[Usefulness of isovolumic acceleration and tissue Doppler echocardiographic parameters for predicting postoperative functional recovery after heart valve surgery]

INTRODUCTION AND OBJECTIVES

Postoperative right ventricular (RV) systolic dysfunction is associated with perioperative myocardial ischemia, hypothermic cardiac arrest, cardiopulmonary bypass and pericardial injury. As myocardial acceleration during isovolumic contraction (IVA) and myocardial velocity during isovolumic contraction (IVV) are little affected by loading conditions, they can predict myocardial function better than conventional parameters. We investigated the usefulness of these parameters for predicting postoperative RV systolic function after isolated heart valve surgery.

METHODS

Overall, 63 patients who underwent isolated heart valve surgery were evaluated by tissue Doppler echocardiography preoperatively, and immediately and 6 months postoperatively.

RESULTS

By the 6-month follow-up, patients' New York Heart Association functional class had improved significantly (P< .026). At that time, functional recovery was observed in 38 of the 63 patients. Logistic regression analysis demonstrated that RV IVA (odds ratio [OR]=3.1; 95% confidence interval [CI], 1.01-9.64; P=.047) and pulmonary artery systolic pressure (OR=1.07; 95% CI, 0.99-1.15; P=.07) were independent predictors of functional recovery 6 months postoperatively. The RV IVA value had recovered by the 6-month follow-up in 39 patients. A positive correlation was observed between functional recovery and IVA recovery (Spearman's correlation, r=0.499; P< .001). The RV IVA was observed to recover in all patient groups regardless of surgical method or atrial rhythm.

CONCLUSIONS

Preoperative RV IVA and pulmonary artery systolic pressure were independent predictors of functional recovery 6 months after isolated heart valve surgery. Given its association with functional recovery, postoperative improvement in these parameters may be a useful clinical indicator after heart valve surgery.

Gender effects on cardiac valvular function in hyperprolactinaemic patients receiving cabergoline: a retrospective study

BACKGROUND

Ergot-derived dopamine agonists are associated with increased risk of valvular dysfunction in Parkinson's disease. The risk of valvular disease associated with lower doses of cabergoline used to treat prolactinomas remains controversial.

OBJECTIVE

To determine whether there is an association of cabergoline and valvular function in patients with hyperprolactinaemia according to gender.

DESIGN

Case-record retrospective study.

SETTING

Outpatient neuroendocrine clinical centre at a tertiary care hospital.

STUDY PARTICIPANTS

One hundred patients (48 men and 52 women) with hyperprolactinaemia who had an echocardiogram while receiving cabergoline for at least 6 months.

CONTROLS

One hundred controls (48 men and 52 women) selected from Massachusetts general hospital (MGH) database of echocardiograms without clinically significant findings, matched to patients for age, gender, body mass index (BMI) and hypertension.

MAIN OUTCOME MEASURE

Echocardiogram.

RESULTS

There were no significant differences in valvular function in patients compared with controls. However, women patients had a higher prevalence of mild tricuspid regurgitation (TR) than female controls (15.4%vs. 1.9%, P = 0.03). Among men only, patients had more trace TR than controls (68.8%vs. 45.8%, P = 0.02). The mild valvular regurgitation in patients was not clinically significant and did not correlate with dose, duration or cumulative dose.

CONCLUSIONS

Overall cabergoline was not associated with valvulopathy. However, subdivided by gender, hyperprolactinaemic men and women had higher prevalence of trace or mild TR, respectively, compared with gender matched controls. There may be gender differences in valvular dysfunction associated with cabergoline. Longer term, larger studies are necessary to evaluate definitively an effect of cabergoline on valvular function in hyperprolactinaemic patients.

