DISCRETE MEMBRANOUS SUBAORTIC STENOSIS: POSTOPERATIVE REVERSION OF AORTIC VALVE ECHOCARDIOGRAM TO NORMAL

Clinical, hemodynamic, angiographic and echocardiographic findings in a patient with discrete membranous subaortic stenosis are presented. Echocardiography revealed evidence of a normal mitral valve and abnormal movement of the aortic valve with poor motion and fluttering of the anterior cusp. After a subvalvular membrane subjacent to the aortic valve cusp was excised, postoperative echocardiographic study showed normal movement of the aortic valve.     

THE VALUE OF ECHOCARDIOGRAPHY IN THE MANAGEMENT OF ACUTE AORTIC INSUFFICIENCY

Three cases of acute rupture of the aortic cusp complicating bacterial endocarditis are described. Special emphasis is placed on the value of serial echocardiography as a means of identifying progressive changes in aortic valve anatomy during the destructive process of the disease. Prior to the results of blood cultures, an echocardiogram confirmed a diagnosis of vegetations on the valve cusps. It also demonstrated flailing of the aortic cusp, which was confirmed at operation. Echocardiographic findings of flailing aortic valves in these patients coincided with the onset of acute aortic insufficiency and contributed to the timing of surgical intervention for replacement of the affected valves.     

ECHOCARDIOGRAPHIC FINDINGS IN BACTERIAL ENDOCARDITIS

Fifteen echocardiographic recordings in nine patients with bacterial endocarditis revealed vegetations in six cases. The vegetations appeared as uneven, irregular thickening of a valve, a mass of shaggy, dense echoes attached to a leaflet or cusp, or a mass of irregular dense echoes in the cavity or outflow tract of the left ventricle. Such findings were seen only on the echocardiograms of very sick patients with severe valvular lesions. Three patients had flail mitral valves. Echocardiography was not helpful in differentiating between active and healed lesions. Problems in the identification and differential diagnosis of vegetations shown on echocardiograms are discussed.     

Prolapse of noncoronary aortic cusp with severe aortic regurgitation after a tear of the aortic root

A patient with acute aortic regurgitation, a dissecting aneurysm with a localized transverse tear just above the aortic valve, and an aortic noncoronary cusp eversion is discussed. The valvular defects were considered to be of recent etiology, and the patient underwent successful aortic valve replacement and repair of the dissection.     

CROSS-SECTIONAL ECHOCARDIOGRAPHIC FINDINGS IN VEGETATIVE AORTIC VALVE ENDOCARDITIS

M-mode echocardiograms of two patients with bacterial endocarditis of approximately 4 months' duration showed dense echoes in the area of the aortic valve. In one patient, who had no prior abnormal cardiac findings, the echoes were clearly suggestive of valvular vegetations. The second patient, however, was known to have had aortic valve disease and a systolic murmur for more than a decade; therefore, dense echoes arising from the aortic valve also could have resulted from valvular calcification. In both patients, cross-sectional echocardiography provided important information. In the first patient, retrograde cardiac catheterization was prevented by large and highly mobile masses attached to the aortic cusps that prolapsed into the left ventricular outflow tract during diastole. Aortic valve replacement without further hemodynamic evaluation was recommended. In the second patient, whose blood cultures remained negative after the acute phase of his illness had been treated, cross-sectional echocardiography showed large vegetations on the aortic valve. Intraoperative findings confirmed the echocardiographic interpretation in each case.     

Systolic fluid–structure interaction model of the congenitally bicuspid aortic valve: assessment of modelling requirements

A transient fluid–structure interaction (FSI) model of a congenitally bicuspid aortic valve has been developed which allows simultaneous calculation of fluid flow and structural deformation. The valve is modelled during the systolic phase (the stage when blood pressure is elevated within the heart to pump blood to the body). The geometry was simplified to represent the bicuspid aortic valve in two dimensions. A congenital bicuspid valve is compared within the aortic root only and within the aortic arch. Symmetric and asymmetric cusps were simulated, along with differences in mechanical properties. A moving arbitrary Lagrange–Euler mesh was used to allow FSI. The FSI model requires blood flow to induce valve opening and induced strains in the region of 10%. It was determined that bicuspid aortic valve simulations required the inclusion of the ascending aorta and aortic arch. The flow patterns developed were sensitive to cusp asymmetry and differences in mechanical properties. Stiffening of the valve amplified peak velocities, and recirculation which developed in the ascending aorta. Model predictions demonstrate the need to take into account the category, including any existing cusp asymmetry, of a congenital bicuspid aortic valve when simulating its fluid flow and mechanics.     

