Lateral tunnel versus extracardiac conduit Fontan procedure: a concurrent comparison

In this paper by Kumar et al. (2003, Ann Thorac Surg 76, 1389-1397), the authors compare the outcomes of patients that underwent the Fontan procedure either using the intra-cardiac (lateral tunnel) or extra-cardiac conduit method. I have previously discussed the differences of these two types of the Fontan procedure here. and how the use of each type has changed over time here. In brief, the intra-cardiac or lateral tunnel method is the ‘older’ method (introduced in 1987) and the extra-cardiac method was more recently developed (1990). The lateral tunnel/intra-cardiac method involves sewing a piece of plastic inside the right atrium to route all blood from the lower part of the body (via the inferior vena cava) to the lungs whereas the extra-cardiac method involves placing a tube (either a tissue graft or plastic) outside the heart so that all blood from the lower part of the body (again via inferior vena cava) goes to the lungs. Regardless, some hospitals still perform the intra-cardiac method is the preferred option (see here).

The first thing to point out that this study was published over 10 years ago and uses data from patients that underwent the Fontan procedure from 1995-2002. As I have discussed elsewhere, there have been significant improvements in patient care and outcomes from the Fontan procedure. The other issue that these authors indicate is that most institutions only use one of the types of Fontan or they have suddenly changed over time. As such, it is hard to compare the outcomes of a lateral tunnel vs. extra-cardiac Fontan at a single hospital over the same time period. This study presents data where they performed both lateral tunnel (37 patients) and extra-cardiac (33 patients)  Fontan procedures at the same institution (Medical University of South Carolina) at the same time period.

Summary of Major Points of this Paper:

1) Theoretical advantages of extra-cardiac method. The lateral tunnel or intra-cardiac method requires placing a piece of plastic (“baffle”) inside of the atrium. The lateral tunnel/intra-cardiac method has had good early, medium, and long-term outcomes as well in previous follow-up studies. However, this requires sewing the piece of plastic (Gore Tex) inside the heart, which may increase the risk of atrial arrhythmias. The extra-cardiac method avoids having to sew this piece of plastic inside of the heart and so a theoretical advantage is that this method may decrease risk of future heart rhythm issues. However, note that this generally requires that the surgery be performed later in life because you are placing a piece of plastic in the heart that will not grow with the patient. Another possible advantage of the extra-cardiac method is that it can allow surgeons to perform the procedure without aortic cross-clamping (where they prevent the blood from leaving the heart) and even without cardiopulmonary bypass, which may have some advantages for short- and long-term outcomes (discussed here). For example, in this study, aortic cross clamping was always used for the lateral tunnel/intra-cardiac method but used in ~51% of patients for the extra-cardiac method.

2) No difference in time on cardiopulmonary bypass between intra-cardiac and extra-cardiac method but patients undergoing intra-cardiac method were on aortic cross clamping longer than those using extra-cardiac method. Patients undergoing the lateral tunnel/intra-cardiac method were on bypass (mean = 134 min) nearly the same amount of time as those undergoing the extra-cardiac method (mean = 145 min). However, 100% of patients undergoing the lateral tunnel/intra-cardiac method had aortic cross-clamping and for a longer period of time (mean = 55 min) than those that had the extra-cardiac method (52% of patients, mean = 26 min).

3) No difference in time on ventilator, time in intensive care unit, duration of chest tube drainage, and hospital stay between those having the lateral tunnel/intra-cardiac method vs. those undergoing the extra-cardiac method. This is an interesting result given that the lateral tunnel/intra-cardiac method is theoretically supposed to improve short-term outcome (that soon after the surgery) because of decreased chest tube drainage, etc. However, here they didn’t find any differences between the two methods.

4) No difference in type or frequency of medications given to patients that underwent intra-cardiac vs. extra-cardiac Fontan ~3 years previous. Though this probably attributable to the hospital itself and how they treat their patients, most of the patients were on asprin (94%) and there were no other differences between the type of frequency of medications taken between patients that underwent intra-cardiac or extra-cardiac method ~3 years previous.

