls and correlated directly with the echocardiographic mean transvalvular gradients. miR-21 overexpression was confined to interstitial cells and absent in cardiomyocytes. Using bootstrap validated multiple linear regression, the variance in myocardial collagen expression was predicted by myocardial miR-21 (70% of collagen variance) or plasma miR-21 (52% of collagen variance), together with the miR-21 targets RECK and PDCD4, and effectors of TGF-ß signaling.

CONCLUSIONS

Our results support the role of miR-21 as a regulator of the fibrotic process that occurs in response to pressure overload in AS patients and underscore the value of circulating miR-21 as a biomarker for myocardial fibrosis.

Androgens contribute to sex differences in myocardial remodeling under pressure overload by a mechanism involving TGF-β

BACKGROUND

In clinical studies, myocardial remodeling in aortic valve stenosis appears to be more favorable in women than in men, even after menopause. In the present study, we assessed whether circulating androgens contribute to a less favorable myocardial remodeling under pressure overload in males. We examined sex-related differences in one-year-old male and female mice. Whereas male mice at this age exhibited circulating androgen levels within the normal range for young adults, the circulating estrogens in females were reduced. The contribution of gonadal androgens to cardiac remodeling was analyzed in a group of same-age castrated mice.

METHODOLOGY/PRINCIPAL FINDINGS

Animals were subjected to transverse aortic constriction (TAC). Echocardiography was performed 2 weeks after TAC and myocardial mRNA levels of TGF-βs, Smads 2 and 3, collagens, fibronectin, β-myosin heavy chain and α-myosin heavy chain were determined by q-PCR. Protein detection of p-SMAD2/3 was performed by Western Blot. Histological staining of fibrosis was performed with picrosirius red and Masson's trichrome. Compared with females, males developed more severe tissue fibrosis, LV dilation and hemodynamic dysfunction. TAC-males showed higher myocardial expression levels of TGF-βs and the treatment with a neutralizing antibody to TGF-β prevented myocardial fibrosis development. Orchiectomy diminished TAC-induced up-regulation of TGF-βs and TGF-β target genes, and it also reduced fibrosis and hemodynamic dysfunction. The capability of androgens to induce TGF-β expression was confirmed in NIH-3T3 fibroblasts and H9C2 cardiomyocytes exposed to dihydrotestosterone.

CONCLUSIONS/SIGNIFICANCE

Our results indicate that circulating androgens are responsible for the detrimental effects in the myocardium of older male mice subjected to pressure overload through a mechanism involving TGF-βs.

Myocardial gene expression of microRNA-133a and myosin heavy and light chains, in conjunction with clinical parameters, predict regression of left ventricular hypertrophy after valve replacement in patients with aortic stenosis

BACKGROUND

Left ventricular (LV) reverse remodelling after valve replacement in aortic stenosis (AS) has been classically linked to the hydraulic performance of the replacement device, but myocardial status at the time of surgery has received little attention.

OBJECTIVE

To establish predictors of LV mass (LVM) regression 1 year after valve replacement in a surgical cohort of patients with AS based on preoperative clinical and echocardiographic parameters and the myocardial gene expression profile at surgery.

METHODS

Transcript levels of remodelling-related proteins and regulators were determined in LV intraoperative biopsies from 46 patients with AS by RT-PCR. Using multiple linear regression analysis, an equation was developed (adjusted R²=0.73; p<0.0001) that included positive [preoperative LVM, microRNA-133a, serum response factor (SRF, which is known to be a transactivator of miR-133) and age] and negative [body mass index (BMI), Wolf-Hirschhorn syndrome candidate-2 (WHSC2, which is a target for repression by miR-133a), β-myosin heavy chain, myosin light chain-2, diabetes mellitus, and male gender] independent predictors of LVM reduction.

RESULTS

Aortic valve area gain or the reduction in transvalvular gradient maintained no significant relationships with the dependent variable. Logistic regression analysis identified microRNA-133a as a significant positive predictor of LVM normalisation, whereas β-myosin heavy chain and BMI constituted negative predictors.

