New concepts regarding events that lead to myocardial infarction

Characterization of an original model of myocardial infarction provoked by coronary artery thrombosis induced by ferric chloride in pig

BACKGROUND

Great advances have been made in the prevention of thrombotic disorders by developments of new pharmacological and surgical treatments. Animal models of arterial thrombosis have largely contributed to the discovery and to the validation of original treatments. The purpose of the present work was to develop and validate an original model of acute myocardial infarction provoked in pig by thrombosis of the left anterior descending (LAD) coronary artery induced by topical application of ferric chloride solution.

METHODS AND RESULTS

Myocardial infarction, resulting from an occlusive and adherent mixed thrombus formed in the LAD coronary artery, was examined at macroscopic level using dual staining technique (Evans blue dye; triphenyltetrazolium chloride) and at microscopic level using conventional histological analyses and immunohistochemical detection of desmin. Biochemical markers (troponin T and ATP), platelet reactivity and standard hemodynamic parameters (such as stroke volume, ejection fraction, stroke work and cardiac output) have also been evaluated. From these analyses, it was demonstrated that each pig developed a transmural area of irreversible damage mainly located in the anteroseptal region of the left ventricle. The more progressive development of coronary artery occlusion, as compared to an abrupt ligation, was accompanied by a correspondingly progressive impairment in hemodynamics.

CONCLUSION

We conclude that this original porcine model of myocardial infarction is quite close to clinical pathophysiological conditions, such as thrombus formation occurring after atherosclerotic plaque rupture. This certainly constitutes a further argument in favour of this model to assess pharmaceutical or mechanical support of an acutely ischemic heart.

The flow cytometer model markedly affects measurement of ex vivo whole blood platelet-bound P-selectin expression in patients with chest pain: are we comparing apples with oranges

Surface expression of P-selectin is known to be a marker of platelet activation in patients with acute coronary syndromes. However, direct comparisons of flow cytometer data may be obscured by differences in methodology, artifactual platelet activation during washing procedures, choice of antibodies, absence of control measurements, and possible observer bias due to unblinded data collection. We sought to test the hypothesis that the model of flow cytometer represents another variable affecting P-selectin measurements. Platelet P-selectin in whole blood was measured by FACScan (Becton Dickinson, Inc., San Diego, CA, USA) or EPICS XL (Coulter Corporation, Hialeah, FL, USA) flow cytometry in 338 patients presenting with chest pain to the emergency departments of three community hospitals as part of a multicenter diagnostic trial. Platelet expression of P-selectin (% of cell positivity) was consistently higher for each discharge diagnosis when measured with FACScan flow cytometer (13.2+/-4.1 for myocardial infarction, 10.0+/-3.6 for unstable angina, 9.9+/-3.5 for heart failure, 4.7+/-0.1 for gastrointestinal illness, and 6.3+/-0.7 for patients with noncardiac chest pain) when compared with results obtained from the EPICS XL instrument (2.4+/-0.2, 2.5+/-0.2, 2.5+/-0.1, 1.8+/-0.1, and 2.3+/-0.1 respectively, p=0.0001 for all groups). This study reveals marked discrepancies in the level of platelet P-selectin measurement based exclusively on the model of flow cytometer used. If P-selectin is to become a diagnostic tool for differentiating an etiology of chest pain, standardized measurements must be defined for each model of flow cytometer.

Plasma thromboxane and prostacyclin are linear related and increased in patients presenting with acute myocardial infarction

The role of prostanoids in patients with ischemic heart disease including acute myocardial infarction (AMI) has been recognized. However, there is very limited knowledge of the baseline TXB2 and 6-keto-PGF1a plasma levels in patients with AMI before therapy has been administered. We compared plasma levels of TXB2 and 6-keto-PGF1a by enzyme immunoassay in 18 AMI patients before thrombolysis, with those of 13 healthy controls. Plasma levels of TXB2 (319.78+/-16.50 pg/ml) and 6-keto-PGF1a (536.72+/-56.71 pg/ml) were heterogeneous, but significantly higher in the AMI patients than in controls (175.92+/-17.29 pg/ml and 192.08+/-26.11 pg/ml, respectively). In some patients, long-term aspirin therapy mildly inhibits baseline prostanoid levels, however, limited data prevents us from further speculations on this issue. Although, the contributions by prostanoids to the pathogenesis of AMI have been well proposed, their plasma concentrations are not uniformly elevated, and it is still unclear whether the resultant changes are indicative of clinically meaningful effects.

Carotene, tocopherol, and ascorbate contents in subspecies of Brassica oleracea

Cruciferous vegetables contain high levels of vitamins that can act as antioxidants, compounds that may protect against several degenerative diseases. The edible portions of 50 broccoli and 13 cabbage, kale, cauliflower, and Brussels sprouts accessions were assayed to determine variation in alpha-carotene, beta-carotene, alpha-tocopherol, gamma-tocopherol, and ascorbate contents within and between subspecies of Brassica oleracea. Ascorbate content was estimated in fresh samples using HPLC. Tissues for carotene and tocopherol analysis were lyophilized prior to extraction. Carotene and tocopherol concentrations were simultaneously measured using a reverse phase HPLC system. Results indicate that there is substantial variation both within and between subspecies. Kale had the highest levels of vitamins, followed by broccoli and Brussels sprouts with intermediate levels and then by cabbage and cauliflower, with comparatively low concentrations. Variability in vitamin content among the broccoli accessions suggests that potential health benefits that accrue with consumption are genotype dependent.

Vitamin E and human health: rationale for determining recommended intake levels

The recent literature provides strong evidence that vitamin E intakes much higher than the current recommendations can contribute to and/or improve human health. In fact, the available data indicate that at higher-than-current recommended intake levels, vitamin E affects several functions related to human health. For example, Vitamin E is required to protect polyunsaturated fatty acids (PUFAs) against auto-oxidation. The amount of vitamin E needed to protect PUFAs against oxidative damage is at least 0.4-0.8 mg vitamin E per gram PUFAs and may be in excess of 1.5 mg/g when diets contain higher-than-average levels of long-chain PUFAs. Based upon studies of vitamin E kinetics and metabolism, a daily vitamin E intake of 135-150 IU is suggested. Important functions such as protection against oxidative damage, immune response, and the propensity of platelets to adhere to the vessel wall are related to vitamin E intakes. Vitamin E intake of 40 IU/d was the least amount demonstrated to inhibit low-density lipoprotein oxidation; a dose-dependent effect was seen up to 800 IU/d. Vitamin E intakes of at least 60 IU/d enhanced immune responses and intakes of 200 IU-400 IU/d decreased platelet adhesion to the vessel wall. Based upon the effects of modulating these functions, it is hypothesized that vitamin E plays a pivotal role in the prevention of cardiovascular diseases. Indeed, many observational studies have reported vitamin E to reduce the risk of cardiovascular disease. Recent intervention studies corroborate these findings. Of equal importance, there is a solid body of literature that demonstrates that these and much higher vitamin E intakes are safe.