Leaflet Immobility Research Articles

Subclinical Leaflet Thrombosis in Supra-annular Transcatheter Aortic Valves: the Role of Leaflet Design.

Subclinical leaflet thrombosis has been increasingly observed in patients undergoing transcatheter aortic valve replacement. Intra-annular transcatheter aortic valves (TAVs) have a larger neo-sinus volume than supra-annular devices and are potentially at a higher risk of hypoattenuated leaflet thickening (HALT). However, clinical data from randomized clinical trials have shown that approximately one-third of patients undergoing TAVR with intra- or supra-annular devices develop HALT in 1year. The findings point to the potential role of leaflet design in developing HALT. The study aimed to systematically investigate leaflet kinematics of a supra-annular TAV, Medtronic CoreValve, and determine regions of blood stasis. Fluid-solid interaction simulations demonstrated the limited movement of CoreValve leaflets in the lower belly region that created regions of blood stasis on the surface of the leaflets. The findings provide insights into potential improvements in leaflet design in the next generation of TAVs to reduce the risk of HALT and leaflet immobility.

Six-Month Biological Response and Functionality of Balloon-Expandable Transcatheter Aortic Valve (Myval) in Aortic Banding Model

BackgroundLong-term evaluation of transcatheter heart valves (THV) in the pre-clinical setting and clinical translation of outcomes was limited.AimWe evaluate biocompatibility and durability of a balloon expandable THV system (Myval, Meril Lifesciences) at 6-month follow-up in the novel ovine aortic banding model.MethodsA surgical ascending aortic banding model was created in 11 sheep. Two weeks later, 11 Myval THV systems (20 and 23 mm) were introduced and implanted via carotid approach for a 6 month follow-up. Transthoracic echocardiography was performed at 30, 90, and 180 days. Subsequently, the animals were sacrificed and the valves with surrounding tissue harvested for pathological and radiographic evaluation.ResultsAll valves were implanted successfully. There were 2 procedure-related deaths. One sheep died prematurely on day 133 due to endocarditis and one on day 74 due to leaflet immobility caused by tight banding. Both these were not related to the device.At 6 months all valves that completed follow-up (n = 7) were functional, with no significant regurgitation, calcification, thrombi, or vegetation. At terminal follow-up mean pressure gradient was 21.9{plus minus}11 mm Hg, Vmax = 3.3{plus minus}1 m/s and ejection fraction of 53.3 {plus minus} 6%. In pathology, implant cusps were covered with endothelialized and fibrocellular neointima, whereas the conduits were fully integrated without inflammatory reaction. There were no signs of thrombus or calcifications.ConclusionsIn this novel aortic banding model, Myval THV showed optimal deployment and good hemodynamic performance at 6 months. There were no device related degenerations and healing was very advanced.

Leaflet immobility and thrombosis in transcatheter aortic valve replacement.

Transcatheter aortic valve replacement (TAVR) has grown exponentially worldwide in the last decade. Due to the higher bleeding risks associated with oral anticoagulation and in patients undergoing TAVR, antiplatelet therapy is currently considered first-line antithrombotic treatment after TAVR. Recent studies suggest that some patients can develop subclinical transcatheter heart valve (THV) thrombosis after the procedure, whereby thrombus forms on the leaflets that can be a precursor to leaflet dysfunction. Compared with echocardiography, multidetector computed tomography is more sensitive at detecting THV thrombosis. Transcatheter heart valve thrombosis can occur while on dual antiplatelet therapy with aspirin and thienopyridine but significantly less with anticoagulation. This review summarizes the incidence and diagnostic criteria for THV thrombosis and discusses the pathophysiological mechanisms that may lead to thrombus formation, its natural history, potential clinical implications and treatment for these patients.

Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility.

