Aortic Enlargement Location and Type A Dissection Risk

Quick Takes

  • Using data from the IRAD registry, among patients with acute type A aortic dissection (ATAD) but maximal aortic diameter (MAD) <5.5 cm, predominant aortic dilation was in the ascending aorta (AA) in ~80% of patients and in the aortic root (AR) in ~20% of patients.
  • However, the MAD at the time of ATAD was smaller among patients in the AR group (4.6 cm [IQR 4.1-5.0 cm]) compared to patients in the AA group (4.8 cm [IQR 4.4-5.1 cm], p < 0.01).

Study Questions:

Among patients with modest aortic dilation, does the location of the dilated segment affect the risk of acute type A aortic dissection (ATAD)?


Using the IRAD (International Registry of Acute Aortic Dissection) database from May 1996–October 2016, 667 ATAD patients with maximal aortic diameter (MAD) <5.5 cm were identified. Patients were stratified by location of the largest proximal aortic segment (aortic root [AR] or supracoronary ascending aorta [AA]). Patients with known genetically triggered aortopathy were excluded. MAD at time of dissection was compared between AR and AA groups. Secondary outcomes included operation, postoperative outcomes, and long-term survival.


Of patients with ATAD at MAD <5.5 cm, 79.5% (n = 530) were in the AA group and 20.5% (n = 137) in the AR group. Modestly dilated ARs (median MAD 4.6 cm [IQR 4.1-5.0 cm]) dissected at a significantly smaller diameter than modestly dilated AAs (median MAD 4.8 cm [IQR 4.4-5.1 cm]; p < 0.01). AR patients were significantly younger than AA patients (58.5 ± 13.0 years vs. 63.2 ± 13.3 years; p < 0.01) and more commonly male (78% vs. 65%; p < 0.01). Postoperative and long-term outcomes did not differ between groups.


ATAD appears to occur at smaller diameters in patients with modest dilation in the AR compared to the AA (4.6 vs. 4.8 cm). The authors concluded that these findings may have implications for future consensus guidelines regarding the management of patients with aortic disease.


Ascending aorta dilation is a risk factor for ATAD; in the absence of a family history of aortic dissection or a recognized genetic aortopathy, a threshold MAD of ≥5.5 cm is used to recommend prophylactic surgical intervention. However, a large proportion of patients who present with ATAD have a MAD <5.5 cm, raising the question of whether higher-risk patients with only moderate aortic dilation can be identified. This study using data from the IRAD registry found that approximately 80% of patients with ATAD and MAD <5.5 cm had predominant dilation of the AA compared to approximately 20% with predominant dilation of the AR, but that ATAD appeared to occur at a small MAD among patients with predominant dilation in the AR. Although it is possible that confounding factors could exist in this large, retrospective, administrative database, including the possible existence of patients with an undiagnosed genetic aortopathy, the study might help inform future efforts to better guide surveillance and intervention for patients with ascending aortic aneurysm but without an existing indication for prophylactic surgical intervention.

Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Vascular Medicine, Aortic Surgery, Cardiac Surgery and Arrhythmias, Interventions and Imaging, Interventions and Vascular Medicine

Keywords: Aneurysm, Dissecting, Aorta, Aortic Aneurysm, Thoracic, Aortic Diseases, Cardiac Surgical Procedures, Diagnostic Imaging, Dilatation, Dissection, Risk Factors, Secondary Prevention, Vascular Diseases

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