Complexity in aortic arch surgery and laws of diminishing return

The management of acute type A aortic dissection (ATAAD) is a high-stakes challenge, with the Sun procedure [frozen elephant trunk (FET) plus total arch replacement] emerging as a key intervention in specialized centers (1,2). Zhu et al.’s cohort study (1), analyzing outcomes of the Sun procedure versus simpler surgical options, provides valuable insights (2-4). This editorial seeks to critically appraise the methodology and broader implications of the study, while exploring scalability and clinical utility for community cardiac surgeons. I am a broadly trained cardiac surgeon with experience across a wide range of procedures. I greatly admire centers where surgeons are able to concentrate on one or two highly specialized operations. While such focused practice is often a product of both opportunity and institutional structure—and not solely a reflection of surgical skill or intellectual innovation—it remains a goal that not all capable surgeons can readily achieve. Nevertheless, during complex and challenging cases, I continually strive to adopt advanced techniques, such as elements of the Sun procedure, to optimize outcomes and save patients' lives.

The study employs robust techniques, notably propensity score matching (PSM), to minimize preoperative variability. PSM enhances the reliability of comparisons between the Sun procedure and simpler alternatives, ensuring baseline comparability across groups. However, limitations remain, particularly in the selection criteria for the Sun procedure group. The authors highlight that candidates were younger and exhibited fewer comorbidities, likely reflecting selection bias towards those perceived as better surgical candidates.

The reliance on retrospective data introduces challenges. While comprehensive follow-up data and zero loss to follow-up bolster reliability, the study’s relatively short follow-up period (3 years) constrains long-term insights, particularly concerning distal aortic events (DAEs) and survival. Furthermore, the absence of patient-reported outcomes, such as quality of life and functional status, restricts a holistic understanding of the procedure’s impact.

The Sun procedure remains a complex operation, predominantly confined to high-volume with dedicated aortic surgeons, tertiary centers again a luxury even in the resource rich countries (4-6). Zhu et al. report a higher incidence of spinal malperfusion syndrome (MPS) in the Sun procedure group, with a notable paraplegia risk (6.33% post-PSM) (1). These findings emphasize the need for meticulous patient selection, advanced imaging, and tailored perioperative strategies. Such expertise, however, is not uniformly available, raising concerns about scalability and implementation for the rest of us.

For the community cardiac surgeon, the feasibility of adopting the Sun procedure is questionable. The technical demands, including prolonged cardiopulmonary bypass and ischemic times, necessitate specialized training and institutional resources. Even with proficiency, the potential for catastrophic complications, such as paraplegia, challenges its wider adoption. I have learned over the years, that when a procedure is done infrequently at hospital, the surgeons should omit their ego and either scrub with another experienced surgeon or defer if safe and possible to send the patient out to a center where such procedures are performed.

Zhu et al. demonstrate no significant difference in 30-day mortality between groups (12.56% Sun vs. 5.38% non-Sun, P=0.06) (1). Similarly, 3-year survival rates (85.02% Sun vs. 91.40% non-Sun, P=0.12) and midterm survival analyses show comparable outcomes. Although the Sun procedure demonstrated a reduction in the incidence of distal aortic events (DAEs), with a 97.17% versus 91.59% freedom from events at three years (P=0.02), the clinical significance of this difference warrants further critical evaluation. Other studies, despite involving smaller cohorts but with longer follow-up periods, have reported higher rates of survival attrition and reinterventions compared to the initial outcomes reported with the Sun procedure. Nevertheless, the results achieved by this group are commendable and inspire considerable interest among clinicians, myself included, to learn from and engage more closely with their team. We eagerly anticipate the forthcoming long-term outcome data on the Sun procedure.

From a practical standpoint, if the Sun procedure does not markedly improve mortality or morbidity, its justification rests on specific scenarios, such as younger patients with Marfan syndrome or complex distal dissections (6-8). For the broader population, simpler approaches may suffice, particularly in lower-resource settings. The study’s findings challenge us to weigh the benefits of potential long-term aortic stability against the increased perioperative risks and resource intensiveness.

