Study Design
A retrospective study was performed to explore the efficacy and safety of sequential therapy regimens of subcutaneous LMWH followed by oral rivaroxaban at a dose of 20mg once daily in the management of patients with established acute PE which included symptomatic or incidental PE without hemodynamic instability. The efficacy and safety were compared among LMWH + rivaroxaban group in which patients received sequential LMWH plus rivaroxaban, LMWH + dabigatran group in which patients received sequential LMWH plus dabigatran, and LMWH + warfarin group in which patients received sequential LMWH plus warfarin, from the baseline which was defined as the diagnoses of acute PE through the 3-month follow-up. Based on the matching of body weight, anatomical extent of PE7, and DVT prevalence, the proportion of number of patients in the aforementioned three groups were determined to be approximately 1:1:1.
LMWH were subcutaneous nadroparin at a dose of 4100 IU every 12 hours for a week. Rivaroxaban was at a dose of 20mg once daily for three months following LMWH. Dabigatran was at a dose of 150mg twice daily for three months following LMWH. Warfarin was at a dose of 2.5-5 mg once daily concurrently with LMWH for at least 5 days until an international normalized ratio (INR) ≥ 2.0 for 24 hours. Then the dose of warfarin was adjusted to maintain an INR of 2.0–3.0 for three months.
The primary outcomes were the results of reexamination of PE at the follow-up visit after 3 months of aforementioned anticoagulant treatment. Reexamination of PE was performed by using computed tomography pulmonary angiography (CTPA) and/or planar ventilation/perfusion (V/Q) scan. Based on the results of reexamination of PE, patients were dichotomized into the resolution group that was defined as the absence of PE on CTPA and V/Q scan, and the non-resolution group that was defined as the remnant presence of PE on CTPA and/or V/Q scan. The resolution rate of PE in each group was compared among the LMWH + rivaroxaban, LMWH + dabigatran, and LMWH + warfarin groups. The resolution rate of PE in each group was defined as the proportion of number of patients whose PE were resolved in the total number of patients of each group at the 3-month follow-up visit. Another primary outcome was the prevalence of DVT on compression ultrasonography(CUS) in each group at the 3-month follow-up visit. The prevalence of DVT were compared among the aforementioned three groups.
The secondary outcomes were the cardiac troponin I level, NT-proBNP level, D-dimer, and probability of pulmonary hypertension (PH) on transthoracic echocardiogram at the 3-month follow-up visit. Probability of PH was dichotomized into PH-likely and PH-unlikely based on the criteria in guidelines.2,3 The cardiac troponin I level, NT-proBNP level, D-dimer and the prevalence of PH-likely patients at the 3-month follow-up visit were compared among the LMWH + rivaroxaban, LMWH + dabigatran, and LMWH + warfarin groups. The level change of troponin I, NT-proBNP, and D-dimer from the baseline through the 3-month follow-up visit were also compared among the aforementioned three groups.
The third outcomes were the events of progressed fatal PE for which thrombectomy, vena cava filter insertion, or thrombolysis were performed or indicated, the death from fatal PE, and the compelled discontinuation of anticoagulation including reduction or cessation due to adverse events, during the 3-month treatment of acute PE. Fatal PE was defined as PE with hemodynamic instability due to PE. Adverse events were defined as bleeding including major bleeding and minor one. Major bleeding was defined as fatal bleeding, and/or symptomatic bleeding in a critical area or organ, and/or a fall in hemoglobin level of 20 g/L or more, or a transfusion of two or more units of whole blood or red cells due to bleeding.8 Bleeding that did not conform to major bleeding was defined as minor bleeding. The third outcome were compared among the LMWH + rivaroxaban, LMWH + dabigatran, and LMWH + warfarin groups.
The principal safety outcomes were major bleeding from the initiation of anticoagulation through the 3-month follow-up visit. Major bleeding rates were compared among the LMWH + rivaroxaban, LMWH + dabigatran, and LMWH + warfarin groups. Major bleeding rate was defined as the percentage of patients with at least one episode of major bleeding in each group. For patients with major bleeding, anticoagulation was ceased and not recovered until the bleeding stopped. A vena cava filter insertion or thrombectomy was performed in case of persistent bleeding.
The primary and secondary outcomes were not compared among the aforementioned three groups for patients with progressed fatal PE for which thrombectomy, vena cava filter insertion, or thrombolysis were performed, those who died of fatal PE resulted from the progression of PE, and those whose anticoagulant was reduced or ceased due to adverse events, during the 3-month treatment of acute PE.
The current study was performed by the investigators of Shanghai Xinhua Hospital, Shanghai Pulmonary Hospital, and Shanghai Punan Hospital. All data needed for the study were retrieved from the electronic medical records system(EMRS) of each participating hospital. All authors vouch for the completeness and accuracy of the data. No one who is not an author contributed to the writing of the manuscript. The study protocol was approved by the institutional review board of each participating hospital.