Regional structure–function relationships in mouse aortic valve tissue

Site-specific biomechanical properties of the aortic valve play an important role in native valve function, and alterations in these properties may reflect mechanisms of degeneration and disease. Small animals such as targeted mutagenesis mice provide a powerful approach to model human valve disease pathogenesis; however, physical mechanical testing in small animals is limited by valve tissue size. Aortic valves are comprised of highly organized extracellular matrix compartmentalized in cusp and annulus regions, which have different functions. The objective of this study was to measure regional mechanical properties of mouse aortic valve tissue using a modified micropipette aspiration technique. Aortic valves were isolated from juvenile, adult and aged adult C57BL/6 wild type mice. Tissue tensile stiffness was determined for annulus and cusp regions using a half-space punch model. Stiffness for the annulus region was significantly higher compared to the cusp region at all stages. Further, aged adult valve tissue had decreased stiffness in both the cusp and annulus. Quantitative histochemical analysis revealed a collagen-rich annulus and a proteoglycan-rich cusp at all stages. In aged adult valves, there was proteoglycan infiltration of the annulus hinge, consistent with the observed mechanical differences over time. These findings indicate that valve tissue biomechanical properties vary in wild type mice in a region-specific and age-related manner. The micropipette aspiration technique provides a promising approach for studies of valve structure and function in small animal models, such as transgenic mouse models of valve disease.     

The Changing Pattern of Aortic Valve Repair

The changes and improvements in the surgical treatment of aortic valve disease in 296 patients, who were operated on between 1953 and 1965, are illustrated and discussed in general terms. Several of the early techniques, such as transventricular dilation, insertion of a homograft aortic valve in the descending thoracic aorta, fabric replacement of one cusp or the entire valve, and ice-chip arrest of the heart, are now obsolete. Total replacement with a ball-valve prosthesis or an aortic valve homograft while the coronary arteries are perfused with blood is the currently popular technique. The results of a hemodynamic follow-up study two years after surgery are also included.     

Modeling leaflet correction techniques in aortic valve repair: A finite element study

In aortic valve sparing surgery, cusp prolapse is a common cause of residual aortic insufficiency. To correct cusp pathology, native leaflets of the valve frequently require adjustment which can be performed using a variety of described correction techniques, such as central or commissural plication, or resuspension of the leaflet free margin. The practical question then arises of determining which surgical technique provides the best valve performance with the most physiologic coaptation. To answer this question, we created a new finite element model with the ability to simulate physiologic function in normal valves, and aortic insufficiency due to leaflet prolapse in asymmetric, diseased or sub-optimally repaired valves. The existing leaflet correction techniques were simulated in a controlled situation, and the performance of the repaired valve was quantified in terms of maximum leaflets stress, valve orifice area, valve opening and closing characteristics as well as total coaptation area in diastole. On the one hand, the existing leaflet correction techniques were shown not to adversely affect the dynamic properties of the repaired valves. On the other hand, leaflet resuspension appeared as the best technique compared to central or commissural leaflet plication. It was the only method able to achieve symmetric competence and fix an individual leaflet prolapse while simultaneously restoring normal values for mechanical stress, valve orifice area and coaptation area.     

Ruptured sinus Valsalva aneurysm, a rare cause of heart failure

A 35-year-old male presented with symptoms of shortness of breath and ankle oedema which had developed within a few days. The symptoms had started suddenly following a mountain bike trip. Physical examination revealed a blood pressure of 90/40 mmHg, no fever and a continuous murmur on auscultation of the heart, as well as signs of left and right heart failure. Echocardiography showed moderate pericardial effusion and a hyperdynamic left and right ventricle with signs of right ventricular volume overload. Turbulent flow was seen in the aortic root and a shunt was demonstrated from the aortic root to the right atrium (figure 1) through a ruptured sinus Valsalva aneurysm of the non-coronary cusp (figure 2).     