Artificial heart valves may dysfunction, leading to thrombus and/or pannus formations. Computational fluid dynamics is a promising tool for improved understanding of heart valve hemodynamics that quantify detailed flow velocities and turbulent stresses to complement Doppler measurements. This combined information can assist in choosing optimal prosthesis for individual patients, aiding in the development of improved valve designs, and illuminating subtle changes to help guide more timely early intervention of valve dysfunction. In this computational study, flow characteristics around a bileaflet mechanical heart valve were investigated. The study focused on the hemodynamic effects of leaflet immobility, specifically, where one leaflet does not fully open. Results showed that leaflet immobility increased the principal turbulent stresses (up to 400%), and increased forces and moments on both leaflets (up to 600% and 4000%, respectively). These unfavorable conditions elevate the risk of blood cell damage and platelet activation, which are known to cascade to more severe leaflet dysfunction. Leaflet immobility appeared to cause maximal velocity within the lateral orifices. This points to the possible importance of measuring maximal velocity at the lateral orifices by Doppler ultrasound (in addition to the central orifice, which is current practice) to determine accurate pressure gradients as markers of valve dysfunction.

Aortic Valve Bioprostheses: Leaflet Immobility and Valve Thrombosis.

Leaflet immobility and valve thrombosis have been reported with both transcatheter and surgical aortic valve bioprostheses. The relationships between these abnormalities and their incidence, time course, clinical significance, predisposing factors, optimal imaging modality, and current therapeutic options remain uncertain but are rapidly evolving. Four-dimensional computerized tomographic imaging has been determined to have the highest sensitivity in studies evaluating leaflet immobility and valve thrombosis. Echocardiography is also used during surveillance, but it appears to be less sensitive. The definitive diagnosis of valve thrombosis is based on a combination of diagnostic 4-dimensional computerized tomographic imaging findings, resolution of imaging abnormalities, and elevated transcatheter gradients with anticoagulation or surgical or pathological confirmation. Uncertainty about the incidence and clinical significance of the findings is the basis of 2 US Food and Drug Administration-approved studies comparing transcatheter and surgical aortic valve replacement with a subset undergoing surveillance 4-dimensional computerized tomographic imaging. Given the expansion of transcatheter aortic valve procedures, including potentially lower-risk patients, the resolution of these uncertainties is critical.

Subclinical bioprosthetic aortic valve thrombosis: clinical and translational implications.

A recently published study has alerted the cardiovascular community to the existence of a significant and previously unrecognized risk of subclinical valve thrombosis following implantation of surgical and catheter-based bioprosthetic valves. The purpose of this article is to review our current understanding of this new clinical entity and to identify unanswered questions and areas for future research. Subclinical bioprosthetic valve thrombosis (BPVT) is a more common phenomenon than previously appreciated. It appears that the incidence of BPVT is higher following transcatheter aortic valve replacement compared with surgical aortic valve replacement. Four-dimensional computed tomography (CT) is the most sensitive imaging modality for detection of leaflet immobility and subclinical BPVT. Certain echocardiographic findings, such as increasing transaortic gradients, increased cusp thickness and abnormal cusp mobility, predict the presence of BPVT on four-dimensional CT. There is a growing body of evidence linking subclinical BPVT with premature valvular hemodynamic deterioration and structural valve degeneration. Furthermore, subclinical leaflet thrombosis may constitute a nidus for unrecognized subacute cerebral or other thromboembolic events. Oral anticoagulation seems effective in both the prevention and treatment of BPVT. Subclinical valve thrombosis is an important and underappreciated cause of early bioprosthetic valve failure. Although several recent studies have improved our understanding of this newly recognized clinical entity, a number of questions remain unanswered. Further studies are warranted to elucidate the true incidence of subclinical BPVT, its clinical consequences, as well as the optimal antithrombotic regimen following bioprosthetic valve implantation. The subgroups of patients at highest risk of BPVT will need to be identified for risk stratification purposes. Several ongoing clinical trials will shed some light on these important issues.

Mechanism of valve failure and efficacy of reintervention through catheterization in patients with bioprosthetic valves in the pulmonary position.

