Aortic root enlargement with robotic surgery

Patient prosthesis mismatch (PPM) was first described in 1978, reflecting the inadequacy of prosthetic heart valves to match the physiologically required orifice area of the healthy valve (1). The shortfall arises as the native heart valves are highly efficient at opening to virtually the full area bounded by the annulus. By contrast, prosthetic valves are limited to a maximal structural diameter equivalent to the annulus, within which a sewing ring, stent frame, and leaflet apparatus must be accommodated, leaving a smaller functional internal diameter. Additionally, prosthetic leaflet materials are inherently thicker and less pliable than healthy valvular tissues and the hinge points where the leaflets are sutured to the stent posts may not have the same degrees of freedom, so the full area of the internal diameter may not be fully utilised. The effective orifice area (EOA) of the prosthetic valve is therefore smaller than the area within the internal diameter of the prosthesis (Figure 1). PPM describes where this residual EOA is restrictive for the required cardiac output.

Figure 1 The effective orifice area (green shaded area) of a prosthetic valve in relation to the area of the internal diameter (red shaded area). The external diameter includes the stent struts and sewing ring.

A number of factors affect the development of PPM, including the design and size of the prosthesis, intra- vs. supra-annular placement, the native annular size and the body habitus of the patient. The most common metric used to estimate the overall effect of these factors is the EOA, indexed to the patient’s body surface area (BSA). Severe PPM (defined as an indexed EOA ≤0.65 cm²/m²) confers a doubling of 5-year mortality and a three-time higher incidence of congestive heart failure (2). Options to mitigate the risk of PPM are shown in Table 1. Despite these methods, an estimated 65% of patients undergoing isolated aortic valve replacement from the Society of Thoracic Surgeons Adult Cardiac Surgery Database had moderate or severe PPM at procedure end (3). Until prosthetic valve designs allow EOA to approach the full extent of the area bounded by the annulus, methods to facilitate aortic root enlargement (ARE) will be required to increase uptake of this technique.

Darehzereshki and colleagues present a case series and video demonstration of robotic aortic valve replacement (RAVR) with ARE (4). We would first like to commend the authors for their technically accomplished video demonstrating their center’s experience, case volume, and reported outcomes reflecting a high level of institutional expertise. As the authors describe, the use of robotic assistance in such cases allows a rib-sparing non-sternotomy approach to the aortic valve, facilitating advanced techniques with a minimally invasive approach.

The broader context of this work deserves acknowledgement. Minimally invasive aortic valve replacement—whether through upper hemi-sternotomy or right anterior mini-thoracotomy—has, over two decades, consistently demonstrated reductions in blood loss, transfusion requirement, wound-related morbidity and length of hospital stay compared with conventional full sternotomy, while preserving the durability of surgical valve replacement (5). Importantly, previous work has shown that even technically demanding adjuncts such as aortic annular enlargement are feasible through a right anterior mini-thoracotomy in experienced hands (6). The robotic platform represents a natural next step in this trajectory, offering three-dimensional high-definition visualization, wristed instrumentation, and a rib-sparing lateral access incision that further minimizes chest wall trauma. The present series, together with the authors' prior work on robotic ARE (7), is therefore noteworthy not only for the technical accomplishment of the individual operations but also for what it signals: that complex, reconstructive aortic valve surgery—historically the preserve of the full sternotomy—can be delivered through a 3 cm transaxillary incision without compromising the core surgical principles of exposure, haemostasis and reproducibility. The authors and their institution deserve considerable credit for advancing this field and for sharing their technique in a format that allows the wider cardiac surgical community to learn from it.

The video briefly outlines the principal operative steps, including excellent exposure of the aortic valve, careful valve explantation, thorough annular decalcification, and meticulous patch reconstruction. The depiction of patch suturing—whether confined to one side of the aorta or extended toward the pulmonary artery aspect of the aortotomy—is particularly useful to show the degree of precision achievable with a robotic platform.

It is notable that in the three presented cases the sinus patch repair was performed after implantation of the prosthetic valve. In this setting, the reconstruction appears primarily intended to facilitate aortotomy closure rather than to achieve substantive annular enlargement for valve upsizing. One might reasonably consider that in the absence of patch reconstruction, selection of a smaller prosthesis would have been necessary to ensure safe and tension-free aortotomy closure.

While the demonstrated procedure is anatomically a form of root enlargement, traditional “root enlargement” techniques are defined by intentional annular expansion. In established methods such as the Nicks (8), Nuñez (9), Manouguian (10), or Yang (11) procedures, annular enlargement constitutes a central component of the operation, and valve sutures are passed through the patch. This incorporation of the reconstructed patch segment into the neo-annulus increases the circumference of the native annulus by the length of the patch through which annular sutures are passed. Given that circumference (C) is a function of diameter (d) where C = pd, there is a 2 mm increase in valve diameter (i.e., an increase of one valve size) for every 6 mm of patch width augmentation of the annulus. The size of the implanted prosthesis shown in the video is prior to the patch enlargement and therefore the annulus appears not to have been augmented with a patch. In addition, the valve sutures at the apex of the Nicks incision are not shown, so it is unclear if the incision extends underneath the implanted valve, but this seems unlikely as this would be inaccessibly below the sewing ring.

