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Objectives: The American Association for Thoracic Surgery 2010 guidelines stipulate that rapid growth of the aorta (>3 mm/y) is an indication for prophylactic surgical intervention. Because of the many potential sources of error in aortic measurement (including measurement variability and comparison of noncorresponding segments), we explored whether rapid aortic growth was a reality or a falsehood., Methods: Among 2781 patients with aortic disease who were treated over 3 decades, we examined aortic growth rate in 811 patients with at least 2 aortic images taken at least 2 years apart. We identified 42 ascending and 27 descending patients with putative rapid aortic growth. A team of experienced clinicians reread the source images., Results: Among the 42 ascending patients with putative rapid aortic growth, rapid growth was confirmed in 12 and refuted in 11 (19 images nonretrievable). Among the 27 descending patients, rapid growth was confirmed in 6 and refuted in 4 (17 images nonretrievable). We calculated lower, middle, and highest possible rapid growth rates by prorating positivity rates for nonretrievable scans. Lowest, middle, and highest possible rates of rapid growth were 2.7%, 4.7%, and 6.9% for ascending aorta, and 1.6%, 4.3%, and 7.3% for descending aneurysms, respectively. Middle rates are considered most accurately reflective. Of the patients with confirmed rapid growth, 3 of 4 inoperable patients succumbed to their aorta. Twenty-three patients underwent prompt surgery, with 22 survivors. For the rapidly growing aortas, operative, pathologic, and genetic findings are reported., Conclusions: Although not a falsehood, rapid growth is uncommon for the ascending and descending aorta. Many putative cases are reflective of measurement error. Attention to potential sources of measurement error is key. VIDEO ABSTRACT., (Copyright © 2022 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.)

Aims: This study aims to outline the 'true' natural history of ascending thoracic aortic aneurysm (ATAA) based on a cohort of patients not undergoing surgical intervention., Methods and Results: The outcomes, risk factors, and growth rates of 964 unoperated ATAA patients were investigated, over a median follow-up of 7.9 (maximum of 34) years. The primary endpoint was adverse aortic events (AAE), including dissection, rupture, and aortic death. At aortic sizes of 3.5-3.9, 4.0-4.4, 4.5-4.9, 5.0-5.4, 5.5-5.9, and ≥6.0 cm, the average yearly risk of AAE was 0.2%, 0.2%, 0.3%, 1.4%, 2.0%, and 3.5%, respectively (P < 0.001), and the 10-year survival free from AAE was 97.8%, 98.2%, 97.3%, 84.6%, 80.4%, and 70.9%, respectively (P < 0.001). The risk of AAE was relatively flat until 5 cm of aortic size, at which it began to increase rapidly (P for non-linearity <0.001). The mean annual growth rate was estimated to be 0.10 ± 0.01 cm/year. Ascending thoracic aortic aneurysms grew in a very slow manner, and aortic growth over 0.2 cm/year was rarely seen. Multivariable Cox regression identified aortic size [hazard ratio (HR): 1.78, 95% confidence interval (CI): 1.50-2.11, P < 0.001] and age (HR: 1.02, 95% CI: 1.00-1.05, P = 0.015) as significant independent risk factors for AAE. Interestingly, hyperlipidemia (HR: 0.46, 95% CI: 0.23-0.91, P = 0.025) was found to be a significant protective factor for AAE in univariable Cox regression., Conclusion: An aortic size of 5 cm, rather than 5.5 cm, may be a more appropriate intervention criterion for prophylactic ATAA repair. Aortic growth may not be an applicable indicator for intervention., Competing Interests: Conflict of interest J.E. serves as the principal of CoolSpine and consultant for Tissium. All other authors report no conflict of interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Ascending thoracic aortic dissection (ATAD) is a well-known vascular cause of sudden death. Spontaneous coronary artery dissections (SCAD) are emerging as an important cause of early-onset myocardial infarction and sudden death. Genetic variants in multiple connective tissue genes have been recognized to underlie ATAD; other genetic variants have similarly been recognized to underlie SCAD. Little data are available regarding any genetic commonality between ATAD and SCAD. Our objective is to determine and characterize any genetic overlap between genes coding for ATAD and SCAD. We identified and reviewed 17 retrospective and prospective genetic studies of thoracic aortic dissection and SCAD published between 2016 and 2022 identified through PubMed and Orbis. Articles highlighting the significant plausible triggers for ATAD or SCAD individually were analyzed. No previous study reviewed both ATAD and SCAD genetics together. Separate lists of causative genes were constructed for ATAD and SCAD-and then commonalities were sought. A Venn diagram was constructed to display the genetic overlap and common physiologic pathways involved. We identified a definite, meaningful overlap of 15 independent genes based on a genome-wide association study or other genetic methods. The associated genetic pathways involved various biologic processes including elastin degradation, smooth muscle cell function, and the TGFβ-pathway. The overlapping genes included the following: COL3A1, TGFB2, SMAD3, MYLK, TGFBR2, TGFBR1, LOX, FBN1, NOTCH1, ELN, COL5A1, COL5A2, COL1A2, MYH11, and TLN1. The corresponding molecular pathways were investigated and correlated for both diseases. We are not aware of other studies searching for genetic commonalities between ATAD and SCAD. We have successfully identified overlapping genes-and their corresponding molecular pathways-for ATAD and SCAD. We hope that these insights will lead to further clinical and scientific understanding of each disease through study of their fundamental commonalities., Competing Interests: Declaration of Competing Interest Dr Elefteriades is a principal of CoolSpine and reports a relation that includes equity or stocks. The remaining authors have no competing interests to declare., (Copyright © 2023 Elsevier Inc. All rights reserved.)

