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Ann Thorac Surg 2007;83:S842-S845
© 2007 The Society of Thoracic Surgeons

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Supplement

Update on Outcomes of Acute Type B Aortic Dissection

^a Department of Cardiothoracic and Vascular Surgery, The University of Texas-Houston Medical School, Houston, Texas
^b Memorial Hermann Heart and Vascular Institute, Houston, Texas

Accepted for publication October 17, 2006.

^_* Address correspondence to Dr Estrera, Department of Cardiothoracic and Vascular Surgery, The University of Texas-Houston Medical School, 6410 Fannin St, Suite 450, Houston, TX 77030 (Email: anthony.l.estrera{at}uth.tmc.edu).

Presented at Aortic Surgery Symposium X, New York, NY, April 27–28, 2006.

	Abstract

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BACKGROUND: The optimal treatment of acute type B aortic dissection remains controversial. This study reports early clinical outcomes of medical management for acute type B aortic dissection.

METHODS: Between January 2001 and April 2006, data on 159 consecutive patients (55 women [35%]) with the confirmed diagnosis of acute type B aortic dissection were prospectively collected and analyzed. Mean age was 62 years (range, 29 to 94). On admission, all patients were initiated on an acute type B aortic dissection protocol with the intent to manage all patients medically. Indications for surgical intervention included rupture, aortic expansion, retrograde dissection, malperfusion (visceral, peripheral), and intractable pain. All patients were followed up after discharge with serial clinical and radiographic examinations.

RESULTS: Overall hospital mortality was 8.8% (14/159): 17% (4/23) with procedural intervention, and 7.4% (10/136) when medical management was maintained. Early intervention was required in 23 patients (14.5%), of which 21 (13.2%) were open vascular/aortic procedures, and two (1.3%) were percutaneous aortic interventions. Morbidity included rupture (5.0%), stroke (5.0%), paraplegia (8.2%), bowel ischemia (5.7%), acute renal failure (20.1%), dialysis requirement (13.8%), and peripheral ischemia (3.8%). Mortality associated with complicated dissection (74/159) was 17%, and mortality associated with uncomplicated dissection (85/159) was 1.2% (p < 0.0003). Late vascular related procedures were performed in 11 (7.6%) of 144 cases (9 aortic, 2 peripheral vascular). The only independent risk factors for hospital mortality by multiple logistic regression analysis was rupture (p < 0.0009). Independent risk factors for mid-term death were history of chronic obstructive pulmonary disease (p < 0.002) and glomerular filtration rate at admission (p < 0.0001).

CONCLUSIONS: Medical management, especially for uncomplicated acute type B aortic dissection, is associated acceptable outcomes. This study provides current data for initial medical management of acute type B aortic dissection. Alternative strategies for the treatment of acute Type B aortic dissection should be compared with these results.

	Introduction

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The current treatment of uncomplicated acute descending thoracic aortic dissection (Stanford type B) remains medical. Morbidity and mortality rates associated with the medical management of acute type B aortic dissection still remain significant, with an early mortality of 10% to 12% [1–3]. For this reason, the optimal initial management, especially in complicated cases of acute type B aortic dissection, has become debatable. Thus, the purpose of this study was to report early and intermediate clinical outcomes for acute type B aortic dissection. This report is an update of our registry of patients who presented with acute type B aortic dissection [4].

	Material and Methods

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Data collection and analysis was approved by the Memorial Hermann Hospital and the University of Texas Houston Medical School Committee for the Protection of Human Subjects. Between January 2001 and April 2006, information was prospectively collected and analyzed on 159 consecutive patients wiith the confirmed diagnosis of acute type B aortic dissection. Mean patient age was 62 years (range, 29 to 94), and 55 (35%) were women.

Aortic dissection was classified as type B according to the Stanford classification if the dissection did not involve the ascending aorta [5]. The dissection was considered acute if the dissection presented within 2 weeks of the initial onset of symptoms (eg, pain). Included were cases of classic dissection; that is, dissecting membrane with some degree of patency of both the true and false lumens, and intramural hematoma (IMH). Classic dissection was noted in 146 (92%) of 159 patients, with isolated IMH in 16 (8%).

On admission, all confirmed patients were treated with an acute aortic dissection protocol. Details have been previously reported [4]. Initial intent was to manage these patients medically. The initial goals were to halt the progression of dissection by decreasing the P/T or "impulse force" and to control the pain. Indications for vascular surgical intervention included rupture, aortic expansion (aortic diameter >5 cm), retrograde dissection into the ascending aorta, visceral and peripheral malperfusion, and intractable pain despite optimal medical management.

Patients who did not require surgical intervention were discharged when blood pressure and pain were controlled on an oral regimen. All patients were followed up after discharge with serial clinical and radiographic examinations at 6 weeks, 3 and 6 months, and yearly thereafter. Continued surveillance was maintained through direct patient or referring physician contact.

Hospital mortality was defined as death during hospitalization. Complicated dissection was defined as any occurrence of rupture or cerebral, spinal, visceral, renal, or peripheral malperfusion. The glomerular filtration rate was derived from the Cockcroft-Gault equation on admission. Chronic obstructive pulmonary disease was defined as a history of bronchitis or emphysema.

Data Analysis
Analysis was retrospective. Survival was ascertained by direct patient contact (telephone or letter) and by searching the Social Security death index. Data were collected from chart reviews done by a trained nurse abstractor and were entered into a dedicated Access database (Microsoft, Redmond, WA). For analysis, data were exported to SAS 6.12 (SAS Institute, Cary, NC) running under Windows 2000 (Microsoft).

