Jean-Gilles Latour

Aspirin, heparin, or both to treat acute unstable angina

We tested the usefulness of aspirin (325 mg twice daily), heparin (1000 units per hour by intravenous infusion), and a combination of the two in the early management of acute unstable angina pectoris in a double-blind, randomized, placebo-controlled trial involving 479 patients. The patients entered the study as soon as possible after hospital admission (at a mean [+/- SD] of 7.9 +/- 8.0 hours after the last episode of pain), and the study was ended after 6 +/- 3 days, when definitive therapy had been selected. Major end points--refractory angina, myocardial infarction, and death--occurred in 23, 12, and 1.7 percent of the 118 patients receiving placebo, respectively. Heparin was associated with a decrease in the occurrence of refractory angina (P = 0.002). The incidence of myocardial infarction was significantly reduced in the groups receiving aspirin (3 percent; P = 0.01), heparin (0.8 percent; P less than 0.001), and aspirin plus heparin (1.6 percent, P = 0.003), and no deaths occurred in these groups. There were too few deaths overall to permit evaluation of the effect of treatment on this end point. The combination of aspirin and heparin had no greater protective effect than heparin alone but was associated with slightly more serious bleeding (3.3 vs. 1.7 percent). We conclude that in the acute phase of unstable angina, either aspirin or heparin treatment is associated with a reduced incidence of myocardial infarction, and there is a trend favoring heparin over aspirin. Heparin treatment is also associated with a reduced incidence of refractory angina.

The low molecular weight heparin, enoxaparin, limits infarct size at reperfusion in the dog

OBJECTIVEnHeparin (HEP) is used in the post-thrombolytic state to prevent vessel reocclusion, thereby aiding myocardial salvage. Side effects limit its benefits, but besides anticoagulant activity HEP has diffuse actions that may be potentially beneficial to jeopardized reperfused myocardium. This study compares the effect of therapeutic doses of HEP and enoxaparin (ENOX), a low molecular weight heparin, and to streptokinase (SK), on infarct size.nnnMETHODSnThe left anterior descending coronary artery was occluded in dogs for 90 min, followed by 6 h of reperfusion with a residual critical stenosis in place. Five min before reperfusion, HEP (2800 IU) was injected i.v., and perfused at 500 IU/h until sacrifice in group 2, while groups 3 and 4 received ENOX (2128 anti-Xa IU i.v.) followed by 380 anti-Xa IU/h. Group 4 was also given 500,000 IU SK over 30 min before reperfusion beginning at 55 min of occlusion (ENOX + SK), while group 5 received only SK. Controls (CON, group 1) received saline. P-selectin mediated platelet-neutrophil rosettes formation was also tested in vitro in the presence of HEP and ENOX.nnnRESULTSnThe area at risk delimited by dye perfusion was statistically similar among groups. Covariance analysis between infarct size (% of area at risk) delimited with triphenyltetrazolium and collateral flow measured with radioactive microspheres confirmed that groups given ENOX (21.6 +/- 5.5%) and ENOX + SK (24.9 +/- 3.9%) developed smaller infarcts (P < 0.05) than CON (48.1 +/- 4.5%), as opposed to HEP (32.2 +/- 3.6%) and SK (46.8 +/- 3.4%) groups. 111In-platelet counts in the infarct were reduced significantly by 64% in the ENOX group as compared to CON, and to a lesser extent (42%, n.s.) in the ENOX + SK group, but were not reduced by HEP and SK treatments. Neutrophil accumulation in the infarcts was decreased significantly and by more than 75% in the ENOX and ENOX + SK groups versus CON, but not in the HEP and SK groups. Also, only ENOX (10-100 micrograms/ml) significantly inhibited platelet-neutrophil rosettes formation in a plasmatic milieu.nnnCONCLUSIONSnThe ENOX treatment, as opposed to that of HEP, reduces myocardial platelet and neutrophil accumulations, and limits infarct size when given just before and during reperfusion. The benefits of ENOX on infarct size were not modified by SK, and may be related, at least in part, to an interaction with P-selectin-mediated cell adhesion.

