Letter by Brilakis and Banerjee Regarding Article, “Impact of Internal Mammary Artery Conduit on Long-Term Outcomes After Percutaneous Intervention of Saphenous Vein Graft”
To the Editor:
Mehta and colleagues1 observed 2119 patients with coronary bypass grafts undergoing coronary angiography and then compared (1) patients with and without a patent internal mammary graft and (2) patients who did versus those who did not undergo saphenous vein graft (SVG) percutaneous coronary intervention (PCI). The authors found that patients who underwent PCI of the SVG at the time of angiography had significantly worse clinical outcomes compared with those who did not. They concluded that “SVG intervention had no measurable survival benefit but was associated with an increased risk of nonfatal myocardial infarction” (p I-396).
The authors are to be commended for improving our understanding of the natural history of patients with SVGs undergoing coronary angiography. Yet, we believe that the above conclusion may not be supported by the data presented in the article. Specifically, the comparison between patients undergoing SVG PCI and those who did not may be invalid, because patients undergoing SVG PCI have significant differences from those who do undergo SVG PCI and are more likely to have worse clinical outcomes. Indeed, as shown in Table 1 in the article by Mehta et al,1 virtually all patients who underwent SVG PCI had significant SVG angiographic disease compared with 19.3% of patients who did not undergo SVG PCI. In addition, patients who underwent SVG PCI were more likely to undergo native coronary artery intervention (12.1% versus 0.3%). Even though the authors did a multivariate analysis to adjust for differences in native and vein graft atherosclerosis, this would still be unlikely to compensate fully for the baseline differences between the 2 groups.
We believe that no inferences could be made regarding the utility of SVG PCI on the basis of their study.1 Instead, a more accurate conclusion would be that compared with coronary bypass patients who did not undergo SVG PCI, those who did undergo SVG PCI had a higher incidence of nonfatal myocardial infarction at follow-up.
Dr Brilakis is supported by the Clark R. Gregg Fund of the Harris Methodist Health Foundation and by a Veterans Affairs VISN 17 start up award.
Mehta RH, Honeycutt E, Peterson ED, Granger CB, Halabi AR, Shaw LK, Smith PK, Califf RM, Harrington RA, Sketch MH Jr. Impact of internal mammary artery conduit on long-term outcomes after percutaneous intervention of saphenous vein graft. Circulation. 2006; 114 (suppl I): I-396–I-401.