This issue of the Yale Journal of Biology and Medicine ( YJBM ) focuses on Big Data and precision analytics in medical research. At the Aortic Institute at Yale New Haven Hospital, the vast majority of our investigations have emanated from our large, prospective clinical database of patients with thoracic aortic aneurysm (TAA), supplemented by ultra-large genetic sequencing files. Among the fundamental clinical and scientific discoveries enabled by application of advanced statistical and artificial intelligence techniques on these clinical and genetic databases are the following: From analysis of Traditional "Big Data" (Large data sets) . 1. Ascending aortic aneurysms should be resected at 5 cm to prevent dissection and rupture. 2. Indexing aortic size to height improves aortic risk prognostication. 3. Aortic root dilatation is more malignant than mid-ascending aortic dilatation. 4. Ascending aortic aneurysm patients with bicuspid aortic valves do not carry the poorer prognosis previously postulated. 5. The descending and thoracoabdominal aorta are capable of rupture without dissection. 6. Female patients with TAA do more poorly than male patients. 7. Ascending aortic length is even better than aortic diameter at predicting dissection. 8. A "silver lining" of TAA disease is the profound, lifelong protection from atherosclerosis. From Modern "Big Data" Machine Learning/Artificial Intelligence analysis : 1. Machine learning models for TAA: outperforming traditional anatomic criteria. 2. Genetic testing for TAA and dissection and discovery of novel causative genes. 3. Phenotypic genetic characterization by Artificial Intelligence. 4. Panel of RNAs "detects" TAA. Such findings, based on (a) long-standing application of advanced conventional statistical analysis to large clinical data sets, and (b) recent application of advanced machine learning/artificial intelligence to large genetic data sets at the Yale Aortic Institute have advanced the diagnosis and medical and surgical treatment of TAA., (Copyright ©2023, Yale Journal of Biology and Medicine.)

Background: Aortic diameter at time of dissection remains an indispensable risk-determining characteristic for prophylactic repair of thoracic aortic aneurysms. Histograms of aortic size at the time of dissection have the potential to shed more light on this relationship., Methods: Size of the thoracic aorta at the time of dissection was determined from imaging of 407 naturally occurring, acute, flap-type ascending or descending aortic dissections treated at 1 institution (1990-2022). Histograms were constructed to depict aortic size at the time of dissection. Data were analyzed by logistic regression., Results: There were 170 (69.11%) of 246 type A dissections (median, 5.07 cm; interquartile range, 4.60-5.67 cm) and 130 (80.75%) of 161 type B dissections (median, 4.2 cm; interquartile range, 3.60-4.87 cm) that occurred at diameters <5.5 cm. By unadjusted regression, factors associated with significantly increased odds of type A dissection at diameters <5.5 cm were female sex (odds ratio [OR], 2.06; P = .023), hypertension (OR, 1.82; P = .036), and smoking (OR, 1.92; P = .029). Patients with bicuspid aortic valve had significantly decreased odds of type A dissection at diameters <5.5 cm (OR, 0.3; P = .047). The recent "left shift" to 5.0 cm in the criterion for ascending aortic intervention could prevent an additional 29.3% of type A dissections., Conclusions: Aortic diameter at the time of type A dissection is consistent with the new guidelines that recommend surgical intervention at 5.0 cm. Type B dissection occurs at small sizes and cannot be prevented with a size criterion., (Copyright © 2023 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

