LV ejection fraction (EF) is the most commonly used LV systolic functional index.Since , it is an easily acquired parameter, it’s popularity has zoomed among both learned and novice cardiology professionals .(Not withstanding the serious shortcomings!)
In one of the evening rounds in my CCU , a young cardiology fellow told me about a patient with acute anterior MI with ST elevation V1 to V5.
The patient was lying supine with trunk up . HR was 110 . BP was 100 /70 There were few basal crackles .The patient was undergoing lysis with streptokinase.
It was suggested to me by the fellow that the patient is going in for “Impending cardiogenic shock since his EF is just 30%”
That prompted me to ask this question
How good is the EF a measure of size of MI during STEMI ?
EF during STEMI is highly variable parameter.The following are important con-founders in LV EF measurement during STEMI.
- Acute ischemia induced LV dysfunction .(Ischemic stunning from the watershed zone significantly over estimate LV dysfunction)
- Mitral regurgitation if present will underestimate it
- Effect of tachycardia and bradycardia can be significant
- The posture of the patient and measurement errors (A good Simpson score is rarely possible in a sick patient )
- Associated hemo -dynamic drugs like NTG/Dopamine etc which alter pre and after load and changes the frank starling forces.
* Please recall , LV EF is never included as a criteria to diagnose cardiogenic shock, confirming the flimsy nature of this parameter during acute phase of STEMI !
The purpose of echocardiography during STEMI is to rapidly identify any mechanical complication , not to waste time in calculating EF.
EF is not a good indicator to quantify the extent of STEMI or it’s prognosis. LVEF cannot be used to risk stratify STEMI in the first 48 hours .One can expect the true LV function to prevail only at discharge.
Ideally ,LV function should be reevaluated by 2 weeks to get a fair idea of true myocardial function .By this time all confounders will resolve.
Since many of us are suffering from an academic obsession and blindly follow the scientific guidelines, a hurriedly diagnosed “severe” LV dysfunction post STEMI may land our patients to inappropriate intervention !