5) No difference in heart rhythm problems between patients that had underwent intra-cardiac vs. extra-cardiac Fontan at ~3 years after the surgery. This is somewhat surprising that 15% of patients that had underwent the intra-cardiac Fontan ~3 years previous had heart rhythm issues (sinus node dysfunction) whereas MORE (28%) of patients that had underwent the extra-cardiac Fontan had heart rhythm issues ~3 years previous. Although this is not statistically different, this is opposite than what would be expected. Two patients underwent permanent pacemaker implantation (1 lateral tunnel and 1 extra-cardiac method) and in one case for slow junctional rhythm.

6) No difference in the post-operative blood pressure in various parts of the atrium and in the Fontan pathway (“Fontan pressure” and transpulmonary gradient) between patients that underwent the intra-cardiac vs. extra-cardiac Fontan. The authors provide brief discussion how these pressures can be predictive of early Fontan failure but they found no difference between these two methods in the first 24 hours after the Fontan.

Summary: This study highlights the lack of any real differences between the intra-cardiac/lateral tunnel vs. extra-cardiac Fontan in both the short- and long-term. This study also highlights the low rates of mortality or Fontan takedown (4.3%) around and soon after the actual surgery and high rates of survival 3-5 years after the Fontan for both the intra-cardiac (97%) and extra-cardiac (91%) methods.

The authors discuss their results in light of other studies that were contemporary at the time of this publication (2003). There results are similar to those of Gaynor et al. (2001, J Thorac Cardiovasc Surg 121, 28-41) who reported results from patients undergoing either intra- or extra-cardiac Fontan at Children’s Hospital of Philadelphia (1992-1999) and who again found no real differences between the methods. However, in another previous study that did a similar comparison between patients that underwent the intra-cardiac or extra-cardiac method at the Hospital for Sick Children in Toronto (data from 1994-1998), there was a significantly higher incidence of heart rhythm problems for patients undergoing the lateral tunnel/intra-cardiac method (45%) than those that underwent the extra-cardiac method (15%) at the post-operative period. Why the differences? The authors indicate that it may come from how the Fontan procedure was staged. The second surgery prior to the Fontan is either the hemi-Fontan procedure or the bidirectional Glenn shunt. The authors indicate that they selectively perform the hemi-Fontan for patients that were to undergo the lateral tunnel/intra-cardiac Fontan and perform the bidirectional Glenn shunt for patients that are due to undergo the extra-cardiac Fontan. In contrast, the patients at the hospital in Toronto were all staged with the bidirectional Glenn shunt regardless of whether they were to undergo the intra-cardiac or extra-cardiac Fontan (well, all patients except 1). The authors discuss how the hemi-Fontan (2nd surgery) prior to the lateral tunnel Fontan is a preferred option than doing the bidirectional Glenn shunt prior to the lateral tunnel Fontan (as the surgeons in Toronto did) because the latter involves making incisions in the same area where the previous incisions for the bidirectional Glenn shunt were made. Cutting into the same places where previous incisions were made in the sinus node region is probably not a preferable option. Interesting result. These findings confirm other studies that the risk of heart rhythm issues is higher for patients that underwent the bidirectional Glenn shunt prior to the lateral tunnel/intra-cardiac Fontan than if they had underwent the hemi-Fontan prior to the lateral tunnel/intra-cardiac Fontan. I wonder if all hospitals now always do the hemi-Fontan before the lateral tunnel/intra-cardiac method now?

Finally, the authors discuss how sometimes one method has to be done over another because of other issues with the heart anatomy. In other words, the choice of an intra-cardiac vs. extra-cardiac Fontan is not randomized among patients. For example, the lateral tunnel Fontan is often done for patients with hypoplastic left-heart syndrome but the extra-cardiac method is preferred for patients with heterotaxy syndrome. This makes it difficult to assess whether the short-, medium, or long-term outcomes are a result of the surgical procedure itself (i.e., which Fontan method) or the actual underlying condition.

