The left atrium: A reservoir and a witness for risk of symptoms and cardiovascular complications

Abstract

The dilated left atrium was primarily seen as a prognostic marker for disease progression, and indeed the prognostic relevance of left atrium dilatation is well established. It has been largely demonstrated, for instance, in the context of chronic kidney diseases. The left atrium modulates left ventricular (LV) filling by acting as a compliant reservoir, passive conduit and active booster pump. Left atrium-dysfunction and remodelling are commonly observed in patients with heart failure. Growing evidence suggests that left atrium-dysfunction is an active contributor to symptoms. When the left atrium-function is impaired, it can lead to greater haemodynamic stress, promoting pulmonary hypertension and severe symptoms. It is thus fair to spend more time in research on the left atrium. One question to address is the optimal method for assessing in routine clinical practice left atrium anatomy and function. Great works have been performed using cardiac magnetic resonance for the dynamic assessment of LV volumes and fibrosis. The works on the localization and the quantification of left atrium fibrosis appear especially relevant for best treating atrial arrhythmias. But, of note, ablation therapies are also inducing some fibrosis that could be quantified. More easily applied in the clinical routine, echocardiography is now providing the 3D semi-automatic assessment of left atrium volumes and their change from systole to diastole. There is also a lot of work done with the use of speckle tracking technology for detecting left atrium longitudinal deformation. This last technique could be challenged by the impact of LV longitudinal deformation and its impact on the left atrium’s own deformation that we could quantify with the speckle tracking approach. The fact is that the two deformations are not perfectly symmetrical and the strain values are geometry dependent. Left atrium strain is providing additive information to what we are already obtaining when measuring LV longitudinal strain. Therefore, a combined Industry Task Force, the American Society of Echocardiography and the European Association for Cardiovascular Imaging have worked on a consensus paper that is now available and that is promoting the use of speckle tracking echocardiography for the assessment of left atrium function. In the current edition of the journal, PrzewlockaKosmala et al. nicely report the correlation between increased central blood pressure and left atrium structural and functional abnormalities. With respect to pulse pressure, central blood pressure should be less dependent on large arteries’ stiffness than on peripheral haemodynamics. They assessed left atrium reservoir function by speckle tracking echocardiography and they found an association between this approximation of the peripheral arteries’ compliance and the left atrial function. They reach the conclusion that the chronic increase of left atrium afterload impacts significantly on left atrium morphology and function and that left atrium reservoir function should be taken into account as a marker for the diagnosis and management of heart failure with preserved ejection fraction (HFpEF), atrial fibrillation or other complications related to an increase in central blood pressure (Figure 1). Left atrium strain is probably a tool that should be integrated for best defining non-invasively diastolic function and the filling pressure of the left heart. The relationship between left atrium function and HFpEF seems particularly valuable also for the understanding of the pathophysiology of HFpEF and clinical expression. For instance, the assessment of left atrium function might be useful for the classification of different HFPEF phenotypes, for example, that with left ventricular hypertrophy and clear decrease in LV-longitudinal function versus that with rather preserved LV but large left atrium and consequences on the right heart. In addition, there is an important association between HFpEF, left atrium-dysfunction