Coinciding with thirty years since the first endovascular repair of the thoracic aorta (TEVAR), performed at Stanford and published in 1994 by Dake et al. for treating a descending thoracic aortic aneurysm, and a decade after the previous guidelines in 2014, the European Association of Cardio-Thoracic Surgery (EACTS), together with the American Society of Thoracic Surgeons (STS), have released new recommendations for diagnosing and treating aortic diseases in a joint guideline. A task force of professionals from both societies developed the document, which was then reviewed and approved by an external panel of global experts, allowing its simultaneous publication in the European Journal of Cardio-Thoracic Surgery and the Annals of Thoracic Surgery. A consensus of this magnitude between the two most influential societies in the field has never been achieved before. Therefore, these guidelines are the result of an extensive quorum, unprecedented to date.
The new guidelines represent a true opus magnum of clinical practice, presented in 195 pages spread over 19 chapters, covering all relevant aspects of aortic diseases and summarized in 36 recommendation tables and 33 figures. Out of 256 recommendations, less than 1% correspond to level A, 26% to level B, and 74% to level C. This reflects that the majority of recommendation classes, which indicate consensus on the effectiveness of a specific intervention, are based primarily on “level C” evidence. Therefore, despite the large number of references cited (983), the studies referred to are largely based on small cohorts, retrospective analyses, and expert opinions.
The document is very extensive and is designed to be consulted on multiple specific occasions. However, attempting to get a global view in one go can be overwhelming. The purpose of this article is to provide a summary of the structure of the guidelines, highlighting the most significant and novel changes compared to previous versions. Thus, readers can take away the key messages and, when they wish to delve deeper into the guidelines, do so in a simpler, more efficient, and enjoyable way.
Below, we break down the most important messages by sections:
The Aorta as an Organ (Nomenclature Change) The guidelines begin with the phrase The obvious is imperceptible until it is perceived, attributed to the philosopher and psychologist William James, where he highlighted how the most obvious things can go unnoticed until someone consciously observes them.
For the first time, the aorta is recognized as an organ that should be interpreted and treated as an independent organ (class IC), becoming the twenty-fourth organ of the human body. The aorta is not simply a conduit for blood flow; it also has a complete functional unit that includes its embryonic origin, tissue structure, and essential function in blood circulation. This comprehensive perspective justifies its recognition as an organ in its own right, beyond its role as a blood vessel.
Specialized Centers and Infrastructure The importance of aortic medicine has grown within health systems due to its economic impact and high complexity. Aortic diseases represent a considerable economic burden, which has been increasing over the past 20 years. For example, the average hospital cost for patients treated for thoracic aortic dissections ($6,102 in medical treatment, $26,896 with endoprosthesis, and $30,372 in surgery) is 50% higher compared to patients hospitalized for other causes after appropriate propensity score analysis, as reflected in some economic studies. Given this context, the guidelines emphasize the importance of forming specialized teams for aortic diseases to effectively address this pathology. Therefore, it is recommended to make joint decisions with an aortic multidisciplinary team (class IC), refer patients with multisegmental or complex aortopathy to specialized centers (class IIa), and have a hybrid operating room available for endovascular procedures (class IC).
They also emphasize the importance of transferring patients with multisegmental aortic disease to “centers of excellence” that have a variety of specialists available with 24/7 coverage. This section is particularly useful for negotiating with and persuading administrations and policymakers about the need for these infrastructures, providing solid arguments.