Mathematical modeling of flow-generated forces in an in vitro system of cardiac valve development

Heart valve defects are the most common cardiac defects. Therefore, defining the mechanisms of cardiac valve development is critical to our understanding and treatment of these disorders. At early stages of embryonic cardiac development, the heart begins as a simple tube that then becomes constricted into separate atrial and ventricular regions by the formation of small, mound-like structures, called atrioventricular (AV) cushions. As valve development continues, these mounds fuse and then elongate into valve leaflets. A longstanding hypothesis proposes that blood flow-generated shear stress and pressure are critical in shaping the cushions into leaflets. Here we show results from a two-dimensional mathematical model that simulates the forces created by blood flow present in a developing chick heart and in our in vitro, tubular model system. The model was then used to predict flow patterns and the resulting forces in the in vitro system. The model indicated that forces associated with shear stress and pressure have comparable orders of magnitude and collectively produce a rotational profile around the cushion in the direction of flow and leaflet growth. Further, it was concluded that the replication of these forces on a cushion implanted in our tubular in vitro system is possible. Overall, the two-dimensional, mathematical model provides insight into the forces that occur during early cardiac valve elongation.

Prolonged QT dispersion in children with congenital valvular aortic stenosis

BACKGROUND

Hypertrophied and ischemic cardiac muscle in patients with aortic valve stenosis becomes a potential source of ventricular cardiac arrhythmia that can lead to sudden death. Arrhythmia is associated with an abnormal duration of the action potential in a cardiac muscle cell. The aim of this prospective study was to analyze QT dispersion in children with different stages of aortic valve stenosis and different left ventricular mass indexes.

MATERIAL/METHODS

Sixty children with aortic valve stenosis were divided into 3 subgroups according to their pressure gradients. Sixty healthy children served as controls. Doppler echocardiography, standard 12-lead electrocardiography and 24-hour Holter monitoring electrocardiography were performed.

RESULTS

QT dispersion was significantly higher in children with aortic stenosis than in the control group. There were statistically significant positive correlation between QT dispersion and left ventricular mass index and between QT dispersion and pressure gradient. QT dispersion was significantly higher in 20 patients with aortic stenosis and ventricular arrhythmia than that in patients without arrhythmia. In children with a higher pressure gradient and a higher left ventricular mass index, more complex arrhythmia was found.

CONCLUSIONS

Risk of ventricular arrhythmia increases with the degree of aortic valve stenosis and cardiac muscle hypertrophy. QT dispersion is prolonged in children with aortic valve stenosis, particularly in patients with arrhythmia, and increases with pressure gradient and left ventricular mass index.

Echocardiographic and histological assessment of age-related valvular changes in normal rats

Aging is associated with morphologic and functional alterations of the rat's left ventricle. However, the time-course of valvular function and morphology in normal aging rats has not yet been studied. For this purpose, 30 male Wistar rats (318 +/- 5g, 10 weeks old) underwent serial echocardiograms for 58 weeks under sodium pentobarbital 50 mg/kg IP anesthetization followed by necropsy. Histopathology was also performed in two additional groups of 10 rats at 10 and 30 weeks of age. Regurgitations were considered as any retrograde flow on 2-D or M-mode color Doppler echocardiography. Tricuspid regurgitation was already found at 10 weeks of age and became more frequent with age. Pulmonary, mitral and aortic regurgitation was seldom observed at 10 weeks but became more frequent after 30 weeks. For the mitral and aortic valve, this was also associated with an increase in valvular thickness because of nodular or segmental myxoid leaflet changes. The severity of valvular regurgitations did not increase with age. In conclusion, aging leads to morphologic and functional valvular changes in normal rats. This is important when investigating models of valvular heart disease in small animals.

