Impact of Patient Prosthesis Mismatch on the Outcome of Transcatheter Pulmonic Valve Implantation

Patient prosthesis mismatch (PPM) is an important factor of the outcome in transcatheter aortic valve implantation. However, the impact of PPM in transcatheter pulmonic valve implantation (TPVI) has not been studied. Based on the narrowest valve stent diameters in two views of fluoroscopy, internal geometric orifice area (GOA) of the valve stent was calculated and indexed by body surface area (BSA), deriving iGOA. To define PPM in TPVI, receiver operating characteristics (ROC) curve analysis for iGOA for predicting significant residual right ventricular outflow tract (RVOT) gradient was used to derive the optimal cut-off value of iGOA. Our cohort were divided into 2 groups: PPM versus non-PPM. The clinical data were compared between 2 groups. TPVI was performed using Melody valve in 101 patients. Significant RVOT residual pressure gradient (≥ 15 mmHg) was observed in 31 patients (39.6%). Over a mean follow up periods of 6.9 ± 2.7 years, 22 patients (21.8%) required repeat interventions (16 transcatheter, 11 surgical, and both in 5 patients). Based on the ROC analysis, the best cut-off value of iGOA was 1.25 cm²/m² (area under the curve 0.873, p < 0.001) to define PPM. PPM was present in 42 patients (42%). On the Kaplan-Meier survival analysis, PPM was associated with the need of repeat intervention (p = 0.02). In conclusion, in TPVI, PPM was a strong predictor for the need of re-intervention. Considering PPM, target diameter of valve stent would depend on the patient body size and should be taken into account for optimal outcome of TPVI.

On the shape and structure of the murine pulmonary heart valve

Murine animal models are an established standard in translational research and provides a potential platform for studying heart valve disease. To date, studies on heart valve disease using murine models have been hindered by a lack of appropriate methodologies due to their small scale. In the present study, we developed a multi-scale, imaging-based approach to extract the functional structure and geometry for the murine heart valve. We chose the pulmonary valve (PV) to study, due to its importance in congenital heart valve disease. Excised pulmonary outflow tracts from eleven 1-year old C57BL/6J mice were fixed at 10, 20, and 30 mmHg to simulate physiological loading. Micro-computed tomography was used to reconstruct the 3D organ-level PV geometry, which was then spatially correlated with serial en-face scanning electron microscopy imaging to quantify local collagen fiber distributions. From the acquired volume renderings, we obtained the geometric descriptors of the murine PV under increasing transvalvular pressures, which demonstrated remarkable consistency. Results to date suggest that the preferred collagen orientation was predominantly in the circumferential direction, as in larger mammalian valves. The present study represents a first step in establishing organ-level murine models for the study of heart valve disease.

Age-Dependent Changes in Geometry, Tissue Composition and Mechanical Properties of Fetal to Adult Cryopreserved Human Heart Valves

There is limited information about age-specific structural and functional properties of human heart valves, while this information is key to the development and evaluation of living valve replacements for pediatric and adolescent patients. Here, we present an extended data set of structure-function properties of cryopreserved human pulmonary and aortic heart valves, providing age-specific information for living valve replacements. Tissue composition, morphology, mechanical properties, and maturation of leaflets from 16 pairs of structurally unaffected aortic and pulmonary valves of human donors (fetal-53 years) were analyzed. Interestingly, no major differences were observed between the aortic and pulmonary valves. Valve annulus and leaflet dimensions increase throughout life. The typical three-layered leaflet structure is present before birth, but becomes more distinct with age. After birth, cell numbers decrease rapidly, while remaining cells obtain a quiescent phenotype and reside in the ventricularis and spongiosa. With age and maturation-but more pronounced in aortic valves-the matrix shows an increasing amount of collagen and collagen cross-links and a reduction in glycosaminoglycans. These matrix changes correlate with increasing leaflet stiffness with age. Our data provide a new and comprehensive overview of the changes of structure-function properties of fetal to adult human semilunar heart valves that can be used to evaluate and optimize future therapies, such as tissue engineering of heart valves. Changing hemodynamic conditions with age can explain initial changes in matrix composition and consequent mechanical properties, but cannot explain the ongoing changes in valve dimensions and matrix composition at older age.

In vivo monitoring of function of autologous engineered pulmonary valve

OBJECTIVES

Clinical translation of tissue-engineered heart valves requires valve competency and lack of stenosis in the short and long term. Early studies of engineered valves showed promise, although lacked complete definition of valve function. Building on prior experiments, we sought to define the in vivo changes in structure and function of autologous engineered pulmonary valved conduits.

METHODS

Mesenchymal stem cells were isolated from neonatal sheep bone marrow and seeded onto a bioresorbable scaffold. After 4 weeks of culture, valved conduits were implanted. Valve function, cusp, and conduit dimensions were evaluated at implantation (echocardiography), at the experimental midpoint (magnetic resonance imaging), and at explant, at 1 day, and 1, 6, 12, or 20 weeks postoperatively (direct measurement, echocardiography). Histologic evaluation was performed.

RESULTS

Nineteen animals underwent autologous tissue-engineered valved conduit replacement. At implantation, valved conduit function was excellent; maximum transvalvular pressure gradient by Doppler echocardiography was 17 mm Hg; most valved conduits showed trivial pulmonary regurgitation. At 6 postoperative weeks, valve cusps appeared less mobile; pulmonary regurgitation was mild to moderate. At 12 weeks or more, valved conduit cusps were increasingly attenuated and regurgitant. Valved conduit diameter remained unchanged over 20 weeks. Dimensional measurements by magnetic resonance imaging correlated with direct measurement at explant.

CONCLUSIONS

We demonstrate autologous engineered tissue valved conduits that function well at implantation, with subsequent monitoring of dimensions and function in real time by magnetic resonance imaging. In vivo valves undergo structural and functional remodeling without stenosis, but with worsening pulmonary regurgitation after 6 weeks. Insights into mechanisms of in vivo remodeling are valuable for future iterations of engineered heart valves.

Geometric models of the aortic and pulmonary roots: suggestions for the Ross procedure

OBJECTIVE

To discuss geometric factors, which may influence long-term results relating to homograft competence following the Ross procedure, we describe the 3D morphology of the pulmonary and aortic roots.

MATERIALS

Measurements were made on 25 human aortic and pulmonary roots. Inter-commissural distances and the heights of the sinuses were measured. For geometrical reconstruction the three commissures and their vertical projections at the root base were used as reference points.

RESULTS

In the pulmonary root, the three inter-commissural distances were of similar dimensions (17.9+/-1.6mm, 17.5+/-1.4mm and 18.6+/-1.5mm). In the aortic root, the right inter-commissural distance was greatest (18.8+/-1.9mm), followed by the non-coronary (17.4+/-2.0mm) and left coronary sinus commissures (15.2+/-1.9mm). The mean height of the left pulmonary sinus was greatest (20+/-1.7mm) followed by the anterior (17.5+/-1.4mm) and right pulmonary sinus (18+/-1.66mm). In the aortic root, the height of the right coronary sinus was the greatest (19.4+/-1.9mm) followed by the heights of the non-coronary (17.7+/-1.8mm) and left coronary sinus (17.4+/-1.4mm). Measured differences between parameters determine the tilt angle and direction of the root vector. The tilt angle in the pulmonary root averaged 16.26 degrees , respectively; for the aortic roots, it was 5.47 degrees .

