Modernizing Aortic Dissection Classification in the Era of Endovascular and Hybrid Repair: Implications for Radiology Reporting

Abstract

Accurate classification of aortic dissection is essential for guiding clinical treatment and facilitating communication between radiologists and clinicians. Traditional classifications, such as the DeBakey and Stanford systems, categorize dissections according to their origin and extent, or by involvement of the ascending aorta. The Stanford classification has gained widespread use due to its clear correlation with the surgical and medical treatments available at the time. However, these traditional classifications provide limited guidance for contemporary management, particularly in the era of endovascular and hybrid surgical techniques for aortic repair. Modern classifications, such as the Type/Entry/Malperfusion (TEM) system and Type B dissection reporting standards proposed by the Society for Vascular Surgery and the Society of Thoracic Surgeons (SVS/STS), incorporate more detailed anatomic and clinical descriptors. The TEM system expands upon the Stanford classification by adding a “non-A non-B” category for arch dissections and incorporating entry tear and malperfusion descriptors. The SVS/STS classification introduces a zone-based model that defines the dissection type by the location and extent of the entry tear. Contemporary guidelines have identified several high-risk imaging features that predict poor outcomes in otherwise uncomplicated dissections. This pictorial review compares these classifications and highlights their implications for radiologic reporting, emphasizing how detailed anatomic and risk-based descriptors better align radiologic interpretations with contemporary management strategies.

INTRODUCTION

Aortic dissection is a life-threatening emergency requiring prompt diagnosis and precise characterization. Computed tomography (CT) angiography is the imaging modality of choice for confirming the diagnosis, mapping the disease extent [1,2,3], and detecting complications, high-risk features, or associated cardiac anomalies [4]. Classification plays a pivotal role not only in treatment selection but also in facilitating clear communication between clinicians and radiologists. Over the past century, multiple classification systems have been proposed, each reflecting anatomical priorities and therapeutic strategies. Although the Stanford classification remains the most widely used system because of its simple binary scheme, contemporary management increasingly requires more detailed anatomical information. This pictorial review compares these systems, aligns them with major clinical guidelines, highlights key implications for radiologic reporting, and proposes a structured reporting framework.

OVERVIEW OF CLASSIFICATION SYSTEMS

The DeBakey classification, introduced in 1965, categorizes dissections into three types—Type I, II, and III—based on the location of the entry tear and the extent of dissection, and also describes the preferred surgical approaches to manage each dissection type (Fig. 1) [5].

Fig. 1. DeBakey classification by site of entry tear and extent of dissection. Type I dissections originate in the ascending aorta and extend to the descending aorta. Type II dissections originate in and are confined to the ascending aorta. Type III dissections originate in and are confined to the descending aorta. The surgical approaches available at that time were described for each type.

The Stanford classification, introduced in 1970, simplifies the DeBakey classification into two categories based on the involvement of the ascending aorta. Type A dissections involve the ascending aorta, whereas Type B dissections are limited to the descending aorta, regardless of entry tear location or distal extent (Fig. 2) [6]. The key insight was that involvement of the ascending aorta necessitated urgent surgical management, whereas uncomplicated Type B dissections are typically managed with initial medical therapy unless complications arise. Because of its simplicity and clear therapeutic implications, the Stanford system has gained widespread adoption.

Fig. 2. Stanford classification by the most proximal extent of dissection. Type A dissections involve the ascending aorta. The entry tear may originate in the ascending aorta or more distally in the aortic arch or descending aorta, with retrograde extension of the dissection into the ascending aorta.

However, both traditional classifications predate advanced imaging-based assessments of aortic dissection and modern therapeutic techniques such as thoracic endovascular aortic repair (TEVAR) and frozen elephant trunk (FET) procedures. Therefore, they lack the anatomical precision necessary for contemporary treatment planning. Neither system accounts for isolated arch dissections that spare the ascending aorta, leading to ambiguity in the classification and management of such cases. These limitations have prompted the development of modern systems that provide more granular descriptors.

