Comparison of early microcirculatory and aortic changes in hypercholesterolemic rats

Clopidogrel or prasugrel reduces mortality and lessens cardiovascular damage from acute myocardial infarction in hypercholesterolemic male rats

AIMS

Hypercholesterolemia is a hazard for increasing susceptibility of the heart to myocardial infarction (MI) by inducing platelet hyperaggregability. Clopidogrel and prasugrel have documented cardioprotective effects in clinical studies. Herein, we investigated whether clopidogrel and prasugrel could protect against isoproterenol-induced acute MI (A-MI) under hypercholesterolemic conditions in rats.

MAIN METHODS

Dietary hypercholesterolemic rats were subjected to acute doses of isoproterenol. Serum lipids, inflammatory markers, aortic endothelin1 and endothelial nitric oxide synthase (eNOS) mRNAs expression and immunexpression of BCL2 were determined.

KEY FINDINGS

Hypercholesterolemic rats showed infiltration of inflammatory cells and reduction in aortic wall thickness, deposition of fibrous tissue between cardiac muscle fibers. Protective doses of prasugrel or clopidogrel for 28 days before A-MI increased survival, amended the ECG parameters -including ST segment elevation- and improved the histopathological picture in hypercholesterolemic rats. This was coupled with reductions in platelet aggregation, creatine kinase-MB activity, endothelin 1, systemic inflammation and cardiac lipid peroxidation and increment in aortic eNOS expression. Clopidogrel and prasugrel groups showed enhanced BCL2 expression in cardiac fibers and aortic wall.

SIGNIFICANCE

Prasugrel and clopidogrel protected against A-MI via anti-aggregatory and anti-inflammatory effects. These results add to the value of these drugs in correcting cardiovascular dysfunction in patients vulnerable to A-MI after confirmation by appropriate human studies.

5-HT causes splanchnic venodilation

Serotonin [5-hydroxytryptamine (5-HT)] causes relaxation of the isolated superior mesenteric vein, a splanchnic blood vessel, through activation of the 5-HT₇ receptor. As part of studies designed to identify the mechanism(s) through which chronic (≥24 h) infusion of 5-HT lowers blood pressure, we tested the hypothesis that 5-HT causes in vitro and in vivo splanchnic venodilation that is 5-HT₇ receptor dependent. In tissue baths for measurement of isometric contraction, the portal vein and abdominal inferior vena cava relaxed to 5-HT and the 5-HT_1/7 receptor agonist 5-carboxamidotryptamine; relaxation was abolished by the 5-HT₇ receptor antagonist SB-269970. Western blot analyses showed that the abdominal inferior vena cava and portal vein express 5-HT₇ receptor protein. In contrast, the thoracic vena cava, outside the splanchnic circulation, did not relax to serotonergic agonists and exhibited minimal expression of the 5-HT₇ receptor. Male Sprague-Dawley rats with chronically implanted radiotelemetry transmitters underwent repeated ultrasound imaging of abdominal vessels. After baseline imaging, minipumps containing vehicle (saline) or 5-HT (25 μg·kg^-1·min^-1) were implanted. Twenty-four hours later, venous diameters were increased in rats with 5-HT-infusion (percent increase from baseline: superior mesenteric vein, 17.5 ± 1.9; portal vein, 17.7 ± 1.8; and abdominal inferior vena cava, 46.9 ± 8.0) while arterial pressure was decreased (~13 mmHg). Measures returned to baseline after infusion termination. In a separate group of animals, treatment with SB-269970 (3 mg/kg iv) prevented the splanchnic venodilation and fall in blood pressure during 24 h of 5-HT infusion. Thus, 5-HT causes 5-HT₇ receptor-dependent splanchnic venous dilation associated with a fall in blood pressure.NEW & NOTEWORTHY This research is noteworthy because it combines and links, through the 5-HT₇ receptor, an in vitro observation (venorelaxation) with in vivo events (venodilation and fall in blood pressure). This supports the idea that splanchnic venodilation plays a role in blood pressure regulation.