Link to this paper:

https://www.sciencedirect.com/science/article/pii/S0003497503010105

Intra- or extracardiac Fontan operation? A simple strategy when to do what

In this paper, Kuroczynski et al. (Arch Med Sci 2013) reviewed the records of patients that had undergone intra-cardiac or extra-cardiac Fontan after the bidirectional Glenn surgery (the second one in staged surgeries). It is a relatively small dataset (72 patients) from one institution/hospital in Germany over a number of years (1995-2008) but I think this question is interesting and important. Understanding the potential risks and benefits of both an intra-cardiac or extra-cardiac Fontan is important. We should expect that medical science should improve outcomes and sometimes this requires paradigm shifts. For example, if an institution/hospital only performs intra-cardiac Fontan procedure, if presented with overwhelming evidence that the extra-cardiac route is “better” in the long-term (which this study does not necessarily show!), they should reconsider their methods.

Here are the major points:

As I have discussed before, two routes are commonly used in the Fontan procedure. Remember that the Fontan procedure is the 3rd step for a univentricular heart and generally comes after a 2nd open heart surgery (often the bidirectional Glenn).

1) What is the intra-cardiac Fontan method? The first potential Fontan method is to use the intra-cardiac route (also called ‘lateral tunnel’) where the blood from the lower part of the body (inferior vena cava) is routed directly to the pulmonary arteries through a ‘tunnel’ in  the atrium (generally the right atrium), which involves sewing a patch (‘baffle’) inside the heart. As its name implies (‘intra-cardiac’), this happens inside the heart. One potential caveat of the intra-cardiac Fontan is that it requires aortic cross-clamping (preventing blood from leaving the heart to the rest of the body) and stopping the heart so the surgical procedure can be completed. The intra-cardiac method also typically involves placing a fenestration in the baffle, which I have discussed in other blogs. Here is a diagram of the intra-cardiac method from Khairy et al. (2007, Circulation 115, 800-812):

2) What is the extra-cardiac Fontan method? The extra-cardiac method differs from the intra-cardiac method mostly in that it happens outside of the heart. Outside of the heart, a tunnel made of polytetrafluroethylene (type of plastic also used in non-stick cookware) connects the blood flow from the lower part of the body (again the inferior vena cava) directly to the right pulmonary artery. Here is an image of the extra-cardiac method from the Boston Children’s Hospital

3) Do the extra-cardiac and intra-cardiac methods differ in their short- and long-term outcomes? The authors suggest that the extra-cardiac method has become the method of choice more recently because i) improved blood flow, ii) less risk of thrombosis (blood clots), iii) lower chance of heart rhythm problems in the short- and long-term, iv) surgically speaking, it is easier and requires less aortic clamping, which may be advantageous (see my other posts). However, this is actually narrow view and, while the extra-cardiac method is preferred at some pediatric cardiology hospitals, the intra-cardiac method is preferred at others. Furthermore, this is definitely not all pediatric cardiologists agree that the extra-cardiac method is preferred over the intra-cardiac method based upon follow-up studies such as this one (Khairy et al., 2012 Circulation 126, 2516-2525).

4) What do the data show presented in this study? Although the sample sizes were extremely small (e.g., for patients with tricuspid atresia, they performed 9 intra-cardiac Fontan and 10 extra-cardiac Fontan), the results are still interesting. However, keep these small sample sizes in mind as well as the fact that these data were collected from 1995-2008 and the type and level of treatment has likely improved for patients undergoing the Fontan procedure over that time period.

5) Patients undergoing the intra-cardiac method spend MORE time on cardiopulmonary bypass than patients undergoing the extra-cardiac method. The amount of time spent on cardiopulmonary bypass for the intra-cardiac Fontan was greater (median = 170 min, range = 50-399 min) than the extra-cardiac Fontan (median 104 min, range = 53-247 min). Most studies (including this one) generally show that spending more time on bypass is not good in the short- and long-term. However, it is again hard to identify cause and effect here given that patients with more complex heart defects will necessarily spend more time on bypass.

