In vitro study of magnetic resonance imaging artefacts of six supraglottic airway devices.

We investigated the artefacts created during magnetic resonance imaging by five different laryngeal mask airways: the Classic (cLMA); the LMA ProSeal; the LMA Unique; the Ambu Disposable Laryngeal Mask; the LMA Supreme; and one other supraglottic airway device, the i-gel supraglottic airway. The devices were placed on top of and inside a phantom simulator to resemble the position in vivo. The artefacts with the cLMA, Unique and Supreme were similar and related to ferromagnetic material in the pilot balloon valve. Artefacts were more prominent with the ProSeal. There were no artefacts with the Ambu Disposable Laryngeal Mask or the i-gel.

A needleless closed system device (CLAVE) protects from intravascular catheter tip and hub colonization: a prospective randomized study.

Hub colonization and subsequent intraluminal progression due to frequent opening and manipulation of intravenous systems is the cause of many catheter-related infections (CRI). A prospective, comparative, randomized study was performed to assess a new closed-needleless hub device (CLAVE) compared with conventional open systems (COS). End-points were hub and skin colonization, catheter tip colonization, catheter-related bloodstream infection (CRBSI) and number of accidental needlesticks. All cultures were processed following standard semiquantitative microbiological techniques. The study involved patients who underwent heart surgery over an 11-month period in a post-surgical ICU. During the study period, 352 patients underwent major heart surgery and 1774 catheters were inserted. Overall, 865 catheters in 178 patients were allocated to the CLAVE system and 909 catheters in 174 patients to COS. The groups were similar regarding underlying conditions and risk factors for infection. Comparison of endpoint results in CLAVE and COS groups was as follows: incidence density per 1000 catheter-days of tip colonization: 59.2 versus 83.6 (P=0.003); of hub colonization: 7.56 versus 24.66 (P=0.0017); of skin colonization: 41.5 versus 58.9 (P=0.038); and of CRBSI 3.78 versus 5.89 (P=0.4). There was one accidental needlestick and one catheter-related prosthetic endocarditis in the COS group. Multivariate analysis showed that CLAVE use was an independent protective factor for tip colonization. CLAVE offered significant protection from catheter-tip and hub colonization.

Prevalence of diabetes mellitus and related conditions in a south Texas Mexican American sample.

The prevalence of self-reported diabetes mellitus in a Mexican American sample population living in Hidalgo County in south Texas was examined along with risk for related sequelae. Data from a stratified random sample of 849 Mexican American men and women ages 45 and older were examined. A subsample of 193 diabetics was compared to 656 nondiabetics with respect to hospitalization, reasons for hospitalization, and other related medical conditions. The prevalence of self-reported diabetes for both men and women was 25.9%. Hospitalization rates for diabetics over a 1-year period and a 5-year period were significantly higher than nondiabetics. Hypertension, cardiac problems, amputations, kidney or urinary problems, eye problems, and joint and bone problems were significantly more common in the diabetics sample than in the nondiabetic sample. The data indicate that diabetes in Mexican Americans may be undertreated in south Texas.

[Reoperations of myocardial revascularization]. / Reoperaciones de revascularización miocárdica.

UNLABELLED: Coronary by-pass grafting is a well established procedure for ameliorating ischemic coronary disease. From time to time it is necessary to re-operate these patients. The objective of our paper is to present our experience in this field. Retrospective analysis of 128 patients operated on between February 1978 and November 1996, has been analyzed. The mean age was 57.4 +/- 0.7 years. 77.2 +/- 5 months elapsed between operations. Stable angina (20.4%) or unstable angina (76.3%), myocardial infarction (48%) and congestive heart failure (17%) were the predominant clinical manifestations. RESULTS: Hospital mortality was 10.9% (14 patients) and in the follow-up there were 16 deaths (14%). Perioperative myocardial infarction was the main cause of in-hospital mortality. In the follow-up there were 4 deaths due to myocardial infarction and another 4 patients died from neoplasms. Perioperative myocardial infarction was present in 9.3% (12 patients) IN CONCLUSION: a) Re-do coronary by-pass grafting is still a good procedure for solving myocardial ischemia in spite of a higher mortality and morbidity than in the original operation. b) There is no progression in the number of patients according to our experience, probably due to better techniques and the frequent actions by an intervention cardiologist. c) The long-term results are good enough, but with a higher mortality.

