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Meeting Highlights: ACC
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Below is a sampling of research underway in atrial fibrillation and stroke prevention, reported in oral and poster sessions at the American College of Cardiology 60th Annual Scientific Sessions and Expo, April 2-5, 2011, in New Orleans.
Radiofrequency Ablation May Reduce Stroke, TIA in Patients with AF
In a retrospective cohort analysis, researchers found a significant reduction in the risk of stroke and transient ischemic attack (TIA) among patients with AF who had been treated with radiofrequency catheter ablation (RFCA).
Patients with AF who underwent RFCA were compared with those treated with at least two antiarrhythmic medications and no ablation. The primary endpoint was a stroke or TIA within 3 years of first ablation or second medication fill. Researchers identified subjects using the Thomson Reuters MarketScan Database, which contains individual claims information from employers, health plans, hospitals, Medicare and Medicaid. They then drew 801 propensity-matched pairs based on 15 characteristics, including patient demographics, comorbid conditions, medication use and prior stroke or TIA.
Using Cox proportional hazards models, researchers showed a reduction in stroke-TIA rates following RFCA, after adjusting for covariates still statistically different after matching, such as time in the database and baseline diabetes (hazard ratio 0.664 [95% CI .45, .98], p=0.04), and after adjusting for prior stroke or TIA (hazard ratio 0.695 [CI .47, 1.00], p=.07).
Reynolds M. Poster Session 1056-395
FRANCIS MARCHLINSKI, MD, RESPONDS:
This study provides more evidence for stroke-risk reduction with catheter-based AF ablation. Matched patients who underwent RF ablation had lower TIA/stroke event rates when compared with patients treated with at least two different rhythm-control medicines. The report supports several single and multicenter observational studies that have identified a very low stroke event rate, even in patients with CHADS2 scores >1, after confirming AF control with monitoring and stopping anticoagulation after AF catheter ablation. The time is right for a prospective, randomized study comparing stroke and bleeding outcomes with and without continued anticoagulation in patients with ECG-documented AF control after ablation. Additional prospectively collected evidence of stroke-risk reduction and elimination of oral anticoagulant use with successful catheter ablation of AF will further endorse the enthusiasm for this important treatment strategy.
Ablation Strategies for Paroxysmal AF May Not Be Equally Effective
Researchers in a prospective, randomized study compared two ablation strategies for maintaining sinus rhythm without medication in patients with paroxysmal AF. They found pulmonary vein isolation with ganglionated plexi (PVI plus GP) superior to the pulmonary vein isolation plus linear lesions (PVI plus LL) strategy.
Consecutive patients diagnosed with paroxysmal AF were randomly assigned to either PVI plus GP (n=74) or PVI plus LL (n=72). Procedures were successful in all targeted veins, and rhythm-control medications were discontinued 2 to 4 weeks after ablation in both groups.
In the PVI plus GP group, after 1 year 51 patients maintained sinus rhythm without medication after the single procedure. Repeat procedures were performed on 16 patients, and the overall success rate in the PVI plus GP group was 59 of 74 patients (79.7%). In the PVI plus LL group, after 1 year 38 patients maintained sinus rhythm without medication. Repeat procedures were performed on 30 patients for an overall success rate of 53 of 72 patients (73.6%).
Romanov A. Poster Session 1020-405
FRANCIS MARCHLINSKI, MD, RESPONDS:
In this well-designed study by Romanov and colleagues, the superiority of adding GP ablation to PV ablation was striking when compared with adding roof and mitral annular lines. The mechanisms for the improved outcome with GP ablation deserves further study. Does GP ablation enhance efficacy when PV reconnection is more likely to recur (first procedure)? Is it less likely to be beneficial when PV isolation is more likely to persist (second procedure)? What is clear from this study is that another nail has been placed in the strategy coffin of deploying linear lesions for paroxysmal AF. In addition to lower efficacy, an atypical flutter rate of 14% with this ablation strategy is unacceptably high.
The study also confirms that we continue to face a sizeable AF recurrence rate, which is almost uniformly due to PV reconnection. Until we accomplish the charge of permanent PV disconnection or at least can reliably confirm reconnection noninvasively, we are left to only speculate, frequently without a sound physiologic rationale, on the “best” additional targets beyond PV isolation required for control of both paroxysmal and more persistent forms of AF.
Dabigatran May Prevent More Strokes Than Warfarin Regardless of Risk Profile
In a subgroup analysis of the RE-LY trial, sponsored by Boehringer Ingelheim, patients treated with dabigatran had fewer annual strokes or major bleeding events—regardless of number of comorbidities—than those treated with warfarin.
Researchers divided patients into groups by CHA2DS2-VASC score, which predicts risk for stroke by assigning patients 1 point each for heart failure, hypertension, age 65-74, diabetes, female sex and vascular disease, and 2 points for previous stroke or TIA and age older than 74.
Distribution of CHA2DS2-VASC scores was 0-2 (n=4,042), 3 (n=5,365), 4 (n=4,374), 5-9 (n=4,327). Subjects in each cohort were randomized to receive dabigatran 110 mg (not available in the United States), dabigatran 150 mg (D150) or warfarin. Researchers calculated relative risks, 95% confidence intervals and p-values for interaction.
Across cohorts, those on D150 had fewer strokes than those taking warfarin (Table). All cohorts except the 5-9 group had fewer major bleeding events on D150.
*Net clinical benefit was stroke, systemic embolism, pulmonary embolism, myocardial infarction, all-cause death and major bleeding.
Source: Oldgren J. Oral Session 906-4
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Oldgren J. Oral Session 906-4
John U. Doherty, MD, RESPONDS:
The previously published RELY trial studied two doses of dabigatran: 110 mg twice a day (D110) (not available in the United States) and 150 mg twice a day (D150) versus warfarin in patients with nonvalvular AF. In RELY, the combined rate of stroke and peripheral embolic events was reduced by 34% with the D150 dose compared with warfarin and hemorrhagic stroke by 74%. Curiously, a slight increase in myocardial infarction was observed in this dose group (p=0.048). The D110 dose was as effective as warfarin in preventng stroke or peripheral embolic events.
The current study further stratified risk among these patients with subgroup analysis using the CHA2DS2-VASC, and investigators evaluated major bleeding and net clinical benefit (defined as stroke, systemic embolism, pulmonary embolism, myocardial infarction, all-cause death and major bleeding).
In patients with CHA2DS2-VASC scores 0 to 2 and 3, the risk of stroke and systemic embolism was equivalent between D110 and warfarin but showed benefit in those with CHA2DS2-VASC scores of 4 and 5 to 9. In comparing D150 and warfarin, a similar benefit was seen in all 4 subgroups with relative risk ranging between .53 and .77.
Major bleeding occurred in fewer patients in groups 0 to 2, 3 and 4, and was equivalent in groups 5 to 9 in the D110 dose group compared with the warfarin group. Likewise, bleeding risk was less in the first 3 groups in the D150 dose group but was increased in the 5 to 9 group.
Net clinical benefit was improved in groups 0 to 2, 3 and 5 to 9, in the D110 dose group compared with warfarin and equivalent in the 4 group. In the D150 dose group, net clinical benenfit was improved in groups 0 to 2, 3 and 4, but was equivalent or worse in group 5 to 9.
Although reduction in stroke risk is consistent with all 4 subgroups in the D150 versus warfarin comparison, risk of bleeding becomes higher with D150 compared with warfarin, and net clinical benefit may be equivalent or worse in patients with the highest CHA2DS2-VASC scores.