6) Patients undergoing the intra-cardiac method (median = 39 hours) spend MORE time on a ventilator after the Fontan procedure than patients undergoing the extra-cardiac method (median = 21 hours). These numbers (the median # of hours spent on ventilator) seem crazy high. A predictor of the length of time spent on the ventilator was the amount of time with aorta cross-clamped (which might reflect a more complicated surgical procedure so not surprising longer time on ventilator). Age and weight at which the Fontan was performed did not impact amount of time on ventilator.

7) Patients undergoing the intra-cardiac method (median = 19.5 days) spent MORE time in the intensive care unit recovering from the Fontan than patients undergoing the extra-cardiac method (median = 14 days). Again, it would be important to know how these values changed over the years as this may have gone down from what it was in the mid 1990’s. Age and weight at which the Fontan was performed did not impact amount of time in intensive care unit.

8) Patients undergoing the intra-cardiac method (median = 48 hours) had to receive greater inotropic support with catecholamines (basically how long they received drugs like dopamine to help their heart beat properly) than patients undergoing the extra-cardiac method (median = 10 hours).

Summary: Taken together, this study shows that there were major advantages for performing the extra-cardiac method over the intra-cardiac method. Patients that underwent the intra-cardiac method spent MORE time i) on cardiopulmonary bypass, ii) on a ventilator, iii) on drugs that helped heart contract, iv) in the intensive care unit. All of this is interesting but it doesn’t prove that intra-cardiac method is worse than extra-cardiac method as this is one study with a small sample size of patients from one institution over a long period of time where how patients needing the Fontan procedure are treated has changed.

Caveats: Why the authors did not report presence/absence of heart rhythm problems is unknown but would have been interesting. Although they found that age and weight at Fontan completion didn’t affect the outcomes, the authors also discuss that they prefer to do the Fontan at a later age (median patient age of Fontan completion was 3.2 years in this study). Using the extra-cardiac method generally requires patients to be older so that changing the length of the conduit (extra-cardiac tunnel) can be avoided as the patient gets older and grows. However, this has to be balanced with the fact that performing the Fontan at a later age can damage the normal ventricle (Mair et al., 2001).

Link to this paper:http://www.termedia.pl/Clinical-research-Intra-or-extracardiac-Fontan-operation-A-simple-strategy-when-to-do-what,19,20334,0,1.html

18 years of the Fontan operation at a single institution

In this study by Dr. Lindsay S. Rogers et al. (2012, Journal of the American College of Cardiology 60, 1018-1025), the authors report their experiences of performing the Fontan operation (palliation) on 771 patients from 1992-2009 at the Children’s Hospital of Philadelphia. The authors recorded a variety of variables about the patient (demographic and anatomical) and the actual surgical procedure (e.g, time on cardiopulmonary bypass, amount of drainage from the pleural – chest – tubes, length of stay, readmission to the hospital following the procedure) and report their findings here.

The interesting part of this study is that they split their analysis into 3 different ‘eras’. Era 1 were Fontan operations performed from 1992-1997 (6 years), Era 2 was 1998-2002 (5 years), and Era 3 was 2003-2009 (7 years). This is important because how patients with a congenital heart defect born in 1992-1993 that had the Fontan procedure may have been treated much differently than those born in 2007-2008 that exhibited the same defect and had the same Fontan procedure. Obviously we hope that science and medical research in general should advance how we treat human diseases and how we perform operations and so it is predicted that outcomes for those born in Era 3 (2003-2009) that had the Fontan procedure may have higher survival rates than those born in Era 1 (1992-1997). This study highlights the shift in treating children with congenital heart defects among these three eras. For example, as the authors indicate, Era 1 (1992-1997) represents a time period when most children were treated with the lateral tunnel type of Fontan (see #1 below for an introduction to this point) , during Era 2 (1998-2002), there was a shift towards using the extra-cardiac conduit method (but still relatively equal number of both method) and routine use of the “modified ultrafiltration” method of cardiopulmonary bypass (see link below) started during this Era 2 (in 1996), and in Era 3 most Fontan operations were performed using the extra-cardiac conduit method (though note that this differs from other hospitals such as C.S. Mott Children’s Hospital – see below). Again, this study highlights the importance of allowing researchers to use such data gathered from children having the Fontan procedure as it allows these types of analyses.

