Aortic arch involvement worsens the prognosis of type B aortic dissections

Differences in In-Hospital and Follow-Up Outcomes Between Non-A Non-B Aortic Dissection and Type B Aortic Dissection Treated by Endovascular Based Treatment

OBJECTIVES

Non-A non-B aortic dissection (AD) is a rare and life-threatening medical emergency, and it has been controversial whether it should be managed as type B aortic dissection (TBAD). The study aims to compare in-hospital and follow-up outcomes between patients with non-A non-B AD and those with TBAD treated by endovascular based treatment (EBT).

METHODS

From January 2017 to December 2021, 96 consecutive patients with non-A non-B AD met the inclusion criteria and underwent EBT. Patients with TBAD were matched to patients with non-A non-B AD at a 1:1 ratio using propensity score matching analysis to correct for baseline confounding factors. The primary endpoint was all-cause mortality. Aortic-related events were defined as dissection-related death, aortic rupture, retrograde type A aortic dissection, reintervention, and type Ia endoleak.

RESULTS

Patients with non-A non-B AD required more TEVAR-related adjunctive procedures compared to TBAD patients during EBT and they required a longer ICU length of stay (36.0 vs 24.0 hours, P < .05) as well as a longer hospitalization (8.0 vs 7.0 days, P < .05) after EBT. There was no statistical difference in overall survival after EBT for patients with TBAD and non-A non-B AD. However, compared to patients with TBAD, non-A non-B AD patients had a higher rate of reintervention and experienced more aortic-related late events during follow-up.

CONCLUSION

Patients with non-A non-B acute AD who are treated with EBT do not have higher in-hospital or follow-up mortality rates compared to patients with type B AD. However, there is an increased risk of reintervention and aortic-related late events after the intervention during follow-up.

Non-A Non-B Acute Aortic Dissection: Is There Some Confusion in the Radiologist's Mind?

BACKGROUND

The aim of this study is to define and determine the rate of acute non-A-non-B aortic dissections, and to evaluate CT angiography findings and possible complications, as well as to discuss management strategies and currently available therapy. Non-A non-B type of aortic dissection is still a grey area in the radiologist's mind, such that it is not entirely clear what should be reported and completed in terms of this disease.

METHODS

A retrospective single-center study including 36 pre-treatment CT angiograms of consecutive patients (mean age: 61 years) between January 2012 and December 2022 with aortic dissection involving the aortic arch with/without the thoracic descending/abdominal aorta (type non-A non-B).

RESULTS

According to the dissection anatomy, we identified three modalities of spontaneous acute non-A-non-B anatomical configurations. Configuration 1 (n = 25) with descending-entry tear and retrograde arch extension (DTA entry). Configuration 2 (n = 4) with Arch entry tear and isolated arch involvement (Arch alone). Configuration 3 (n = 7) with Arch entry and anterograde descending (±abdominal) aorta involvement (Arch entry). CT angiogram findings, management, and treatment options are described.

CONCLUSIONS

Acute non-A non-B dissection represents an infrequent occurrence of aortic arch dissection (with or without involvement of the descending aorta) that does not extend to the ascending aorta. The complete understanding of its natural progression, distinct CT angiography subtypes, optimal management, and treatment strategies remains incomplete. Within our series, patients frequently exhibit a complex clinical course, often necessitating a more assertive approach to treatment compared to type B dissections.

Current knowledge and contemporary management of non-A non-B aortic dissections

Non-A non-B aortic dissection (AAD) is an infrequently documented condition, comprising of only a small proportion of all AADs. The unique anatomy of the aortic arch and the failure of the existing classifications to adequately define individuals with non-A non-B AAD, have led to an ongoing controversy around the topic. It seems that the clinical progression of acute non-A non-B AAD diverges from the typical type A and B dissections, frequently leading to serious complications and thus mandating early intervention. Currently, the available treatment methods in the surgical armamentarium are conventional open, endovascular techniques and combined hybrid methods. The optimum approach is tailored in every individual case and may be determined by the dissection’s location, extent, the aortic diameter, the associated complications and the patient’s status. The management of non-A non-B dissections still remains challenging and a unanimous consensus defining the gold standard treatment has yet to be reached. In an attempt to provide further insight into this perplexing entity, we performed a minireview of the literature, aiming to elucidate the epidemiology, clinical course and the optimal treatment modality.