A deleterious effect of aspirin on the antithrombotic properties of endothelial cells is not observed with platelets previously exposed to aspirin: studies in a flow system.

We have explored both the independent and combined effects of aspirin on cultured endothelial cells and platelets, and its influence on platelet deposition onto an extracellular matrix. Blood was circulated through a flat perfusion chamber with two coverslips placed sequentially with respect to blood flow. The first coverslip (upstream) was covered with a cultured endothelial cell monolayer, and the second (downstream) coated with extracellular matrix obtained after endothelial cell removal. Platelet interaction was measured on the second coverslip. Treatment of endothelial cells on the first coverslip with 100 µM aspirin strongly reduced 6-keto-PGF(1a) levels recovered in the perfusates (118.3 ± 35.8 vs 1038.0 ± 308.5 pg/ml) and significantly increased platelet deposition on the downstream coverslip (% covered surface: 38.6 ± 6.4% vs 14.6 ± 1.8%; P < 0.001). Increased platelet deposition (% covered surface: 24.9 f 3.1%; P < 0.01) was observed in perfusions performed with blood containing aspirinized platelets, in the presence of intact endothelial cells. Treatment with aspirin of both platelets and endothelial cells had no additional effect on platelet adherence. Pretreatment of cultured endothelial cells with aspirin did not influence the adhesive properties of their underlying extracellular matrix. Our results indicate that, although endothelial cell cyclooxygenase is important in regulating platelet adhesion, its blockade seemed to have minimal effect on platelet deposition once platelet-cyclooxygenase was already inhibited.

Effects of aspirin and indomethacin separately in red blood cells and platelets. Modulation of the adhesive and cohesive functions of platelets under flow conditions.

We treated red cells and platelet sepatately in vitro with aspirin or indomethacin to inhibit platelet function. The excess of drug was removed by profuse washing prior to blood reconstitution. We examined the influence of such treatments on platelet interaction with vascular subendothelium employing a perfusion system. Treatment of red cells or platelets with aspirin showed a similar pattern of platelet deposition onto subendothelium. However, platelet adhesion was significantly increased in treated red cells (21.7 ± 2.7% vs 13.7 ± 1.9% in controls; P < 0.05) whereas thrombus was significantly decreased in treated platelets (6.2 ± 1.62% vs 13.8 ± 1.7% in controls; P < 0.05). Treatment of red cells or platelets with indomethacin strongly inhibited platelet interaction. Thrombus and covered surface were decreased in experiments with treated red cells (2.3 ± 0.73% and 14.9 ± 2.3%, respectively; P < 0.05). Adhesion, thrombus and covered surface were decreased in experiments with treated platelets (4.3 ± 0.7%, 2.3 ± 0.9%, 9.2 ± 1.5%, respectively; P < 0.05). Platelet aggregation experiments performed with aspirin-treated red cells showed a progressive inhibition of platelet function. Testing levels of drug in plasma samples from the perfusates showed that levels of drug were very similar to those obtained if treated red blood cells were not washed after treatment. All these results suggest that red cells retained some quantities of drug. Our data highlight the potential effect of red cells interfering with platelet function inhibitors.

Macrosocial and environmental influences on minority health.

Ethnic minority populations show patterns of health, health care use, and mortality that differ from the overall U.S. population. Each of the broad groups of minorities (Asian Hispanic, Native, and African Americans) has a unique background of sociocultural factors that influence these patterns. Thus, the larger social environment for ethnic populations, including political, environmental, historical, and economic factors, is a major variable in possible health outcomes. The individual portions in this panel report of the conference seek to identify such factors for each ethnic group and to suggest those macrosocial influences that are most important for observed health effects.

Massive calcification of the left atrium: surgical implications.

BACKGROUND: Massive calcification of the atrial walls ("porcelain atrium") is a rare condition that usually has been reported as an incidental radiologic findings. METHODS: Between January 1988 and June 1993, 971 patients underwent valvular operation at our institution; 21 patients showed extensive calcification of the left atrium. In 8 patients the calcification was massive, involving almost all the atrial surface. The diagnoses were established by radiology and were confirmed at operation. The mean age of these patients (4 men, 4 women) was 55 +/- 9.6 years. All had rheumatic valve disease, were on atrial fibrillation, and had undergone at least one operation previously. Pulmonary artery pressure was severely increased, even up to systemic levels, in all patients except 1. Total endoatriectomy of the left atrium and mitral valve replacement were performed. No patient was lost during the follow-up. RESULTS: Hospital mortality rate was 12.5% (1 patient) and 2 patients died in the late postoperative period. None of these deaths are attributable to the surgical procedure. CONCLUSIONS: In toto endoatriectomy of a massively calcified atrium is an easy to perform technique that helps to replace the mitral valve and close the atrial wall.