We examined the long-term fate of the preserved aortic root after emergent repair of acute Type A aortic dissection. 144 patients (60% males, mean age 60.5 years) underwent supracoronary ascending aortic replacement for acute Type A aortic dissection. Long-term survival, as well as growth, reoperation, and adverse events of the aortic root (rupture, pseudoaneurysm, and persistent dissection) were retrospectively assessed. Operative mortality was 9%, and overall survival at 1, 5, and 10 years was 87.8%, 76.4%, and 64.6%, respectively. Reoperation on the proximal aorta was performed in 16 patients (12.2%) within a median of 2.45 years post-operatively. Indications were severe aortic insufficiency (AI) (n = 6), aortic root pseudoaneurysm (n = 8), pseudoaneurysm with severe AI (n = 1), and persistent dissection with severe AI (n = 1). The aortic root grew at 0.2mm/year (interquartile range 0-0.8). Among survivors (n = 131), 28 patients (21.3%) reached aortic root diameter ≥ 45 mm (mean diameter 47.6 mm, range 45-54 mm). Survival free from proximal aortic reoperation at 1, 5, and 10 years was 96.6%, 94.5%, and 92.2%, respectively. No non-reoperated patient-despite persistent, unoperated enlargement or distortion or pseudoaneurysm of the aortic root-developed free rupture or fistula to a cardiac chamber. Root-sparing ascending aortic replacement for acute Type-A aortic dissection showed satisfactory long-term outcomes with relatively low rates of re-intervention or serious aortic root adverse events despite dilatation and irregularity of aortic root contour. Dense adhesions from prior surgery, proximal aortic suture line, and Teflon felt seem to discourage free rupture or fistulization., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Thoracic aortic aneurysm is typically clinically silent, with a natural history of progressive enlargement until a potentially lethal complication such as rupture or dissection occurs. Underlying genetic predisposition strongly influences the risk of thoracic aortic aneurysm and dissection. Familial cases are more virulent, have a higher rate of aneurysm growth, and occur earlier in life. To date, over 30 genes have been associated with syndromic and non-syndromic thoracic aortic aneurysm and dissection. The causative genes and their specific variants help to predict the disease phenotype, including age at presentation, risk of dissection at small aortic sizes, and risk of other cardiovascular and systemic manifestations. This genetic "dictionary" is already a clinical reality, allowing us to personalize care based on specific causative mutations for a substantial proportion of these patients. Widespread genetic sequencing of thoracic aortic aneurysm and dissection patients has been and continues to be crucial to the rapid expansion of this dictionary and ultimately, the delivery of truly personalized care to every patient.

Background Data from the International Registry of Acute Aortic Dissection indicate that the guideline criterion of 5.5 cm for ascending aortic intervention misses many dissections occurring at smaller dimensions. Furthermore, studies of natural behavior have generally treated the aortic root and the ascending aorta as 1 unit despite embryological, anatomical, and functional differences. This study aims to disentangle the natural histories of the aforementioned aortic segments, allowing natural behavior to define specific intervention criteria for root and ascending segments of the aorta. Methods and Results Diameters of the aortic root and mid-ascending segment were measured separately. Long-term complications (dissection, rupture, and death) were analyzed retrospectively for 1162 patients with ascending thoracic aortic aneurysm. Cox regression analysis suggested that aortic root dilatation ( P =0.017) is more significant in predicting adverse events than mid-ascending aortic dilatation ( P =0.087). Short stature posed as a serious risk factor. The dedicated risk curves for the aortic root and the mid-ascending aorta revealed hinge points at 5.0 and 5.25 cm, respectively. Conclusions The natural histories of the aortic root and mid-ascending aorta are uniquely different. Dilation of the aortic root imparts a significant higher risk of adverse events. A diameter shift for intervention to 5.0 cm for the aortic root and to 5.25 cm for the mid-ascending aorta should be considered at expert centers.

