Non-inflammatory aortic root disease and floppy aortic valve as cause of isolated regurgitation: a clinico-morphologic study

Pathobiology of Idiopathic Ascending Aortic Aneurysms

The majority of ascending aortic aneurysms cannot be related to any specific etiology and should be qualified as idiopathic. The pathobiology of ascending aortic aneurysms remains incompletely understood. Data from direct study are still scarce and often limited because of patient heterogenicity. Currently available information suggests that destructive remodeling of the aortic wall, inflammation and angiogenesis, biomechanical wall stress, and molecular genetics are relevant mechanisms of idiopathic ascending aortic aneurysm formation and progression. Further understanding of these mechanisms will likely provide novel diagnostic, prognostic, and therapeutical tools for the clinician.

Aortic valve repair update

The key for successful valve repair is full understanding of the regurgitant mechanism and sufficient evaluation of the valve. Currently, multidetector computed tomography has been introduced for evaluation. The aortic valve can be analyzed in details preoperatively. The main causes of aortic regurgitation (AR) in the adult population are degenerative leaflet change and annulus dilatation. Restoration to normal structure can be accomplished mainly by plication. Central leaflet plication near the Arantius nodule is a simple technique for redundant tissue. For leaflet deficiency, pericardial patch plasty may be an option. No universal technique exists for plication of the aortic annulus. The valve-sparing aortic root replacement firmly stabilizes the ventriculo-aortic junction (VAJ) and assures repair durability even in patients with mild to moderate root dilatation. Subcommissural annuloplasty (Cabrol stitch) does not seem sufficient for the prevention of VAJ dilatation. Circumferential annuloplasties may have a greater potential. However, convenient device for annular plication is still in development. The bicuspid aortic valve is a congenital heart valve lesion. A basic technique is free margin plication of the fused leaflet. Aortic root dilatation may contribute to AR severity. Valve-sparing aortic root replacement may improve repair durability. Considering the great advances in valve repair, young patients with AR should be informed that valve repair is a promising option for surgical treatment.

Proteomic profiling of medial degeneration in human ascending aorta

OBJECTIVE

The objective of this study was the construction of a reference map for aortic medial degeneration by a proteomic approach.

DESIGN AND METHODS

A proteomic profiling of the media of human ascending aorta was performed by two-dimensional electrophoresis and MALDI-TOF mass spectrometry.

RESULTS

A reliable protocol for two-dimensional electrophoresis analysis of human aortic media proteins was developed allowing the selection and identification of 52 spots. Protein identifications revealed that the predominant vascular smooth muscle cell proteins isolated from grade 1 aortic medial degeneration (MD) included proteins involved in muscle contraction, protein folding, cytoskeletal structure and metabolic processes, and those with antioxidant or transport functions. The most populated functional classes were those related to muscle contraction and cytoskeletal proteins, including actin, calmodulin, calponin, myosin light chain, tropomyosin, vimentin, profilin and transgelin.

CONCLUSIONS

The obtained aortic MD proteomic profile provides a relevant background for future studies aimed to find further specific molecular changes potentially related to the aortic MD process.

Scanning Electron Microscopy of Aortic Medial Changes in Aortic Ascending Dilatation

The study of cystic cavities and collagen fibers fragmentation is useful to for a better knowledge of pathogenesis and surgical therapy of medial ascending aortic degeneration. Thus, the aim of this study was to describe by scanning electron microscopy the surfaces and shape of the cysts, measure their area, and identify microcystic spaces related to this degenerative disease. Scanning electron microscopy analysis was performed in 16 out of 36 patients who underwent surgery for ascending aorta dilatation with associated aortic valve disease. The aortic medial wall showed a cribrose appearance at low magnification (x50-100) and the intima was effuse. At high magnification (x500-2000), small cavities (clefts) lined by normal or fragmented elastic fibers and large cavities (pseudocystes) with anfractuous borders lined by fragmented elastic fibers and smooth muscle cells were observed. Furthermore, in the outer media wall microvessels lined by endothelium were also observed. These changes were lacking or less pronounced in normal aorta. SEM allows one to better identify the pathological cavities and to differentiate them from microvessels. These pathological cavities are more numerous and larger in the convexity than in the concavity of the aorta in according to our previous morphological and morphometric findings in asymmetrical aorta dilatation.

[Pathobiology of idiopathic ascending aortic aneurysms]

BACKGROUND

The majority of ascending aortic aneurysms cannot be related to any specific etiology and should be qualified as idiopathic. The incidence of this disease is increasing in the population of the developed countries but its pathobiology is poorly understood.

AIM

This article is reviewing the publications concerning the pathobiology of idiopathic ascending aortic aneurysms.

SOURCES

A PubMed search on articles published in English or French, between January 1965 and December 2007, on key-words << aortic root >>, << ascending aorta >>, << aortic arch >>, << thoracic aorta >>, << aneurysm >>, << dilatation >> and << dissection >> was undertaken. Articles on aneurysms related to inflammatory and infectious diseases, congenital or genetic syndromes were excluded.

