How to estimate LV ejection fraction rapidly at the bedside , without echocardiography ?
Posted Mar 12 2010 6:38am
The LV ejection fraction , is the most revered medical parameter for both physicians and cardiologists.There are anesthetists and surgeons , who do not operate a cardiac patient without knowing it.There are physicians who do monthly assessment of EF in their patients with dilated cardiomyopathy.
Now ,every one is interested to know what is their EF ? Thanks to the global information highway .We witness , patients who are extremely delighted when their EF increases from 45% to 48% . Similarly , they get depressed when it falls by 2% .
Why this hoopla around the LV EF ?
Every one knows EF is nothing but a LV contractile force at a particular beat of the heart . It is possibly a crudest possible way to screen for LV function.( Of course it can still be useful in patients with established myocardial disease to follow up LV dysfunction)
The most important caveat in EF is it’s dependence on the loading conditions of heart .It is also heavily influenced by the heart rate.We now, even a severely dysfunctional LV can contract vigorously with inotropic stimulation like dobutamine or whenever local catecholamines.
Our obsession with EF is complete and it is not expected to get cured in the near future.
There are many hundreds of articles in cardiology literature which ridicules the EF as sole parameter for assessing LV function. Still , it is the number one parameter to asses LV function in real world as well as in vast number of land mark clinical trials . Are all those trial results to be doomed ?
Even as the LV EF is being labeled as futile index , we also realise we have not traveled far from our great clinical ancestors . Thousands of years ago the Chinese yellow emperor of medicine found the cardiac contractility by pulse volume and predicted death accurately , probably better than the live 3d echocardiography derived EF guided by LV volume rendering algorithm !
The purpose of this article is to tell the current generation physicians there are some simple and probably accurate clinical tips to rule out significant LV dysfunction.
One can confidentially tell the LV EF would be > 50% in 99% of population if they have the following !
A brisk upstroke of carotid pulse.*
A well palpated tapping apical impulse**
A Loud first heart sound(S1)
A totally normal ECG (Even a normal QRS complex is suffice !) ***
Normal CT ratio in Xray chest
A comfortable brisk walk of at 6 km/hour for 10 m .
* A brisk central arterial pulse is nothing but the reflection of LV DP/DT a sophisticated echo parameter assessed with much hype ! A good thumb with an alert brain can accurately tell a given patients dp/dt is within normal range.
** A loud S1 and tapping apical impulse indicate the velocity of closure of anterior mitral leaflet.Which is in turn reflect the force of contraction of the antero lateral papillary muscle of LV .So what you hear a loud s1 is nothing but the contractile function of the most important part of LV namely the pap muscle of LV.
*** A normal ECG , generally tells us all is well with LV myocardium . Finally, it makes immense sense to correlate the functional capacity to EF. (90% correlation)
Mind you , all the above modalities come either free of cost or a fraction of echocardiography . It is estimated up to 90% echocardiography scans to R/O LV dysfunction can be avoided . The global health care costs can be saved and be utilised for some better purpose like protecting our atmospheric shell from the hazardous gases
Note of caution
While ,one can rule out signficant LV dysfunction by above mode , it can miss other forms of LV dysfunction like relaxation defect etc . (ofcourse the EF also misses it !) .Judicious use of functional imaging modalities are adviced in those who require it.