Importance of Platelets in Neutrophil Adhesion and Vasoconstriction After Deep Carotid Arterial Injury by Angioplasty in Pigs

In previous studies we have shown that platelets can support neutrophil adhesion to the injured vessel wall in vitro and that neutrophils contribute to vascular tone regulation after arterial injury in vivo. In this study, we investigated the implication of platelets in neutrophil adhesion and the vasomotor response to arterial injury in vivo. 111In-labeled neutrophil adhesion and angiographic vasoconstriction were quantified after deep carotid arterial injury by balloon angioplasty in normal (n = 8), thrombocytopenic (n = 7), and aspirin-treated (2 mg/kg IV, n = 7) pigs. Thrombocytopenia was produced by a polyclonal antiplatelet serum that depleted circulating platelet count by 84% without influencing neutrophil count. In the control animals, neutrophil adhesion (x 10(4)/cm2) at the site of deep arterial injury averaged 26.8 +/- 4.0 and decreased significantly to 11.5 +/- 2.3 and 11.2 +/- 2.4 in the thrombocytopenic and aspirin groups, respectively. The degree of vasconstriction was also reduced significantly, from 55.5 +/- 3.8% in the control group to 31.4 +/- 6.2% after platelet depletion and to 23.6 +/- 4.5% in the aspirin-treated group. Neutrophil adhesion to intact noninjured adjacent arterial segments was low in all groups and was not affected by the antiplatelet serum or by aspirin. In in vitro superfusion flow chambers, neutrophil adhesion to damaged arterial segments increased in the presence of platelets in a concentration-dependent manner and was not influenced by the antiplatelet serum. This study demonstrates that platelets can modulate neutrophil adhesion to the deeply injured arterial wall and that both elements may influence the degree of postangioplasty vasoconstriction in vivo.

Selectin Blockade Reduces Neutrophil Interaction With Platelets at the Site of Deep Arterial Injury by Angioplasty in Pigs

The adhesion of neutrophils to damaged arterial surfaces is increased in the presence of platelets by a mechanism implicating platelet P-selectin. Such interactions may enhance thrombus formation and the vascular response to injury. In this study, we investigated the effects of a selectin blocker (CY-1503), an analogue of sialyl Lewisx, on platelet and neutrophil interactions after arterial injury produced by angioplasty in pigs.51Cr-platelet deposition and 111In-neutrophil adhesion were quantified on intact, mildly and deeply injured carotid arterial segments, produced by balloon dilation, in control (saline, n=8) and treated (CY-1503, 15 mg/kg IV, n=7) pigs. The hematological parameters, the aggregation of whole blood in response to adenosine diphosphate, and the activating clotting time, as well as the heart rate and mean arterial blood pressure, were similar among groups and were not influenced significantly by CY-1503. The level of platelet and neutrophil adhesion increased significantly with the severity of arterial injury but was not influenced by CY-1503 on intact and mildly injured arterial segments. However, at the site of deep arterial injury, CY-1503 treatment was associated with a 58% reduction (P<0.01) in neutrophil adhesion, from 446.7+/-72.6x10(3) neutrophils/cm2 in the control group to 186.8+/-38.7x10(3) neutrophils/cm2 in the CY-1503-treated group, whereas platelet deposition remained unchanged (43.4+/-15.6x10(6) platelets/cm2 versus 50.1+/-12.2x10(6) platelets/cm2 in the control group). In in vitro adhesion experiments, using isolated platelet and neutrophil suspensions, we found that CY-1503 interfered with the adhesion of neutrophils to damaged arterial surfaces only in the presence of platelets. In contact with thrombogenic arterial surfaces, adherent and activated platelets supports neutrophil adhesion at the site of deep injury by an adhesive interaction involving neutrophil sialyl Lewisx. The inhibitory effect of CY-1503 on neutrophil interaction with adherent platelets may be clinically relevant in patients undergoing percutaneous transluminal coronary angioplasty where platelet and neutrophil interactions may enhance the acute and chronic arterial response to injury.

Inhibition of platelet-neutrophil interactions by Fucoidan reduces adhesion and vasoconstriction after acute arterial injury by angioplasty in pigs.

The selectin family of cell-adhesion molecules contributes to the interactions of leukocytes and platelets at the site of vascular injury. Such interactions enhance inflammatory reactions and thrombus formation during the arterial response to injury. In this study, we investigated the effects of a selectin inhibitor (Fucoidan) on platelet and neutrophil interactions after arterial injury produced by angioplasty in pigs. [51Cr]-platelet deposition and [111In]-neutrophil adhesion were quantified on intact, mildly, and deeply injured carotid arterial segments, produced by balloon dilation in control (saline, n = 7) and Fucoidan-treated (i.v.; 1 mg/kg, n = 6; 5 mg/kg, n = 5) pigs. In the control group, platelet deposition (x10(6)/cm2) was influenced by the severity of injury and increased significantly (p < 0.05) from 0.06+/-0.06 on intact endothelium to 3.8+/-0.6 and 33.6+/-4.9 on mildly and deeply injured segments, respectively. Fucoidan, 1 mg/kg, had no significant effect, although doses of 5 mg/kg reduced platelet deposition by 73% on deeply injured segments. The level of neutrophil adhesion (x10(3)/cm2) was also influenced by the severity of injury: it increased in the control group from 8.8+/-2.5 on intact endothelium to 226.6+/-45.5 and 397.4+/-61.3 on mildly and deeply injured arterial segments, respectively (p < 0.05). Again, 1 mg/kg Fucoidan had no effect, although doses of 5 mg/kg reduced neutrophil adhesion by 92% and by 84% on mildly and deeply injured segments, respectively. The effects of Fucoidan were associated with a 51% decrease in the vasoconstrictive response at the site of arterial injury. However, Fucoidan had no significant effect on either platelet aggregation or activated clotting time (ACT). In the in vitro perfusion experiments, Fucoidan inhibited both isolated platelet, and neutrophil, adhesion to damaged arterial surfaces. This inhibition was more pronounced in experiments using mixed cell preparations, indicating that Fucoidan interferes with platelet and neutrophil interactions. These results highlight the importance of selectins in the acute physiopathologic reactions related to platelet-neutrophil interactions after arterial injury.

