Characterization of the early lesion of 'degenerative' valvular aortic stenosis. Histological and immunohistochemical studies

Is it ever too late to operate on the patient with valvular heart disease?

All valvular heart disease imparts a hemodynamic burden on the left and/or right ventricle. This burden can only be removed effectively by correcting the responsible valvular lesion. Although a percutaneous approach is usually used to correct mitral stenosis, other valve lesions require surgical intervention. Over the past 40 years there has been a persistent improvement in our understanding of the pathophysiology of valvular heart disease and in the surgical techniques for correcting it. These factors have acted in concert to alter our view of the proper timing and applicability of surgery. On one hand it is no longer necessary or even advisable to delay surgery until advanced symptoms are present, and thus surgery is timed earlier today than it was even a decade ago. On the other hand, many but not all patients with far advanced disease, once considered inoperable, are now often helped substantially by valve surgery. However, selection of which of these very ill patients will or will not benefit from valve surgery remains a challenge for all of us. It is this group of patients that is addressed in the review.

Neoangiogenesis, T-lymphocyte infiltration, and heat shock protein-60 are biological hallmarks of an immunomediated inflammatory process in end-stage calcified aortic valve stenosis

OBJECTIVES

We investigated the main biomolecular features in the evolution of aortic stenosis, focusing on advanced lesions.

BACKGROUND

"Degenerative" aortic valve stenosis shares risk factors and inflammatory similarities with atherosclerosis.

METHODS

We compared nonrheumatic stenotic aortic valves from 26 patients undergoing surgical valve replacement (group A) and 14 surgical control patients (group B). We performed semiquantitative histological and immunohistochemical analyses on valve leaflets to measure inflammation, sclerosis, calcium, neoangiogenesis, and intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression. We assessed heat shock protein 60 (hsp60) gene expression as an index of cellular stress and C-reactive protein, erythrocyte sedimentation rate, and fibrinogen as systemic inflammatory markers.

RESULTS

In group A valves, we found a prevalence of calcium nodules surrounded by activated inflammatory infiltrates, neovessels, and abundant ICAM-1, VCAM-1, and hsp60 gene expression. Specimens from group B were negative for all of these markers, except 2 of 14 positivity for hsp60. The presence of active inflammatory infiltrates correlated with an abundance of thin neovessels (p < 0.01) and hsp60 gene expression (p = 0.01), whereas neoangiogenesis correlated with inflammation (p = 0.04), calcium (p = 0.01), and hsp60 gene expression (p = 0.04).

CONCLUSIONS

"Degenerative" aortic valve stenosis appears to be a chronic inflammatory process associated with atherosclerotic risk factors. The coexistence of neoangiogenesis, T-lymphocyte infiltration, adhesion molecules, and hsp60 gene expression indicates an active immunomediated process in the final phases of the disease.

Timing of Aortic Valve Surgery in Chronic Aortic Stenosis and Regurgitation

The correct timing of aortic valve replacement in chronic aortic stenosis or regurgitation is a very important and sometimes difficult task for physicians caring for patients with aortic valve disease. In this review, we will present the current available literature regarding the appropriate management of these patients.

Inflammation, infection, and aortic valve sclerosis

Atherosclerosis-related mechanisms, including inflammation and possibly infection, are likely to be involved in the pathogenesis of calcific aortic valve disease. The purpose of this study was to examine whether systemic inflammatory markers and Chlamydia pneumoniae seropositivity are associated with aortic valve sclerosis (AVS) in a sample of the general population. Transesophageal echocardiography was performed in 381 subjects (median age: 67 years, range: 51-101; 52% men), a sample of the adult population in Olmsted County, Minnesota. The associations between systemic inflammatory markers (blood counts, including white blood cells differential counts, fibrinogen, and high-sensitivity C-reactive protein [hs-CRP]), C. pneumoniae immunoglobulin G (IgG) antibody titers, and AVS were examined. AVS was present in 140 subjects (37% of the population). After adjustment for age, sex, and smoking status: (1). hs-CRP was associated with AVS (odds ratio: 1.20 per two-fold increase in hs-CRP; 95% confidence interval: 1.01-1.43; P = 0.04) but this association was not significant after adjustment for additional risk factors for AVS, including body mass index (P = 0.52). (2). Blood counts and fibrinogen were not associated with AVS (P-values >0.30). (3). C. pneumoniae IgG antibody titers (low [1:16-1:32], intermediate [1:64-1:128], or high [>or=1:256] titers, compared with titers <1:16) were not associated with AVS (P = 0.21). In conclusion, hs-CRP is weakly associated with AVS, an association that is not independent of other AVS risk factors. Blood counts, fibrinogen, and C. pneumoniae seropositivity are not associated with AVS. These findings suggest that other non-inflammatory non-infectious mechanisms are likely to have a role in the pathogenesis of calcific aortic valve disease.

Nε-(Carboxymethyl)lysine depositions in human aortic heart valves: similarities with atherosclerotic blood vessels

Recent studies indicate a role of atherosclerosis-like changes involved in the pathogenesis of aortic valve stenosis. Interestingly, one of the major advanced glycation end products (AGEs), N(omega)-(carboxymethyl)lysine (CML) has been related to the process of atherosclerosis in blood vessels. In the present study, we have analyzed the presence of CML in degenerative altered aortic valves with atherosclerosis-like changes, and in degenerated mitral valves without atherosclerosis-like changes, derived from patients suffering from acute rheumatism during childhood. Degenerated and non-degenerated valves were derived from autopsy or obtained during cardiac surgery. The presence of CML was examined by immunohistochemistry. CML was found on the endothelium and fibroblasts in control aortic and mitral valves. Minor differences in CML staining were observed between control and degeneratively affected mitral valves. In contrast, in degenerated aortic valves, CML accumulation was found in macrophages and on calcification sites, comparable to that in atherosclerotic arteries, while the presence of CML staining on the endothelium and fibroblasts was significantly less as compared with control aortic valves. Our data support the hypothesis that the process of degeneration of aortic valves resembles that of atherosclerosis in blood vessels. They suggest that CML also plays a role in the process of atherosclerosis in aortic valves.