Here are the major findings or those that I find interesting:

1) As Fig. 1 indicates, the number of Fontan procedures performed per year at this hospital ranges from 25-70, not terribly high and somewhat surprising to me. It also shows how the type of Fontan performed has changed dramatically across these years. In Era 1 (1992-1997), most Fontan procedures had the lateral tunnel method whereas in the modern era (2003-2009), most Fontan procedures used the extra-cardiac conduit method. From what I understand, the lateral tunnel method is older (well, introduced in 1987) than the extra-cardiac conduit method (introduced in 1990). The lateral tunnel (LT) procedure involves placing a ‘baffle’ (piece of Gore-tex) inside the atrium. One predicted risk of the LT procedure is an increased chance of developing heart rhythm problems, which might not be surprising given that you are sewing something inside of the atrium. The LT procedure is still used by many major hospitals (e.g., at C.S. Mott Children’s Hospital at the University of Michigan, 92% of Fontan procedures performed from 1992-2007 used the LT method: Hirsch et al. 2008, Annals of Surgery 248, 402-410). The extra-cardiac conduit (literally outside the heart tunnel…) or ECC method basically does not involve sewing this baffle into the atrium and is theoretically associated with decreased postoperative complications. This topic (lateral tunnel vs. ECC) should clearly be a focus of a future blog post as I have a major interest in this area. Moving on…

2) From Era 1 (1992-1997), the median age at Fontan was 2.3 years, whereas it was 2.8 years in Era 3 (2003-2009). This is somewhat surprising given our personal experiences that the age of Fontan has been steadily decreasing over the years. Also, as these authors show, the age at stage 2 surgery (e.g., “hemi-Fontan”) decreased from Era 1 (6.4 months) to Era 3 (5.9 months). It would be interesting to conduct a more fine-grained analysis where we look at how differences in age at Fontan affect other parameters (e.g., do children that have Fontan at 18 months have a different outcome than those at 36 months?). As far as I can tell, most studies that have looked at this break the data up into larger chunks (e.g., Fontan performed >3 years or ❤ years as in Shiraishi et al. (2009, Annals Thoracic Surgery 87, 555-561). In this study by Shiraishi et al. (2009), they found that patients with dominant left ventricle (e.g., having Tricuspid atresia or a very small/reduced right ventricle) that had the Fontan procedure performed before 3 years of age had a higher cardiac index (basically heart performance corrected for variation in body size) at 5 and 10 years after operation and higher peak oxygen consumption (might view this as exercise capacity).

On the other hand, this increase in age at Fontan from Era 1 to Era 3 is likely due to the observation that body weight at the time of the Fontan procedure is a predictor of short- and long-term outcomes. Indeed, weight at Fontan from Era 1 (12 pounds) has increased to Era 3 (12.9 pounds).

3) Perhaps the most important part of this paper is the “outcomes” section. The good news is that only 3.5% of the patients that underwent the Fontan procedure died from 1992-2009 (27/771) and the probability of death of the individual <30 days after the Fontan procedure has declined significantly from Era 1 (9.3% died) to Era 3 (1.2%), though there hasn’t been any improvement in increasing survival <30 days after the Fontan from Era 2 (1.0%) to Era 3 (1.2%).

4) More good news is that duration in the ICU, total time in the hospital, and the frequency of lengthy (>14 days)  pleural effusions (drainage from the chest tubes) has declined from Era 1 to Era 3. Though the average i) ICU duration (2-3 days across Era 1 to Era 3) has not changed from 1992-2009, the variation has changed such that were fewer lengthy stays in the ICU in Era 3 (range of stay was 1-45 days) compared to Era 1 (0-181 days). Similarly, the duration of chest tube drainage in Era 1 (mean was 3 days) was similar to Era 3 (4 days) but again the frequency of chest tube drainage that lasted >14 dyas has declined from Era 1 (28.6%) to Era (17.5%). Moreover, the length of hospital stay has declined from Era 1 (12 days) to Era 3 (8 days) and the frequency of lengthy hospital stays (>14 days) after the Fontan has declined from Era 1 (46.7% of Fontan procedures performed here involved patients staying >14 days after procedure) compared to Era 3 (19.5% patients stayed >14 days after Fontan).

