We have read extensively about LV pressure volume loops . What about Left atrial pressure volume relationship ?
This could be vitally important to understand left atrial failure . While, it is often taught that , LA comes to the rescue of left ventricle at time of stress , we rarely talk about left atrial failure !
Where will the LA look for help when it is stressed ?
Pulmonary veins ? , No , the LA simply succumb and patient deteriorates.The only way it can react is by a panic response and starts fibrillating !. This is what happens in many cases of dilated cardiomyopathy and late stages of aortic valve disease . This AF is very poorly tolerated . ( Of course , we do not understand fully , why AF is relatively well tolerated in severe mitral stenosis , inspite of very high LA pressures Often >40mmHg?)
The importance of left atrium as a mechanical chamber is well recognised .It is supposed to empty the blood it receives from pulmonary veins within a narrow pressure zone of 8-12mmhg within a fraction of a second. Even a slight increase in LA pressure may result in pulmonary venous regurgitation and the incoming venous tides are reversed(“a” reversal in pulmonary vein echo ) that results in the so called pulmonary congestion /Pulmonary venous hypertension.
If only god has created additional pulmonary venous valves** at it’s entry , LA can perhaps a relax a little bit . But it is not the case . So, LA function becomes as vital as LV.
(**Can we create pulmonary venous check valves ? . . . will it be an answer for preventing recurrent LVF in cardiomyopathies etc)
Here is an article from European heart journal , which gives great insight into Left atrial function.
The one that has fascinated me is the LA pressure volume loop.
The two pressure waves in left atrium reflect distinct properties . “v” wave is a volume dependent wave and “a” wave a pressure generated wave . Surprisingly the volume dependent wave generates more pressure than the atrial contraction wave.(Note in LA v > a while in RA a>v)