Classifications, Scales, and Definitions Establishing a common language is essential, so the guidelines have sought to standardize classifications across each segment. In terms of acute aortic dissection, the TEM classification, derived from the TNM system in oncology, has finally been recognized as the cornerstone of indications. Although widely commented on in other blog entries, it’s worth a small reminder: T (type), according to the modified Stanford classification (A for ascending aorta, B for descending aorta, non-A non-B for involvement of the aortic arch with/without descending aorta affecting the ascending aorta). E (entry), according to the location of the entry site (0: undetermined, intramural hematoma; 1: ascending aorta; 2: aortic arch; 3: descending aorta). Lastly, M, presence of malperfusion and at what level: 0: absent; 1: coronary, 2: supra-aortic trunks, 3: visceral, medullary and/or limb; -: no clinical signs or +: with clinical signs). The GERAADA score (already commented on previously in the blog), the first tool to predict 30-day mortality using easily accessible clinical and radiographic data, is also highlighted. Moreover, the non-A, non-B type, affecting only the aortic arch or also the descending aorta, has been standardized as an accepted classification for acute aortic dissection. The extent of the disease and repair are now described using Ishimaru zones (from 0 to 11). As for the bicuspid aortic valve, it has been reclassified to describe it as fused, partially fused, or with two sinuses. The most relevant point is the importance attributed to the morphology of the aorta and the aortic root in patients with a bicuspid aortic valve (and also tricuspid). Depending on the aorta phenotype (type “root” or type “ascending”), the prognosis changes significantly. We recommend reviewing figure 7, which clearly illustrates how patients with a “root” phenotype (5-10% of cases) have a worse prognosis in terms of growth and complications, implying an earlier indication for surgery, more aggressive treatment, and stricter follow-up. Endoleaks: A clear and graphical review of the five types of endoleaks is presented, highlighting that types I and III remain the most important, as they are considered treatment failures and require reintervention. Aortic ulcers and traumatic injuries are clearly illustrated and classified. Additionally, a precise definition of Kommerell’s diverticulum is provided, facilitating its proper management. Grading of hypothermia: A surprising and notable aspect is the effort of the drafting committee to unify the classification of hypothermia, eliminating the confusion existing in the literature about definitions and measurement locations. Four categories have been established: mild hypothermia (above 28 °C), moderate hypothermia subdivided into high moderate (24-28 °C) and low moderate (20-24 °C), and deep hypothermia (below 20 °C). It is important to note that these categories refer to the central body temperature, measured at locations such as the bladder or rectum. Diagnosis and Indications Diagnosis: A key aspect of the guidelines is how measurements should be performed. In angioCT, for example, it is emphasized that measurements should be made from outer diameter to outer diameter. Additionally, for the first time, the length of the aorta is incorporated as a criterion in decision-making, establishing a limit of 11 centimeters from the midline at the level of the aortic ring to the origin of the brachiocephalic trunk. Regarding the measurement of diameter, the approach continues to be to identify the maximum diameter, and it should be measured from sinus to sinus in the aortic root. The measurement of the true lumen, false lumen, and total aorta diameter has also been standardized, especially in postoperative contexts and for the formation of aneurysms.
Surgical Indications in Aortic Dilation: Diameter remains the most discussed component in the guidelines, with cut-off points generally between 5 and 5.5 cm, but with a clear trend towards lower thresholds than in the past. For example, if the surgical risk is low, in bicuspid and tricuspid aortic valves, elective surgery on the ascending aorta (excluding the root) is recommended with class IIa when the diameter reaches 52 mm or more, instead of the previous limit of 55 mm. Additionally, the length of the aorta (>11 cm) and the root phenotype have also been incorporated as variables to consider for surgical indication, suggesting surgery when these factors are present and the diameter exceeds 50 mm.
Management and Treatment One of the great novelties is the inclusion of specific flowcharts for each subtype of acute aortic dissection, definitively clarifying what to do in each circumstance: In type A dissection, the TEM classification guides decisions. In most cases, the recommended surgery is replacement of the ascending aorta and hemiarch, except in specific cases of E2 (if the entry is on the greater curvature) and E3 (if the tear is in the first 10 centimeters from the left subclavian artery), where the frozen elephant trunk (FET) is suggested. In type B acute dissection, medical treatment remains the main option for uncomplicated cases. However, if there are “high-risk features” (already listed in previous blog entries), TEVAR is advised at three months if feasible, or FET if not. For complicated dissections, TEVAR is recommended as an emergency if viable, or FET if not. In other words, emergency intervention is not advised in uncomplicated dissections. In acute non-A non-B dissection, the approach depends on the location of the entry site. If it is in the aortic arch (E2), it generally involves the implantation of a FET, which can be delayed up to 48 hours if it is not a complicated dissection. In the case of an E3, if the dissection is uncomplicated, conservative treatment is the best option, but if it becomes complicated, TEVAR is the treatment of choice, resorting to FET if TEVAR is not viable. The manuscript also addresses in detail the surgical steps in acute dissection, the implantation of FET, the preservation of the root while preserving the valve, and combined vascular and endovascular operations. Additionally, there is an extensive chapter on open thoracoabdominal treatment, with a focus on protecting organs, the spinal cord, viscera, kidneys, and limbs.
