Ventricular Outflow Tract Morphology Research Articles

Surgical and transcatheter pulmonary valve replacement in patients with repaired tetralogy of Fallot: cardiac magnetic resonance imaging characteristics and morphology of right ventricular outflow tract.

Pulmonary valve replacement is recommended in patients with repaired tetralogy of Fallot based on cardiac magnetic resonance imaging (MRI) criteria. This procedure is performed by surgical or transcatheter approaches. We aimed to investigate the differences in preprocedural MRI characteristics (volume, function, strain) and morphology of the right ventricular outflow tract and branch pulmonary arteries in patients for whom surgical or transcatheter pulmonary valve replacementwas planned. Cardiac MRI of 166 patients with tetralogy of Fallot were analyzed. Of these, 36 patients for whompulmonary valve replacement was plannedwere included. Magnetic resonance imaging characteristics, right ventricular outflow tract morphology, branch pulmonary artery flow distribution and diameter were compared between surgical and transcatheter groups. Spearman correlation and Kruskal-Wallis tests were performed. Circumferential and radial MRI strain for the right ventricle were lower in thesurgical group (P=0.045and P=0.046, respectively). The diameter of the left pulmonary artery was significantly lower (P=0.021) and branch pulmonary artery flow and diameter ratio were higher (P=0.044and P = 0.002, respectively) in the transcatheter group. There was a significant correlation between right ventricular outflow tract morphology and right ventricular end-diastolic volume indexand global circumferential and radial MRI strain (P=0.046, P=0.046and P= 0.049, respectively). Preprocedural MRI strain, right-to-left pulmonary artery flow, diameter ratio and morphological features of the right ventricular outflow tract were significantly different betweenthe two groups. A transcatheter approach may be recommended for patients with branch pulmonary artery stenosis, since both pulmonary valve replacement and branch pulmonary artery stenting can be performed in the same session.

The Effect of Pulmonary Root Translocation on the Left Ventricular Outflow Tract

We report the effect of pulmonary root translocation onthe left ventricular outflow tract. A double switch operation with pulmonary root translocation was performed in a 6-year-old boy whose diagnosis was dextrocardia, congenitally corrected transposition of the great arteries, ventricular septal defect, and pulmonary stenosis. Postoperative magnetic resonance imaging showed more natural left ventricular outflow than preoperatively (19 mm vs 22 mm in length between the top of the interventricular septum and the aortic valve). This technique does not require coronary transfer and enables preservation of the aortic root structure. The long-term results, including left ventricular outflow tract morphology, should be evaluated.

Fixed Subaortic Stenosis: A Clinical Dilemma for Clinicians and Patients

Subaortic stenosis carries considerable morbidity and mortality. In most cases, patients have an underlying left ventricular outflow tract morphology that promotes turbulence at the outflow tract, which induces the development of subaortic fibromuscular tissue. A subset of patients will progress to develop severe stenosis and aortic regurgitation, but it has been difficult to determine which patients are at risk. While resection of the subaortic tissue improves immediate outcome, many patients have recurrence of both stenosis and regurgitation, questioning the efficacy of surgical intervention in asymptomatic patients. This review article describes the current understanding of the etiology, treatment, and prognosis of subaortic stenosis.

Papillary Muscle Insertion Directly into the Anterior Mitral Leaflet in Hypertrophic Cardiomyopathy, Its Identification and Cause of Outflow Obstruction by Cardiac Magnetic Resonance Imaging, and Its Surgical Management

This case presents an uncommon but important mechanism of muscular left ventricular outflow obstruction in hypertrophic cardiomyopathy due to anomalous and direct papillary muscle insertion into the anterior mitral leaflet, a finding reliably identified clinically by cardiac magnetic resonance imaging. The identification of this left ventricular outflow tract morphology is important before invasive ventricular septal reduction therapy because it dictates a specific surgical strategy. These findings further support the role of cardiac magnetic resonance imaging in the early evaluation of hypertrophic cardiomyopathy patients.