Oh, the places you'll go! My many colored serotonin (apologies to Dr. Seuss)

Serotonin [5-hydroxytryptamine (5-HT)] has a truly fascinating history in the cardiovascular world. Discovered in the blood, 5-HT has long been appropriately regarded as a vasoconstrictor. A multitude of in vitro studies of isolated vessels support that addition of 5-HT causes vascular contraction. In only a few cases was 5-HT a vasodilator. Moreover, the potency and threshold of 5-HT causing contraction is increased in arteries from hypertensive vs. normotensive subjects, both animal and human. As such, we and others have hypothesized that 5-HT would contribute to hypertension by elevating arterial tone. In stark contrast to these decades of findings, we observed that a chronic infusion of 5-HT into conscious rats caused a reduction in blood pressure and nearly normalized blood pressure of experimentally hypertensive rats. Going back to the early work of Irvine Page, one of the scientists who discovered 5-HT, reveals an early recognized but never understood ability of 5-HT to reduce systemic blood pressure. Our laboratory, in collaboration with colleagues around the world, has dedicated itself to understanding the mechanisms of 5-HT-induced reduction in blood pressure. This manuscript takes you through a brief history of the discovery of 5-HT, in vitro serotonergic pharmacology of blood vessels, in vivo work with 5-HT and our studies that suggests the venous vasculature, potentially in combination with small arterioles, may be important to the actions of 5-HT in reducing blood pressure. 5-HT has certainly ended up in a place I never expected it to go.

PPAR-γ activator induces neuroprotection in hypercholesterolemic rats subjected to global cerebral ischemia/reperfusion injury: in vivo and in vitro inhibition of oxidative stress

Hypercholesterolemia (HC) and aging combine to increase the incidence of cerebrovascular disease through oxidative stress. Our investigation examined the effects of diet-induced hypercholesterolemia (2% for 8weeks) on the extent of brain injury in response to global cerebral ischemia/reperfusion (GCI/R) and the neuroprotective potentials of rosiglitazone in relation to oxidative stress. HC exacerbated the decline in the brain levels of GSH and the increase in MPO, proinflammatory markers and hippocampal lesions in response to GCI/R. HC rats receiving rosiglitazone, PPAR-γ agonist, demonstrated preservation of cell viability of CA1 hippocampal region and attenuation of brain edema. They also showed elevated levels of GSH and low levels of the other parameters similar to non-HC rats subjected to GCI/R. In vitro, rosiglitazone dose-dependently inhibited ROS generation by neutrophils. The results suggest exacerbation of brain lesions by HC in response to GCI/R. The neuroprotective therapeutic potentials of rosiglitazone are comparable to non-HC animals. Mechanisms of protection are possibly due to anti-oxidant, anti-inflammatory effects and scavenging properties of rosiglitazone. These results add to the beneficial therapeutic effects of rosiglitazone and its significance for age-associated diseases including hypercholesterolemia.

Statin and resveratrol in combination induces cardioprotection against myocardial infarction in hypercholesterolemic rat

Hypercholesterolemia (HC) is a common health problem that significantly increases risk of cardiovascular disease. Both statin (S) and resveratrol (R) demonstrated cardioprotection through nitric oxide-dependent mechanism. Therefore, the present study was undertaken to determine whether combination therapy with statin and resveratrol is more cardioprotective than individual treatment groups in ischemic rat heart model. The rats were fed with 2% high cholesterol diet and after 8 weeks of high cholesterol diet the animals were treated with statin (1 mg/kg bw/day) and resveratrol (20 mg/kg bw/day) for 2 weeks. The rats were assigned to: (1) Control (C), (2) HC, (3) HCR, (4) HCS and (5) HCRS. The hearts, subjected to 30-min global ischemia followed by 120-min reperfusion were used as experimental model. The left ventricular functional recovery (+dp/dt(max)) was found to be significantly better in the HCRS (1926+/-43), HCR (1556+/-65) and HCS (1635+/-40) compared to HC group (1127+/-16). The infarct sizes in the HCRS, HCS and HCR groups were 37+/-3.6, 43+/-3.3 and 44+/-4.2 respectively compared to 53+/-4.6 in HC. The lipid level was found to be decreased in all the treatment groups when compared to HC more significantly in HCS and HCRS groups when compared to HCR. Increased phosphorylation of Akt and eNOS was also observed in all the treatment groups resulting in decreased extent of cardiomyocyte apoptosis but the extent of reduction in apoptosis was more significant in HCRS group compared to all other groups. In vivo rat myocardial infarction (MI) model subjected to 1 week of permanent left descending coronary artery (LAD) occlusion documented increased capillary density in HCR and HCRS treated group when compared to HCS treatment group. We also documented increased beta-catenin translocation and increased VEGF mRNA expression in all treatment groups. Thus, we conclude that the acute as well as chronic protection afforded by combination treatment with statin and resveratrol may be due to pro-angiogenic, anti-hyperlipidemic and anti-apoptotic effects and long-term effects may be caused by increased neo-vascularization of the MI zone leading to less ventricular remodeling.