A review of state-of-the-art numerical methods for simulating flow through mechanical heart valves

In nearly half of the heart valve replacement surgeries performed annually, surgeons prefer to implant bileaflet mechanical heart valves (BMHV) because of their durability and long life span. All current BMHV designs, however, are prone to thromboembolic complications and implant recipients need to be on a life-long anticoagulant medication regiment. Non-physiologic flow patterns and turbulence generated by the valve leaflets are believed to be the major culprit for the increased risk of thromboembolism in BMHV implant recipients. In this paper, we review recent advances in developing predictive fluid-structure interaction (FSI) algorithms that can simulate BMHV flows at physiologic conditions and at resolution sufficiently fine to start probing the links between hemodynamics and blood-cell damage. Numerical simulations have provided the first glimpse into the complex hemodynamic environment experienced by blood cells downstream of the valve leaflets and successfully resolved for the first time the experimentally observed explosive transition to a turbulent-like state at the start of the decelerating flow phase. The simulations have also resolved a number of subtle features of experimentally observed valve kinematics, such as the asymmetric opening and closing of the leaflets and the leaflet rebound during closing. The paper also discusses a future research agenda toward developing a powerful patient-specific computational framework for optimizing valve design and implantation in a virtual surgery environment.

A spheroidal control volume for the quantitative measurement of regurgitant flow by cardiac MRI

PURPOSE

We sought to show that a spheroidally shaped control volume (CV), formed from a minimal MRI data set, can be used to measure regurgitant flow through a defective cardiac valve consistently and accurately under a variety of flow conditions.

MATERIALS AND METHODS

Using a pulsatile flow pump and phantoms simulating severe valvular regurgitation, we acquired 31 scans of two or three radially oriented slices, using a variety of flow waveforms and regurgitant volumes of 12 to 55 ml. Data sets included high- and low-resolution scans, and variable-rate sparse sampling was also applied to reduce the scan time. An oblate spheroid was placed in the pump chamber opposite the jet and fit as tightly as possible to isomagnitude velocity contours at 25% of the velocity encoding limit.

RESULTS

Normalized regurgitant volumes (NRVs) expressed as a percentage of the pump setting were obtained from the product of the spheroid surface area with the velocities normal to it. Mean +/- SD NRV values were 96.8 +/- 6.6% for all scans. Imaging times in the breath-hold range were obtained using reduced resolution and variable-rate sparse sampling approaches without significant degradation in accuracy.

CONCLUSION

In our preliminary findings, the spheroidal CV method showed clear potential for the development of a robust, clinically feasible technique for the measurement of regurgitant volume.

Defining Ebstein's malformation using three-dimensional echocardiography

Ebstein's malformation is difficult to visualise, for both the echocardiographer and the surgeon. The essence of the problem in Ebstein's malformation is the deviation of the hingepoints of the leaflets towards the junctions of the inlet and apical trabecular parts of the right ventricle. Three-dimensional echocardiography offers new insights into the morphology and function of malformed valves, and allows elucidation of all the features. It allows clear visualisation of the valve leaflets, showing the precise morphology of the valve leaflets, the extent of their formation, the level of their attachment, and their degree of coaptation. Visualisation of the mechanism of regurgitation or stenosis is possible, as is more accurate quantification of the regurgitant jet or jets. Subchordal apparatus may be seen more clearly using three-dimensional echocardiography, and their functional anatomy understood. The multiplanar review modality allows examination of the three-dimensional data set even in patients with sub-optimal echocardiographic imaging. Previously, much of this information could only be well-understood at the time of surgery or post mortem, meaning that the majority of the specimens fully examined were at the poorly functioning end of the spectrum. This information is of use in furthering our understanding of this complex lesion as it functions in vivo, and demonstrating which anatomical pathology is significant in producing functional and physiological consequences. It is also of use for the clinician in selecting which patients are amenable to surgical intervention, for either single or biventricular repair, and for the surgeon in planning how to approach the operation. Correlation between three-dimensional echocardiographic findings and surgical findings has already been established, but the effect of this enhanced anatomical knowledge on surgical planning and surgical outcome requires further investigation.