CONCLUSIONS

Hypertrophy regression 1 year after pressure overload release is related to the preoperative myocardial expression of remodelling-related genes, in conjunction with the patient's clinical background. In this scenario, miR-133 emerges as a key element of the reverse remodelling process. Postoperative improvement of valve haemodynamics does not predict the degree of hypertrophy regression or LVM normalisation. These results led us to reconsider the current reverse remodelling paradigm and (1) to include criteria of hypertrophy reversibility in the decision algorithm used to decide timing for the operation; and (2) to modify other prevailing factors (overweight, diabetes, etc) known to maintain LV hypertrophy.

Plasma levels of transforming growth factor-beta1 reflect left ventricular remodeling in aortic stenosis

Background

TGF-β1 is involved in cardiac remodeling through an auto/paracrine mechanism. The contribution of TGF-β1 from plasmatic source to pressure overload myocardial remodeling has not been analyzed. We investigated, in patients with valvular aortic stenosis (AS), and in mice subjected to transverse aortic arch constriction (TAC), whether plasma TGF-β1 relates with myocardial remodeling, reflected by LV transcriptional adaptations of genes linked to myocardial hypertrophy and fibrosis, and by heart morphology and function.

Methodology/Principal Findings

The subjects of the study were: 39 patients operated of AS; 27 healthy volunteers; 12 mice subjected to TAC; and 6 mice sham-operated. Myocardial samples were subjected to quantitative PCR. Plasma TGF-β1 was determined by ELISA. Under pressure overload, TGF-β1 plasma levels were significantly increased both in AS patients and TAC mice. In AS patients, plasma TGF-β1 correlated directly with aortic transvalvular gradients and LV mass surrogate variables, both preoperatively and 1 year after surgery. Plasma TGF-β1 correlated positively with the myocardial expression of genes encoding extracellular matrix (collagens I and III, fibronectin) and sarcomeric (myosin light chain-2, β-myosin heavy chain) remodelling targets of TGF-β1, in TAC mice and in AS patients.

Conclusions/Significance

A circulating TGF-β1-mediated mechanism is involved, in both mice and humans, in the excessive deposition of ECM elements and hypertrophic growth of cardiomyocytes under pressure overload. The possible value of plasma TGF-β1 as a marker reflecting preoperative myocardial remodeling status in AS patients deserves further analysis in larger patient cohorts.

Surgical site infections in cardiac surgery after a hospital catastrophe

On 2 November 1999, one of the main hospital façades adjoining cardiovascular surgery collapsed in a 900-bed teaching hospital in Santander, Spain. The purpose of this study was to determine whether the accident affected the safety of patients by increasing the risk for nosocomial and surgical site infections (SSI). Measures for the prevention of nosocomial infections were immediately reinforced. A total of 217 consecutive patients were operated on before 2 November 1999, with another 296 after this date. Patients in both study periods showed similar severity of illness, complexity of surgical procedure and length of hospital stay. The overall rate of nosocomial infection before and after the accident was 28.1% and 24.7%, respectively (P=0.381). The rates of respiratory infection, urinary infection and bacteraemia were also similar. A statistically significant reduction in the SSI rate in the second period was observed (14.8% vs 4.4%, P=0.008). The collapse of the façade was not associated with any increase in nosocomial infection rates, but there was a significant reduction of SSI rates in relation to intensive infection control measures implemented after the collapse.

Left ventricular volume shifts and aortic root expansion during isovolumic contraction

BACKGROUND AND AIM OF THE STUDY

Aortic valve opening involves conformational changes of the aortic root, including the ventricular-aortic junction (VAJ), sinotubular junction (STJ), and cusps. Moreover, the aortic root is contiguous with the left ventricular outflow tract (LVOT), which changes diameter throughout the cardiac cycle. Aortic root expansion prior to valve opening facilitates outward displacement of aortic cusp attachments, which helps flatten the cusps, thereby reducing cusp stress and fatigue, ultimately enhancing functional valve durability. The mechanisms underlying aortic root expansion prior to valve opening, however, remain incompletely characterized. The study aim was to establish a link between such aortic root expansion and intraventricular volume shifts into the LVOT during isovolumic contraction (IVC).

