Y-incision aortic annular enlargement (Y-AAE) is a relatively recent surgical technique for patients undergoing surgical aortic valve replacement (SAVR) who have a small aortic annulus. It was developed by Bo Yang and his group in 2020, primarily to allow implantation of a larger aortic prosthesis using a reproducible technique, thereby reducing the risk of prosthesis-patient mismatch (PPM) and improving prosthetic valve hemodynamics. Y-AAE involves a Y-shaped incision at the commissure between the left and noncoronary sinuses, extending into the aortomitral curtain. Placement of a patch then allows enlargement of the surgical annulus and aortic root.

Since its introduction, the technique has generated some controversy, particularly regarding what should actually be considered the “aortic annulus” and whether the enlargement achieved is truly effective or represents genuine annular enlargement. However, accumulated experience and subsequently published studies have provided data that help clarify several of these concepts. Consequently, the technique has gained popularity, particularly in the United States, and has become an increasingly feasible option for treating these patients.

The criticisms can be grouped into five controversial points, which are discussed below.

The first arises from confusing the surgical aortic annulus—a three-dimensional, crown-shaped structure—with the basal annulus measured by imaging. The annulus visualized on echocardiography or CT usually corresponds to a virtual basal ring, defined by the plane connecting the lowest points (nadirs) of the three leaflets. This distinction is fundamental, because the goal is not simply to increase an imaging-derived measurement, but rather to create sufficient space to implant a prosthesis with an effective orifice area appropriate for the patient and consistent with that basal annulus.

In the initial series of 119 patients, Y-AAE enlarged the surgical annulus, allowing implantation of prostheses 3–4 sizes larger (median 29 mm), with actual effective orifice areas of approximately 2.2–2.7 cm² and mean gradients of approximately 5–7 mmHg.

The second misconception is that Y-AAE would be insufficient because it does not directly enlarge the basal annulus or left ventricular outflow tract (LVOT). However, in isolated valvular aortic stenosis in adults, the obstruction is located at the leaflets. Once the valve has been replaced, the LVOT and basal annulus are generally of adequate size and do not themselves represent sites of obstruction.

In those initial 119 patients, the mean gradient across the LVOT was approximately 2 mmHg before surgery and remained 2 mmHg afterward, demonstrating the absence of significant obstruction that would justify its enlargement.

The third concern is that, rather than enlarging the annulus, the procedure might simply tilt the prosthesis. However, the technique is designed to preserve appropriate three-dimensional geometry. The three lowest points of the prosthetic sewing ring are secured to the three nadirs of the aortic annulus. Likewise, the new commissure is sutured onto the patch at a height equivalent to that of the native left-noncoronary commissure.

Three-dimensional CT reconstructions have shown that both bioprosthetic and mechanical valves can remain properly aligned without significant tilting. Therefore, annular enlargement does not necessarily result in altered prosthetic valve orientation.

The fourth issue concerns the subsequent treatment of a degenerated prosthesis using valve-in-valve procedures. The concern is that a large prosthesis might lie too close to the coronary ostia, increasing the risk of coronary obstruction during future TAVI. However, Y-AAE enlarges not only the annulus but also the aortic root and sinotubular junction by approximately 6–7 mm, while maintaining a similar valve-to-coronary ostia distance.

The final concern is that a larger aortic root and larger prostheses could produce turbulence, stasis, and flow disturbances that might promote thrombosis. Fluid dynamics analyses performed after Y-AAE do not support this hypothesis. Predominantly laminar flow through the prosthesis and ascending aorta has been observed, with minimal blood stasis. Therefore, creating a larger root does not appear, by itself, to generate a detrimental flow pattern.

Clinical follow-up is also reassuring. In a current series of 229 patients, with a maximum follow-up exceeding five years, only two developed hypoattenuated leaflet thickening (HALT). Both had a 29-mm prosthesis: one had undergone Y-AAE and the other valve replacement without annular enlargement. In both cases, HALT resolved with apixaban. Thus, the available data do not suggest that Y-AAE or the use of large prostheses increases the risk of prosthetic valve thrombosis.

COMMENTARY:

Aortic annular and root enlargement techniques are experiencing a clear increase in use. According to the cited data from the Society of Thoracic Surgeons (STS) database, between 2020 and 2023 the proportion of aortic valve replacements incorporating root enlargement increased from approximately 8% to 13%. Among women, the increase was even greater, from 18% to 27%. In parallel, the STS-predicted risk of mortality decreased from approximately 2.24% to 2.04%.

This reflects growing awareness of the consequences of implanting small prostheses in patients with small annuli. The issue is not the nominal diameter of the prosthesis, but its effective orifice area. Surgical prostheses have an effective orifice area smaller than the nominal size reported by the manufacturer. Therefore, a seemingly adequate prosthesis may still result in PPM.

Y-AAE does not simply aim to increase an echocardiographic measurement of the annulus, but rather to create the anatomical space required to implant a prosthesis with an effective orifice area appropriate for the patient’s true functional size, thereby reducing PPM, promoting regression of left ventricular hypertrophy, and, at the same time, preserving the possibility of future valve-in-valve interventions.

Nevertheless, these results should be interpreted with caution, as Y-AAE is a relatively recent technique and the available series remain limited compared with conventional techniques.

REFERENCE:

Yang B, Chen SA. The 5 Misconceptions of Y-Incision Aortic Annular Enlargement. Ann Thorac Surg. 2026 Jun;121(6):1281-1282. doi: 10.1016/j.athoracsur.2025.12.049. Epub 2026 Jan 30. PMID: 41619928.