Background: This study evaluates sex differences in the natural history of descending thoracic and thoracoabdominal aortic aneurysms (DTTAAs)., Methods: In all, 907 patients with descending thoracic and thoracoabdominal aortic sizes greater than 3 cm were retrospectively reviewed. Growth rate estimates were performed utilizing an instrumental variables approach. Yearly complication rates as a function of aortic size were computed., Results: There were 615 men (67.8%) and 292 women (32.2%) treated between 1990 and 2018, with mean aortic diameters of 4.1 ± 1.4 cm and 4.8 ± 1.6 cm, respectively (P < .001). The mean growth rate of DTTAAs was 0.17 cm per year in men and 0.25 cm per year in women (P < .001), increasing with increasing aneurysm size. Dissection, rupture, or aortic death or the combination of the three occurred at double the rate for women compared with men (5.8% vs 2.3% per year for the combined endpoint). Diameter of DTTAA greater than 5 cm was associated with 26.3% (male) and 33.1% (female) average yearly rates of the composite endpoint of rupture, dissection, and death (P < .05). The probability of fatal complications (rupture and death) increased sharply at 5.75 cm in both sexes. Between 4.5 and 5.75 cm, there was another hinge-point of higher probability of fatal complications among women., Conclusions: Women diagnosed with DTTAA fare worse. Faster aneurysm growth and higher rates of dissection, rupture, and aortic death are apparent among women. Current guidelines recommend surgical intervention at 5.5 to 6 cm for DTTAAs without sex considerations. Our findings suggest that increased virulence of DTTAA in women may indicate surgery at a somewhat smaller diameter., (Copyright © 2021 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

Background: The purpose of this study was to examine whether chronologic and climatic factors and lunar phases affect the onset of acute aortic dissection (AAD)., Methods: The frequencies of AAD were analyzed with regard to the chronologic and climatic factors and lunar phases on the day when AAD occurred for 1642 patients with AAD from two aortic referral centers in the United States and China., Results: Mean age of patients was 51.6 ± 13.1 years, and 1260 (76.7%) were men. Dissection was type A in 1125 patients (68.5%) and type B in 517 (31.5%). Early mortality rate was 11.6% (190 of 1642), including 89 aortic ruptures before operation and 101 operative deaths. There was a winter peak in occurrence (33.6%, P < .01) with a relative risk of 1.519. In a week, the frequency was highest on Wednesday (15.5%) and Monday (15.2%), and lowest on Sunday (12.8%). Month-specific incidence was significantly inversely correlated to the mean temperature (rho = -0.650, P = .022) and directly correlated to the atmospheric pressure (rho = 0.706, P = .001). The proportion of type A dissection was significantly higher in the full moon phase compared with type B dissection (73.7% vs 66.9%, P = .012)., Conclusions: Acute aortic dissection exhibits significant chronologic variation in the frequency of occurrence, with a peak in winter and on Wednesdays, and nadir in summer and on Sundays. The incidence is significantly correlated to the mean temperature and atmospheric pressure. The proportion of type A dissection is higher in the full moon phase. These results are important for understanding the mechanisms involved in triggering AAD events and helpful for improving disease prevention and patient care., (Copyright © 2020 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

