Commentary: A 3-minute foray into the futureThe year is 2050. Freddy Jones is about to undergo a Fontan operation. Freddy is an unusual patient. Most blastocysts are genetically screened for hypoplastic left heart syndrome, and if detected, a developing patient undergoes either embryological epigenetic modification or fetal intervention, preventing or eliminating the disorder. These techniques are still not globally available, so Freddy was not screened. Thus, Freddy is managed with the older, 3-stage palliation. In preparation for the Fontan, Freddy undergoes cardiac magnetic resonance imaging with complete pressure mapping (diagnostic catheterization became obsolete by 2030).
Commentary: Man versus machine: Whose side are you on?Go is an ancient Chinese board game that is played today exactly as it was more than 3000 years ago.1 It is a game with simple rules, in which 2 players take turns putting black and white stones onto a flat piece of wood on which a grid is printed. To win, a player captures or surrounds more territories than the opponent. Despite its simplicity, Go is far more complex than chess, with possible moves and legal positions estimated to be greater than the number of atoms in the known universe. Go is a game more of intuition than anticipation or calculation.
Commentary: Yet another Fontan computational study—but this one has clayWhat does clay have to do with computational flow dynamics (CFD) and the personalized Fontan (herein referred to as the TCPC)? Loke and colleagues' response1 is that a surgeon-fashioned clay TCPC actually performed reasonably well and could reduce the computational time and money by serving as starting input for the CFD iterative process. With the availability of surgical modeling software, we don't fully understand the need for clay and haptic feedback but, must admit, find the use of clay kind of appealing—can't explain it, maybe it invokes pleasant childhood memories.
Commentary: I don't like changeOkay, I will admit that I do not like to change. It is difficult to see that what you have done for years may not be the right way and then head in a different direction, whether with respect to medical treatment of a particular nature, in a relationship, or in practicing surgery for congenital heart disease. I think this is particularly true for surgical techniques, where there are very few randomized studies proving that one technique is better than another (actually, that's also true for relationships).
Management of the bad atrioventricular valve in Fontan…time for a changeSuccessful long-term outcome following Fontan procedure depends on numerous factors, including normal ventricular systolic and diastolic function, adequate pulmonary artery size and distribution, low pulmonary artery pressures and resistance, sinus rhythm, and a competent atrioventricular valve.
Commentary: Promise of personalized tissue-engineered vascular grafts for congenital heart surgeryVascular grafts and, more commonly, patches are commonly used in the repair of congenital heart defects. Non-autologous, circumferential vascular grafts have key shortcomings, such as the lack of growth potential and need for anticoagulation, that prohibit their universal adoption.1 Another shortcoming of grafts and patches is that tailoring of their shape and size before implantation is according to the surgeon's eye or crude measurements in 1 or 2 dimensions. Although this tailoring may be satisfactory for simple geometries, achieving the most efficient hemodynamic result for complex pathways and baffles in growing children is sometimes difficult, and the development of late obstruction may necessitate reoperation.
Commentary: Something made from nothing—impressive, but will it last?I congratulate Yeung and colleagues1 for their development of an elegant, sophisticated, and innovative technology and also commend their collaboration across multiple disciplines and institutions. The basic concept they promote is intuitively very appealing—use patient-specific anatomy, guided by computational fluid dynamics, to develop 3-dimensional (3D) vascular grafts tailored to a given patient's specific needs—in this particular case, the creation of bifurcated pulmonary artery grafts. The reader should look beyond the fact that both animals originally had normal anatomy, as I presume the computer-aided design phase would permit creation of any desired anatomy (for missing parts), which could then be modified to fit the patient's true anatomy.
Commentary: Why use the Y-graft?The Fontan procedure represents the last stage of surgical palliation for functional single-ventricle defects. As a staged operation in the current era, the Fontan procedure creates a pathway that directs inferior vena cava (IVC) blood flow into the lungs via the branch pulmonary arteries. Over time, a number of modifications of the Fontan procedure have been made, including an atriopulmonary connection, intra-atrial lateral tunnel, extracardiac conduit, and extracardiac Y-graft.
