Hymenoptera sting anaphylaxis and urticaria pigmentosa: clinical findings and results of venom immunotherapy in ten patients

BACKGROUND

Occasional patients with urticaria pigmentosa and anaphylaxis after Hymenoptera stings have been described. In this situation the question arises: Is anaphylaxis IgE-mediated or induced by pharmacologic mediator release from mast cells?

METHODS

We investigated 10 patients with histologically confirmed urticaria pigmentosa and a history of anaphylaxis after honeybee or Vespula stings before and during immunotherapy with the respective venom.

RESULTS

In eight of 10 patients, an elevated serum tryptase level was found. In two of 10 patients, no venom-specific IgE could be detected by either skin tests or RAST. Five patients had no detectable venom-specific serum IgE, and in the remaining patients the level was low (<1 Phadebas RAST unit). Venom immunotherapy was well tolerated and caused only one mild systemic reaction in a patient during the dose increase phase. Six patients were re-stung while receiving venom immunotherapy: only one had a mild systemic reaction (angioedema) after a Vespula sting.

CONCLUSION

Anaphylactic symptoms after Hymenoptera stings in patients with urticaria pigmentosa are most often IgE-mediated but can occasionally be observed in the absence of IgE sensitization to venom allergens. Venom immunotherapy can be safely and successfully used in patients with urticaria pigmentosa and sting anaphylaxis.

A requirement for Flk1 in primitive and definitive hematopoiesis and vasculogenesis

Mouse embryos lacking the receptor tyrosine kinase, Flk1, die without mature endothelial and hematopoietic cells. To investigate the role of Flk1 during vasculogenesis and hematopoiesis, we examined the developmental potential of Flk1-/- embryonic stem cells in chimeras. We show that Flk1 is required cell autonomously for endothelial development. Furthermore, Flk1-/- cells do not contribute to primitive hematopoiesis in chimeric yolk sacs or definitive hematopoiesis in adult chimeras and chimeric fetal livers. We also demonstrate that cells lacking Flk1 are unable to reach the correct location to form blood islands, suggesting that Flk1 is involved in the movement of cells from the posterior primitive streak to the yolk sac and, possibly, to the intraembryonic sites of early hematopoiesis.

Implementation and evaluation of patient-specific three-dimensional internal dosimetry

Current methods for calculating the absorbed dose in a target region from a source region rely on a standard "reference man" geometry and assume an uniform distribution of radiolabel. While this approach is acceptable at the low levels of radioisotope administered for most diagnostic purposes, the generality of the calculations is not adequate for doses at the higher levels required for therapy and is not easily extendible to tumor dosimetry.

METHODS

We have developed an integrated system which utilizes patient anatomy and radionuclide distribution in the calculation of absorbed dose rate or total dose to any user-defined target region. Images of radionuclide distribution (PET/SPECT) are registered to anatomic images (CT/ MRI) and then entered into a three-dimensional internal dosimetry software system (3D-ID) where regions of interest are defined. Dose calculations are performed by the mathematical convolution between a user-specified, dose-point kernel with the activity in the source volume over the target volume. The resulting dose rate distribution may be scaled by cumulated activity to yield absorbed dose. In addition to calculating the mean dose, dose-volume histograms may be generated which plot absorbed dose with respect to percent of volume. The method was evaluated using selected standard man phantom organs.

RESULTS

Dose estimates for two patient studies are included to illustrate differences between patient-specific and MIRD-based calculations. The package provides an alternative approach to image display and three-dimensional internal dose calculations.

CONCLUSION

The dose-volume histogram representation of absorbed dose to a target volume provides valuable information in assessing tumor control probability and normal tissue toxicity.

The effect of treatment positioning on normal tissue dose in patients with prostate cancer treated with three-dimensional conformal radiotherapy

PURPOSE

To prospectively assess the effect of supine vs. prone treatment position on the dose to normal tissues in prostate cancer patients treated with the three-dimensional conformal technique.

METHODS AND MATERIALS

Twenty-six patients underwent three-dimensional treatment planning in both the supine and prone treatment positions. The planning target volume and normal tissue structures were outlined on each CAT scan slice, and treatment plans were compared to assess the effect of treatment position on the volume of rectum, bladder, and bowel exposed to the high dose of irradiation.