Surgical treatment patterns and clinical outcomes of type B aortic dissection involving the aortic arch

OBJECTIVE

In the present report, we have described the outcomes of endovascular repair, hybrid arch repair, and open surgical repair for type B dissection involving the aortic arch (B_{1-2, D}).

METHODS

Cases of endovascular repair, hybrid arch repair, and open surgical repair performed between January 2015 and December 2019 for aortic dissection designated as B_{1-2, D} by the Society for Vascular Surgery/Society of Thoracic Surgeons classification were retrospectively analyzed. The primary end point was all-cause mortality at follow-up. The secondary end points included early mortality, early morbidities, and aortic-related late events. Kaplan-Meier curves were created to analyze survival from all-cause mortality and freedom from aortic-related late events in the endovascular, hybrid, and open groups. Propensity score matching and stratification (stratified by proximal dissection extension: B_{1, D} and B_{2, D}) were performed as sensitivity analyses to compare the outcomes among the three treatment patterns after controlling for major confounders.

RESULTS

The present study included 151 patients (men, 79.5%; mean age, 47.3 ± 10.5 years), with 72 (47.7%) in the endovascular group, 46 (30.5%) in the hybrid group, and 33 (21.8%) in the open group. No significant difference was noted in early mortality between the endovascular, hybrid, and open groups (1.4% vs 2.2% vs 3.0%; P = .791). The incidence of early endoleak was significantly greater (33.3% vs 13.0% vs 6.1%; P = .002) and the incidence of renal function deterioration was less (4.2% vs 26.1% vs 24.2%; P = .001) after endovascular repair vs hybrid arch repair and open surgery. After a median follow-up of 40.0 months (range, 0-84.0 months), no significant differences were found in all-cause mortality (5.6% vs 4.3% vs 3.0%; P = 1.0), aortic-related late events (16.7% vs 15.2% vs 12.1%; P = .834), or late endoleak (9.7% vs 4.3% vs 6.1%; P = .630) after endovascular, hybrid, and open surgery. The propensity score matching and stratification analyses displayed consistent outcomes for early mortality, all-cause mortality, and aortic-related late events among the three groups.

CONCLUSIONS

The mid- to long-term outcomes after endovascular repair, hybrid arch repair, and open surgical repair for type B dissection involving the aortic arch (B_{1-2, D}) were favorable and comparable in selected patients. Extensive experience and multidisciplinary teamwork are prerequisites for individualized strategies for repair of B_{1-2, D}.

Triple-Branched Stent Graft Implantation for Acute Non-A-non-B Aortic Dissection

BACKGROUND

The optimal treatment for acute non-A-non-B aortic dissection remains controversial. Triple-branched stent graft (TBSG) implantation has been used to treat acute type A aortic dissection. This study aimed to evaluate the safety and efficacy of TBSG as a treatment for acute non-A-non-B aortic dissection.

METHODS

Fifty patients with non-A-non-B dissection received TBSG implantation in our center between January 2014 and December 2019. Early mortality, morbidity, and dissected aorta remodeling during follow-up were calculated.

RESULTS

There were no deaths in-hospital or within 30 days. Postoperative complications included pneumonia (n = 12), acute kidney injury (n = 6; preoperative renal malperfusion, n = 4), transient cerebral injury (n = 6; preoperative cerebral malperfusion, n = 4), pleural effusion (n = 4), and pericardial effusion (n = 2). During follow-up, 1 patient experienced a stroke, and 2 patients required secondary interventional therapy for residual dissection below the level of the TBSG. All implanted TBSGs had good positioning, and all sidearm stent graft grafts were fully patent. No retrograde aortic dissection or type I endoleak was detected.