Commentary: Moderate atrioventricular valve regurgitation may be too much to bear for a single ventricleIn their editorial review in this issue of the Journal, Stephens and Dearani1 comment on the results of our retrospective series2 that assessed the incidence and impact of atrioventricular regurgitation in patients who had survived the Fontan operation. In our experience, more than half of the common atrioventricular valves and tricuspid valves were regurgitant or necessitated intervention before patients reached the age of 25 years (Figure 1).2 The existence of even moderate regurgitation was enough to more than double a patient's risk of circulatory failure, which for most meant death or transplantation.
Commentary: Cavopulmonary assist: Closing in on the white whale of single-ventricle palliationImproving the long-term survival and quality of life for patients with single-ventricle heart disease remains the single greatest unmet need in pediatric heart surgery and pediatric cardiology. Although the surgical outcomes of single-ventricle palliation have been celebrated and have steadily improved over time, the unsightly truth is that the Fontan circulation is a grossly abnormal circulatory configuration, which leads to a myriad of progressive, debilitating, and ultimately fatal medical problems that accumulate over time.
Commentary: Why the Y-graft?Long-term outcomes after the Fontan operation for single-ventricle lesions remain suboptimal, with many patients having complications related to resistance through the Fontan circuit or maldistribution of hepatic blood flow between the lungs. These mechanisms of Fontan failure have persisted through various iterations of Fontan anatomy that have been developed during the almost 5 decades since the first successful atriopulmonary connection in 1971. A recent modification to the Fontan operation is the use of a bifurcated Y-graft to complete the inferior cavopulmonary connection.
Commentary: The future fourth stage of single-ventricle palliationFive decades after Francis Fontan first described his procedure for palliation of tricuspid atresia, modified versions have enabled long-term survival of a broad array of patients with univentricular circulation.1 It has long been recognized, however, that the sequelae of the total cavopulmonary connection—including systemic venous congestion, hepatic dysfunction, renal insufficiency, changes in pulmonary vascular physiology, and elevated systemic afterload—result in long-term failure of even the “perfect” Fontan circulation.
Commentary: Engineering an optimal mechanical circulatory support system for the cavopulmonary connectionLong-term survival of the patients with a functional single-ventricle physiology has dramatically improved with the establishment of staged surgical palliation and subsequent Fontan operation. As the number of the patients who live with a Fontan circulation has been increasing exponentially, management of the failing Fontan circulation becomes one of the most critical issues in pediatric and adult congenital heart disease care. Dr Trusty and colleagues1 reported an in vitro analysis of the mechanical circulatory support (MCS) system for failing Fontan circulation using a PediMag (Thoratec Corp, Pleasanton, Calif) or CentriMag (Thoratec Corp) centrifugal pump.
Commentary: Fontan assist device support: Road map to “stage 4” palliationThe “un-natural” history of the Fontan circulation portends a rather grim long-term outlook for patients with single ventricle congenital heart disease. Decades of experience with the Fontan circulation have shown the advantages of the total cavopulmonary connection that minimizes power loss to improve subpulmonary flow efficiency; yet, the altered hemodynamics impart a chronic attrition to the organ systems of the body leading to a range of complications and limited life expectancy for this patient cohort.
Commentary: Subpulmonary pump in Fontan circulation: Can it be a breakthrough in treatment of the single ventricle?It has been almost half a century since the first successful report of Fontan surgery.1 Without any doubt, this was one of the major breakthroughs in the history of cardiac surgery and brought a ray of light to a previously unrepairable and lethal heart condition. However, long-term survival after the Fontan operation is still far from satisfactory.2 Efforts to improve survival to date have focused on optimization of the design of the Fontan circuit per se to make the best use of the single energy source from the single ventricle.