Patients were followed up until death or until follow-up reached the study end date (April 10, 2006). Univariate risk factor effects on survival were evaluated using the Kaplan-Meier product-limit method. Continuous variables were stratified by quartile. Hypothesis tests of homogeneity over strata were computed using the log-rank test. Adjusted effects of risk factors on survival were evaluated using Cox proportional-hazards regression analysis, using stepwise and best-subsets model selection techniques. Continuous variables were left continuous for the Cox analyses.

	Results

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Overall hospital mortality was 8.8% (14/159); 17% (4/23) when vascular intervention was required during the initial hospitalization and 7.3% (10/136) if medical management was maintained. Eight patients (5.0%) presented with rupture with an associated mortality of 50% (4/8). The four survivors all underwent surgical repair of the descending thoracic aorta.

Complicated dissection occurred in 47% (74/159) of patients and was associated with a hospital mortality of 18% (13/74); this was compared with an uncomplicated dissection (53%, 85/159) mortality of 1.2% (1/85), p < 0.0003.

Of the patients treated with the medical regimen, 97% (155/159) required at least one intravenous antihypertensive medication during hospitalization, and most required a multidrug regimen. Median time to achieve a blood pressure of less than 140 mm Hg from the time of admission was 48 hours (range, 0 to 720 hours), and median time to control primary pain from time of admission was 48 hours (range, 0 to 264 hours). All patients were discharged on oral antihypertensive medications. Mean hospital length of stay was 15 days (range, 1 to 88 days), and mean intensive care unit stay was 8 days (range, 1 to 58 days).

Patient morbidities are listed in Table 1. Neurologic complications occurred in 24 (15.1%) patients. The 8 patients who sustained a stroke were not among the 3 patients who developed retrograde type A aortic dissection. The cause of cerebral hemorrhage during acute type B aortic dissection was unclear. Two cases were described as intraparenchymal and one as subarachnoid hemorrhage. Paraplegia occurred in 8.2% of patients, with most (11/13) involving bilateral lower extremities. It is of interest that 62% of the cases of paraplegia (8/13) resolved within 24 hours of presentation. Of note, early in our experience, cerebrospinal fluid drainage was inserted in 2 patients who presented with paraplegia, with no improvement in neurologic function.

Early vascular intervention (occurring during primary hospitalization) was required in 23 patients (14.5%): 21 (13.2%) were open vascular interventions and two (1.6%) were percutaneous aortic interventions (Table 2). Three cases (1.9%) of retrograde dissection occurred, with subsequent replacement of the ascending aorta under profound hypothermic circulatory arrest.

View larger version (13K): [in this window] [in a new window]   Fig 1. Actuarial survival of cohort with acute type B aortic dissection. (Solid-line, product-limit estimate curve; dots, censored observations.)

	Comment

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The results of this study underscore the unpredictable nature of acute aortic dissection. Early mortality and morbidity are primarily the result of expansion with rupture or end-organ malperfusion. With an incidence of rupture at presentation of only 4.6%, end-organ malperfusion was the most common cause of significant morbidity during the acute presentation of type B aortic dissection. This is presumably the result malperfusion leading to thrombosis, ischemic–reperfusion injury, or a systemic inflammatory response syndrome. Unpredictable variability in blood flow patterns occurring in the dissected aorta further complicates acute aortic dissection. Of interest is that the changes in aortic blood flow patterns also allow for resolution of malperfusion as depicted in this series, with spontaneous resolution of paraplegia in 62% of patients and peripheral ischemia in 57%.

In general, initial medical management has been the consensus for the treatment of acute type B aortic dissection unless associated with life-threatening complications. Early mortality remains significant despite aggressive medical management, and diminished long-term survival has been reported in these patients [6]. For these reasons, endovascular treatment of acute aortic dissection has gained increased interest as an initial treatment option. The appeal arises from the potential to address malperfusion syndromes as well as to exclude the tear and obliterate the false lumen. In a recent meta-analysis, however, the mortality rate in the subgroup of 248 patients with acute type B aortic dissection treated with endovascular stenting was still significant at 10%, with paraplegia in 2% to 3% [7].

The indications for endovascular therapy during acute type B aortic dissection have yet to be determined. Complicated aortic dissection—patients who present with rupture or malperfusion, which was almost 50% of patients in this series—may become a specific indication, although validation with studies comparing surgical therapy are likely required. Less clear, however, is the use of endovascular therapy in uncomplicated dissection. In the acute setting, it appears that medical management is adequate, associated with only 1.2% mortality, assuming a standardized medical protocol. What remain unclear, however, are the potential benefits of endovascular therapy, such as sealing the tear and the false lumen, in the chronic setting. We await the results of ongoing studies.

In conclusion, although acute aortic dissection remains associated with significant mortality and morbidity, medical management is associated acceptable outcomes, especially in uncomplicated cases. Further studies evaluating other management strategies such as endovascular stenting, for acute type B aortic dissection need to be performed and compared with these results.

	Acknowledgments

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We thank Kirk Soodhalter for his editorial assistance and for preparation of this manuscript.

	References

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5. Daily PO, Trueblood HW, Stinson EB, Wuerflein RD, Shumway NE. Management of acute aortic dissections Ann Thorac Surg 1970;10:237-247.[Medline]
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7. Eggebrecht H, Nienaber CA, Neuhauser M, et al. Endovascular stent-graft placement in aortic dissection: a meta-analysis Eur Heart J 2006;27:489-498.[Abstract/Free Full Text]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Anthony L. Estrera Eyal E. Porat Paul E. Achouh Jayesh Dhareshwar Riad Meada Hazim J. Safi Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Estrera, A. L. Articles by Safi, H. J. Search for Related Content PubMed PubMed Citation Articles by Estrera, A. L. Articles by Safi, H. J. Related Collections Great vessels