Objectives: Our goal was to outline the clinical presentations, surgical treatment and outcomes of subacute/chronic type A aortic dissection (TAAD)., Methods: A total of 1092 patients with TAAD were enrolled retrospectively and divided into 2 groups based on acuity of TAAD (181 subacute/chronic vs 911 acute cases of TAAD). Early and late outcomes were investigated and compared using propensity score matching., Results: The top 3 symptoms for subacute/chronic TAAD were chest tightness (80/181, 44.2%), mild pain (65/181, 35.9%) and sweating (58/181, 32.0). Fifteen (15/181, 8.3%) patients were symptom-free. Typical symptoms of acute TAAD were less common in patients with subacute/chronic TAAD such as intense/sharp pain (48/181, 26.5%), tear-like pain (35/181, 19.3%) and radiating pain (30/181, 16.6%). Patients with subacute/chronic TAAD had better early and late survival rates, with an early mortality rate of 6.1% (11/181) compared to 11.6% (106/911) of those with acute TAAD (P = 0.038). Before propensity score matching, survival at 1, 3 and 5 years was 93.1% [95% confidence interval (CI) 89.4-96.9%], 88.4% (95% CI 83.1-93.9%) and 86.4% (95% CI 80.1-93.1%) for subacute/chronic TAAD and 86.9% (95% CI 84.7-89.2%), 82.6% (95% CI 79.9-85.3%) and 79.0% (95% CI 75.5-82.7%) for acute TAAD, respectively (P = 0.039). The propensity score matching analysis substantiated the foregoing results., Conclusions: Subacute/chronic TAAD was clearly distinct from acute TAAD in terms of clinical presentations and had better early and late survival rates. Current surgical strategies for acute TAAD are applicable to subacute/chronic TAAD with excellent outcomes., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Thoracic aortic aneurysm and dissection (TAAD) affects many patients globally and has high mortality rates if undetected. Once thought to be solely a degenerative disease that afflicted the aorta due to high pressure and biomechanical stress, extensive investigation of the heritability and natural history of TAAD has shown a clear genetic basis for the disease. Here, we review both the cellular mechanisms and clinical manifestations of syndromic and non-syndromic TAAD. We particularly focus on genes that have been linked to dissection at diameters <5.0 cm, the current lower bound for surgical intervention. Genetic screening tests to identify patients with TAAD associated mutations that place them at high risk for dissection are also discussed.

Objective: The risk of rupture and dissection in ascending thoracic aortic aneurysms increases as the aortic diameter exceeds 5 cm. This study evaluates the clinical effectiveness of a specific algorithm based on size and symptoms for preemptive surgery to prevent complications., Methods: A total of 781 patients with nondissecting ascending thoracic aortic aneurysms who presented electively for evaluation to our institution from 2011 to 2017 were triaged to surgery (n = 607, 77%) or medical observation (n = 181, 24%) based on a specific algorithm: surgery for large (>5 cm) or symptomatic aneurysms. A total of 309 of 781 patients did not undergo surgery. Of these, 128 (16%) had been triaged to prompt repair but did not undergo surgery for a variety of reasons ("surgery noncompliant and overwhelming comorbidities" group). Another 181 patients (24%) were triaged to medical management ("medical" group)., Results: In the "surgery noncompliant and overwhelming comorbidities" versus the "medical" group, mean aortic diameters were 5 ± 0.5 cm versus 4.45 ± 0.4 cm and aortic events (rupture/dissection) occurred in 17 patients (13.3%) versus 3 patients (1.7%), respectively (P < .001). Later elective surgeries (representing late compliance in the "surgery noncompliant and overwhelming comorbidities group" or onset of growth or symptoms in the "medical" group) were conducted in 21 patients (16.4%) versus 15 patients (8.3%) (P = .04), respectively. Death ensued in 20 patients (15.6%) versus 6 patients (3.3%) (P < .001), respectively. In the "surgery noncompliant and overwhelming comorbidities" group, 7 of 20 patients died of definite aortic causes compared with none in the "medical" group., Conclusions: Patients with ascending thoracic aortic aneurysms who did not follow surgical recommendations experienced substantially worse outcomes compared with medically triaged candidates. The specific algorithm based on size and symptoms functioned effectively in the clinical setting, correctly identifying both at-risk and safe patients., (Copyright © 2018 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.)

Nonsyndromic thoracic aortic aneurysm and dissection (TAAD) account for 95% of all TAAD cases and comprise a subset in which the lack of obvious clinical signs makes diagnosis a challenge. Despite the potentially fatal natural history, timely diagnosis and prophylactic surgical intervention allow restoration of near-normal life expectancy in TAAD patients, underlining the critical importance of screening tests. To date, more than 30 TAAD disease-causing genes have been identified, and over 30% of nonsyndromic TAAD patients have a genetic mutation in 1 or more of these genes. Whole exome sequencing allows routine genetic testing in a clinical setting by screening for all TAAD-related genes, thus facilitating personalized aortic care. Additionally, increased vigilance upon diagnosis of certain TAAD-related diseases ("guilty associates") and the emergence of modern radiologic and novel serologic screening tests will further bolster efforts to detect undiagnosed asymptomatic nonsyndromic TAAD., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Thoracic aortic aneurysm (TAA) is an increasingly recognized condition that is often diagnosed incidentally. This review discusses ten of the most relevant epidemiological and clinical secrets of this disease; (1) the difference in pathogenesis between ascending and descending TAAs. TAAs at these two sites act as different diseases, which is related to the different embryologic origins of the ascending and descending aorta. (2) The familial pattern and genetics of thoracic aneurysms. Syndromic TAAs only explain 5% of the pattern of inheritance. (3) The effect of female sex on TAA growth and outcome. Females have been found to have worse outcomes compared to males. (4) Guilt by Association. TAAs are associated with abdominal aortic aneurysms, intracranial aneurysms, bicuspid aortic valve, and inflammatory disorders. (5) Natural history of TAAs. Important findings have been made regarding the expansion rate (in relation to familial pattern, location and size), and also regarding the risk of rupture or dissection. (6) The aortic size paradox. Size only is not a sufficient predictor of risk of dissection. (7) Biomarker void. Although many serum biomarkers have been studied, imaging remains the only reliable method for diagnosis and follow-up. (8) Indications for repair. Decisions are made depending on symptoms, location, size, and familial patterns. (9) Types of repair. Both open and endovascular repair options are available for certain TAAs. (10) Medical treatment. The efficacy of prescribing beta blockers, angiotensin converting enzyme inhibitors or angiotensin receptor blockers remains dubious.

