Is There a Role for Mechanical Valved Conduits in the Pulmonary Position?

Mechanical Pulmonary Valve Replacement

Although most valve operations performed annually address lesions of the aortic or mitral valves, the frequency of pulmonary valve replacement (PVR) is increasing because most patients with congenital heart disease are surviving into the adult years. The vast majority of patients, especially children that require PVR, obtain a tissue valve because of the relative good durability and the lack of a need for anticoagulation. Because the need for repeat operation is inevitable for most patients, and the population of adults with congenital heart disease continues to grow, there are increasing situations in which a mechanical pulmonary prosthesis may be appropriate. Most patients being considered for mechanical PVR have a congenital diagnosis and require multi-valve procedures, and quality of life and need for repeat operation(s) are major issues. Mechanical valves are durable but require anticoagulation, which carries its own inherent set of risks. There are conflicting reports regarding the late outcome of mechanical PVR. There are few reports that indicate that, in the pulmonary position, bileaflet valves are at higher risk for complications compared with monodisc valves; however, the majority of these patients were not anticoagulated with warfarin, but simply maintained on aspirin. There is a growing body of literature documenting low rates of thrombosis or pulmonary prosthesis dysfunction when proper anticoagulation and monitoring are applied.

Mid-term outcome of mechanical pulmonary valve prostheses: the importance of anticoagulation

INTRODUCTION

Pulmonary valve replacement (PVR) is being performed more commonly late after the correction of tetralogy of Fallot. Most valves are replaced with an allograft or xenograft, although reoperations are a common theme. Mechanical prostheses have a less favorable reputation due to the necessity of lifelong anticoagulation therapy and higher risk of thrombosis, but they are also less likely to require reoperation. There is a paucity of data on the use of prosthetic valves in the pulmonary position. We report the midterm outcomes of 38 cases of PVR with mechanical prostheses.

METHODS

One hundred twenty two patients who underwent PVR were studied. Thirty-eight patients, mean age 25 ± 8.4 years underwent PVR with mechanical prostheses based on the right ventricular function and the preferences of the patients and physicians. Median age of prosthesis was 1 year (range 3 months to 5 years).

RESULTS

Seven (18%) patients had malfunctioning pulmonary prostheses and two patients underwent redo PVR. Mean International Normalized Ratio (INR) in these seven patients was 2.1±0.8. Fibrinolytic therapy was tried and five of them responded to it well. There was no significant association between the severity of right ventricular dysfunction, patient's age, prostheses valve size and age of the prosthesis in the patients with prosthesis malfunction.

CONCLUSION

PVR with mechanical prostheses can be performed with promising midterm outcomes. Thrombosis on mechanical pulmonary valve prostheses remains a serious complication, but most prosthesis malfunction respond to fibrinolytic therapy, underscoring the need for adequate anticoagulation therapy.

In search of a pediatric cardiac surgeon’s ‘Holy Grail’: the ideal pulmonary conduit

The limited lifespan of all currently available conduits leads to repeat operations and interventional procedures in many children. Each reoperation entails considerable risk to life, expenditure and compromised quality of life as the conduit degenerates. The ideal conduit should be available freely, inexpensive, require no anticoagulation, be resistant to infection, free from thromboembolism, have no gradients or regurgitation and have unlimited durability. This review explores various options as surgeons and researchers endeavor to develop the ideal conduit--which will fulfill all of the above-mentioned criteria. Various currently available conduits are analyzed. Special emphasis is given to tissue-engineered valves and percutaneous valve implantations.

Chronic pulmonary valve insufficiency after repaired Tetralogy of Fallot: diagnostics, reoperations and reconstruction possibilities

Complete correction of Tetralogy of Fallot, the most common cyanotic congenital heart defect, has now become routine. However, late residual lesions, primarily chronic pulmonary valve insufficiency, may have a negative impact on right-ventricular function, leading to the need for reoperation to insert a competent valve at the right-ventricular outflow. The diagnostic modalities pertaining to the failing right ventricle, the timing for eventual reintervention and the various surgical reconstruction possibilities of the right-ventricular outflow tract are still controversial and evolving, and are reviewed with a brief overview on current trends and future outlooks.

Safe surgical strategy for extracardiac conduit replacement in common arterial trunk

Repair of common arterial trunk using an extracardiac right ventricular to pulmonary arterial conduit is the preferred method in most cardiac surgical centres. Reoperation is a fact of life for survivors of common arterial trunk and related cardiac lesions who have undergone such repairs. Long-term survivors may require periodic conduit revisions, with a potentially escalating technical difficulty and risk. Herein we present an analysis of the currently available choices for extracardiac conduits, and outline what we consider to be a safe and reliable surgical strategy for conduit revision.