Asymptomatic papillary fibroelastoma of the aortic valve

A previously healthy 63-year-old woman with multiple risk factors for coronary artery disease was referred to the outpatient clinic with a three-month history of atypical chest pain. At physical examination no abnormalities could be detected and the ECG was completely normal. At transthoracic echocardiography and transoesophageal echocardiography a mass, 1 cm in diameter and attached to the right coronary cusp of the aortic valve, was detected. The mass had the echocardiographic appearance of a nonhomogeneous, round, dense, mobile structure, typical features of a fibroelastoma (figure 1). On dipyridamole-thallium scintigraphy, no coronary insufficiency could be demonstrated. Since cardiac papillary fibroelastomas are associated with a risk of thromboembolic events, the patient underwent complete tumour excision by a simple shave excision (figure 2).     

Balloon dilatation of the aortic valve for inoperable aortic stenosis.

The place of balloon dilatation of the aortic valve in the treatment of calcific aortic stenosis is controversial. Thirty two patients (mean age 76) in whom valve replacement was contraindicated were followed up for three to 24 months (mean 8); 25 were in functional class III or IV according to the New York Heart Association''s classification. Major complications of the procedure occurred in four patients. Echocardiography and Doppler studies were performed before operation and before discharge in 28 patients, and the area of the valve was measured again six to 50 (mean 23) weeks after operation in 11 patients. The peak to peak aortic pressure gradient fell from a mean of 65 (SD 24) to 46 (20) mm Hg, but the area of the aortic valve, measured by Doppler echocardiography, in 18 patients showed a modest but significant increase, from 0.61 (0.16) to 0.74 (0.23) cm2. One month after dilatation, 29 patients were alive, of whom 17 had improved symptoms. Only two had lasting clinical benefit. Sixteen patients died, 12 of a cardiac cause. The estimated one year survival rate was 49%. Six patients underwent or required valve replacement because of persisting symptoms. In view of its limited long term efficacy balloon dilatation of the aortic valve should be used only for patients with severe symptoms whose life expectancy is limited by other disease or who are considered to be unsuitable for valve replacement. It may have a role in improving the condition of patients who present with cardiogenic shock or pulmonary oedema before valve replacement is undertaken.     

Imaging analysis of collagen fiber networks in cusps of porcine aortic valves: effect of their local distribution and alignment on valve functionality

The cusps of native aortic valve (AV) are composed of collagen bundles embedded in soft tissue, creating a heterogenic tissue with asymmetric alignment in each cusp. This study compares native collagen fiber networks (CFNs) with a goal to better understand their influence on stress distribution and valve kinematics. Images of CFNs from five porcine tricuspid AVs are analyzed and fluid-structure interaction models are generated based on them. Although the valves had similar overall kinematics, the CFNs had distinctive influence on local mechanics. The regions with dilute CFN are more prone to damage since they are subjected to higher stress magnitudes.     

COMBINED REPLACEMENT OF THE AORTIC VALVE AND ASCENDING AORTA IN JEHOVAH'S WITNESSES: REPORT OF TWO CASES

Two Jehovah's Witnesses with large ascending thoracic aortic aneurysms and aortic insufficiency secondary to annuloaortic ectasia underwent successful combined replacement of the aortic valve and the ascending aorta. One patient received a composite graft containing an aortic valve prosthesis, which necessitated supravalvular coronary ostia reimplantation; the other patient underwent separate aortic valve and left supracoronary ascending aneurysm replacement, with reimplantation of the right coronary ostium into the graft. No blood or blood derivatives were administered. Both patients had uneventful recoveries and continue to do well. To our knowledge, they represent the first reported cases of successful combined replacement of the aortic valve and ascending aorta in Jehovah's Witnesses.     

DIASTOLIC OPENING OF THE AORTIC VALVE (AV) IN A CASE OF AORTIC INSUFFICIENCY DUE TO AV FENESTRATION

A patient with severe aortic insufficiency due to fenestration of the non-coronary aortic valve leaflet is described. A preoperative echocardiogram demonstrated early closure of the mitral valve and early diastolic separation of the aortic valve leaflets. These findings disappeared after partial surgical correction and subsequent hemodynamic improvement. Premature opening of the aortic valve is common in severe aortic insufficiency.     

