Discussion| Volume 157, ISSUE 6, P2396-2398, June 2019


    Open ArchivePublished:April 03, 2019DOI:
        Dr Thomas L. Spray (Philadelphia, Pa). These authors have collected extensive preoperative, intraoperative, and postoperative data on 216 neonates and infants with truncus over a 7-year period at 15 centers in the United States to evaluate the potential risk factors for major adverse cardiac events after repair. Twenty-one percent of the population had a major event and 16 patients died, or 7% of the total, 10% required ECMO, and 12% cardiopulmonary resuscitation in the postoperative period. The data from these 15 centers is remarkably similar to the collected data from the STS Congenital Heart Surgery Database in terms of mortality and need for ECMO support, suggesting that the 15 centers, which in fact represent a range from small- to large-volume programs, accurately reflect the overall patient population that does undergo this procedure. The authors found there was a trend suggesting patients who were discharged from the neonatal unit with medical management and later repair had a worse outcome than those who underwent surgical repair earlier and that longer duration of cardiopulmonary bypass of over 150 minutes and the use of larger RV-PA conduits are associated with adverse events.
        It has been recognized I think for many years that truncus arteriosus is an unstable lesion and that cardiovascular collapse can occur at any time as pulmonary resistance drops, and therefore most centers consider truncus to be a condition that would require urgent newborn surgery at the same hospitalization, and the authors’ results tend to confirm the desirability of early surgery.
        Longer cardiopulmonary bypass time was associated with a worse outcome in almost all congenital heart lesions. It is notable that the median bypass time difference in those patients with major adverse events compared with those without events was only approximately 20 minutes. However, the range of bypass times was significantly wider in the patients with adverse events, potentially reflecting more complex operations or difficulties with the repair.
        With the small number of patients in this series that actually had adverse events or died, it would be useful to see if there were any specific characteristics of those patients who required prolonged bypass times in terms of their operative procedure. Maybe you could tease out some of those effects of longer bypass time and whether it was actually the more complex repair that caused a longer time.
        You speculate that larger conduit size might cause adverse events from larger ventriculotomies and potential sternal compression. However, it is noted that over 50% of the patients had elective open sternums at the end of the procedure and therefore it's not really clear that conduit size or sternal closure per se would be associated with adverse events because most of the chests were open at that time. In addition, the difference in ventriculotomy size between a 12- and 10-mm conduit is relatively small. The tachyarrhythmias also tended to occur more commonly in patients with larger conduits. I would suggest that perhaps rather than ventriculotomy size or ventriculotomy issues and RV dysfunction that larger conduits tend to represent essentially an aneurysm of the right ventricle where the total stroke volume might barely fill the proximal conduit, and tachycardia might be a result of inefficiency of right ventricular outflow.
        In addition, it has been our experience that the most common complication after repair of truncus is kinking of the branch pulmonary arteries with either stretch of the right pulmonary artery or stenosis of the left pulmonary artery because the pulsatility of the conduit and the size mismatch between the conduit and the pulmonary branches can cause kinking of the pulmonary vessels. Relative conduit stenosis can affect RV function and overall cardiac output. And with the small number of mortalities in this series, only 16, I wonder if you could comment on whether the actual causes of death were identified in the patients who did not survive their major cardiac events and whether there was echocardiographic evidence of any kind of technical issue at the completion of operation in those patients who ultimately went on to have adverse events or mortality.
        You collected data on many variables preoperatively, intraoperatively, and postoperatively, but I saw no evidence of an assessment of the intraoperative echo and a correlation with major adverse events postoperatively, nor inotropic use postoperatively and other indicators of poor cardiac output. I wonder if you could comment on that.
        Perhaps a more aggressive examination of the pulmonary outflow tract in patients who are not responding as expected after cardiac repair would identify some patients who might have revision of their surgical repair with potential improvement of their outcome and reversing of their adverse event.
        Although you noted in your manuscript that conduit type was not directly associated with adverse outcome, it is notable that use of the Contegra conduit, as you mentioned, was much more common in those with adverse events. Because the Contegra conduit's smaller sizes seem to have a size >50 mm2 body surface area in all but the very large potential recipients, would you recommend that the Contegra conduit be discontinued in use for truncus arteriosus repair and femoral vein or other homograft conduits be preferentially used? Also, would you recommend maybe that we even abandon the use of conduits in the current era of primary repair and go back to the original truncus repair as described by Barbero-Marcial and others with direct connection of the right ventricle to the pulmonary arteries.
        It is clear that truncus repair continues to carry a remarkably high mortality for what is really a simple operation, VSD closure and a conduit. It is surprising that if you look at the overall mortality, and even in the STS database, it can range as high as 10% for what is a fairly simple lesion.
        Although I agree that conduit size is very likely to be a significant factor in hemodynamics after repair, did you analyze the mortalities carefully to see if there were any other patterns in terms of residual cardiac lesions or postoperative signs that might suggest a higher risk for a poor outcome? It is interesting that you had a lower incidence of major adverse events in patients with DiGeorge syndrome, which is contrary to what we would otherwise generally expect.
