Monday, 15 April 2013

Off Pump Coronary Surgery (OPCAB) and the Evolution of My Pragmatism!

I have been observing and then performing coronary artery surgery since 1988. It was in 1992 when I first heard of Subramanian's first published accounts of LIMA to LAD coronary bypass done off pump i.e. without the aid of a heart lung machine.

In 1995, when I was senior registrar (Chief resident) at the Queen Elizabeth Hospital in Birmingham, UK, Jim Fonger, an American cardiac surgeon, was invited by Bruce Keogh (who was still a plain old Mr. then and a Consultant cardiac surgeon at the QE) to come to Birmingham to operate on a Jehovah's Witness who required redo coronary surgery . Dr. Fonger performed an off pump gastroepiploic artery bypass to the right coronary off pump through a small upper abdominal incision - it was impressive stuff. The patient did very well and the case was reported in the local paper. A few months later another surgical team arrived from Italy and operated on 6 patients with isolated disease in the left anterior descending coronary artery. Two things seem quite extraordinary now - finding so many patients with single vessel coronary disease requiring surgical bypass and enabling foreign surgeons to operate on NHS premises - both are virtually impossible now! Anyway, back to Birmingham, these 6 patients did not do as well as was expected and most suffered one or other complication - I was not impressed and my skeptic attitude towards off pump CABG returned.  Moving on to 1998 and a publication from South America changed the scene. Buffolo et al described a very large series of patients undergoing multivessel coronary artery bypass surgery without the aid of a heart lung machine. This study was significant because until now only single vessel bypass had been performed in this way. Now here was a operation that was applicable for the majority of patients with coronary disease requiring surgical revascularisation. The operation was christened OPCAB - off pump coronary surgery. Industry became interested and the turbo boosters were lit! What followed was massive non-evidence based expansion in practice in the usual optimistic way which seems to be so characteristic of surgical procedures. I was swept up by the enthusiasm, went on courses, learned the technique and soon more than 50% of the cases I was operating on were done without the aid of a heart lung machine. Over the ensuing 8 years, paper after paper eschewing the benefits of OPCAB surgery were published. Most of these papers were large retrospective series. There were some small randomised trials that suggested that despite the findings of the retrospective case series, the differences between on pump and OPCAB were negligible . The justified criticism aimed at these studies were that they were small and trial subjects did not include the type of patients who were likely to benefit from OPCAB - the high risk patient. I stated as much in a leader in the European Heart Journal.
During the past three years, the findings of a number of randomised controlled studies have now been published - here, here, here and here. The truths surrounding the OPCAB vs on pump CABG debate are now emerging from the mists of uncertainty.
Patients require less transfusion after OPCAB
Patients are less likely to suffer postoperative atrial fibrillation after OPCAB
Early and probably late mortality rates are NO different after OPCAB in all (even higher risk) patients
Vein grafts are less likely to be patent after one year in patients undergoing OPCAB
As a consequence, patients are more likely to suffer angina recurrence and need coronary revascularisation at 1 year after OPCAB (still much lower than percutaneous coronary intervention).

There are 2 further truths that all surgeons would also accept - 1. manipulation of an ascending aorta that is known to be diseased is tantamount to criminal behaviour because of the known  high risk of cerebral emboli. 2. The only way to avoid touching the aorta during a coronary artery bypass procedure is to perform an OPCAB procedure using pedicled arterial grafts such as the internal mammary artery grafts with any further grafts attached proximally to these pedicles.  The alternative, if the disease in the aorta is not diagnosed until after the chest is opened, is a surgical bailout. In the presence of severe coronary disease, this option could be quite hazardous.
The age of the patients undergoing coronary surgery is increasing all the time. Operating on an octogenarian is now not as rare as it used to be. The chances of coming across a diseased ascending aorta is therefore higher than it has ever been.
Despite the lack of evidence for its superiority and the fact that OPCAB surgery is technically harder and certainly more stressful for the operating surgeon, it  represents a valuable addition to a coronary surgeon's armamentarium. As it is a technically harder operation, surgical competence must depend on the surgeon performing an adequate number of procedures.
These are pragmatic rules I have devised  therefore for choosing OPCAB when performing a coronary bypass operation:
all patients with any evidence of a diseased ascending aorta requiring surgical coronary revascularisation
When putting the patient on the heart lung machine is hazardous - e.g. heparin resistance,
If performing the same operation is quicker and easier if the heart lung machine (or Pump) is NOT used e.g. LIMA to LAD

These rules mean I can perform OPCAB often enough  to remain proficient in the technique and I am not caught out if required to perform coronary surgery without a pump in an emergency.
OPCAB remains the procedure of choice in many cardiothoracic centres including the majority in India where OPCAB is king. Evidence however suggests that this might not be the right thing to do.