Relative importance of patient, procedural and anatomic risk factors for early vein graft thrombosis after coronary artery bypass graft surgery.

AIM: The aim of the present study was to investigate the relative importance of a wide array of patient demographic, procedural, anatomic and perioperative variables as potential risk factors for early saphenous vein graft (SVG) thrombosis after coronary artery bypass graft (CABG) surgery. METHODS: The patency of 611 SVGs in 291 patients operated on at four different hospitals enrolled in the Reduction in Graft Occlusion Rates (RIGOR) study was assessed six months after CABG surgery by multidetector computed tomography coronary angiography or clinically-indicated coronary angiography. The odds of graft occlusion versus patency were analyzed using multilevel multivariate logistic regression with clustering on patient. RESULTS: SVG failure within six months of CABG surgery was predominantly an all-or-none phenomenon with 126 (20.1%) SVGs totally occluded, 485 (77.3%) widely patent and only 16 (2.5%) containing high-grade stenoses. Target vessel diameter ≤ 1.5 mm (adjusted OR 2.37, P=0.003) and female gender (adjusted OR 2.46, P=0.01) were strongly associated with early SVG occlusion. In a subgroup analysis of 354 SVGs in which intraoperative graft blood flow was measured, lower mean flow was also significantly associated with SVG occlusion when analyzed as a continuous variable (adjusted OR 0.984, P=0.006) though not when analyzed dichotomously, <40 mL/min versus ≥ 40 mL/min (adjusted OR 1.86, P=0.08). CONCLUSION: Small target vessel diameter, female gender and low mean graft blood flow are significant risk factors for SVG thrombosis within six months of CABG surgery in patients on postoperative aspirin therapy. This information may be useful in guiding revascularization strategies in selected patients.

Effect of anti-platelet factor-4/heparin antibody induction on early saphenous vein graft occlusion after coronary artery bypass surgery.

BACKGROUND: Antibodies to complexes of heparin and platelet factor 4 (PF4) are capable of causing heparin-induced thrombocytopenia (HIT). Recent evidence suggests that anti-PF4/heparin antibodies may be prothrombogenic even in the absence of thrombocytopenia and clinically-recognized HIT. OBJECTIVES: To determine if induction of anti-PF4/heparin antibodies is an independent risk factor for early saphenous vein graft (SVG) occlusion or adverse clinical outcome after coronary artery bypass graft (CABG) surgery. PATIENTS/METHODS: Anti-PF4/heparin antibody titers were measured in 368 patients prior to and then 4 days, 6 weeks and 6 months after CABG surgery. Serotonin release assay (SRA) and antibody isotype analysis were also performed on 6-week samples. SVG patency was determined in 297 patients 6 months after surgery by multidetector computed tomography coronary angiography. RESULTS: Six weeks after surgery, 52% of patients were anti-PF4/heparin seropositive and 9% were SRA positive. Six months after surgery, neither the percentage of occluded SVG (19% vs. 20%, P = NS), the percentage of patients with an occluded SVG (33% vs. 33%, P = NS) nor the incidence of adverse clinical events (21% vs. 24%, P = NS) differed between seropositive and seronegative groups. Neither IgG isotype nor SRA positivity was additionally predictive of SVG occlusion or adverse clinical outcome. CONCLUSION: Induction of anti-PF4/heparin antibodies, even those capable of heparin-dependent platelet activation, is not independently associated with early SVG occlusion or adverse clinical outcomes after CABG surgery.

Factor analysis of regional cerebral glucose metabolic rates in healthy men.

Cerebral glucose utilization measured with fluorine-18-fluoro-2-deoxy-D-glucose is characterized by considerable variability both among different persons and for the same person examined on different occasions. The goal of this study was to explore whether some regions of the brain were more variable than others with respect to glucose utilization and whether there was a pattern in their covariance. The global and regional cerebral utilization of glucose was measured in 12 healthy young volunteers on 3 or 4 occasions. In all, 24 regions were examined. The interrelation of the glucose utilization rates of the brain regions was investigated by factor analysis of the metabolic rates. Some 70% of the total variance was attributable to only 1 factor, while 80% of the total variance could be attributed to 2 factors. Regions making up the first factor were the frontal and temporal cortex, cingulate gyrus, caudate nucleus, thalamus and putamen. These regions are functionally related to the limbic system. Regions of the second factor were the parietal cortex, occipital cortex and cerebellum, regions more clearly related to sensory and motor functions. The 2-factor pattern was highly reproducible, being found with different algorithms for factor extraction and rotation. Under resting conditions, the variance of cerebral metabolism seems to be primarily related to regions which are closely involved with the limbic system. Cortical regions involved primarily in motor and sensory functions have less influence on the variance.

