The recently published article Unplanned coronary artery bypass graft in aortic root replacement (European Journal of Cardio-Thoracic Surgery) evaluates the clinical relevance of requiring an unplanned coronary artery bypass graft (CABG) during aortic root replacement (ARR). This event typically arises from technical difficulties during coronary button reimplantation, a pivotal step in root reconstruction. The study explores the consequences of this complication and identifies associated risk factors.

This retrospective analysis includes all patients undergoing ARR between 2004 and 2021 at two major US aortic centers (Columbia University and Emory University). From an initial cohort of 2701 individuals, cases with planned CABG for known atherosclerotic coronary artery disease were excluded, resulting in a final population of 2416 patients. These were divided into two groups: ARR without CABG (n = 2212) and ARR with unplanned CABG (n = 204; 8.4%).

To evaluate the clinical impact of unplanned CABG, the investigators used propensity score matching (2:1 ratio) to compare ARR alone versus ARR with unplanned CABG in patients with balanced baseline characteristics. After matching, unplanned CABG was associated with higher rates of in-hospital mortality (21.2% vs 8.2%), stroke (8.4% vs 2.5%), renal failure (18.2% vs 10.6%) and respiratory complications (49.3% vs 27.2%). Survival analyses also revealed a significant reduction in both early (90-day) and long-term survival among patients requiring unplanned CABG.

In multivariable analysis, several independent predictors of unplanned CABG emerged: female sex, chronic kidney disease, reoperation, aortic dissection, endocarditis and concomitant arch replacement. Conversely, valve-sparing root replacement (VSRR) was associated with a lower likelihood of this complication.

COMMENTARY:

The work by Rajesh et al. addresses a well-recognized yet insufficiently characterized complication in aortic root replacement (ARR): the need for unplanned coronary artery bypass grafting (CABG) following difficulties during coronary button reimplantation. One of the first findings that stands out is the comparatively high incidence reported (8.4%), which is noticeably greater than that described in the two prior series available: Shahriari et al. from Yale (2.2% in 139 patients) and Ogami et al. from Pittsburgh (4.3% in 795 patients). Although the authors attribute this rise largely to their broader definition of the phenomenon, the concept of unplanned CABG itself is fairly straightforward. A more plausible interpretation for this discrepancy may lie in the differing proportions of operative indications—namely acute dissection, endocarditis and aneurysm—across the cohorts. Each clinical scenario carries a distinct technical burden for coronary reimplantation, which can significantly influence the risk of button-related complications. Notably, the Yale cohort had a very low proportion of dissections and endocarditis (approximately 11%), whereas the two more recent, larger cohorts—particularly the present study—include far more complex pathologies. As a result, the “true” incidence of this complication likely falls within the 4–8% range. Ultimately, the incidence is a somewhat imprecise surrogate, as it reflects both institutional technical proficiency and the inherent complexity of the surgical case mix.

Although unplanned CABG has been previously described, this investigation provides the strongest evidence to date that its occurrence is associated with significantly worse perioperative outcomes. The propensity-matched analysis demonstrates higher rates of stroke, renal failure, respiratory failure and in-hospital mortality compared with isolated ARR. These observations are physiologically coherent: managing an unexpected coronary button problem inevitably prolongs cardiopulmonary bypass (CPB) and aortic cross-clamp times, increasing exposure to myocardial ischemia and systemic inflammatory stress. In this series, the unplanned CABG group required, on average, an additional 85 minutes of CPB and 49 minutes of cross-clamp. Established literature confirms the direct relationship between prolonged CPB times and adverse neurologic, renal and respiratory outcomes, suggesting that a large portion of the observed morbidity may stem from time-related injury rather than the CABG procedure per se. Curiously, no postoperative markers of myocardial ischemia were reported—data that might have helped discern the specific contribution of coronary compromise to early outcomes. Previous studies that failed to show increased morbidity in unplanned CABG groups were likely underpowered: given the operative delays inherent to rescue CABG, larger populations are needed to detect clinically meaningful differences.