For the path forward, several questions arise: should the Sun procedure be reserved for centers of excellence, and how can its technical intricacies be demystified for broader adoption? Moreover, what is the threshold of benefit—in terms of DAE prevention or survival—to justify its use?

Addressing these challenges requires multicenter collaboration, pooling data to validate outcomes and refine indications. Recent meta-analysis confirms the non-inferiority of the FET to the regular Borst Elephant Trunk Enhanced preoperative imaging and risk stratification tools are critical to identifying candidates most likely to benefit from such procedures (9). Additionally, innovation in surgical techniques, such as shorter stents or hybrid approaches, may mitigate complications like paraplegia, making the procedure safer and more accessible.

The Sun procedure, as evaluated by Zhu et al., underscores the complexity of managing ATAAD (1). While it offers potential benefits in reducing DAEs, its lack of definitive survival advantage and high complication risk limit its applicability. For the community cardiac surgeon, simpler alternatives remain a pragmatic choice. Future efforts must focus on refining patient selection, optimizing technique, and expanding data to clarify the Sun procedure’s role. Ultimately, the goal is to balance innovation with feasibility, ensuring that advances in surgical care translate to tangible benefits for patients everywhere.

While there are no randomized trials in this context, other studies including meta-analysis should be brought in for perspective and discussion. Tian et al. (10) and Vernice et al. (11) provide robust evidence on the long-term benefits of the FET technique in complex aortic arch surgery. Tian et al.’s systematic review of 37 studies (4,178 patients) showed favorable survival rates—with 1-, 3-, and 5-year survival at 89.6%, 85.2%, and 82.0%, respectively—and high freedom from reintervention, while maintaining acceptable complication rates. Meanwhile, Vernice et al.’s meta-analysis comparing FET to the conventional elephant trunk (CET) demonstrated that FET yields lower perioperative mortality and improved 1-year survival, though with a higher incidence of endovascular reinterventions. Both studies underscore FET as a safe and effective alternative in the management of aortic arch pathologies, emphasizing its durability and the potential benefits of a more secure landing zone for subsequent endovascular procedures.

In contrast, Zhu et al.’s cohort study focused on ATAAD and compared outcomes between the Sun procedure—a variant of FET combined with total arch replacement—and less extensive repair (1). Zhu et al. found that although the Sun procedure significantly reduced DAEs, it was associated with a higher risk of spinal malperfusion syndrome, and early mortality did not differ significantly between groups. While the systematic reviews by Tian et al. (10) and Vernice et al. (11) highlight the long-term survival advantages and safety profile of FET in a broader, often more chronic aortic pathology setting, Zhu et al. illustrate the trade-offs in an acute, high-risk population, where the aggressive nature of the Sun procedure may offer long-term benefits at the cost of increased perioperative morbidity.

In this context, I would like to remind the reader of the laws of diminishing returns that I studied at school and first formulated by David Ricardo in the early 19th century (12). The law states that as additional input is applied to a fixed resource, the incremental output eventually decreases (see Figure 1). In complex surgery, this principle applies when increasing procedural intricacy, time, and resource use leads to marginal improvements in outcomes while elevating costs, complication risks, and surgeon fatigue. For example, highly specialized cardiac procedures may demand extensive investment in technology and expertise but yield only slight additional patient benefits, with diminishing financial and operational returns. To counteract this, surgical programs should prioritize and consolidate high-yield techniques, optimize case selection, and balance innovation with efficiency to ensure sustainable, value-driven care continues for the foreseeable future.

Figure 1 The graph illustrates the law of diminishing returns, showing how increasing input initially leads to higher output (significant positive surgical outcomes), but at a decreasing rate over time. As input continues to rise (enhanced in surgical technique application), the curve flattens, indicating that additional input contributes progressively less to overall output.

Acknowledgments

None.

Footnote

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