METHODS

Miniature radiopaque markers were implanted on the left ventricle, VAJ, STJ, and aortic cusps of six sheep. After one week, 3-D marker coordinates were obtained using biplane videofluoroscopy (60 Hz). Triangular areas at the VAJ and STJ were calculated; LV main chamber (non-LVOT) and LVOT volumes were calculated using multiple tetrahedra. End-diastole was defined as the peak of the electrocardiogram R-wave, and end-IVC when aortic cusp separation began.

RESULTS

During IVC, blood within the left ventricle was redistributed to the LVOT: mean LVOT volume was increased (+0.2 +/- 0.1 ml, p = 0.009) as non-LVOT volume fell (-0.8 +/- 0.4 ml, p = 0.006). Concomitantly, the aortic root expanded as both VAJ and STJ areas increased (+0.23 +/- 0.12 cm2 (p = 0.005) and +0.25 +/- 0.14 cm2 (p = 0.007), respectively) prior to aortic cusp separation.

CONCLUSION

Aortic root expansion prior to valve opening is closely related to intraventricular volume shifts into the LVOT during IVC. Such volume shifts may 'prime' the aortic valve for ejection. These findings expand our understanding of cardiac dynamics by showing that blood acts as a coupling link between various cardiac units. Preservation of these normal aortic root dynamics may enhance the efficacy and durability of aortic surgical interventions.

Isolated non-compaction of the left ventricular myocardium in an adult treated with heart transplantation

Isolated left ventricular non-compaction is a rare unclassified cardiomyopathy characterized by arrest of normal embryogenesis that results in the persistence of intertrabecular recesses and the development of a spongy myocardium. The pathological diagnosis is often first established at autopsy. Described herein is the case of a 57-year-old man with isolated non-compaction of the left ventricle who had a 17 year history of worsening heart failure and was successfully treated with heart transplantation. To the authors' knowledge only seven adult patients with non-compaction cardiomyopathy have been reported to have undergone heart transplantation. Including the present case the mean age of the adult patients at transplantation was 39.5 years (range, 18-60 years). The male : female ratio was 3:1. Both ventricles were involved in 37.5% of cases. The mean follow up was 6.3 years (range, 2 months-17 years). One patient died because of a malignant tumor 9 years after transplantation. The morphological pattern of the isolated ventricular non-compaction represents a pathological entity discernible from other cardiomyopathies and should be classified as a specific cardiomyopathy. It is likely that surgical pathologists will encounter this entity more frequently due to involvement in transplantation teams.

Ring annuloplasty prevents delayed leaflet coaptation and mitral regurgitation during acute left ventricular ischemia

OBJECTIVE

Incomplete mitral leaflet coaptation during acute left ventricular ischemia is associated with end-diastolic mitral annular dilatation and ischemic mitral regurgitation. Annular rings were implanted in sheep to investigate whether annular reduction alone is sufficient to prevent mitral regurgitation during acute posterolateral left ventricular ischemia.

METHODS

Radiopaque markers were inserted around the mitral anulus, on papillary muscle tips, and on the central meridian of both mitral leaflets in three groups of sheep: control (n = 5), Physio ring (n = 5) (Baxter Cardiovascular Div, Santa Ana, Calif), and Duran ring (n = 6) (Medtronic Heart Valve Div, Minneapolis, Minn). After 8 +/- 1 days, animals were studied with biplane videofluoroscopy before and during left ventricular ischemia. Annular area was calculated from 3-dimensional marker coordinates and coaptation defined as minimal distance between leaflet edge markers.

RESULTS

Before ischemia, leaflet coaptation occurred just after end-diastole in all groups (control 17 +/- 41, Duran 33 +/- 30, Physio 33 +/- 24 ms, mean +/- SD, P >.2 by analysis of variance). During ischemia, regurgitation was detected in all control animals, and leaflet coaptation was delayed to 88 +/- 8 ms after end-diastole (P =.02 vs preischemia). This was associated with increased end-diastolic annular area (8.0 +/- 0.9 vs 6.7 +/- 0.6 cm(2), P =.004) and septal-lateral annular diameter (2.9 +/- 0.1 vs 2.5 +/- 0.1 cm, P =.02). Mitral regurgitation did not develop in Duran or Physio sheep, time to coaptation was unchanged (Duran 25 +/- 25 ms, Physio 30 +/- 48 ms [both P >.2 vs preischemia]), and annular area remained fixed.

