While many of us are preoccupied with wires and balloons ,( coronary myopia ! ) , our radiology colleagues are making rapid strides . Let us spend some time to understand how the myocardial segments are inflicted the final insult . We need to realize , there is a pattern to this myocardial end game of scarring and fibrosis.
MRI is the gold standard to assess the myocardial architecture . It has a role in both assessing the anatomy , function , perfusion and viability .
- LV function is assessed by cine MRI
- Viability stud by delayed enhancement MRI (DEMRI , also called as LGE- Late Gadolinum enhancement )
- Myocardial scar best assessed by DEMRI*
* Why do you require DEMRI to identify scar ?
One can detect scars in plain MRI but contrasts make it better .Hence delayed enhancement in by DEMRI is used to detect scars.
Is it ischemic DCM or Non ischemic DCM ? ( That is the question we commonly ask
We rely too much on CAG anatomy for this. It can be misleading. Cine MRI with DEMRI gives the answer straightway with high degree of accuracy . CAG is required in all , but if it is normal , or has insignificant lesions , the dilemma of ischemic DCM would continue !)
**Note ,there is one simple algorithm proposed by the author to differentiate Ischemic DCM from Idiopathic DCM without MRI – Click here to Link
Following scar patterns in DEMRI help us to arrive a diagnosis.
Favors Non ischemic DCM
- Mid myocardial scar
- Epicardial scars
- Global sub-endocardial scars
- No scar(Ironically if no delayed hyper-enhancement is noted it is likely to be non Ischemic DCM )
Favors ischemic DCM
- Regional transmural scars
- Localised sub-endocardial scars
* Ischemic DCM will always involve subendocardium as ischemic wave front goes from sub-endo to epicardium.
examples for Non Ischemic DCM
- Amyloidosis (Can be restrictive as well )
- Chagas
- Fabrys
Why is scar localisation and Quantification important ?
Apart from differentiating various cardiomyopathies it has few clinical implication .
- Since scar indicates irreversible damage , if extensive it will argue against any re-vascularisation .
- Scar location becomes vital if we plan CRT .It will be futile to place a CRT lead over a scar.
- Scars are often form a macro re-entrant circuits for VT .Help us localize or zeroing in VT focus.
- Scar quantification is helpful risk stratification of patients with HOCM .and their family.
Final message
Myocardial scar location and quantification is the new mantra in a patient with dilated heart with cardiac failure.
It may be more important than even a coronary angiogram .MRI will prevail over any of the available echocardiogram modalities to assess the scar pattern.
Reference
Dr.S.Venkatesan MD 