        I congratulate you on undertaking a study with data collection over multiple centers and adding to the literature on what still remains a relatively high-risk cardiac procedure despite standardized surgical approaches over the past 30 years.
        You didn't include echo data, I noticed, in your analysis, and I would assume that in these centers all patients underwent an echocardiogram at the end of the cardiac procedure.
        Dr Christopher W. Mastropietro (Indianapolis, Ind). Thank you for the wonderful summary and insightful questions. We did have postoperative echocardiographic data. We have actually a lot of data, more than I could actually present in this session. We looked at ventricular function, valvular regurgitation, valvular stenosis, and the presence or absence of an atrial septal defect or PFO. We really found no clear association between echocardiographic data other than if you had severely depressed ventricular function—that was typically associated with one of these events. But typically those patients were the ones that were on ECMO support.
        As far as patterns, we did identify a few interesting patterns. One pattern is that we had a handful of patients who had truncal valve repairs and replacements during the same operation. Those patients who had a valve repair attempt first, then came off pump but the surgeons didn't like the way it looked and the patients weren't doing well, went back on pump, then underwent replacement—these patients had extremely long bypass runs and ended up on ECMO, and I think only 1 of those patients survived, as opposed to the patients who had very ugly valves that the surgeons just replaced without a previous attempt at repair—these patients had much shorter bypass runs, did not come off bypass on ECMO, and all of those patients survived.
        As I wrote in the manuscript, 12 patients were actually sent home with the diagnosis of truncus arteriosus, with a plan to be managed medically and told to come back at a later date for surgery. Of these patients, 7 were readmitted before their surgical day in severe respiratory failure, 1 of them went on ECMO, and 1 of them developed severe necrotizing enterocolitis. So those patients went into these operations in a rough state and obviously came out in a rough state.
        There were definitely a few of the incidents of CPR where the triggering events led to either ECPR or death, and there were just a handful of patients that came out on ECMO and just were not able—it was just one problem after another—to be liberated from ECMO and were ultimately withdrawn from support. So that's my synopsis of some of the insight into some of the reasons why they died.
        As far as your comments on conduit size, I believe you asked if the Contegra should not be used in favor of the smaller conduits. I don't think we can say that, but I definitely think if you have a sick patient who is going into the operation in a less than optimal state, you probably should pay a little bit more attention to conduit size, because that might be 1 extra factor that might push that kid over into requiring ECMO or having an adverse event.
        I know I didn't answer all of your questions. I think we will start with that and you can draw out whatever I didn't address.
        Dr Spray. I think you addressed them fine. I think you are on to something with conduit size. I do think conduit size and larger sizes is more of a problem in terms of pulmonary artery reconstruction, not so much ventriculotomy, and then the question is, what is the RV pressure at the end of the operation. And if you have tricuspid regurgitation and you have significant RV hypertension, sometimes that's related to pulmonary artery kinking rather than RV failure per se, then that evolved into RV failure, ECMO support, but then sometimes subsequent improvement and you can come off ECMO.
        You didn't really say what categories of patients with adverse events went on to die as opposed to those who went on to recover, and the ones who recovered, was there something unique about them that made them recover compared with the others?
        Dr Mastropietro. I don't think we really got that granular with the data as far as looking to see which patients with the larger conduits actually made it through their ECMO run or made it through their episode of CPR and actually did not die and what happened to them down the road, something I can easily look back at. We have all the descriptive data.
        And I agree with you completely. Your speculation is obviously going to be better than mine as far as why the larger conduit sizes might be associated with these events. I think your insight is great and it is stuff I wish I would have wrote in the manuscript.
        Dr Spray. People went to conduit repair for truncus because the perception was that the patients had more instability when you didn't have a pulmonary valve in the RV outflow tract at the time of repair and that pulmonary hypertension would be less well tolerated by the right ventricle, and that was really the primary reason to use conduits in the initial repair. One wonders if in the current era whether that's really true anymore and whether we might consider going back to nonconduit reconstruction as a way of avoiding some of these problems.
        But I think it is a very interesting study. Thank you.
        Dr Mastropietro. Thank you.
        Dr J. William Gaynor (Philadelphia, Pa). One brief question. Was the use of conduits uniform across the centers or was it only a few that used Contegra? You looked at center volume, but in your analyses did you include a center variable in the univariate and multivariate analysis, did you adjust for institution across those, because if Contegra is only used at a few institutions, it could be a marker for an institutional variation.
        Dr Mastropietro. For sure. We actually used a random effect for center, and we didn't actually put center volume into the model.
        Dr Gaynor. Not center volume but center.
        Dr Mastropietro. Yes, center as a variable in and of itself. And the conduit type actually varied much more with surgeon and not necessarily with center. There was I think only 1 center that universally used the same conduit for all the operations. Most centers seemed to have multiple conduits.
        Dr Gaynor. Was the Contegra used at all?
        Dr Mastropietro. I think the Contegra was not used at all centers. I think it was used at 4 or 5 of the 15. The larger centers seemed to use the Contegra more than the smaller ones.