atrial fibrillation ( af ) is a common arrhythmia affecting 1% of the general population increasing to 18% for those over 80  years old . af can cause turbulence in the blood flow within the heart resulting in clot formation . clots can then migrate to the peripheral circulation resulting in stroke or limb thromboembolism [ 24 ] . this risk ranges from 5 to 7% in non - anticoagulated patients and is affected by other factors reflected in the cha2ds2vasc risk score : congestive heart failure , hypertension , age , diabetes mellitus , previous stroke , vascular disease history , and gender [ 5 , 6 , 10 ] . the current recommendation is , therefore , to anticoagulate for at least 3  weeks before cardioversion and 4  weeks after the procedure to minimize the risk of embolization [ 711 ] . traditionally , the vitamin k antagonist , warfarin , has been used ; however , this agent has considerable limitations as it can take time to get patients into target international randomized ratio ( inr ) range , and they run the risk of having dccv canceled if their inr is out of range . the rate of success of dccv in af is largely affected by the duration of the af ; a shorter duration of af is associated with a higher rate of success of dccv and less relapse . the use of doacs in this setting to achieve rapid stable anticoagulation is , therefore , an attractive option . the availability of the direct oral anticoagulants ( doacs ) has dramatically changed the anticoagulation landscape . dabigatran is a direct thrombin inhibitor ( dti ) that has several advantages over warfarin . dabigatran has rapid onset of action with peak plasma concentration within 60  min and a half - life between 12 and 17  h . dabigatran has a stable pharmacokinetic profile , and there is , therefore , no need to monitor use with blood tests in most patients . this study aimed to compare the safety and efficacy of dabigatran and warfarin around dccv in terms of stroke prevention , time taken to get to dccv , and the success of cardioversion in achieving sinus rhythm . a retrospective study of sequential patients referred for elective dccv to basingstoke and north hampshire hospital over 12  months running from september 2013 to september 2014 . patients were divided into two cohorts ; cohort a received dabigatran , while cohort b was managed with warfarin . all patients with non - valvular af planned for dccv were included in the study . patients managed with chemical cardioversion and those with mechanical valves and severe valvular heart disease were excluded from the study . patients who started on anticoagulation with warfarin or dabigatran for dccv were eligible for the study . those already on warfarin or dabigatran for another indication ( pulmonary embolism ) were also included . their inr was checked weekly until the time of dccv with target inr of 23 . in line with normal practice , if the inr was not within the therapeutic range , the procedure was canceled pending adjustment of the dose of warfarin until the inr within the therapeutic range . patients who were on dabigatran had baseline screening blood tests with coagulation profile , urea and electrolyte ( u&es ) and liver function tests ( lft ) with no further blood tests if results were normal / stable . only patients with stable renal function and creatinine clearance above 30  ml / min commenced on dabigatran . dabigatran was initiated at a dose of 110  mg twice daily for people over 75  years old and 150  mg twice daily for people less than 75  years old . on the date of the procedure , a written consent obtained from the patient after a discussion with risks and benefits of dccv . in addition , the duration of dabigatran therapy was reviewed ensuring that a full course of 3  weeks had been taken , and if more than two doses had been missed , the procedure was canceled and rescheduled for another date . the following data were collected : patient diagnosis , patient demographics , comorbidities , including cardiovascular risk factors ( cha2ds2vasc ) , time between the referral for af and the date of dccv , the rate of cancelation and rescheduling of dccv , and the success rate of dccv in restoring sinus rhythm . clinical outcomes , including cerebrovascular accident , transient ischemic attack , and peripheral arterial embolism , and bleeding events , were evaluated during 68  weeks of post - procedure follow - up . differences between categorical values were analyzed using pearson s chi - square test and fisher s exact test , while the mann whitney u test was used for continuous values . a p  value less than 0.050 was considered statistically significant . this article is based on previously conducted procedures and does not involve any new studies of human or animal subjects performed by any of the authors . 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 cha2ds2vasc score of between 0 and 3 , while only 10.3% ( 11 out of 107 ) had a cha2ds2vasc score of between 4 and 9 . for patients receiving dabigatran , the average cha2ds2vasc 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 cha2ds2vasc between cohort a and cohort b ( table  1).table  1background data and outcome : cohort a versus cohort bcategorydabigatran ( cohort a)warfarin ( cohort b ) 
