Left Atrial Volumes in Health and Disease Measured Using Cardiac Magnetic Resonance
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- atrial fibrillation
- heart atria
- heart failure
- magnetic resonance imaging
It is not the size of a man, but the size of his heart that matters.—Evander Holyfield
The Left Atrium in Health and Disease
The left atrium (LA) plays an important mechanical role in cardiac performance. There are 3 discrete phasic functions within the cardiac cycle: first, the LA acts as a reservoir for storing pulmonary venous return during left ventricular (LV) contraction; second, it acts as a conduit because blood is passively transferred into the LV; third, active LA contraction in LV end-diastole contributes significantly to LV filling. It is also responsible for secreting natriuretic peptides in response to stretch, thus, helping to mediate fluid and hemodynamic homeostasis.
See Article by Zemrak et al
Given these various and important functions, it is unsurprising that disturbances of LA morphology are associated with important cardiovascular comorbidities, such as stroke,1 heart failure,2 atrial fibrillation (AF),3 and even premature mortality.4 Overall, LA size has been the most widely investigated atrial characteristic and has been found to be consistently increased in association with these and other cardiovascular complications. Given the enormous and increasing combined public health impact of these diseases, there is significant clinical interest in LA imaging as a potential biomarker to not only identify individuals at increased risk (suggested by the presence of LA remodeling), but also guide potential treatments and assess the therapeutic response—that is, reverse LA remodeling.5
Assessment of LA Size
The traditional metric of LA size has been the anteroposterior LA diameter in ventricular end-systole (ie, maximal atrial dimension within the cardiac cycle), measured from a parasternal long-axis M-mode echocardiographic view. This approach has advantages, given the widespread availability of echocardiography and the ease and reproducibility of this particular measurement. However, the LA is a morphologically complex chamber, and overall volume is more accurately estimated using the biplane area–length method, which combines LA areas and lengths …