Methods
Definitions
Acute type B Aortic Dissection. Aortic dissection involving the descending thoracic aorta and distal sites only and the diagnosis has to be within 14 days of onset of symptoms.
Complicated Type B Aortic Dissection. Complicated dissections refer to aortic rupture, visceral and renal ischemia, lower extremities ischemia, or spinal cord ischemia (SCI). Expansion to the aortic arch or proximal descending aorta with a total diameter of 4.5 cm or greater is also considered a complicated dissection. However, refractory hypertension, hypertension persisting despite three different classes of antihypertensive therapy at maximal recommended or maximal tolerated doses, if not present in the clinical history before the onset of dissection, is considered a sign of instability or of renal malperfusion.
Malperfusion syndrome is the most frequent complication of type B dissection. The clinical presentation includes paraparesis or paraplegia, lower limb ischemia, abdominal pain, nausea, or diarrhea. Visceral artery malperfusion may be associated with an increase in laboratory markers (bilirubin, amylases, hepatic and intestinal enzymes). The CT angiography or magnetic resonance angiography findings such as true lumen compression, or an intimal flap inside the renal, celiac, or mesenteric arteries, carry a high suspicion of visceral malperfusion. Delay or absence of nephrographic effect during the late phase of contrast-enhanced CT scan, often accompanied by an increase in serum creatinine and/or refractory hypertension, indicates renal malperfusion.
Search Strategy
The present meta-analysis was conducted in accordance with the recommendations of the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) group. An extensive electronic health database search was performed on all articles published from January 2006 up to November 2013 describing the management of acute type B aortic dissection. The search was performed using exploded medical subject heading (MeSH) terms: "acute type B aortic dissection", "complicated", "uncomplicated", "medical treatment", "surgical treatment", "open repair" and "endovascular treatment". Publications were retrieved through electronic search engines (Medline, Embase, Scopus, Google Scholar, Ovid, and the Cochrane Library). All studies were independently assessed, and full texts of potentially eligible studies were retrieved. In addition, the reference lists of all retrieved articles were examined for further relevant series.
Study Eligibility, and Exclusion Criteria
Studies were included in the present review if (I) the index aortic pathology was acute type B aortic dissection; (II) BMT, open surgical repair or TEVAR were the applied treatment options; (III) stated the incidence of at least one of the basic outcome criteria; (IV) included ≥15 patients. Articles in languages other than English were eliminated from further analysis. Case reports and case series with less than 15 patients were excluded. Studies referring to chronic aortic dissection were excluded. Studies referring to type A aortic dissection or to combined hybrid endovascular and open thoracic aorta repairs were excluded as well. When multiple publications on the same patient population were identified or study populations overlapped, only the latest report was included, unless the reported outcomes were mutually exclusive. Furthermore, several studies included patients with acute type B dissection as a subset of the entire study cohort. These were included in the present review if separate data for this patient subgroup was provided.
The available data were independently extracted and analyzed by two reviewers (S.M. and K.M.), and a consensus was reached if discrepancies were observed. Primary endpoints included peri-procedural (30-day/in-hospital) mortality, stroke, SCI and total neurologic complications rates. Data regarding long-term survival and aortic event freedom were also analyzed.
Statistical Analysis
Separate meta-analyses was carried out on all eligible studies for peri-procedural (30-day/in-hospital) mortality, stroke, SCI and total neurologic complications. The pooled proportion was calculated as the back-transformation of the weighted mean of the transformed proportions. Statistical heterogeneity was measured using the Cochran Q statistic score (P<0.10 was considered indicative of statistically significant heterogeneity) and the I test. A fixed-effects model was used when no heterogeneity existed among studies. Otherwise, the random effects model was used. The meta-analyses were conducted using StatsDirect statistical software (StatsDirect Ltd, UK). Frequency study-specific estimates were pooled and are reported as event rates with corresponding 95% confidence intervals (95% CI). Long-term data were reported with Kaplan-Meier rates by the study investigators. No pooled analyses of long-term results were performed as there were variable event definitions among studies.