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Some thoughts about left main disease : Why CABG will always prevail over PCI in left main disease ?

Posted in cardiac surgery, Cardiology - Clinical, Cardiology -Interventional -PCI, cardiology -Therapeutics, Uncategorized, tagged , , , , , , , , , , , , , , on March 6, 2009| Leave a Comment »

Why PCI  in   left main CAD is considered  an inferior modality than CABG ?

CABG is superior to PCI for the  simple reason it provides complete revascularisation virtually in all  patients with LMCAD , while PCI is possible only in a fraction of patients with LMCAD.

If  we take 100 patients  with left main  disease may be ten (At best !)   would be  suitable for PCI ! In other words PCI is contraindicated in vast majority of LMCAD  by technical criteria alone , while there can never be a contraindication for CABG in patients with LMCAD.(Except  when , comorbidity precludes surgery )

Why  PCI in  LMCAD difficult ?

It is  dependent on  technicalities

CABG does not tackle a lesion,  it simply avoids it  and by passes it ” No great brains required”

while PCI takes on the plaque frontally ,  in the dangerous  terrain of  left main artery  itself !

so,  much caution,  planing ,  logistics are required . Further ,  if there is a complication there is a potential

for catastrophe  as the only  supply line is cut off . This is the reason , cardiologists were worried to try this on

unprotected left main. (Protected LMCAD refers to left main disease following CABG  wherein atleast   LAD or LCX is  grafted )

Points to ponder in LMCAD

  • PCI is suited for isolated discrete LM disease.In realty  this is seen in less  than 5-8 % CAD.
  • LMCAD is very often associated  with  critical and multivessel distal CAD . So these patients will be candidates for CABG.
  • Left main ostium or LAD ostial  involvement makes PCI a tougher exercise
  • Calcification is more common in LMCAD that  again makes PCI difficult.

The following article in Feb 2009 is a major blow for proponents of  PCI for left main

http://circ.ahajournals.org/cgi/content/extract/119/7/1013

left-main

http://content.onlinejacc.org/cgi/content/abstract/51/5/538?ijkey=84c977d189e84327c3abbd4c1228de17dd99048a&keytype2=tf_ipsecsha

Final message

  • Conquering left main disease is an interventionist’s  ultimate dream.
  • But, before that they have  to tackle the bifurcation lesions .This is of vital importance, because 2/3 rd of left main  patients have  some form of bifurcation lesions. Current techniques , hardware  and outcomes are far below the idealistic solutions in bifurcation lesions.
  • Till that time ,  CABG would  remain the only choice for all , but for  a small fraction of isolated  left main disease where PCI may be possible.

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Why is LIMA graft superior to saphenous venous graft in CABG ?

Posted in cardiac surgery, Infrequently asked questions in cardiology (iFAQs), tagged , , , , , , , , , , , , , , , , , , , , , , , on November 6, 2008| Leave a Comment »

          During CABG arterial grafts are always preferred over venous grafts , for the simple reason the grafted vessel has to carry arterial blood and not the venous blood. Saphenous veins are tuned to carry venous blood at low pressure.The mean coronary arterial pressure is around 40mmhg and this will damage the saphenous venous endothelium more quickly. The reocculsion rate at 10 years for venous grafts  can reach  60%.


                                                    Left internal mammary artery (LIMA) is the most commonly used arterial graft. This is usually anastamosed with LAD. The lumen of LAD &  LIMA are more or less equal and they match well in character also !

The other advantage  of  LIMA graft  is ,   blood    tends to  flow  both during systole and diastole in a smooth fashion.. Since the venous graft which  hangs from the root of aorta , the  ostium  of venous graft lacks the  hemodynamic benefits of   coronary sinus . (We know the coroanry sinus acts like a  reservoir for  the smooth release of  blood flow into coronary arteries.)

Finally ,  the most important feature of LIMA is

  It is a live graft

LIMA’s proximal origin from subclavian is left intact, so LIMA acts as a live vessel with it’s  vasa vasorum intact ,  which means the endothlium derived relaxing factor (EDRF-Nitric oxide) secretion is not interrupted.This makes the LIMA  an excellent graft , self protected against reocclusion.One may call it a drug eluting graft !

 What is the patency rate for LIMA ?

LIMA patency rates at 10 years is nearly 90 %  .But the graft patency depends on many factors , like diabetes, age, gender, surgical technique ,(Now , beating heart CABG is very popular , where the LIMA patency is said to be slightly lower than conventional CABG) Sequential LIMA grafts, free LIMA graft ( Which  loses the advantage of being  a live graft) have relatively lower patency rates.

What are the other arteries used in CABG ?

Other arteries that could be used are radial artery, right internal mammary artery, and gastro epiploic artery.The patency rates of all these arteries far less than LIMA .

cabg-2

A surgeon testing LIMA flow before Anastomosing it to LAD.

Image courtesy Dr.Mannoj Aggny .You tube

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