Myocardial distribution of retrograde cardioplegic solution assessed myocardial thallium 201 uptake

Perfusion of the right ventricular myocardium with retrograde infusion of cardioplegic solution through the coronary sinus has been reported to be less than optimal. To study left and right ventricular perfusion during retrograde and antegrade coronary sinus cardioplegia, we added 0.5 mCi of thallium 201 to 500 ml of hyperkaliemic crystalloid cardioplegic solution injected retrogradely into the coronary sinus at low perfusion pressure (20 to 40 mm Hg) in 14 dogs and antegradely in the ascending aorta in seven dogs. The cardioplegic solution was cold (4 degrees C) in eight animals perfused retrogradely and warm (21 degrees C) in 13 animals. After aortic crossclamping, the ascending aorta and the left and right ventricles were vented and cardioplegic solution was injected retrogradely into the coronary sinus. Antegrade injections were performed after aortic crossclamping and venting of the left and right ventricles and of the left and right atrium. After cardioplegic arrest, the heart was harvested, fixed, and scanned with a gamma camera. With cold retrograde cardioplegia, 82% +/- 5% of the injected thallium 201 activity was identified in the myocardium--71% +/- 9% for warm retrograde perfusion and 80% +/- 3% for antegrade perfusion (p > 0.05). Focal areas of hypoactivity in the septum and in the right ventricular free wall were present at scintigraphic imaging in all animals receiving retrograde perfusion. In conclusion, most thallium 201 activity of cardioplegic solution injected retrogradely in the coronary sinus was identified in the myocardium, but focal areas of hypoactivity in the septum and in the right ventricular free wall were present, indicating uneven distribution. Temperature of the crystalloid solution had no effect on the myocardial distribution of the thallium 201 radiotracer in the myocardium.

Hemodynamic, platelet and clinical responses to prostacyclin in unstable angina pectoris

The hemodynamic and platelet effects of prostacyclin (PGI2) were investigated in 27 patients with unstable angina (14 treated patients; 13 control subjects) given a 72-hour infusion (5 ng/kg/min) or placebo. This randomized study was double-blind and conducted as a substudy of a multicenter trial testing the clinical efficacy of PGI2. The clinical and angiographic features were identical in the 2 groups. Blood pressure and heart rate were not modified significantly by PGI2. A recurrence of angina during infusion occurred in 8 treated patients (57.1%) and in 8 control subjects (61.5%). Two patients receiving PGI2 and none in the control group developed a myocardial infarction. Levels of 6-keto-prostaglandin F1 alpha, a stable metabolite of PGI2, increased from baseline values (less than 20 pg/ml) to 605 +/- 41 pg/ml during infusion. Levels of fibrinopeptide A, beta-thromboglobulin, platelet factor 4, thromboxane B2 and the platelet aggregates ratio in blood were similar between the 2 groups before, during and after PGI2 infusion. Prostacyclin reduced ex vivo platelet aggregation to adenosine diphosphate and thromboxane B2 generation by approximately 50% during the infusion period with return of aggregation to baseline and platelet thromboxane B2 production to above baseline after the discontinuation of PGI2. Thus, despite favorable effects of PGI2 upon platelet aggregation and systemic hemodynamics, the prostanoid failed to improve the clinical evolution of unstable angina.

Intravenous aspirin at reperfusion does not reduce infarct size in the dog with a residual critical stenosis.