Osteogenic regulation of vascular calcification: an early perspective

Cardiovascular calcification is a common consequence of aging, diabetes, hypercholesterolemia, mechanically abnormal valve function, and chronic renal insufficiency. Although vascular calcification may appear to be a uniform response to vascular insult, it is a heterogenous disorder, with overlapping yet distinct mechanisms of initiation and progression. A minimum of four histoanatomic variants-atherosclerotic (fibrotic) calcification, cardiac valve calcification, medial artery calcification, and vascular calciphylaxis-arise in response to metabolic, mechanical, infectious, and inflammatory injuries. Common to the first three variants is a variable degree of vascular infiltration by T cells and macrophages. Once thought benign, the deleterious clinical consequences of calcific vasculopathy are now becoming clear; stroke, amputation, ischemic heart disease, and increased mortality are portended by the anatomy and extent of calcific vasculopathy. Along with dystrophic calcium deposition in dying cells and lipoprotein deposits, active endochondral and intramembranous (nonendochondral) ossification processes contribute to vascular calcium load. Thus vascular calcification is subject to regulation by osteotropic hormones and skeletal morphogens in addition to key inhibitors of passive tissue mineralization. In response to oxidized lipids, inflammation, and mechanical injury, the microvascular smooth muscle cell becomes activated. Orthotopically, proliferating stromal myofibroblasts provide osteoprogenitors for skeletal growth and fracture repair; however, in valves and arteries, vascular myofibroblasts contribute to cardiovascular ossification. Current data suggest that paracrine signals are provided by bone morphogenetic protein-2, Wnts, parathyroid hormone-related polypeptide, osteopontin, osteoprotegerin, and matrix Gla protein, all entrained to endocrine, metabolic, inflammatory, and mechanical cues. In end-stage renal disease, a "perfect storm" of vascular calcification often occurs, with hyperglycemia, hyperphosphatemia, hypercholesterolemia, hypertension, parathyroid hormone resistance, and iatrogenic calcitriol excess contributing to severe calcific vasculopathy. This brief review recounts emerging themes in the pathobiology of vascular calcification and highlights some fundamental deficiencies in our understanding of vascular endocrinology and metabolism that are immediately relevant to human health and health care.

Lipid profile of patients with aortic stenosis might be predictive of rate of progression

BACKGROUND

Aortic stenosis is one of the most commonly encountered valvular pathology requiring surgery in developed countries. There are similarities between risk factors for coronary atherosclerosis and the development of aortic stenosis. We designed a retrospective study, evaluated the lipid profile and previous echocardiographic recordings of patients with aortic stenosis, and searched the association of rate of progression and lipid profile.

METHODS AND RESULTS

The annual rates of progression in the peak and mean aortic gradients were 8.5 +/- 3.2 and 6.7 +/- 2.2 mm Hg/year, respectively. We classified the annual rate of progression of peak aortic gradient into 2 groups, group 1 with <10 mm Hg ("slow progressors") and group 2 with > or =10 mm Hg annual rate of progression ("fast progressors"). The annual rate of progression in group 1 was significantly higher than that in group 2, both in peak and mean aortic gradients (12 +/- 2 mm Hg and 6.4 +/- 1.6 mm Hg; 9 +/- 1.3 mm Hg and 5.2 +/- 1.1 mmHg; P <.001 for both). There was a highly significant difference between group 1 and group 2 for total cholesterol/high-density lipoprotein (HDL) cholesterol level ratio (7.1 +/- 1.4 vs 5.2 +/- 1.3, P <.001). There was a significant correlation between annual rate of progression in peak gradient and total cholesterol/HDL cholesterol level ratio (r = 0.399, P =.009). Smoking (P =.024, Beta = 0.26), presence of coronary heart disease (P =.011, Beta = 0.31), and total cholesterol/HDL cholesterol level ratio (P =.004, Beta = 1.98) were independently predictive of fast progression of the peak aortic gradient in the regression analysis.

CONCLUSION

In a small group of patients from Turkey with aortic stenosis, there seems to be an association between the rate of progression and total cholesterol/HDL cholesterol level ratio, with fast progression occurring in the group with higher ratios.

Association of aortic valve sclerosis and coronary artery disease in patients with severe nonischemic mitral regurgitation

BACKGROUND

The presence of aortic valve sclerosis accounts for a higher rate of ischemic events and increased cardiovascular mortality. It may reflect coronary artery disease (CAD) because of a shared pathologic background.

HYPOTHESIS

We aimed to analyze whether the presence of aortic valve sclerosis might help in identifying patients with coronary atherosclerosis among those with severe nonischemic mitral regurgitation (MR), who undergo coronary angiography before surgery for screening, and not because of suspected ischemic heart disease.

METHODS

In all, 84 patients (mean age 64 +/- 9 years; 71% men) with mitral valve prolapse and severe regurgitation underwent echocardiography and coronary angiography. Aortic valve sclerosis was defined as focal areas of increased echogenicity and thickening of the leaflets without restriction of leaflet motion on echocardiography. Coronary artery disease was defined by the presence/absence of atherosclerotic plaques, independent of the degree of stenosis.

RESULTS

Coronary artery disease was diagnosed in 47.6% of patients with and 15.8% of those without aortic valve sclerosis (p = 0.008). On logistic regression analysis, the presence of aortic valve sclerosis predicted CAD (odds ratio 3.3, 95% confidence interval 1.03-10.5; p = 0.04) independent of age. In female patients, the risk ratio for CAD in the presence of aortic valve sclerosis was 9.

CONCLUSIONS

Coronary artery atherosclerosis and aortic valve sclerosis are closely associated in patients with severe nonischemic MR.

Hemodynamic Effects of the Angiotensin-Converting Enzyme Inhibitor, Ramipril, in Patients with Mild to Moderate Aortic Stenosis and Preserved Left Ventricular Function

Background

Angiotensin-converting enzyme (ACE) inhibitor use is presumed to be contraindicated in patients with aortic stenosis (AS). We determined the hemodynamic effects of ACE inhibitors in patients with mild to moderate aortic stenosis (AS) and preserved left ventricular function.

Methods

Thirteen elderly patients (mean [SD] age = 65 [17] years), with mild to moderate AS (aortic jet velocity 2.5–4.0 m/s), normal left ventricular and renal function, and no clinical coronary artery disease, were enrolled in a single-center, open-label trial comparing the hemodynamic effects at baseline and following titration of ramipril to a maximum dose of 7.5 mg twice daily. Patients were identified from echocardiography laboratory logs. Despite a presumed contraindication to ACE inhibitor use in AS patients, 30% (71 of 235) of patients otherwise meeting inclusion or exclusion criteria were excluded owing to current ACE inhibitor use. Patients were monitored with weekly clinic visits, biweekly laboratory tests, and monthly echocardiograms.

Results

There were no significant changes from baseline to week 8 in echocardiographic parameters, including mean (SD) aortic jet velocity [2.9 (0.4) vs 2.9 (0.4) m/s], calculated aortic transvalvular gradient [18 (6) vs 18 (6) mm Hg], or cardiac output [5.5 (1.2) vs 6.0 (2.1) L/min], or significant changes in blood pressure or heart rate. Early discontinuations were for asymptomatic low blood pressure (one patient) or a reversible creatinine increase of 0.3 mg/dL (one patient).