CONCLUSIONS

Herein we suggest that the left pulmonary sinus is best implanted in the position of the right coronary sinus, the anterior pulmonary in the position of the non-coronary sinus and the right pulmonary sinus in the position of the left coronary sinus. In this way, the direction of the pulmonary root vector will be parallel to that of the aortic root vector.

Construction of Tissue-Engineered Homograft Bioprosthetic Heart Valves In Vitro

Human mesenchymal stem cells (MSCs) differentiate into multiple cell-lineages and may serve as an alternative source of seed cells for tissue engineering. We investigated whether MSCs could be induced to differentiate into endothelial cells (ECs) and function as seed cells for the in vitro construction of tissue-engineered heart valves (TEHVs). Aortic or pulmonary valve homografts were decellularized with 0.1% sodium dodecylsulphate and used as scaffolds for TEHVs. The MSCs were isolated from human bone marrow by Percoll gradient centrifugation (1.073 g/ml), differentiated into ECs with vascular endothelial growth factor (10 ng/ml), and seeded onto a decellularized scaffold (high-density seeding, >10(5) cells/cm2) and grown in static culture for 14 days. Over 90% of the differentiated cells from MSCs stained positively for von Willebrand factor and Tie-2-related antigen. Additionally, Weibel-Palade corpuscle was observed in the cytoplasm of these cells. Levels of reendothelialization in static culture on days 7, 14, and 20, were 73%, 85%, and 95%, respectively. These results show that MSCs from human bone marrow can differentiate, in vitro, into ECs that can then be used to construct TEHVs. Reendothelialization in static culture can be used to provide the basic material for pulsatile-flow cultivation.

The Ross Procedure: New Insights Into the Surgical Anatomy

BACKGROUND

The precise knowledge of regional anatomical details is of utmost importance specially in complex procedures such as the Ross operation. This anatomical study offers a critical approach regarding the advantages, limits, and precautions for this procedure.

METHODS

Using dissection techniques, magnifications up to x6 and nontraditional approaches, 68 fixed normal heart specimens were studied over a 2-year period. The details of surgical relevance such as the boundaries and relations of the pulmonary and aortic roots, their vascularization, and the number and distribution of the septal arteries are described.

RESULTS

The aortic and pulmonary roots include interdependent elements functioning in a coordinated manner and establishing important relations with adjacent structures. Both coronary arteries vascularize the arterial roots. The infundibular branches from the right coronary artery are larger and more constant. The septal arteries establish important relations with the pulmonary infundibulum but their contribution to its vascularization is negligible. In this series, the main septal artery was the second, showing the longest retroinfundibular course. However, no constant relation was found between this vessel and the intraventricular landmarks.

CONCLUSIONS

A novel approach was used by performing nontraditional dissections of the arterial roots and by studying their vascularization The depicted details are useful to the surgeon specializing in the Ross procedure and represent the basis for further research.

Optimal Size of a Monocusp Patch for Reconstruction of a Hypoplastic Pulmonary Root: An Experimental Study in Pigs

BACKGROUND

Transannular patching is often performed to relieve congenital pulmonary stenosis, especially in tetralogy of Fallot. Theoretically, a monocusp patch can reduce patch-related pulmonary regurgitation, but the optimal size relation between the implant and the native hypoplastic pulmonary root is not well defined.

METHODS

In 11 pigs, peak pressure gradient and regurgitation fraction across the pulmonary root were measured. During cardiopulmonary bypass, two cusps including the pulmonary artery wall were resected and the midpoint of the free margin of the remaining cusp was sutured to the sinus wall to imitate a hypoplastic pulmonary root. Transannular patching was performed using a noncoronary segment of a porcine aortic root. After discontinuation of cardiopulmonary bypass, all measurements were repeated. Thereafter, the cusp of the patch was resected, and all measurements again repeated. Anatomic dimensions were determined after the pigs had been sacrificed.

RESULTS

Regurgitation fraction increased from 0.2% +/- 3.4% at baseline to 15.5% +/- 6.2% after reconstruction with a monocusp patch and to 60.0 +/- 18.6% after the cusp of the monocusp patch had been resected (p < 0.001). The median peak pressure gradient increased from 0 to 1 to 6 mm Hg (p = 0.013), respectively. The regurgitation fraction negatively correlated with the ratio of the length of the monocusp patch to that of the hypoplastic pulmonary root (r = -0.63, p = 0.037).

CONCLUSIONS

A monocusp patch for reconstruction of a hypoplastic pulmonary root results in significantly less regurgitation than a nonvalved patch of the same size, while the peak pressure gradient remains normal. The lowest regurgitation fraction was observed with a monocusp patch two-times the length of the circumference of the hypoplastic pulmonary root.

Geometrical model of the pulmonary root

BACKGROUND AND AIM OF THE STUDY

The renaissance of the Ross procedure has attracted much attention to the clinical anatomy of the pulmonary valve. Within the reviewed literature which emphasizes the morphology of the pulmonary root, no detailed anatomy has been reported. The study aim was to describe the cardiosurgical-orientated anatomy of the pulmonary valve.

METHODS

Morphometric measurements were made on 20 fixed normal pulmonary roots. The roots were fixed under diastolic pressure (5 mmHg) with closed leaflets. The distances between the commissures, and between the intervalvular triangles, were measured. The heights of the sinuses and of the intervalvular triangles were also defined.

RESULTS

The mean (+/- SD) of each parameter was calculated. The distances of the right, left and anterior sinus commissures were approximately similar, as were the distances of the intervalvular triangles at the root base. The mean height of the left coronary sinus was maximal, followed by the right and anterior pulmonary sinuses. The left intervalvular triangle was highest, followed by the posterior and right intervalvular triangles. The difference between the height of the left sinus and right intervalvular triangle indicated a tilt angle of 16.26 degrees between the root base and sinotubular junction.

CONCLUSION

Based on these measured parameters, a spatial geometrical model was constructed which clearly described the asymmetrical structure of the pulmonary root.

Echocardiographic features of the morphologically right ventriculo-arterial junction

In the normal heart, the morphologically right ventricle supports the pulmonary trunk. The key to echocardiographic evaluation of the junction between these structures is to understand not only the arrangement of the pulmonary valve, but also the complete muscular infundibulum that supports the valvar leaflets, lifting the valvar complex away from the base of the ventricular mass. As explained in the previous review,1 it is the presence of this free-standing muscular infundibular sleeve that makes it possible for the surgeon to remove the pulmonary valve for use as an allograft in the Ross procedure.2 In this review, we will address the echocardiographic features of the junction, considering primarily the situation in which the morphologically right ventricle supports the pulmonary trunk, but making comparisons with the abnormal arrangements in which either the aorta, or both arterial trunks, arise from the right ventricle. As we will see, the basic arrangement of the free-standing complete muscular infundibulum, or conus, is preserved with these abnormal arrangements, but there can be variation depending on the precise arrangement of the inner heart curvature, or ventriculo-infundibular fold, and the morphology can be further changed depending on the relationship of the arterial trunks themselves. The key to analysis, therefore, and also to accurate description, is to analyse separately the way in which the arterial trunks are joined to the ventricular mass, the relationships of the trunks one to the other, and the precise structure of the supporting right ventricular outflow tract, or outflow tracts in the setting of double outlet connection. If each of these features is then described in its own right, avoiding the temptation to make inferences regarding one feature from knowledge of another, then it is possible to avoid many of the persisting controversies relating to nomenclature.