[Expression of von Willebrand's disease in endothelial cord cell from a type 1 patient. Discrepancies between clinical manifestations and laboratory tests]. / Expresión de la enfermedad von Willebrand en células endoteliales de cordón umbilical de una paciente tipo I. Discrepancias entre pruebas de laboratorio y manifestación clínica.

PURPOSE: The reactivity of subendothelium generated by endothelial cells attained from the umbilical cord of a newborn girl from a patient with type I von Willebrand's disease was evaluated. MATERIAL AND METHODS: Platelet adhesiveness was assessed by means of "ex vivo" blood perfusion systems (shearing coefficients from 300 to 1,300 s-1), on umbilical artery subendothelium and over the extracellular matrix (ECM) generated by cultured endothelial cells attained from the umbilical cord of a newborn baby from a type I von Willebrand mother. RESULTS: By means of an ELISA technique, a significant reduction of both the vWF secreted into the culture (p < 0.05) and of that associated with ECM (p < 0.05) was noticed. The two subendothelial surfaces examined supported a lesser extent of platelet adhesion than the control surfaces from healthy individuals in the perfusion tests at 1,300 s-1 (p < 0.05). The experimental results did not agree with the lack of clinical manifestations and laboratory abnormalities in the propositus at age 3. CONCLUSIONS: These findings suggest that the endothelial cells cultured from the tissues of a newborn baby from a type I von Willebrand woman expressed less vWF, at the same time confirming the importance of vWF bound to connective tissue in sustaining platelet adhesion. The data attained here illustrate the complex model of inheritance of moderate von Willebrand's disease, along with the technical limitations of cell culture studies. Such observations must be borne in mind whenever any experimental approach is performed with material attained from ill-differentiated tissues such as the umbilical cord vein.

Thoracic aneurysm as a cause of chyluria: resolution by surgical treatment.

A 37-year-old man who had suffered a thoracic trauma presented night release of whitish urine 2 years later. Thoracic computed tomography and aortography demonstrated an aneurysm of the thoracic aorta. Lymphography confirmed the compression of the thoracic duct by the aneurysm. After surgical repair the patient has remained asymptomatic.

Cardiac surgery in patients under chronic hemodialysis.

A total of 15 chronic renal failure patients on hemodialysis therapy underwent some kind of cardiovascular surgery between August 1984 and March 1993. Ten had a valve abnormality, and the remaining five had coronary artery disease. All of them were hemodialyzed the day before surgery and 24-48 h after the operation. Eleven recovered well after surgery, four died of septic shock: two of these were in septic shock prior to surgery; one was in acute congestive heart failure, and one was operated during an acute myocardial infarction. All operative deaths occurred in the patients who underwent non-elective surgery or were preoperatively in New Heart Association (NYHA) class IV. The factors having an impact on morbidity and mortality seem to be more related to the previous clinical situation and to the urgency of the operation than to the status of chronic renal failure. An early and adequate assessment of the candidates, when possible avoiding emergency surgery and acute left ventricular dysfunction, as well as careful management during cardiopulmonary bypass procedures (CPB) and the immediate post-surgical period will certainly improve the result of cardiac surgery in these patients, making it similar to those who are not in chronic renal failure.

[The contribution and usefulness of routine intraoperative transesophageal echocardiography in cardiac surgery. An analysis of 130 consecutive cases]. / Contributo e rentabilidade da ecocardiografia transesofágica intraoperatória de rotina em cirurgia cardíaca. Análise de 130 casos consecutivos.