Application of computational simulations for percutaneous pulmonary valve implantation: (Percutaneous pulmonary valve computer analysis)

Percutaneous pulmonary valve implantation is an innovative, successful alternative to open-heart surgery for the treatment of pulmonary valve dysfunction. However, this minimally-invasive procedure still presents some limitations: stent fracture and availability to a limited group of patients with very specific anatomy. Computational simulations, together with advanced cardiovascular imaging techniques can be used to help understand these limitations in order to improve the success of percutaneous pulmonary valve implantation and ultimately to broaden the range of patients suitable for this procedure. In this review, we show how three-dimensional image reconstruction of patients' right ventricular outflow tract, derived from magnetic resonance data, can be used to assess implantation site anatomy, and define a morphological classification to analyse the criteria for subject selection and to outline the design and mechanical requirements for the next generation of percutaneous pulmonary valve devices. We also show how the finite element method can be used to virtually model different stents (current stent and new possible stent designs) to evaluate their mechanical performance, risk of fracture, and optimise the design of the next generation device. Finite element inflation of these stents into selected right ventricular outflow tract models allowed for the evaluation of the in-situ anchoring and performance of the stents in each individual patient specific implantation site. The engineering methodologies reviewed – patient-specific three-dimensional imaging elaboration and finite element modelling – can be used to characterize right ventricular outflow tract morphology, outline the requirements for the next generation percutaneous pulmonary valve device and enable better selection of patients for this procedure, thus enhancing their safety. Such methodologies have the potential to aid and accelerate the design of future stents for percutaneous pulmonary valve implantation, so that a much larger patient population requiring pulmonary valve dysfunction treatment might benefit from this minimally-invasive intervention.

Minimally Invasive Options for Failing Homografts in the Pulmonary Position

Homograft implantation in the pulmonary position is usually part of initial repair in congenital heart defects with dysplasia or atresia of the pulmonary valve and at the time of the Ross operation. As part of reoperations, homografts are mainly required after nonvalved right ventricular outflow tract procedures. Due to an annual increase of homograft dysfunction, replacement is inevitable. Recently, percutaneous catheter-based valve implantations gain increasing acceptance. Even transventricular pulmonary valve implantation has been reported. Prior to decision making for any surgical or interventional therapy, the right ventricular outflow tract morphology together with additional pathologies need to be assessed. With the development of new prostheses and delivery modes, the demand for conventional surgery will further decrease.

Valved stents for transapical pulmonary valve replacement

Pulmonary valve insufficiency remains a leading cause for reoperations in congenital cardiac surgery. The current percutaneous approach is limited by the size of the access vessel and variable right ventricular outflow tract morphology. This study assesses the feasibility of transapical pulmonary valve replacement based on a new valved stent construction concept. A new valved stent design was implanted off-pump under continuous intracardiac echocardiographic and fluoroscopic guidance into the native right ventricular outflow tract in 8 pigs (48.5 +/- 6.0 kg) through the right ventricular apex, and device function was studied by using invasive and noninvasive measures. Procedural success was 100% at the first attempt. Procedural time was 75 +/- 15 minutes. All devices were delivered at the target site with good acute valve function. No valved stents dislodged. No animal had significant regurgitation or paravalvular leaking on intracardiac echocardiographic analysis. All animals had a competent tricuspid valve and no signs of right ventricular dysfunction. The planimetric valve orifice was 2.85 +/- 0.32 cm(2). No damage to the pulmonary artery or structural defect of the valved stents was found at necropsy. This study confirms the feasibility of direct access valve replacement through the transapical procedure for replacement of the pulmonary valve, as well as validity of the new valved stent design concept. The transapical procedure is targeting a broader patient pool, including the very young and the adult patient. The device design might not be restricted to failing conduits only and could allow for implantation in a larger patient population, including those with native right ventricular outflow tract configurations.

Variations in Right Ventricular Outflow Tract Morphology Following Repair of Congenital Heart Disease: Implications for Percutaneous Pulmonary Valve Implantation

Our aim was to identify sub-groups of right ventricular outflow tract morphology that would be suitable for percutaneous pulmonary valve implantation and to document their prevalence in our patient population. Eighty-three consecutive patients with right ventricular outflow tract dysfunction (5-41 years, 76% tetralogy of Fallot) referred to our center for cardiovascular magnetic resonance were studied. A morphological classification was created according to visual assessment of three-dimensional reconstructions and detailed measurement. Diagnosis, right ventricular outflow tract type, surgical history and treatment outcomes were documented. Right ventricular outflow tract morphology was heterogeneous; nevertheless, 5 patterns were visually identified. Type I, a pyramidal morphology, was most prevalent (49%) and related to the presence of a transannular patch. Other types (II-V) were seen more commonly in patients with conduits. Two patients had unclassifiable morphology. Ninety-five percent of patients were assigned to the correct morphological classification by visual assessment alone. Percutaneous pulmonary valve implantation was performed successfully in 10 patients with Type II-V morphology and in 1 patient with unclassifiable morphology. Percutaneous implantation was not performed in patients with Type I morphology. Only right ventricular outflow tract diameters < 22 mm in diameter were suitable for the current device. We have created a morphological classification of the RVOT in patients referred for assessment of RVOT dysfunction. Though only 13% of our patients underwent percutaneous implantation, > 50% of outflow tract morphologies may be suitable for this approach, in particular with the development of new devices appropriate for larger outflow.