Role of matrix metalloproteinases and their tissue inhibitor of metalloproteinases in myxomatous change of cardiac floppy valves

To clarify the underlying cause of myxomatous changes in cardiac floppy valves, the expression of the matrix metalloproteinases (MMP) and the tissue inhibitors of metalloproteinases (TIMP) was investigated in cardiac valves. Valves were obtained from nine patients with floppy valves, from 13 patients with other valvular disease types, and from four patients with normal valves. Immunohistochemical analyses for MMP-2, MMP-9, TIMP-1, and TIMP-2, and gelatin zymography for MMP-2 and MMP-9 were performed. Compared with the spongiosa of normal valves, the myxomatous area of floppy valves had stronger immunohistochemical reaction to MMP-2 and MMP-9, and weaker reaction to TIMP-2. Activated MMP-2 and MMP-9 were detected in eight out of nine cases of floppy valves. Activated MMP-2 was detected at low levels in two cases of normal valves showing mild expansion of the spongiosa without macroscopic floppiness. The ratio of active/total MMP-2 and MMP-9 increased in floppy valves compared with normal valves. These results suggest that the imbalance between MMP and TIMP and the increased activity of MMP-2 and MMP-9 may correlate with myxomatous changes observed in floppy valves. Valves with a slight myxomatous change and activated MMP-2 may develop into floppy valves with increases in the activity of MMP.

Real-time three-dimensional echocardiography: technological gadget or clinical tool?

The complex anatomy of cardiac structures requires three-dimensional spatial orientation of images for a better understanding of structure and function, thereby improving image interpretation. Real-time three-dimensional echocardiography is a recently developed technique based on the design of an ultrasound transducer with a matrix array that rapidly acquires image data in a pyramidal volume. The simultaneous display of multiple tomographic images allows three-dimensional perspective and the anatomically correct examination of any structure within the volumetric image. As a consequence, it is less operator-dependent and hence more reproducible. Dedicated software systems and technologies are based on high-performance computers designed for graphic handling of three-dimensional images by providing possibilities beyond those obtainable with echocardiography. This methodology allows simultaneous display of multiple superimposed planes in an interactive manner as well as a quantitative assessment of cardiac volumes and ventricular mass in a three-dimensional format without a pre-established assumption of cardiac chamber geometry. In addition, myocardial contraction and/or perfusion abnormalities are clearly identified. Finally, real-time three-dimensional colour Doppler flow mapping enables complete visualisation of the regurgitant jet and new ways of assessing regurgitant lesion severity. Thus, this technique expands the abilities of non-invasive cardiology and may open new doors for the evaluation of cardiac diseases. In this article, current and future clinical applications of real-time three-dimensional echocardiography are reviewed.

Clinical Application of Tissue Doppler Imaging in Patients With Idiopathic Pulmonary Hypertension

BACKGROUND

Tissue Doppler (TD) echocardiographic imaging of mitral and tricuspid annulus has been applied to assess right ventricular (RV) and left ventricular (LV) function in many cardiac diseases, but its clinical application, including response to long-term targeted therapy in patients with idiopathic pulmonary hypertension (PH), has not been addressed.

METHODS

Seventy patients with idiopathic PH were compared with 35 age-matched control subjects to examine myocardial velocities by TD. Of these, 35 patients underwent repeat imaging after long-term targeted therapy. In addition, 50 consecutive patients with idiopathic PH with simultaneous right-heart catheterization and echocardiography were examined.

RESULTS

No significant differences were noted between PH patients and the control group in lateral mitral annulus systolic velocity and early diastolic velocity (Ea) by TD, but septal velocities were significantly lower (p < 0.01). With targeted therapy, myocardial velocities at the septum and RV free wall increased significantly (p < 0.05). Likewise, E/Ea ratio increased, albeit still in the normal range. In all 50 patients with invasive measurements, lateral E/Ea ratio readily identified normal mean pulmonary capillary wedge pressure (PCWP).

CONCLUSIONS

TD imaging of the lateral mitral annulus can reliably predict the presence of normal/reduced mean PCWP in patients with idiopathic PH, and track the improvement in RV function and LV filling with long-term targeted therapy.