Background:Surgical and transcatheter bioprosthetic valves (BPVs) in the pulmonary position in patients with congenital heart disease may ultimately fail and undergo transcatheter reintervention. Angiographic assessment of the mechanism of BPV failure has not been previously described.Aims:The aim of this study was to determine the mode of BPV failure (stenosis/regurgitation) requiring transcatheter reintervention and to describe the angiographic characteristics of the failed BPVs and report the types and efficacy of reinterventions.Materials and Methods:This is a retrospective single-center review of consecutive patients who previously underwent pulmonary BPV placement (surgical or transcatheter) and subsequently underwent percutaneous reintervention from 2005 to 2014.Results:Fifty-five patients with surgical (41) and transcutaneous pulmonary valve (TPV) (14) implantation of BPVs underwent 66 catheter reinterventions. The surgically implanted valves underwent fifty reinterventions for indications including 16 for stenosis, seven for regurgitation, and 27 for both, predominantly associated with leaflet immobility, calcification, and thickening. Among TPVs, pulmonary stenosis (PS) was the exclusive failure mode, mainly due to loss of stent integrity (10) and endocarditis (4). Following reintervention, there was a reduction of right ventricular outflow tract gradient from 43 ± 16 mmHg to 16 ± 10 mmHg (P < 0.001) and RVp/AO ratio from 0.8 ± 0.2 to 0.5 ± 0.2 (P < 0.001). Reintervention with TPV placement was performed in 45 (82%) patients (34 surgical, 11 transcatheter) with no significant postintervention regurgitation or paravalvular leak.Conclusion:Failing surgically implanted BPVs demonstrate leaflet calcification, thickness, and immobility leading to PS and/or regurgitation while the mechanism of TPV failure in the short- to mid-term is stenosis, mainly from loss of stent integrity. This can be effectively treated with a catheter-based approach, predominantly with the valve-in-valve technique.

Incidence, Predictors, and Mid-Term Outcomes of Possible Leaflet Thrombosis After TAVR

ObjectivesThis study sought to clarify the incidence and predictors of hypoattenuated leaflet thickening (HALT) and mid-term outcomes after transcatheter aortic valve replacement. BackgroundHALT detected on multidetector computed tomography (MDCT) scanning raised concerns about possible subclinical leaflet thrombosis. MethodsWe studied 70 of 100 consecutive patients from a single-center registry who underwent implantation with the Edwards SAPIEN-XT device. MDCT results, echocardiographic data, and laboratory findings obtained at the 6-month and 1-year follow-ups were analyzed. ResultsOf 70 patients, MDCT scans revealed HALT in 1 patient (1.4%) at discharge, 7 (10.0%) at 6 months, and 10 (14.3%) at 1 year post–transcatheter aortic valve replacement cumulatively. The degree of leaflet immobility correlated with the HALT area on 4-dimensional MDCT (r = 0.68) on the basis of data from 10 patients. HALT was associated with male sex (70% vs. 25%; p = 0.008) and larger sinus of Valsalva (31.0 ± 2.0 mm vs. 28.6 ± 2.6 mm; p = 0.005). HALT was found in 3 of 49 patients with a 23-mm bioprosthesis and in 7 of 21 patients with a 26-mm bioprosthesis (6.1% vs. 33.3%; p = 0.006). D-dimer levels were significantly increased in the HALT group at the 6-month (2.3 μg/ml [interquartile range (IQR): 2.1 to 6.1 μg/ml] vs. 1.1 μg/ml [IQR: 0.8 to 2.2 μg/ml]; p = 0.002) and 1-year (2.7 μg/ml [IQR: 1.7 to 4.8 μg/ml] vs. 1.2 μg/ml [IQR: 0.9 to 2.1 μg/ml]; p = 0.006) follow-ups, despite no differences at discharge. The pressure gradient was decreased in the HALT group at the 1-year follow-up (8.3 ± 0.8 mm Hg vs. 11.1 ± 4.9 mm Hg; p = 0.005). After detecting HALT, additional anticoagulation therapy was not administered. Clinical outcomes, including all-cause mortality (0% vs. 1.7%; p = 1.00) and stroke (0% vs. 0%; p = 1.00), were similar between the groups. ConclusionsHALT with reduced leaflet motion was not rare but usually subclinical. Valve hemodynamics and mid-term outcomes were uneventful even without additional anticoagulant therapy in our limited number of cases. Male sex, larger sinus and bioprosthesis size, and elevated D-dimer levels during follow-up were associated with this phenomenon.