Normal and abnormal structure of the ventriculo-arterial junctions

The normal heart possesses two ventriculo-arterial junctions – one for the aortic valve, and the other for the pulmonary valve. In the normal heart, these pulmonary and aortic roots are discrete and separate structures, the subpulmonary infundibulum being a free-standing muscular sleeve, separated by extracardiac space from the outflow tract of the left ventricle. When considering the congenital malformations that can distort these outflow tracts, it is conventional to categorise them as existing at subvalvar, valvar, and supravalvar levels. Such an approach, however, ignores the fact the valvar leaflets themselves extend through a significant length of the outflow tracts, with so-called supravalvar stenosis almost always involving the sinutubular junction, this being an integral part of the mechanism that normally ensures competent valvar closure. When considering the lesions that involve abnormally structured outflow tracts, these are best analysed by recognising the different features of the ventriculo-arterial junctions, namely the way the arterial trunks are joined to their underlying ventricles, the interrelationships of the trunks one to the other, and the arrangement of the supporting ventricular structures. In this review, we will show how knowledge of the arrangement of the normal junctions provides the necessary scaffold for logical analysis of all the lesions that can afflict the outflow tracts, be they otherwise normally or abnormally structured.

Comparison of biomechanical and structural properties between human aortic and pulmonary valve*1

OBJECTIVE

Pulmonary valve autografts have been reported as clinically effective for replacement of diseased aortic valve (Ross procedure). Published data about pulmonary valve mechanical and structural suitability as a long-term substitute for aortic valve are limited. The aim of this study was to compare aortic and pulmonary valve properties.

METHODS

Experimental studies of biomechanical properties and structure of aortic and pulmonary valves were carried out on pathologically unchanged human heart valves, collected from 11 cadaveric hearts. Biomechanical properties of 84 specimens (all valve elements: cusps, fibrous ring, commissures, sinotubular junction, sinuses) were investigated using uniaxial tensile tests. Ultrastructure was studied using transmission and scanning electron microscopy.

RESULTS

Ultimate stress in circumferential direction for pulmonary valve cusps is higher than for aortic valve (2.78+/-1.05 and 1.74+/-0.29 MPa, respectively). Ultimate stress in radial direction for pulmonary and aortic cusps is practically the same (0.29+/-0.06 and 0.32+/-0.04 MPa, respectively). In ultrastructural study, different layout and density in each construction element are determined. The aortic and pulmonary valves have common ultrastructural properties.

CONCLUSIONS

Mechanical differences between aortic and pulmonary valve are minimal. Ultrastructural studies show that the aortic and pulmonary valves have similar structural elements and architecture. This investigation suggests that the pulmonary valve can be considered mechanically and structurally suitable for use as an aortic valve replacement.

Intrapericardial echocardiography: a novel catheter-based approach to cardiac imaging

BACKGROUND

Transvascular catheter-based intracardiac echocardiography has been successfully used to help guide catheter ablation and electrophysiologic procedures. It has recently been demonstrated that catheters can be safely placed into the pericardial space to allow for epicardial cardiac mapping and ablation. We evaluated the feasibility of catheter-based intrapericardial echocardiography (IPE) during such procedures to identify cardiac structures and visualize intracardiac catheters.

METHODS

IPE was performed in 7 goats by placing a phased-array ultrasound transducer contained within a 10F steerable catheter into the pericardial space using the same transthoracic subxyphoid approach as used to map and ablate epicardial ventricular tachycardia. Images were obtained of cardiac structures and of intracardiac ablation catheters. After the procedure, the hearts were harvested to assess for possible IPE-related lesions.

RESULTS

The IPE catheter could be easily placed inside the pericardial space in all animals. In 7 of 7 cases, longitudinal and short-axis views of right- and left-sided chambers and valves were obtained, similar in orientation to transesophageal echocardiography. Visualization of atrial appendages (6/7), pulmonary veins (6/7), coronary arteries (6/7), and coronary sinus (3/6) was also feasible. Assessment of intracardiac transvalvar and venous blood flow was achieved by spectral and color Doppler. The ablation catheter could be clearly visualized inside cardiac chambers. No arrhythmias were induced with IPE catheter manipulation. After harvesting the hearts, no lesions resulting from the procedure were observed.

CONCLUSION

In this experimental setting, IPE was able to provide detailed images of cardiac structures and establish the relative position of the ablation catheter.

Quantification of pulmonary autograft characteristics using magnetic resonance imaging

BACKGROUND AND AIM OF THE STUDY

The diameters and distensibility of the native pulmonary root and their effect on pulmonary autograft performance were examined pre- and postoperatively using cardiac ultrasound and magnetic resonance imaging (MRI).

METHODS

Eight patients undergoing the Ross procedure were prospectively involved. The diameters of the native aortic, native pulmonary and autograft roots were measured at the level of the annulus, sinus, sinotubular junction and in the main root using MRI through the cardiac cycle. Ultrasound was also used to estimate the degree of regurgitation, both pre- and postoperatively.

RESULTS

The pulmonary root implanted into the systemic circulation increased in size but decreased in distensibility significantly at the sinus, sinotubular junction and main root, but not at the annulus. Postoperatively, the pulmonary autograft annulus showed a similar size and distensibility to that of the native aortic annulus. A wide range of aortic annular sizes (22-30 mm) produced clinically competent valves postoperatively. All undersized pulmonary valves showed only trivial regurgitation postoperatively. Although there was no clear correlation between root shape and valve insufficiency, two patients with mild and moderate autograft regurgitation both had divergent pulmonary roots (diameter at sinotubular junction > annulus diameter) preoperatively.

CONCLUSION

The pulmonary autograft using the root replacement technique functioned well in all but one case. The shape of the native pulmonary root may be a determinant of early autograft regurgitation, as well as the diameter and the size mismatch between the great arteries.

