Introduction
Diabetes mellitus (DM) is associated with dysfunction of the fibrinolytic system and hypercoagulability state resulting in decreased tissue perfusion especially in the peripheral circulation [1,2,3]. This phenomenon is increased in patients with disturbed peripheral tissue perfusion due to arterial obliteration causing chronic ischemic ulcer in the foot, which is a common and severe complication of DM [4,5]. Patients with peripheral artery occlusive disease and DM are vulnerable to decreased blood supply to the skin and the surrounding peripheral tissues causing severe complication on the local tissue perfusion that in turn would decrease the tissue oxygenation and nutrition [6].
There is evidence of an increase in the serum level of fibrinogen in patients with DM that could cause disturbance in the arterial and venous circulation [7]. After activation of thrombin in the coagulation process, the fibrinogen is transformed into fibrin monomers that polymerize to form heterogenous abnormal fibrin network in DM, including thick fibers invaginated by thin fibers with small pores [8]. Fibrin composition and network architecture is one of the factors affecting the rate of fibrinolysis, and any disturbance in it would cause thrombosis in the vessel [9].
A previous randomized clinical trial investigated the efficacy of the low molecular weight heparin (LMWH) on the neuroischemic ulcers in the foot of diabetic patients and revealed that it could improve the outcome of these ulcers [10]. The exact mechanism by which the LMWH could improve the outcome of neuroischemic function is not clear yet; however, it is obvious that its work on the hemostasis could positively affect the microvascular circulation on the skin and peripheral tissues. Furthermore, it was reported that LMWH showed great efficacy in the prevention of coagulation in the coronaries of patients with ischemic heart disease [11]. In the current practice, new oral anticoagulants, such as rivaroxaban, were recommended to be used instead of LMWH in many situations such as acute limb ischemia. In this study, we aimed to investigate the association between rivaroxaban and the hemostasis parameters, coagulation biomarkers, and fibrinolysis in patients with DM, peripheral artery occlusive disease, and chronic foot ulcers. Furthermore, we aimed to investigate the efficacy of rivaroxaban on the microcirculation of the skin and the surrounding peripheral tissues.
Methods
Study design
This study was conducted as an observational retrospective study to illustrate the role of rivaroxaban in patients with DM, lower limb noncritical ischemia, and chronic foot ulcers who presented at the outpatient clinic of the vascular surgery department at Al-Azhar University Hospital, New Damietta, from January 2015 till December 2020.
The study was approved by the institutional review board of the New Damietta Faculty of Medicine, Al-Azhar University, and informed written consent was obtained from all participants. The study is conducted in accordance with Helsinki standards as revised in 2013.
Eligibility criteria
Any patient with blood pressure index in the toe or arm less than 0.6, duration of foot ulcer more than 2 months, foot ulcer of stage I or II by Wagner classification [12], aspirin therapy for at least 1 month before the admission was considered for the inclusion in the study. On the other hand, patients with threatened limb loss, reconstruction surgery or angioplasty of 3 months or less before the admission, chronic renal disease, anticoagulant therapy for any causes at the time of admission, rivaroxaban hypersensitivity, and pregnant or lactating women were excluded from the study.
Study groups
Patients were categorized into two groups: case group that included patients who received rivaroxaban 10 mg daily till the healing of the ulcer or for a duration not more than 6 months, and control group that included patients who did not receive anticoagulant therapy, but instead received other treatment modalities including antiplatelets such as aspirin. The ulcer was considered as healed if the surface area of the ulcer reduced by ≥50% and was considered unchanged if the surface area decreased or increased by less than 50%. Consequently, it was considered worsened if the surface area increased ≥50%.
Data measurement
For all patients, the microcirculation in addition to the macrocirculation was assessed at the admission (baseline) and two other times at 3-month interval using the clinical assessment and pulse oximeter [13,14]. Furthermore, the systolic toe blood pressure was measured and the consequent toe to arm blood pressure index was also calculated [15]. The investigation of peripheral sensation was performed through investigating the pressure sensation and the vibration sensation. The ulcer was dressed in the two groups using normal saline. Using pulse oximetry, transcutaneous oxygenation was measured at the foot dorsum to assess the skin oxygenation.
