Monday, 24 December 2012

How to link 5 stories to 1 Narrative or Why Cardiac Surgeons are not doing the right operation.

Reports of the death of the Coronary Artery Bypass Grafting Operation (CABG) are plentiful and exaggerated.
Despite the obvious advances in the technology of percutaneous coronary intervention over the past 30 years, surgical coronary artery bypass remains superior to PCI in patients with complex coronary artery disease and in patients with diabetes. 
What is surprising about the CABG operation is the fact that it has changed very little in 40 years. This is unlike the percutaneous procedure which today is completely different from the one originally performed by Andreas Gruntzig in the 1980s. The principle of the percutaneous procedure remains the same i.e to treat the stenosis or the diseased part of the coronary artery. The instruments and gadgets used to do this however have changed dramatically. 
In the CABG operation, the diseased part of the artery is avoided and a new conduit or pipe is used to divert the blood from a healthy part of the arterial system behind the narrowing, past the diseased narrowed part to another healthy part of the artery in front of the narrowing.  The choice of conduits or pipes that we use and the way they are plumbed into the arterial system has not changed since the first operations were performed in the 1960s by Favoloro at the Cleveland Clinic in the USA. 
The standard CABG operation to treat multi vessel coronary disease is the triple bypass operation to treat narrowings in all the 3 main coronary artery branches in the heart. The conduits used are pieces of saphenous or leg vein to bypass 2 of the narrowings and an artery that runs behind the left side of the breast bone to bypass the narrowing in the most important of the coronary branches - the LAD or Left Anterior Descending. This arterial conduit is known as the Internal Thoracic Artery (ITA). Use of this artery rather than vein to bypass the LAD is known to confer a survival advantage when compared to the use of a leg vein. Use of the left Internal thoracic artery is accepted as standard practice and failure to use it would be classed as negligent. 
Many research studies also suggest that use of both the internal thoracic arteries (we have 2, a right and a left) would confer an even bigger survival advantage. Yet whilst one internal thoracic artery is used in  >95% of CABG operations, 2 ITAs are only used in 10% of CABG operations in Europe and only 4% of CABG operations in the USA. In the UK, as with many things in life, the figure lies somewhere in between. In a recent leader in Circulation, John Puskas tries to explain the anomaly of low bilateral ITA use.
No-one in the cardiac surgical community, not even the greatest of advocates of bilateral ITA use, would argue against the fact that there are drawbacks associated with this procedure.
The procedure takes longer and is technically more demanding. These drawbacks however are relative and diminish with good training. 
One of the normal functions of these arteries (when they are not being used to bypass narrowed coronary arteries ) is to supply blood to the sternum or breast bone. The CABG operation requires the splitting of this bone. At the end of the procedure the bone is wired back together.  The bone healing that needs to takes place, requires a good blood supply - poor blood supply after harvesting of both ITAs equals poor healing and wound infection - (a good blood supply is required to fight the bugs that threaten to infect wounds). There is ample evidence of an increased wound infection risk with the harvesting of bilateral ITAs. Although the absolute risk difference is probably less than 1%, it is perceived by many surgeons to be much greater.
In the article in Circulation, Puskas points out two additional factors which conspire to restrict the use of these superior conduits. These factors are unique to healthcare systems of the USA and to a lesser extent in the UK. The first is public reporting of outcomes by individual surgeons. This is the norm in many states in the US and as the medical director of the NHS in the UK (a cardiac surgeon) has recently announced, will be mandatory for many surgical specialties in the UK.
The second factor that is unique to the US (but will undoubtedly cross the Atlantic) is the fact reimbursement for the treatment wound infections has now stopped. This is not such a bad idea - after all, the use of a carrot and stick approach led to the virtual eradication of antibiotic associated, hospital acquired infections such as MRSA and Clostridium Difficile diarrhoea and bed sores. Despite this, avoidance of operations with higher wound infection rates is becoming the norm.
Despite all these drawbacks, use of 2 internal thoracic arteries in the CABG operation IS associated with  improved outcomes. A patient is therefore faced with a choice, either a small increase in the incidence of sternal wound infection on the one hand or an increase risk of premature death/myocardial infarct/coronary re-intervention, on the other.
The fact both ITAs is rarely used suggests to me that patients are not being involved in the decision as to which conduits to use in their CABG operation. A recent article in the BMJ highlights this problem generally i.e the assumption of patient preference for a certain treatment. Doctors cannot recommend the right treatment without understanding how the patient values the trade-offs. This phenomenon is known as Silent Misdiagnosis. Discussion of the pros and cons of all available treatments with the patient should be an integral part of Shared Care decision Making .
Increasing the use of a surgical technique is rather more difficult than increasing the use of a drug - careful training by a decreasing number of trainers is required. Patients, Commissioners and Professional Specialist Surgical Societies should all have a role to play to ensure what is a good operation does not disappear altogether.