Conclusions

Short-term treatment with up to 7.5 mg twice daily of ramipril was well tolerated in patients with mild to moderate AS and preserved left ventricular function. A surprisingly high proportion of patients with documented AS were already receiving ACE inhibitors.

Aortic valve disease: Current recommendations

Aortic stenosis is a common valvular abnormality. Surgical valve replacement is the standard of care for symptomatic patients with severe aortic stenosis and is appropriate for certain asymptomatic patients. Statin therapy may slow progression of the disease. Contrary to conventional wisdom, vasodilator therapy may in fact be safe and effective in certain instances of severe aortic stenosis. Chronic aortic regurgitation is commonly treated with vasodilator therapy, which is certainly indicated for the asymptomatic patient with hypertension. Surgery is recommended for left ventricular dilatation, diminished ventricular systolic function, or symptoms.

Association of aortic valve calcium detected by electron beam computed tomography with echocardiographic aortic valve disease and with calcium deposits in the coronary arteries and thoracic aorta

We conducted electron beam computed tomographic (EBCT) testing in a representative sample of 327 Framingham Heart Study subjects without clinical cardiovascular disease. EBCT was compared with 2-dimensional echocardiography for the detection of degenerative aortic valve (AV) disease. We determined the association between EBCT measures of AV calcium and calcium deposits in the coronary arteries and thoracic aorta. Of 327 subjects (mean age 60 +/- 9 years; 51% men), 14% had EBCT AV calcium (median Agatston score 0, range 0 to 1,592). The prevalence of AV calcium increased predictably across decades of age. Compared with echocardiography, the sensitivity and specificity of EBCT for the detection of degenerative AV disease were 24% and 94%, respectively. In unadjusted logistic regression models, the prevalence of EBCT AV calcium increased across tertiles of coronary artery calcium (for trend across tertiles, odds ratio [OR] 2.2, 95% confidence interval [CI] 1.4 to 3.5) and thoracic aorta calcium (for trend OR 2.8, 95% CI 1.7 to 4.4). After adjustment for age and gender, the associations of AV calcium with coronary calcium and thoracic aorta calcium were attenuated and no longer statistically significant. Thus, compared with echocardiography, EBCT was specific but insensitive for the detection of degenerative AV disease. EBCT AV calcium was associated with calcium deposits in the coronary arteries and the thoracic aorta, but these associations were confounded by age and risk factors.

Association between cardiac valvular calcification and coronary artery disease in a low-risk population

BACKGROUND

Mitral annulus calcification (MAC) or aortic valve sclerocalcification (AVSC) is common with aging and associated with coronary artery disease (CAD) in Caucasians. This study was performed to determine whether MAC or AVSC is also associated with, and has a power to predict, CAD in Koreans as in Caucasians.

METHODS

Three hundred and eight patients with chest pain, who had undergone coronary angiography and transthoracic echocardiography, were enrolled (189 males; mean 60.5 +/- 9.8 years).

RESULTS

The prevalence of MAC and AVSC was significantly more common in CAD (+) compared with CAD (-) group (83.9%:55.2%, 87.9%:57.5%, respectively, both p < 0.001). On multivariate analysis with MAC and AVSC along with conventional coronary risk factors (cRF), MAC, male gender, AVSC, and diabetes mellitus were significantly associated with CAD (p < 0.001, < 0.001, 0.010 and 0.014 respectively). Additionally, a positive linear relationship was found between the prevalence of both MAC and AVSC and the extent of CAD defined by the number of stenotic coronary arteries (both p < 0.001). Furthermore, the odds ratio for CAD in the group with both multiple valvular sclerocalcification (MVSC) and > or = 2 cRF was 12.3 compared to the < or = 1 cRF group without MVSC.

CONCLUSIONS

MAC and AVSC were independently associated with CAD in a low-risk Korean population. Also, combination of MVSC with > or = 2 cRF increased the predictability of the presence of CAD. Therefore, the possibilities of CAD must be considered when MVSC is detected in transthoracic echocardiography in patients with > or = 2 cRF.

Association of dyslipidemia and effects of statins on nonmacrovascular diseases

BACKGROUND

Statins have mechanisms of action that expand their effects beyond cholesterol lowering and atherosclerotic medical conditions.

OBJECTIVE

This review summarizes clinical evidence for the association of dyslipidemia and the effects of statin use on aortic stenosis, Alzheimer's dementia (AD), osteoporosis, prevention of diabetes mellitus (DM), diabetic retinopathy, age-related macular degeneration, and diabetic/nondiabetic nephropathy.

METHODS

An English-language literature search was conducted using MEDLINE (1966-June 2003). Bibliographies of retrieved articles were reviewed. Search terms included statin, HMG-CoA reductase inhibitors, aortic stenosis, Alzheimer's dementia, osteoporosis, prevention of diabetis, diabetic retinopathy, age-related macular degeneration, diabetic nephropathy, and nondiabetic nephropathy.

RESULTS

Three retrospective cohort trials have shown an association between statin use and the progression of aortic stenosis; one of these trials observed a 45% decrease in aortic valve area in 1 year. In AD, one cross-sectional analysis found 60% to 73% lower AD rates in lovastatin or pravastatin recipients ( P<0.001 ). Of the multiple observational studies on the effect of statins on fracture risk, some have shown a decreased risk, with an odds ratio as low as 0.50 (95% CI, 0.33-0.76); others have demonstrated no association. A post hoc analysis of the West of Scotland Coronary Prevention Study found a 30% reduction in the development of DM ( P=0.042 ), but this was not duplicated in the Anglo-Scandinavian Cardiac Outcomes Trial-Lipid Lowering Arm. A small clinical trial of 6 patients (11 eyes) demonstrated improved retinal hard exudates with pravastatin treatment in patients with diabetic retinopathy. In a cross-sectional analysis, age-related macular degeneration was found to be less common among statin users than nonusers (4% [ 1/27 ] vs 22% [ 76/352 ]; P=0.02. Multiple small clinical trials of 19 to 56 patients with diabetic and nondiabetic nephropathy at various stages generated inconsistent results for an association between statin use and decreased albumin excretion rate and decreased rate of decline in glomerular filtration.

CONCLUSION

Data of variable quantity and quality support the use of statins as adjuncts in the treatment of nonmacrovascular diseases.

Adverse outcome in aortic sclerosis is associated with coronary artery disease and inflammation

OBJECTIVES

The present study was designed to evaluate the relationship between the presence of aortic sclerosis, serologic markers of inflammation, and adverse cardiovascular outcomes.