The conus valves of the adult gilthead seabream (Sparus auratus)

The conus (bulbo-ventricular) valves of teleosts perform a key function in the control of blood backflow during ventricular diastole. However, the structural characteristics of these valves are almost unknown. This paper presents a systematic anatomical, histological and structural study of the conus valves of the adult gilthead seabream (Sparus auratus). S. auratus shows two major left and right valves consisting of the leaflet and the supporting sinus. Each valvar leaflet can be divided into a stout proximal body and a flap-like distal region. The proximal body is structured into three layers: a luminal fibrosa, a dense cellular core and a parietal fibrosa. The luminal fibrosa is a collagenous structure extending the entire length of the leaflet, while the parietal fibrosa is restricted to the most proximal area. The dense cellular core consists of fibroblastic cells and a matrix rich in glycoconjugates, collagen and elastin. The histochemical and structural data suggest that the luminal fibrosa bears most of the force associated with valvar closure, while the cellular core acts as a cushion dampening vibrations and absorbing the elastic recoil. The sinus wall is a fibrous layer which shows proximal-distal differences in thickness. It also shows compositional differences that can be related to mechanical function. We describe the presence of a fibrous cylinder formed by the sinus wall, the fibrous interleaflet triangles and the fibrous layer that covers the inner surface of the conus myocardium. This fibrous cylinder constitutes the structural nexus between the ventricle, the conus and the bulbus arteriosus, provides support for the conus valves and separates the valvar complex from the surrounding tissues. The structure of the conus valves in S. auratus is different from that found in other vertebrates. Anatomical similarities between the conus valves and the mammalian arterial valves are emphasized. Each phyletic group appears to have developed specific structures in order to perform similar functions.

Visualization of the pulmonary valve using cine MR imaging

PURPOSE

To evaluate the capability of bright-blood cine MR to directly visualize the leaflets of the valve replacement in pulmonary position following Ross operation.

MATERIAL AND METHODS

Long and short axis views of the pulmonary valve were obtained in 10 normal subjects and 14 patients after Ross operation. Valve morphology and function were analyzed and signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated. Flow measurements were performed in the pulmonary trunk to assess pulmonary regurgitation.

RESULTS

In all subjects, tricuspid morphology of the pulmonary valve was visualized. SNR of the leaflets in normal subjects (9.8 +/- 3.0) and in patients after Ross operation (7.5 +/- 2.2) differed significantly from blood (12.6 +/- 3.2 and 11.3 +/- 2.5, respectively, p < 0.05). Valvular regurgitation was seen in 5 patients as an insufficient closure of the valve which was confirmed by flow measurements.

CONCLUSION

Cine MR enables in-plane visualization of the pulmonary valve and allows for functional and morphological evaluation in patients after pulmonary valve surgery.

Construction of autologous human heart valves based on an acellular allograft matrix

OBJECTIVE

Tissue engineered heart valves based on polymeric or xenogeneic matrices have several disadvantages, such as instability of biodegradable polymeric scaffolds, unknown transfer of animal related infectious diseases, and xenogeneic rejection patterns. To overcome these limitations we developed tissue engineered heart valves based on human matrices reseeded with autologous cells.

METHODS AND RESULTS

Aortic (n=5) and pulmonary (n=6) human allografts were harvested from cadavers (6.2+/-3.1 hours after death) under sterile conditions. Homografts stored in Earle's Medium 199 enriched with 100 IU/mL Penicillin-Streptomycin for 2 to 28 days (mean 7.3+/-10.2 days) showed partially preserved cellular viability (MTT assay) and morphological integrity of the extracellular matrix (H-E staining). For decellularization, valves were treated with Trypsin/EDTA resulting in cell-free scaffolds (DNA-assay) with preserved extracellular matrix (confocal microscopy). Primary human venous endothelial cells (HEC) were cultivated and labeled with carboxy-fluorescein diacetate-succinimidyl ester in vitro. After recellularization under fluid conditions, EC were detected on the luminal surfaces of the matrix. They appeared as a monolayer of positively labeled cells for PECAM-1, VE-cadherin and Flk-1. Reseeded EC on the acellular allograft scaffold exhibited high metabolic activity (MTT assay).

CONCLUSIONS

Earle's Medium 199 enriched with low concentration of antibiotics represents an excellent medium for long time preservation of extracellular matrix. After complete acellularization with Trypsin/EDTA, recellularization under shear stress conditions of the allogeneic scaffold results in the formation of a viable confluent HEC monolayer. These results represent a promising step toward the construction of autologous heart valves based on acellular human allograft matrix.

Cartilage in pulmonary valves of Syrian hamsters

The presence of cartilage in the pulmonary valve has been reported in birds, but not in mammals. We describe here the occurrence of cartilaginous tissue in the pulmonary valves of 40 (11.4%) of 351 Syrian hamsters examined using histological, histochemical and/or immunohistochemical techniques. The cartilaginous deposits were located along the fibrous attachments of the valve leaflets to the wall of the pulmonary artery trunk. Our findings indicate that the proximal attachments of the leaflets to their respective sinuses, and especially that of the ventral leaflet, are the most prone valvular regions to develop cartilaginous foci. Nonetheless, the possible function of these foci remains an open question. Formation of cartilage in the pulmonary valve starts within the first month of life, that is during the period in which the valve reaches histological maturation. The earliest evidence of chondrogenesis is the presence of small groups of cells embedded in a type II collagen-positive extracellular matrix. These groups of cells, which can appear as early as one day after birth, increase moderately in size and differentiate into hyaline cartilaginous tissue. The precursors of the cartilaginous cells are presumed to be neural crest-derived elements. However, the factor or factors involved in the differentiation of these precursors into chondrocytes are still unknown. In this regard, our observations cast doubt on the hypothesis that the formation of cardiac cartilages is primarily due to locally intense mechanical stimulation.

Morphometric study of the pulmonary trunk: implications for a new approach of the Ross procedure

A pulmonary valve autograft may be proposed to replace diseased aortic valves. The explanted pulmonary valve is replaced with a pulmonary homograft with the inherent risk of calcified degeneration. A monocusp valve using the anterior pulmonary trunk has been proposed to reconstruct the right ventricular outflow tract. The aim of this study was to determine the feasibility of this technique. In hearts from 17 adult cadavers, we measured: pulmonary trunk diameter at the leaflet tops (D1). H1 and H2 were respectively from leaflet top to lower and upper levels of the pulmonary trunk bifurcation. D2 = 1.4 D1 was calculated as the monocusp size allowing a 45 degrees opening of the valve and thus permitting good valvular efficacy. G = H1 - D2 determined the feasibility of the technique: G greater than 10 mm, appeared the most favorable, G between 0 and 10 mm, appeared possible, and G less than 0, appeared to be impossible. Mean values of D1, H1 and H2 were respectively: 20.19 mm, 37 mm and 57 mm. The technique was possible in 16 cases (94%) and impossible in 1 case (6%). Preoperative determination of these parameters, by echocardiography or magnetic resonance imaging, appears necessary before applying this new surgical technique.

Body surface area as a predictor of aortic and pulmonary valve diameter

BACKGROUND

Predicting cardiac valve size from noncardiac anatomic measurements would benefit pediatric cardiologists, adult cardiologists, and cardiac surgeons in a number of decision-making situations. Previous studies correlating valve size with body size have been generated with the use of fixed autopsy specimens, angiography, and echocardiography, but primarily in the young. This study examines the relation of body surface area to measurements of the left ventricular-aortic junction (aortic valve anulus diameter) and the right ventricular-pulmonary trunk junction (pulmonary valve anulus diameter) in 6801 hearts across a wide spectrum of ages.

METHODS

From June 1985 to October 1998, cardiac valves from 6801 donated hearts were analyzed morphologically. Donor age was newborn to 59 years (mean 31 +/- 17 years; median 32 years). Calculated body surface areas ranged from 0.18 to 3.55 m(2). Aortic (n = 4636) and pulmonary valve diameters (n = 5480) were measured from enucleated valves suitable for allograft transplantation. Mean valve sizes were computed for ranges in body surface area in 0.1-m(2) increments.

