Under physiological condition , pre-load , after load , and cardiac contractility should be a sequentially matching parameters . After load mismatch is an important concept , where myocardial contractility is temporarily depressed due to lack of adequate pre-load for a given level of after load .
This is also referred to as descending limb LV function paradox .
The three common clinical situation AL mismatch occurs
- Critical Aortic stenosis (High aortic after load )
- Acute Hypertension (High after Load -Normal and low pre-load)
- Severe diastolic dysfunction (Pre-load is high -After load is normal )
If it happens acutely the myocardium becomes dyfunctional due to mechanical non ischemic stunning .Once the after load comes down the contractility improves .
What is the chronic adoptive response to after load mismatch ?
LVH is the major chronic adoptive response to AL mismatch.
LVH reduces the wall stress which will reduce the after load indirectly .
So LVH neutralises the high after load .Laplace law at work . (Wall stress is equal to 2 times the radius divided by thickness of the wall )
Here is the Link to the great lecture by John Ross Jr in LA Jolla , California in one of the annual scientific session of AHA more than 25 years ago . http://www.ncbi.nlm.nih.gov/pubmed/966366 .The concept is alive and kicking even today .I am sorry to note this important physiological concept never received the attention it deserves . I would vouch , it can be as important as Frank starling principle .