PURPOSE: To assess the value of routine intraoperative transesophageal echocardiography (TEE) in unselected patients (P) undergoing cardiac surgery. DESIGN: Routine intraoperative TEE in unselected patients undergoing cardiac surgery and evaluation of its usefulness and contribute to a successful surgery. PATIENTS: In-hospital patients from cardiology, cardiac surgery and intensive care departments of a general hospital classified as a reference medical centre in cardiovascular pathology. MATERIAL AND METHODS: From February 1994 to May 1994 an intraoperative TEE was routinely performed in patients undergoing cardiac surgery. A total of 130 TEE studies were made corresponding to 128 patients, 69 males and 61 females, with a mean age of 49.4 +/- 12.1 years. Indications for surgery were as following: a) Coronary artery bypass grafting (C.A.B.G.)-39; b) Valvular surgery-76; c) C.A.B.G. and valvular surgery-5; d) Thoracic aorta pathology associated or not to aortic valve surgery and/or coronary arteries re-implantation-6; e) Other-4. TEE performed using either a monoplane, biplane or multiplane probe and the images acquisition was made before thoracotomy and cardiopulmonary bypass (CPB) and after CPB with hemodynamic stabilization. RESULTS: Pre CPB imaging yielded unsuspected findings in 11 P (8.5%) that changed the planned surgery in 7 cases (5.4%). Post CPB echo study, which was performed after hemodynamic stabilization, modified the surgical strategy in 13 cases (10.9%) avoiding 1 predetermined surgical procedure (tricuspid ring annuloplasty) and a new surgery in another case, leading to a 3 non-predetermined surgical procedures (by showing significative tricuspid regurgitation), to a further surgery in the same valve in 6 patients (mitral paravalvular leak with significative regurgitation in 1P, another mitral prosthesis dysfunction in 1P, residual mitral valve insufficiency after mitral valve repair in 3 P and aortic prosthesis dysfunction in 1 P), to a intraaortic counterpulsation balloon device in 1 P and to new CPB due to an insufficient extraction of calcified pericardium in one case of constrictive pericarditis. In 23 cases (17.7%) TEE has modified the anesthetic procedure by demonstrating signs of hemodynamic changes before Swan-Ganz catheter, thus prompting changes in the administrations of fluids and either in inotropic or vasodilator agents. In total, intraoperative TEE has changed the surgical and/or anesthetic plan in 43 cases (33.0%). There was no difficulties or complications related to the procedure. CONCLUSION: These data indicate that intraoperative TEE is useful in formulating the surgical plan and assessing immediate operative results as well as a guide to anesthetic procedures. Its high rentabillity in modifying the surgical and/or anesthetic plans lead us to believe that it must be used as a routine procedure in patients undergoing cardiac surgery.

Influence of co-incubation and cell number of platelets and polymorphonuclear leukocytes in cellular inhibition and activation phenomena.

Evidence indicates that complex interactions occur between blood platelets and polymorphonuclear leukocytes (PMN) referring to both activation and inhibition phenomena. We studied the influence of co-incubating activated PMN and platelets at varying cell counts in the production of two active metabolites, thromboxane A2 (TxA2) measured as thromboxane B2 (TxB2) and platelet activating factor (PAF). The decrease observed in the quantity of TxA2 synthesized by 2 x 10(8) platelets/ml in the presence of physiological PMN counts clearly indicates an inhibitory effect of PMN in AA-derived metabolites. This suggests there is an influence of PMN-released products on activated platelets, decreasing their capacity to synthesize TxA2. Moreover, we found that the addition of platelets, which do not make measurable quantities of PAF, to PMN suspensions significantly decreased the capacity of PMN to synthesize this mediator. Together with this inhibiting action we also observed an activating effect, in such a way that the more PMN were added to platelet suspensions the more TxA2 was produced. Conversely, the maximal amounts of PAF were synthesized when the highest platelet count suspensions were added to PMN. In summary, the results we present here clearly show cellular interactions between platelets and PMN that directly influence the amounts of metabolites synthesized by both cells.

[Potentiation of the antiplatelet effect of dipyridamole and aspirin by erythrocytes. Study under flow conditions]. / Potenciación del efecto antiplaquetario del dipiridamol y la aspirina por los eritrocitos. Estudio bajo condiciones de flujo.

