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Dealing with Evidence!

You have probably heard about EBM (Evidence Based Medicine), and those of you who are not doctors probably presume that a lot of what we do is based on Evidence.....

NOT SURE! There is a lot more of the other EBM - Eminence Based Medicine, that gets used.

How do we as cardiothoracic surgeons deal with evidence?

Lets take a simple example - use of multiple arterial grafts in Coronary Artery Bypass Graft (CABG) surgery. Bypass surgery started off as a method of providing an additional channel of blood from the aorta to the blocked coronary artery - obviously beyond the blockage in the artery. Interestingly, an early pioneer in the use of arterial bypasses using the Left Internal Mammary Artery (LIMA), Dr Kolessov showed success of this approach in the old Soviet Union - Leningrad (now St Petersburg), in the late 1960s. His work did not get much airplay or credence because it was from behind the Iron Curtain. The Cleveland Clinic promoted the use of Saphenous Vein Grafts around the same time and very soon CABG became a frequently performed operation. To be fair to them, the Clinic also promoted the use of the LIMA through a landmark paper by Proudfoot, et al in 1986. Dr Brian Buxton, who had returned to Melbourne from Texas, postulated in the mid-1980s that if one IMA improved outcomes and survival, then two IMAs must be better!

I was fortunate that I trained with Brian Buxton, a pioneer in the use of the RIMA (Right Internal Mammary Artery) and the RA (Radial Artery), in addition to the LIMA (Left Internal Mammary Artery). As a consequence, Melbourne, Australia has one of the highest rate of multiple arterial grafts in the world. There are many papers documenting improved short, medium and long-term survival with the use of multiple arterial grafts. This extends to all ages and sexes. What is the rate in the US? This is an opinion piece highlighting this

https://www.tctmd.com/news/multiarterial-approach-cabg-still-entails-higher-risk-might-unlock-door-better-long-term

12%!

Yes that is right! Twelve percent (2004-15)!

This year, this study was presented at our annual meeting with a simultaneous publication in the New England Journal of Medicine.

https://www.tctmd.com/news/more-data-show-benefits-multiple-arterial-over-saphenous-vein-grafting-cabg-meta-analysis

It did not seem to make much of a difference in practice in the centers where I work. This is despite one of us (me) showing my colleagues that Multiple arterial Grafts were safe with good outcomes.

Why? Its complicated....

Since surgery is a craft with a considerable foundation in the skill & comfort level of the operator, this tends to color the way individual surgeons view evidence.

The other common refrain "I trained this way and it has worked for me".

Another contributing reason - "those operations take longer". This maybe true if one or the team is starting off; or doing this occasionally. That then becomes a convenient reason not to use it.

Other reasons given - higher risk of sternal wound infections, greater risk of bleeding, more complications in the peri-operative period, etc, etc. All of these have been addressed by many groups who have embraced multiple arterial grafts.

This reluctance is often in the face of cardiologists requesting at least a 2nd arterial graft instead of a vein graft.

My friend, Alistair Royse, an excellent surgeon from Melbourne, with a great expertise in echo and ultrasound has conducted a lot of follow up studies on patients undergoing multiple arterial grafts in Australia. The results at 15 years, are compelling enough that he has proposed a provocative concept - that the use of any venous graft might impact negatively on long-term outcomes.

Sorry to be so carried away by all this. This is a good example of how Evidence can be used selectively, with multiple reasons being offered.

It is important therefore for the consumers - patients, physicians, cardiologists ask why a 2nd arterial graft is not being used.


Indeed, as I update this blog in late 2020, more studies including a research letter by our collaborator Mario Gaudino from Cornell show that MAG (multiple arterial grafting) despite being better in terms of patient outcomes are grossly under-utilized in North America.


We have recently had two publications - one in JAMA and another coming out in Circulation that clearly shows that the Radial Artery is significantly better than Saphenous Vein at 10 years in terms of patency and clinical outcomes.


These messages need to be widely propagated to change practice. Eventually, it is up to cardiologists and patients to maybe force the necessary alterations in surgical behavior.

Patient engagement is vital - in making sure that Evidence is used effectively in the treatment of our patients.

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Jaishankar Raman, MBBS MMed, FRACS, PhD

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