RESULTS

The average dose to the rectal wall and the V95 (volume of rectal wall receiving at least 95% of the prescription dose) for the prone position were 64 and 24% of the prescription dose, respectively, compared to 72 and 29%, respectively, for the supine position (p < 0.05). When the average rectal wall dose was used as an endpoint, 14 of the 26 patients (54%) had an advantage for the prone position compared to 1 (4%) who demonstrated an advantage for the supine position (p < 0.0002). Similarly, when V95 of the rectal wall was used as a measure of comparison, 15 patients (58%) had an advantage for the prone position compared to 1 (4%) who demonstrated an advantage for the supine position (p < 0.0002). In 13 patients (50%), a change from supine to the prone position was associated with reduction of the V95 to levels < 30% of the prescription dose compared to 3 patients (11%) in whom such an advantage resulted from change of the prone to the supine position (p < 0.005). The effect of treatment position on the rectal wall dose was most pronounced in the region of the seminal vesicles. An increased volume of bowel was also noted in the supine position. The treatment position, however, had no significant impact on the dose to the bladder wall.

CONCLUSIONS

Three-dimensional conformal radiotherapy for prostate cancer in the prone position is associated with significant reduction of the dose to the rectum and bowel resulting in an improvement in the therapeutic ratio.

Evolution of cardiovascular risk after liver transplantation: a comparison of cyclosporine A and tacrolimus (FK506)

The development of atherosclerotic cardiovascular complications is a common and serious problem for the long-term survivors of organ transplantation. Cyclosporine A plus steroid-based immuno-suppression regimens in these patients are associated with the development of hypertension, hyperlipidemia, obesity, and diabetes mellitus. Whether the new immunosuppressive agent tacrolimus (FK506) confers any advantage in terms of these cardiovascular risk factors has been less well studied. We compared serial changes in blood pressure, lipids, body weight, and glucose levels during the first 12 months after liver transplantation in patients using either cyclosporine A (n = 39) or tacrolimus (n = 24)-based immunosuppression. By 12 months, the prevalence of hypertension, hypercholesterolemia, and obesity was increased in the cyclosporine A group compared to tacrolimus: 82% versus 33%, 33% versus 0%, and 46% versus 29%, respectively (all p < .05). Triglyceride and total cholesterol levels were 196 +/- 23 versus 125 +/- 13 mg/dL and 225 +/- 9 versus 159 +/- 7 mg/dL for the cyclosporine A versus tacrolimus groups, respectively (p < .05). Cumulative posttransplant steroid dose was not related to the observed lipid changes in either group, although the increase in triglycerides was positively correlated to weight gain and diuretic use in the cyclosporine A group. The incidence of diabetes mellitus was not increased from baseline in either group. These results indicate that tacrolimus, compared to cyclosporine A, is associated with a less adverse cardiovascular risk profile in the first year after liver transplantation. Whether these differences persist and become clinically relevant to a liver transplant recipient population that is increasingly older and has more preexisting cardiovascular disease remains to be determined.

Role of steroid dose in hypertension early after liver transplantation with tacrolimus (FK506) and cyclosporine

Transplant immunosuppression using either cyclosporine (CsA) or tacrolimus (FK506) leads to renal vasoconstriction and nephrotoxicity. Despite producing similar effects within the kidney and blood vessels, clinical hypertension occurs less frequently with tacrolimus during the first year after transplantation, compared with CsA. To examine the role of steroid dose in early posttransplant hypertension, we measured blood pressure and kidney function in liver transplant recipients treated with tacrolimus and either high-dose (TAC-HI-P, n = 19) or low-dose (TAC-LO-P,n = 20) prednisone, compared with CsA-treated recipients (n = 29) receiving prednisone doses similar to the TAC-HI-P group. At 1 month, hypertension occurred more often with CsA (72%) than with TAC-HI-P (42%, P < 0.05) or TAC-LO-P (30%, P < 0.05). By 4 months after transplantation, hypertension developed in nearly twice as many TAC-HI-P (63%) as TAC-LO-P patients (32%, P < 0.05), with no difference between TAC-HI-P and CsA (86%, NS). Daily prednisone dose at 1 month closely paralleled cumulative steroid dose in the first month in the TAC-HI-P and TAC-LO-P groups. Fourteen of 19 TAC-HI-P patients (74%) required bolus steroids for treatment of rejection within the first month, compared with 3/20 (15%) TAC-LO-P and 10/29 (34%) CsA recipients. Glomerular filtration rate fell from pretransplant levels at 1 month and 4 months to the same degree in CsA, TAC-HI-P, and TAC-LO-P patients. These results demonstrate a central role for steroid dose in the rate of onset of hypertension early after liver transplantation using tacrolimus immunosuppression. Both daily dose and cumulative dosage, including bolus treatment for rejection, may impact on the development of hypertension. Since prevalence rates rise to levels comparable to CsA by 24 months regardless of steroid dose, hypertension after liver transplant may be mediated by different mechanisms at different stages of the posttransplant course.