The Type/Entry/Malperfusion (TEM) classification, introduced in 2019, defines the type of dissection according to its most proximal extent in the ascending aorta (Type A), arch (non-A non-B), or descending aorta (Type B). The entry tear location and malperfusion are described and recorded separately. This expands upon the Stanford classification by introducing a new “non-A non-B” category to capture dissections involving the arch but sparing the ascending aorta (Fig. 3) [7]. The new “non-A non-B” category, previously unclassifiable, accounts for 2%–11% of all dissections [8].

Fig. 3. TEM classification. Type classification is by the most proximal extent of the dissection: Type A involves the ascending aorta, non-A non-B involves the arch, and Type B involves only the descending aorta. Entry tears are recorded depending on their anatomical location: in the ascending aorta (E1), arch (E2), descending aorta (E3), or if not identified (E0). Likewise, radiologic evidence of malperfusion is recorded depending on which branch vessels are involved. TEM = Type/Entry/Malperfusion.

The latest classification system proposed by the Society for Vascular Surgery and Society of Thoracic Surgeons (SVS/STS) in 2020 is based on the Ishimaru zonal anatomy, which was originally developed to guide endovascular aortic interventions. The Ishimaru zones divide the aorta into 11 zones of attachment, each corresponding to potential landing sites for stent grafts (Fig. 4) [9]. Zone 0 comprises the ascending aorta and origin of the brachiocephalic artery. In contrast to the Stanford and TEM classifications, the SVS/STS classification defines the dissection type primarily by entry tear location (Fig. 5) [10]. Type A dissections are defined as having an entry tear in zone 0, whereas Type B dissections are defined as having an entry tear in zone 1 or beyond. The extent of dissection is described by listing the most proximal and distal affected zones as subscripts. As the Ishimaru zones are already integrated into TEVAR planning, this system is particularly intuitive for interventionists. This classification formally defines dissection chronicity, dividing it into hyperacute (<24 hours), acute (<14 days), subacute (15–90 days), and chronic (>90 days) phases, which have been adopted in multiple guidelines [1,3,10].

Fig. 4. Ishimaru zonal anatomy divides the aorta into 11 zones. Of note, zone 0 comprises the ascending aorta and the proximal arch up to the origin of the brachiocephalic artery, while zones 1 and 2 correspond to the rest of the aortic arch. Zone 3 is the proximal segment of the descending aorta within 2 cm of the origin of the left subclavian artery, and an entry tear in this location is considered a high-risk imaging feature. SMA = superior mesenteric artery.

Fig. 5. SVS/STS classification by the site of the entry tear and extent of dissection based on Ishimaru zonal anatomy. Dissections with the entry tear in zone 0 are considered Type A, while dissections with the entry tear in zones 1 or beyond are considered Type B. The most proximal and distal extents of the dissection are indicated as subscripts. If the dissection involves the ascending aorta but the entry tear is not identified, it is termed Type I. SVS = Society for Vascular Surgery, STS = Society of Thoracic Surgeons.

There is considerable overlap in terminology among the different classifications regarding how they define the dissection type (Fig. 6). DeBakey Types I and II correspond to Stanford A and Type A in modern (SVS/STS, and TEM) classifications (Figs. 7, 8), whereas DeBakey Type III corresponds to Stanford B and Type B in modern classifications (Fig. 9).

Fig. 6. Comparative overview of the different classification systems for aortic dissection. The systems share Type A/B terminology but define these types differently. SVS = Society for Vascular Surgery, STS = Society of Thoracic Surgeons, TEM = Type/Entry/Malperfusion, TEVAR = thoracic endovascular aortic repair.

Fig. 7. 87-year-old woman with Type A dissection (Case 1). A, B: Axial (A) and sagittal oblique CT (B) images show an aortic dissection with the entry tear (*) in the ascending aorta, extending to the abdominal aorta (not shown). C: Axial CT image at the level of the supra-aortic vessels shows extension into the brachiocephalic (red arrow), left common carotid (yellow arrow), and left subclavian (green arrow) arteries. The TL of the brachiocephalic artery is collapsed. D: Schematic illustration of dissection extent and entry tear (*). This would be classified as DeBakey I and Type A under the Stanford, SVS/STS, and TEM classifications. CT = computed tomography, TL = true lumen, SVS = Society for Vascular Surgery, STS = Society of Thoracic Surgeons, TEM = Type/Entry/Malperfusion, FL = false lumen.