[New insight into the treatment of aortic stenosis]

Aortic valve stenosis (AS) is the most frequent heart disease after coronary artery disease and arterial hypertension and it is associated with a high incidence of adverse outcomes. Historically, calcific AS has been considered as "degenerative" because it was thought to be the result from aging and "wear and tear" of the aortic valve. However, this perception has changed over the years with the publication of several studies showing that the calcific AS shares many histological similarities with atherosclerosis, thus suggesting that this disease could eventually be modified by lifestyle or pharmacological therapies. Furthermore, recent data support the notion that AS is not an isolated disease uniquely limited to the valve. Indeed, AS is frequently associated with abnormalities of the systemic arterial system, and in particular with reduced arterial compliance, which may have important consequences on the pathophysiology and clinical outcome of this disease. Hence, the assessment of AS severity as well as its therapeutic management should be conducted with the use of a comprehensive evaluation that includes not only the aortic valve but also the systemic arterial system and the left ventricle, since these 3 entities are tightly intricated on both the pathophysiological and hemodynamic standpoints.

Cerebral infarction in Hunter syndrome

Hunter syndrome, or mucopolysaccharidosis type II, is an X-linked recessive disorder resulting from iduronate sulfatase deficiency. Typical manifestations include short stature, mental retardation, hydrocephalus, macroglossia and cardiac valvulopathy. We describe a 21-year-old patient who presented with acute ischemic stroke and evidence of cerebral embolization. The echocardiogram demonstrated thickened mitral and aortic valves as potential sources of emboli. We conclude that ischemic stroke secondary to cardioembolization is a potential complication of Hunter syndrome.

Heart involvement in systemic lupus erythematosus, anti-phospholipid syndrome and neonatal lupus

Cardiac involvement is one of the main complications substantially contributing to the morbidity and mortality of patients suffering from systemic autoimmune diseases. All the anatomical heart structures can be affected, and multiple pathogenic mechanisms have been reported. Non-organ-specific autoantibodies have been implicated in immune complex formation and deposition as the initial triggers for inflammatory processes responsible for Libman-Sacks verrucous endocarditis, myocarditis and pericarditis. Anti-phospholipid antibodies have been associated with thrombotic events in coronary arteries, heart valve involvement and intra-myocardial vasculopathy in the context of primary and secondary anti-phospholipid syndrome. Antibodies-SSA/Ro and anti-SSB/La antigens play a major pathogenic role in affecting the heart conduction tissue leading to the electrocardiographic abnormalities of the neonatal lupus syndrome and have been closely associated with endocardial fibroelastosis.

Age-related structural changes in cardiac valves: implications for tissue-engineered repairs

Elderly patients would receive substantial benefits from tissue-engineered heart valves (TEHVs), but most TEHV research has not focused on applications for this growing patient population. There will be numerous technical challenges involved in developing TEHVs for the elderly, such as designing tissues to accommodate higher blood pressure and larger aortic roots that may be friable or calcified. Concomitant medications may also affect the biology of the TEHV. Due to the predominantly senescent behavior of cells from older persons, a nonautologous cell source may be required to develop the TEHV. Decellularized heart valve allografts from elderly donors may not be durable enough to use as a scaffold, but several polymer and natural biodegradable scaffolds may provide promising alternatives. The selection of cell sources, scaffolds, and mechanical/biologic conditioning will need to be precisely targeted to meet the diverse physiological, medical, and surgical requirements of elderly patients.

