Routine visualization of the left internal mammary artery before bypass surgery: is it necessary?

The left internal mammary (LIMA) is an ideal conduit for bypassing the left anterior descending artery (LAD) during coronary artery bypass surgery (CABG). In this study, we evaluate the frequency of significant disease in the LIMA prior to CABG and describe associated significant lateral costal branches (> 1.5 mm), subclavian disease and vertebral disease. In 115 consecutive patients referred to CABG, 101 patients met the inclusion criteria. All patients who underwent routine visualization of the LIMA vessels were reviewed and quantitatively analyzed by an independent reader. Disease in the LIMA, left subclavian and vertebral arteries were graded and considered significant if lesions were > 50%. Lateral costal branches of the LIMA were also noted for their presence and size. Of the 101 patients, 87.1% of the LIMAs prior to surgery were without any disease. One LIMA had a 25-50% narrowing and the remaining LIMAs showed 0-25% disease. Of the LIMAs, 48.5% had lateral costal branches with diameters > 1.5 mm. The incidence of significant left vertebral disease and proximal subclavian disease was 37.6% and 5%, respectively. Cardiolite stress imaging post-CABG (n = 75) showed that when ischemia persisted in the anterior wall in patients with a LIMA to the LAD, this was not associated with the presence of significant LIMA disease, lateral costal branches, or subclavian disease identified pre-operatively. We conclude that the LIMA rarely shows significant disease on routine visualization prior to CABG. Asymptomatic subclavian artery disease and the presence of lateral costal branches pre-operatively did not correlate with post-CABG ischemia in the LAD territory.

Identification of an interleukin-15alpha receptor-binding site on human interleukin-15.

To identify the epitopes in human interleukin-15 (IL-15) that are responsible for binding to the interleukin-15 receptor alpha chain, antibody and receptor mapping by peptide scanning and site-directed mutagenesis was used. By using peptide scanning, we identified four regions in IL-15. The first region ((85)CKECEELEEKN(95)) is located in the C-D loop and is recognized by a set of non-inhibitory antibodies. The second region ((102)SFVHIVQMFIN(112)) is located in helix D and is recognized by two antibodies that are inhibitory of IL-15 bio-activity but not of IL-15 binding to IL-15Ralpha. The two remaining regions react with a recombinant soluble form of the IL-15Ralpha; the first ((44)LLELQVISL(52), peptide 1) corresponds to a sequence located in the B-helix and the second ((64)ENLII(68), peptide 2) to a sequence located in helix C. The latter is also contained in the epitope recognized by an antibody (monoclonal antibody B-E29) that prevents IL-15 binding to IL-15Ralpha. By site-directed mutagenesis, we confirmed that residues present in peptide 1 (Leu-45, Glu-46, Val-49, Ser-51, and Leu-52) and peptide 2 (Leu-66 and Ile-67) are involved in the binding of IL-15 to IL-15Ralpha. Furthermore, the results presented indicate that residues in the second peptide (Glu-64, Asn-65, and Ile-68) participate in IL-2Rbeta recruitment. This finding could have implications for the dynamics of receptor assembly. These results also indicate that the modes of interaction of IL-15 and IL-2 with their respective alpha chains are not completely analogous. Finally, some of the IL-15 mutants generated in this study displayed agonist or antagonist properties and may be useful as therapeutic agents.

In-hospital complications of peripheral vascular interventions using unfractionated heparin as the primary anticoagulant.

Unfractionated heparin is the current antithrombotic of choice in peripheral vascular interventions. The rate of in-hospital major complications during peripheral angioplasty procedures (PTA) using heparin as the primary anticoagulant has not been well defined. In this single-center study, the charts of 213 consecutive PTA procedures in a 1-year period were reviewed. Of unstaged procedures, a total of 131 patients (57.3% males; mean age, 66.4 12.1 years) met inclusion criteria. Forty-five patients (34.4%) had recent onset of claudication and 15 (11.5%) had ulceration. Thrombus was angiographically visualized in 16.7% of patients. Unfractionated heparin was administered at a mean of 4,672 1,238 U (59.1 20.0 U/kg) during the procedure. The highest activated clotting time (ACT) during the procedure was recorded in 114 patients. ACTs were < 300, 300 400 and > 400 seconds in 29.0%, 29.0% and 42.1%, respectively. In-hospital clinical events occurred in 12 patients (9.2%) who met any one of the following endpoints: death (0.8%), limb loss (1.5%), major bleeding (4.6%), emergent need for repeat revascularization of the same vessel (7.6%), embolic stroke (0.0%) and vascular complications (1.5%). The best model associated with salvage revascularization included cigarette smoking within the past year, recent onset of claudication and PTA treatment below the knee. Increased dosages of heparin (U/kg) were associated with a trend toward higher rates of complications. A significant number of patients have in-hospital major complications following PTA procedures using unfractionated heparin as the primary anticoagulant. Current ongoing registries are evaluating the feasibility of direct thrombin inhibitors bivalirudin instead of heparin as a primary anticoagulant during PTA.