The V-stent: a novel technique for coronary bifurcation stenting

Intracoronary stenting as a transcatheter treatment for bifurcation stenoses remains controversial. A novel technique of coronary bifurcation stenting is reported. A 15 mm Palmaz-Schatz stent is bent 180 degrees at its bridge articulation into a V- configuration and mounted on two balloon-catheters linked together by adhesive tape. This unified stent delivery system was used successfully in five cases of porcine coronary bifurcation stenting.

Estrogen and progesterone receptor expression in endometrial polyps

Endometrial polyps are a frequent cause of abnormal uterine bleeding, but their pathogenesis is poorly understood. This study was undertaken to investigate if endometrial polyps result from localized overexpression of estrogen receptors (ERs) or reduced expression of progesterone receptors (PRs). Fourteen cases of endometrial polyps, in which normal cycling endometrium was also present on the same slide, were immunostained for ERs and PRs. Percentages of positive cells in glands and stroma for each receptor were subjectively assessed to the nearest 5%. The intensity of staining was recorded on a scale from 1+ to 4+. The level and intensity of staining in polyps were compared with the staining in normal endometrium. Fewer stromal cells in polyps expressed ERs and PRs compared with cycling endometrium (% ER = 55.9 +/- 25.8 vs. 74.3 +/- 25.8, p = 0.03; % PR = 56.1 +/- 28.2 vs. 87.5 +/- 10.1, p = 0.002). Stroma in polyps also had significantly reduced intensity of staining for PRs, but not for ERs (intensity PR = 2.7 +/- 1.4 vs. 3.5 +/- 0.7, p = 0.015; intensity ER = 2.1 +/- 0.7 vs. 2.4 +/- 0.8, p = 0.45). There were no significant differences in expression of ERs and PRs in the endometrial glands in endometrial polyps compared with normal endometrium (% ER = 75.4 +/- 32.5 vs. 70.7 +/- 39.2. p = 0.25; % PR = 79.6 +/- 32.8 vs. 80.4 +/- 34.4, p = 0.8; intensity ER = 2.7 +/- 0.9 vs. 2.4 +/- 1, p = 0.15; intensity PR = 2.9 +/- 1.4 vs. 3.4 +/- 0.7, p = 0.15). We conclude that endometrial polyps may result from a decrease in ER and PR expression in stromal cells. Because of these receptor-negative stromal cells, endometrial polyps may be relatively insensitive to cyclic hormonal changes.

Cell autonomous functions of the receptor tyrosine kinase TIE in a late phase of angiogenic capillary growth and endothelial cell survival during murine development

TIE is a receptor tyrosine kinase expressed in both mature endothelial cells and their precursors, as well as in some hematopoietic cells. Mouse embryos homozygous for a disrupted Tie allele die at midgestation due to impaired endothelial cell integrity and resulting hemorrhage. Here we have performed chimeric analysis to study further the function of the murine TIE in the development of embryonic vasculature and in the hematopoietic system. Cells lacking a functional Tie gene (tie(lcz)/tie(lczn-) cells) contributed to the embryonic vasculature at E10.5 as efficiently as cells heterozygous for a targeted Tie allele (tie(lcz)/+ cells). Thus, TIE does not play a significant role in vasculogenesis or in early angiogenic processes, such as formation of the intersomitic arteries and limb bud vascularization. At E15.5 tie(lcz)/tie(lczn-) cells still readily contributed to major blood vessels and to endothelial cells of organs such as lung and heart, which have been suggested to be vascularized by angioblast differentiation. In contrast, the tie(lcz)/tie(lczn-) cells were selected against in the capillary plexuses of several angiogenically vascularized tissues, such as brain and kidney. Our results thus support a role for TIE in late phases of angiogenesis but not vasculogenesis. Furthermore, the results suggest that different mechanisms regulate early and late angiogenesis and provide support for a model of differential organ vascularization by vasculogenic or angiogenic processes. Analysis of adult chimeras suggested that TIE is required to support the survival or proliferation of certain types of endothelial cells demonstrating heterogeneity in the growth/survival factor requirements in various endothelial cell populations. Chimeric analysis of adult hematopoietic cell populations, including peripheral platelets and bone marrow progenitor cells, revealed that tie(lcz)/tie(lczn-) cells were able to contribute to these cell types in a way indistinguishable from tie(lcz)/+ or wild-type cells. Thus, the primary function of TIE appears to be restricted to the endothelial cell lineage.