BACKGROUND

Aortic sclerosis is associated with adverse cardiovascular outcomes. However, the mechanism by which such nonobstructive valve lesions impart excess cardiovascular risk has not been delineated.

METHOD

In 425 patients (mean age 68 +/- 15 years, 54% men) presenting to the emergency room with chest pain, we studied the relationship among aortic sclerosis, the presence and acuity of coronary artery disease, serologic markers of inflammation, and cardiovascular outcomes. Patients underwent echocardiography and serologic testing including C-reactive protein (CRP). Aortic valves were graded for the degree of sclerosis, and cardiovascular outcomes including cardiac death and nonfatal myocardial infarction (MI) were analyzed over one year.

RESULTS

Aortic sclerosis was identified in 203 patients (49%), whereas 212 (51%) had normal aortic valves. On univariate analysis at one year, patients with aortic sclerosis had a higher incidence of cardiovascular events (16.8% vs. 7.1%, p = 0.002) and worse event-free survival (normal valves = 93%, mild aortic sclerosis = 85%, and moderate to severe aortic sclerosis = 77%, p = 0.002). However, by multivariable analysis aortic sclerosis was not independently associated with adverse cardiovascular outcomes; the only independent predictors of cardiac death or MI at one year were coronary artery disease (hazard ratio [HR] 3.23, p = 0.003), MI at index admission (HR 2.77, p = 0.008), ascending tertiles of CRP (HR 2.2, p = 0.001), congestive heart failure (HR 2.15, p = 0.02) and age (HR 1.03, p = 0.04).

CONCLUSIONS

The increased incidence of adverse cardiovascular events in patients with aortic sclerosis is associated with coronary artery disease and inflammation, not a result of the effects of valvular heart disease per se.

Three-dimensional visualization and thickness estimation of aortic valve cusps using high-frequency ultrasound

High-frequency ultrasound techniques are introduced for three-dimensional imaging and thickness estimation of fresh heart valve cusps. Images of porcine aortic valve specimens were acquired within a 12 x 8 x 8 mm3 volume using a VisualSonics VS40 micro-imaging system operating at a 40 MHz centre frequency. Two image volumes were obtained from each of six left coronary cusps. One volume was acquired with the specimen submerged in distilled water and the second volume was acquired through either Hanks physiologic solution or coronary perfusion solution (CPS). The fibrosa, spongiosa and ventricularis were most readily distinguished when the specimen was imaged in distilled water. Colour thickness maps were computed from B-mode image data, and the mean and standard deviations of the thickness were determined for each cusp. In 11 of 12 trials, the image analysis algorithm yielded valid thickness estimates over greater than 98% of the region examined. Mean thickness estimates obtained with specimens submerged in Hanks solution or CPS ranged from 0.66 to 1.03 mm, and submersion in distilled water increased the mean thickness by 20-40%. This observation suggests that the cusps osmotically absorbed water. Information provided by high-frequency ultrasound is expected be valuable for characterizing the morphological properties of heart valves.

Effect of aortic valve replacement on c-reactive protein in nonrheumatic aortic stenosis

Plasma levels of C-reactive protein were higher in 20 patients with bicuspid or trileaflet degenerative aortic stenosis than in 31 normal controls and in 19 patients with pure aortic regurgitation. C-reactive protein decreased from before to 6 months after aortic valve replacement for aortic stenosis. These observations suggest that aortic stenosis is an inflammatory disease.

Smoothelin-positive cells in human and porcine semilunar valves

Our aim was to further characterize the interstitial cell phenotypes of normal porcine and human semilunar valves, information necessary for the design of bioengineered valves and for the understanding of valve disease processes such as aortic valve sclerosis. Existence of fibroblasts, myofibroblasts, and smooth muscle-like cells within semilunar heart valves has been established. However, the nature of the smooth muscle cell population has been controversial. We used immunochemical and western blotting methods to determine the status of smoothelin and smooth muscle alpha-actin in the valve. Our examination of valve interstitial cells confirmed the presence of terminally differentiated, contractile smooth muscle cells in situ. They were arranged in small bundles of 5-35 cells within the ventricularis or as individual cells scattered throughout the valvular layers in vivo, and were present in cells explanted from the valves in vitro. Colocalization of these proteins in semilunar heart valves was achieved with double-labeling experiments. Protein extraction, followed by coimmunoprecipitation, electrophoresis, and western blotting confirmed the immunochemical analysis and suggested that smooth muscle alpha-actin and smoothelin interact, as has been previously postulated. The presence of contractile smooth muscle within the valve may be an important factor in understanding valve pathology and in the design of tissue engineering efforts.

Interleukin-1 beta promotes matrix metalloproteinase expression and cell proliferation in calcific aortic valve stenosis

Calcific aortic valve stenosis (AS), the main heart valve disease in the elderly, is characterized by extensive remodeling of the extracellular matrix. Matrix metalloproteinases (MMPs) are upregulated in calcific AS and might modulate matrix remodeling. The regulatory mechanisms are unclear. As recent studies have suggested that calcific AS might result from an inflammatory process involving leukocyte invasion and activation, the present study aimed to elucidate the role of the pro-inflammatory cytokine interleukin (IL)-1 beta on MMP expression and cell proliferation in human aortic valves. Immunohistochemistry for leukocytes, IL-1 beta and MMP-1 was performed on aortic valves with (n=6) and without (n=6) calcification obtained at valve replacement or autopsy. Stenotic valves showed marked leukocyte infiltration and associated expression of IL-1 beta and MMP-1. In control valves only scattered leukocytes, low staining for MMP-1 and no staining for IL-1 beta were present. Double-label immunostaining localized IL-1 beta expression mainly to leukocytes and MMP-1 expression to myofibroblasts. Stimulation of cultured human aortic valve myofibroblasts with IL-1 beta lead to a time-dependently increased expression of MMP-1 and MMP-2 by Western blotting and zymography, whereas MMP-9 remained unchanged. Cell proliferation was increased by IL-1 beta as determined by bromodesoxyuridine incorporation. Thus, IL-1 beta may regulate remodeling of the extracellular matrix in calcific AS.

Aortic valve calcification on computed tomography predicts the severity of aortic stenosis

AIM

Incidental aortic valve calcification is often detected during computed tomography. The aim was to compare the severity of valvular stenosis and calcification in patients with aortic stenosis.

MATERIALS AND METHODS

One hundred and fifty-seven patients aged 68+/-11 years (range: 34-85) with aortic valve stenosis underwent multislice helical computed tomography and Doppler echocardiography performed by independent, blinded observers. The aortic valve calcium score was determined using automated computer software calibrated with a phantom.