RESULTS

The presented data suggests that destructive remodeling of the aortic wall, inflammation and angiogenesis, biomechanical wall stress, and molecular genetics are relevant mechanisms of idiopathic ascending aortic aneurysm formation and progression.

LIMITS

Sparse data available from few direct studies offer limited knowledge on pathobiology of idiopathic ascending aortic aneurysms.

CONCLUSION

A more intimate knowledge of the triggers and perpetrating factors of this disease might offer new diagnostic and treatment options.

Ascending aorta dilatation in aortic valve disease: morphological analysis of medial changes

We investigated whether and how the severity of medial degeneration lesions varies along the circumference of the dilated intrapericardial aorta. Two groups of aortic wall specimens, respectively harvested in the convexity and concavity of ascending aorta in 72 patients undergoing surgery for dilatation of the intrapericardial aorta associated with aortic valve disease, were separately sent for pathology, morphometry, and ultrastructural examination. Cystic medial necrosis, fibrosis, and elastic fiber fragmentation were classified into three degrees of severity; their mean degree and morphometric findings in the convexity and in the concavity specimens were compared by paired t-test. Correlation between echocardiographic degree of aortic dilatation and severity of medial degeneration was assessed separately for each of the two groups of specimens. Morphologically, medial degeneration was found in all cases; a higher mean degree was found in the convexity group (2.39 +/- 0.58 vs 1.44 +/- 0.65 in the concavity group; P < 0.001). At morphometry normal smooth muscle cells in the convexity specimens were significantly reduced (P = 0.007); the length (P = 0.012) and number (P = 0.009) of elastic fibers reduced and increased, respectively. Moreover, in the convexity specimens a significantly smaller amount of smooth muscle cells and an increase of immunohistochemical labeling of apoptosis-associated proteins in the subintimal layer of the media was noticed. Correlation between aortic ratio and medial degeneration degree was significant in the convexity group (P < 0.001), but not in the concavity group (P = 0.249). Scanning electron microscopy analysis confirmed morphological results and allowed us to better distinguish the early pathological cavities from the microvessels, which were in the outer media in normal aorta and ubiquitous in aortitis or atherosclerosis. Electron transmission microscopy analysis showed changes in the extracellular matrix and smooth muscle cells, and these changes increased from the intima to the adventitial layer of the media. In dilated intrapericardial aorta, medial degeneration changes and expression of apoptosis-associated proteins are more marked in the ascending aorta convexity, likely due to hemodynamic stress asymmetry. Ultrastructural findings allow us to distinguish the early medial changes not yet evident on light microscopy.

Peripartum presentation of an acute aortic dissection

We report the case of an acute type A aortic dissection occurring in a 35-year-old parturient. The initial diagnosis was missed; a subsequent emergency Caesarean section 3 weeks after presentation was followed by the development of left ventricular failure and pulmonary oedema in the early postoperative period. Echocardiography confirmed the diagnosis of aortic dissection and the patient underwent a successful surgical repair.

Aortic Valve Repair Using a Differentiated Surgical Strategy

BACKGROUND

Reconstruction of the aortic valve for aortic regurgitation (AR) remains challenging, in part because of not only cusp or root pathology but also a combination of both can be responsible for this valve dysfunction. We have systematically tailored the repair to the individual pathology of cusps and root.

METHODS

Between October 1995 and August 2003, aortic valve repair was performed in 282 of 493 patients undergoing surgery for AR and concomitant disease. Root dilatation was corrected by subcommissural plication (n=59), supracommissural aortic replacement (n=27), root remodeling (n=175), or valve reimplantation within a graft (n=24). Cusp prolapse was corrected by plication of the free margin (n=157) or triangular resection (n =36), cusp defects were closed with a pericardial patch (n=16). Additional procedures were arch replacement (n=114), coronary artery bypass graft (n=60) or mitral repair (n=24). All patients were followed-up (follow-up 99.6% complete), and cumulative follow-up was 8425 patient-months (mean, 33+/-27 months).Results- Eleven patients died in hospital (3.9%). Nine patients underwent reoperation for recurrent AR (3.3%). Actuarial freedom from AR grade > or =II at 5 years was 81% for isolated valve repair, 84% for isolated root replacement, and 94% for combination of both; actuarial freedom from reoperation at 5 years was 93%, 95%, and 98%, respectively. No thromboembolic events occurred, and there was 1 episode of endocarditis 4.5 years postoperatively.

CONCLUSIONS

Aortic valve repair is feasible even for complex mechanisms of AR with a systematic and individually tailored approach. Operative mortality is low and mid-term durability is encouraging. The incidence of valve-related morbidity is low compared with valve replacement.

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.

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.