Fig. 8. 78-year-old woman with Type A dissection complicated by hemopericardium (Case 2). A, B: Axial (A) and sagittal oblique CT (B) images show an aortic dissection with the entry tear (*) and dissection confined to the ascending aorta. C: Axial CT shows extension of the dissection into the origin of the brachiocephalic artery (arrow). D: Axial non-contrast CT at the level of the lower thorax shows high-attenuation pericardial fluid (arrows) consistent with hemopericardium. The pericardium encloses the ascending aorta, and hemopericardium is a sign of aortic rupture into the pericardial space. E: Schematic illustration of dissection extent and entry tear (*). This would be classified as DeBakey II and Type A under the Stanford, SVS/STS, and TEM classifications. CT = computed tomography, SVS = Society for Vascular Surgery, STS = Society of Thoracic Surgeons, TEM = Type/Entry/Malperfusion, FL = false lumen, TL = true lumen.

Fig. 9. 58-year-old woman with Type B dissection complicated by mediastinal hematoma (Case 3). A: Axial CT image shows an aortic dissection with the entry tear (*) in the descending aorta. B: Sagittal oblique CT image shows the entry tear measuring 19 mm (double arrow line). The dissection extends to the common iliac arteries (not shown). C: Coronal oblique CT image orthogonal to the long axis of the aorta shows a maximal aortic diameter of 42 mm (double arrow line) and a FL diameter of 18 mm (dashed double arrow line). D: Axial non contrast CT image at the lower thorax shows a mediastinal hematoma (red arrow) and left hemorrhagic pleural effusion (yellow arrow). In contrast to Case 2, the descending aorta is not covered by the pericardium, and rupture results in blood entering the mediastinal and pleural spaces instead of the pericardial space. E: Schematic illustration of dissection extent and entry tear (*). This would be classified as DeBakey III and Type B under the Stanford, SVS/STS, and TEM classifications. CT = computed tomography, FL = false lumen, SVS = Society for Vascular Surgery, STS = Society of Thoracic Surgeons, TEM = Type/Entry/Malperfusion, TL = true lumen.

Nevertheless, important discrepancies across the classification systems exist, as Stanford and TEM typing are based primarily on the most proximal extent of the dissection, whereas SVS/STS typing is based on the site of entry tear. Consequently, a dissection with an entry tear in the descending aorta and retrograde propagation into the ascending aorta would be classified as Type B in the SVS/STS classification but as Type A in the Stanford and TEM classifications (Fig. 10).

Fig. 10. 77-year-old man with Type A dissection from retrograde propagation of an entry tear in the descending aorta (Case 4). A, B: Axial (A) and sagittal oblique CT (B) images show an aortic dissection with the entry tear (*) in the descending aorta, retrogradely propagating to involve the ascending aorta (red arrows). The dissection extends into the superior mesenteric artery (yellow arrow). C: Axial CT image of the abdominal aorta shows dissection of the superior mesenteric artery (yellow arrow) and right renal artery (red arrow), resulting in right kidney nonenhancement. D: Schematic illustration of dissection extent and entry tear (*). This would be classified as Type B under the SVS/STS classification, but Type A under the Stanford and TEM classifications. It is not classified under the DeBakey classification. CT = computed tomography, SVS = Society for Vascular Surgery, STS = Society of Thoracic Surgeons, TEM = Type/Entry/Malperfusion, FL = false lumen, TL = true lumen.

Aortic arch dissections sparing the ascending aorta (not defined by the DeBakey and Stanford classifications) are defined by the TEM classification as “non-A non-B”–the entry tear can be located anywhere in the arch or descending aorta. However, in the SVS/STS classification, arch dissections, as defined above, can fall under either Type A if the entry tear is at the level of the brachiocephalic artery (Ishimaru zone 0 or proximal arch) or Type B if the entry tear is in Ishimaru zones 1 or 2 (Figs. 11, 12). The overlap between distal zone 0 and the proximal aortic arch can result in a discrepant categorization of the same dissection, whereas the latter Type B classification undermines the clinical significance of arch dissection. Arch involvement (non-A non-B) often has a worse prognosis than Type B dissections, requiring tailored, aggressive management, such as FET.