RESULTS

Doppler echocardiography demonstrated a post-valve velocity of 3.45+/-0.66 m/s and a peak gradient of 49+/-11 mmHg. Computed tomography showed excellent reproducibility and the median aortic valve calcium score was 5858 AU (interquartile range, 1555-14,596). The computed tomography aortic valve calcium score positively correlated with the Doppler post-valve velocity and peak gradient (r=0.54, p<0.0001 for both) of the aortic valve. All patients with severe aortic stenosis had a calcium score of >3700 AU.

CONCLUSION

Calcification of the aortic valve is closely associated with the severity of aortic stenosis, and heavy calcification suggests the presence of severe aortic stenosis that requires urgent cardiological assessment. Patients with lesser degrees of aortic valve calcification should be screened for aortic stenosis and monitored for disease progression.

Is aortic stenosis a preventable disease?

Aortic stenosis (AS) is the most common valvular disease requiring valve replacement. Its prevalence increases with age. When the severity of AS is only mild to moderate, it is well tolerated. When it becomes severe, AS confers significant morbidity and mortality. Adverse events can be avoided if it is possible to prevent or retard the progression from mild or moderate AS to severe AS. Progression of AS parallels the progression of sclerotic changes involving the aortic valve, which share histological and immunochemical similarities with the process of atherosclerosis. Far from being just a degenerative process, the development of AS is a complex and highly regulated process with a number of modifiable factors. One of the key factors appears to be lipoproteins, which are intimately involved in several pathways crucial to the development of AS. The importance of lipoproteins is further supported by epidemiological and clinical studies showing a strong association between lipoproteins and AS. The time has come to initiate prospective studies to assess the effect of cholesterol lowering on the progression of AS.

Oestrogen receptor alpha gene polymorphism is related to aortic valve sclerosis in postmenopausal women

OBJECTIVES

Aortic valvular sclerosis (AS) is an inflammatory process and not a result of normal ageing. The sclerotic process is accelerated by risk factors such as smoking and high cholesterol levels. The genetic factors for the development of AS are however unknown. Therefore the purpose of the present study was to investigate whether polymorphisms in the oestrogen receptor alpha (ORalpha) gene and in the transforming growth factor beta (TGF-beta1) gene were related to the presence of AS in postmenopausal women.

DESIGN

Case-control study.

SUBJECTS AND METHODS

Relationships were tested between polymorphisms in the ORalpha gene defined by the restriction enzymes PvuII and XbaI, and in the TGF-beta1 gene defined by AocI, and AS, lipid levels, and lipoprotein(a) [Lp(a)] in 41 postmenopausal female patients and 41 age- and sex-matched controls. These polymorphisms were also tested in relation to lipid levels and Lp(a), in 99 healthy Caucasian girls, aged 16.9 +/- 1.2 years.

RESULTS

In the postmenopausal patients and age-matched controls, the PvuII polymorphism was independently associated with an increased risk of AS [odds ratio (OR) = 3.38; 95% confidence interval (CI) 1.13-10.09). A genotype defined by at least one restriction site in the PvuII polymorphism and two restriction sites in the TGF-beta1 polymorphism was related to a highly significantly increased risk of AS (OR = 4.58; 95% CI 1.68-12.51). In the adolescent female cohort, presence of two restriction sites in the PvuII polymorphism was associated with higher levels of total cholesterol (TC) (P = 0.02), and low-density lipoprotein cholesterol (LDL) (P = 0.04).

CONCLUSIONS

We have demonstrated that the PvuII polymorphism in the ORalpha gene is related to both the presence of AS in postmenopausal women and to lipid levels in adolescent females, suggesting that this polymorphism may influence the risk of AS partly by affecting lipid levels.

Hypercholesterolemic valvulopathy: an aspect of malignant atherosclerosis

Hypercholesterolemia affects not only the coronary artery, but also the aortic root, particularly the aortic valve. Aortic stenosis is critical in the prognosis for most patients with homozygous familial hypercholesterolemia (FH) and some heterozygous FH patients who result in aortic valve replacement (AVR). Histopathological examination of their valves shows lipid deposition, inflammatory cell infiltration and calcification in the aortic cusps. These pathological findings are common in non-FH patients with AVR. In homozygous FH patients, the aortic valves are injured by extreme hypercholesterolemia in a relatively short period of time, whereas in heterozygous FH patients with additional risk factors, the damage to the valves occurs over an intermediate time period. In the non-FH population with several risk factors, an underlying raised serum cholesterol level results in gradual impairment over a number of years. Aortic valvular dysfunction caused by hypercholesterolemia, which we termed hypercholesterolemic valvulopathy is recognized to be a life-threatening complication as the primary clinical characteristic of malignant atherosclerosis.

Valvular and thoracic aortic calcium as a marker of the extent and severity of angiographic coronary artery disease

BACKGROUND

The presence of calcified extracoronary structures as a useful indicator of underlying coronary artery disease (CAD) has not yet been established. The purpose of this study was to evaluate whether valvular and thoracic aortic calcification is associated with obstructive CAD.

METHODS

We evaluated 99 patients who underwent both coronary angiography and electron beam tomography (EBT) coronary scanning. We identified the presence, absence, and amount of calcification in the aortic valve (AVC), mitral annulus (MAC), descending aorta (DAC), and ascending aorta (AAC). The extent of CAD was graded according to the number of vessels diseased (VD).

RESULTS

Patients with multivessel disease (MVD) had a higher proportion of DAC. The presence of DAC significantly increased the specificity of EBT to detect CAD (58% with a calcium score >0 to 88% for calcium score>0 and DAC >0, P <.001). Both AAC and DAC were associated with a significantly higher rate of MVD in women (DAC, 63% in MVD vs 19% without, P <.01.; AAC, 65% vs 22%, P <.05). MAC had no relationship to either stenosis severity or the presence of obstructive CAD. AVC was the strongest predictor of the severity of CAD and predicted the presence of 3-vessel disease.

CONCLUSION

AVC and thoracic aortic calcification as detected with EBT are associated with the angiographic extent and severity of CAD and add incremental diagnostic value to the coronary artery calcium score. MAC does not add incremental value.

