In the present study, higher D-dimer level on admission was a significant independent determinant of short-term neurological dysfunction in patients with AIS within 90 days in the Chinese population. After adjusting for various confounders, the association remained significant.
Previous prospective epidemiological investigations have concluded that there is a positive association between D-dimer levels and stroke [26-28]. In some studies, the results showing that D-dimer was associated with stroke severity [29, 30], infarct volume [15, 31, 32] and progression of stroke status [14, 33, 34]. While in the patient with AIS, there are not many studies about the association between D-dimer levels and poor outcomes.
The available investigations of stroke have shown a correlation between D-dimer levels and functional outcomes and the prognostic value of D-Dimer in several different types of population with AIS [35-39]. Nam et al. [35] and Nezu et al. [36] found a predictive role of D-dimer only in patients with cryptogenic stroke. A Canadian study by Kim et al. [37] reported prognostic Value of plasm D-Dimer in patients with noncardioembolic stroke. In the study of the Chinese population complicating coronary heart disease, the result indicated that higher D-dimer levels had worst outcomes within 90 days after initial onset of AIS[38]. A Swiss study by Hsu et al. reported high plasma D-dimer indicates unfavorable outcome of in patients with AIS receiving intravenous thrombolysis[39]. But review previous literature, we also found that some other studies have reported conflicting results in comparison. A report by Squizzato et al. [19] revealed that D-dimer levels with AIS probably do not predict the functional outcome after adjustment for age and stroke subtype. Furthermore, two other studies even did not find a meaningful association between D-dimer and the prognosis of patients with AIS[40, 41].
In this study, because the prognostic did not alter even if adjusted various confounders such as age, sex, BMI, vascular risk factors, baseline NIHSS scores, and stroke etiology, our results revealed D-dimer is an independent biological prognostic marker of AIS. Actually, the positive value of plasm D-Dimer in patients with all subtypes of AIS was indicated in the previous several studies [33, 41, 42], which is consistent with our findings.
D-dimer derived from the cross-linked fibrin network is a final soluble fibrin degradation product undergoes plasmin-mediated degradation [13]. D-dimer could be elevated in population with thrombotic diseases such as pulmonary embolism and venous thromboembolism [42, 43], however, the mechanism remains unclear. There are several possible explanations for why D-dimer levels might be relevant to poor functional outcomes in patient with AIS. First of all, D-dimer level increases in blood coagulation and degradation of fibrin and could be a marker of thrombosis based on the underlying mechanisms [44, 45]. Moreover, high D-dimer levels may result in resistant to the endogenous fibrinolytic system and influence thromboembolism formation [40, 46]. Furthermore, D-dimer also stimulates the immune system and lead to changes in inflammatory mediators levels such as IL-1, TNF-alpha, IL-6, and IL-8 [47, 48]. Activated inflammation may contribute to the pathological alteration in patients with AIS [49]. In addition, infarct volume, initial stroke severity, and progression of stroke status were correlated with high D-dimer levels [14, 29-34], therefore elevated D-dimer levels may predict poor outcomes through the aggravation of cerebral tissue damage by disturbing recanalization and increasing reperfusion injury. Additionally, D-dimer level in patients with AIS may identify patients who may benefit from additional interventions, targeting some of the mechanisms mentioned above. This need be explored in further studies.
This current study has several limitations. First, this is a single-center, observational study. The sample sizes of patients are small, and selection bias was a major concern, therefore limiting the power to generalize our results. Second, the D-dimer levels were recorded only at admission, recording the serial change of D-dimer levels might be better explored the correlation between D-dimer and outcomes after AIS. Finally, our study did explore short-term outcomes whose end-point was defined at 90 days. The relationship between D-dimer levels and long-term prognosis require further confirmation in our study population. Therefore, further larger sample size, multicenter studies are needed to carry out.
Conclusions
Elevated plasma D-dimer level on admission was significantly associated with increased poor outcome after admission for AIS, suggesting the positive role of D-dimer as a predictive marker for short-term poor outcomes in patients with AIS. Plasma D-dimer level as a convenient and economical biological indicator could be used for better specific management of stroke rehabilitation regarding functional outcomes.