Editorial Comment

Thou Shalt Not (Look Like You’reTrying to) Steal

Peter C. Block, MD

Emory University Hospital,Atlanta, Georgia

The potential for mammary side-branch steal from theleft anterior descending coronary artery after left internalmammary/left anterior descending coronary (LIMA/LAD) bypass grafting has generated a small but none-theless vociferous following. The literature surroundingthis issue has credible voices on both sides. For interven-tional cardiologists who see angiograms of LIMA/LADs(done because of recurrent angina postoperatively), acurious reversal of the inaptly named “oculo-stenotic”reflex frequently occurs. A large (usually proximal)branch of the LIMA that has escaped the surgeon’s clipsdue to its location is seen to be widely patent. It fre-quently is almost equal in diameter to the LIMA itself.Just because it is large, patent, and looks like it might bestealing, an intervention is performed. The vessel iscoiled and, hopefully (though not always), closed.

I would wager that many such interventions have beendone, and plead guilty to the offense myself. The questionremains, Does closure of the proximal offensive (if notoffending) branch make any difference in blood supply tothe LAD with stress? This is where the literature becomesleast credible. Many reports are anecdotal, and many simplystate that technically a closure can be performed. Patients’symptoms are variably improved, but that is no measure ofactual improvement of coronary blood flow. The basicpremise that occluding a side branch of a LIMA deliveringantegrade flow to a coronary artery has always puzzled mebecause it seems contrary to what we know about coronaryflow versus systemic artery flow. Because coronary flow ismainly diastolic flow, how is this influenced by occluding abranch that supplies thoracic muscles primarily in systole?It’s a mystery.

Perhaps the best review of this issue is an editorialcomment written by Mort Kern [1], who concluded thatLIMA/LAD steal is inconsequential and should be laid torest. However, he also suggested that if occlusion of theside branch is contemplated, demonstration of improve-ment of LIMA/LAD blood flow using intracoronaryDoppler velocity after trial balloon occlusion of the sidebranch would help allay the risk/benefit issues of theintervention. His advice apparently has been heeded. Inthis issue, Morocutti et al. have reported such a demon-stration. In their patient, Doppler flows at rest and withadenosine, during hyperventilation at rest and with aden-osine, and finally at rest and with adenosine and hyper-ventilation after trial balloon occlusion of the side branchof the LIMA were different. Coil occlusion was per-formed, and we are told angina has improved. Am Iconvinced? Perhaps, but not completely. Two issuesmust be raised. First, we do not have Doppler flow duringtrial balloon occlusion and hyperventilation withoutadenosine. Did occlusion alone make any difference?Second, we are not told about antegrade blood flow to thedistal LAD through the native vessel. Was the nativeLAD occluded proximal to the LIMA/LAD anastamosis?If so, I would be reassured that the data shown are valid.If not, then the degree of native vessel LAD antegradeflow may have significantly impacted the Doppler flowsthat were measured.

Does the report by Morocutti et al. help with thisdebate? I think it does. It shows that Doppler flows canbe measured successfully before and after trial side-branch occlusion. It also emphasizes that we should besure we provide data to support the expectation of real(not just symptomatic) improvement before we take therisk of intervention. Doppler studies interpreted carefullyand done for each patient might be just the thing to keepus from taking unnecessary risks.

REFERENCES1. Kern MJ. Mammary side branch steal: is this a real or even

clinically important phenomenon? Ann Thorac Surg1998;66:1873–1875.

DOI 10.1002/ccd.10264Published online in Wiley InterScience (www.interscience.wiley.com).

Catheterization and Cardiovascular Interventions 56:377 (2002)

© 2002 Wiley-Liss, Inc.