CONCLUSIONS

TBSG implantation for acute non-A-non-B aortic dissection had a low incidence of mortality and morbidity, featuring good remodeling of the dissected aortic wall during follow-up. The early outcomes of this technique were satisfactory.

Aortic dissection with epileptic seizure: A case report

BACKGROUND

Aortic dissection (AoD) is a life-threatening disease. Its diversified clinical manifestations, especially the atypical ones, make it difficult to diagnose. The epileptic seizure is a neurological problem caused by various kinds of diseases, but AoD with epileptic seizure as the first symptom is rare.

CASE SUMMARY

A 53-year-old male patient suffered from loss of consciousness for 1 h and tonic-clonic convulsion for 2 min. The patient performed persistent hypomania and chest discomfort for 30 min after admission. He had a history of hypertension without regular antihypertensive drugs, and the results of his bilateral blood pressure varied greatly. Then the electroencephalogram showed the existence of epileptic waves. The thoracic aorta computed tomography angiography showed the appearance of AoD, and it originated at the lower part of the ascending aorta. Finally, the diagnosis was AoD (DeBakey, type I), acute aortic syndrome, hypertension (Grade 3), and secondary epileptic seizure. He was given symptomatic treatment to relieve symptoms and prevent complications. Thereafter, the medical therapy was effective but he refused our surgical advice.

CONCLUSION

The AoD symptoms are varied. When diagnosing the epileptic seizure etiologically, AoD is important to consider by clinical and imaging examinations.

Management and Outcomes of Non-A Non-B Aortic Dissection

OBJECTIVE

The results of best medical treatment (BMT), endovascular based treatment (EBT), and total arch replacement (TAR) with frozen elephant trunk (FET) treatment in a single centre experience were reported in non-A non-B aortic dissection patients.

METHODS

From January 2016 to May 2020, 215 consecutive patients with acute or subacute non-A non-B aortic dissection were enrolled. The primary endpoints were all cause death. Secondary endpoints included follow up adverse aortic event (AE), a composite of the outcomes of dissection related death, rupture, retrograde type A aortic dissection, stent graft induced new entry tear, secondary endoleak, and follow up re-intervention. Kaplan-Meier curves were used to evaluate associations between different treatments and outcomes.

RESULTS

Among the 215 dissection patients, 127 (59.1%) received EBT, 42 (19.5%) received TAR + FET, and the remaining 46 (21.4%) received BMT. Thirty day mortality was higher in patients receiving TAR + FET (7.1%) than in those treated with EBT (1.6%) or BMT (2.2%) (p = .12). However, after a median follow up of 39.1 (27.0 - 50.7) months, no additional death was recorded in the TAR + FET group, while nine (7.3%) patients died in the EBT group and 14 (31.8%) died in the BMT group (p < .001). Specifically, EBT and TAR + FET showed no significant difference in midterm mortality rate, follow up AE, and re-intervention for complicated or uncomplicated dissection patients involving zone 2. For patients with uncomplicated non-A non-B aortic dissection involving zone 2, EBT could profoundly decrease the mortality rate, follow up AE and re-intervention when compared with BMT (p < .010 for all), although this difference was not statistically significant between TAR + FET and BMT. No statistical comparison was performed in patients with zone 1 involvement because of the limited number of patients.

CONCLUSION

It was demonstrated that EBT or TAR + FET might be a viable strategy for non-A non-B aortic dissection patients.

