Posts Tagged ‘cass study’

Coronary  atherosclerosis is the number one killer of mankind. Many would consider it as an  essential  process of aging .Modern  life styles and habits make this appear  very early in life . There is currently an endemic (or even  a pandemic ) of   CAD due to premature  atherosclerosis. We need to recognise CAD is not a  primary heart disease  .It is an irony, heart is an  innocent bystander  to the  biological derangement  of coronary  vascular system  when  it is infested with atherosclerotic plaques .

So , when we  are confronted  with  serious atherosclerotic lesions in a coronary artery   what shall we do ?

We have three options

  1. Take on the enemy in a direct confrontation (Like war on terror ) : This is  some times called as Interventional cardiology .Caution is required as the battle  is within the human coronary artery ,  cross fires and collateral  damage  are unavoidable.

2 .Next  method  is to  find the basic cause  of  terrorism , identify  the perpetuates, facilitators    and try to correct the   root cause of it (CAD ) .This approach  also refered to as medical management  in cardiology community*  . It  aims  at regression of plaque  by statins, and life style modification and preventive cardiology. This modality is most ridiculed and  insulted by the main stream cardiologists.

*Comparable to  bilateral peace talks for a political solution to terror

3. And third option is a  real  surprise !   This  neither  confronts   the lesion   nor does it  address the initiating factors . It   just ignores  the lesion and by pass it with a LIMA /SVG  fly over ,  as if  nothing has happened in this vital high way leaving the culprit scot-free  .This option is  executed by surgeons as  CABG surgery . . . and  for mysterious reasons  this is a  well accepted one .

CABG :Here the atherosclerotic  burden is untouched by surgery . The graft can get diseased  sooner or later , native vessel disease  shall  progress some times encroaching  the ostia of distal graft site . Incidence of acute coronary syndrome following CABG is not greatly reduced for the simple reason we are not doing anything primarily to the inflamed plaques .These issues  are left ,  to be  taken care by the  medical  management .

* This article  does not want to defame these great development in cardiology(PCI/CABG) . They have a  specific role to play. CABG AND PCI remain the only option for critical  lesions with limiting angina .But please remember without  proper  medical management  ( ie Targeting  the perpetuates of  crime )  both  PCI and CABG will be a big sham !

Final  message

Avoiding   the  lesion  or  attacking the lesion  is a  primitive  method to tackle CAD  . Passifying   the lesions  in a slow and gentle manner,   preventing  further progression  or regression  of lesions is the only  “sane” method for combating CAD   . PCI and by pass surgeries  can be termed  as  21st century’s   medical  adventure sports  which  has  limited role ,  in the overall control  of CAD  for the human kind .

And  now  answer this question . . .

Cardiologists attack the lesion and  surgeon avoids the lesion ?  Who is the winner in our fight against CAD  ?

Both of them are  clear losers .The winners are  all those  humble physicians and parmedical workers (or even the responsible lay public ) who  help recognise  the early forms  of  CAD  and  counsel properly to prevent it .

This is  what  Dean Ornish   in 1991  documented in  Lancet  which was never considered scientific   for the simple reason it has no commercial value !




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Cleveland clinic is a leading centre for cardiac care .Major technological breakthrough occurs from this institute than any other place. Thousands of articles come out every year. Some articles , get global attention and make  a huge impact. These are usually related to a new hi- tech modality like CRT devices or percutaneous aortic valve deployment etc ,etc.

                                                Some articles , which are very important  may not get the due  attention . Journal editorial boards often  have a scorecard called impact factor .That is ,   how  a  journal  is  impacting the practice habits of  medical professionals . Ideally we need to have to grade individual   articles with impact factor .Many articles may not have any significant  impact  however good the impact factor of the journal.

Here is an article,  which excellently depicts the principles of management of ACS.  It was published in 2003 JACC,  by Steven Nissen  from Cleveland,  Ohio .It deserves more attention . Every cardiologist , involved in ACS management should read this, especially the interventionist.

Link to article placed her with courtesey of JACC

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MASS 2  study , the 10 year follow-up results are just out in circulation   september 2010 .

