Posts Tagged ‘why we take lv end ssytolic dimension for assessing lv function ?’

Regurgitant  lesions of cardiac valves  are often tricky for the heart . Myocardium shows “love- hate” relationship with these  leaky valves.  Some of them are  “sort of”  stress relievers for  LV . A mild MR will make the LV comfortable in terms of wall stress. When the wall stress is reduced the contractility increases and LV EF may raise a little.Hence EF is never going to help us to assess true LV function in MR .

LV end diastolic dimension(LVEDD) is  a preload dependent  parameter .A patient with 6.5cm LV EDD  may still  have good contractility  and he may reach even a  40mm LV ESD, implying an intact LV function.

LV function should be best  assessed  in systole .(After all ,  systole is the prime function of heart) .Further , it should be assessed when the LV is  free from  influence of the all  loading  conditions of heart .  (Note : The initial part of systole  depends on after load. As the systole progresses the influence  of after-load lessens .In the pressure volume loop* , the point at which loading conditions are least operative is end systole.)

* Please realise , heart is a dynamic organ there is no true load independent point in cardiac cycle  as pressure and volume are eternally coupled.

What happens in AR ?

The same rule applies for Aortic regurgitation, but the parameters worsen little later than that of MR. For same degree of regurgitant fraction MR will require early surgery than AR.The reason for better  tolerablity of  AR  is due to largely  intact LA function and compliance till very late stages of AR.(In AR- it’s single chamber volume overload , while in MR  it’s two chambers !)

Final message

LVEDD is not used in assessing MR  as it is a pre-load dependent parameter that will not reflect true myocardial  function /dysfunction. LV ESD is fairly accurate  measure of LV systolic function minus all loading factors .

Watch out  for next topic

Vasodilator therapy in MR and AR : How is it different ?

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