Fig. 11. 46-year-old woman with non-A non-B dissection originating from the arch (Case 5). A, B: Axial (A) and sagittal oblique CT (B) images show an aortic dissection with the entry tear (*) at the origin of the LSA, measuring 5 mm in size. The dissection extends to the internal and external iliac arteries (not shown). C: Axial CT image of the supra-aortic vessels shows dissection involving the LCC (yellow arrow) and LSA (green arrow). D: Axial CT image of the descending aorta shows a maximal aortic diameter of 25 mm (double arrow line) and a FL diameter of 12 mm (dashed double arrow line). E: Schematic illustration of dissection extent and entry tear (*). This would be classified as Type B under the SVS/STS classification, but non-A non-B under the TEM classification. It is not classified under the DeBakey or Stanford classifications. CT = computed tomography, LSA = left subclavian artery, LCC = left common carotid artery, FL = false lumen, SVS = Society for Vascular Surgery, STS = Society of Thoracic Surgeons, TEM = Type/Entry/Malperfusion, TL = true lumen.

Fig. 12. 73-year-old man with non-A non-B dissection originating from the origin of the BCA (Case 6). A, B: Axial (A) and sagittal oblique CT (B) images show an aortic dissection with a large semi-circumferential entry tear (*) at the inner curvature of the aortic arch segment at the level of the BCA origin. C: Axial CT image shows a FL diameter of 25 mm (dashed double arrow line), with near-complete collapse of the TL. D: Axial CT image at the level of the abdominal aorta shows dissection into the left renal artery (red arrow), resulting in left renal malperfusion. There is also dissection of the superior mesenteric artery (yellow arrow). E: Schematic illustration of dissection extent and entry tear (*). This would be classified as Type A under the SVS/STS classification, but non-A non-B under the TEM classification. It is not classified under the DeBakey or Stanford classifications. BCA = brachiocephalic artery, CT = computed tomography, FL = false lumen, TL = true lumen, SVS = Society for Vascular Surgery, STS = Society of Thoracic Surgeons, TEM = Type/Entry/Malperfusion.

A summary figure panel shows how the six case examples were classified differently by each system (Fig. 13).

Fig. 13. Summary figure panel comparing all six case examples by dissection extent, entry tear location, and classification under each system. The “M” category from the TEM classification has been omitted for ease of comparison. TEM = Type/Entry/Malperfusion, SVS = Society for Vascular Surgery, STS = Society of Thoracic Surgeons.

IMPLICATIONS FOR RADIOLOGIC REPORTING

Although classification systems provide conceptual frameworks, radiologic reports must translate imaging findings into clear, management-relevant descriptors. The following elements should be systematically addressed:

Chronicity

Chronicity should be explicitly stated, as it influences both prognosis and management strategies. In accordance with the SVS/STS classification and multiple clinical guidelines, classification into hyperacute (<24 hours), acute (<14 days), subacute (15–90 days), and chronic (>90 days) phases should be based on correlation with prior imaging, clinical documentation, and patient history. CT findings that support chronic dissection include thickened and straightened intimal flaps that may also be calcified [11].

Type Classification

Despite the limitations of the Stanford classification, it remains practical for rapid communication in emergency settings and interdisciplinary discussions, thereby serving as a common clinical shorthand upon which modern classifications are layered. Regarding modern classifications, the Type component of the TEM classification is more intuitive for clinical communication, as anatomical details guide management and intervention planning. The SVS/STS classification has greater relevance in clinical studies and registries. Therefore, we recommend harmonizing reporting terminology by adopting the Type component of the TEM classification and describing the most proximal extent of dissection when it extends into the ascending aorta (Type A) or arch (non-A non-B). Dissections sparing the ascending aorta and arch should be classified as Type B.

This classification directly reflects the differences in clinical urgency and therapeutic complexity. Type B dissections may be managed with optimal medical therapy, with TEVAR reserved for complicated cases or for those with high-risk features. Non-A non-B dissections often carry greater complexity and worse prognosis than Type B dissections and require hybrid techniques (TEVAR with extra-anatomic bypass or arch replacement with FET) for repair. Type A dissections represent the most immediately life-threatening category and warrant emergent ascending aorta replacement with or without arch replacement [1,2]. By explicitly stating the proximal extent of dissection, radiologists convey not only the anatomy but also the relative severity and anticipated treatment pathways.

