Addressing mild-to-moderate aortic root dilation during concomitant aortic valve and ascending aorta replacement remains controversial. The primary options are composite valve conduit replacement (Bentall procedure) and separate ascending aorta and aortic valve replacement, preserving the root with a prosthetic aortic valve and supracoronary graft (commonly known as the Wheat procedure). The Bentall procedure is more aggressive and may lead to root-related complications, while the Wheat procedure, a seemingly less invasive approach, theoretically increases the risk of aneurysm or dissection in the preserved aortic root. However, no long-term studies to date have validated this risk.

This study by Mayo Clinic offers clarity on this issue through a retrospective analysis of 778 adult non-syndromic patients with an aortic root diameter ≤55 mm who underwent ascending aorta and aortic valve replacement between January 1994 and June 2017. Patients were divided into two groups according to aortic root management: the Bentall procedure in 406 patients (52%) and separate replacement of the ascending aorta and aortic valve in 372 patients (48%). Propensity score matching was used to balance baseline characteristics, resulting in 188 matched pairs. Analysis revealed a median sinus of Valsalva diameter of 43 mm (39-47 mm). Short- and long-term mortality did not differ significantly between groups: operative mortality was 2% in the Bentall group and 3% in the Wheat group, while long-term mortality rates remained similar after a mean follow-up of 9.6 years (8.4-10.1 years). There were also no significant differences in reoperation rates, with 7% in the Bentall group and 10% in the Wheat group. In the propensity-matched Wheat group, sinus of Valsalva diameter decreased by 2 mm (0-4 mm) after a mean follow-up of 41 months.

In conclusion, for patients with mild-to-moderate aortic root dilation, both the Bentall and Wheat procedures present similar short- and long-term mortality and reoperation risks. The Wheat procedure does not seem associated with subsequent root dilation in midterm echocardiographic follow-up.

COMMENTARY:

Previous posts on this blog have addressed aortic root surgery in the context of aortic dissection, a rare but critical condition. In the study reviewed today, we revisit aortic root surgery, focusing on a much more common clinical scenario. This involves patients who require concurrent aortic valve and ascending aorta surgery, but with mild-to-moderate root dilation (<55 mm). The central question this study raises is whether the Bentall or Wheat procedure is equally, less, or more effective in these cases.

The primary finding from this study, shedding light on this issue after a median follow-up of almost 10 years, is that reintervention rates were low and not significantly different between the two patient groups. While more in-depth analysis is warranted, this outcome supports the notion that either the Bentall or Wheat procedure can be effective and suitable options for this specific patient population.

What does the existing literature say? Thirty years ago, the Stanford group established the Bentall procedure as their preferred intervention for such patients. Shortly after, in 2000, Sundt et al. sought to determine the optimal intervention in patients with bicuspid valves, finding that both the Bentall and Wheat procedures yielded similar long-term outcomes. Subsequent studies supported these findings, with some, like Sioris et al., achieving excellent results by selectively replacing only the dilated noncoronary sinus in the Wheat procedure, effectively avoiding reinterventions. Overall, despite the lack of randomized trials and the reliance on case series, no evidence currently suggests that patients with mild-to-moderate dilation who undergo the Wheat procedure face poor long-term outcomes. The findings of this article, based on an extensive patient series and nearly a decade of follow-up, align with the current body of literature.

A notable aspect of this study is the reduction in sinus of Valsalva diameter by 2-3 mm during a mean echocardiographic follow-up of 41 months. Remarkably, no patient in the Wheat group required reintervention for aortic root dilation over 19 years of clinical follow-up, underscoring the rarity of root dilation to a degree necessitating surgery. Other studies have similarly reported such decreases in size post-Wheat procedure, including reductions of 2-3 mm after 6 years (Vendramin et al.) and up to 9 mm in just 4 years (Nardi et al.). Additionally, some studies suggest that root stabilization may persist for over a decade.

The surgical risk associated with the Bentall procedure is well documented, with recent STS database reviews estimating an increased risk of 2.8%. This risk may be higher for patients with non-significantly dilated roots and low coronary ostia, a scenario common in this study’s cohort. Although early mortality did not differ significantly in this Mayo Clinic series compared to the Wheat procedure, characteristic complications, such as coronary revascularization or pseudoaneurysm formation, were observed.

The primary limitation of this study is the inability to ascertain the criteria for selecting Bentall or Wheat procedures for different patients. Propensity score matching was implemented to reduce selection bias, although the matched patient proportion was low. Additionally, the study’s retrospective design led to incomplete follow-up, with sinus of Valsalva measurements missing for some patients, and these measurements were based on echocardiography rather than computed tomography. Lastly, while not a strict limitation, a median follow-up of 10 years may not be sufficient to capture significant differences between procedures, as reoperations often occur 12-20 years post-intervention. Prospective studies with longer follow-ups are thus needed to draw more definitive conclusions.

For aortic roots <55 mm, the choice between a Bentall or Wheat procedure is influenced by a variety of factors, ranging from case-specific variables—such as clinical presentation, patient age, comorbidities, and aortic valve type—to the surgeon’s experience and preferences. Interestingly, both the literature and this study seem to simplify these variables, suggesting that outcomes are similar for both Bentall and Wheat procedures. Nevertheless, in clinical practice, experienced surgeons tailor each case individually. For instance, a young patient with a small body surface area, bicuspid aortic valve, and suboptimal aortic wall tissue quality might prompt many surgeons to perform a root procedure. Conversely, for a 45 mm root in an older patient with a tricuspid valve, a Wheat procedure might be preferable. These nuances are not reflected in these studies, highlighting the essential role of surgeon expertise, potentially the most influential factor in determining prognosis. This is validated by the strong outcomes observed in this study, emphasizing the importance of excellent patient selection for each intervention by the involved surgeons.

REFERENCE

Cangut B, Greason KL, Todd A, Arghami A, Krishnan P, Crestanello JA, et al. Aortic root replacement in the setting of a mildly dilated nonsyndromic ascending aorta. J Thorac Cardiovasc Surg. 2023 Oct;166(4):983-993. doi: 10.1016/j.jtcvs.2022.03.044.