The Heart Rhythm Society 2021 Scientific Sessions took place in Boston between June 28–31, 2021, as a hybrid conference with both virtual and in-person attendees seeking expert-led didactic education to evaluate ground-breaking science. The conference also showcased its annual late-breaking clinical trials session. This year, one of the studies presented provided an answer to a question that has never been addressed by a randomized clinical trial — until now.
Catheter placement into the left-sided cardiac chambers can lead to thrombus, char, or coagulum formation during ablation, and this may embolize, causing a perioperative stroke. Stroke prevention during catheter ablation for left atrial and ventricular arrhythmias is critical given the risk for intraoperative thromboembolism. This endangerment is mitigated intraoperatively by administering intravenous unfractionated heparin or bivalirudin to maintain activating clotting times > 300 seconds. Atrial fibrillation (AF) ablation patients are re-initiated on their pre-procedure oral anticoagulation for stroke prophylaxis post-ablation. Patients requiring catheter ablation for premature ventricular complexes and ventricular tachycardia are not usually on preoperative anticoagulation and are, therefore, not generally initiated on postoperative anticoagulation.
There are currently no evidence-based guidelines directed at medical therapy for stroke prevention after left ventricular catheter ablation despite its inherent risk. Periprocedural stroke incidence is on average 1.5% for left chamber ablations. Just as concerning is the incidence of post-ablation subclinical thromboembolism noted in brain MRIs which may result in cognitive decline.
Possible etiologies of left ventricular (LV) cavity ablation causing a stroke are char or thrombus from the ablation site, catheter dwells time, reduced LV function, and plaque embolism when utilizing a retrograde aortic approach to access the LV. Catheter tip irrigation has not been sufficient to prevent char formation or embolism from myocardial tissue once ablated. Until now, no randomized clinical trial assessed the safety and efficacy of postoperative anticoagulation for stroke prevention until the STROKE VT trial was presented during the late-breaking session by Dr. Lakkireddy, from the Kansas City Heart Rhythm Institute and Research Foundation, Overland Park, Kansas.
Two hundred forty-six patients were randomized 1:1 to receive either post-operative direct oral anticoagulant (DOAC). Fourteen patients were on dabigatran, 40 on rivaroxaban, 69 on apixaban, and 123 on aspirin (ASA), with the ASA dose being 81 mg. Investigators assessed stroke/transient ischemic attack (TIA) incidence via brain MRI at 24 hours and 30 days post-procedure. The secondary endpoints were a composite of vascular or pericardial complications, heart block, thromboembolic event excluding stroke/TIA, and in-hospital mortality. 75% had a VT ablation, mean age 60 years, and 18% were female. The two groups were equally balanced, comparing all baseline variables except that in the DOAC group, 81% had VT ablation with 53% amiodarone use. The 30-day odds ratio (OR) for stroke/TIA in ASA compared to the DOAC group was 12.6 (95% confidence interval, 4.10-39.11; P < .001). The OR for cerebral lesions noted on brain MRI at 24 hours was 2.15 (95% CI, 1.02-4.54; P = .04) and at 30 days was 3.48 (95% CI, 1.38-8.80; P = .008) for the ASA group. A worrisome finding is the OR was 2.6 for stroke when comparing the retrograde aortic approach versus a transeptal catheterization (95% CI, 1.06-6.37; P = .04). A major difference was the ablation time; catheter dwell time was much higher in the DOAC group (2094 sec) versus the ASA group (1707 sec). The primary endpoint of CVA/TIA was higher in the ASA group (P = 0.001). The asymptomatic cerebral event rate on brain MRI at both 24 hours and 30 days was statistically higher on the ASA group compared to the DOAC group (24 hours P=0.03, 30 days P=0.006).
In a multivariate analysis, the predictors of clinical and subclinical cerebral events were ASA use (P<0.001), ejection fraction (P=0.009), retrograde aortic access (P=0.004), and ablation time (P=0.003). Notably, despite direct oral anticoagulation or ASA use, there was no statistically significant difference in mortality and bleeding complications between the two groups.
The trialists nicely summarized some limitations of the study, and one of the most important ones is the etiology of the brain lesions noted on MRI. It can be hypothesized that they are all related to embolism from catheter placement in the left ventricular cavity. However, there are other causes as well, including thrombus on the tip of the catheter, transseptal needle tip thrombus, aortic atheroma, prolonged hypoperfusion, or plaque shift when accessing the retrograde aortic approach via the aortic valve. A limitation of this study is that only 81 milligrams of aspirin were used for stroke prevention. It's unclear if 325 milligrams would have provided any added protection. In addition, it remains unclear if dual antiplatelet therapy would have afforded any additional benefit compared to aspirin alone. The study was not designed for long-term follow-up to assess for a neurocognitive decline in patients that had a positive brain MRI scan for thromboembolism. Finally, the crossover rate was high, with 8.9% of the patients in the aspirin group receiving direct oral anticoagulation post-ablation.
This study may influence guideline committee writers and redirect our post-ablation protocols. The safety and efficacy of DOACs in this realm are considerable. More work is needed to assess the impact of the subclinical findings on brain MRIs post-ablation and whether DOAC use prevents cognitive decline in these cases.
Dr. Chirag Sandesara is employed by Virginia Heart. He has no conflicts of interest to report.