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MASS 2 , 10 year follow up study : A shot in the arm for CABG ?

Posted Oct 28 2010 10:15am

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/abstract/122/10/949

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


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