Several cardiac imaging modalities are able to visualize the left atrium (LA) and, therefore, allow for quantification of both structural and functional properties of this cardiac chamber. In echocardiography, only the maximal LA volume is included in the assessment of diastolic function at the current moment. Numerous studies, however, have shown that functional measures may be superior to the maximal LA volume in several aspects and to possess clinical value even in the absence of structural abnormalities. Such functional measures could prove particularly useful in the setting of predicting atrial fibrillation, which will be a point of focus in this review. Pivotal cardiac magnetic resonance imaging studies have revealed high correlation between LA fibrosis and risk of atrial fibrillation recurrence after catheter ablation, and subsequent multimodality imaging studies have uncovered an inverse relationship between LA reservoir function and degree of LA fibrosis. This has sparked an increased interest into the application of advanced imaging modalities, including both speckle tracking echocardiography and tissue tracking by cardiac magnetic resonance imaging. Even though increasing evidence has supported the use of functional measures and proven its superiority to the maximal LA volume, they have still not been adopted in clinical guidelines. The reason for this discrepancy may rely on the fact that there is little to no agreement on how to technically perform deformation analysis of the LA. Such technical considerations, limitations, and alternate imaging prospects will be addressed in this review.
Aims We aimed to investigate whether left atrial (LA) markers from cardiovascular magnetic resonance (CMR) were able to predict atrial fibrillation (AF) in elderly patients with risk factors for stroke. Methods and results At baseline, 203 participants with stroke risk factors but without history of AF underwent advanced CMR and received an implantable loop recorder. During a median of 40 (37–42) months of continuous monitoring, incident AF was detected in 79 patients (39%). With regards to CMR markers, a steep increase in incidence rate of AF was seen with LA maximum volume (LAmax) above 55 mL/m2, LA minimum volume (LAmin) above 30 mL/m2, LA total emptying fraction (LA TEF) below 45%, LA active emptying fraction (LA AEF) below 37%, LA strain S below 25%, LA strain A below 17%, and LA strain rate A above −1.7 s−1. After multivariate adjustment, the above-mentioned CMR markers remained associated with AF incidence: hazard ratio (95% confidence interval) 1.25 (1.06–1.48) and 1.51 (1.22–1.87) per 10 mL/m2 increase of LAmax and LAmin, respectively, 1.49 (1.26–1.76) and 1.46 CI (1.25–1.71) per 5% decrease in LA TEF and LA AEF, respectively, 1.23 (1.05–1.44) and 1.56 (1.18–2.06) per 5% decrease in LA strain S and A, respectively, and 2.06 (1.31–3.23) per s−1 increase in LA strain rate A. In prediction analyses, LA functional indices increased area under the receiver operating characteristic curve significantly. Conclusion The risk of AF, including asymptomatic AF, increases significantly with increasing LA volumes and worsening LA function.
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