RESULTS

For adult men (age >/= 17 years), the mean aortic valve diameter was 23.1 +/- 2.0 mm (n = 2214) and the mean pulmonary valve diameter was 26.2 +/- 2.3 mm (n = 2589). For adult women, the mean aortic valve diameter was 21.0 +/- 1.8 mm (n = 1156) and the mean pulmonary valve diameter was 23.9 +/- 2.2 mm (n = 1408). The mean indexed aortic valve area was 2.02 +/- 0.52 cm(2)/m(2) and the pulmonary valve area 2.65 +/- 0.52 cm(2)/m(2). Between 82% and 85% of the variability was explained by the size of the patient. Regression equations were developed both overall and separately for men and women, although the additional contribution of sex above that of body size was less than 1%.

CONCLUSIONS

Aortic and pulmonary valve diameters are closely related to body size. Thus, body surface area, when used in conjunction with other clinically accepted evaluations, is a useful tool for estimating normal aortic and pulmonary valve size.

Anatomy of the muscular subpulmonary infundibulum with regard to the Ross procedure

BACKGROUND

To clarify the precise anatomical relationship of the muscular subpulmonary infundibulum.

METHODS

Eleven hearts were dissected, and microscopic sections taken through the arterial trunks of a 37-week-old fetus and of a neonate. The anatomy was also investigated during operative Ross procedures.

RESULTS

The sinotubular junctions of the pulmonary and aortic roots cross obliquely. The leaflets of the pulmonary valve are lifted away from the ventricular septum by the free-standing subpulmonary infundibulum, whereas the aortic valve is deeply wedged between the atrioventricular junctions. The muscular infundibulum spirals around the aortic root, being longest below the right-facing aortic sinus and shortest below the left. The first septal perforating artery pierces the septum below the shortest part of the infundibulum, sometimes within a millimeter of the pulmonary valvar hinge, but a muscular sleeve lifts the pulmonary leaflets from the septal musculature.

CONCLUSIONS

The pulmonary valvar leaflets are supported entirely by free-standing musculature, having no direct relationship with the ventricular septum. This makes possible the Ross procedure.

The influence of size mismatch on the hemodynamic performance of the pulmonary autograft in vitro

OBJECTIVES

We established an in vitro model to investigate the effect of size mismatch between the aortic and pulmonary root on the hydrodynamic performance and leaflet motion of the pulmonary autograft.

METHODS

Ten fresh porcine pulmonary roots (annulus diameter: 19-25 mm) were tested in a pulsatile flow simulator. The autografts then were implanted in fresh porcine aortic roots (annulus diameter: 19-30 mm) and retested in the flow simulator. Three roots were oversized by 21-39%, three were undersized by 32-45% and there were four size for size implantations. The external diameter of the roots and autografts was measured at the sinotubular junction at hydrostatic pressures of 0 - 120 mmHg. The transvalvular gradient and regurgitation were also measured and the effective orifice area was calculated. The leaflet motion was recorded on video.

RESULTS

The fresh pulmonary roots were more compliant than the fresh aortic roots (46 +/- 8.4% vs. 35 +/- 7.8% dilatation from 0 to 120 mmHg). The group of matching size autografts dilated by 43 +/- 4.9% in the same pressure range. The external diameter of the undersized autografts was 10 +/- 2.1% bigger than before implantation at 0 pressure and then the dilatation was 40 +/- 5.3% at 120 mmHg. The oversized implantation made the autografts 11 +/- 9.4% smaller in their relaxed state, but then they dilated by 65 +/- 11% as the pressure increased to 120 mmHg, resulting in a net dilatation of 54% over the original undilated state. The under or oversizing had little effect on the pressure gradient measured across the valves (5.6 +/- 2.57 mmHg before, 6.3 +/- 3.27 mmHg after implantation). Only the oversized valves showed significantly higher gradients than the native pulmonary valves. The effective orifice area of the undersized autografts was slightly bigger and the oversized autografts was slightly smaller after implantation, although the differences were not significant. The size mismatch did not cause regurgitation on the valves. The video images showed very low-open leaflet-bending deformation, both on the fresh pulmonary and the autograft valves.

CONCLUSION

Under or oversizing the pulmonary autograft up to 40% of the annulus diameter did not affect the hydrodynamic parameters significantly. The compliance of the autograft root was able to compensate for the size mismatch without adversely influencing the valve performance.

Clinical anatomy of the normal pulmonary root compared with that in isolated pulmonary valvular stenosis

OBJECTIVES

This study aimed to clarify the clinical anatomy of the pulmonary root.

BACKGROUND

Many descriptions of valvular anatomy have focused on the annulus, leading to varied interpretations of abnormal valves.

METHODS

Twenty-two heart specimens with isolated pulmonary valvular stenosis were examined to analyze the gross structure of the pulmonary root. For comparison, we examined a normal series of a similar age range together with nine adult hearts. Serial histologic sections were prepared from five specimens.

RESULTS

The normal pulmonary valve is enclosed in a proximal sleeve of free-standing right ventricular infundibulum supporting the fibroelastic walls of the pulmonary sinuses at the anatomic ventriculoarterial junction. The valvular leaflets are attached in semilunar fashion across this junction, delimiting the extent of the valvular sinuses. The stenotic valves were separated into dome-shaped valves, dysplastic valves and a third group of less typical cases. In the dome-shaped valves, which had a relatively circular origin of their leaflets, three raphes were tethered to the arterial wall at the sinutubular junction, producing a waistlike narrowing. The leaflets of the dysplastic valves were attached in a relatively normal semilunar fashion, but stenosis was caused by thickening of the leaflets at their free edges. Serial histologic sections through normal and abnormal valves failed to demonstrate any well defined fibrous "annulus" that could be of clinical relevance.

CONCLUSIONS

Unlike the normal and the dysplastic valves, the dome-shaped valves have circular rather than semilunar lines of attachment of the valvular leaflets. Liberation of the fused zones of apposition of the leaflets within the dome is unlikely to restore such abnormal valves to normal structure, even if this procedure relieves the stenosis.

Morphology of the pulmonary and aortic roots with regard to the pulmonary autograft procedure

Aortic root replacement with the pulmonary autograft warrants a thorough histologic comparison of the morphologic characteristics of the pulmonary and aortic roots. For this purpose nine normal heart specimens (7 neonatal and 2 adult hearts) were studied. Histologic study confirmed the collagenous anulus in both roots to be a complex circular-shaped structure, intricately interposed between the elastic lamellae of the arterial wall and the ventricular structures of the heart. In this sinus the elastic lamellae of the arterial wall continue along the luminal side with collagen being situated at the outside. At the interleaflet triangle this relation is reversed. Surprisingly, islet of elastic fibers were found in the otherwise completely collagenous interleaflet triangles. The amount of elastic lamella distal to the commissures was in both arteries higher than that in the middle of the sinuses, with a preponderance in the aorta as compared with the pulmonary trunk. The pulmonary root anulus proximally inserts into the relatively thin right ventricular myocardium, whereas the aortic root anulus inserts into the thick left ventricular myocardium and several fibrous structures. The pulmonary root is hardly supported by the right ventricular myocardium, whereas the aortic root is supported by its wedged position between the left and right atrioventricular anuli and the bulging thick left ventricular myocardium. When the pulmonary autograft is used for aortic root replacement it should be inserted as proximally as possible to get the support of the fibrous structures of the left ventricular outflow tract and the surrounding ventricular and atrial myocardium.