MDCT Imaging of Non-Traumatic Thoracic Aortic Emergencies and Its Impact on Diagnosis and Management—A Reappraisal

Non-traumatic thoracic aorta emergencies are associated with significant morbidity and mortality. Diseases of the intimomedial layers (aortic dissection and variants) have been grouped under the common term of acute aortic syndrome because they are life-threatening conditions clinically indistinguishable on presentation. Patients with aortic dissection may present with a wide variety of symptoms secondary to the pattern of dissection and end organ malperfusion. Other conditions may be seen in patients with acute symptoms, including ruptured and unstable thoracic aortic aneurysm, iatrogenic or infective pseudoaneurysms, aortic fistula, acute aortic thrombus/occlusive disease, and vasculitis. Imaging plays a pivotal role in the patient’s management and care. In the emergency room, chest X-ray is the initial imaging test offering a screening evaluation for alternative common differential diagnoses and a preliminary assessment of the mediastinal dimensions. State-of-the-art multidetector computed tomography angiography (CTA) provides a widely available, rapid, replicable, noninvasive diagnostic imaging with sensitivity approaching 100%. It is an impressive tool in decision-making process with a deep impact on treatment including endovascular or open surgical or conservative treatment. Radiologists must be familiar with the spectrum of these entities to help triage patients appropriately and efficiently. Understanding the imaging findings and proper measurement techniques allow the radiologist to suggest the most appropriate next management step.

Management of Ascending Aorta and Aortic Arch: Similarities and Differences Among Cardiovascular Guidelines

BACKGROUND

Ascending aorta and aortic arch diseases have an increasing interest among cardiovascular specialists regarding diagnosis and management. Innovations in endovascular surgery and evolution of open surgery have extended the indications for treatment in patients previously considered unfit for surgery. The aim of this systematic review of the literature was to present and analyze current cardiovascular guidelines for overlap and differences in their recommendations regarding ascending aorta and aortic arch diseases and the assessment of evidence.

METHODS

The English medical literature was searched using the MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials databases from January 2009 to December 2020. Recommendations on selected topics were analyzed, including issues from definitions and diagnosis (imaging and biomarkers) and indications for treatment to management, including surgical techniques, of the most important ascending aorta and aortic arch diseases.

RESULTS

The initial search identified 2414 articles. After exclusion of duplicate or inappropriate articles, the final analysis included 5 articles from multidisciplinary, cardiovascular societies published between 2010 and 2019. The definition of non-A-non-B aortic dissection is lacking from most of the guidelines. There is a disagreement regarding the class of recommendation and level of evidence for the diameter of ascending aorta as an indication. The indication for treatment of aortic disease may be individualized in specific cases while the growth rate may also affect the decision making. The role of endovascular techniques has not been established in current guidelines except by 1 society. Supportive evidence level in the management of aortic arch diseases remains limited.

CONCLUSION

In current recommendations of cardiovascular societies, the ascending aorta and aortic arch remain a domain of open surgery despite the introduction of endovascular techniques. Recommendations of the included societies are mostly based on expert opinion, and the role of endovascular techniques has been highlighted only from 1 society. The chronological heterogeneity apparent among guidelines and the inconsistency in evidence level should be also acknowledged. More data are needed to develop more solid recommendations for the ascending aorta and aortic arch diseases.

The impact of pre-existing blood pressure control in patients with acute aortic dissections

OBJECTIVES

Arterial hypertension (HTN) is considered a seminal risk factor for aortic dissection (AD). The purpose of this study is to evaluate whether pre-existing blood pressure (BP) control lessens the extent of dissection and has a favorable impact on outcome of patients with acute AD.

METHODS

Consecutive acute AD patients who had at least two BPs recorded within the 12 months preceding the AD were retrospectively analyzed. The two most recent BPs were averaged and defined per published guidelines as normal (BP≤ 130/80), Stage I HTN (BP >130/80 and <139/89), or Stage 2 or greater HTN (BP > 140/90). The number of hypertensive medications (MEDs) was also used as a surrogate marker of HTN severity. Patients with known genetic causes of AD were excluded.

