I will go with the last response. As for as I understand, we have never quantified Atrial muscle mass properly even in normality. One may be tempted to think there is no purpose to measure it, other than academic reasons. The fact that the incidence of atrial fibrillation in mitral stenosis is not linearly correlating with LA size makes us think, LA mass (Virtual LAH) may have a say in triggering AF.
This post is meant for cardiology fellows. Maybe someone can do a study on this by measuring LA mass pre and post-PTMC, we might get an idea about regression as well. Meanwhile, we are well versed with infiltrative diseases like atria like amyloidosis that can mimic LAH. Currently, we realize fatty infiltration of LA is the common trigger for AF in varied populations.
By the way, readers are welcome to post any specific formula to measure LA mass if they come across .
Reference
A good review of LA anatomy.
Dr.S.Venkatesan MD 