 p  valuenumber of patients , n 
 5442mean age    sd ( range ) , years64.0    10.9 ( 2582)66.9    8.0 ( 4584)0.124 
 gender , n n 
 23130.795 
 diabetes mellitus , n 
 470.158 
 vascular disease , n 
 770.610 
 cerebrovascular accident , n 
 320.862 
 mean cha2ds2vasc score    sd1.9    1.82.3    1.30.291 
 interval between referral and dccv ( days)51800.001 
 cancelation and rescheduling of dccv390.219 
 dccv with successful outcome33220.391 

 dccv direct current cardioversion , sd standard deviation 
 mann  whitney u test 
 pearson s chi - square test 
 fisher s exact test 
  background data and outcome : cohort a versus cohort b 
 dccv direct current cardioversion , sd standard deviation 
 pearson s chi - square test 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 majority of the patients ( 73% ) received one dccv ; 16% and 11% required 2 and 3 dccv , respectively . at 620 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 ) . 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 , 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 620  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 . 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  2analysis of patients who received direct current cardioversion within 45  days and outcome ; patients with background of heart failure and outcomecategorynumber of patientssuccess rate 
 p  valuenumber of patients with 45  days referral  total3222 ( 69%)0.165  cohort a ( dabigatran)21  cohort b ( warfarin)7heart failure patients  total3828 ( 73.7%)0.009  cohort a ( dabigatran)2017 ( 85%)0.006  cohort b ( warfarin)1811 ( 61%)0.327 
  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 ) . 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 . the relatively higher cost of dabigatran (  75.60 per month ) may limit its use in comparison with warfarin (  0.861.67 per month but with additional monitoring costs ) . in the uk , it is estimated that the overall cost for outpatient dccv is approximately  722 , and this cost is predicted to be higher with cancelation and rescheduling . shorter duration between the onset of af and the date of dccv is associated with a higher probability of successful dccv . the use of dabigatran in comparison with warfarin facilitated earlier dccv with a lower probability of rescheduling due to inadequate anticoagulation . sufyan benamer , debbie lusty , and tamara everington declare that they have no conflicts of interest . this article is based on previously conducted procedures and does not involve any new studies of human or animal subjects performed by any of the authors . this article is distributed under the terms of the creative commons attribution - noncommercial 4.0 international license ( http://creativecommons.org/licenses/by-nc/4.0/ ) , which permits any noncommercial use , distribution , and reproduction in any medium , provided you give appropriate credit to the original author(s ) and the source , provide a link to the creative commons license , and indicate if changes were made .
introductiondirect current cardioversion ( dccv ) is considered as the most effective treatment for atrial fibrillation ( af ) . 
 af is associated with an increased risk of thromboembolism , and dccv may increase this risk . 
 the current recommendation is , therefore , to anticoagulate for at least 3  weeks before dccv and 4  weeks after the procedure.methodsa retrospective study of patients referred for elective dccv as treatment for af in hampshire hospitals nhs foundation trust was performed to compare the safety and efficacy of dabigatran with warfarin in this setting.resultsduring a 12-month period , 129 patients were referred for dccv for the treatment of af and 107 patients received dccv . 
 fifty - four patients were anticoagulated with dabigatran , 42 patients with warfarin , and 11 patients with other direct oral anticoagulants ( doacs ) with choice of agent determined following an informed discussion with the patient . 
 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 warfarin , this was 82 ( p  =  0.001 ) . 
 the proportion of cancelation and rescheduling for warfarin patients was 21.4% , while for dabigatran , this was 5.5% . 
 patients were reviewed 620  weeks after dccv ; the success rate of dccv for dabigatran patients was 61% , whilst for warfarin patients , this was 52% . 
 the success rate went up to 69% for patients who received dccv within 45  days of referral ( p  =  0.165).conclusionthis retrospective study supports clinical experience that dccv is more likely to be successful when there is a shorter duration between the onset of af and the date of dccv , and shows that the use of dabigatran in comparison with warfarin facilitates earlier dccv .