The serum fibrinogen level was determined using the syneresis method [16], whereas prothrombin fragment 1+2 was assessed to determine the thrombin using ELISA. Furthermore, ELISA was used to detect the tPA antigen (Biopool International, Umea°, Sweden), whereas the bioimmunoassay was used to detect the activity of PAI-1.
Statistical analysis
Statistical analysis was performed on the SPSS software version 23 for Windows (IBM Corporation, New York, USA). The sample size calculation was conducted using MedCalc software for Windows using the level of fibrinogen that was published by Kalani et al. [17] and using 0.05 as alpha value and 0.80 as power. Continuous parametric data were represented using mean and SD, whereas nonparametric data were presented using the median and interquartile range. Furthermore, categorical data were represented using the number and frequency. The comparison between the two groups was analyzed using Student’s t-test for continuous variables, whereas Mann–Whitney and Wilcoxon tests were used in other variables. The correlation coefficient was used to determine the association between two different variables. Statistical significance was determined when the P value <0.05.
Results
Throughout the 5 years of the study, 172 patients were included; the case group included 87 patients and the control group included 85 patients. There was no difference between the case and the control groups regarding the demographic characteristics data (Table 1). There was no difference between demographic characteristics at admission and after 3 months in the case group. However, glucosylated hemoglobin was decreased significantly after 3 months in the control group (P<0.05).
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Table 1: The demographic characteristics of the patients in both case and control groups at the time of hospital admission
The number of patients with healed ulcers in the case group who were treated with rivaroxaban 10 mg daily was significantly higher than the number of patients with healed ulcers in the controlled group. Furthermore, there was no difference between study groups regarding the toe blood pressure and the toe to arm blood pressure index at the time of admission; however, it increased significantly after 6 months of admission in both groups (P<0.05).
Having the oxygenation of the skin, there was no significant difference between the two groups regarding the transcutaneous oxygen tension at the time of hospital admission. However, it increased significantly in the case group after 6 months with a significant difference between the two groups (Table 2). The toe blood pressure in patients with improved ulcers was 58±22 mmHg; whereas the toe-to-arm index was 0.5±0.1 and the transcutaneous oxygen tension was 27±19 mmHg. There was no association between any change in the ulcer and the vascular variables (both macro- and microcirculation).
Table 2: The changes that occurred in coagulation and fibrinolysis variables at the end of the study
Despite there was no difference between the study groups regarding the plasma level of fibrinogen, there was a negative association between the levels of plasma fibrinogen and the transcutaneous oxygenation (Table 2). No association was detected between the plasma concentration of fibrinogen or variables related to fibrinogen gel structure and any change in the site of the ulcer.
Having the plasma levels of prothrombin fragment 1+2 and PAI-1, there was no difference between study groups at the time of admission regarding both of them (Table 2). However, after 6 months, the prothrombin fragment 1+2 was increased significantly in the control group, and PAI-2 was increased significantly in the case group. The subgroup analysis showed that the PAI-1 activity was increased in both subgroups in the control group (the group who improved and another group who deteriorated), whereas it did not increase in all subgroups of the vase group. There was no association between the variables of hemostatic function and the change in the ulcer site. There was a significant difference between the two groups regarding the permeability coefficient, fiber mass/length ratio, and tissue plasminogen activator antigen, and tissue oxygenation (P<0.05).
Discussion
Patients with DM are prone to chronic ulcers in the foot that may be severely complicating, and life threading, especially if these patients have peripheral artery occlusive disease [5]. Treatment with anticoagulants such as Dalteparin has shown favorable effect as an adjunctive treatment of ulcer in such patients [10]. Diabetic angiopathy is one of the causes of ulcer development, and it is characterized by hypercoagulopathy and defects in fibrinolysis [18]. In this study, we investigated the role of anticoagulant (Rivaroxaban) on fibrinolysis and microvascular circulation of the ulcer in addition to the coagulopathy. Diabetic patients with chronic foot ulcer were associated with the elevated plasma level of fibrinogen and dense fibrin network. In such patients, it is expected that anticoagulants such as new oral anticoagulants or Dalteparin would change the fibrin gel network to make it more porous; therefore, it would improve the microcirculation. This indicates the role of anticoagulants in treating diabetic patients with foot ulcers and peripheral occlusive arterial disease as they improve the local tissue oxygenation and the microvascularity.
