Bentall Procedure in Small Aortoannular Complex: Impact of Implantation Plane on Prosthesis Upsizing and Early Outcomes

Technical Summary: Bentall Procedure in Small Aortoannular Complex

Problem Statement
In patients with severe aortic stenosis (AS) presenting with a small aortoannular complex and/or a narrow sinotubular junction-proximal ascending aorta, surgical reconstruction poses a significant challenge. The primary constraint is the limited space for implanting a valved conduit with an adequate effective orifice area (EOA). This anatomical limitation increases the risk of prosthesis-patient mismatch (PPM), which is associated with increased left ventricular workload, limited functional recovery, and worse outcomes. While the Bentall procedure is standard for root replacement, its application in small-root anatomy requires careful planning to balance technical feasibility with optimal hemodynamic performance. The study addresses the need to determine if redefining the implantation plane can facilitate the implantation of larger prostheses without compromising safety.

Methodology
This single-center, retrospective cohort study analyzed 402 adult patients who underwent the Bentall procedure between January 2020 and April 2026 at Dr. Siyami Ersek Thoracic and Cardiovascular Surgery Training and Research Hospital. Patients were selected based on severe AS associated with a small aortoannular complex (defined as an annular diameter ≤21 mm or intraoperative sizing limiting prosthesis to 21 mm) and/or a narrow sinotubular junction.

The cohort was divided into two groups based on the proximal conduit implantation plane:

1. Supra-annular-supported annular conduit implantation (SSAC): The standard Bentall technique where interrupted pledgeted sutures are passed through the annulus with pledgets positioned above the annulus, seating the conduit in a supra-annular position relative to the native annulus.
2. Subannular-supported supra-annular conduit implantation (SSSC): A modified technique where, after complete annular ring resection, sutures are passed from the subannular plane (left ventricular side) with pledgets remaining subannular. The sutures are exteriorized through the residual aortic root, and the conduit is seated on a newly created, lower "neo-annular" plane. This aims to allow the conduit to sit in a supra-annular position relative to the native annulus while permitting a larger conduit size.

Key Contributions and Technical Approach
The study's primary technical contribution is the comparative evaluation of the SSSC technique against the standard SSAC approach specifically for small-root anatomy. The authors operationalized "size gain" as the difference between the implanted prosthesis size and the standard expected size (based on preoperative CT or intraoperative sizers). The study also evaluated the functional impact of this upsizing through early hemodynamic metrics, including indexed effective orifice area (EOAi), PPM rates, and transprosthetic gradients.

Results

• Prosthesis Upsizing: The SSSC group demonstrated a statistically significant advantage in prosthesis size. The mean implanted size was 23.4 ± 1.4 mm in the SSSC group versus 22.0 ± 1.1 mm in the SSAC group (p < 0.001). The mean size gain was 3.0 ± 1.1 mm for SSSC compared to 1.7 ± 1.0 mm for SSAC. Notably, zero size gain occurred in 19.7% of SSAC patients but in no SSSC patients.
• Operative Efficiency: The SSSC group had significantly shorter cardiopulmonary bypass (CPB) times (135.9 ± 10.8 vs. 168.0 ± 31.6 min) and cross-clamp times (95.5 ± 11.1 vs. 111.1 ± 23.1 min) compared to the SSAC group.
• Hemodynamics: While both groups showed significant reduction in preoperative gradients, early postoperative mean and peak gradients were similar between the two techniques. However, the SSSC group achieved higher postoperative EOA (2.02 ± 0.29 vs. 1.90 ± 0.34 cm²) and EOAi (0.98 ± 0.15 vs. 0.93 ± 0.18 cm²/m²). Consequently, the rate of moderate PPM was lower in the SSSC group (19.5% vs. 30.7%; p = 0.017). No severe PPM was observed in either group.
• Complications: The complication profiles differed. The SSSC group had a higher rate of new permanent pacemaker implantation (7.9% vs. 2.1%). Conversely, the SSAC group exhibited higher rates of bleeding revision, postoperative atrial fibrillation, low cardiac output syndrome, and infection. Multivariable analysis suggested SSAC was associated with higher odds of low cardiac output syndrome and bleeding revision, though sensitivity analyses indicated these associations required cautious interpretation due to operative complexity factors.
• Mortality: In-hospital and 30-day mortality rates were similar between the two groups.

Significance and Claims
The paper claims that in the context of small aortoannular complex Bentall surgery, the SSSC technique provides a more consistent and reliable method for prosthesis upsizing compared to the standard SSAC approach. The authors posit that the primary benefit of SSSC is not necessarily a reduction in early transprosthetic gradients, but rather the achievement of a higher EOAi and a reduction in the incidence of moderate PPM. This suggests that the functional "root-enlargement" effect of SSSC improves prosthesis-patient compatibility early in the postoperative period.

The study concludes that SSSC is a feasible strategy that expands the implantation field for larger conduits in small roots. However, the authors emphasize that this technique carries a distinct risk profile, specifically a higher likelihood of requiring a permanent pacemaker, likely due to the subannular fixation plane's proximity to the conduction system. The paper frames these findings as hypothesis-generating, noting that the retrospective nature and lack of long-term follow-up limit definitive conclusions. The authors advocate for mid- and long-term echocardiographic follow-up and multicenter studies to precisely define the clinical role of this approach.