Effect of hypercholesterolemia on experimental colonic anastomotic wound healing in rats

AIM: To evaluate the mechanical and biochemical parameters of colonic anastomotic healing in hypercholesterolemic rats.

METHODS: Sixty rats were divided into two groups of 30 each according to their dietary regimens. The test group was fed with a high cholesterol-containing diet for two months while the control group had standard diet. These two groups were further divided into three subgroups consisting of ten rats each. After hypercholesterolemia was established, left colon resection and anastomosis were performed in both groups and samples from liver and abdominal aorta were taken to evaluate the systemic effects of hypercholesterolemia. Anastomotic wound healing, blow-out pressures and tissue hydroxyproline levels were evaluated.

RESULTS: The test group had a significant weight gain in two months. Microscopic examination of the abdominal aorta revealed no atherosclerotic change in none of the groups, but liver tissue specimens showed significant steatosis in the test group. Tissue hydroxyproline levels and anastomotic blow-out pressures were significantly lower in the test group than in the controls.

CONCLUSION: Hypercholesterolemia not only increases hydroxyproline levels and blow-out pressures but also worsens anastomotic wound healing.

Pitavastatin Prevents Bacterial Translocation after Nonpulsatile/Low-Pressure Blood Flow in Early Atherosclerotic Rat: Inhibition of Small Intestine Inducible Nitric Oxide Synthase

BACKGROUND

Cardiopulmonary bypass decreases intestinal mucosal blood flow because of nonpulsatile and low-pressure blood flow resulting in bacterial translocation (BT) and atherosclerosis also has peripheral blood flow deficiency. The risk of nonpulsatile and low-pressure blood flow for atherosclerotic animals and the effect of statin administration, which has pleiotropic effects, were studied.

METHODS

Wistar rats were divided into four groups: group N (normal diet), group C (high-cholesterol diet), group S (group C plus pitavastatin therapy), and group I [group C plus inducible nitric oxide (iNOS) inhibitor therapy]. First of all, vascular responses were measured. Then the rats underwent nonpulsatile/low-pressure blood flow in the intestine, and the serum peptidoglycan concentration as a parameter of BT, the small intestinal PO(2) ratio (intestinal PO(2)/PaO(2)) as a parameter of mucosal blood flow, and NO concentrations were measured before surgery (T0), at the end of 90 min of stenosis (T1), and 90 min after the release of stenosis (T2). Immunostaining for nitrotyrosine was also performed at T2.

RESULTS

Group C had vascular endothelial dysfunction without histological changes, which indicated early atherosclerosis. The serum peptidoglycan concentration increased significantly at T2 only in group C. The intestinal PO(2) ratio was decreased at T1 in all the groups, and retuned to baseline at T2 in group N and group S, but not in group C or group I. Jejunal NO only in group C was significantly higher at all time points and ileal NO production at T1 and T2. There tended to be a positive stain for nitrotyrosine along the mucosal epithelium in group C.

CONCLUSION

In the setting of early atherosclerosis, intestinal blood flow does not only improve after nonpulsatile/low-pressure blood flow but causes BT because of a large amount of NO from high enzymatic intestinal iNOS activity, and pitavastatin treatment can prevent BT by improving both issues.

Hypercholesterolemia impairs reactive hyperemic vasodilation of 2A but not 3A arterioles in mouse cremaster muscle