PURPOSE: To assess, by means of a morphometric method, the interaction of platelets with subendothelium, as induced by perfusion with the Baumgartner system, and to compare the antiplatelet effect of acetylsalicylic acid (ASA) and dipyridamole (DIP) and the combination of both drugs. MATERIAL AND METHODS: Blood samples were drawn from healthy volunteers and platelet-rich plasma specimens were prepared at a concentration of 4 x 10(8)/mL. Abdominal aorta segments were obtained from New Zealand rabbits, they being deprived of endothelium by alpha-chymotrypsin. Red cells and platelets were separately or conjointly treated on reconstituted whole blood using ASA and DIP at therapeutic doses, separately or in association. Perfusion experiences were carried out in Baumgartner's annular chamber. Upon finishing the studies, the aorta segments were morphometrically evaluated by an optic analysis system attached to a computer with an automatic image recognition programme. The statistical analysis was performed with Student's t test, differences between groups of p < 0.05 being assigned significance. RESULTS: Treatment with the association ASA-DIP was the only one to significantly reduce interaction, as both the size of aggregates and the extent of the covered surface decreased when whole blood was treated, and only the covered surface did when red cells were separately treated. When treating only platelets, the reduction of aggregates had no significance. CONCLUSION: The synergism of ASA and DIP in antiplatelet therapy was confirmed, as well as the important enhancing effect exerted by red cells.

Platelets lacking functional CD36 (glycoprotein IV) show reduced adhesion to collagen in flowing whole blood.

A parallel-plate perfusion chamber has been used to evaluate the contribution of the adhesive membrane glycoprotein CD36 (GPIV) to platelet adhesion on type I collagen in flowing whole blood at a shear rate of 800 s-1. In one series of experiments, reconstituted normal blood (hematocrit 0.4; platelet count 1.5 x 10(5)/microL) was prepared from washed red blood cells, plasma, and washed platelets that had been incubated with Fab fragments of a monospecific polyclonal anti-CD36 antibody (50 micrograms/mL, 30 minutes, 37 degrees C). Percent surface coverage of collagen-coated coverslips using reconstituted blood with antibody-blocked platelets, as compared with paired reconstituted controls (100%), was 50% at 2 minutes, 87% at 5 minutes, and 90% at 10 minutes. Further studies were performed by perfusion of whole blood from a healthy donor of the Naka-negative phenotype, whose platelets constitutively lack CD36, over collagen-coated coverslips. In this case, percent surface coverage was 55% of normal controls at 2 minutes, 76% of controls at 5 minutes, and 72% of controls at 10 minutes. In both preparations, platelets lacking functional CD36 had a statistically significant decrease (P < .005) in adhesion after 2 minutes and 10 minutes perfusion but not at 5 minutes. These results show that functional CD36 facilitates the rapid adhesion of platelets to collagen and that this effect is seen at the earliest time points of their interaction.

Interleukin 1-induced cancer cell/endothelial cell adhesion in vitro and its relationship to metastasis in vivo: role of vessel wall 13-HODE synthesis and integrin expression.

Previously, we have demonstrated that stimulation of endothelial cells (ECs) with interleukin-1 alpha (IL-1 alpha) enhances the synthesis and expression of the vitronectin receptor (VnR), promotes VnR-dependent adhesion of human A549 adenocarcinoma cells to ECs, and is associated with decreased EC 13-hydroxyoctadecadienoic acid (13-HODE) synthesis in vitro. To determine whether these observations are relevant in vivo, we examined the acute retention and subsequent metastasis of intravenously-injected B16F10 melanoma cells in murine lungs, in relation to vessel wall 13-HODE. In C57BL/6 mice pretreated with IL-1 alpha, vessel wall 13-HODE was decreased and B16F10 lung entrapment and metastasis were increased. The latter two events were blocked by pretreating the animals with the GRGDS peptide. These data suggest a relationship between vessel wall 13-HODE synthesis, adhesion molecule expression, and adhesion of B16F10 cells to the endothelium.

[Effect of PAF (platelet-activating factor) on hemostasis. Studies on endothelial cells and platelets]. / Influencia del PAF (factor activador de las plaquetas) en la hemostasia. Estudios en células endoteliales y plaquetas.