CONCLUSION

Mitral annular area reduction and fixation with an annuloplasty ring eliminated delayed leaflet coaptation and prevented mitral regurgitation during acute left ventricular ischemia after ring implantation.

Restricted posterior leaflet motion after mitral ring annuloplasty

BACKGROUND

The effects of ring annuloplasty on mitral leaflet motion are incompletely known. The three-dimensional dynamics of the mitral valve in vivo were examined to determine how two types of annuloplasty rings affect leaflet motion during valve closure.

METHODS

Miniature radiopaque markers on the mitral leaflets, annulus, and left ventricle were implanted in three groups of sheep. One group served as control (n = 7); other sheep were randomly assigned to receive either a flexible Duran (n = 6) or a semirigid Carpentier-Edwards Physio ring (n = 6). After recovery, three-dimensional marker coordinates were computed from simultaneous (60 Hz) biplane videofluoroscopic marker images.

RESULTS

Both types of rings immobilized the middle scallop of the posterior leaflet without affecting anterior leaflet motion. The excursion of the anterior leaflet edge from maximally open to fully closed was not different between the groups (control, 13+/-2 mm; Duran 13+/-1 mm; Physio ring, 14+/-1 mm; p > 0.05), but posterior leaflet edge excursion was restricted (control, 7.4+/-0.4 mm; 2.3+/-0.3 mm [p < 0.001]; Physio, 2.7+/-0.2 mm [p < 0.001]) by both rings.

CONCLUSIONS

Mitral annuloplasty with either ring type markedly reduced the mobility of the central posterior leaflet in normal ovine hearts such that valve closure became essentially a single (anterior) leaflet process with the frozen posterior leaflet serving only as a buttress for closing.

Mitral annular size and shape in sheep with annuloplasty rings

BACKGROUND

Mitral annuloplasty is an important element of most mitral repairs, yet the effects of various types of annuloplasty rings on mitral annular dynamics are still debated. Recent studies suggest that flexible rings preserve physiologic mitral annular area change during the cardiac cycle, while rigid rings do not.

METHODS

To clarify the effects of mitral ring annuloplasty on mitral annular dynamic geometry, we sutured 8 radiopaque markers equidistantly around the mitral anulus in 3 groups of sheep (n = 7 each: no ring, Carpentier-Edwards semi-rigid Physio-Ring [Baxter Healthcare Corp, Edwards Division, Santa Ana, Calif], and Duran flexible ring [Medtronic, Inc, Minneapolis, Minn]). Ring sizes were selected according to anterior leaflet area and inter-trigonal distance (Physio-Ring 28 mm, n = 7; Duran ring 31 mm, n = 5, and 29 mm, n = 2). After 8 +/- 1 days of recovery, the sheep were sedated and studied by means of biplane videofluoroscopy. Mitral annular area was calculated from 3-dimensional marker coordinates without assuming circular or planar geometry.

RESULTS

In the no ring group, mitral annular area varied during the cardiac cycle by 11% +/- 2% (mean +/- SEM; maximum = 7.6 +/- 0.2, minimum = 6.8 +/- 0.2 cm2; P </=.001). Mitral annular area was fixed in the Physio-Ring group (4. 6 +/- 0.1 cm2) and, surprisingly, also static in the Duran ring group (4.8 +/- 0.1 cm2; P =.26 vs Physio-Ring). Furthermore, mitral annular 3-dimensional shape changed in the no-ring group during the cardiac cycle, but not in the Physio-Ring or Duran groups.

CONCLUSIONS

Mitral annular area and shape did not change during the cardiac cycle after ring annuloplasty, regardless of ring type. Thus mitral annular area reduction, independent of intrinsic ring flexibility, is the chief mechanism responsible for the salutary effects of mitral ring annuloplasty.

The CarboMedics valve: experience with 1,049 implants

BACKGROUND

The lack of valve rotatability, the structural deterioration, and the rate of valve-related complications with the standard mechanical bileaflet prosthesis led to the development of a new second-generation bileaflet valve in 1986.

METHODS

Between January 1989 and March 1994, 1,049 CarboMedics valves were implanted in 859 patients. The rotatability was used in 109 mitral prostheses (21.5%) and in 61 aortic prostheses (11.6%). Follow-up was 97.1% complete, with 3,049 patient-years.