Background: Multiple studies have quantified the relationship between aortic size and risk of dissection. However, these studies estimated the risk of dissection without accounting for any increase in aortic size from the dissection process itself., Objectives: This study aims to compare aortic size before and after dissection and to evaluate the change in size consequent to the dissection itself., Methods: Fifty-five consecutive patients (29 type A; 26 type B) with aortic dissection and incidental imaging studies prior to dissection were identified and compared to a control group of aneurysm patients (n = 205). The average time between measurement at and prior to dissection was 1.7 ± 1.9 years (1.9 ± 2.0 years mean inter-image time in the control group). A multivariate regression model controlling for growth rate, age, and gender was created to estimate the effect of dissection itself on aortic size., Results: The mean aortic sizes at and prior to dissection were 54.2 ± 7.0 and 45.1 ± 5.7 mm for the ascending aorta, and 47.1 ± 13.8 and 39.5 ± 13.1 mm for the descending aorta, respectively. The multivariable analysis revealed a significant impact of the dissection itself (p < 0.001) and estimated an increase in size of 7.65 mm (ascending aorta) and 6.38 mm (descending aorta). Thus, a proportional estimate of 82.8% (ascending aorta) and 80.8% (descending aorta) of dissections are made at a size lower than the guideline-recommended threshold (55 mm)., Conclusions: The aortic diameter increases substantially due to aortic dissection itself and, thus, aortas are being dissected at clinically meaningfully smaller sizes than natural history analyses have previously suggested. These findings have important implications regarding the size at which the risk of dissection is increased., (© 2018 S. Karger AG, Basel.)

Objectives: Although family members of patients with aortic dissection (AoD) are believed to be at higher risk of AoD, the prognostic value of family history (FH) of aortic dissection (FHAD) in family members of patients with AoD has not been studied rigorously. We seek examine how much a positive FHAD increases the risk of developing new aortic dissection (AoD) among first-degree relatives., Methods: Patients with AoD at our institution were analyzed for information of FHAD. Positive FHAD referred to that AoD occurred in index patient and one or more first-degree relatives. Negative FHAD was defined as the condition in which only one case of AoD (the index patient) occurred in the family. The age at AoD, exposure years in adulthood before AoD, and annual probability of AoD among first-degree relatives were compared between patients with negative and positive FHADs., Results: FHAD was positive in 32 and negative in 68 among the 100 AoD patients with detailed family history information. Mean age at dissection was 59.9±14.7years. Compared to negative FHAD, patients with positive FHAD dissected at significantly younger age (54.7±16.8 vs 62.4±13.0years, p=0.013), had more AoD events in first-degree relatives (2.3±0.6 vs 1.0±0.0, p<0.001), and shorter exposure years per AoD event (18.3±6.7 vs 43.1±8.5, p<0.001). Annual probability of AoD per first-degree relative was 2.77 times higher in patients with positive than negative FHADs (0.0100±0.0057 vs 0.0036±0.0014, p<0.001)., Conclusions: A positive FHAD confers a significantly increased risk of developing aortic dissection on family members, with a higher annual probability of aortic dissection, a shorter duration of "exposure time" before dissection occurs and a lower mean age at time of dissection., (Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.)