PURPOSE: To evaluate the direct action of PAF on the pro-coagulant activity of cultured vascular endothelial cells; to analyse by photometric methods the thrombogenic effect of PAF on platelets, and to assess platelet deposition on vascular endothelium. MATERIAL AND METHODS: Human endothelial cells were isolated from umbilical cord vein and incubated for three minutes at 22 degrees C with different PAF concentrations (10(9) M to 10(-7) M) in order to assess the influence of this lipidic mediator on the procoagulant activity of the cells. The effect of PAF on platelet aggregation was assessed by aggregation studies using arachidonic acid (AA) and different PAF and Lyso-PAF concentrations (10(-8) M to 10(-4) M). Serotonin (5-HT) release was tested in platelet rich plasma (PRP) samples highly sensitive to PAF. PRP samples were incubated for 30 minutes at 22 degrees C with 100 microCi 3H-5-HT. Platelets were activated with 10(-7) M to 10(-9) M PAF concentrations, the percentage of 3H-5-HT released into the extra-platelet medium being calculated. Baumgartner's continuous perfusion model was used to study platelet deposition on the vascular endothelium. The morphometric evaluation was carried out by a planimeter assembled to a data processor with a programme devised for analysing the platelet-subendothelium interaction. RESULTS: Evaluation of the procoagulant activity on the cell surface: The expression of the procoagulant activity showed no variations with respect to the controls under different concentrations of PAF. Platelet aggregation and release studies: Normal values of platelet aggregation (80% to 100%) were found when using AA, however, there were great case to case variations under different PAF concentrations. Serotonin release was less marked than aggregation itself. The use of Lyso-PAF failed to elicit platelet aggregation and serotonin release in any case. Morphometric evaluation: The results attained showed that perfusion carried out with 10(-8) M PAF concentration showed contact, adhesiveness and thrombus formation figures similar to those of control perfusion. CONCLUSIONS: Human platelets are not too sensitive to PAF activity, only high PAF concentrations being capable of inducing platelet aggregation and 5-HT release with ample variability. This suggests the existence of a heterogeneous platelet population with PAF receptors. Low PAF concentrations do not modify the haemostatic function, and only those PAF concentrations inducing maximal release and aggregations could reduce the interaction of platelets with vascular subendothelium and the formation of thrombi.

Platelet adhesivity to subendothelium is influenced by polymorphonuclear leukocytes: studies with aspirin and salicylate.

Interactions between blood platelets and polymorphonuclear leukocytes (PMN) influence cell reactivity. We have examined the effects of inhibiting platelet and PMN cyclooxygenase and lipoxygenase pathways, by treatment with aspirin (ASA) and salicylate (SAL) on platelet-vessel wall interaction studied under flow conditions by means of an annular chamber perfusion system. We have also measured the levels of cyclooxygenase-derived metabolites during perfusion. Perfusates were prepared with untreated and ASA- or SAL-treated PMN or platelets. Our results demonstrated that blockage of the lipoxygenase pathway in PMN significantly increased platelet thrombus formation and favored the production of thromboxane B2 (TxB2) during perfusion, whereas inhibition of cyclooxygenase pathway in PMN had no effect either on platelet deposition or on TxB2 levels. In contrast, blockage of platelet cyclooxygenase, which caused almost total inhibition of TxB2, enhanced platelet adhesion and did not modify platelet thrombus formation. These results suggest that under dynamic conditions cooperative metabolic mechanisms between platelets and PMN directly influence platelet interaction with vascular subendothelium.

[The effect of low-dose acetylsalicylic acid on platelet aggregation parameters in vitro]. / Efecto del ácido acetilsalicílico a dosis bajas sobre los parámetros de agregación plaquetaria in vitro.

In order to elucidate whether a single dose of 150 mg acetylsalicylic acid three times a day, provokes significant changes into platelet aggregation, we analyzed a group of 50 patients who underwent coronary revascularization. During 48 hours before surgery, all patients received 100 mg dipyridamole orally every 6 hours and 1 hour after the end of the operation 100 mg dipyridamole via nasogastric tube. Patients were then randomized into three groups to receive 3 times a day a capsule containing: 50 mg acetylsalicylic acid, 50 mg acetylsalicylic acid plus 75 mg dipyridamole or placebo. Before the antiplatelet therapy was started, the day of the operation and 5 days after the onset of the treatment, blood samples were taken to determine platelet aggregation (turbidimetric technique) and the thromboxane A2 liberation. The three groups were comparable for all the studied clinical and angiographic variables. Preoperative dipyridamole did not provoke significant changes in platelet aggregation (acetylsalicylic acid group 86.5 +/- 10% vs 71 +/- 28.8%; acetylsalicylic acid + dipyridamole group 81.5 +/- 7.8% vs 75.3 +/- 22.7%; placebo group 83.7 +/- 8.9% vs 70 +/- 21.5%). After 5 days of treatment with acetylsalicylic acid, both groups under active treatment showed a significant (p less than 0.001) decrease of aggregability (acetylsalicylic acid 12.8 +/- 4.4%; acetylsalicylic acid + dipyridamole 20.5 +/- 17%; placebo 72 +/- 21.5%).(ABSTRACT TRUNCATED AT 250 WORDS)