RESULTS

89 subjects (55% men, 45% women; mean age, 64±14 years) with acute AD (58% Stanford type A and 42% Stanford type B) were included. Two most recent BPs were recorded a mean of 5±3 and 3±2.7 months before the AD, respectively. Twenty-nine (33%) subjects had normal BP, including nine subjects with no history of HTN and on no MEDs. Sixty (67%) subjects had elevated BP, including 21 (35%) with Stage I HTN and 39 (65%) with Stage 2 HTN. Compared to subjects with normal BP, subjects with Stage 1 and Stage 2 HTN were younger (70±13 years vs 62±1 year, p = 0.01), but there were no differences in other demographics, risk factors, comorbidities, or history of drug use. There were no group differences in the distal extent of the dissections, complications requiring thoracic endograft repair, mean length of hospital stay, final discharge status, or 30-day mortality. Compared to the number of MEDs before AD, all three groups had a higher mean number of MEDs to achieve normal BP at discharge that persisted at a mean follow-up of 18±15 months.

CONCLUSIONS

These data show that approximately one-third of patients with acute AD had well controlled or no antecedent history of HTN. The degree of pre-existing HTN control had no bearing on the type or extent of AD, length of stay, or early outcome. Regardless of the state of HTN control before AD, the consistent and sustained increase in the severity of HTN after AD suggests that the dissection process has a profound and lasting effect on BP regulation. Further studies are indicated to elucidate the pathologic mechanisms involved in AD.

Computed Tomography Angiography Assessment of Acute Aortic Syndromes: Classification, Differentiating Imaging Features, and Imaging Interpretation Pitfalls

An acute aortic syndrome (AAS) is an important life-threatening condition that requires early detection and management. Acute intramural hematoma (IMH), aortic dissection (AD) and penetrating atherosclerotic ulcer (PAU) are included in AAS. ADs can be classified using the well-known Stanford or DeBakey classification systems. However, these classification systems omit description of arch dissections, anatomic variants, and morphologic features that impact outcome. The Society for Vascular Surgery and Society of Thoracic Surgeons (SVS-STS) have recently introduced a classification system that classifies ADs according to the location of the entry tear (primary intimomedial tear, PIT) and the proximal and distal extent of involvement, but does not include description of all morphologic features that may have diagnostic and prognostic significance. This review describes these classification systems for ADs and other AAS entities as well as their limitations. Typical computed tomography angiography (CTA) imaging appearance and differentiating features of ADs, limited intimal tears (LITs), IMHs, intramural blood pools (IBPs), ulcer-like projections (ULPs), and PAUs will be discussed. Furthermore, this review highlights common imaging interpretation pitfalls, what should be included in a comprehensive CTA report, and provides a brief overview of current management options.

Aortic Wall Enhancement Detected by Contrast Computed Tomography Scan Predicts Aortic Remodeling after Conservative Therapy for Acute Uncomplicated Type B Dissection

BACKGROUND

The Investigation of Stent Grafts in Aortic Dissection with extended length of follow-up trial showed that pre-emptive thoracic endovascular aneurysm repair (TEVAR) for the uncomplicated type B dissection (TBAD) in the subacute phase promotes aortic remodeling and avoids aortic-related death 5 years after onset. However, there are some patients with complete aortic remodeling (CAR) with optimal medical treatment (OMT) and severe complications after TEVAR such as retrograde type A dissection. Therefore, which patients should undergo pre-emptive TEVAR and optimal surgical timing are still under debate. We reported that aortic wall enhancement (AWE) after endovascular aneurysm repair for abdominal aortic aneurysm was associated with sac shrinkage. However, there is no report about the relationship between AWE and aortic dissection. Herein, we evaluated the relationship between AWE and acute TBAD.

METHODS

From March 2012 to May 2018, consecutive patients with acute TBAD were retrospectively collected. We retrospectively analyzed 35 patients with acute TBAD who were treated with OMT and without pre-emptive TEVAR in the subacute phase. AWE was defined as an increase of more than 20 Hounsfield units in mean computed tomography (CT) values, comparing images in delayed contrast-enhanced scans with those in plain scans evaluated within 3 months from onset. The measurement points were all slices including the wall of the false lumen. The patients with traumatic dissection, type A dissection, acute complicated type B dissection, chronic (>12 weeks) dissection, and those lost to follow-up within 3 months from onset were excluded. The primary end point was spontaneous CAR under OMT, as determined by the latest contrast-enhanced CT scan.