Hypercholesterolemia and atherosclerosis have been associated with changes in the microvasculature, in particular with endothelial dysfunction. In the present study, the impact of atherogenic conditions on arteriolar vasomotor control was determined. Arteriolar [second-order (2A) and third-order (3A) arterioles; diameter range: 9–37 μm] responses during reactive hyperemia (RH) were determined in cremaster muscle of anesthetized mice. C57Bl/6 mice on normal rodent chow were used as controls and high-fat/high-cholesterol (HFC)-fed C57Bl/6 and ApoE3-Leiden mice as hypercholesterolemic mice. The HFC diet resulted in time-dependent increases in plasma cholesterol and triglyceride concentrations ( P < 0.001), which were more pronounced in ApoE3-Leiden mice ( P < 0.001). In control mice, inhibition of nitric oxide (NO) synthesis with Nω-nitro-l-arginine (l-NNA) reduced baseline diameter from 17.9 ± 1.2 to 15.9 ± 1.3 μm ( P < 0.05) and decreased the duration of RH [time to 50% ( t50) of recovery: 23.3 ± 3.6 vs. 12.5 ± 1.3 s ( P = 0.003)]. t50was longer in 2A versus 3A arterioles (33 ± 3 vs. 18 ± 2 s, P < 0.001) and increased with wall shear rate at the beginning of RH in 2A arterioles only. Compared with control mice, RH duration was reduced in 2A arterioles of HFC mice ( t50: 11 ± 2 s, P < 0.001 vs. control) but not affected in 3A vessels. l-NNA did not affect baseline diameter in HFC mice and reduced t50only in “slow” responders ( t50≥ 10 s). It is concluded that hypercholesterolemia results in an impairment of NO-mediated vasomotor control in 2A but not 3A arterioles during dynamic changes of perfusion like RH. 2A arterioles likely therefore represent the functional locus of endothelial dysfunction during atherogenic conditions.

Lipids and endothelium-dependent vasodilation--a review

Studies using both in vitro and in vivo techniques have repeatedly shown that endothelium-dependent vasodilation (EDV) is impaired in different forms of experimental as well as human hypercholesterolemia. Clearly this impaired EDV can be reversed by lowering cholesterol levels by diet or medical therapy. Competitive blocking of L-arginine, changes in nitric oxide synthase activity, increased release of endothelin-1, and inactivation of nitric oxide due to superoxide ions all contribute to the impairment in EDV during dyslipidemia. The oxidation of low density lipoprotein, with its compound lysophosphatidylcholine, plays a critical role in these events. However, data on the role of triglycerides and fat-rich meals regarding EDV are not so consistent as data for cholesterol, although a view that the compositions of individual fatty acids and antioxidants are of major importance is emerging. Thus, this review shows that while impaired EDV is a general feature of hypercholesterolemia, the mechanisms involved and the therapeutic opportunities available still have to be investigated. Furthermore, discrepancies regarding the role of triglycerides and fat content in food may be explained by divergent effects of different fatty acids on the endothelium.

The microphotohemolytic response of erythrocytes is altered by streptozotocin-induced diabetes and copper deficiency in rats

Microphotohemolysis is a new technique that has been used to determine the presence of alterations in the erythrocyte membrane. The method involves light activation through a microscope of a fluorescent dye-erythrocyte-buffer solution in a hemocytometer. The interaction of the light and dye result in the generation of toxic oxygen products which attack the membrane allowing water to enter the cell. As hemolysis occurs the optical density of the microscopic field decreases and this is recorded for later quantitation with an image analysis system. Maximal effect, time to half maximal effect and the slope of the hemolysis curve are determined. The goal of this study was to determine if microphotohemolysis could be used to detect differences in erythrocytes from animals with altered physiological states such as hypercholesterolemia, diabetes, and copper deficiency. These are conditions that alter the lipid or protein structure of the erythrocyte membrane and/or the antioxidative capacity of the erythrocyte. There were no effects of hypercholesterolemia on the microphotohemolytic response of the erythrocyte. Streptozotocin-induced diabetes resulted in a decreased maximum effect, a significant shift of the hemolysis curve to the right (increased T 1/2) and a significant decrease in the slope of the hemolysis curve. Copper deficiency resulted in a significant decrease in the slope of the hemolysis curve. These results in diabetes and copper deficiency are consistent with an altered protein structure in the erythrocyte membrane that occurs in these conditions. The data demonstrate that this technique may be used to detect differences between normal and altered erythrocytes. As such, it could be useful in monitoring the course of a disease or its treatment.

The antioxidant butylated hydroxytoluene prevents early cholesterol-induced microcirculatory changes in rabbits