Three-dimensional echocardiography: Historical development and current applications

Three-dimensional (3D) echocardiography facilitates spatial recognition of intracardiac structures, potentially enhancing diagnostic confidence of conventional echocardiography. The accuracy of 3D images has been validated in vitro and in vivo. In vitro, a detail 1.0 mm in dimension and 2 details separated by 1.0 mm can be identified from a volume-rendered 3D image. In vitro 3D volume measurements are underestimated by approximately 4.0 mL. In vivo, left ventricular volume measurements correlate highly with both cineventriculography (limits of agreement ±18 mL for end diastole and ±10 mL for end systole) and magnetic resonance imaging, including measurements for patients with functionally single ventricles. Studies on congenital heart lesions have shown good accuracy and good reproducibility of dynamic “surgical” reconstructions of septal defects, aortoseptal continuity, atrioventricular junction, and both left and right ventricular outflow tract morphology. Transthoracic 3D echocardiography was shown feasible in 81% to 96% of patients with congenital heart defects and provided additional information to that available from conventional echocardiography in 36% of patients, mainly in more detailed description of mitral valve morphology, aortoseptal continuity, and atrial septum. In patients with mitral valve insufficiency, 3D echocardiography was shown to be accurate in the quantification of the dynamic mechanism of mitral regurgitation and in the assessment of mitral commissures in patients with mitral stenosis. This includes not only valve tissue reconstruction but also color flow intracardiac jets. Three-dimensional reconstructions of the aortic valve were achieved in 77% of patients, with an accuracy of 90%. In conclusion, the role of 3D echocardiography, which continues to evolve, shows promise in the assessment of congenital and acquired heart disease. (J Am Soc Echocardiogr 2001;14:403-12.)

Elderly patients with hypertrophic cardiomyopathy: A subset with distinctive left ventricular morphology and progressive clinical course late in life

This report describes a subgroup of 52 elderly patients with obstructive hypertrophic cardiomyopathy in whom certain clinical and morphologic features differed importantly from those of many other patients with this disease. Ages ranged from 60 to 84 years (mean 69) and 45 [87%] were women.Echocardiographic examination showed a relatively small heart, having only modest ventricular septal hypertrophy associated with marked distortion of left ventricular outflow tract morphology. By virtue of selection, left ventricular outflow tract size at end-diastole was substantially reduced, and anterior displacement of the mitral valve within the left ventricular cavity was particularly marked. Sizable deposits of calcium in the region of the mitral anulus, posterior to the mitral valve, appeared to contribute to the outflow tract narrowing. Systolic anterior motion of the mitral valve was severe (with apposition of the mitral valve and ventricular septum) in 32 patients and more moderate in 20. The mechanism by which systolic contact between the mitral valve and septum occurred in most patients appeared to differ from that observed more typically in many other patients with hypertrophic cardiomyopathy; in most elderly study patients, anterior excursion of the mitral valve leaflets was relatively restricted, and systolic apposition between the mitral valve and septum resulted from a combination of anterior motion of the mitral valve and posterior excursion of the septum.The vast majority (50 of 52) of the patients remained asymptomatic (or only mildly symptomatic) for most of their lives and often did not develop severe and intractable symptoms until the 6th or 7th decade (ages 56 to 81 years; mean 66). Of the 49 patients with at least 1 year follow-up study, only 12 had improvement with pharmacologic therapy; however, 14 of the 18 patients who underwent ventricular septal myotomy-myectomy or mitral valve replacement obtained symptomatic benefit from operation.In conclusion, obstructive hypertrophic cardiomyopathy in many elderly (and predominantly female) patients may assume a distinctive morphologic appearance and a progressive clinical course. This subgroup of patients appears to constitute an important segment of the disease spectrum of hypertrophic cardiomyopathy of cardiac disease in the elderly that previously has not been precisely defined nor fully appreciated.

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.