Medial degeneration does not involve uniformly the whole ascending aorta: morphological, biochemical and clinical correlations

OBJECTIVE

To investigate whether and how the severity of medial degeneration (MD) lesions varies along the circumference of the dilated intrapericardial aorta.

METHODS

Two groups of aortic wall specimens, respectively harvested 1cm distal to the non-coronary (NC) sinus (right postero-lateral wall) and to the right coronary sinus (anterior wall) in 22 patients undergoing surgery for dilatation of the intrapericardial aorta associated with aortic valve disease, were separately sent for pathology, morphometry and ultrastructural examination. MD lesions found at histology were classified into three degrees of severity. MD mean degree and morphometric findings in postero-lateral ('NC') and anterior ('coronary') specimens were compared by paired t-test. Correlation between degree of aortic dilatation at echocardiography and severity of MD was assessed separately for each of the two groups of specimens. After the preliminary results of the morphological study, we decided to send the specimens for biochemical investigation of protein electrophoretic patterns. This was performed in the last seven patients of this series.

RESULTS

At histology, MD was found in all cases. A higher mean MD degree was found in the NC group (2.59+/-0.50 versus 1.59+/-0.67 in the coronary group; P<0.001). At morphometry, normal smooth muscle cells in the NC specimens were significantly reduced (P=0.012) and the length (P=0.011) and number (P=0.015) of elastic fibres reduced and increased, respectively. Correlation between aortic ratio and MD degree was significant in the NC specimens (P<0.001), not in the coronary ones (P=0.227). Quantitative differences between coronary and NC proteins from the same patient and between coronary proteins from different patients were found at electrophoresis. However, at this stage of the study, the sample was too small to allow for the identification of proteins involved in those differences.

CONCLUSIONS

MD lesions in dilated intrapericardial aorta are more severe in the right postero-lateral wall area, likely due to haemodynamic stress asymmetry.

Mechanisms of aortic valve incompetence: finite element modeling of aortic root dilatation

BACKGROUND

Idiopathic root dilatation often results in dysfunction of an otherwise normal aortic valve. To examine the effect of root dilatation on leaflet stress, strain, and coaptation, we utilized a finite element model.

METHODS

The normal model incorporated the geometry, tissue thickness, stiffness, and collagen fiber alignment of normal human roots and valves. We evaluated four dilatation models in which diameters of the aortic root were dilated by 5%, 15%, 30%, and 50%. Regional stress and strain were evaluated and leaflet coaptation percent was calculated under diastolic pressure.

RESULTS

Root dilatation significantly increased regional leaflet stress and strain beyond that found in the normal model. Stress increases ranged from 57% to 399% and strain increases ranged from 39% to 189% in the 50% dilatation model. Leaflet stress and strain were disproportionately high at the attachment edge and coaptation area. Leaflet coaptation was decreased by 18% in the 50% root dilatation model.

CONCLUSIONS

Idiopathic root dilatation significantly increases leaflet stress and strain and reduces coaptation in an otherwise normal aortic valve. These alterations may affect valve-sparing aortic root replacement procedures.

Causes of isolated aortic insufficiency in an urban population in the 1990s a review of 56 surgical pathology cases

Until recently, the cause of isolated aortic insufficiency (AI) was usually thought to be inflammatory or rheumatic in most cases. However, at our institution we have noted a high prevalence of myxomatous degeneration (MD) in aortic valves removed for AI. In this study we report anatomic observations on valves from 56 consecutive patients with isolated AI undergoing aortic valve replacement surgery. Fifty-six consecutive aortic valves removed at our institution from 1994 to 1996 for isolated AI and/or aortic aneurysm were reviewed. Anatomic features were compared with clinical history and echocardiographic data. The anatomic results were also compared to 22 age-matched control aortic valves obtained at autopsy. In 13/56 cases (23%), a specific valvular cause of AI was determined (infectious endocarditis, seven cases; chronic rheumatic disease, four cases; congenital bicuspid valve, two cases). Of the remaining (idiopathic) 43 cases, 18 (42%) had severe isolated MD defined as >50% expansion of the spongiosa and disruption of the fibrosa by the deposition of acid mucopolysaccharides in the absence of severe calcification, fibrosis, or other pathologic findings. Only 1/22 aortic valves from the autopsy controls had severe MD. Eighteen of the 56 patients also had a clinical history of aortic dilatation/aneurysm of which 12 were confirmed to be dilated by echocardiographic criteria. Of these 12, five (42%) had MD of the aortic valve only, three (25%) had both MD and cystic medial degeneration (CMD) of the aorta, two (17%) had CMD of the aorta only, and two (17%) had no specific diagnosis. Isolated MD of the aortic valve is the most common cause of isolated AI in our patient population. Furthermore, in a subset of non-Marfan's patients with both AI and dilatation of the aortic root/aortic aneurysm the incidence of MD is even higher (67%). These results suggest that there is overlap between MD and CMD in non-Marfan's patients and that both entities may be part of a spectrum of a generalized connective tissue disorder.