Dr.S.Venkatesan MD

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)

http://eurheartj.oxfordjournals.org/content/22/1/22.full.pdf