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- ↵*Reprint requests and correspondence:
Dr. Ralf J. Holzer, The Heart Center, Nationwide Children's Hospital, 700 Children's Drive, Columbus, Ohio 43205
Since its introduction in the mid-1980s (1), transcatheter therapy has replaced cardiothoracic surgery as the preferred treatment modality in the majority of patients with congenital valvular aortic stenosis. In 1990, a group from Children's Hospital Boston wrote an editorial in this journal titled “Balloon Dilation of Congenital Valvular Aortic Stenosis,” emphasizing the need for long-term follow-up data in this group of patients (2). Now, 20 years later in this issue of the Journal, the same group, with David Brown as the lead investigator, presents comprehensive long-term follow-up data in this patient cohort (3). This provides important insight into the freedom from reintervention and aortic valve replacement (AVR) after balloon aortic valvuloplasty.
On the basis of a retrospective analysis of 509 patients, with a median follow-up period of 9.3 years, the investigators found that 44% of patients required some form of aortic valve reintervention (repeat valvuloplasty, aortic valve repair, or AVR) during the follow-up period. The survival free from any aortic valve intervention at 20 years was 27%, and survival free from AVR was 53% at 20 years. Even though the exact causes of death were not specified in this study, the overall survival was 88% at 20 years. All these data are extremely helpful in counseling patients before transcatheter aortic valve therapies, and one probably should use a more cautious approach to long-term prognosis, especially when considering that survival free from aortic reintervention was only 27% and free from AVR only 53% at 20 years.
Although not significant by multivariate analysis, the investigators found by univariate analysis that survival free from AVR was shorter in older patients. As stated by the investigators, this finding likely reflects a lower threshold to intervene surgically, combined with the fact that operators may be more easily persuaded to upsize the balloon to achieve a better gradient reduction, because of the knowledge that surgery with adequate results is much more readily achievable than in neonates.
Not surprisingly, the investigators found that lower post-dilation aortic valve gradients and a lower grade of post-dilation aortic insufficiency (AI) were associated with a longer freedom from AVR. While these data are important, without clear thresholds, it does not help the interventionalist in deciding when a more aggressive approach may be warranted. Increasing the balloon size may lead to lower residual gradients and, therefore, theoretically to improved freedom from AVR. However, at the same time, an increased amount of aortic regurgitation may completely negate the achieved benefit, which has been the main reason for operators being reluctant to push for a more aggressive gradient reduction.
The difficulty faced in the catheterization laboratory is usually the decision on when to upsize (or not to upsize) the balloon, especially in those patients with borderline residual gradients of 30 to 40 mm Hg. When gradients are higher, especially in older patients, one very rarely hesitates to upsize the balloon when the degree of AI is only mild or less. However, if residual gradients are <30 mm Hg, there is very little to be gained in upsizing the balloon any further. Compounding this dilemma is the fact that balloons usually are only available in 1- to 2-mm increments, so that a single upsized balloon in an infant from a 10- to an 11-mm represents a 10% increase, while upsizing a balloon from 19 to 20 mm is only a 5% increase. To help answer these questions and to provide interventionalists with a better defined guide, the investigators compared freedom from AVR for different combinations of AI and residual aortic stenosis. For this purpose, patients were divided into those with residual gradients above and below 35 mm Hg in combination with different degrees of aortic regurgitation (none-trivial, mild, or moderate-severe). The finding that freedom from AVR was not any worse (and potentially better) in patients with residual gradients of <35 mm Hg and moderate or severe AI compared with patients with residual gradients of >35 mm Hg and mild AI should help in persuading operators to upsize the balloon if the gradient is 35 to 40 mm Hg with just mild AI, rather than a more conservative approach for fear of creating more AI. This is especially true as the long-term outcome seems notably better if the degree of AI were to remain mild, but the gradient would drop to <35 mm Hg. As such, within the borderline gradients of 30 to 40 mm Hg, further gradient reduction may be more important than the degree of AI in terms of long-term outcome. Although the investigators acknowledge that these data were not adjusted for age, they are the first data of their kind that give operators a quantitative guideline on when to continue with balloon valvuloplasty using a larger balloon size and when to stop.
These data may also influence the clinical follow-up of patients after AVR. Patients with a mild to moderate degree of AI and moderate residual stenosis (>40 mm Hg) are often not considered for repeat balloon aortic valvuloplasty, because of the concern of increasing AI, and are instead restricted from exercise because of the degree of residual AS and concern about sudden cardiac death, which is based on general consensus statements, such as the 36th Bethesda conference and other recommendations endorsed by the American College of Cardiology and the American Heart Association, but without any true evidence-based studies (4). However, with the data suggesting that moderate residual aortic valve stenosis may be worse than moderate AI in terms of survival free from AVR, it raises the question of whether restricting a patient from exercise because of moderate residual AS may in fact be a valid reason to seek a more aggressive transcatheter approach. If a patient is old enough to have all surgical options available at a fairly low risk, one could argue that it would be important to achieve an adequate gradient reduction that not only puts the patient into a better category with regard to long-term survival free from AVR but that may also allow the physician to remove any exercise restriction that was prescribed. This may lead to a repeat transcatheter intervention, even in the presence of mild to moderate aortic regurgitation, knowing that more definitive surgical therapy is available if a satisfactory transcatheter result cannot be achieved. The residual aortic valve gradient appears to be much more important in terms of freedom from AVR than previously anticipated. Many recent publications still state that “valvuloplasty is not recommended for asymptomatic patients with a peak-to-peak gradients <50 mm Hg” (5). Although this may still hold true for infants and smaller children with limited surgical options, the data in this present study do not support a conservative approach for this type of gradient in older children or young adults.
However, although these data are uniquely important, there are inherent limitations to this study. As acknowledged by the investigators, the main outcome variable, AVR, may not necessarily be a good descriptor of aortic valve function and may instead reflect a very variable referral pattern of individual cardiologists. As such, the clinical status, electrocardiographic changes, valve morphology and function, and the specific indications for surgical valve replacement may have been quite variable in this cohort. This is an inherent problem of retrospective studies, and the investigators concede that this could only be overcome with prospective data collection.
In conclusion, Brown et al. (3) have provided excellent data on the long-term outcomes in patients who have undergone balloon aortic valvuloplasty. These data will be extremely helpful in counseling patients about the not insignificant need for surgical AVR over a 20-year period and of practical importance in the catheterization laboratory when contemplating upsizing of the balloon. The data emphasize the importance of adequate gradient reduction for a satisfactory long-term outcome. Now, all we have to do is reconcile these data with the emerging transcatheter aortic valve implantation indications for aortic valve stenosis, again illustrating that aortic valve disease, whether congenital or acquired, is not a simple matter!
Dr. Holzer reports that he has no relationships to disclose. Dr. Cheatham has served as a consultant for AGA Medical, Medtronic, Inc., Numed, Inc., Toshiba Medical, and W.L. Gore & Associates, Inc. (all monies paid to author's employer).
↵* Editorials published in the Journal of the American College of Cardiologyreflect the views of the authors and do not necessarily represent the views of JACCor the American College of Cardiology.
- American College of Cardiology Foundation
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