Fontan conversion for Fontan failure: lessons from a vanishing craft

Introduced by Fontan and Kreutzer 50 years ago, the unique impact of the Fontan operation cannot be overstated, offering a true perspective for children born with complex univentricular heart malformations, priorly burdened with dismal prognosis, to survive into adulthood. However, as already realized by Fontan himself, the procedure is of a palliative character only and increasingly available long-term data painfully clearly point out the intrinsic limitations of this unnatural circulation [1]. In the absence of a subpulmonary ventricle, the Fontan circulation pathophysiology unavoidably results in venous congestion and reduced ventricular preload with a chronic low output state. The continuous attrition of Fontan haemodynamics may elicit countless long-term complications and co-morbidities and likely inevitably results in irreversible circulatory failure and premature death or the requirement of cardiac transplantation. Once decompensating, therapeutic options to treat Fontan circulation failure in patients without interventionally or surgically addressable haemodynamic issues are severely limited. Conventional medical heart failure treatment has little proven efficacy. It is therefore a general conception that identifyable haemodynamic restrictions in a Fontan circulation with signs of failure, in fact better yet way before the onset of such signs, shall be addressed. Such optimizations may, at least temporarily, reverse circulatory failure. Hence, Fontan patients undergo a considerable number of reinterventions and re-operations, which have to be regarded as necessary maintenance work to keep the imperfect circulation the least imperfect possible [2]. Older Fontan modifications such as the atriopulmonary connection have proven to be particularly haemodynamically disadvantageous. As already de Leval et al.[3] pointed out when introducing their concept of a total cavopulmonary connection Fontan with a lateral tunnel, the atriopulmonary connection results in significant energy loss of the passive blood flow directed towards the pulmonary arteries. The well-described sequelae of atrial dilatation and atrial dysrhythmias accelerate the haemodynamic demise. Pioneered by Mavroudis et al. [4], the concept of Fontan coversion from an atriopulmonary modification to an extracardiac conduit with concomitant atrial arrhythmia surgery and cardiac pacemaker implantation was consequentially introduced. In their present study, Padalino et al. [5] summarize their results of surgical interventions for the treatment of failing Fontan circulation, with the majority of procedures being Fontan conversions. Their early and midterm results of Fontan conversion are good, there were a total of 3 early deaths (14% mortality) from the early era but no early mortality during the last 20 years of their experience. Overall mid-term survival was also good with 5- and 10-year survival estimates after Fontan conversion of ∼85% and 75%, respectively. These results may not quite compare to the exceptional results reported by Mavroudis and Deal [6], who have undisputably mastered the craft of Fontan conversion, but are well comparable to those described by various centres. However, the atriopulmonary connection Fontan modifications have largely been abandoned for decades now, for their obvious disadvantages. Patients with these modifications are considerably old and their numbers are constantly declining by either conversion, cardiac transplantation or death. Therefore, sometime very soon, these modifications will have disappeared entirely, rendering the Fontan conversion procedure a dying craft. Then, what is there to learn from Padalino’s and other author’s studies for the contemporary, ever growing cohort of Fontan patients that will not be able to be treated with conversion upon eventual circulatory Fontan failure? One of the critical points may indeed be timing. The patients in Padalino’s study were fairly young and were not in excessive heart failure with two-third of the patients corresponding to NYHA functional class II. Overall, they were likely comparably ‘well’ failing Fontan patients. This might represent a crucial factor for success of any major surgical intervention in these patients. The longer failing Fontan patients remain in a state of insufficient haemodynamics, the more secondary organ dysfunctions will progress and the risks for surgical interventions such as Fontan conversion but, importantly, also for the ultima ratio option cardiac transplantation, will considerably increase. As intuitive and trivial this may seem, previously stated innumerable times, unfortunately little progress has been made to characterize the optimal time points of necessary interventions. For surgical procedures such as Fontan conversion it might be argued to perform them as early as possible at the onset of Fontan failure or even preemptively, since patients will initially remain with Fontan haemodynamics. However, conversion will not be an option for contemporary Fontan patients that will develop failure and the matter is more complicated for intended primary cardiac transplantation. Transplantability of patients, limited availability of allocatable organs and expected waiting times as well as limited longivety of transplants among other factors will have to be taken into considerations. Reported mortality rates on the transplantation waitlist of up to 28% and early mortality after transplantation of up to 20% are worrisome and suggest that patients with late Fontan failure in general might rather be listed way too late [7, 8]. Other centres on the other hand have reported an incredibly low early mortality of 0% after cardiac transplantation and combined cardiac and liver transplantation in adult failing Fontan patients [9]. This clearly emphasizes that there is a large potential for improvement in the treatment of Fontan patients transitioning to their ‘fourth stage palliation’. It must be kept in mind that the Fontan circulation is a man-made state of variably but steadily progressing chronic heart failure. For the time being, if medical heart failure therapy is exhausted, mechanical circulatory support as well as cardiac transplantation are the only meaningful therapeutic options for end-stage heart failure. However, for failing Fontan patients, there are numerous unanswered questions and an obvious need for a collaborative effort to identify effective medical treatment strategies, define validated evaluation and listing criteria to improve transplantation outcomes but, importantly, also to explore the possibilities of reproducibly successful mechanical circulatory support as a bridge to transplantability or even as destination therapy. The problem is urging as the global Fontan population ages and increases in numbers. Only multiinstitutional, multinational collaboration and collective data will provide an adequate basis to address these issues. Initiatives like the recently founded International Fontan Interest Group provide some much-needed optimism [10].