The impact of mitral regurgitation on the incidence of stroke in patients with atrial fibrillation
Authors: Hieda M , Ono Y , Moriyama S , Kisanuki M , Ishiguro C , Sato S , Fukuda H , Akashi K 
Published: October 2022

Abstract

Background
Stroke is a significant cause of mortality and a leading cause of disability in elderly patients. Atrial fibrillation (Af) is the most common cardiac disease with assumed embolic stroke. Therefore, patients with Af need anti-coagulant therapy with a Warfarin (vitamin K antagonist) or a DOAC (Direct Oral Anti-Coagulant), also considering the risk and benefit net balance. It has been suggested that significant mitral regurgitation (MR) and its vortex jet in the left atrium might reduce embolic stroke source in patients with Af. However, the effect of MR on the risk of stroke in patients with Af is still controversial. Therefore, we hypothesized whether MR might be associated with a lower risk of thromboembolic events in patients with Af.

Purpose
This study aims to investigate whether MR was associated with a decreased risk of stroke in patients with Af, especially in the elderly population.

Methods
We studied 1,714,955 patients in the LIFE Study database, comprising Japanese claims data for public insurance policyholders between 2014 and 2020. We identified 51,939 patients with new-onset Af. Among them, patients with pre-existing stroke patients (N=28,519) were excluded, and new-onset Af patients without stroke (N=23,420) were obtained. Based on the baseline information, the Af patients were stratified into the MR group (N=3,439) and Without-MR group (N=19,981). Propensity score matching (the nearest neighbor method with a caliper of 0.2) was performed to balance baseline features and stroke risk factors between the MR group (N=3439) and the Without-MR group (N=3439). Propensity scores were estimated using logistic regression with age, sex, and all factors in Elixhauser's comorbidity system. The incidence rate of the stroke (events per person-year) was calculated by the event numbers divided by the overall period for the observations months × 12. Kaplan-Meier curves of stroke-free survival were generated, and the two groups' comparisons were performed using the log-rank test.

Results
As expected, patients' characteristics were comparable between the two groups. The observation period was 3 years for both groups. In the MR group, 136 patients with stroke were detected. On the other hand, 122 patients with stroke were detected in the Without-MR group. The incidence rate of the stroke per person-year was 0.027 and 0.025 events per person-year in patients with the MR and Without-MR groups. In addition, the Kaplan-Meier analysis showed that the incidence rate of stroke was comparable between the two groups (P=0.43).

Conclusions
The frequency of stroke in patients with atrial fibrillation was similar, despite mitral regurgitation. Therefore, patients with atrial fibrillation should have anti-coagulation therapy, regardless of the presence or absence of mitral regurgitation.

Funding Acknowledgement
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by grants provided by the Japan Science and Technology Agency (JST) Fusion Oriented Research for disruptive Science and Technology (FOREST) Program (Grant Number: JPMJFR205J) and the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI) Program (Grant Numbers: JP20H00563 and JP19K21590).