Coronary artery stenting: indications and cost implications

The practice of coronary stenting is evolving rapidly, with new stent designs, deployment techniques, and adjunctive therapy. In many respects, clinical practice is changing in advance of the availability of supporting data. The consistent excellent angiographic result with stent deployment exceeds that achieved by any other previous interventional device, and the extent to which this accounts for the exponential increase in stent utilization cannot be accurately determined but is undoubtedly considerable. Controlled randomized trials have confirmed that stent deployment is superior to balloon angioplasty in certain lesion subsets or clinical scenarios. These include focal de novo native vessel lesions, lesions with late recoil after balloon angioplasty, acute closure after balloon angioplasty, and proximal left anterior descending coronary artery lesions. In addition, observational data is persuasive in focal coronary saphenous vein graft lesions and aorto-ostial lesions. On the other hand, the evidence supporting the use of stents strictly to improve on a suboptimal result, possibly the most frequent indication, is indirect and circumstantial. Stents are expensive, but it was anticipated that with the reduction in restenosis not only would they be cost-effective but also ultimately would reduce costs. This hope has not as yet been realized. However, there is little question that the introduction of intracoronary stents has been the most significant and exciting development since the introduction of percutaneous revascularization almost 20 years ago. It has revitalized the field.

Nurse management of posttransplant hypertension in liver transplant patients

Hypertension develops soon after organ transplantation using cyclosporine- or FK506-based immunosuppression. Sustained rises in blood pressure require intervention to reduce the risk of intracranial bleeding and other cardiovascular complications. Antihypertensive treatment is complicated by reduced renal function and potential interference with absorption and/or metabolism of cyclosporine or FK506. To manage early and long-term hypertension related to immunosuppression with cyclosporine or FK506 and prednisone following orthotopic liver transplantation, a comprehensive nurse-managed hypertension clinic was developed. Blood pressure, heart rate, and antihypertensive and immunosuppressive regimens were evaluated according to a standard protocol at 1, 4, 12, 24, and 36 months after orthotopic liver transplantation. Data indicate that posttransplantation hypertension develops within the first months after orthotopic liver transplantation and persists indefinitely. If comprehensively managed by the hypertension nurse-clinician, the percentage of controlled hypertension patients can increase over time.

Coronary 'Y' stenting: a technique for angioplasty of bifurcation stenoses

This report describes a case of successful percutaneous coronary transluminal angioplasty (PTCA) of a coronary artery bifurcating lesion using multiple intracoronary stents in an inverted 'Y' configuration. Balloon angioplasty of bifurcation coronary stenoses has a lower procedural success rate, higher restenosis rate and potential for side branch occlusion compared with nonbifurcation lesions. Numerous techniques, including two ('kissing') angioplasty balloons, have been used to overcome these problems. The authors believe that the technique described in this report, inserting stents into both branches simultaneously followed by a third proximal stent in a 'Y' configuration, allows successful dilatation of the bifurcation lesion while preserving flow into both branches and should be considered for similar complex anatomical subsets.

The role of pain behaviors in the modulation of marital conflict in chronic pain couples

Sixty-one married male chronic benign back patients and their spouses were recruited in order to examine the relationship between marital conflict/stress and patient pain behaviors. The results suggest that marital conflict in pain couples is associated with increases in subsequent display of pain behaviors which, in turn, are associated with greater negative affective responses and more punitive behaviors by the spouse. A positive association was found between punitive spouse behaviors and patient physical and psychosocial impairment. The findings are discussed in terms of their clinical implications and the need for further experimental study of these relationships.

Scleritis and mucosal-associated lymphoid tissue lymphoma: a new masquerade syndrome

PURPOSE

To present a new masquerade syndrome showing features of mucosal-associated lymphoid tissue (MALT) lymphoma associated with choroidal white dots and scleritis. Differentials including systemic lymphoma, central nervous system lymphoma, and etiologies of white-dot syndromes and scleritis are discussed.

PATIENTS AND METHODS

A 42-year-old man who had decreased vision and ocular redness of his right eye for 4 years had a biopsy-proven diffuse anterior and posterior scleritis associated with intense circumferential perilimbal chemosis and ipsilateral yellow-white choroidal dots. A new conjunctival biopsy was performed because of unresponsiveness to high-dose systemic steroid and cyclophosphamide therapy. Immunostains for lymphocyte markers were preformed.