Entry Tear Location

The site of the proximal entry tear should be systematically identified based on the Ishimaru zones. This can be slightly difficult when the tear is small or obscured by cardiac motion artifacts. However, it remains a key finding as resection and sealing of the proximal entry tear are the goals of surgical repair and TEVAR, respectively.

In Type B dissections, the proximity of the entry tear to the supra-aortic branches presents specific anatomical challenges for TEVAR. The distance from the entry tear to the left subclavian artery is clinically relevant for endovascular planning and should be measured. When an adequate proximal landing zone cannot be achieved without compromising perfusion to the supra-aortic branches, endovascular repair may be precluded or require adjuncts, such as chimney grafting or custom-made devices. In addition, entry tears in the lesser curvature or in Ishimaru zone 3 are recognized as independent high-risk imaging features [2,12].

Complications

Dissections are considered complicated when there is evidence of aortic rupture or end-organ malperfusion. Aortic rupture may manifest on CT as a hemopericardium, mediastinal hematoma, and/or hemothorax, and should be urgently communicated to the clinical team.

Patients with malperfusion syndromes often present with clinical manifestations such as neurological deficits with supra-aortic involvement, biochemical derangements including lactic acidosis, or symptoms of end-organ ischemia involving the kidney, bowel, and/or lower limbs [13]. On CT, malperfusion is suspected when there is evidence of reduced vessel opacification, delayed or absent end-organ enhancement (e.g., asymmetric renal enhancement [14], bowel hypoenhancement), or true lumen collapse of the branch vessel.

When branch vessel compromise is identified, it is important to differentiate whether there is a static or dynamic obstruction, as this impacts management (Fig. 14). A dissection flap extending into the branch vessel results in persistent true lumen collapse (static flap). In the presence of the corresponding clinical manifestations, stenting of the true lumen in the branch vessel must be considered to restore flow. In the case of dynamic obstruction, the mobile dissection flap in the aorta prolapses intermittently to occlude the origin of the branch vessel. Dynamic obstruction is treated medically with blood pressure control and repair of the primary entry tear(s) to prevent flap mobility.

Fig. 14. Illustration of a cross-sectional view of the aorta showing static and dynamic obstruction of branch vessels. A: Static obstruction occurs when the flap extends into the branch vessel. B: Dynamic obstruction occurs when the flap prolapses, occluding the ostium of the branch vessel. C: Both static and dynamic obstructions can occur simultaneously.

Extension of the dissection into the iliac arteries with true lumen collapse or thrombosis and absent distal opacification can lead to clinically significant limb ischemia [12,15]. Such cases require urgent intervention with true lumen cannulation and stenting, failing which, bypass may be considered.

Branch vessels that remain patent may be supplied by the true or false lumen and should be described appropriately.

High-Risk Features

For both uncomplicated non-A non-B and Type B dissections, several high-risk imaging features have been associated with an increased risk of aneurysmal degeneration, rupture, or delayed intervention, and there is increasing evidence that early endovascular repair should be considered over medical therapy to reduce long-term morbidity and mortality in this patient group [16,17,18,19]. Clear and concise reporting of these high-risk features in radiology reports influences clinical management (Table 1) [1,2,3,10,20]. Notable examples of high-risk imaging features include a maximal aortic diameter >40 mm or a maximal false lumen diameter >22 mm. The standardized method for measuring the diameter of the aorta and false lumen is perpendicular to the aortic centerline [1,2,3,21]. The false lumen diameter is measured from the inner wall of the false lumen to the intimal flap (Figs. 9C, 11D, 12C, 15) [12,22].

Table 1. High-risk imaging features in non-A non-B and Type B dissections. Radiologic-only malperfusion refers to imaging evidence of malperfusion in the absence of corresponding clinical signs or symptoms.