5) The final and important part of this paper is indicating the risk factors that predicted whether patients that had the Fontan procedure died, had lengthy hospital stays or chest tube drainage after the Fontan. For death or Fontan takedown within 30 days of the Fontan procedure, those patients that had longer times on deep hypothermic circulatory arrest had an increased probability of dying or Fontan takedown. However, the use of modified ultrafiltration during cardiopulmonary bypass has decreased the risk of death or Fontan takedown, which again is good news and evidence that progress in surgical techniques has benefited patients having the Fontan procedure performed in the modern era. This also highlights the importance of asking your surgeon or their support team how long your child was on cardiopulmonary bypass as it provides some potentially useful information about the future or risks for the future. Also of note, whether patients had the i) lateral tunnel or extra-cardiac conduit method of the Fontan and ii) whether fenestration was or was not used did not affect the risk of death or Fontan takedown within 30 days of the Fontan, though this is again only 30 days after the Fontan and we need to know more about the long-term outcomes of these different procedures.

6) Because the authors found that those patients with longer support times (basically longer cardiopulmonary bypass time) had longer hospital stays and longer periods of chest tube drainage after the Fontan, they also investigated what factors of the patient affected total support time. They found that patients that were larger at the Fontan had longer total support times and that those patients that had the extra-cardiac conduit method also had longer total support times. These are interesting results when comparing the benefits and costs of the lateral tunnel vs. extra-cardiac conduit method as well as the age (and weight) at which to perform the Fontan procedure. However, the longer total support time and the longer time on deep hypothermic circulatory arrest (see above) likely just reflect that the surgery was more complicated because of a complex heart defect. The authors do indicate that their results suggest that the extra-cardiac conduit method is associated with greater short-term complications (longer chest tube drainage and hospital stay duration because of longer total support time) but the preferential use of this procedure over the lateral tunnel method is because it is thought to lower the risk of long-term complications (heart rhythm problems associated with lateral tunnel methods). Yet, we need to see those data showing a reduction in heart rhythm problems in order to justify the conclusion that the extra-cardiac conduit method has long-term benefits compared to the lateral tunnel method!

7) The final and interesting point of this paper is found in Table 9, which summarizes the post-operative outcomes from several similar studies using data collected from several hospitals that commonly perform these procedures (e.g., Children’s Hospital of Philadelphia, C.S. Mott Children’s Hospital at the University of Michigan, Children’s Mercy Hospitals and Clinics in Kansas City, Children’s Hospital of Wisconsin, Children’s Hospital in Boston,  etc.). What is interesting here is that you might make some comparisons among the different studies (and really hospitals) for mortality rates, hospital stay times, bypass times, etc. Though I will resist making comparisons here because really it isn’t good science to make comparisons when the hospitals and surgeons take in different numbers of patients (some do more than others) and take in patients with varying degrees of difficulty (who may have higher mortality rates). For example, at the Children’s Mercy Hospitals and Clinics in Kansas City, surgeons performed 145 Fontan procedures (all nonfenestrated, extra-cardiac conduit method) from 1997-2008 and 5.5% of those patients died and 2.8% of those patients had Fontan takedown. In contrast, at Children’s Hospital of Wisconsin in Milwaukee, surgeons performed 256 Fontan procedures (fenestration used selectively) from 1994-2007, 2.0% of those patients died and 0.8% of those patients had Fontan takedown. These differences may or may not be statistically different from one another and we do not know if the degree of complexity of the defects treated at the two hospitals differ from one another.

Link to this paper:

http://dx.doi.org/10.1016/j.jacc.2012.05.010

Link to information about Modified Ultrafiltration during cardiopulmonary bypass:

http://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v04/040064r00.htm