RESULTS

The hospital mortality was 6.9% for the mitral group, 3.4% for the aortic group, and 10.7% for the double-valve group (p < 0.005). The actuarial survival curve at 5 years was 77.3% +/- 3.6%, 90.1% +/- 2.5%, and 79.2% +/- 3.7% (p = 0.0003), freedom from thromboembolism was 89.1% +/- 3.6%, 87.1% +/- 3.8%, and 68.8% +/- 8.2%, freedom from reoperation was 95.9% +/- 1.4%, 98.9% +/- 0.6%, and 94.9% +/- 2.4%, and freedom from valve-related complications was 68.8% +/- 4.1%, 79.5% +/- 3.5%, and 55.3% +/- 5.9% after mitral, aortic, and mitral and aortic valve replacement, respectively. There were five episodes of valve thrombosis, but no structural deterioration occurred.

CONCLUSIONS

The clinical performance of the CarboMedics valve is quite satisfactory, with a low incidence of valve-related mortality and morbidity. The rotatability feature was useful when the native valve was preserved or for repeat valve replacement.

Poor clinical performance of the Wessex porcine heart valve bioprosthesis at nine years' follow up

OBJECTIVE

To assess the long term performance of the Wessex porcine bioprostheses implanted in a consecutive series of patients.

DESIGN

A retrospective case series.

PATIENTS

Between January 1985 and July 1991, 184 Wessex bioprostheses (78 mitral, 102 aortic, and 4 tricuspid) were implanted in 150 patients. The patients were 55% (83/150) male and 45% (67/150) female; mean age was 60 (SD 10) years.

RESULTS

Hospital mortality was 9.3% (14/150). Total follow up was 696 patient-years (mean 4.7 years per patient). Linearised rates (events per 100 patient-years (SEM) for postoperative complications for patients with isolated mitral valve replacement, isolated aortic valve replacement, and multiple valve replacement were, respectively: late mortality: 4.7 (1.6), 3.3 (0.9), and 4.9 (1.9); thromboembolism: 5.8 (1.8), 3.0 (0.9), and 2.8 (1.4); valve thrombosis: 1.0 (0.7), 0.3 (0.3), and 0.7 (0.7); structural failure: 5.8 (1.7), 1.9 (0.7), and 7.1 (2.2). Actuarial freedom from complications at nine years (70% confidence interval) was: late mortality: 61 (9)%, 57 (13)%, and 59 (12)%; thromboembolism and valve thrombosis: 71 (9)%, 79 (6)%, and 81 (8)%; structural failure: 33 (14)%, 50 (16)%, and 12 (14)%; all valve related morbidity/mortality: 31 (10)%, 21 (11)%, and 7 (9)%. Stent fractures appeared in 11 of 17 explanted prostheses; actuarial freedom from stent fracture at nine years was 66 (12)%.

CONCLUSIONS

The Wessex bioprosthesis is associated with high thrombogenicity, early structural dysfunction, and a high valve related morbidity/mortality which justifies very close follow up of patients fitted with them.

Stent fracture in Wessex porcine heart valve bioprostheses

By January 1994, a total of 40 Wessex porcine bioprostheses (21 mitral, 18 aortic, and 1 tricuspid) were explanted from 31 subjects. They belonged to a series of 150 patients who received 184 of such prostheses in our unit. Seventeen of these explanted prostheses were available for study, and 11 of them presented some sort of stent fracture or fissuring (mean of 3.6 +/- 1.6 fractures per prosthesis). The disruption occurred in all cases at the base of the commissural arch or at the commissural bar of the stent. The fractures were not detected clinically nor echo-cardiographically before reoperation, and most valves were explanted for reasons other than the stent rupture itself. The actuarial probability of freedom from stent fracture in our series is 66 +/- 12% at 9 years of follow-up. In our experience, fracture of the stent is an important mode of structural dysfunction of the Wessex porcine bioprostheses.

