CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 3, July/August 2023 AFRICA 183 of more than 48 hours and less than one year9 (Table 1). The third study was the apixaban study, EMANATE, which enrolled 1 500 patients.10 Apixaban was randomly administered to 753, while 747 patients received warfarin with heparin bridging therapy. In the apixaban group, no patients developed stroke at 30 days, compared to six in the heparin/VKA group. Systolic embolism events were not observed in either group. There were two deaths in the apixaban group (0.27%, 95% CI: 0.03–0.96%) and one in the heparin/VKA group. Finally, there were fewer major bleeding events in the apixaban group than in the heparin/ VKA group (3/735 and 6/721 patients, respectively) (Table 1) A meta-analysis of the above trials (n = 5 203 patients) revealed that the composite primary outcome (stroke/systemic embolism, myocardial infarction or cardiovascular death) was significantly reduced with NOAC treatment compared with VKA.11 This outcome occurred in 12 (0.42%) of 2 850 patients randomised to receive a NOAC versus 23 (0.98%) of 2 353 patients randomised to receive a VKA, with a pooled risk ratio of 0.42 (95% CI: 0.21–0.86; p = 0.017). Differences between NOAC and VKA in all-cause mortality and major bleeding were not observed. Additional information confirming the above conclusions was provided by sub-analyses of the main registry studies concerning dabigatran (RELY study), rivaroxaban (ROCKET AF study), apixaban (ARISTOTLE study) and edoxaban (ENGAGE AF-TIMI 48 study). Sub-analyses included patients who underwent electrical cardioversion during the course of the study12-15 (Table 1). The results of the above randomised trials have been confirmed by retrospective observational studies. Geurink et al. showed no differences in the incidence of stroke or TIA within the first year after ECV among 1 613 AF patients treated with NOAC or VKA.16 These results are comparable to results of another study based on a group of 2 150 patients undergoing ECV.17 Moreover, the use of NOAC has been shown to significantly reduce the time to ECV, eliminating the risk of unplanned postponement of the procedure due to non-therapeutic INR results. In the Kalejs et al. study involving 525 patients, the average time for treatment before cardioversion was significantly lower for dabigatran (25 days) versus warfarin (35 days; p < 0.01).18 These results are in accordance with results from another study including 570 patients.19 The median time from the initiation of dabigatran to the first cardioversion was 32 versus 74 days with warfarin. Thrombi in the left atrial appendage in patients treated with oral anticoagulants The main source of embolic material (approximately 90%) in non-valvular AF is the left atrial appendage (LAA).20 Thrombi in the LAA occur in 5–27% of patients with AF naïve to oral anticoagulation. This rate is comparable in patients treated with subtherapeutic doses of VKA.21-24 More intensive treatment with vitamin K derivatives while maintaining the INR within the therapeutic range between 2 and 3 led to a lower incidence of embolic material, with a frequency of LAA occurring in approximately 0.6–8.3% of cases.25-28 Based on the current knowledge, it seems that the incidence of embolic material in the LAA is similar among patients treated with VKA and NOACs. In the ARISTOTLE study, 743 cardioversions were performed in 540 patients. The procedure was preceded by TEE in 171 patients, 86 of whom were treated with apixaban and 85 who were treated with warfarin; no LAA thrombus was detected in any of the groups.14 In the RELY study, 1 983 cardioversions were performed in 1 270 patients; TEE was performed more often before the procedure in patients treated with dabigatran than those treated with warfarin (25.5 vs 24.1 vs 13.3% of cases for dabigatran 2 × 110 mg, dabigatran 2 × 150 mg, and warfarin, respectively).12 A thrombus was found in 1.8% of patients treated with dabigatran 2 × 110 mg, 1.2% treated with dabigatran 2 × 150 mg, and 1.1% treated with warfarin. Unfortunately, no data on the rate of echocardiographic examinations and their results have been published in the ROCKET-AF (rivaroxaban) and ENGAGE AF-TIMI 48 (edoxaban) study populations13,15 (Table 2). An analysis of the studies comparing NOAC and VKA in patients undergoing electrical cardioversion obtained the following results regarding the incidence of thrombus in the LAA: ENSURE-AF study, 8.0% in the edoxaban group and 7.1% in the warfarin group; XVeRT study, 5.1% in the rivaroxaban group and 4.6% in the VKA group; and EMANATE study, 7.2% of patients Table 2. The frequency of LAA thrombus formation in patients treated with oral anticoagulation (data from RCTs) Trial Trial design NOAC No of patients Sample size, n Patients with TEE performed, n Patients with thrombus in LAA, n (%) NOAC VKA NOAC VKA NOAC VKA X-VeRT RCT to determine events after CV Rivaroxaban 1504 1002 502 410 218 21 (5.1) 10 (4.6) ENSURE-AF RCT to determine events after CV Endoxaban 2199 1095 1104 589 594 47 (8) 42 (7.1) EMANATE RCT to determine events after CV Apixaban 1500 753 747 418a 437a 30 (7.2) 31 (7.1) RELY subgroup Post hoc analysis of an open-label RCT Dabigatran 1270 from 18 113 413 – D110 421 – D150 436 165 – D110 162 – D150 88 3 (1.8) – D110 2 (1.2) – D150 1 (1.1) ROCET AF subgroup Post hoc analysis of an open-label RCT Rivaroxaban 321 from 14 264 underwent ECV, PCV, catheter ablation 160 161 No data No data No data No data ARISTOTLE subgroup Post hoc analysis of an open-label RCT Apixaban 540 from 18 201 743 cardioversions 265 275 86 85 0 0 ENGAGE AF-TIMI 48 Post hoc analysis of an open-label RCT Endoxaban 365 from 21 105 632 cardioversions 140 – E60/30 111 – E30/15 114 No data No data No data No data aEMANATE trial – 14 patients from 855 underwent only computed tomography. NOAC, novel oral anticoagulant; VKA, vitamin K antagonist; TEE, transoesophageal echocardiography; LAA, left atrial appendage; CV, cardioversion; D110, dabigatran 110 mg; D150, dabigatran 150 mg; E30, endoxaban 30 mg; E60, endoxaban 60 mg; ECV, electrical cardioversion; PCV, pharmacological cardioversion; RCT, randomised controlled trial.
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