RESULTS

A morphologically and immunohistochemically typical, monotypical mu-kappa immunoglobulin light chain secreting B-cell MALT-lymphoma was diagnosed. Eighteen months after completion of radiotherapy, the patient recovered completely, except for the choroidal dots, which remained unchanged.

CONCLUSION

When scleritis, even histologically proven, fails to respond to immunosuppressive therapy, a new biopsy is mandatory to rule out a misdiagnosed MALT lymphoma.

Angioplasty of isolated acute marginal coronary artery disease

This report describes a patient who presented with a non Q wave myocardial infarction and post-infarction angina. Angiography revealed that his only significant disease was a severe lesion in an acute marginal branch of the right coronary artery. Balloon angioplasty was performed successfully with subsequent stabilization and no recurrence of angina in a 9-month follow-up. This case raises the possibility that acute marginal disease may contribute to ischemic syndromes and warrants consideration for revascularization.

The effects of in utero diagnostic X-irradiation on the development of preschool-age children

High doses of X-irradiation may affect the developing human embryo and fetus, causing brain, eye, skeletal and other defects. Although the doses used in diagnostic irradiation are not considered to be high enough to cause fetal anomalies, it is unknown whether they affect the long-term development of the in utero exposed children. Using the Bayley or McCarthy developmental scales we examined 52 children born to mothers exposed to diagnostic X-irradiation of the abdomen and/or pelvis during the first trimester of pregnancy, 60 children born to mothers exposed during pregnancy (58 in the first trimester) to X-rays in areas other than the abdomen or pelvis, and 62 normal children without maternal exposure to X-rays during pregnancy. All children were aged 1-5 years at examination. Parental socioeconomic status was the same in all three groups. There were no differences in the results of the medical and neurological examination, and in the motor or congnitive scores among three groups. Embryonic or fetal exposure to X-irradiation in doses below 5 rads does not seem to have any effect on development during childhood.

Initial report of rotational ablation: the Toronto Hospital experience

OBJECTIVE

To describe the initial experience of rotational ablation (using the Rotablator device), in terms of safety and the effectiveness as a proportion of final angiographic outcome when combined with adjunctive balloon angioplasty.

DESIGN

Retrospective analysis of single-centre experience, including operator learning curve.

SETTING

Tertiary care hospital, Cardiac Catheterization Laboratory.

PATIENTS

Consecutive subjects (14 men, 11 women) selected for rotational ablation based on ostial/bifurcation lesions (n = 10), 'long' (more than 10 mm) stenoses (n = 11) or extensive dystrophic calcification (n = 4).

INTERVENTIONS

Rotational ablation (Rotablator) with routine adjunctive balloon angioplasty. Quantitative coronary arteriography using the Cardiac Measurement System.

RESULTS

Rotational ablation reduced coronary obstruction, as demonstrated by minimal lumen diameter (preprocedure, 0.57 =/- 0.28 to 1.17 +/- 0.32 mm, P<0.05), with further improvements following adjunctive balloon angioplasty (1.93 +/- 0.35 mm). Similar changes were observed in relative stenosis after Rotablator (preprocedure, 79.7 +/- 7.6 to 56.1 +/- 13.1% diameter), with typical post-angioplasty residual narrowings (29.7 +/- 8.2% diameter). Estimated stenotic flow reserve was improved by the interventional procedures (preprocedure, 0.94 +/- 0.70; rotational ablation 3.07 +/- 1.14; and angioplasty, 4.73 +/- 0.25 times baseline). Complications were acceptable, and included three acute occlusions requiring balloon angioplasty recanalization and three non-Q wave myocardial infarctions (with creatine phosphokinase levels of 270, 417 and 602 IU, respectively).

CONCLUSIONS

The Rotablator is a relatively user-friendly device with a reasonable safety profile, accounting for approximately 50% of minimum lumen diameter gains when used in conjunction with routine balloon angioplasty. The precise role of rotational ablation, particularly in the context of preselected lesion specific uses (bifurcations, long lesions, dystrophic calcification), requires prospective, randomized studies.