Is there such a thing as the "tendon of the infundibulum" in the heart?

The fibrous skeleton of the heart has featured prominently in anatomical and surgical descriptions, although all its purported components are difficult to demonstrate. In descriptions of the skeleton, there have been repeated references to the presence of a tendon (or ligament) between the aortic and pulmonary roots. Such a tendon is rarely, if ever, discussed in the context of surgical procedures being carried out on the ventricular outflow tracts. Our study was undertaken, therefore, to investigate the existence and nature of such a tendon or ligament. Serial transverse sections were made through roots of aorta and pulmonary trunk in an intact fetal heart. In addition, ten normal adult hearts were dissected to display the components of the fibrous skeleton of the heart. No discrete fibrous or elastic structure could be detected in the tissue plane between the aortic sinuses and the subpulmonary muscular infundibulum, although a fascial strand was observed in one heart. Apart from this specimen, the space between the free-standing muscular subpulmonary infundibulum and the sinuses of aorta hearing the coronary arteries was occupied only by loose fibroareolar tissue. The initial presence of the ligament was described following studies of animal and macerated human hearts. Subsequently, it would seem its existence has been passed down through generations of morphologists and surgeons without its presence being reconfirmed. We have been unable to demonstrate any structure approximating to the initial illustrations.

Anatomic fitting studies of a total artificial heart in heart transplant recipients. Critical dimensions and prediction of fit

Anatomic fitting studies of the Cleveland Clinic-Nimbus total artificial heart were performed in 33 patients undergoing heart transplantation. The pump fit in the pericardial space in 20 men (80%) and 4 women (50%). There was no significant difference between the Fit and Non-Fit groups in external chest dimensions. Among 42 intrathoracic dimensions, the distance from the center of the mitral valve to the diaphragm (Fit: 5.6 +/- 2.2 cm, Non-Fit: 3.6 +/- 0.4 cm, p < 0.00001) and the distance from the caudal end of the pulmonary valve to the diaphragm (Fit: 9.4 +/- 1.6 cm, Non-Fit: 6.3 +/- 0.8 cm, p < 0.0001) were the most critical. To predict anatomic fit, an index (A x B x C) was obtained from chest X-ray measurements (A, the craniocaudal distance from the dorsal region of the 8th left rib to the left diaphragm; B, the maximum left chest width; and C, the maximum anteroposterior sternum-vertebrae dimension). The pump fit in 88.5% of the patients with an index above 1200 cm3, whereas it fit in only 14.3% of the patients with an index below 1200 cm3 (p < 0.001). This index was an easily obtainable, good predictor of anatomic fit.

Percutaneous balloon valvuloplasty for pulmonic stenosis in adolescents and adults

BACKGROUND

Percutaneous balloon valvuloplasty has been the accepted first-line treatment for congenital pulmonic stenosis in children. Its efficacy in adolescents and adults is less well defined.

METHODS

Between December 1985 and July 1995 we performed percutaneous pulmonic valvuloplasty with a single Inoue balloon catheter in 53 adolescent or adult patients 13 to 55 years of age (mean [+/- SD], 26 +/- 11). Follow-up studies were performed 0.2 to 9.8 years after the procedure (mean, 6.9 +/- 3.1) by Doppler echocardiography (in all the patients) and by cardiac catheterization and angiography (in nine patients).

RESULTS

After balloon valvuloplasty, the systolic pressure gradient across the pulmonic valve decreased from 91 +/- 46 mm Hg to 38 +/- 32 mm Hg (P < 0.001), and the diameter of the pulmonic-valve orifice increased from 8.9 +/- 3.6 mm to 17.4 +/- 4.6 mm (P < 0.001). In the nine patients catheterized at follow-up, the systolic gradient decreased from 107 +/- 48 mm Hg before valvuloplasty to 50 +/- 29 mm Hg after valvuloplasty and to 30 +/- 16 mm Hg at follow-up (P < 0.001 for the comparison of the gradient before and after valvuloplasty; P < 0.001 for the comparison before valvuloplasty and at follow-up; and P < 0.05 for the comparison after valvuloplasty and at follow-up). In the same nine patients, the diameter of the pulmonic valve, as measured by right ventricular angiography, increased from 8.3 +/- 1.4 mm before valvuloplasty to 17.2 +/- 2.0 mm after valvuloplasty (P < 0.001) and to 18.4 +/- 1.4 mm at follow-up (P = 0.08). Incompetence of the pulmonic valve was noted in 7 of the 53 patients (13 percent) after balloon valvuloplasty, but it had disappeared at follow-up in all of them.

CONCLUSIONS

Patients with congenital pulmonic stenosis who present in late adolescence or adult life can be treated with percutaneous balloon valvuloplasty with excellent short-term and long-term results that are similar to those in young children.

Anatomic and physiologic bases for the Ross procedure

Now that the Ross procedure (RP) has been established as the best method of aortic valve replacement (AVR) in several cohorts of patients, it is appropriate to analyze the evolution, as well as the anatomic and physiologic bases for it. Reviewing the evolution of this operation, one may understand the time lapse between its inception and the universal performance of this procedure. Experimental work began as early as 1927 by Hochrein. He was followed by the Stanford group, Lower in 1960 and 1961, and Pillsbury and Shumway in 1966. Successful clinical application by Donald Ross in 14 patients, two in the mitral and 12 in the aortic positions, was accomplished in 1967. Several important developments followed, including Marcel Geens' study of the blood supply to the ventricular septum in 1971 together with the improvement in surgical results following the initial experience of Gonzalez-Lavin and Ross. Further developments included assessment of the tensile strength of the pulmonary valve (PV) by Gorczynski (1982), ability to grow by Murata (1984), a finding of low Ca++ content of the PV by Livi in 1987 and of excellent hydraulic function by Wareesena in 1994. Finally there was universal acceptance by Elkins, Duran, and others, culminating with the Ross Registry and the establishment of the Ross Colloquium by Oury et al. A review of the anatomical features of the PV are compared with those of the aortic valve (AV), including gross anatomy and relationship to the sinotubular junction, scan microscopy and anisotropic properties of both AV and PV. The blood supply to the ventricular septum will be outlined by reviewing Marcel Geens work. The hemodynamics as reported by several investigators are reviewed. The clinical evidence of growth by Elkins et al. is outlined. Based on this increasing knowledge, indications and contraindications for AVR by the RP are discussed.