Valvular and perivalvular abnormalities in end-stage renal disease

Valvular and perivalvular involvement in end-stage renal disease (ESRD) is most commonly manifested as mitral annular calcification and aortic valve calcification. Both mitral and aortic valve calcification (MAC) occur more frequently and at younger age in those with ESRD than in those with normal renal function. Aortic valve calcification progresses to aortic stenosis more commonly and at a more accelerated rate than in the general population. Altered calcium and phosphate metabolism are thought to predispose to these valvular and perivalvular abnormalities. No treatment is necessary for MAC unless severe mitral regurgitation or stenosis occur (both are rare). Mitral valve repair or replacement and aortic valve replacement are indicated for severe symptomatic valve stenosis or regurgitation, albeit at a higher risk than in those with normal renal function. Infective endocarditis may complicate MAC or aortic stenosis in patients with ESRD and is associated with a high mortality rate in such patients.

Progression of aortic valve stenosis: TGF-beta1 is present in calcified aortic valve cusps and promotes aortic valve interstitial cell calcification via apoptosis

BACKGROUND

Aortic valve stenosis characteristically progresses due to cuspal calcification, often necessitating valve replacement surgery. The present study investigated the hypothesis that TGF-beta1, a cytokine that causes calcification of vascular smooth muscle cells in culture, initiates apoptosis of valvular interstitial cells as a mechanistic event in cuspal calcification.

METHODS

Noncalcified and calcified human aortic valve cusps were obtained at autopsy or at the time of cardiac surgery. The distributions within cusps of TGF-beta1, latent-TGF-beta1-associated peptide, and TGF-beta receptors were studied using immunohistochemistry. The effects of TGF-beta1 on mechanistic events contributing to aortic valve calcification were also investigated using sheep aortic valve interstitial cell (SAVIC) cultures.

RESULTS

Immunohistochemistry studies revealed that calcific aortic stenosis cusps characteristically contained within the extracellular matrix qualitatively higher levels of TGF-beta1 than noncalcified cusps. Noncalcified normal valves demonstrated only focal intracellular TGF-beta1. Addition of TGF-beta1 to SAVIC cultures led to a cascade of events, including: cellular migration, aggregation, formation of apoptotic-alkaline phosphatase enriched nodules, and calcification of these nodules. The time course of these events in the SAVIC culture system was rapid with nodule formation with apoptosis by 72 hours, and calcification after 7 days. Furthermore, ZVAD-FMK, an antiapoptosis agent (caspase inhibitor), significantly inhibited calcification and apoptosis induced by TGF-beta1, but had no effect on nodule formation. However, cytochalasin D, an actin-depolymerizing agent, inhibited nodule formation, but not calcification.

CONCLUSIONS

TGF-beta1 is characteristically present within calcific aortic stenosis cusps, and mediates the calcification of aortic valve interstitial cells in culture through mechanisms involving apoptosis.

Endothelium and valvular diseases of the heart

It has become increasingly evident that the endothelium plays a critical role in the pathogenesis of valvular heart disease. The endothelium helps regulate vascular tone, inflammation, thrombosis, and vascular remodeling. Dysfunction of the endothelial cells has been linked to many vascular disorders including atherosclerosis. Common valvular diseases such as senile degenerative valve disease, myxomatous (or floppy) valves, rheumatic valves, and infective endocarditis valves show changes in the synthetic, morphologic, and metabolic functions of the valvular endothelial cells. These diseases are active processes related to endothelial cell dysfunction. Endothelial cell dysfunction is caused by mechanical forces, bacterial infection, autoantibodies, and circulating modulators of endothelial cell function. This study reviews the role of endothelial cell dysfunction in the more common valvular diseases. Continued research on endothelial cell dysfunction is crucial to our understanding of valvular heart diseases and may elucidate novel treatment and prevention strategies.

Association of cholesterol levels, hydroxymethylglutaryl coenzyme-A reductase inhibitor treatment, and progression of aortic stenosis in the community

OBJECTIVES

This study was designed to analyze the association among cholesterol levels, lipid-lowering treatment, and progression of aortic stenosis (AS) in the community.

BACKGROUND

Aortic stenosis is a progressive disease for which there is no known medical treatment to prevent or slow progression. Despite plausible pathologic mechanisms linking hypercholesterolemia to AS progression, clinical studies have been inconsistent and affected by referral bias, and the role of lipid-lowering therapy is uncertain.

METHODS

We determined the association between blood cholesterol levels and progression of native AS (assessed by Doppler echocardiography at baseline and at least six months later; mean interval, 3.7 +/- 2.3 years) in a community-based study of 156 patients (age 77 +/- 12 years; 90 men). Thirty-eight patients received statin treatment during follow-up.

RESULTS

In untreated subjects, mean gradient increased from 22 +/- 12 mm Hg to 39 +/- 19 mm Hg, and aortic valve area (AVA) decreased from 1.20 +/- 0.35 cm(2) to 0.91 +/- 0.33 cm(2) (both p < 0.001). The annualized change in AVA was -0.09 +/- 0.17 cm(2)/year (-7% +/- 13%/year). Neither total cholesterol (r = -0.01, p = 0.92) nor low-density lipoprotein cholesterol (r = 0.01; p = 0.88) showed a significant correlation to AS progression. Nevertheless, progression of AS was slower in patients receiving statins compared with untreated patients (decrease in AVA -3 +/- 10% vs. -7 +/- 13% per year, respectively; p = 0.04), even when adjusted for age, gender, cholesterol, and baseline valve area (p = 0.04). The association of statin treatment with slower progression was confirmed when analysis was restricted to patients coming for a systematic follow-up (p=0.02). The odds ratio of AS progression with statin treatment was 0.46 (95% confidence interval, 0.21 to 0.96).

CONCLUSIONS

In the community, progression of AS shows no trend of association with cholesterol levels. Statin treatment, however, is associated with slower progression, suggesting that the effects of statin treatment on progression of AS should be pursued with appropriate clinical trials.

T lymphocyte infiltration in non-rheumatic aortic stenosis: a comparative descriptive study between tricuspid and bicuspid aortic valves

BACKGROUND

The two most common causes of aortic stenosis are primary "degenerative" calcification of tricuspid aortic valves and secondary calcification of congenital bicuspid valves. T lymphocyte infiltration occurs in stenotic tricuspid aortic valves, indicating an inflammatory component, but it has not been shown whether it also occurs in stenotic bicuspid valves.

OBJECTIVE

To compare non-rheumatic tricuspid and bicuspid stenotic aortic valves for the presence and distribution of T lymphocytes.

SETTING

University hospital.

PATIENTS AND DESIGN

Valve specimens were obtained from 29 patients (15 women, 14 men, mean age 69 years (range 52-81 years)), referred to the hospital for aortic valve replacement because of symptomatic aortic valve stenosis. There were 17 tricuspid valves (from 10 women and seven men, mean age 71 years) and 12 bicuspid valves (from five women and seven men, mean age 67 years). To identify mononuclear inflammatory cells, sections were stained with antibodies for CD3 (pan-T cell antigen, Dako 1:400) and then graded histologically according to the degree of T cell infiltrate.