Bleeding and Thrombotic Emergencies in Pediatric Cardiac Intensive Care

Children in the cardiac intensive care unit (CICU) with congenital or acquired heart disease are at risk for hematologic complications, both hemorrhage and thrombosis. The overall incidence of hematologic complications in the CICU is unknown, but risk factors and target groups have been identified where the essential physiologic balance between bleeding and clotting has been disrupted. Although the best management of life-threatening bleeding and clotting is prevention, the cardiac intensivist is often faced with managing life-threatening hematologic events involving patients from within the unit or those who present from outside. Part I of this review deals with the propensity of children with congenital and acquired heart disease to complications of both bleeding and clotting, and includes discussions of perioperative bleeding, thromboses in single-ventricle patients, clotting of Blalock-Taussig shunts and thrombotic complications of mechanical valves. Part II deals with the subject of stroke in children with heart disease. Part III reviews monitoring the effectiveness of anticoagulation and thrombolysis in the CICU. Currently available diagnostics modalities, medications and management strategies are reviewed and future directions discussed.

Valve replacement in children: a challenge for a whole life

Valvular pathology in infants and children poses numerous challenges to the paediatric cardiac surgeon. Without question, valvular repair is the goal of intervention because restoration of valvular anatomy and physiology using native tissue allows for growth and a potentially better long-term outcome. When reconstruction fails or is not feasible, valve replacement becomes inevitable. Which valve for which position is controversial. Homograft and bioprosthetic valves achieve superior haemodynamic results initially but at the cost of accelerated degeneration. Small patient size and the risk of thromboembolism limit the usefulness of mechanical valves, and somatic outgrowth is an universal problem with all available prostheses. The goal of this article is to address valve replacement options for all four valve positions within the paediatric population. We review current literature and our practice to support our preferences. To summarize, a multitude of opinions and surgical experiences exist. Today, the valve choices that seem without controversy are bioprosthetic replacement of the tricuspid valve and Ross or Ross-Konno procedures when necessary for the aortic valve. On the other hand, bioprostheses may be implanted when annular pulmonary diameter is adequate; if not or in case of right ventricular outflow tract discontinuity, it is better to use a pulmonary homograft with the Ross procedure. Otherwise, a valved conduit. Mitral valve replacement remains the most problematic; the mechanical prosthesis must be placed in the annular position, avoiding oversizing. Future advances with tissue-engineered heart valves for all positions and new anticoagulants may change the landscape for valve replacement in the paediatric population.

Outcomes of mechanical valves in the pulmonic position in patients with congenital heart disease over a 20-year period

BACKGROUND

Homografts or bioprosthetic valves have been preferred in the pulmonic position in patients with congenital heart disease. However, unsatisfactory long-term results have aroused interest in the use of mechanical valves. In this study, we investigated the long-term outcomes of mechanical valves implanted in the pulmonic position.

METHODS

The medical records of 37 patients (27 male, 73%) who underwent 38 mechanical pulmonary valve replacements between October 1988 and February 2011 were reviewed, retrospectively. The median age of patients was 13.5 years (range, 7 months to 23 years), and the median number of prior operations per patient was 2 (range, 0 to 5). Tetralogy of Fallot was the most common diagnosis (n=23). The median valve size was 23 mm (range, 17 to 27 mm), and the median follow-up duration after pulmonary valve replacement was 24.6 months (range, 1.3 months to 22.5 years). Events were defined as the following: valve failure, thrombosis, embolism, bleeding, reoperation, and death.

RESULTS

There was no in-hospital mortality, but there were 2 late deaths (1 heart failure and 1 traffic accident at 10.8 months and 8.7 years postoperatively, respectively). Excluding the traffic accident death, survival rates were 97%, 97%, and 97%, at 1, 5, and 10 years, respectively. Freedom from thromboembolism or bleeding events was 92%, 92%, and 78.8%, at 1, 5 and 10 years, respectively. Two reoperations were performed at 6.8 and 10.2 years postoperatively. Freedom from reoperation was 100%, 100%, and 85.7%, at 1, 5, and 10 years, respectively.

CONCLUSIONS

Durability of mechanical valve in pulmonic position was excellent. Thromboembolism or bleeding events due to anticoagulation therapy were rare. In growing patients who have undergone prior sternotomies requiring a pulmonary valve replacement, a mechanical valve could be an attractive option.

Options for prosthetic pulmonary valve replacement

This article reviews current data on various prostheses utilized for pulmonary valve replacement. Durability data is reviewed and risk factors for deterioration are examined. Finally, the choice of prosthesis should be tailored to the specific clinical scenario based on existing data regarding durability and risk factors.

Long term results of right ventricular outflow tract reconstruction with homografts

Background

Homograft cardiac valves and valved-conduits have been available in our institute since 1992. We sought to determine the long-term outcome after right ventricular outflow tract (RVOT) reconstruction using homografts, and risk factors for reoperation were analyzed.

Materials and Methods

We retrospectively reviewed 112 patients who had undergone repair using 116 homografts between 1992 and 2008. Median age and body weight at operation were 31.2 months and 12.2 kg, respectively. The diagnoses were pulmonary atresia or stenosis with ventricular septal defect (n=93), congenital aortic valve diseases (n=15), and truncus arteriosus (N=8). Mean follow-up duration was 79.2±14.8 months.