Clinical experience with the CarboMedics valve: early results with a new bileaflet mechanical prosthesis

Between January 1989 and August 1992, 612 CarboMedics mechanical prostheses (CarboMedics, Inc., Austin, Tex.) (295 mitral, 308 aortic, and 9 tricuspid) were implanted in 504 patients: 189 patients had isolated mitral valve replacement, 209 had isolated aortic valve replacement, and 106 had multiple valve replacement. The total follow-up was 1182 patient-years. The hospital mortality rate was 7.4% for mitral valve replacement, 5.3% for aortic valve replacement, and 13.2% for multiple valve replacement. Linearized rates for the different complications for mitral valve replacement, aortic valve replacement, and multiple valve replacement (in events per 100 patient-years) were, respectively, as follows: late mortality, 2.6 +/- 0.8, 1.5 +/- 0.5, and 3.9 +/- 1.3; thromboembolism [correction of thromboembolim], 3.7 +/- 0.9, 3.1 +/- 0.8, and 3.9 +/- 1.3; valve thrombosis, 0.5 +/- 0.3 for mitral valve replacement and 0.4 +/- 0.4 for multiple valve replacement; anticoagulant-related hemorrhage, 2.8 +/- 0.8, 1.9 +/- 0.6, and 2.6 +/- 1.1; nonstructural dysfunction, 1.6 +/- 0.6, 0.8 +/- 0.4, and 3.5 +/- 1.2; and reoperation, 1.1 +/- 0.5, 0.4 +/- 0.3, and 3.1 +/- 1.1. Actuarial estimates of freedom from the different complications for mitral valve replacement, aortic valve replacement, and multiple valve replacement (at 5 years of follow-up for mitral valve replacement and aortic valve replacement and 4.5 years for multiple valve replacement) were, respectively, as follows: overall death, 83% +/- 4%, 89% +/- 2%, and 76% +/- 4%; thromboembolism or valve thrombosis, 88% +/- 3%, 91% +/- 2%, and 86% +/- 5%; anticoagulant-related hemorrhage, 89% +/- 3%, 95% +/- 2%, and 90% +/- 5%; nonstructural dysfunction, 97% +/- 1%, 98% +/- 1%, and 91% +/- 3%; and reoperation, 96% +/- 2%, 99% +/- 1%, and 87% +/- 5%. There were no instances of prosthetic structural dysfunction. The performance of the CarboMedics valve is satisfactory at 5 years of follow-up but thromboembolic and hemorrhagic phenomena are still serious complications of mechanical prostheses.

Isolated apical intracavitary left ventricular abscess in a normal heart: a rare complication of Streptococcus milleri endocarditis

A 31-year-old patient without past history of cardiac disease presented with an atypical form of Streptococcus milleri endocarditis. The disease progressed in an unusually aggressive manner, with abscess formation in the apex of the left ventricular cavity. The cardiac valves functioned normally and were not affected by the disease.

[Cerebrospinal fluid drainage to protect the spinal cord during surgical repair of thoracoabdominal aortic aneurysm]

Spinal cord injury is a serious complication of aortic cross-clamping during thoracoabdominal aortic surgery. We report the case of a 59-year-old man whose mycotic pseudoaneurysm in the thoracoabdominal aorta was repaired surgically. Cerebrospinal fluid pressure was monitored and the fluid was drained to protect the spinal cord while the aorta was clamped. A 19-G epidural catheter was inserted into the subarachnoid space using a paramedian approach form L2-L3. The aorta was clamped at the thoracic level in the descending distal portion and at the abdominal level above the kidney, for a period of 61 minutes. A total of 65 ml of cerebrospinal fluid was drained. The early postoperative period was uneventful and tubes were removed 40 hours after surgery. The results of neurological examination were normal. One week later the patient developed a respiratory infection, which was followed by multi-organ failure and died 22 days after the operation. We discuss the case and review the various alternatives available for protecting the spinal cord during surgery on the thoracoabdominal aorta.