It is a rare study , where “one  to one vs  one” was compared  ie  the effect of  medical,  CABG , and  PCI    in chronic CAD .This was done in a single centre in Brazil,  between 1995 -2000 . It was  followed  up till 2010. Interestingly ,  such a study  may not be possible in the future ,   as  many of us  have  prematurely  glorified  the PCI and CABG over medical therapy . Recruiting  patients   for medical therapy alone is becoming a  difficult  job even in  developing countries.  Even if we recruit , huge cross over is likely  to PCI, CABG for all fancy reasons.

So , in MASS 2 we have a rare treasure on hand . . . Let us give three cheers to those  Brazilians  who did this study ,  and  shall carefully analyse and  interpret the results.

Highlights ( According to my  interpretation)

  • A total of about  600 patients with 200 in each group.
  • The overall death at 10 years  is not greatly different . (Around 25 % )
  • But ,cardiac deaths were distinctly higher by few percentages in pure medical  arm
  • Need for crossover  from medical to surgery and PCI to surgery was significant.

CABG tended  to prevent future MI in this study . This  could be  most significant observation from  this study ,( A revelation in fact ! ).It is against the popular  belief  created by CASS  legacy.

What are  the observed difference  between MASS 2 –  5 year results , which was published in 2004 ,  and  the 10 year follow-up , as  on  2010 ?

At the end of 5 years in 2004 , the differences  among the three groups were not obvious.The benefits of CABG mainly appeared after the 5th year and at 10 years it was significant.

Shortcoming of MASS 2

  • It is a single centre study .Numbers were less (600) .
  • It need to be emphasised    CABG was done  with  pump in all patients  . So the currently prevalent off  pump CABG  may not be really  comparable with reference to outcome.
  • Only   bare metal stents were used in PCI .(If only DES was used  . . . Considering the host of issues for and against DES , it will  be a  wild guess to judge it’s implication .  It could  have  tilted , either in favor or against  the  PCI  limb .)
  • In medical  limb ,  statins were not used in all.  Further , the dose of statins were not aggressive.This makes medical therapy appear less effective.

Intriguing  thoughts

When we say medical   therapy is  being  compared with PCI and surgery , we are actually comparing ,

Medical therapy  alone

Medical  therapy+ PCI

Medical  therapy + CABG .

Every patient  in all three  groups  receive  statin , antiplatelet and beta blocking drugs and so on.  Even though  statistics  would  vouch for  additional  benefit ,  over and above medical therapy  , in a given CABG  individual ,  how much  of the  the  accrued benefit  is contributed by co- administering   medical therapy  .It  is beyond   reasoning even  with all  gimmicks of statistics.

To exactly quantify  the individual benefits and efficiency  of  PCI ,  CABG  and medical therapy  two more  study limbs are necessary .

  • PCI without drugs.
  • CABG without drugs.

Such a study is possible only in a virtual world ! .  Decision  making  in favor of CABG ,  especially   in chronic stable angina ,  will continue , to be  difficult in the absence of refractory angina .This is due to  the modest benefit of CABG ,   that is  expected,  at an additional risk , cost and  expertise.

Please remember, a person can survive  , only  with medical  therapy for > 10 years  but no one can ever live with PCI or CABG  for that period of time without  adjunct drugs  . Guess  which modality   is  going to win the race  against CAD  in the long run  ?

Final message

If  any one  asks  for  conclusion of MASS 2  study ,  don’t ever say  “CABG is superior to  medical therapy” . Please emphasize , “CABG + medical therapy could   be , marginally superior to medical  therapy alone in some of the patients with chronic stable angina. (Each word  in the above statement is  important !) .

So . . . MASS 2 : Is it a  shot in the arm or shot  in the head for CABG ,  we do not know !


http://circ.ahajournals.org/cgi/content/full/122/10/949 .This study was done by Zerbini foundation Brazil

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Can we advice CABG for single vessel disease  ?

Yes, CABG  may be indicated  in

  • Critical , proximal , complex  LAD disease   with or without  ostium involvement.
  • Many of the bifurcation lesions with large and significant  side branch
  • Small caliber LAD with diffuse disease .