The hemodynamics of the Berlin pulsatile VAD and the role of its MHV configuration

The 3D flow in a model of the Berlin ventricular assist device (VAD) chamber with monoleaflet valves placed in S-shape conduits was simulated numerically. The blood flow dynamics were described in terms of flow patterns, velocity, pressure, and shear stress. The hemodynamic properties and the VAD's potential risk for thrombosis were evaluated in terms of mixing and washout properties, and global estimations of platelet level of activation (LOA). In order to evaluate the role of valves on the flow in the chamber, the flow in a model with bileaflet valves in straight conduits was simulated and compared with the original case. The results showed that in both models a large rotating flow was developed in the chamber during filling. This vortex filled the entire chamber and moved constantly up to the peak ejection phase, resulting in relatively low shear stress (up to 0.4 Pa) and no lasting stagnation regions. Significant shear stresses were found near the valves with higher values near the outlet valve in both models. The configuration of valves and conduits had a large effect on VAD washout and mixing properties, with advantage to the bileaflet model. However, since the bileaflet valves exhibited higher shear stresses, higher LOA were found for the bileaflet model.

Anti-HLA antibodies after cryopreserved allograft valve implantation does not predict valve dysfunction at three-year follow up

BACKGROUND AND AIM OF THE STUDY

As the cause of allograft heart valve degeneration is poorly understood, the study aim was to investigate the host antibody response to allograft valve implantation.

METHODS

Sera were obtained from 92 recipients of allograft heart valves (61 pulmonary, 31 aortic). Sera were tested for anti-HLA class I antibodies by ELISA and complement-dependent cytotoxicity (CDC) methods, and anti-HLA class II antibodies by ELISA. Specificities of recipient anti-HLA class I antibodies were defined by standard CDC testing against a panel of T lymphocytes from 80 blood donors. Donor valve HLA typing was performed on stored donor DNA samples using molecular methods. The presence of donor-specific anti-HLA class I antibodies was hence defined in recipient sera. The presence of anti-HLA antibodies and donor-specific anti-HLA class I antibodies were correlated with function of allograft valves at the most recent echocardiographic follow up.

RESULTS

At a mean of 3.0 years (range: 0.3-5.4 years) after allograft implantation, 96% (87/92) and 82% (75/92) of patients were positive for anti-HLA class I and II antibodies, respectively, by ELISA testing. Some 68% (61/90) of patients were positive for anti-HLA class I antibody (PRA > 5%) by CDC testing. PRA levels decreased with greater postoperative interval (r = -0.31, p = 0.003). In 68 recipients where donor HLA type was defined, 54% (37/68) of patients had antibodies specific to at least one donor HLA class I antigen. In 87 patients with a recent echocardiographic examination available for analysis (at a mean of 3.5 +/- 1.6 years postoperatively), there was no association between valve dysfunction and antibody status.

CONCLUSION

Anti-HLA class I and II antibodies were detected by ELISA methods in most patients after allograft implantation extending to 5.4 years. The clinical significance of these findings is unclear, as no correlation was found between the prevalence of anti-HLA antibody and echocardiographic parameters of valve dysfunction at a mean of 3.5 years follow up.

Pulmonary function assessment in children and teenagers before and after surgical treatment for rheumatic valve disease

OBJECTIVE

To assess pulmonary function in children and adolescents subjected to correction of rheumatic valve disease in order to quantify changes caused by factors inherent to surgery and rheumatic heart disease.

METHODS

This was a longitudinal and quantitative intervention study, undertaken at a children's hospital that is a center of excellence for the state of Pernambuco (Instituto Materno Infantil de Pernambuco), between December 2004 and May 2005. Eighteen children suffering from rheumatic fever and indicated for surgery to repair or replace the mitral valve were assessed preoperatively and again on the first and fifth postoperative days. The parameters recorded were minute volume, rapid shallow breathing index, peak expiratory flow, forced vital capacity and inspiratory capacity.

RESULTS

All patients were aged 8 to 17 years (mean 12.4+/-2.1), they had a mean body mass index of 16.1+/-2.2, and were weaned off invasive mechanical ventilation during the first 10 postoperative hours. All parameters had undergone significant deterioration on the first day (statistically significant, p < or = 0.01), demonstrating gradual improvement up to the last day of assessment, although, with the exception of minute volume which was no longer significantly different from the fourth day onwards (p > 0.01), without returning to baseline levels.

