World Journal for Pediatric and Congenital Heart Surgery | 2021
Caution Required Contextualizing Recommendations for Infants and Neonates in a Pediatric Experience of Mitral Valve Replacement
Abstract
There are very few self-confessed experts in infant “mitral valve” replacement. It is an occasional operation as highlighted by this report by Elsisy et al at the Mayo Clinic which performed on average only one mitral valve replacement annually, on a child younger than two years of age. It is an operation that is performed when no other options exist and often at the end of a road that started with a repair. In today’s practice, a leaking canal-type left atrioventricular (AV) valve is the most common indication, followed by the small dysplastic mitral valve which is often part of a Shone-type complex. Historically, infant left AV valve replacement has been strenuously avoided, in part because of the perceived poor shortand long-term outcomes associated with the procedure, including the need for anticoagulation. That was then, and things have changed. Several groups report very low mortality, satisfactory functional outcomes, and reasonable freedom from reoperation in this age-group. This report describes a 26-year experience of 119 mitral valve replacements in “pediatric” patients. A prosthesis size of 23 mm was noted as a threshold below which earlier reintervention was likely to occur. The authors’ conclusion is that better outcomes are achieved when mitral valve replacement is performed after the age of two and with a prosthesis size of 23 mm or greater. In search of better outcomes, should we then wait for patients to achieve two years of age and avoid using a prosthesis sized less than 23 mm? The authors advise that even re-repair with a “acceptance of a suboptimal result,” including “moderate residual regurgitation or stenosis,” should be considered, in order to achieve two years of age and a 23 mm valve. The authors dichotomized their experience above and below two years of age. It is not surprising then that the younger group would fare worse by usual parameters of success including mortality and time-toreintervention. We would suggest that conclusions drawn from these data are not easily translated to everyday practice. We don’t get to choose the timing of mitral valve replacement—timing is determined by the patient, their pathology, and failure to achieve a satisfactory growth trajectory. The results of mitral valve replacement over two years of age may be superior to younger patients, but this should in no way be seen as a practice guideline regarding timing. To reinforce this concept that the patient declares when they need an operation, 44% of operations in the younger age-group were performed urgently or emergently. For infants requiring mitral valve replacement, it is best to worry about the future tomorrow—if that future involves reoperation in five years in an otherwise well child, that is, an acceptable problem in managing life with mitral valve disease. Seeking to upsize in order to achieve a 23-mm prosthesis, even in patients over two years of age, may be associated with increased risk of heart block and other complications. The report, while technically correct in its statistical comparisons, does not realistically capture the likely outcome of mitral valve replacement in infants, nor are its recommendations necessarily relevant to infants. Indeed, it may be unwise to tolerate significant mitral valve disease until two years of age, with the risk of pulmonary vascular disease, risk of ventricular dysfunction, and precipitous circulatory collapse. A close look at the outcomes by era is interesting. The authors point out that the mortality rate decreased to 0%, most notably in the cohort less than two years of age in the most recent era (2011-2019). They conclude “we have demonstrated improved outcomes in the current era with the younger age group.” The total number of patients in each era undergoing mitral valve replacement (MVR) is not explicitly stated: based on the percentages and information in Table 3, we calculate that 8 MVRs were performed in the less than 2-year-old cohort from 1993 to 2000 with 3 mortalities (37.5%), 15 from 2001 to 2010 with 4 mortalities (26.7%), and 3 MVRs were performed in the last era. The message of reduced mortality in younger patients is credible and one that aligns with other reports. Nevertheless, with only 12% of the operative experience in the last era, the conclusion is only loosely based on the reported experience. At the risk of purporting to be “expert,” we see four important considerations in infant mitral valve replacement, some of which have been previously reported. Firstly, avoidance of oversizing, secondly wide resection of the subvalvar apparatus that may entrap prosthetic leaflets, thirdly, placement of many fine, for example, 5/0 mattress sutures passed through a 5-mm fringe of leaflet tissue with the placement of small pledgets on the ventricular aspect, to evenly spread tension, and lastly, avoiding annular sutures and thus annular compression that may contribute to postoperative heart block and ventricular dysfunction. An inverted aortic prosthesis is sometimes the best choice for a small annulus, as the housing of the mechanism sits in the atrium, and away from the left ventricular outflow tract. To make ageor size-based recommendations using evidence, a larger patient experience will need to be reported. This should include neonates, infant categories, and those over one year of age, rather than lumping these three groups as being <2 years of age. Such a report will require multicenter participation, given the low volume of such cases. In the meantime, we suggest that mitral valve replacement in small children is performed when needed and not delayed in anticipation of an arbitrary time point.