RESULTS

The median follow-up period from onset was 86 weeks and there were 25 cases (71.4%) with AWE. Under OMT, CAR was observed in 20 patients (57.1%); this was significantly associated with abdominal branch dissection (6/15 [40%] vs. 2/20 [10%], P = 0.050), number of tears more than 2 at onset (11/15 [73%] vs. 4/20 [20%], P = 0.003), multiple tears at 1 month after onset (9/15 [60%] vs. 4/20 [20%], P = 0.020), maximal false lumen diameter at 1 month after onset (14 vs. 8 mm, P = 0.025), and AWE within 3 months of onset (7/15 [47%] vs. 18/20 [90%], P = 0.010). Multivariate analysis demonstrated a significant difference with multiple tears at onset (P = 0.014) and AWE within 3 months of onset (P = 0.047).

CONCLUSIONS

AWE was associated with CAR under OMT for acute TBAD which is out of indication of pre-emptive TEVAR. Presence of AWE may be useful in predicting prognosis of TBAD.

Closing the gap between type A and type B aortic dissections

PURPOSE OF REVIEW

Given its rarity little is known about natural history, surgical indications, and results of acute non-A non-B dissections. With this review, we aim to review the current knowledge of this subject.

RECENT FINDINGS

non-A non-B aortic dissections should be differentiated from type B aortic dissections. A strikingly high proportion of these patients have a complicate course requiring treatment and the mortality of patients treated with medical therapy is substantially higher compared to type B dissections. Surgical and endovascular treatment can be accomplished safety, with very good results in terms of mortality and morbidity also in the acute setting. Several treatments options are available including endovascular repair with thoracic endovascular aortic repair (TEVAR) associated with Chimney grafts or carotid to subclavian by pass, open arch replacement mainly by means of the frozen elephant trunk technique and hybrid arch repair with debranching of the supra-aortic vessel and zone 0 TEVAR.

SUMMARY

considering the high rate of complication, the high mortality of patients managed medically and the safety of surgical and endovascular repair, early invasive treatment of non-A non-B dissections may be further considered. The treatment should be tailored to the morphology of the dissected aorta with TEVAR reserved to more distal lesions and open arch replacement with the FET technique for more proximal lesions.

Initial results of thoracic endovascular repair for uncomplicated type B aortic dissection involving the arch vessels using a semicustom-made thoracic fenestrated stent graft

OBJECTIVE

Thoracic endovascular aortic repair (TEVAR) for selected type B aortic dissection (TBAD) is a standard treatment; however, TBAD involving the aortic arch is difficult to treat because of the need for arch vessel reconstruction. We report our initial results of TEVAR for uncomplicated TBAD involving the arch vessels using a semicustom-made fenestrated stent graft.

METHODS

This is a retrospective study of 24 patients treated by fenestrated (F group) or debranching (D group) TEVAR from August 2011 to July 2017. The patients in the F group received the Najuta semicustom-made fenestrated stent graft (Kawasumi Laboratories, Tokyo, Japan). The fenestrated graft ensures sufficient sealing at the proximal healthy aorta without the need for arch vessel reconstruction. The primary end point was aorta-related mortality; the secondary end points were technical success and major adverse events (stroke, type IA endoleak, retrograde type A aortic dissection, and secondary intervention).

