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Posts Tagged ‘beating heart surgery’

The NEJM’s breaks the  hidden truths about cardiopulmonary bypass in a beating  heart. The irony in medical science is   ,  trend setting  land mark articles usually arrive  very late . . .   to disappoint  all those  patients who  got the wrong treatment ! Off pump by pass is definitely one among them . . .

The major reason for off pump CABG’s s poor showing is

  • The surgeon’s  conflict   in defining   what is successful CABG  .The success of CABG   is   in    relief of symptoms & providing good bypass graft  with long term patency   .It is not in  less  thoracic trauma or in  a quick hospital discharge  !
  • The second major reason is denial of  the fact  that off pump CABG is indeed inferior  and hence no course correction was attempted  ! ( And  now that it   has become a hard  evidence   we expect some changes  . It  required almost 10 years for our cardiology community to  recognise this .)
  • Lesion access and  difficulty in mobilizing LIMA .Many times the the point of anastomoses is preselected by the accessibility and technical issues rather than lesion guided approach .This often happens than we imagine , and this could be a very bad advertisement for off  pump CABG

cabg on pump vs off pump beatin heart

Click on the link to NEJM abstract  ROOBY study

http://content.nejm.org/cgi/content/short/361/19/1827

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          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

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