Results

There were 10 early and 4 late deaths. Overall survival rate was 89.6%, 88.7%, 86.1% at postoperative 1 year, 5 years and 10 years, respectively. Body weight at operation, cardiopulmonary bypass (CPB) time and aortic cross-clamping (ACC) time were identified as risk factors for death. Forty-three reoperations were performed in thirty-nine patients. Freedom from reoperation was 97.0%, 77.8%, 35.0% at postoperative 1 year, 5 years and 10 years respectively. Small-sized graft was identified as a risk factor for reoperation.

Conclusion

Although long-term survival after RVOT reconstruction with homografts was excellent, freedom from reoperation was unsatisfactory, especially in patients who had small grafts upon initial repair. Thus, alternative surgical strategies not using small grafts may need to be considered in this subset.

Pulmonary insufficiency is the nexus of late complications in tetralogy of Fallot

The number of adults with tetralogy of Fallot now exceeds the number of children with the disorder due to childhood surgical successes. After surgical repair, however, most patients are left with pulmonary regurgitation that, over time, results in right ventricular volume overload, enlargement, and dysfunction. Usually well tolerated for 20 years or more, ongoing pulmonary insufficiency is at the core of late complications that include right ventricular failure, exercise intolerance, atrial and ventricular arrhythmias, and sudden death. Though late pulmonary valve replacement appears to attenuate this risk, prostheses have a finite life span. Thus, the timing of surgery must be carefully considered, weighing the up-front risks of surgery and possible repeat surgery against the risk of ongoing pulmonary regurgitation.

Right ventricular outflow tract reconstruction for pulmonary regurgitation after repair of tetralogy of Fallot. Preliminary results

BACKGROUND

Pulmonary regurgitation after tetralogy of Fallot (ToF) repair is associated with right ventricular dilatation, failure and arrhythmia. Timing and technique for re-intervention remain controversial.

METHODS

Our recent approach is to reconstruct the dilated right ventricle outflow tract (RVOT) as a fibro-muscular sleeve to support a pulmonary homograft valve conduit in orthotopic position. Indication is based on clinical and magnetic resonance (MR) criteria. We reviewed all patients who underwent RVOT reconstruction between January 2004 and February 2005. There were seven children (mean age 14+/-2 years) operated 13+/-2 years after ToF repair, and 12 adults (mean age 30+/-15 years) operated 23+/-10 years after ToF repair. Exercise testing and MR evaluation prior to surgery and at 1 year postoperative follow-up were compared.

RESULTS

There was no operative mortality. At 1 year, pulmonary regurgitation was mild or less in 16/19 patients. Right ventricular (RV) end-diastolic (158+/-51 to 103+/-36ml/m(2), p<0.001) and end-systolic volumes (85+/-42 to 49+/-24ml/m(2), p=0.001) fell significantly. Importantly, effective RV stroke volume (43+/-10 to 48+/-7ml/m(2), p=0.019) and left ventricular (LV) stroke volume (43+/-7 to 47+/-7ml/m(2), p=0.009) increased significantly. The mean RV/LV end-diastolic volume ratio fell markedly in both children and adults (2.22+/-0.62 to 1.38+/-0.52). However, no improvement in maximal VO(2) on exercise was noted in either group.

CONCLUSIONS

RVOT reconstruction restored valve function, improved RV dimensions and left and right stroke volumes. Maximal exercise capacity did not improve in either children or adults.

Percutaneous implantation of the pulmonary and aortic valves: indications and limitations

Percutaneous transcatheter intervention for valvular heart disease is the new horizon in transcatheter therapeutics. Balloon dilatation has been used successfully for treatment of congenital and acquired stenotic lesions of semilunar and atrio-ventricular valves. Although attempts have been made to repair and replace cardiac valves without cardiopulmonary bypass and through percutaneous techniques, this has only recently become a reality. The semilunar valves have preceded atrioventricular valves in successful application in animals and humans. Morphological features play an important role in determining the design of the valve and technique and site of implantation. The major deviations in research and development in artificial or tissue valves have included attempts at delivery of these valves to the site of implantation without open heart surgery. Successful implantation needs long-term follow-up for the durability of the valve and freedom from re-intervention.

When reconstruction fails or is not feasible: valve replacement options in the pediatric population

Valvular pathology in infants and children poses numerous challenges to the pediatric cardiac surgeon. Without question, valvular repair is the goal of intervention because restoration of valvular anatomy and physiology using native tissue allows for growth and a potentially better long-term outcome. When reconstruction fails or is not feasible, valve replacement becomes inevitable. Which valve for which position is controversial. The goal of this article is to address valve replacement options for all four valve positions within the pediatric population. We will draw from our institutional experience and review current literature to support our preferences.