Advancing a Guiding Catheter Across a Mechanical Aortic Valve.

Postoperative mitral paravalvular leaks (MPVLs) occur in approximately 5% of patients undergoing mitral valve replacement and are associated with substantial morbidity. Although surgical repair is the gold standard, it carries a significant risk of morbidity and death, which makes percutaneous closure guided by transesophageal echocardiography a viable and attractive approach in high-risk patients.1 Most case reports discuss an antegrade or transapical approach via an arteriovenous wire loop that serves as a monorail, in order to advance and deploy a closure device. A few case reports1–3 have described a retrograde approach in patients with normal aortic valves, wherein the proximal disc of the device is deployed into the left atrium via an arterial wire. This approach saves operative time and fluoroscopy time, and lowers the risk of sequelae by avoiding a transseptal puncture and an arteriovenous loop.3 The retrograde approach is usually better in patients with medial defects or with defects that create a large gradient across the leak.4The concern is that advancing a guiding catheter across a mono- or bileaflet mechanical aortic valve can cause temporary valve malfunction and hemodynamic compromise. There have been a few published reports4,5 of cases wherein a small guiding catheter was advanced across a mechanical aortic valve to facilitate the making of an arteriovenous loop by advancing the wire through the left ventricle and across the defect into the left atrium. The wire is then snared into the venous system.Until this issue of the Texas Heart Institute Journal, there has, to our knowledge, been no mention in the literature of deploying a closure device through a mechanical aortic valve solely by the retrograde technique. The authors of the case series6 report 2 such instances, in which MPVLs were closed in a retrograde fashion. They first tested the hemodynamic effect of crossing the mechanical aortic valve by using a 6F catheter, and then proceeded with deployment. They gave themselves a 5-minute limit in each attempt and encountered no sequelae of great consequence. Despite their success, we worry that this approach of passing a catheter through a mechanical valve is dangerous. The authors appear to agree, because they limit each attempt to 5 minutes. The worst potential sequela is valve damage and leaflet immobility that result in “wide-open” aortic regurgitation and catastrophic hemodynamic consequences.In patients with MPVL and a mechanical aortic valve, we should still attempt an antegrade technique first, because it remains safer, with better support during deployment of the closure device. This case report shows the retrograde approach to be a feasible option only when the other approaches have failed in such patients, or are not viable. The retrograde approach should be the last resort in an otherwise-inoperable patient. Further studies are needed to validate the optimal timing and technique.

Risk Stratification in Patients With Aortic Stenosis Using Novel Imaging Approaches.

The prevalence of calcific aortic stenosis increases with age, occurring in 3% to 5% of individuals aged >75 years.1,2 The narrowing of the aortic valve is driven by a highly complex and intricately regulated process of inflammation, fibrosis, and calcification, which eventually results in leaflet immobility and the associated hemodynamic consequences.3 In response to the narrowed valve, left ventricular hypertrophy is initially adaptive to restore wall stress and cardiac performance. Ultimately, adverse events, such as symptoms, heart failure, and death, occur as the left ventricle decompensates. This transition from adaptation to decompensation is driven by progressive myocyte death and myocardial fibrosis.4–6 Therefore, it is important to consider aortic stenosis as a condition that affects both the valve and the myocardium.5,6 Indeed, contemporary guidelines recommend aortic valve replacement in patients with severe aortic stenosis and evidence of advanced ventricular decompensation, defined by either the presence of symptoms or an impaired systolic ejection fraction <50%.7,8 The current strategy relies heavily on the timely identification of symptoms. However, the poor prognosis associated with the development of angina, exertional dyspnea, and syncope first described by Ross and Braunwald4 in 1968 was based on younger patients with bicuspid or rheumatic disease (average age of 63 years at the time of death). Establishing symptoms in the more elderly population encountered in current clinical practice is more challenging because of their comorbidities and often sedentary lifestyles. Moreover, it is now widely recognized that left ventricular ejection fraction is not a sensitive marker of myocardial dysfunction,9,10 and impairment in ejection fraction is often a late manifestation that may not be reversible.11,12 Furthermore, there is an urgent need to improve our understanding of the pathogenesis of aortic stenosis, both …

Imaging of pannus formation in patients with mechanical heart valves.

