Fontan Conversion/Arrhythmia Surgery Long-term Database

Doctor's Name: 
Constantine Mavroudis, MD
Cleveland Clinic Foundation

Each year thousands of babies born in the United States have a severe form of congenital heart malformation referred to as “functionally univentricular heart.” In truth, this term is applied to a rather broad spectrum of congenital heart defects which have as their common feature the lack of two normal, well-developed ventricles or pumping chambers – one to send blue blood to the lungs, and one to send red oxygenated blood to the body.  When only one pumping chamber has to perform both jobs, life expectancy is severely limited. For some of these heart malformations, such as hypoplastic left heart syndrome, death is a virtual certainty without surgery within the first days of life. Other forms of univentricular heart, or “single ventricle”  can be associated with survival without heart surgery for months or years, but invariably with cyanosis (blueness due to poor oxygen content in the blood) and very abnormal quality of life.


Several decades ago, pioneer surgeons developed operations to make the univentricular circulation function more like the normal circulation – all the blue blood going to the lungs, and then all the red oxygenated blood going to the body, including the heart  and brain and other vital organs. But the key feature of these operations, named Fontan operations after one of the pioneer surgeons, is that the single ventricle propels the flow of blood to the body, but the flow of blood to the lungs is passive – it has to occur without the assistance of a dedicated pumping chamber. Operations of this type have evolved through numerous modifications, to the point where today they can be done with a high rate of success for virtually all of the congenital heart malformations in that large category of functionally univentricular heart - including the most severe and challenging ones. This has given the hope of survival and reasonable quality of life to literally tens of thousands of patients in the US and around the world.


Unfortunately, with more and more patients surviving Fontan operations, it started to become evident that the satisfactory condition of patients after successful Fontan operations was not necessarily a permanent or even a long-term outcome for many. While some continued to be active and enjoy good health for decades, many began to experience worsening clinical status over time. Sometimes the progression of symptoms was subtle; sometimes severe and abrupt. Several theories were entertained to explain this. One was the pessimistic view that the “Fontan state” itself was a circulatory condition that was inevitably destined to be associated with declining function, deteriorating health, and premature death. But the generally satisfactory status of some of the the patients over many years – even several decades, seemed to challenge this idea. Another theory was that the type of “cardiovascular plumbing” that resulted from the particular ways that Fontan operations were done years ago is inherently inefficient in respects that could be addressed by newer more streamlined surgical pathways for the Fontan circulation. Beginning nearly twenty years ago, surgeons attempted to interrupt or reverse the declining status of some Fontan patients by “converting” them to the more modern, more bioenergetically efficient pathways. In some instances, this was very successful. But one feature of the declining state of many Fontan patients – the recurrent or constant occurrence of atrial tachyarrhythmias (rapid or chaotic heart rhythms) did not appear to improve with these conversion surgeries, and sometimes prevented successful outcomes. The team of cardiologists and surgeons at Childrens Memorial Hospital in Chicago, led by cardiac surgeon Constantine Mavroudis (now at Cleveland Clinic), developed a procedure known as Fontan conversion with surgical arrhythmia circuit ablation. The process involved both the conversion of the Fontan pathway to a more efficient type of “plumbing,” and the freezing or cutting of numerous specific lines and sites within the heart to eliminate or interrupt the electrical circuitry through the heart tissue that allowed the arrhythmias to occur.


As time has gone on, it has become clear that even patients with the more modern types of Fontan surgery are at risk for deteriorating health status as they approach adulthood, or even later as young adults who had been leading active, productive lives. Also clear is the fact that atrial arrhythmias are a feature of the complex medical challenge for most of these patients. Fontan conversion and surgical arrhythmia circuit ablation is increasingly being done in these circumstances as well. And while it is a complex and difficult undertaking, the vast majority of these patients survive surgery, and most have enjoyed improved status with control of arrhythmias – at least during short-term follow up and over the first several years after surgery.


So, we’ve reached a point where we need to find out  -  is the enormous potential benefit of the Fontan principle a hollow promise? Is declining status of patients with single ventricle repairs an inevitable and irreversible outcome of a failed approach? Has all of the hope and effort of treating single ventricle patients merely postponed the inevitable? Are those who are most pessimistic ultimately correct? Or can timely interventions such as Fontan conversion with surgical arrhythmia circuit ablation restore functional capacity to the single ventricle circulation in a way that is durable and results in functional status that not only improves but remains satisfactory? We believe this to be true, but realize the need for objective evidence. For the ever increasing number of patients receiving the Fontan type repairs, it is critical to assess novel strategies and interventions that may have the potential to restore or prolong acceptable physiologic status and functional capacity.  The development of a longitudinal database of patients treated by Fontan conversion with surgical arrhythmia circuit ablation is an important means of capturing all of the information that will be essential to answering these questions and determining the optimal timing and appropriate circumstances under which to undertake this promising, complex form of therapy.

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