Relationships between the dimensions of the human aortic and pulmonary valve leaflets: implications on Ross' operation

The technique of replacing the aortic valve with the patient's pulmonary valve and the implantation of a homograft in the pulmonary position was first introduced by D. Ross in 1967. Despite the many advantages and successes of this procedure, it frequently results in some degree of valve insufficiency. In order to optimize the results of Ross' operation, we carried out a comparative study (n = 22) of the relative dimensions of the human aortic and pulmonary valve leaflets using a digitizer. The digitizer supplies the spatial coordinates of a given point (in a pre-chosen reference frame), by the positioning of its sensor on that point. By digitizing relevant points marked on the arterial wall we were able to calculate the distance between the commissures and the perimeter of each leaflet. Analysing the values thus obtained, we found that in 17 of the 22 cases studied (77.3%) there was one orientation (out of the three anatomically possible orientations) of the pulmonary valve, relative to the configuration of the recipient aortic root, that was clearly better than the other two. This study led to the formulation of a "rule" that, in most of the cases studied (86.4%), led to the best fitting orientation of the autograft using the knowledge of the intercommissural distances.

A comparison of macroscopic lipid content within porcine pulmonary and aortic valves. Implications for bioprosthetic valves

Lipid droplets have been demonstrated within both explanted porcine bioprostheses and normal porcine aortic valves. Because of the increasing interest in pulmonary valves as an allograft or xenograft aortic valve substitute, we examined the incidence and distribution of such lipid deposits in 50 porcine aortic valves and 50 matched porcine pulmonary valves. All 300 cusps were removed with surgical scissors and, under a dissecting microscope, the ventricularis layer was removed to expose the spongiosal layer. Macroscopic extracellular lipid droplets analyzed by means of a dissecting microscope with an eyepiece grid and stereology point-counting techniques to provide an area-density average spatial probability map for each cusp. Only 8% of porcine aortic valves were free of lipid, with the distribution of the lipids being 52% +/- 14% right coronary cusp, 90% +/- 8% left coronary cusp, and 68% +/- 13% noncoronary cusp. Of the pulmonary valves, 60% were free of lipid, with the incidence of lipids being 26% +/- 12% left cusp, 6% +/- 7% right cusp, and 12% +/- 9% anterior cusp. Subsequently, lipid cluster samples underwent thin-layer chromatography, which showed them to be phospholipids, oleic acid (fatty acid), triglycerides, and unesterified cholesterol. One primary mode of bioprosthetic valve failure is leaflet calcification. The similarity of distribution within the spongiosal layer between leaflet calcification and intrinsic cusp lipids suggests that the observed lipids might act as a nucleation site for calcification. The substantially lower incidence of lipid in pulmonary valves therefore may represent a potential benefit when these valves are considered for use as aortic valve replacements.

Swine hearts: quantitative anatomy of the right ventricle

The right ventricle was studied in 75 anatomically normal swine hearts, using, in all, nine geometric and volumetric parameters: ventricular-wall thickness, length of the right-ventricular inflow and outflow tracts, and volume of the right-ventricular inflow and outflow tracts. The data for these parameters were compared with previously published patterns for human hearts and volumetric data were compared with patterns of normality found in human hearts. As in the human heart, the ventricular inflow tract in swine hearts was significantly shorter than the outflow tract (P < 0.0001).

Porcine pulmonary and aortic valves: a comparison of their tensile viscoelastic properties at physiological strain rates

Pulmonary valve autografts and allografts have been recently reported as being clinically effective for the replacement of the diseased aortic valve. While the biomechanics of the aortic valve have been widely studied, there is little information available about the mechanical properties of the pulmonary valve. We felt that it was necessary to investigate the mechanical properties of the pulmonary valve to determine if it is mechanically suitable as a long term replacement for the aortic valve. We employed physiological strain rate tensile testing to investigate the stress-strain and stress relaxation behaviour of 44 aortic and 40 pulmonary valve cusp strips cut in the radial and circumferential directions, in fresh and glutaraldehyde fixed states. Stress-strain and stress relaxation tests were performed on each test strip at extension rates of 40 mm/s, 4 mm/s and 0.4 mm/s. In all but one mechanical parameter, we found no difference between aortic and pulmonary valve tissues. The extensibilities and relaxation rates were similar, but the aortic valve tissue had a greater average modulus (p = 0.0005) than the pulmonary valve tissue (i.e. 7.41 MPa vs. 5.86 MPa respectively). Since bioprostheses are often constructed from materials with mechanical properties very different from those of the aortic valve, like pericardium, the slight difference between aortic and pulmonary valves is unlikely to affect the operation of the pulmonary valve in the aortic position. The pulmonary valve could therefore be considered mechanically acceptable as a replacement for the aortic valve.

Age-related changes in normal Chinese hearts

The heart weights, ventricular wall thickness and valve circumferences were measured in 507 autopsy specimens of normal hearts from persons aged from 10 to 90 years. The heart weights increased with age and were greater in the males than in the females, except from the 6th to 8th decades where they were reversed. The body weight was the best predictor of heart weight. The ventricular wall thickness in males did not differ significantly from that in females. The values of the indexed left ventricular wall thickness (i.e. values divided by BSA) in the females exceeded those in the males from the 6th to 9th decades. The mean valve circumference was greater in the males but it was significant (P < 0.05) only for the tricuspid valves at the 9th decade of life. The pulmonary valve circumferences were greater than the aortic for all decades and the ratio of the aortic to pulmonary valve circumference remained constant. In the clinical evaluation of the specimens of Chinese hearts, the absence of the aged-related dilatation of the aorta described in Caucasian hearts should be duly taken into account.

Anomalous origin of the left coronary artery from the pulmonary trunk and its relationship with the morphology of the cardiac semilunar valves in Syrian hamsters

The conditions of the aortic and pulmonary valves and the arrangement in the origin of the coronary arteries were studied in 247 Syrian hamsters belonging to a single family subjected to high endogamous pressure. Most specimens (n = 216) were examined using a stereomicroscope. The remaining 31 were studied histologically. In 110 specimens both cardiac semilunar valves were normal. The aortic valve was bicuspid and the pulmonary valve was normal in 79 animals, while a normal aortic valve and a bicuspid pulmonary valve occurred in 37. In the remaining 21 specimens both semilunar valves were bicuspid. In 34 cases, the left coronary artery originated from the pulmonary trunk. Statistical analyses indicate that there is no significant relationship between the bicuspid condition of the pulmonary valve and the fact that a coronary artery arises from the pulmonary trunk. On the other hand, they substantiate that the frequency of this coronary artery anomaly significantly increases when the aortic valve is bicuspid. The present findings agree with the hypothesis that abnormal migration of the neural crest cells may be responsible for the combined occurrence of bicuspid aortic valve and anomalous origin of the left coronary artery from the pulmonary trunk. In addition, they suggest that the neural crest cells involved in the formation of the pulmonary valve diverge from those migrating into the aortic valve and those imposing spatial order upon the development of the proximal coronary arteries.