Diameter measurements	Entry tear	Other
Aortic diameter >40 mm	Entry tear >10 mm	Hemorrhagic pleural effusion
False lumen diameter >22 mm	Entry tear at inner curvature	Radiologic-only malperfusion
Increase in total aortic diameter >5–10 mm/year	Entry tear <20 mm to left subclavian artery (zone 3)	Partial false lumen thrombosis

Fig. 15. Illustration of a cross section of an aortic dissection showing the TL, FL, maximal aortic diameter (double arrow line), and FL diameter (dashed double arrow line). Measurements are performed on planes orthogonal to the aortic centerline to avoid inaccuracies due to obliqueness on standard axial planes. TL = true lumen, FL = false lumen.

STRUCTURED REPORTING TEMPLATE

We outlined a suggested structured reporting template that can be incorporated into routine CT reports and includes all the aforementioned radiologic findings relevant to aortic dissection (Table 2). A sample report for Case 6 is provided as an example.

Table 2. Suggested structured reporting template incorporating the type classification, entry tear location, and other clinically relevant information. A sample report using details from Case 6 is provided.

Suggested reporting template		Case example
Chronicity: [Hyperacute (<24 hours)/Acute (<14 days)/Subacute (15–90 days)/Chronic (>90 days)]		Chronicity: Hyperacute (<24 hours)
Type: [A/non-A non-B/B]		Type: non-A non-B
Extent (most proximal and distal zones):		Extent (most proximal and distal zones): 0–9
Primary Entry Tear: [Ascending aorta/Arch/Descending aorta]		Primary Entry Tear: Arch
Zone: [zone of entry tear]		Zone: 0; brachiocephalic origin
	• Distance of entry tear from LSA (mm):		• Distance of entry tear from LSA (mm): NA
	• Tear Size (mm):		• Tear Size (mm): Large semi-circumferential tear 20 mm
Complications/Malperfusion:		Complications/Malperfusion:
• Hemopericardium: [Yes/No]; [Free text]		• Hemopericardium: No
• Periaortic Hematoma: [Yes/No]; [Free text]		• Periaortic Hematoma: No
• Coronary Arteries: [Patent/Involved]; [Free text]		• Coronary Arteries: Patent
• Supra-aortic Branches: [Patent/Involved]; [Free text]		• Supra-aortic Branches: Patent
• Visceral Arteries: [Patent/Involved]; [Free text]		• Visceral Arteries: Involved
			- SMA static obstruction, supplied by TL
			- Left renal artery static obstruction, supplied by FL
• Iliac Vessels: [Patent/Involved]; [Free text]		• Iliac Vessels: Patent
• Other: [Free text, e.g., aortic true lumen collapse, renal malperfusion]		• Other
			- Near complete collapse of descending aorta true lumen
			- Left renal malperfusion
High-risk Imaging Features (applicable to non-A non-B and Type B dissections):		High-risk Imaging Features (applicable to non-A non-B and Type B dissections):
• Maximal Aortic Diameter (mm):		• Maximal Aortic Diameter (mm): 27 mm
• Increase in total aortic diameter >5–10 mm/year: [Yes/No/NA]; [Measurement]		• Increase in total aortic diameter >5–10 mm/year: NA
• Maximal False Lumen Diameter (mm):		• Maximal False Lumen Diameter (mm): 25 mm
• Entry Tear >10 mm: [Yes/No]; [Measurement]		• Entry Tear >10 mm: Yes
• Entry Tear at the inner curvature: [Yes/No]		• Entry Tear at the inner curvature: Yes
• Partial False Lumen Thrombosis: [Yes/No]		• Partial False Lumen Thrombosis: No
• Hemorrhagic pleural effusion: [Yes/No]		• Hemorrhagic pleural effusion: No

SMA = superior mesenteric artery

CONCLUSION

Radiologists are essential in translating imaging findings into clinically actionable information. Modern aortic dissection classification systems highlight key descriptors—extent of dissection, entry tear location, malperfusion, and high-risk features—that inform management strategies. By integrating these precise and clinically meaningful anatomical details into structured reports, radiologists contribute substantively to multidisciplinary decision-making, moving beyond simply assigning a traditional label such as the Stanford or DeBakey classification. Adopting a proximal extent–based Type classification and using TEM’s expanded “non-A non-B” category, when applicable, while clearly documenting entry tear location, complications, and high-risk features, bridges the gap between traditional nomenclature and contemporary interventions. This structured, management-oriented reporting framework strengthens interdisciplinary communication and facilitates tailored, evidence-based care for patients with aortic dissection.