Discussion
Infection prevention strategies during the COVID-19 pandemic have impacted the workflow significantly at high volume centers performing catheter ablation of AF. Omission of routine pre-ablation TEE use in appropriately selected patients is associated with improved workflow efficiency in the EP laboratory and promotes cost-effective utilization of health care resources. Additionally, it may reduce the risk of viral transmission to health care providers. We investigated the safety of a pre-ablation CT-only imaging protocol for the evaluation of LAA thrombus at our center to minimize the use of pre-procedural TEE. The following are the main findings of our study: 1) Implementation of pre ablation CT-only imaging strategy with selective use of TEE for LAA thrombus evaluation does not lead to significantly increased CVE risk; 2) Incidence of peri-procedural CVE is low; 3) Patients with CT imaging suggestive of LAA thrombus may have TEE imaging that is negative for thrombus.
Previous studies have investigated the sensitivity and specificity of pre-ablation CT by comparing it with TEE and reported conflicting findings3-6,8,11-13. Our study design precluded head-to-head comparison of pre-ablation CT with TEE for LAA thrombus evaluation. Nevertheless, our study provides data for the utility of pre-ablation CT-only approach to LAA thrombus assessment during the COVID-19 pandemic and supports the findings of previous reports7-9published during the non-COVID era. Bilchick et al7, demonstrated the safety of the pre-ablation CT-only approach to assessment of LAA thrombus in low-risk patients undergoing AF ablation7. However, unlike the current study, they restricted the use of pre-ablation CT-only protocol for LAA thrombus evaluation to patients with PAF, without a history of prior CVE/LAA thrombus and CHA2DS2-VASc score <4. In contrast to previous studies7-9, which included patients with low to intermediate stroke risk based on a younger age of the study cohort, lower CHA2DS2-VASc score and lower burden of comorbidities, our study included patients at a high stroke risk given a higher burden of comorbidities, older age, and a higher CHA2DS2-VASc score. Moreover, in our study, the pre-ablation CT-only protocol for LAA thrombus evaluation was offered to all the patients regardless of the previous history of stroke/TIA, type of AF, and CHA2DS2-VASc score. Additionally, we followed the current practice of minimally interrupted peri-procedural anticoagulation protocol with DOAC.
Similar to the previously published reports, our results suggest that the incidence of peri-procedural stroke following atrial fibrillation ablation remains low8,14. However, an interesting finding of our study is the development of peri-procedural stroke in a patient with unremarkable pre-ablation CT. Previous investigations4,5,7-9,11suggest that pre-ablation CT has a high sensitivity for LAA thrombus detection. Nevertheless, it is possible that our patient had a false-negative CT result, or that he had an embolic event from a different source (air embolism from a transseptal sheath; char at the catheter tip; non-LAA cardiac thrombus)15,16. Previously published reports suggest an increased propensity for LAA thrombus formation in patients with PsAF, and high CHA2DS2-VASc scores3,13,17. Whether patients with PsAF and high CHA2DS2-VASc scores would benefit from the routine use of pre-ablation TEE regardless of pre-ablation CT findings is a topic worthy of further investigation.
The findings of our study should be interpreted with attention to the associated limitations, including: 1) Those limitations inherent to a single-center, retrospective, and observational study; 2)We could not perform the adjusted predictor analysis for CVE given the low event rates; 3) The anticoagulation protocol at our center may be different from other centers, limiting the generalization of our findings; 4) There may be an underestimation of subclinical CVE or silent cerebral infarcts given the fact that not all the patients underwent post-procedural cardiac magnetic resonance imaging evaluation.5) We cannot exclude the possibility of a significant difference in a larger patient cohort.
In conclusion, based on our experience, implementation of pre ablation CT-only imaging strategy with selective use of TEE for LAA thrombus evaluation does not lead to significantly increased CVE risk during the COVID- 19 pandemic, has greater physician acceptance, and improved workflow efficiency. Further prospective randomized studies are required to identify the patients deriving the maximum benefit from pre-ablation TEE.