CONCLUSION

We observed that the pulmonary dysfunction that results from this type of heart surgery is maintained until at least the fifth postoperative day. It appears that this dysfunction is influenced by the pain and mechanical alterations caused by sternotomy and reduced pulmonary compliance post surgery.

The optimal method for recording prosthetic heart valve sounds in clinical situations

BACKGROUND

Valve sounds are thought to be useful in evaluating the functioning of prosthetic heart valves. In previous reports, two recording instruments have mainly been used, a condenser microphone (instrument A) and an accelerometer (instrument B), respectively. This study aimed to investigate the applicability of these conventional devices in recording mechanical heart valve sounds in daily clinical situations. In addition, two other instruments, namely, a stethoscope including a small microphone in its tube (instrument C) and an electrostethoscope (instrument D), were proposed and examined.

METHODS

Mechanical valve sounds were recorded from postoperative patients using each-device and the signal to noise ratio (SNR) of each was calculated. Frequency characteristics of the two newly proposed instruments were also investigated by recording a sweep signal in an anechoic chamber.

RESULTS

The SNR values of the new instruments were significantly superior to those of conventional ones (A, sound signals were not defined from noises; B, 0.97 +/- 0.59 dB; C, 11.5 +/- 4.7 dB; and D, 9.4 +/- 3.5 dB, respectively p<0.05). The frequency characteristics of the two newly proposed instruments were also shown to be acceptable (under 10 kHz), though resonance frequency peaks were observed.

CONCLUSIONS

Two newly proposed instruments can record mechanical heart valve sounds more noiselessly and with more ease than previous ones, and their frequency characteristics are acceptable.

Renewed Interest in Preejectional Isovolumic Phase: New Applications of Tissue Doppler Indexes: Implications to Ventricular Dyssynchrony

There is renewed interest in isovolumic contraction (IC) in tissue Doppler echocardiography of the myocardial walls, which is revisited in this editorial with new regional velocity data. The aims are to recall traditional background information and to emphasize the need to master the rapidly evolving tissue Doppler procedures for the accurate display of brief IC. IC, a preejectional component of great physiologic interest, is very demanding in terms of ultrasound technology. The onset and end of its motion velocities should be unambiguously defined versus the QRS complex and ejection wall motion. This is a prerequisite for exploiting the new information as guidance toward new therapeutic strategies from a practical viewpoint. However, IC preload dependence should be kept in mind, because of its limited potential for contractility studies. Finally, when only duration measurements are made in the assessment of ventricular dyssynchrony, regional preejectional duration is the pertinent tool to single out the onset of ejection local wall motion.

[Challenges in the surgical management of hearts with a functional single ventricle]

Nowadays, the complex congenital heart diseases with a functional single ventricular haemodynamics can be treated with good results with bi-directional Glenn (BDG) and total cavopulmonary connection (TCPC) procedure. The late results are determined by the ventricular function.

AIMS

To assess the surgical results of "high risk" BDG and TCPC procedures, where the functional single ventricle were complicated by left sided SVS and IVC, total anomalous pulmonary venous connection (TAPVC) and severe atrioventricular valve insufficiency. These patients' were refused for surgery earlier.

PATIENTS

Between 01. 01. 1994. and 30. 06. 2004. 112 BDG and 93 TCPC (42 pts with extracardiac conduit--ECC) procedures were performed. AGE: 3 months-29 yrs mean: 4,7 yrs, weight: 4-46 kg, mean: 15,5 kg. Among the "high risk" pts.: 1. Bilateral BDG in 19, left BDG in 9, left sided TCPC with ECC in 3 pts. were performed, 2. The associated TAPVC were operated on successfully in 3 pts. (bilateral BDG in 1, left BDG in 1, left sided TCPC with ECC in 1), 3. Mitral valvuloplasty in 2, artificial (mitral) valve implantation in 1, tricuspid valve closure or valvuloplasty in 3, (tricuspid) valve replacement in 1, common AV valve replacement in 1 pts were performed, 4. In 4 infants BDG was performed after Norwood I. procedure.

