Arterial Grafting Seen as Better for Moderate Coronary Blockages

HOUSTON -- Grafting moderate stenoses during bypass of other more extensively blocked coronary arteries was associated with less ischemia, particularly when using an arterial graft, a single-center observational study suggested.

Progression of a 50%- to 69%-stenosed native vessel to become a severe blockage or complete occlusion was faster in grafted vessels, and more so for those treated with saphenous vein grafts, Joseph Sabik, MD, now of University Hospitals Cleveland Medical Center, reported here at the Society of Thoracic Surgeons meeting.

Progression by 10 years occurred in 66% of non-grafted vessels, compared with 84% treated with an internal thoracic artery (ITA) graft and 90% with saphenous vein grafts in the study, selected as the top paper in adult cardiac surgery at the meeting and slated to be published in the Annals of Thoracic Surgery.

But patency of the ITA grafts was 92% at 1 year and 89% at 10 years, slightly lower than expected, "due to the effect of native vessel competitive flow on internal thoracic artery patency," but still better than the 87% patency at 1 year and 54% at 10 years with saphenous vein grafts, Sabik told the audience.

Thus for moderately-stenosed lesions, 47% would have had protection from myocardial ischemia at 5 years if treated with an internal thoracic artery graft versus no grafting, as calculated by multiplying the percentage of nongrafted, moderately-stenosed coronary arteries that progressed in that time by the graft patency at that time. By comparison, that proportion was 36% with saphenous vein grafts.

"Consideration should be given to grafting moderately-stenosed coronary arteries with an internal thoracic artery during coronary surgery," Sabik concluded at the presentation of his study (done while at the Cleveland Clinic).

Among 55,567 patients undergoing primary isolated coronary artery bypass grafting (CABG) for two- or three-vessel disease at the Cleveland Clinic from 1972 through 2011, the study looked at the 1,902 who had a single vessel that fell into the 50% to 69% stenosis range. For these moderate blockages, 74% were grafted, of which 27% were internal thoracic artery grafts and the rest were saphenous vein grafts.

However, study discussant T. Bruce Ferguson, MD, of East Carolina University in Greenville, N.C., argued a different conclusion for the "provocative" findings.

"No support is provided for saphenous vein grafting of moderate stenoses. At face value, the early-phase ITA grafting results -- 23% relative increase in disease progression, 8% 1-year ITA angiographic occlusion -- suggests that all moderate stenoses should be left ungrafted," he said. "Only the inference of late-phase functional ischemia provides the rationale for ITA grafting of these lesions."

He pointed to prior findings from Sabik's group that treating moderate stenoses had no impact on long-term survival.

The pragmatic conclusion might be that anatomic criteria are inadequate for treatment decisions on moderate stenosis, Ferguson suggested. What's missing is objective physiologic evidence on which to base it, he added, referring to the FAME trial showing the combination of functional ischemia and anatomic imaging did predict outcomes.

Ferguson predicted that "soon CABG will be sandwiched by functional and anatomic angiography."

John Puskas, MD, of Mount Sinai Hospital in New York City, also cautioned about selection bias on the part of the operating surgeon. Speaking from the audience, he suggested that surgeons' ability to select dangerous moderate lesions to graft -- perhaps based on length or more complex appearance -- might have confounded the results.

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