Molecular and developmental mechanisms of congenital heart valve disease

Congenital heart disease occurs in approximately 1% of all live births and includes structural abnormalities of the heart valves. However, this statistic underestimates congenital valve lesions, such as bicuspic aortic valve (BAV) and mitral valve prolapse (MVP), that typically become apparent later in life as progressive valve dysfunction and disease. At present, the standard treatment for valve disease is replacement, and approximately 95,000 surgical procedures are performed each year in the United States. The most common forms of congenital valve disease include abnormal valve cusp morphogenesis, as in the case of BAV, or defects in extracellular matrix (ECM) organization and homeostasis, as occurs in MVP. The etiology of these common valve diseases is largely unknown. However, the study of murine and avian model systems, along with human genetic linkage studies, have led to the identification of genes and regulatory processes that contribute to valve structural malformations and disease. This review focuses on the current understanding and therapeutic implications of molecular regulatory pathways that control valve development and contribute to valve disease.     

Balloon aortic valvuloplasty as a bridge to aortic valve replacement in a patient with severe calcific aortic stenosis

This case report describes a patient with severe calcific aortic stenosis who was initially considered inoperable because of a very poor left ventricular function and severe pulmonary hypertension. After balloon aortic valvuloplasty, the clinical and haemodynamic status of the patient improved to such an extent that subsequent aortic valve replacement was considered possible and eventually proved to be successful. Balloon aortic valvuloplasty has value as a potential bridge to aortic valve replacement when the risks for surgery are considered to be too high.     

Biaxial mechanical properties of the native and glutaraldehyde-treated aortic valve cusp: Part II--A structural constitutive model

We have formulated the first constitutive model to describe the complete measured planar biaxial stress-strain relationship of the native and glutaraldehyde-treated aortic valve cusp using a structurally guided approach. When applied to native, zero-pressure fixed, and low-pressure fixed cusps, only three parameters were needed to simulate fully the highly anisotropic, and nonlinear in-plane biaxial mechanical behavior. Differences in the behavior of the native and zero- and low-pressure fixed cusps were found to be primarily due to changes in the effective fiber stress-strain behavior. Further, the model was able to account for the effects of small (< 10 deg) misalignments in the cuspal specimens with respect to the biaxial test axes that increased the accuracy of the model material parameters. Although based upon a simplified cuspal structure, the model underscored the role of the angular orientation of the fibers that completely accounted for extreme mechanical anisotropy and pronounced axial coupling. Knowledge of the mechanics of the aortic cusp derived from this model may aid in the understanding of fatigue damage in bioprosthetic heart valves and, potentially, lay the groundwork for the design of tissue-engineered scaffolds for replacement heart valves.     

Open-Heart Correction of Mitral Valvular Disease: Review of 30 Cases

Thirty patients with mitral valve disease operated upon by the open-heart technique during the period 1958-1962 were studied. In 15 insufficiency predominated. Clinical, radiological and pathological findings included the following: aortic valve disease is the commonest associated lesion; cusp calcification is uncommon in mitral insufficiency; left atrial enlargement is more pronounced in mitral insufficiency; a relaxed annulus is the commonest pathological lesion associated with mitral insufficiency, with ruptured chordae in second place. Five of the 15 patients with mitral insufficiency and four of the 15 with mitral stenosis died during the postoperative period, while clinical improvement was apparent in seven and 11, in the respective groups. The standard techniques of annuloplasty, suturing of ruptured chordae, and open commissurotomy were found to provide satisfactory results. Partial Ivalon prosthetic replacement was unsatisfactory. The study suggests that a more liberal use of the open-heart procedure in surgical correction of complicated mitral valve lesions is indicated.     

Use of a novel acellular xenograft as a patch for aortic annular enlargement during aortic valve replacement

A patient with a history of aortic valve endocarditis and surgical debridement presented with acute congestive heart failure because of severe aortic stenosis. During valve replacement surgery, an aortic annular enlargement was required to overcome a potential patient-prosthesis mismatch. We describe the use of a novel, bioresorbable, acellular xenograft for the enlargement patch. This material is expected to remodel into native patient tissue over time. This case offers an alternative implant for left heart reconstruction using a regenerative patch.