Fate of the autologous tri-cusp-valved pericardial conduit in the right ventricular outflow tract of growing pigs

No perfect valve or valved conduit is currently available to reconstruct the right ventricular outflow tract (RVOT) in pediatric patients. To investigate the fate of autologous pericardial valved conduit, twenty piglets weighing 12.2 +/- 1.4 kg were divided into two groups. In 10 of them, the pericardium was immersed in 0.6% glutaraldehyde for 5 minutes (Gr PG) and then washed with normal saline. In the other 10 pigs, the pericardium was immersed in normal saline only (Gr PN) after procurement. Afterwards the autologous pericardium was tailored as designed to build a tri-cusp-valve inside the pericardial conduit with reconstruction of the sinus of Valsalva. This conduit was connected to the pulmonary trunk (PT) distally and RVOT proximally without a pump. The PT was then doubly ligated just above the annulus. The pigs survived 114 +/- 92 days in Gr PG and 82 +/- 50 days in Gr PN. The body weight increased to 42 +/- 29 kg in Gr PG and 30 +/- 9 kg in Gr PN. No cusps adhered to the conduit wall in either group. In Gr PN, the valve became retracted; in 7 of them an aneurysm developed proximal to the stenotic pulmonary valve, while only one pig in Gr PG developed an aneurysm. In Gr PG, the leaflet and conduit showed evidence of growth. In contrast, no evidence of valve growth was found in Gr PN. Calcification was evident more in Gr PG than in Gr PN either on the leaflet (9/10 vs. 5/10) or in the wall of conduit (8/10 vs. 6/10), but the differences were not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Replacement of the aortic valve with a pulmonary autograft: the "switch" operation

The transfer of the patient's own pulmonary valve to the aortic position developed from our earlier work with aortic homografts. The valve shows no progressive tissue failure and offers the prospect of a permanent valve replacement for young people. Like homografts, the valves can be inserted in the subcoronary position or as a root replacement. In infants and growing children root replacement should be used to benefit from the valve's growth potential.

Pulmonary stenosis with intact ventricular septum: assessment and indication of reconstructive surgery for residual right-ventricular outflow tract obstruction

If not all of the right ventricular outflow tract obstruction (RVOTO) is removed in the operation for pulmonary stenosis, high right ventricular pressure can sometimes occur afterward. However, it is not easy to assess the amount of RVOTO that is to be removed, and there is no quantifiable method for selecting operative procedures. The aim of this report is to discuss the formulation of a numerical indicator, based on the parameters peak systolic right-ventricular pressure (RVP), systolic systemic arterial pressure (AP), pulmonary valvular orifice size (VS), and body surface area (BSA), from the results obtained in sixty-four open heart surgeries for pulmonary stenosis with intact ventricular septum. A group, in which an outflow tract patch was not used and which had a higher pre-operative RVP/AP ratio, had a tendency to have a correspondingly higher RVP/AP ratio one month after the operation. Most patients with a high RVP/AP ratio one month after the operation showed a significant decrease in this ratio a long time after the operation. But, there were exceptions to this rule where the ratio remained high. Reconstruction of the right ventricular outflow was considered for some patients whose RVP/AP ratios remained high. Reconstruction of the RVOT by using an outflow tract patch worked well for patients with an associated infundibular stenosis. A subannular patch was used for patients with infundibular stenosis, and a transannular patch was used for patients with annular stenosis. The optimal annulus size was such that VS/BSA was not less than 2 cm2/m2. A transannular monocusp patch was applied to an area which was more than 10 mm wide.(ABSTRACT TRUNCATED AT 250 WORDS)

The quantitative anatomy of the normal human heart in fetal and perinatal life

A total of 367 human fetuses and newborn subjects weighing from 60 to 5000 g provided the material for a morphometric study of the heart. A total of 17 interventricular parameters were measured in each specimen, one of the parameters representing an innovation with regard to the classically used set of measurements. A new anatomo-geometric configuration is described for each ventricle along with a new component for the left ventricular outflow tract, designated as the aortic outflow tract. The appropriate stereometric formulas were used to calculate real ventricular volumes rather than the previously studied volumetric indices. Additionally, correlation indices were calculated for ventricular wall thickness as well as the circumferences and diameters of the atrioventricular and arterial valves. The results show that, in fetuses of up to 2700 g in body weight, ventricular wall thickness is greater in the right than in the left ventricle, although the opposite is true in fetuses weighing above 2700 g. Throughout the range of weights studied, ventricular volume was greater in the left than in the right chamber. Tricuspid and pulmonary valve circumference and diameter were consistently greater than in the mitral and aortic valves, respectively. We believe the new morphometric data and their innovative interpretation to have immediate applications in both the morphological and functional areas of cardiology.

Dimensions of the great arteries, semilunar valve roots, and right ventricular outflow tract during growth: normative angiocardiographic data

Systolic and diastolic diameters of the right and left pulmonary arteries (RPAD, LPAD), descending thoracic aorta (DTAD), right ventricular infundibulum (RVID), and pulmonary and aortic valve roots at the proximal, commissural and distal levels were estimated from angiocardiograms in 24 infants, children, and adolescents without heart disease, and correlated with body surface area (BSA), stroke volume (SV), cardiac output (CO), and ventricular volumes. The relationships between cardiovascular diameters and BSA were better expressed by a power function than by the other functions tried. We obtained different exponents for pulmonary and aortic valve annuli and the more distally measured great arteries (RPAD, LPAD, and DTAD), suggesting different growth patterns. The right ventricular infundibular shortening fraction (RVISF) was weakly correlated with BSA (r = -0.328), and the values obtained indicated constancy during normal growth. There was a direct proportional relationship between the pulmonary valve annulus diameter and the cube root of the right ventricular volume (r = 0.952), as well as between SV and cross-sections of the right pulmonary artery (RPAC; r = 0.916), left pulmonary artery (LPAC; r = 0.878) and descending thoracic aorta (r = 0.962). RPAC and LPAC were strongly correlated (r = 0.940), the RPAC being significantly larger than the LPAC.

Pulmonary atresia with and without ventricular septal defect: a different etiology and pathogenesis for the atresia in the 2 types?

In 15 of 20 hearts of neonates with pulmonary atresia and intact septum (PA-IVS) and in 4 with critical pulmonary stenosis, the pulmonary valve consisted of 3 fused cusps. One of the 11 patients with a ventricular septal defect (PA-VSD) had a well-developed pulmonary root; in 8 the pulmonary trunk arose from a dimple. Two had a bicuspid valve. In 10 of the 20 patients with PA-IVS and in those with critical stenosis, the diameter of the pulmonary trunk was normal or larger than normal. The authors believe that this is related to flow through an initially patent pulmonary valve and, perhaps more importantly, to poststenotic dilatation. In all hearts with PA-VSD, the pulmonary trunk was very small. In the patients with PA-IVS and a normal-sized pulmonary trunk and in 3 with critical pulmonary stenosis, the morphology of the ductus arteriosus was normal, suggesting that even in the former the valve was patent before birth, allowing forward flow. In all patients with small pulmonary trunk, the ductus was long, tortuous, and originated from the aortic arch in a proximal position, suggesting that reversal of flow had occurred early in development. The authors postulate that in patients with ventricular septal defect (VSD), the pulmonary ostium becomes atretic early in development, at or shortly after partitioning of the truncoconal part of the heart has taken place but before closure of the ventricular septum. In patients with intact ventricular septum, on the other hand, atresia very likely occurs sometime after cardiac septation has been completed. In these cases the pulmonary atresia may be due to a prenatal inflammatory process, rather than representing a true congenital malformation.