Platelet-related events being associated with the increment of infarct size at reperfusion in the presence of a residual stenosis, we tested in dogs whether intravenous aspirin (ASA) could limit infarct size. The left anterior descending coronary artery was occluded for 90 min and reperfused for 6 h in the presence of a residual critical stenosis. Controls received saline, and treated groups were given 2, 6, or 12 mg/kg ASA, i.v., 5 min before reperfusion. Infarct size did not differ significantly between groups (control, 43.80+/-6.28%; ASA, 2 mg/kg: 41.07+/-7.78%; ASA, 6 mg/kg: 37.55+/-3.44%; ASA, 12 mg/kg: 29.40+/-5.41%), as well as transmural collateral blood flow and [111In]-platelet accumulation in the infarcted myocardium (2.5-3.6 x 10(5) platelets/g). However, myocardial neutrophil accumulation was significantly reduced (p < 0.05) in groups given 6 (15.0+/-2.6 x 10(6)/g tissue) and 12 mg/kg (18.4 +/-3.8) ASA, but not in the 2-mg/kg group (21.0+/-5.2), as compared with control group (32.0+/-7.2). Ex vivo platelet aggregation to collagen was abolished during reperfusion in all treated groups (p < 0.05). Transcardiac arteriovenous differences in 6-keto-PGF1alpha were reduced significantly 1 h after reperfusion in groups given 6 or 12 mg/kg ASA (94.7+/-13.1 and 71.7+/-19.2 pg/ml, respectively) but not in the 2-mg/kg group (178.3+/-78.2 pg/ml), as compared with control (405.4+/-171.6 pg/ml). ASA-insensitive platelet activation at the site of stenosis or inhibition by ASA of prostacyclin production by jeopardized myocardium may explain the observed lack of benefit of ASA.

Sustained Myocardial Protection by Clentiazem (TA-3090) After a 90-Minute Coronary Occlusion and 72 Hours of Reperfusion in Dogs with Collateral Flow

Summary: Reduction of infarct size by calcium channel blockers, given at reperfusion, has been reported with diltiazem and clentiazem after 6 h of reperfusion following a 90-min coronary occlusion in the dog. The aims of the present study were to establish that the postischemic cardioprotection is not simply a delay in cell death, but a sustained or permanent myocardial salvage. Dogs with a 90-min occlusion of the left descending coronary artery underwent reperfusion for 72 h. Five minutes before reperfusion, they received, at random, i.v. saline (controls) or clentiazem (125 μg/kg i.v.), followed by infusion of 1 μg/kg/min, until sacrifice. Transmural collateral flow measured 15 min after occlusion with radioactive microspheres was not statistically different between groups [(means ± SE) control: 0.123 ± 0.040; treated: 0.150 ± 0.042 ml/min/g]. The area at risk (percentage of left ventricle), delimited by Evans blue perfusion was also similar (control: 39.9 ± 1.5%; treated: 42.4 ± 1.6%). Infarct size, estimated as percentage of the area at risk by triphenyltet-razolium chloride and histology, was reduced (p < 0.05) in treated dogs (control, 42.4 ± 4.7%; treated, 26.5 ± 5.4%) with collateral flow (≥ 0.02 ml/min/g), but not in those with virtually no (<0.02 ml/min/g) collateral flow (control, 62.0 ± 8.9%; treated, 72.7 ± 6.8%). Therefore clentiazem, at reperfusion after a 90-min ischemia, increases myocardial salvage limiting postischemic injury and providing sustained reduction of infarct size in dogs with collateral blood flow.

Ca2+-channel blockers and nucleoside triphosphate diphosphohydrolase (NTPDase) influence of diltiazem, nifedipine, and verapamil

The nucleoside triphosphate diphosphohydrolases (NTPDase; EC 3.6.1. 5) are a family of ectonucleotidases associated with vascular endothelial and smooth muscle cells. These ectonucleotidases are involved in the control of vascular tone by regulating the level of circulating ATP. Ca(2+)-channel blocking agents are currently used for the treatment of hypertension. Considering the external localization of the NTPDase catalytic site and its Ca(2+) requirement for enzyme activity, a possible interference of calcium antagonists (nifedipine, verapamil-HCl, and diltiazem-HCl and some of its metabolites) could be anticipated. To test that hypothesis, an NTPDase-enriched particulate fraction was used. Our results show that verapamil, diltiazem, and its metabolites all produced a concentration-dependent inhibition of NTPDase, at concentrations greater or equal to 0.1 mM with verapamil and to 0.5 mM with diltiazem and its metabolites, whereas no significant effect was observed with nifedipine. Kinetic studies, carried out to define the mode of action of these drugs, showed a mixed type of inhibition. Based on their respective K(i) values (in parentheses, in mM), inhibitory potencies of these molecules were in the following order: desacetyl-N-desmethyldiltiazem (M(2)-HCl; 0.6) > verapamil (0.76) > N-desmethyldiltiazem (M(A;) 0.9) > diltiazem (2.4) > desacetyl-O-desmethyldiltiazem (M(4)-HCl; 3.5) > desacetyl N, O-desmethyldiltiazem (M(6)-HCl; 3.9). Hence, these calcium antagonists can be considered as weak NTPDase inhibitors. Moreover, based on these K(i) values and the range of concentrations found in the blood, NTPDase would not be inhibited significantly in vivo.