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Posts Tagged ‘eliis classification’

Reporting a coronary  angiogram  may look like child’s play  for most cardiologists. Many do it in less than a minute. (It goes something like this  90 % LAD , 30 % ostial OM1, 50 % mid RCA etc etc ) The famous and meticulous  classification of Ellis and Ambrose proposed  two  decades ago appear largely redundant.

In this review we shall  briefly  debate an eccentric plaque or lesion .

Pathological definition

Pathologically  an eccentric lesion  will have a disease free arc  within an  atherosclerotic lesion.If we apply this criteria most of the plaques appear to be eccentric.

Angiographic definition

In simple terms  eccentricity is  said to be present when the plaque  volume is three times more on one side when compared  to opposite side .

The incidence of eccentric lesion is largely under estimated.  It can be up to 40 % of all lesions.

It has histological  as well as  hemodynamic  significance.

How to measure eccentricity index ?

Ratio between maximum plaque thickness and minimum plaque thickness (Including the media )

Image courtesy modified from Circulation. 1996;93:924-931

In the above figure : The eccentricity index is measured  as the ratio of the maximum  to minimum plaque plus media thicknesses. In the eccentric lesion  the maximum wall thickness measures 2.6 mm, minimum wall thickness measures 0.2 mm, and eccentricity index is calculated to be 5.2.  In the  concentric lesion  the maximum wall thickness measures 2.2 mm, minimum wall thickness measures 1.6 mm, and eccentricity index is calculated to be 1.4.

What are the associations of eccentric plaque ?

Calcification and hard plaques are more common in eccentrically placed plaques.The  most vulnerable point for plaque  rupture or disruption is  the shoulder region between normal and plaque segment.

A long eccentric lesion with over hanging plaque

 

Clinical implications

  • Acute recoil
  • Coronary spasm
  • Mechanical effects : Asymmetric expansion of stent
  • Drug eluting stents

An arc of normal plaque circumference predispose to acute recoil and spasm.this is logical as the normal  arc will have a fully functional  medial smooth muscle  which are prone for spasm.

Does stenting reverse  the eccentricity of plaque ?

It may not .  The drag effect of major plaque mass may either result in plaque prolapse or  asymmetric stent approximation  or even stent crushing effect.

How does the  the stents  elute in an eccentric lesion ?

Stents are not intelligent enough to  differentiate  the plaque surface and normal surface. We  also know these drugs are  toxic to  normal endothelium  and hence  are not welcome in the normal arcs of an eccentric lesion.

Since the drug secretion   is uniform throughout the circumference   it makes the   DES a perfect misfit in eccentric lesions  As  we  realise most of the lesions are pathologically eccentric one can guess the long term  consequences .

Final message

The more we think we know . . . the less  is understood .

The images we see daily in cath labs are too simplistic to make vital decisions .There are  constant innovations coming up but none seems succeed in  imparting  common sense to  majority  us.(Namely  direct plaque intervention can never succeed over a diffuse medical  disease called atherosclerosis  )

A good reference article

http://circ.ahajournals.org/cgi/content/full/93/5/924

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