During the period of 12 months from September 2013 to September 2014, 129 patients were referred for elective DCCV for the treatment of AF with 107 patients actually receiving DCCV. The majority of referred patients 98.1% (105 out of 107) was newly started on oral anticoagulants, and only two (1.9%) patients were already receiving anticoagulants for the indication of pulmonary embolism. Fifty-four patients who received DCCV were on dabigatran (50.5%; Cohort A), 42 patients were on warfarin (39.2%; Cohort B), and 11 patients were on another DOAC (10.2%).
Twenty-two patients were canceled for various reasons; 4 patients with low INR (18%), 4 patients (18%) returned spontaneously to sinus rhythm, while the remaining cancelations were either because the patient was too unwell to receive DCCV or because they had been referred for ablation.
The majority of the referred patients (96 patients; 89.7%) had a low CHA2DS2–VASc score of between 0 and 3, while only 10.3% (11 out of 107) had a CHA2DS2–VASc score of between 4 and 9. For patients receiving dabigatran, the average CHA2DS2–VASc was 1.9 ± 1.8, while for warfarin, the average was 2.3 ± 1.3 with no statistical significance (P = 0.291).
The average age of included patients was 65.45 years, and there was no statistical significance in age between those on dabigatran and those on warfarin. The total number of male patients was 70, and the total number of females was 26, a ratio of 2.7:1. In terms of comorbidities in the total number of patients: 38 had congestive heart failure, 36 had hypertension, 11 had diabetes, 14 had a history of vascular disease, and 5 had previous cerebrovascular disease. There was no statistical difference in comorbidities with CHA2DS2–VASc between Cohort A and Cohort B (Table 1).
Table 1 Background data and outcome: Cohort A versus Cohort B
The average number of days between the date of referral for DCCV and the date of DCCV for patients who were on dabigatran was 51 days, while for patients on warfarin, this was 80 days (P = 0.001); for those who were on another DOAC, this was 50 days (Table 1).
The proportion of cancelation and rescheduling to a later date because of suboptimal INR for warfarin patients was 21.4% (9 out of 42 patients). In contrast, those who received dabigatran had a low rate of rescheduling with only three patients (5.5%) having DCCV postponed due to missing doses (Table 1).
The percentage of immediate success of DCCV with achievement of sinus rhythm was 86%. The majority of the patients (73%) received one DCCV; 16% and 11% required 2 and 3 DCCV, respectively. At 6–20 week review following DCCV, the overall success rate was 57% (61 patients out of 107), and the proportion of patients who failed to maintain sinus rhythm was 46 out of 107 (43%). For those patients on dabigatran, the success rate was 61% (33 out of 54), and the failure rate was 39% (21 patients out of 54; Table 1). In comparison, the success rate for patients on warfarin was 52% (22 patients out of 42; Table 1), and the failure rate were 48% (20 out of 42). Six patients who received other DOACs had successful DCCV. There were no reported cases of cerebrovascular accident, transient ischemic attack, and peripheral arterial embolism or bleeding events in patients who received dabigatran, warfarin, or other DOACs. In addition, no discontinuation of any of the drugs was reported.
As previous studies have shown that shorter duration of AF associated with higher success rate of DCCV and less relapse [15], analysis was made for those patients who had AF duration of ≤45 days. Review of patients with time between referral and date of DCCV ≤45 days included 32 patients out of 107 (30%). Twenty-one patients were on dabigatran, 7 patients were on warfarin, and 4 patients were on another DOAC. At 6–20 week review post-DCCV, the overall success of DCCV in restoring sinus rhythm was 22 patients out of 32 (69%; P = 0.165; Table 2) reflecting a higher success rate in this cohort. This finding was not statistically significant due to the relatively small number of patients. There were a high number of dabigatran patients receiving DCCV within 45 days compared to warfarin, which indicates that dabigatran can be associated with more rapid DCCV and a shorter AF.
Table 2 Analysis of patients who received direct current cardioversion within 45 days and outcome; patients with background of heart failure and outcome
Patients with heart failure represented a large group of 38 (39.8% of the total). Twenty of these patients received dabigatran, while 18 patients had warfarin. The total success rate was 73.7% (28 patients; P = 0.009). The percentage of the success of DCCV for heart failure who received dabigatran was 85% (17 patients; P = 0.006), while for warfarin patients, this was 61% (11 patients; P = 0.327; Table 2).
One of the limitations of this study is the relatively small number of patients in this single-center study; however, the data are comparable with other published studies [1]. The relatively higher cost of dabigatran (£75.60 per month) may limit its use in comparison with warfarin (£0.86–1.67 per month but with additional monitoring costs) [13]. In the UK, it is estimated that the overall cost for outpatient DCCV is approximately £722 [14], and this cost is predicted to be higher with cancelation and rescheduling. Dabigatran may, therefore, be a more cost-effective approach for DCCV.