Straining for the answers in stroke - a meta-analysis on left atrial strain as a predictor of stroke

Abstract Background/introduction The pathophysiological relationship between atrial fibrillation (AF) and stroke, has recently come under much scrutiny. Prolonged cardiac monitoring is identifying both more, and shorter runs, of AF. However, this has not been translated to meaningful reductions in stroke incidence. This apparent paradox has led to the spotlight being focused on a new paradigm – namely the concept of a pro-thrombotic atrial cardiopathy, independent of AF. Purpose Functional measures of left atrial function, such as reservoir strain (LARS) (figure 1), have consistently been shown to be an effective predictor of AF, but may reflect a subclinical atrial cardiopathy. A variety of electrical and mechanical factors, in both the atria and the ventricles, influence LARS. Given that LARS will be affected by even small, regional left atrial changes, it is understandable why it may reflect a more sensitive marker of atrial pathology, and thus identify atrial cardiopathy. Identifying relationships between atrial cardiopathy and stroke, may help advance pathophysiological understanding, as well improve targeting of both continuous monitoring and secondary prevention strategies. The aim of this work was to systematically review published literature associating LARS and the development of stroke. Methods The electronic databases PubMed, Embase, Google Scholar, Scopus and Web of Science were systematically searched using the key words "atrial strain" and "stroke" from inception to April 2024. An initial titular analysis, followed by abstract and full text screening was performed. Data was extracted using a pre-specified collection form. A random-effects model with generic inverse variance weights was utilised to pool the most adjusted effect measure from each paper. Results After excluding duplicate studies, 2177 studies were screened, with 101 full-texts being assessed for eligibility. A total of 8 studies were identified that associated LARS and subsequent stroke, and were pooled for meta-analysis. In the pooled studies a total of 17223 patients were included with 1266 cases of incident stroke. The meta-analysis of the studies suggested that a 1% reduction in LARS associated with a pooled hazard ratio of 1.13 (95% CI 1.06-1.22) for incident stroke (figure 2). This implies that impaired LARS is associated with a higher incidence of stroke, independent of the presence of AF. Sensitivity analysis by removing one study at each time did not significantly alter the results. Conclusion This comprehensive meta-analysis including 17223 patients from 8 studies, emphasises the association between changes in LARS and future stroke. Further work is required to explore whether this effect reflects a pro-thrombotic atrial cardiopathy. If so, this may have important therapeutic and monitoring implications, especially in patients who are already felt to be at risk of future stroke.Calculating left atrial strain Forest plot: LA strain and stroke