Peripheral artery occlusive disease is a result and indication of atherosclerosis in the systemic circulation and could be considered as a risk factor for the development of foot ulcers in diabetic patients [19]. All patients included in our study had peripheral arterial occlusive disease, and about a quarter of these patients previously underwent an amputation. Both macro- and microcirculation are important for local tissue oxygenation and conveying nutrients. Consequently, both are important for ulcer healing. The microangiopathy in DM is characterized by shunting of blood through arteriovenous anastomosis that consequently would reduce the blood in the capillary bed causing a decrease in the nutrition and oxygenation and the development of ischemia [20]. Many factors can aggravate this microangiopathy including neuropathy, blood disease, and hyper-viscosity of the blood. Our results revealed that the local tissue oxygenation was improved at the site of ulcer after taking anticoagulant; however, there was no change regarding the skin microcirculation. This could be explained by shifting blood from arteriovenous anastomosis to capillary bed.
Arterial thrombosis could be enhanced by many factors including severe stenosis in the vascular wall, decreased blood flow, increased fibrin and thrombin formation, and decreased fibrinolysis. In our study, the plasma levels of fibrinogen and PAI-1 were elevated in both groups denoting impaired fibrinolysis and hypercoagulability. The acute tissue reactants were elevated in both groups that indicated the presence of similar inflammation in the local area of both groups. Local tissue oxygenation could be a factor that could decide the fate of the ulcer and upon which we could decide the need for amputation [21]. We also revealed a negative association between the plasma fibrinogen level and the microcirculation. This could be explained through the increased plasma viscosity that could decrease the tissue perfusion, and the low level of plasma fibrinogen could be a result of severe vasculopathy causing vicious circle [22,23].
The porosity of fibrin gel was increased after taking the anticoagulants. Furthermore, our results revealed a positive association between the fibrin gel porosity and local skin oxygenation. This could also increase the microcirculation in the skin area of the ulcer and therefore enhance the healing. Fibrin fiber density could also be affected by various metabolic factors, including glycated hemoglobin and treatment with antiplatelets [24,25,26]. All patients showed accepted levels of glycated hemoglobin and all patients in the two groups received antiplatelet. This indicated that the change in the fibrin gel was due to the received anticoagulant.
The increased levels of plasma fibrinogen and PAI-1 in the control group could be explained by the fact that the anticoagulant could decrease their plasma concentration and the enhancing effect on fibrinolysis. The positive outcomes regarding the ulcer were seen in the group of patients who received anticoagulation. This could be explained by the presence of a positive correlation between ulcer outcomes and local tissue oxygenation and microcirculation. Disturbed healing of the ulcer in patients with DM and peripheral arterial occlusive disease could be attributed to many factors including presence of neuropathy, metabolic factors, presence of inflammation tissue oxygenation, and microcirculation. These factors could work together to either participate in ulcer healing or ulcer deterioration. Therefore, administration of anticoagulants such as new oral anticoagulants could affect all of these factors and therefore enhance the healing of the ulcer.
Despite these beneficiary results, this study showed some limitations. One of them is the study design; being retrospective observational study is not the better design for the study. Therefore, a prospective randomized controlled trial would be better and would result in a robust result. Another limitation is the small sample size that needs to be increased. Moreover, new oral anticoagulants are not routinely used in diabetic foot ulcers such as subcutaneous or intravenous anticoagulants.
In conclusion, there was a positive association between administration of anticoagulants and the local tissue oxygenation, microcirculation, fibrinolysis, and fibrin gel porosity in diabetic patients with peripheral arterial occlusive disease and having chronic foot ulcers. Furthermore, there was an inhibitory effect of anticoagulant and thrombin formation and blood flow in the arteriovenous anastomosis. Therefore, new oral anticoagulants would benefit diabetic patients with the peripheral arterial occlusive disease and chronic foot ulcers.
Recommendations
- New oral anticoagulant is helpful in patients with diabetic foot ulcers as it improves local tissue oxygenation, microcirculation, fibrinolysis, and fibrin gel porosity.
- Patients with peripheral arterial occlusive disease due to diabetes would benefit from new oral anticoagulants.
- New oral anticoagulants are similar to conventional anticoagulants regarding the effectiveness but better in compliance.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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