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Posts Tagged ‘left main’

Human coronary artery branching pattern is unique in every  individual . Left circumflex shows many variations.

The important ones are  a separate origin , variation in the angle of bifurcation, the number of OMs  .Further, the length of  mainstem  LCX  and its course in the AV groove are quiet unpredictable.The diameter of LCX vs are generally equal  (or LAD >LCX).

The division of  left main is such that circumflex  generally gets a lesser share  of blood flow . If  LCX is dominant this  ratio  may be little balanced. But if the LCX  is huge LAD definitely suffers !When left circumflex equals the size of left main  the pattern is distinctly  unusual.

This patient   we encountered recently had 4mm sized LCX   and  presented with a tight LAD lesion .

This man's LCX probably will never sufffer from atherosclerosis !

Other observations about large bored LCX

  • Narrow ostiums are prone for  atherosclerosis .A large mouthed  LCX rarely involves  in left main  bifurcation lesions.
  • Disproportionate size of LCX when compared to LAD  can  have hemodynamic implication of provoking LAD disease  .

The implication of  differential  sharing of left main blood flow is not fully understood .It needs further insights.

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Left main divides into two. Some times into three . Very rarely into 4

Look  at this angiogram ,  This looks  like  a quadrification, if not quadrification equivalent

Clinical implication

A 4 way division invariably means the OM and diagonal or going to be diminutive.These people are expected to have favorable coronary hemodynamics during ACS , and  left main lesions are  less likely  to  occur

Reference

This article is from Singapore medical Journal

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NSTEMI  constitutes a  very heterogeneous population .The cardiac   risk   can vary  between very low to very high .  In contrast ,  STEMI patients  carry  a high risk for  electro mechanical complication including   sudden death .They all need immediate treatment  either with  thrombolysis or PCI to open up the blood vessel  and salvage the myocardium.

The above concept , may  be true in   many situations  ,  but what we fail to recognize   is  that ,   STEMI   also  is  a heterogeneous clinico pathological  with varying risks and outcome !

Let us see briefly ,  why this  is very important  in the management of STEMI

Management of STEMI  has undergone great  change  over the past 50 years and  it is the standing example of evidence based coronary care in the modern era ! The mortality  ,  in the early era was around 30-40% . The advent of coronary care units, defibrillators, reduced the mortality to around 10-15%  in 1960 /70s . Early use of heparin , aspirin   further improved the outcome .The inhospital mortality  was greatly  reduced to a level of  7-8% in the thrombolytic  era. And ,  then  came the interventional approach, namely primary PCI ,  which is now considered the best form of reperfusion when done early by an experienced team.

Inspite of this wealth of evidence   for the   superiority  of PCI  , it is only a fraction of  STEMI patients get  primary PCI   even in some  of the  well equipped centers ( Could be as low as  15 %)

Why ? this paradox

Primary PCI   has   struggled  to establish itself  as a global  therapeutic concept  for STEMI ,   even after   20 years of it’s introduction (PAMI trial)  .  If we  attribute ,  lack of   infrastructure  , expertise are  responsible for this low utility of primary PCI , we are mistaken ! There are so many institutions , at least in developing world ,   reluctant to do primary PCI  for varied reasons.( Affordability , support system , odd hours ,and finally perceived fear of untoward complication !)

Primary PCI may be a great treatment modality , but it comes with a inherent risk related to the procedure.

In fact the early hazard could exceed the potential benefit in many of the low risk STEMI  patients !

All STEMI’s are not  same , so all does not require same treatment !

Common sense and logic would   tell us any medical condition should be risk stratified before applying the management protocol. This will enable  us to avoid applying “high risk  – high benefit”  treatments in low risk patients . It is a great surprise,  the cardiology community has extensively researched to risk stratify NSTEMI/UA   ,  it has  rarely  considered risk stratification of STEMI before  starting the treatment.

In this context , it should  be emphasized  most of the clinical trails on   primary PCI  do not address  the clinical  relevance and the  differential outcomes   in various  subsets of  STEMI .

Consider the following two cases.

Two young men with STEMI  , both present within  3  hours   after  onset of symptoms

  1. ST elevation in V1 -V6 , 1 , AVL   ,  Low blood pressure , with severe  chest pain.
  2. ST elevation in 2 ,3, AVF , hemodynamically stable , with minimal  or no  discomfort .