Endovascular treatment is also positioned very clearly as a first or second choice in many cases:
TEVAR is the first-line intervention for almost all pathologies affecting the distal arch or descending thoracic aorta. It is especially recommended for the treatment of type B acute aortic dissection complicated and for those with “high-risk features,” ulcers, and traumatic ruptures. It is also supported, with a class IIa recommendation, the stabilization of the membrane (PETTICOAT-type techniques or similar, like the recent AMDS® prosthesis) in acute dissections in cases where adequate decompression of the distal lumen cannot be achieved with TEVAR alone. Endovascular repair of aneurysms with branches or fenestrations is considered equivalent to open surgery for treating thoracoabdominal pathologies (class IIa). As for open surgical treatment, FET becomes the treatment of choice for most diseases of the arch. A class IIa recommendation is offered for acute type A or non-A non-B aortic dissections, type B aortic dissections complicated not suitable for TEVAR, and chronic aortic diseases.
COMMENTARY:
One of the most notable features of these guidelines is the unification of classifications, scores, and definitions, such as the TEM classification, the GERAADA score, the non-A, non-B subtype of aortic dissection, the Ishimaru zones, the morphology of the aortic root, endovascular leaks, and a better understanding of Kommerell’s diverticulum. This unification of language facilitates communication and understanding at a global level, a considerable achievement of these guidelines.
The better natural understanding of aortic diseases has been key to adjusting the surgical indications based on diameter, with a trend towards increasingly lower thresholds. Additionally, for the first time, the length of the aorta is incorporated as an additional criterion in decision-making. These new indications must be incorporated into our daily practice, and they will surely be the subject of repeated consultations by all of us in this new phase.
Another great novelty is the consensus reached on the classification of hypothermia, which will allow comparative studies at the global level with a common language in managing hypothermic circulatory arrest.
The recognition of the aorta as the 24th organ of the human body, along with a better understanding of the importance of effectively managing this high-cost pathology, has driven the creation of specialized centers for complex aortic pathology, equipped with the most advanced therapeutic resources and supported by clinical guidelines. In Spain, a successful example of this strategy is the aorta code in Madrid, whose goal has been to optimize the treatment of acute aortic syndrome in a network of five hospitals. This is achieved through early diagnosis, immediate transfer to the reference center, and treatment by an expert multidisciplinary team. We recently had the opportunity to analyze its results in a blog entry. This is a complex debate, with multiple factors at play, but it will undoubtedly generate a broad global debate, the outcome of which is yet to be seen.
It is necessary to highlight that the main weak point of these guidelines is the low level of evidence that supports many of the recommendations, which deserves constructive criticism. Some proposals from the committee lack solid data support, generating areas of controversy. Among them, the indication for prophylactic surgery in aortas of 45 mm or more in patients with Marfan syndrome, even without high-risk features; the measurement of aortic diameters from outer edge to outer edge instead of from inner edge to inner edge; and the use of moderate to high hypothermia in lower body circulatory arrest, as well as selective antegrade cerebral perfusion in complex arch procedures.
This low level of evidence should serve as an incentive for the aortic community to strive to generate more data through prospective randomized controlled trials. Additionally, it would be valuable to create networks of specialized hospitals that collaborate closely to advance knowledge and improve practices in this field.
In conclusion, we are faced with a highly useful clinical practice guideline for all professionals dedicated to aortic pathology. It stands out not only for its thoroughness but also for its applicability in daily practice, providing great clarity in the new surgical indications for aortic aneurysms, as well as in the flowcharts for the treatment of aortic dissection, fundamentally the non-A non-B type, which until now remained in limbo.
REFERENCE:
Czerny M, Grabenwöger M, Berger T, Aboyans V, Della Corte A, et al.; EACTS/STS Scientific Document Group. EACTS/STS Guidelines for diagnosing and treating acute and chronic syndromes of the aortic organ. Eur J Cardiothorac Surg. 2024 Feb 1;65(2):ezad426. doi: 10.1093/ejcts/ezad426. Erratum in: Eur J Cardiothorac Surg. 2024 Jun 3;65(6):ezae235.