Commentary: Dream big in every small stepThe last stage of surgical single-ventricle palliation has undergone ingenious modifications since its first description.1 The achievement of a higher arterial saturation level by the separation of the venous backflow from the systemic circulation at the cost of a passive, nonpulsatile pulmonary blood supply and higher systemic venous pressure has led to the initially successful but challenging Fontan physiology in the longer follow-up.2,3 By consideration of various etiologies for an ultimately failing Fontan circulation, the search for the optimal fourth stage palliation strategy continues, with remarkable future potential.
Another step toward intelligent surgical planningThe applications of computational fluid dynamics (CFD) to cardiovascular medicine and surgery just keep getting better. Trusty and colleagues1 examine a way that CFD could be used to plan “complex” Fontan operations. These patients are those whose anatomy does not “guarantee” a relatively even distribution of hepatic blood flow (HBF) to both lungs with a conventional extracardiac conduit or lateral tunnel. The typical example would be an interrupted inferior vena cava with azygous continuation to a left superior vena cava and a right-sided hepatic veins-to-right pulmonary artery conduit.
Aortic arch reconstruction in the Norwood operation: It is more than just geometryMuch attention has been given to the reconstructed aortic arch anatomy in the Norwood operation with regard to hypoplastic left heart syndrome (HLHS) outcomes. Having the arch too big, leaving or residual obstruction or having it develop, and using patch material have all been implicated in poor results after the Norwood procedure. Knowing that the right ventricle may struggle as the systemic ventricle long-term, more data are being sought with regard to the abnormal afterload imposed on the right ventricle by a reconstructed aortic arch.
Francis Fontan memorial 1929-2018Francis Fontan was born in Nay, in the province of Bearn in France. His father, Victor, was a noted professional cyclist and achieved fame as the “King of Mountains” in the Tour de France.
Still young at heart…Surgical palliation for single-ventricle (SV) physiology has continued to improve over the last 40 years. Since the original description of the Fontan operation for tricuspid atresia in 1971,1 the procedure has undergone several modifications and is now used to palliate a wide range of SV defects. Most patients with SV lesions require some form of neonatal palliation to ensure unrestricted systemic and pulmonary blood flow and free mixing of blood within the heart. Invariably, first-stage palliation results in a volume-loaded ventricle, as pulmonary resistance decrease with age.
Cause versus effect? Tricuspid valve replacement in the management of a failing Fontan circulationManagement of single-ventricle physiology after completion Fontan continues to produce improved outcomes and transplant-free quality of life metrics. Single-ventricle survivorship clinics and other focused care delivery models within congenital heart programs provide multidisciplinary care across all medical components of need for these complex patients.1 Despite these advances, however, transplantation remains a common end pathway for these palliated patients. Creation of a medical and social environment that is best for patients to prepare for this “final” surgical stage confounds even the most advanced institutions.
Fontan-associated liver disease: Is it all about hemodynamics?The study by Trusty et al,1 in this issue of The Journal of Thoracic and Cardiovascular Surgery, aims at investigating detailed cardiac magnetic resonance (CMR)-derived flow dynamics and total cavopulmonary connection (TCPC) energetics as potential risk factors for hepatic fibrosis in Fontan patients. Fontan-associated liver disease (FALD) has been a well documented complication for decades2 and is now recognized as a progressive process affecting all Fontan survivors. The exact causes and risk factors of FALD remain poorly understood.
Cow neck veins and endocarditis: A mooo…ving mysterySurgeons loathe endocarditis—it kills patients and causes morbidity. Moreover, nothing puts a damper on a surgeon's day like a multiple redo sternotomy and inadvertent rupture of an endocarditic conduit. Therefore, the report by Beckerman and colleagues1 of increased risk of infective endocarditis (IE) with bovine jugular vein (BJV) conduits (Medtronic Inc, Minneapolis, Minn), which is a notable addition to the growing literature on this topic, is certainly concerning. At a median follow-up of 7.5 years, IE occurred in 10% of 253 BJV conduits, 0.8% of 506 homografts, and 1.9% of 269 porcine heterografts.