RESULTS

During the study period, we treated 65 TBAD cases by TEVAR, including 17 complicated cases. Of the 48 uncomplicated cases, 24 underwent TEVAR with arch vessel involvement (13 in the F group and 11 in the D group). The technical success rates in the F and D groups were 92.3% and 100.0%, respectively (P > .99, NS). The mean operation time was significantly shorter in the F group (158 minutes) than in the D group (202 minutes; P = .0426), and the mean postoperative hospital stay was also significantly shorter in the F group (7 days) than in the D group (22 days; P = .0168). The primary patency rate of the reconstructed branch vessel was 100%, and there were no aorta-related deaths or retrograde type A aortic dissection in either group. One patient had a type IA endoleak in the F group. In the D group, one patient had a postoperative stroke and two patients required secondary interventions for stent graft-induced new entry at the descending aorta. The median follow-up period was 14.1 months (range, 1-37 months). The rate of freedom from aorta-related death was 100% in both groups (P > .99, NS); the rate of freedom from major adverse events at 24 months was 92.3% in the F group and 72.7% in the D group (P = .749, NS).

CONCLUSIONS

The initial results of TEVAR with aortic arch vessel reconstruction for uncomplicated TBAD were acceptable. The fenestrated graft may be a less invasive option for the treatment of TBAD involving the aortic arch.

Current evidence in predictors of aortic growth and events in acute type B aortic dissection

OBJECTIVES

Acute type B aortic dissection can have a stable course or evolve into aneurysm and subsequent adverse events. The aim of this systematic review was to analyze the morphologic predictors of an adverse course to establish their validity based on consistency of results.

METHODS

Fifty-one studies were included in this review, reporting on aortic size, false lumen (FL) size, primary entry tear (ET) size and location, status of FL thrombosis, number of ETs, branch vessels involvement, and FL longitudinal extent.

RESULTS

Some predictors showed good consistency, whereas others did not. Aortic size was the most investigated predictor. A larger diameter at presentation predicted worse outcomes, with few exceptions. Both FL size and size relative to true lumen size also predicted an adverse course, although a standardized measurement method was not used. Regarding primary ET size and location, evidence was sparse and somewhat conflicting. Although FL complete thrombosis was consistently associated with a more benign course, the role of partial thrombosis remained unclear and the concept of FL saccular formation might account for the inconsistency, but further evidence is needed. A higher number of re-entry tears was considered to be protective against false channel expansion, but results need to be confirmed. The predictive role of branch vessels involvement and FL longitudinal extent remain controversial.

CONCLUSIONS

Among several predictors of aortic growth and events in acute type B aortic dissection, controversial and even conflicting results have been described. Consistent evidence has been demonstrated only for two predictors: aortic size at presentation is associated with adverse events and total FL thrombosis has a protective role.

Left subclavian artery dissection associated with connective tissue abnormalities resembling Marfan-like syndrome in an English bulldog

The unexpected demise of a 12-year-old male neutered English bulldog solicited a gross examination, which revealed a blood-filled space occurring in the proximal left subclavian artery (LSA). It originated about 1 cm from the branching point of the vessel and progressively dilated for 3 cm distal to this origin. Histopathological investigation showed that the tunica media of the LSA was more than 50% split, with the blood-filled space dissecting through the arterial wall. In the tunica media of the LSA, severe multifocal fragmentation and/or loss of the elastic fibers was observed. The retained disorganized elastic fibers were separated and disoriented due to accumulations of acid mucopolysaccharide. Marked, diffuse medial, and adventitial fibrous tissue deposition was also identified. The cause of death was attributed to acute hemorrhagic and necrotizing pancreatitis with pulmonary edema, suggesting that LSA dissection was an incidental finding. Subclavian artery dissection is extremely rare in humans, where the involvement of the LSA in cases of aortic dissection both with or without Marfan syndrome has been reported. Aortic and pulmonary artery dissection in bovines and aortic aneurysm and dissection in dogs have been reported to be associated with Marfan and Marfan-like syndromes, respectively. Histopathological findings suggestive of underlying connective tissue abnormalities resembling Marfan-like syndrome (i.e., the appearance of the elastic tissue and the degenerative changes of the tunica media) were detected in the first case of LSA dissection in dogs and veterinary medicine, herein described.