Patient-prosthesis mismatch (PPM) should be recognized in patients with elevated transprosthetic gradients but without leaflet immobility, since the treatment strategy may differ in either etiology. However, thrombus and/or pannus formation should be excluded before a diagnosis of PPM is made. Particularly, pannus formation may not be diagnosed with 2-dimensional transesophageal echocardiography. Electrocardiographically gated 64-section multidetector computed tomography (MDCT) may be a promising tool in diagnosing or excluding pannus formation. Our report underlines the utility of MDCT in this regard and also emphasizes the importance of recognition of PPM as a differential diagnosis in such patients.

Transapical Aortic Valve-in-Valve-in-Valve Implantation as a Procedural Rescue Option

Device malposition and dysfunction with resultant severe aortic insufficiency are known complications of transcatheter aortic valve implantation (TAVI). Fortunately, these complications can often be successfully treated with a transcatheter valve-in-valve (VinV) implantation. However, prosthetic leaflet dysfunction or immobility from the VinV configuration can lead to severe central aortic insufficiency. We report the first known case of implantation of a third SAPIEN prosthesis (Edwards Lifesciences, Irvine, CA) during TAVI as a valuable bailout strategy to deal with severe aortic insufficiency after VinV implantation.

Live 3D TEE Demonstrates and Guides the Management of Prosthetic Mitral Valve Obstruction

A 43-year-old woman, with a remote history of rheumatic mitral stenosis and a St. Jude prosthetic mitral valve replacement, presented with shortness of breath and palpitations, shortly after a long flight. On admission, atrial fibrillation with a rapid ventricular response was noted in the setting of a long history of noncompliance with her anticoagulation. Transesophageal echocardiography (TEE) demonstrated multiple laminated thrombi in the left atrial appendage. Live three-dimensional (3D) TEE confirmed this diagnosis and demonstrated an immobile posterior leaflet of the mitral prosthesis, which had direct implications in her management. She successfully underwent surgery for mitral valve replacement, left atrial appendage ligation, and a Maze procedure on the following day. The multiple thrombi within the atrial appendage were confirmed intraoperatively and pannus formation was determined to be the etiology of the leaflet immobility.

Feeling the Pressure? Anterior Mitral Leaflet Immobility in a Patient With Bicuspid Aortic Valve Disease

A 32-YEAR-OLD, 87-kg, 173-cm man with a past medical history of a congenital bicuspid aortic valve was admitted to the authors' hospital for evaluation of dyspnea on exertion. The patient had been a frequent participant in strenuous athletic activities including full-court basketball. He reported that his stamina during these activities had declined substantially in recent months. The patient also described unusual episodes of fatigue while performing his job as a biomedical engineer. He denied a history of angina pectoris, syncope, palpitations, orthopnea, paroxysmal nocturnal dyspnea, and peripheral edema. The physical examination was notable for a grade III of VI holodiastolic murmur heard best along the left sternal border. An Austin Flint murmur 1 Flint A. On cardiac murmurs. Am J Med Sci. 1862; 44: 29-54 Google Scholar was not appreciated. The remainder of the physical examination was noncontributory. Noninvasive measurements of arterial blood pressure indicated the presence of a widened pulse pressure (75-80 mmHg). A plasma brain natriuretic peptide concentration was normal. Transesophageal echocardiography (TEE) was performed as part of the evaluation and confirmed the presence of a bicuspid aortic valve with thickened anterior-lateral (left and right coronary cusp fusion; type A) 2 Russo C.F. Cannata A. Lanfranconi M. et al. Is aortic wall degeneration related to bicuspid aortic valve anatomy in patients with valvular disease?. J Thorac Cardiovasc Surg. 2008; 136: 937-942 Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar and posterior-medial leaflets of approximately equal size. The TEE examination also revealed that the middle scallop of the anterior mitral leaflet (A2) was essentially immobile throughout the cardiac cycle (Fig 1, Fig 2 and Video 1 [supplementary videos are available online]). What is the cause of this anterior mitral leaflet immobility? Fig 2The midesophageal long-axis view obtained during early diastole; the location and shape of the middle scallop of the anterior mitral leaflet (A2) are essentially unchanged compared with Figure 1. View Large Image Figure Viewer Download Hi-res image