RESULTS

T lymphocyte infiltration was present in both tricuspid and bicuspid stenotic aortic valves, without any significant differences in extent or localisation.

CONCLUSIONS

Stenotic bicuspid aortic valves show the same degree of T lymphocyte infiltration as degenerative tricuspid aortic valves. Inflammation needs to be considered in the pathogenesis of acquired aortic stenosis, irrespective of the primary valve anomaly.

Reproducibility of electron-beam CT measures of aortic valve calcification

RATIONALE AND OBJECTIVES

The authors performed this study to establish the interscan, interobserver, and intraobserver reproducibility of aortic valve calcification (AVC) measurements obtained with electron-beam computed tomography (CT).

MATERIALS AND METHODS

The authors evaluated electron-beam CT scans from all patients who had undergone two serial examinations on the same day as part of a study of coronary artery calcification reproducibility. In patients in whom aortic valve calcium was identified at electron-beam CT, AVC scores were measured with both the Agatston and the volumetric methods, which were developed previously to quantify coronary calcium.

RESULTS

Forty-four asymptomatic patients (mean age, 66 years +/- 9) with AVC at electron-beam CT were included in the analyses. AVC score reproducibility was excellent with both the Agatston and the volumetric methods (R2 = 0.99, P = .0001 for both), with median interscan variabilities of 7% and 6.2%, respectively. Interscan reproducibility was similar, whether the analysis included all scans or was restricted to those with scores greater than 10 or greater than 30. For the volumetric method, the median interobserver variability was 5% and the median intraobserver variability was 1%.

CONCLUSION

The low interscan, interobserver, and intraobserver variabilities at electron-beam CT suggest that this method should be useful for the noninvasive monitoring of AVC changes over time and for assessing the efficacy of therapies aimed at slowing AVC accumulation.

Failure to detect Chlamydia pneumoniae in senile calcific aortic stenosis or calcified congenital bicuspid aortic valve by immunofluorescence, polymerase chain reaction and electron microscopy

INTRODUCTION

Chlamydia pneumoniae has been identified in arterial atherosclerosis. Aortic valves affected by senile calcific aortic stenosis (SCAS) or calcification of a congenital bicuspid valve (CCBAV) may have interior environments similar to atherosclerosis. This study aimed to detect C. pneumoniae within either SCAS or CCBAV.

METHODS

60 valves showing either SCAS (n=36) or CCABV (n=22) and control valves (n=2) were studied for the presence of C. pneumoniae by the following three techniques: (1) indirect immunofluorescence (IF) was performed on 36 SCAS valves, 22 CCBAV valves and 2 control aortic valves using a HEp-2 cell line infected with C. pneumoniae as a positive control. Negative controls comprised duplicate slides of the same valves with omission of the primary antibody step. A section of human stomach was also used as a negative control. A semiquantitative scoring method was used to grade positive IF staining. (2) Polymerase chain reaction (PCR) was performed on 30 SCAS valves, 20 CCBAV valves and 1 control valve using C. pneumoniae as a positive control and negative controls comprised a Ureaplasma sp. and human DNA from peripheral blood mononuclear cells. (3) Electron microscopy (EM) was performed upon 13 SCAS, 8 CCBAV and 2 control valves.

RESULTS

All three methods failed to detect the presence of C. pneumoniae in any of the 60 aortic valves examined. False positive IF staining was encountered in 81% of test valves and in 76% of negative control valve sections (positive in calcified material due to nonspecific binding of FITC-conjugated secondary antibody). No staining was observed in the negative control stomach sections.

CONCLUSIONS

This study failed to detect C. pneumoniae within aortic valves showing SCAS or CCBAV. Studies using IF alone to detect C. pneumoniae in calcified tissues should be interpreted with caution, since nonspecific binding of FITC-conjugated secondary antibody by calcium in the cusps may be misinterpreted as evidence of Chlamydia. The use of appropriate controls and ancillary methods for the identification of C. pneumoniae are important in this regard.

Floppy aortic valves without aortic root dilatation: clinical, histologic, and ultrastructural studies

Gross anatomic, histologic and ultrastructural studies were made on 32 floppy aortic valves (FAVs) resected at the time of aortic valvular replacement for aortic regurgitation. Patients with the FAVs had relatively long clinical courses and had severe aortic regurgitation with mild symptoms of heart failure. The sizes of the mechanical valves implanted in the patients with FAVs were not large, indicating that the aortic regurgitation in these patients was not worsened by dilatation of the aortic ring. Two types of FAVs were recognized grossly, according to whether they showed abnormal cuspal thickening or thinning. Accumulations of myxoid material in the spongiosa were found in all FAVs, regardless of cuspal gross morphology. Histologically, the collagen fibers were sparse and irregularly arranged and elastic fibers were disrupted and finely granular in the myxomaotus areas of FAVs. Ultrastructurally, the myxomatous material consisted of numerous star-shaped proteoglycan granules associated with spiraling collagen fibrils and abnormal elastic fibers. Numerous spiraling collagen fibrils were observed especially at the border area of myxomatous change that extended from the spongiosa into the fibrosa. Abnormal elastic fibers had either a granular appearance of their amorphous components without microfibrils, or irregularly arranged masses of microfibrils without amorphous components. These abnormalities of connective tissue components, resulting from defective formation and/or increased degradation were similar to those in floppy mitral valves, and were related to the floppiness of cardiac valves.

Mycoplasma pneumoniae and Chlamydia pneumoniae in calcified nodules of aortic stenotic valves

Aortic Valve Stenosis (AVS) has been explained as an atherosclerotic process of the valve as they often exhibit inflammatory changes with infiltration of macrophages, T lymphocytes and lipid infiltration. The present study investigated whether the bacteria Chlamydia pneumoniae (CP) and Mycoplasma pneumoniae (MP), detected previously in atherosclerotic plaques, are also present in AVS. Ten valves surgically removed from patients with AVS were analyzed by immunohistochemistry, in situ hybridization, and electron microscopy. The mean and standard deviation of the percentage areas occupied by CP antigens and MP - DNA were respectively 6.21 +/- 5.41 and 2.27 +/- 2.06 in calcified foci; 2.8 +/- 3.33 and 1.78+/- 3.63 in surrounding fibrotic areas, and 0.21 +/- 0.17 and 0.12 +/- 0.13 in less injured parts of the valve. There was higher amount of CP and MP in the calcified foci and in the surrounded fibrosis than in more preserved valvular regions. In conclusion, the fact that there were greater amounts of CP and MP in calcification foci of AVS favors the hypothesis that AS is not an inevitable degenerative process due to aging, but rather that it may be a response to the presence of these bacteria, similarly to the morphology detected in atherosclerosis damage.