Clinical applications of proton therapy

Proton therapy offers considerable potential advantages in the management of poorly resectable, radio-resistent tumors close to critical anatomical structures. So far over 15,000 patients have been treated worldwide with two major indications: conservative management of ocular melanomas in which local control exceeds 95% at 5 years and curative irradiation of sarcomas at the base of the skull and cervical canal, with a survival rate between 84 and 94% at 5 years. The different protocols tested currently worldwide are discussed.

Double-blind comparison of cefazolin and ceftizoxime for prophylaxis against infections following elective biliary tract surgery

Antibiotics have been shown to reduce the incidence of wound infections after elective biliary tract procedures. Cefazolin and cefoxitin are among the agents most commonly promoted for this purpose. Cefoxitin has been substituted with ceftizoxime in many institutions; however, the role of ceftizoxime as a prophylactic agent in this setting has not been determined. To assess the comparative prophylactic efficacies of cefazolin and ceftizoxime in biliary tract surgery, we conducted a double-blind, randomized prospective clinical trial in a tertiary-care teaching hospital. Adult patients were randomized to one of two treatment groups and received a 30-min preoperative dose of study drug and as many as two postoperative doses at 12 and 24 h, depending on hospitalization status. Cefazolin and ceftizoxime were given as 1,000-mg doses. Patients with infections, those receiving prior antibiotics, or those with beta-lactam allergies were excluded. Over the 19-month study tenure, 167 patients were enrolled. Seventeen patients were excluded from analysis because of protocol violations. Of the 150 evaluable patients (72 and 78 receiving cefazolin and ceftizoxime doses, respectively), there was no significant difference among groups regarding sex, age, weight, preoperative Apache II score, baseline chemistry, and hematological parameters. Groups were also equivalent regarding the surgeon, type of procedure, characteristics (blood loss, drains, organ injury, and complications), and duration of hospital stay (mean, 5.6 versus 4.3 days [P = 0.31]). No clinical evidence of infection (7-day hospital stay and 30-day follow-up) was identified in 93% of cefazolin and 92% of ceftizoxime patients (P = 1.0). Microbiological confirmation was found in only 18% of primary-site infections. In conclusion, cefazolin and ceftizoxime appear to be equivalent for the prevention of infection in biliary tract surgery with the dosage regimens studied.

Initial results with one-year minimum follow-up of the first 146 patients with a uveal melanoma treated with protons at CPO (Orsay)

Proton therapy began at the 'Centre de Protonthérapie d'Orsay' (CPO) in September 1991. Our treatment protocol and the preliminary results have been presented on the first 146 irradiated patients with one-year minimal follow-up. The subsequent developments have also been mentioned.

[Apoptosis and cancer]

Apoptosis is a mode of active cell death having distinct biochemical and morphological features including chromatin condensation, polynucleosomal DNA fragmentation, and disruption of cells into apoptotic bodies. The apoptotic process plays a major role both during development and in the functioning of the immune system. Apoptosis may in part be genetically regulated, and may also be linked to physiological and non physiological signals from the environment. Apoptosis may be a defense at the cellular level against cancer. Moreover, there is evidence that a number of pro-oncogenes and tumor suppressor genes are involved in regulating apoptosis. Further understanding of the molecular events underlying the apoptotic process should provide new insights into the mechanism of tumorigenesis and facilitate the development of new strategies for the treatment of cancer.

Antithrombotic therapy in patients with saphenous vein and internal mammary artery bypass grafts

In most studies, aspirin has been shown to be effective for a period of 1 year in reducing the frequency of saphenous vein bypass graft occlusion when begun 1 day before surgery, on the day of surgery, or the day after surgery. Effective doses of aspirin range from 100 to 975 mg/d. Aspirin in combination with dipyridamole is effective in the prevention of saphenous vein bypass graft occlusion if aspirin and dipyridamole therapy is started 1 or 2 days before surgery or aspirin therapy is started on the day of surgery but dipyridamole therapy is started before surgery or if treatment with both aspirin and dipyridamole is started 1 day after surgery. Aspirin in combination with dipyridamole is not more effective than aspirin alone in the prevention of saphenous vein graft occlusion. Bleeding is higher among patients treated with aspirin alone than among controls if aspirin therapy is started 1 day before surgery. Bleeding is not greater in comparison to controls if aspirin therapy is started the day of surgery or 1 day after surgery. When aspirin and dipyridamole are used in combination, bleeding is higher than in controls, and bleeding is higher than with aspirin alone. The continued use of aspirin for 2 additional years after an initial year of aspirin therapy for the prevention of saphenous vein bypass graft occlusion showed no additional long-term benefit on graft patency at the end of the third year.