Left ventricular hypertrophy (LVH) is the most common structural abnormality of the heart. Hypertension and LVH are close associates . Still ,not every one with HT develop LVH . So, there obviously is a missing link . Similarly , diabetes in the company of hypertension love to target the heart muscle with more vigour . The incidence of LVH can be near 100% when DM join hands with HT.
So, what is the secret ?
Sustained elevation of afterload due to high BP inflate the myocyte , result in myocyte hypertrophy , which is more of a physiological response. The diabetes mellitus adds some spice to the hypertensive LVH.
Diabetes causes glycation of myocyte cell membrane proteins . This opens the flood gates and the cell permeability barrier vanishes. Hence there is exudate collect in the cardiac interstitium. This is equivalent to diabetic microangiopathy seen in retina and kidneys.
There is well established link between diabetic LVH and microalbuminuria , suggesting a protein leak equivalent in heart (Myocardial proteinuria) . The only difference here , is the protein leaks into the interstitium instead of renal tubules . As we know interstitial leak is a powerful stimulant for fibrotic reaction and new cell growth. Fibroblasts in combination with extracellular matrix and macropahges form a rigid and timid myocardium . If the patient is also a dyslipidemic( which is usually the case !) the leaked LDL , TGL adds to the chaos .
Pathological effects of diabetic LVH
- Increased LV mass
- Early LA enlargement
- Early diastolic dysfunction
- Prevent regression of LVH even after good BP control
Can diabetes per se cause LVH without Hypertension ?
Yes .this is also possible , but it is less recognised.Diabetic LVH can be a part of generalised organomegaly seen.(Right from the days of fetus diabetes has a tendency to increase solid viscera size – Large babies in diabetic mothers , diabetic kidneys rarely shrink !)
Other factors that are related to LVH in diabetes include
- Female Gender
- Insulin resistance
- The lipid connection – Hypertriglyceridmia is linked to LVH
Can tight blood sugar control reverse diabetic LVH ?
We hope so . It may not happen in real life .it depends upon the extent of interstitial invasion of abnormally glycated proteins.
Can echocardiography identify diabetic LVH from hemodynamic LVH of SHT ?
The diabetic LVH is fundamentally different in that , the classical septal hypertrophy is uncommon, instead the overall LV mass is increased .This is logical, as septal LVH is more often reflect hemodynamic stress .
Diabetes infested myocardium bright echoes arise from within . This is due to reflection from interstitial proteins.
The newer modalities of echocardiography like integrated back scattering analysis can characterise tissues.
Tissue doppler myocardial spectral analysis can identify LVH contributed by DM..
Final message.
What we know about LVH , is far less than we do not know ! , especially when a patient has a combination of DM and HT. The interaction between them is so intimate , we fail to recognise individual contribution to the process. If only we decode this mystery , we can intervene better in the pathological progress of LVH.
Dr.S.Venkatesan MD 