A precise radiographic technique for the measurement of dimensional changes in heart valve biomaterials following fixation

Accurate tissue thickness measurements are difficult to acquire by present techniques. Error is introduced by tissue compression during measurements or by tissue processing prior to measurement. In the field of valve replacement, tissue dimensional changes from fixation prior to implantation may predispose implants to premature tissue failure and it becomes important to have an accurate method for comparing cusp dimensions pre- and post-fixation. A new approach is to use high-resolution digital radiography to make thickness maps of entire specimens. For 25 matched porcine aortic valve cusps, we have evaluated this technique's ability to measure and compare thickness, surface area and volume before and after 7 days of aldehyde fixation. Digital radiographs were acquired pre- and post-0.5% glutaraldehyde (n=13) or 10% formaldehyde (n=12) fixation. Mean thickness, surface area, volume and four measurements to evaluate shape differences with fixation were obtained and compared pre- and post-fixation using paired t tests. The results demonstrate that this X-ray imaging technique can provide dimensions of matched fresh and fixed specimens and is sensitive enough to show statistically significant changes due to fixation. These findings also illustrate that aldehyde fixation can cause tissue contraction resulting in a significant overall increase in tissue thickness and a decrease in surface area. This technique could be used to gain further insights into tissue anatomy and mechanics.

Cause of degenerative disease of the trileaflet aortic valve: review of subject and presentation of a new theory

Risk factors for both atherosclerotic aortic wall disease and degenerative disease of the trileaflet aortic valve are very similar if not identical. This correlation grows even stronger as the person advances in years. Because of this, it is the prevailing view that sclerosis of the trileaflet aortic valve, unless previously affected by septic or rheumatic endocarditis, is a disease similar in origin to sclerosis of the aortic wall, ie, degenerative aortic valve disease is arteriosclerosis of the aortic valve. Our studies challenge these views. The aortic valve is a functional assembly composed of the three cusps, corresponding sinuses, and the sino-tubular junction, characterized not only by morphologic features but also by its functional properties, which together create an environment that is optimal for distribution of diastolic pressure load and assures proper and timely valve opening and closure. Our more recent experiments also demonstrate that loss of aortic wall compliance at the level of the sinuses leads to significant stress-overload on the aortic leaflets and it is likely to start a chain of events, which begins with minor changes in their microstructure, then continues in more evident sclerosis, and finally ends in gross distortion or calcification of the cusps. The loss of the "pull-and-release" process may also play a part in disintegration of bioprosthetic valves and in degeneration of native aortic valves encased in noncompliant prostheses.

Aortic valve calcification: its significance and limitation as a marker for coronary artery disease

Aortic valve calcification (AVC) is correlated with atherosclerotic risk factors; however, its significance remains largely unknown. The aim of this study was to investigate whether AVC detected by transthoracic echocardiography can be a useful marker for the identification of significant coronary artery disease (CAD), particularly in elderly patients. The study included 432 consecutive patients with suspected CAD who were admitted for the first time for coronary angiography. Two-dimensional transthoracic echocardiography and selective coronary angiography were performed in all patients. Aortic valve calcification was defined as bright dense echoes of > 1 mm on one or more cusps and decreased mobility of the involved cusp. Aortic valve calcification was detected in 64 of the 337 patients with significant CAD, but only in 9 of 95 cases with normal or mildly stenotic coronary arteries (19% vs 9%, p < 0.001). The severity of coronary artery disease (defined as the number of obstructed vessels) was not related to the presence of AVC (p > 0.05). Stepwise multiple logistic regression analysis of the study patients revealed only age (p=0.003, odds ratio= 1.56) and AVC (p<0.001, odds ratio = 2.03) as independent predictors of CAD. When the study population was divided into two groups as those below (n = 338) and above (n = 94) 75 years old, AVC failed to be a predictor of CAD in those >75 years old (p > 0.05, odds ratio = 0.8) while it remained the most significant predictor of CAD (p<0.001, odds ratio=2.19 in patients aged <75 years. In conclusion, detection of AVC by transthoracic echocardiography may be a useful noninvasive marker for identification of significant CAD in patients younger than 75 years old. Its clinical usefulness is limited in elderly patients.

Aortic valve sclerosis as a marker of active atherosclerosis

Aortic sclerosis is a calcific disease of the aortic valvular leaflets defined as focal leaflet thickening without significant obstruction to left ventricular outflow. Several clinical factors are associated with calcific aortic valve disease, including male sex, smoking, hypertension, age, hypercholesterolemia, and diabetes. Histologic and biochemical studies suggest similarities between the mechanisms involved in the development of aortic sclerosis and atherosclerosis, suggesting these two diseases may share common pathophysiologic mechanisms. In a recent prospective trial, the presence of aortic sclerosis was associated with an approximately 50% increase in cardiovascular mortality and myocardial infarction, even after correction for age, gender, known coronary artery disease, and clinical factors associated with a aortic sclerosis.

Advances towards understanding heart valve response to injury

BACKGROUND

Composed of endocardial endothelial, valvular interstitial, cardiac muscle, and smooth muscle cells (SMC), heart valves are prone to various pathologic conditions the morphology of which has been well described. The morphology of diseased valves suggest that the "response to injury" process occurs in these valves, and is associated with an accumulation of interstitial cells and matrix, valvular inflammation and calcification, conditions that lead to dysfunction. The purpose of this study is to describe the current knowledge of the regulation of the valvular "response to injury" process, since we feel that this paradigm is essential to understanding valve disease.

METHODS

The pertinent literature relating to the cell and molecular biology of valvular repair, and specifically interstitial cell function in valve repair, is reviewed.

RESULTS

The cell and molecular biology of valve interstitial cells are poorly understood. Molecules regulating some of the aspects of the "response to injury" process have been studied, however, the signal transduction pathways, gene activation, and interactions of bioactive molecules with each other, with cells, and with the matrix have not been characterized. Initial studies identify the cell and molecular biology of interstitial cells to be an important area of research. Agents that have been studied include nitric oxide (NO) and FGF-2 and several matrix-related proteins including osteopontin. The present review suggests several directions for future study and a working model of valvular repair is presented.

DISCUSSION

The regulation of the "response to injury" process in the human heart valve is still largely unknown. The cell and molecular events and processes that occur in heart valve function and repair remain poorly understood. These events and processes are vital to our understanding of the pathobiology of heart valve disease, and to the successful design of tissue engineered replacement valves.