Importantly, the outstanding exposure and operative visualization demonstrated in these videos highlight the promise of robotic surgery as a platform for the full gamut of enlargement procedures. In particular, the ability to gusset-patch to the far side of the aortic incision indicates superb access from the right side of the chest. Techniques such as the Manouguian or inverted Y enlargement, which may allow upsizing by two or more valve sizes, could be particularly well suited to this approach. The enhanced visualization provided by robotics may facilitate accurate annular extension and patch integration, thereby broadening the role of true annular enlargement in minimally invasive surgery beyond simply avoiding implantation of a 19 mm prosthesis.

PPM is typically predicted pre-operatively using echocardiographic or radiological measures of annular size to estimate the optimal size of prosthesis that can be implanted. While absolute annular size (or absolute implanted valve size) is a useful screening tool, it should be noted that there can be a 17% difference in EOA between different valves of the same nominal size and that the cardiac output and physiological requirements will differ between patients of different sizes. These differences can be adjusted for by:

• Estimating the implantable size of the chosen prosthesis;
• Cross-referencing against manufacturer-published EOAs; and
• Indexing to the patient’s BSA.

In should be noted that BSA provides a much closer estimate of physiological requirement for lean/fat-free mass compared to body mass index (BMI), but is poorly correlated with true cardiac output. Some caution must therefore be applied to the use of indexed EOA in predicting PPM, as it does not correlate directly with valve haemodynamic obstruction (i.e., mean gradient ≥20 mmHg or Doppler velocity index <0.35) (12). Nonetheless, indexed EOA remains a more nuanced tool than annular size alone in predicting PPM (13). To adjust for BSA indexing for lean mass, in obese patients it is recommended to utilise more permissive criteria for predicting PPM. Commonly cited Valve Academic Research Consortium 3 (VARC-3) cut-offs for severe PPM are indexed EOA ≤0.65 cm²/m² in patients with a BMI <30 kg/m² and ≤ 0.55 cm²/m² in obese patients (BMI ≥30 kg/m²) (14).

In summary, this case series video provides a reassuring insight into the use of robotic assistance in minimally invasive cardiac surgery. Meticulous patch reconstruction beyond isolated aortic valve replacement is possible with excellent results. The quality of exposure and operative control shown supports the feasibility of undertaking more comprehensive annular enlargement strategies in appropriately selected patients, with the goal of optimizing prosthesis size and minimizing the risk of patient-prosthesis mismatch.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Journal of Visualized Surgery. The article did not undergo external peer review.

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://jovs.amegroups.com/article/view/10.21037/jovs-2026-0034/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Rahimtoola SH. The problem of valve prosthesis-patient mismatch. Circulation 1978;58:20-4.
2. Mohty D, Malouf JF, Girard SE, et al. Impact of prosthesis-patient mismatch on long-term survival in patients with small St Jude Medical mechanical prostheses in the aortic position. Circulation 2006;113:420-6.
3. Fallon JM, DeSimone JP, Brennan JM, et al. The Incidence and Consequence of Prosthesis-Patient Mismatch After Surgical Aortic Valve Replacement. Ann Thorac Surg 2018;106:14-22.
4. Darehzereshki A, Wei L, Mehaffey JH, et al. Robotic aortic valve replacement and aortic root enlargement for optimal prosthesis selection. Ann Cardiothorac Surg 2025;14:238-40.
5. Murtaza G, Wei L. Lateral access fully robotic aortic valve replacement "RAVR": from novel to normal. Ann Cardiothorac Surg 2025;14:192-201. [Crossref] [PubMed]
6. Robinson DA, Johnson CA Jr, Goodman AM, et al. Concomitant Annular Enlargement in Minimally Invasive Aortic Valve Replacement. Innovations (Phila) 2019;14:159-67. [Crossref] [PubMed]
7. Darehzereshki A, Wei LM, Comas G, et al. Feasibility and safety of robotic aortic root enlargement in conjunction with robotic aortic valve replacement. JTCVS Tech 2023;22:178-80. [Crossref] [PubMed]
8. Nicks R, Cartmill T, Bernstein L. Hypoplasia of the aortic root. The problem of aortic valve replacement. Thorax 1970;25:339-46. [Crossref] [PubMed]
9. Nuñez L, Aguado MG, Pinto AG, et al. Enlargement of the aortic annulus by resecting the commissure between the left and noncoronary cusps. Tex Heart Inst J 1983;10:301-3. [PubMed]
10. Manouguian S, Seybold-Epting W. Patch enlargement of the aortic valve ring by extending the aortic incision into the anterior mitral leaflet. New operative technique. J Thorac Cardiovasc Surg 1979;78:402-12. [PubMed]
11. Yang B, Naeem A, Palmer S. "Roof" technique-a modified aortotomy closure in Y-incision aortic root enlargement upsizing 3-4 valve sizes. JTCVS Tech 2022;12:33-6. [Crossref] [PubMed]
12. Vriesendorp MD, Groenwold RHH, Herrmann HC, et al. The Clinical Implications of Body Surface Area as a Poor Proxy for Cardiac Output. Structural Heart 2021;5:582-7.
13. Ternacle J, Pibarot P. Prosthesis-Patient Mismatch: The Complex Interaction between Cardiac Output and Prosthetic Valve Effective Orifice Area. Structural Heart 2021;5:588-90.
14. Généreux P, Piazza NVARC-3 WRITING COMMITTEE, et al. Valve Academic Research Consortium 3: updated endpoint definitions for aortic valve clinical research. Eur Heart J 2021;42:1825-57. [Crossref] [PubMed]