Spectrum of Calcific Aortic Valve Disease

Received October 26, 2004; revision received January 13, 2005; accepted February 4, 2005. Calcific aortic valve disease is a slowly progressive disorder with a disease continuum that ranges from mild valve thickening without obstruction of blood flow, termed aortic sclerosis, to severe calcification with impaired leaflet motion, or aortic stenosis (Figure 1). In the past, this process was thought to be “degenerative” because of time-dependent wear-and-tear of the leaflets with passive calcium deposition. Now, there is compelling histopathologic and clinical data suggesting that calcific valve disease is an active disease process akin to atherosclerosis with lipoprotein deposition, chronic inflammation, and active leaflet calcification. The overlap in the clinical factors associated with calcific valve disease and atherosclerosis and the correlation between the severity of coronary artery and aortic valve calcification provide further support for a shared disease process. Figure 1. Gross specimen of minimally diseased aortic valve (left) and severely stenotic aortic valve (right). In the severely stenotic valve, there are prominent lipocalcific changes on aortic side of valve cusps (arrow), with sparing of commissures. ### Anatomy of Normal Aortic Valve The normal aortic valve comprises 3 layers. The ventricularis, on the ventricular side of the leaflet, is composed of elastin-rich fibers that are aligned in a radial direction, perpendicular to the leaflet margin. The fibrosa, on the aortic side of the leaflet, comprises primarily fibroblasts and collagen fibers arranged circumferentially, parallel to the leaflet margin. The spongiosa is a layer of loose connective tissue at the base of the leaflet, between the fibrosa and ventricularis, composed of fibroblasts, mesenchymal cells, and a mucopolysaccharide-rich matrix. These layers work in concert to provide tensile strength and pliability for decades of repetitive motion. ### Early Lesion of Aortic Sclerosis Histopathologic studies of aortic sclerosis show focal subendothelial plaquelike lesions on the aortic side of the leaflet that extend to the adjacent fibrosa layer. Similarities to …

Extrinsic obstruction of a carbomedics prosthesis in the mitral position: Echocardiographic and surgical findings

In this article a case of malfunction of a Carbomedics mitral prosthesis in a patient with mild symptoms is described. Although there was evidence by echocardiography of a thrombus in proximity to the prosthesis and leaflet immobility assumed to be caused by the thrombus, it was demonstrated, at the time of surgery, that the immobility of the prosthetic leaflet was due to a chorda tendineae stuck between the leaflet and the sewing ring. This is the first report of this occurring in a bileaflet prosthesis. It is likely that the restricted mobility of the leaflet had contributed to the thrombosis of the prosthesis.

Doppler echocardiographic evaluation of streptokinase lysis of thrombosed right-sided St. Jude Medical valves in patients with congenital heart defects

Four episodes of St. Jude Medical prosthesis leaflet thrombosis were serially evaluated by two-dimensional and Doppler echocardiography during treatment with streptokinase. Three patients aged 4, 11, and 24 years with congenital heart disease had St. Jude Medical valves in pulmonary positions (two cases) for tetralogy of Fallot and in the tricuspid position (one case). The duration of thrombosis was not known in any patient. Leaflet immobility and its resolution were demonstrated by echocardiography and were confirmed fluoroscopically. Continuous wave Doppler echocardiography showed abnormal stenotic gradients in thrombosed valves that were reduced after thrombolysis. These studies demonstrate the utility of two-dimensional and Doppler echocardiography in serial evaluation of prosthetic pulmonary and tricuspid valve thrombosis during thrombolysis.