Commissural dehiscence of Carpentier-Edwards mitral bioprostheses. Explant analysis and pathogenesis

Manufacturing factors have seldom been implicated as a direct cause of structural deterioration of valvular bioprostheses; this phenomenon has generally been considered to be of a host-dependent origin. We analyzed the clinical and pathologic data from 12 Carpentier-Edwards mitral bioprostheses removed from 12 patients because of severe dysfunction and showing detachment of the porcine aortic wall from the stent in one commissure or more. These 12 prostheses were part of a group of 92 such valves that were explanted and displayed structural deterioration. They belong to a population of 405 Carpentier-Edwards bioprostheses implanted in the mitral position in our institution between May 1978 and November 1988. The patients included three men and nine women with a mean age of 54 +/- 13 years. One patient had a history of chronic renal failure, and two had systemic hypertension. Prosthesis sizes were 29, 31, and 33 mm (n = 4 for each size). The models of the valves were 6625 (n = 8) and 6650 (n = 4). Mean duration of implantation of the prostheses was 99 +/- 27 months (52 to 136 months) and did not differ depending on the model. There was no significant clustering of commissural detachments depending on valve size, year of implantation, or gender of the patient. No similar phenomenon was observed among 76 explanted aortic Carpentier-Edwards bioprostheses with structural deterioration from a population of 441 valves implanted during the same time frame. Native porcine aortic roots (n = 5) and aortic Carpentier-Edwards bioprostheses explanted because of structural deterioration (n = 4) were used as controls for comparison. Macroscopic examination showed single commissural dehiscence in 10 patients and double in two. Radiology disclosed no or mild mineralization in eight valves and no calcium in the area of aortic wall dehiscence, except for heavily calcified valves. Light microscopy evidenced a significant thinning of the aortic wall at the paracommissural level of mitral bioprostheses (351 +/- 68 microns) compared with either aortic bioprostheses (526 +/- 59 microns; p < 0.01) or control native porcine aortic roots (419 +/- 50 microns; p < 0.01). No difference was found in terms of aortic wall thickness between detached (322 +/- 42 microns) and intact (366 +/- 74 microns) commissures in mitral bioprostheses.(ABSTRACT TRUNCATED AT 400 WORDS)

Durability of the Carpentier-Edwards porcine bioprosthesis: role of age and valve position

The durability (structural deterioration-free interval) after valve implantation with the first-generation Carpentier-Edwards porcine bioprosthesis has been investigated. From 1978 through 1984, 420 patients (175 male, 245 female) underwent valve replacement with the Carpentier-Edwards standard bioprosthesis. Mean age was 50.6 years (range, 13 to 77 years). Isolated mitral valve replacement (MVR) was performed in 198 patients (47.1%), aortic valve replacement (AVR) in 136 (32.4%), and double valve replacement (DVR) in 86 (20.5%). Hospital mortality was 32 patients (7.6%), 7.5% for MVR, 5.1% for AVR, and 11.6% for DVR. Mean follow-up was 10.8 years (range, 9 to 15 years) and is 96.2% completed. Reoperation for structural deterioration was required in 143 patients. Actuarial curve free from structural deterioration at 15 years is 33.0% +/- 6.5% for MVR, 62.0% +/- 5.1% for AVR, and 44.2% +/- 8.2% for DVR (p < 0.03). Durability of the CE bioprosthesis for MVR was 101.6 +/- 34.5 months, 92.9 +/- 26.4 for AVR, and 84.3 +/- 25.3 for DVR (p = not significant). The regression logistic analysis between age at the time of surgery and durability of the bioprosthesis showed no correlation for the MVR group, but with the following predictive formula for AVR and DVR groups of patients older than 30 years" durability = 46.05 + 0.818 x age, for AVR (r2 = 0.43); durability = 15.81 + 1.122 x age, for DVR (r2 = 0.52). In conclusion, we have found a significant difference in the behavior of the CE porcine bioprosthesis between the mitral and aortic position.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-dependent dystrophic calcification of the aortic valve leaflets in normal subjects

The aortic valves of 43 subjects (14 females and 29 males, mean age 48.9 +/- 22.2 years, range 3-88 years), dying from accidental causes and without any previous record of cardiovascular disease, were studied. The whole aortic root was removed and morphological features recorded. Calcium content was determined by atomic absorption spectrophotometry. Calcium content sustained a positive significant correlation (p < 0.001) with age. Comparison of regression lines from subjects of different age groups disclosed a significantly greater slope in the regression line of persons older than 50 years than in those of the younger population (p < 0.05). The increase with age of calcium content displayed no significant differences between male and female nor between any of the three aortic cusps. The presence of Lambl's excrescences on the aortic leaflets became more frequent with age and was associated with a higher calcium content.