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Acute type A aortic dissection is a relatively uncommon, although potentially life threatening, disease. Given the high mortality, predictive tools to identify patients at increased risk of death are needed to assist clinicians in optimal treatment. Known prognostic parameters are: age > 70 years; abrupt onset of chest pain; hypotension, shock, or tamponade; renal failure at presentation; pulse deficit; and abnormal ECG, particularly ST segment elevation.1
Recently we found that concentrations of D-dimer, a degradation product of cross linked fibrin, were raised in all cases of acute aortic dissection and, therefore, normal D-dimer concentrations can be used to rule out the disease.2 Our results were subsequently confirmed by others.3 However, owing to small patient numbers in both studies, no firm conclusions about the prognostic significance of absolute D-dimer concentrations can be drawn.
We measured plasma concentrations of D-dimer in 27 patients with acute type A dissection of the aorta by using the Tina-quant assay (Roche Diagnostics, Mannheim, Germany) on an automated chemical analysis system (model 704; Hitachi, Tokyo, Japan) as previously described.2 Twelve of these patients have been reported on previously (submitted in 2002); the others have been investigated prospectively and consecutively since then to clarify whether higher D-dimer concentrations confer a worse prognosis. The diagnosis was confirmed for all patients with computed tomography, echocardiography, or necropsy. Prognosis was assessed as in-hospital mortality. Values are absolute numbers (percentage) or median (25–75% interquartile range), unless otherwise stated. Statistical analyses were Mann-Whitney U test for univariate comparisons between the outcome groups and a logistic regression model (including variables associated significantly or marginally with outcome or D-dimer concentrations in univariate analysis) for the prediction of in-hospital mortality.
Mean (SD) age of our patients was 62 (16) years and 15 (55.6%) were men. Seventeen patients (63%) were operated on and the others were treated conservatively due to severe co-morbidities, advanced age, or refusal of the patient or the surgeon. Thirteen patients died (48.1%) during their hospital stay and 14 survived (51.9%).
In agreement with our previous study, D-dimer concentrations were increased (> 0.5 µg/ml) in all patients. D-dimer concentrations were higher in patients who died than in survivors (fig 1, table 1). Other significant predictors of mortality in univariate analysis were a lower diastolic blood pressure on admission and a conservative treatment strategy. Stratified analysis for each treatment strategy showed that D-dimer concentrations were significantly higher in patients who died than in survivors in surgically as well as in medically treated patients (table 1). In the logistic regression model (p = 0.002; the model predicted survival status correctly for 89% of patients), D-dimer was the only independent predictor of mortality (odds ratio 1.32 per unit, 95% confidence interval 1.01 to 1.75, p = 0.046). Other variables included in the model, but not reaching significance, were age, diastolic blood pressure, treatment strategy, ECG evidence of left ventricular hypertrophy (Sokolow or Cornell index), and anatomical extent of disease.
In addition to corroborating our previous results of a 100% sensitivity of a D-dimer cut off concentration of 0.5 µg/ml for acute type A aortic dissection, we found that absolute D-dimer concentrations provide prognostic information about these patients. Increased plasma D-dimer concentrations found in acute aortic dissection reflect endogenous fibrinolytic activity counteracting the activation of the extrinsic pathway of the coagulation cascade; this cascade is triggered by exposure to tissue factor from the dissected aorta. The anatomical extent of the dissection may be hypothesised to be related to the amount of coagulation and fibrinolytic activation. Therefore, absolute D-dimer concentrations may reflect the anatomical extent of the disease.2 On the other hand, increased D-dimer concentrations may originate from systemic inflammatory reactions, which have been previously described in patients with acute aortic dissection and which have been shown to be independent predictors of mortality in acute aortic syndromes.4,5
Of note, the information provided by D-dimer concentrations is independent of and may be additive to clinical parameters of outcome.
As in most single centre studies on aortic dissection, the main limitation of our study is the small sample size, which can be overcome only by a multicentre approach.
In summary, D-dimer concentrations on admission may provide independent prognostic information about patients with acute aortic type A dissection.
We are indebted to Drs Josef Seier and Erich Wimmer for measuring D-dimer. We are indebted to Erich Kvas MSc for statistical evaluation.