The intraoperative mechanisms leading to rescue CABG are described with a classification that is both practical and clinically intuitive: (1) anatomic limitations or tissue friability (39.7%), (2) compromised flow after button anastomosis (38.2%), (3) malperfusion resulting from aortic dissection (16.2%) and (4) direct coronary injury (6%). This framework underscores the heterogeneous nature of the complication and suggests that not all unplanned CABG carries the same prognostic weight. For instance, extreme tissue frailty in the context of connective tissue disorders, reoperations or acute dissections likely portends a different risk profile compared with a torsion-related flow issue during elective aneurysm repair. A stratified analysis based on these mechanisms might clarify whether certain etiologies have a disproportionate impact on outcomes.

The multivariable analysis reinforces the role of underlying tissue integrity in the genesis of unplanned CABG. Acute dissection and endocarditis—both associated with structurally compromised buttons—emerge as strong predictors, as does reoperation, which introduces additional challenges related to scarring, adhesions and altered anatomy. The associations with female sex and chronic kidney disease (CKD) are more nuanced. For women, the authors propose anatomic differences, although direct evidence is lacking. A more likely explanation relates to the generally smaller aortic root and coronary artery dimensions observed in female patients—an association supported by prior series, including the Pittsburgh experience, where a body surface area <1.7 m² was linked to higher CABG risk. CKD, for its part, is consistent with known patterns of impaired tissue quality and vascular fragility.

Interestingly, surgeon experience did not emerge as an independent predictor, though the threshold used (>5 ARR procedures/year) is arguably insufficient to differentiate high-volume aortic specialists from occasional root surgeons. This limitation likely diluted the measurable impact of operator experience.

Valve-sparing root replacement (VSRR) appears as a protective factor, though this observation must be interpreted cautiously. The protective effect almost certainly reflects patient selection—VSRR candidates are generally younger, with healthier tissues and fewer urgent or emergent indications—rather than any inherent advantage of the technique. The involvement of more experienced surgeons in VSRR programs may further contribute to this association.

Regarding limitations, the retrospective design is inherent to the nature of this complication, which is difficult to study prospectively given its unpredictability. One notable omission is the exclusion of surgical “status” from the propensity model due to collinearity concerns; however, a separate analysis differentiating elective versus urgent/emergent settings would have been clinically informative, particularly since urgent presentations disproportionately involve conditions that predispose to button failure. Another unaddressed issue concerns the long-term implications of relying on a single conduit—often a saphenous vein graft—anastomosed proximally to a Dacron graft, a configuration prone to accelerated intimal hyperplasia. Moreover, the study does not specify whether left coronary system failures were managed with one or two grafts; using only an LAD graft may insufficiently perfuse the lateral wall, raising the possibility of residual ischemia.

Overall, the work by Rajesh et al. reinforces that unplanned CABG during ARR is not merely an intraoperative mishap but a clear marker of operative complexity and worse prognosis. A more refined understanding of the mechanisms leading to rescue CABG may help develop preventive strategies and improve outcomes in this highly demanding area of aortic surgery.

REFERENCE:

Rajesh K, Chung M, Levine D, Hohri Y, Norton E, Patel P et al. Unplanned coronary artery bypass graft in aortic root replacement. Eur J Cardiothorac Surg 2025;67(7):ezaf193. doi:10.1093/ejcts/ezaf193

Shahriari A, Eng M, Tranquilli M, Elefteriades JA. Rescue coronary artery bypass grafting (CABG) after aortic composite graft replacement. J Card Surg. 2009;24(4):392-6. doi:10.1111/j.1540-8191.2008.00762.x.

Ogami T, Serna-Gallegos D, Yousef S, Brown JA, Thoma FW, Subramaniam K, et al. The clinical significance of unplanned coronary artery bypass grafting in aortic root replacement. J Cardiothorac Vasc Anesth. 2024;38(4):918-23. doi: 10.1053/j.jvca.2024.01.001.