RESULTS

Five pts. were lost after BDG procedure (Damous-Kaye-Stansen operation were performed as well in 3 pts.), and another 5 patients' systemic pulmonary shunts were re-done. Four patients after TCPC were lost and reoperation to BDG (n = 1) or shunt procedure (n = 2) was performed in 3 pts. Pre-discharge echocardiography confirmed mitral valvuloplasty with good results. No intervention was necessary in the follow up (1-3 yrs period) due to AV insufficiency and ventricular functions improved.

CONCLUSION

On the basis of our series the "high risk" BDG and TCPC operations can be performed with an encouraging early result. The authors previously contraindicated associated defects can be surgically managed. Our short and mid-term results are feasible in this aspect. The long-term control of the "uni-ventricular" heart's ventricular function needs further investigation.

Application of tissue-engineering principles toward the development of a semilunar heart valve substitute

Heart valve disease is a significant medical problem worldwide. Current treatment for heart valve disease is heart valve replacement. State of the art replacement heart valves are less than ideal and are associated with significant complications. Using the basic principles of tissue engineering, promising alternatives to current replacement heart valves are being developed. Significant progress has been made in the development of a tissue-engineered semilunar heart valve substitute. Advancements include the development of different potential cell sources and cell-seeding techniques; advancements in matrix and scaffold development and in polymer chemistry fabrication; and the development of a variety of bioreactors, which are biomimetic devices used to modulate the development of tissue-engineered neotissue in vitro through the application of biochemical and biomechanical stimuli. This review addresses the need for a tissue-engineered alternative to the current heart valve replacement options. The basics of heart valve structure and function, heart valve disease, and currently available heart valve replacements are discussed. The last 10 years of investigation into a tissue-engineered heart valve as well as current developments are reviewed. Finally, the early clinical applications of cardiovascular tissue engineering are presented.

Measurement and reconstruction of the leaflet geometry for a pericardial artificial heart valve

This paper describes the measurement and reconstruction of the leaflet geometry for a pericardial heart valve. Tasks involved include mapping the leaflet geometries by laser digitizing and reconstructing the 3D freeform leaflet surface based on a laser scanned profile. The challenge is to design a prosthetic valve that maximizes the benefits offered to the recipient as compared to the normally operating naturally-occurring valve. This research was prompted by the fact that artificial heart valve bioprostheses do not provide long life durability comparable to the natural heart valve, together with the anticipated benefits associated with defining the valve geometries, especially the leaflet geometries for the bioprosthetic and human valves, in order to create a replicate valve fabricated from synthetic materials. Our method applies the concept of reverse engineering in order to reconstruct the freeform surface geometry. A Brown & Shape coordinate measuring machine (CMM) equipped with a HyMARC laser-digitizing system was used to measure the leaflet profiles of a Baxter Carpentier-Edwards pericardial heart valve. The computer software, Polyworks was used to pre-process the raw data obtained from the scanning, which included merging images, eliminating duplicate points, and adding interpolated points. Three methods, creating a mesh model from cloud points, creating a freeform surface from cloud points, and generating a freeform surface by B-splines are presented in this paper to reconstruct the freeform leaflet surface. The mesh model created using Polyworks can be used for rapid prototyping and visualization. To fit a freeform surface to cloud points is straightforward but the rendering of a smooth surface is usually unpredictable. A surface fitted by a group of B-splines fitted to cloud points was found to be much smoother. This method offers the possibility of manually adjusting the surface curvature, locally. However, the process is complex and requires additional manipulation. Finally, this paper presents a reverse engineered design for the pericardial heart valve which contains three identical leaflets with reconstructed geometry.