Reduced left ventricular cavitary activity ("black hole sign") in thallium-201 SPECT perfusion images of anteroapical transmural myocardial infarction.

Apparently reduced left ventricular (LV) cavitary thallium activity in both planar and tomographic perfusion images has been previously observed by these and other investigators. With single-photon emission computerized tomography, we have clinically noted that this "black hole sign" was associated with an aneurysm in the setting of a transmural anterior or anteroapical perfusion defect. We have now prospectively studied the etiology and predictive value of this sign in 84 consecutive patients with an anterior, anteroapical transmural perfusion defect. Of the 84 patients, 49 had both LV aneurysm (confirmed by contrast ventriculography, echocardiography or gated blood pool studies) and a black hole sign. Only 1 patient with an aneurysm did not have the black hole sign, and 2 without aneurysm did. Thus, it is concluded that this sign is highly accurate in diagnosing LV aneurysm. Because thallium-201 single-photon emission computerized tomography imaging is often performed as one of the first diagnostic tests soon after myocardial infarction, this has important clinical management implications.

Failure of perchlorate to inhibit Tc-99m isonitrile binding by the thyroid during myocardial perfusion studies.

The thyroid gland receives an average radiation dose of 3 rads during two Tc-99m isonitrile (MIBI) myocardial perfusion studies, if 20 mCi is administered both at rest and at peak exercise. In patients with coronary artery disease, multiple myocardial perfusion studies may be required, resulting in a high level of thyroid radiation. We attempted to reduce this radiation exposure by blocking thyroidal Tc-99m MIBI uptake with oral potassium perchlorate (KCIO4). Fourteen normal subjects received 0.6g to 0.8g KCIO4 20-25 minutes before tracer injection. Subjects who received KCIO4 at rest (n = 11) did not receive KCIO4 at their stress study, and vice versa (n = 3). Thyroid uptake values were obtained with a thyroid probe 20 minutes after injection for both rest and stress studies and were corrected for saturation effects. There was no difference between fractional thyroid uptake values with and without preceding perchlorate administration: 1.9 +/- 0.5% and 1.8 +/- 0.3% (mean +/- SD), respectively. Failure to block Tc-99m MIBI uptake after intravenous (IV) injection is probably due to high thyroidal blood flow and nonspecific tracer accumulation. The concentration of this radioisotope in adjacent muscles also contributes to the high thyroid radiation dose. In summary, administration of KCIO4 before Tc-99m MIBI studies does not reduce the thyroidal radiation dose or uptake of this tracer, suggesting that thyroidal uptake of this tracer is not mediated by the iodine trapping mechanism.

Global and regional cerebral metabolic rate of 2-[18F]fluoro-2-deoxy-D-glucose in the presence of ofloxacin, a gamma-aminobutyric acid a receptor antagonist.

We investigated the effects of ofloxacin, a new antibacterial quinolone gamma-aminobutyric acid A receptor antagonist, on the global and regional cerebral metabolic rates of glucose (cMRgl). Twelve healthy normal male volunteers (mean age, 26.7 years) were studied in a double-blind, placebo-controlled protocol of 11 days' duration. Results of a total of 42 positron emission tomography studies were obtained for these subjects: 12 base line, 18 during placebo, and 12 during ofloxacin administration. The conditions under which repeat positron emission tomography studies of the same subject were performed were reproduced as closely as possible. cMRgl was measured in 24 brain regions. The global cMRgl for base line, placebo, and ofloxacin were 8.82 +/- 1.17, 8.24 +/- 1.17, and 8.79 +/- 1.18 mg/min/100 g, respectively (mean +/- 1 standard deviation). The mean global differences between base line and placebo and between ofloxacin and placebo were 5.1 and 6.6%, respectively. Analysis of variance of both the global and the regional cMRgl showed no statistical difference between base-line, placebo, and ofloxacin studies. Variations in cMRgl found in this study were not related to the presence of ofloxacin. Results of our study demonstrate that ofloxacin does not increase or decrease cMRgl beyond the limits of variability of the study.