The dysplastic pulmonary valve: echocardiographic features and results of balloon dilatation.

The feasibility of using balloon dilatation to relieve stenosis caused by dysplasia of the pulmonary valve was assessed in seven patients (five female, mean age two years) with angiographically confirmed dysplasia who were identified among 38 patients with pulmonary valve stenosis selected for balloon dilatation over a two year period. The clinical features in three patients were consistent with Noonan's syndrome. In all patients the gradient across the valve was assessed by cross sectional echocardiography and Doppler echocardiography before cardiac catheterisation. Balloon dilatation was performed by conventional techniques. In one patient, who had balloon dilatation in the operating room before surgical valvectomy, the diameter of the valve orifice increased from 3 mm to 10 mm. Inspection showed a tear along the anterior commissure. The mean (SD) pressure gradients between the right ventricle and pulmonary artery before and immediately after dilatation in five patients were not significantly different (58 (28) and 47 (12) mm Hg) respectively. There was no overall significant change in the degree of stenosis when four of these patients were examined by Doppler echocardiography six months after operation (44 (17) mm Hg), although one patient (case 5) did show a significant reduction in gradient. This patient had angiographic and echocardiographic features of dysplasia and commissural fusion. Several echographic features were common to all patients and distinguished them from cases of typical pulmonary valve stenosis. These were: pronounced thickening of leaflets; leaflet immobility in diastole and systole; no dilatation of the sinuses of Valsalva in diastole, and supra-annular narrowing. These poor results of balloon dilatation suggest that commissural fusion is not an important mechanism for causing stenosis in the dysplastic pulmonary valve. When dysplasia of the pulmonary valve is identified clinically and echocardiographically, balloon dilatation is unlikely to improve haemodynamic function; it should be attempted if commissural fusion is present.

Fate of Left-Sided Cardiac Bioprosthesis Valves in Children

To avoid anticoagulation and minimize thromboembolic phenomena, between 1975 and 1980 we used 18 porcine bioprosthetic valves (BPVs) to replace 11 aortic and seven mitral valves in 17 children ranging from 7 to 18 years of age (mean, 8.2 years). Ten BPVs (91%) in the aortic position had to be replaced one to six years (mean, 4.2 years) after insertion. Nine of these valves developed severe calcification with leaflet immobility and severe stenosis. The tenth valve became insufficient with a disrupted cusp. Six (86%) of seven BPVs inserted in the mitral position required replacement two to four years (mean, 3.1 years) after insertion. Massive mitral regurgitation developed in three, while in the other three mitral stenosis was prominent. All explanted BPVs exhibited calcification with disruption and loss of mobility of the leaflets. Hemodynamic deterioration often occurred catastrophically, with nine patients requiring emergency valve replacement. Elective valve replacement carried no hospital mortality, whereas emergency valve replacement carried a 33% mortality. The BPV failure rate of 94% within six years leads us to recommend against the use of biologic valves in the pediatric age group in the aortic or mitral position. Bioprosthetic valve failure may occur catastrophically and replacement should be carried out early to avoid the higher operative mortality associated with emergency surgery.

Complete and Intermediate Atrioventricular Canal in Infants Less than a Year Old: Observations of Anatomical and Pathological Variants in Left Ventricular Outflow Tract

In a study of 13 postmortem specimens from infants with intermediate and complete forms of persisting atrioventricular (AV) canal, potentially obstructive left ventricular outflow tract morphology was apparent in 6. Possible obstructive components included various causes of anterior mitral leaflet immobility, multiple short chordae, anterior malposition of papillary muscles, and septal hypertrophy. Left ventricular outflow tract obstruction can be exaggerated by corrective techniques that do not produce relief of these conditions.