Though the left atrium is the superior most chamber of the heart , it loses its gravity-assisted LV filling advantage in a lying posture. In patients with compromised heart function, this becomes a symptom defining factor. No surprise, patients during episodes of LVF or paroxysmal nocturnal dyspnea, natural forces make them sit up by default, and bring the LA superior & over the top of LV hence its filling is augmented. One more factor that operates is that, IVC orientation, which assumes slope and reduce venous return velocity. In the process, they decongest the lungs and patient gets Immediate relief. In fact, pillows work faster than diuretics and we can technically call it low-cost LV assit devices.
Note, how the LA takes control by its superior position, when the patient assumes erect posture from supine. In fact ,the number of pillows used, by the pateint has some direct correlation with LA mean and Echo cardiographic E/e ‘ . ESCAPE study suggest a possiblity of correlation of this LVEDP with right sided JVP as well.( Drazner et al Circ Heart Fail. 2008 )
Final message
This post may not be relevant to cardiology fellows. Whenever we receive a dyspneic patient in heart failure, prop them up with few pillows. This lesson is taught right in the first-year clinical rounds. I wanted to highlight the anatomical and hemodynamic basis of the sitting-up posture and its impact on LA mean and LVEDP. By some crazy stretch of imagination, pillows can be referred to as a temporary LV assist device.
Research suggestion for fellows
Some of you can do you a study in cath lab, how much the LA mean pressure is altered with reference to posture. It could appear a flimsy study in this era of TAVR/Mitra clips. Sill, we have an good opprtunity to analyse these things as we enter all chambers of heart in routine fashion for some indication or other. This will make us understand LV filling physiology in a better way. (Recalling the days of Guyton & Rushmer when they strugggled to know computational models to measure the pressure gradients)
A question for our hemodynamic acumen ?
How does the LA empty in to LV , when LV inflow conduit need to operate against gravity during head down feet up postion as in many sports like bungee jumping or in some asanas (Shirshasana) . Has any one attempted, to know , how would be the E and A velocity across the mitral valve in this posture .Wish some one take on this and report ,if no one has done it before please add some credit . (Just kidding)
Caution
Patients (even some healthy) with diastolic dysfunction especially in elderly, should never attempt to do such sports or indulge in any compromised posture that brings LA below the LV.
Dr.S.Venkatesan MD 