When these occur  in diabetic  subjects , the  indication for CABG is more certain .

* Present generation cardiologists  would feel  every  lesion  is  stentable and should not be referred to the surgeon .But it should be emphasized here,   technical feasibility alone  ,  does not  imply  PCI is superior and ideal in all coronary interventions.

Can we do a CABG  in  single vessel disease  with  normal  LAD ?

CABG is  very rarely  indicated   for isolated RCA or LCX disease. It should be consciously avoided in this patient population.

This is because the at risk myocardium  supplied by these vessels are far less than that of LAD. PCI  is  preferred    in these vessels .(Ofcourse , after considering medical management  ) .

CABG is  ,  too traumatic a  surgery , to  offer  in this  low  risk  coronary  lesions.


CABG  can still be done in following situations  for non LAD single vessel disease.

  • Left dominant circulation  with  complex lesions in LCX /OMs.
  • It is common to see diffuse , long segment  and severe disease of RCA with normal LAD /LCX system .PCI is not feasible in this subset.
  • Failed PCI
  • Recurrent instent restenosis.
  • Bail out CABG after a acute complication during PCI

One should remember ,  inability to do a PCI  does not  mean ,  the patient  should   land in surgeon’s table .We should recall , from our memory medical management is an effective and established form of treatment in single vessel disease ( Mainly for non LAD , and some cases of LAD also !)

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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 .


A surgeon testing LIMA flow before Anastomosing it to LAD.

Image courtesy Dr.Mannoj Aggny .You tube

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                                Coronary artery  by pass graft surgery has become the most common cardiac surgery done world over ever since it was first introduced by Favalaro in 1969.The common indications  are, triple vessel disease and left main disease in any of the following situationsE.

Elective CABG(Non emergent)

1.Chronic stable angina

Either emergent or elective

1.Unstable angina

Emergency CABG*

1.Acute myocardial infarction.-Cardiogenic shock

2.Failed thrombolysis

3.Failed primary PCI

4.Complications during routine PCI(Cath lab crashes !  etc)

5.As an associate procedure after a  mechanical complication during MI (Septal rupture, Acute MR etc)

*In emergency situations even a single vessel disease would require a  CABG

Hybrid CABG

Combining CABG and PCI in the same patient is followed in very few centres .(Example LAD graft and RCA angioplasty)This is done in patients who have co morbid conditions who can not tolerate prolonged surgical times.Further there can be situations  one lesion is very ideal for PCI  while for other grafting is the only solution.

Controversial CABG

1.CABG as a primary revascularisation  in STEMI*

(Rarely done now , almost obsolete , primary PCI has almost replaced it  . . . but it is still  useful if performed within 6 hours of MI )

2.Incidentally detected CAD*  following routine coronary angiogram.

( *CABG for incidentally detected asymptomatic CAD is  increasing in many parts of world )

Inappropriate CABG

         If it’s triple vessel disese it must be CABG -CASS study (1980s)

                       Coronary artery surgery study (CASS) still has considerable influence among the  cardiology  community in the decision making process  for CABG , even though it is many decades old .There has been a phenomenal development in both medical as well as interventional techniques since  CASS . (Thrombolysis, Statins, ACEI, PCI  DES to name a few) .

                     When CASS study was done many decades ago,it was believed triple vessel disese constitute a  homogeneous population and  carry  the same clinical significance . For example a 90% proximal LAD , 50% RCA and 50% OM technically qualify for a CABG and unfortunately , some of them are  subjected to it even in  2008 !  Now we clearly know, it is not the number of diseased vessels  that is important, but it’s location, severity , LV function, presence or absence of diabetes . Finally , the presence of revascularisation eligible myocardium must be documented in all post MI patients . (Technically referred to viable & ischemic myocardium ).              

              Currently , with the  PCI  & medical management has grown so much, CABG should be reserved only for, critical triple vessel disese , with at least one proximally located lesion (Mostly  LAD  or Left main ), especially in diabetic individuals.

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