In the above example,   a  small inferior  MI by a distal RCA occlusion  ,  and a proximal LAD lesion jeopardising entire anterior wall , both  are  categorized as STEMI !

Do you want to advocate same treatment  for both ?  or Will you  risk stratify the STEMI and treat individually ?  (As we do in NSTEMI !)

Current guidelines , would  suggest PCI for both situations. But , logistic ,  and real world experience would clearly favor thrombolysis for the second patient .

Does that mean,  the second patient is getting an inferior modality of treatment ?

Not at all . In fact there is a strong case for PCI being inferior in these patients as the risk of the procedure may far outweigh the benefit especially if it is done on a  random basis  by  not so well experienced cath lab team.

(Note : Streptokinase  or TPA does not  vary it’s action ,  whether given by  an ambulance drive or a staff nurse or even a  cardiologist !  .In contrast ,  the infrastructure and expertise have the  greatest impact on the success and failure  of PCI )

Final message

So , it is argued the world cardiology societies(ACC/ESC etc)  need to risk stratify STEMI (Like we do in NSTEMI ) into low risk, intermediate risk and high risk categories and advice primary PCI only for high risk patients.

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Coronary stents have revolutionised the management of CAD. Stents are metallic scaffolding devices that help keep the atherosclerotic plaque  plastered within the coronary arterial wall.Thus it gained the name angioplasty. Stents have aradial strength that  exerts a constant force on  the plaque . Since metals are unfriendly partners for coronary artery , we need to have minimum metal within the coronary artery.The stent struts weave around the lumen generally the stento/ artery area ratio should be as less as possible (15%).

But this has a trade off .The uncovered area of plaque tend to project into the lumen .This is many times not significant.But can be a problem if the plaque is very soft and bulk of the lipid core may reenter the lumen.this event is called plaque prolapse.

plaque-prolapse

What is the time taken for plaque to prolapse ?

Generally it is late event.But it can happen immediately after the procedure also.

Which type of lesions are more likely to have plaque prolapse ?

Eccentric and complex lesions especially with overhanging edges are prone for prolapse

What is the sequale ?

It can be benign.If there is a erosion due to stent struts can precipitate an ACS.It progresses into instent restnosis in many.

What is the angiographic appearnce ?

Angiographically it often appears as luminal  irregularity withi stented segment .

Many times , it may appear as a filling defect also.

Is there any specific issues in plaque prolapse in drug eluting stents ?

Coornary artery is not drugged uniformly by the drug eluting stents.In fact contact  lines of metalic struts  , through it’s micropore oozes the drug with polymer.Pathological studies have revelaed non homogenous drug penetration and resultant irregularity on the plaque surface.This could amplify the plaque penetration preferentially in few areas.

How to manage plaque prolapse ?

It should be managed as any other instent restenosis.Plaque resection with atherectomy devices has not solved the problem to the desired levels.A second stent is the most common approach advocated by the cardiologists.(Whic is not ideal though !)

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                                                          Left main coronary  lesions are  fairly common  during routine coronary angiogram.These may be a critical or a innocuous lesion.The  word “left main” triggers a sort of alarm reaction to many cath lab staff as well as the cardiologists and surgeon.Many times, these left main lesions are detected in patients   with chronic stable angina who have stable symptoms. Left main disese has not been graded  clearly in literature . Often it is perceived , any lesion in LM is serious.

There is an unwritten rule,  rather a medical compulsion  to take a patient  with left main disease  for emergency CABG ( Now some centres ,emergency PCI) .Some institutions make it  a rule these patients  are posted  in the  next available slot in the theatre.

 The basic question we raise here is   “Should we consider all  left main  disease  as  an  emergency”?

Not really , especially when it occurs in a stable angina .One can wait , buy some time to fully evaluate and prepare  the patient  and may be the patient can be posted  as an elective case. It is a well recognised fact that, CABG carries adverse outcome when done as an emergency procedure. This is primarily due to inadequate pre op work up and resultant complications. It is also well known ,  surgical  back up team may not be available in full strength in odd hours .

This post is  to convey the message , that left main is  a serious disease but that doesn’t  mean it should elicit  a panic reaction and be taken as an ultra emergency . There has been many morbid and fatal outcomes in many hospitals due to this apparent  pseudo emergency !

 

Note* 1.Left main  disease during acute coronary syndrome is to be seen in different perspective.2.Some of the proximal LAD lesions are so tight and  could be more significant than left main lesions.

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