Microcirculation was studied during 10 wk in untreated rabbits (n = 13) and in rabbits treated with dietary addition of 1% cholesterol (n = 13), 1% cholesterol + 1% of the antioxidant BHT (butylated hydroxytoluene) (n = 11), or 1% BHT (n = 5). The studies were performed by direct intravital microscopic imaging of the left and right conjunctivae with the use of a stereo microscope and a high resolution television camera. Microvessel diameter, erythrocyte flow velocity, and microhemorheologic conditions were evaluated quantitatively via a computer-assisted digital image processing system. Significant and marked changes occurred in all the above variables as a consequence of cholesterol feeding. After 3 wk of feeding there was a dramatic decrease (approximately 30%) in blood flow velocity in arterioli of the third order (P < 0.0001), accompanied by aggregation of cells in 40-50% of the smaller conjunctival vessels (P < 0.0001). These changes were enhanced further during the following 7 wk of treatment. All the above changes in the microcirculation were markedly reduced by the addition of BHT treatment. The diameter of the above arterioli decreased in the purely cholesterol-fed group (P < 0.005), whereas this did not occur in the group fed both cholesterol and BHT. In rabbits fed BHT in the absence of cholesterol, there was no significant effect on any assessed microcirculatory variable. In conclusion, the results demonstrate that the antioxidant BHT prevented early cholesterol-induced microcirculatory changes. This prevention occurred in the absence of a reduction of blood lipid levels. The results provide strong support for the hypothesis that a considerable part of the effects on microcirculation in hypercholesterolemia may be due to cholesterol-induced oxidations and not to cholesterol itself. The results are discussed in relation to the previously demonstrated antiatherogenic effect of BHT and the possible use of antioxidants in the therapy and prophylaxis of atherosclerosis.

Premature carotid atherosclerosis: does it occur in both familial hypercholesterolemia and homocystinuria? Ultrasound assessment of arterial intima-media thickness and blood flow velocity

BACKGROUND AND PURPOSE

Homocystinuria due to cystathionine beta-synthase deficiency and familial hypercholesterolemia are inherited disorders of metabolism that are associated with premature development of cardiovascular disease. This study addresses the possibility that different patterns of carotid wall damage and cerebral blood flow hemodynamics are present in these two metabolic diseases.

METHODS

Twelve patients with homocystinuria due to cystathionine beta-synthase deficiency (mean age, 24 years), 10 patients with homozygous familial hypercholesterolemia (mean age, 26 years), and 11 healthy control subjects (mean age, 26 years) underwent a vascular examination by noninvasive methods. B-mode ultrasound imaging was used to obtain measurements of intima-media thickness of common carotid, bifurcation, and internal carotid arteries as an index of atherosclerosis. Cerebral blood flow velocity was estimated from vascular examination of the middle cerebral artery by transcranial Doppler. Systolic, diastolic, and mean velocities were measured. Pulsatility index, a possible indicator of vascular resistance in the cerebral circulation, was also calculated.

RESULTS

Mean maximum intima-media thickness was 1.4 mm in patients with familial hypercholesterolemia, 0.6 mm in patients with homocystinuria, and 0.6 mm in control subjects. The difference between hypercholesterolemic and homocystinuric patients or control subjects was statistically significant (P < .001). Diastolic blood flow velocities were significantly reduced in the middle cerebral arteries of hypercholesterolemic patients compared with homocystinuric patients or control subjects (P < .05), whereas systolic or mean velocities did not differ. The pulsatility index, a possible indicator of vascular resistance in the cerebral circulation, was significantly higher in hypercholesterolemic patients compared with homocystinuric patients or healthy control subjects (P < .01). A direct relation was demonstrated between pulsatility index of the middle cerebral artery and mean maximum intima-media thickness of carotid arteries on the same side (P < .001).

CONCLUSIONS

Familial hypercholesterolemia is responsible for diffuse and focal thickening of carotid arteries and possibly also for hyperlipidemic endothelial dysfunction extending to small resistance arteries and leading to a disturbed cerebral blood flow. Patients with homocystinuria due to homozygosis for cystathionine beta-synthase deficiency seldom have plaques in their carotid arteries. They are similar to healthy control subjects with regard to both intima-media thickness and blood flow velocity in the middle cerebral artery. Therefore, it is unlikely that typical atherosclerotic lesions precede thrombotic events in homocystinuria. However, it is possible that arterial dilatations caused by medial damage lead to thrombosis in homocystinuric patients.

Cerebral blood flow velocity and systemic vascular resistance after acute reduction of low-density lipoprotein in familial hypercholesterolemia

BACKGROUND AND PURPOSE

Low-density lipoprotein apheresis is currently used for the treatment of familial hypercholesterolemia, an inherited disorder of metabolism associated with premature development of cardiovascular disease. We wanted to evaluate cerebral blood flow velocity, cardiac output, and systemic vascular resistance in patients with familial hypercholesterolemia before and after low-density lipoprotein apheresis.

METHODS

Ten patients (age range, 14 to 46 years; 4 males, 6 females) with familial hypercholesterolemia (8 homozygotes, 2 heterozygotes) and 10 healthy control subjects of comparable age and sex distribution participated in the study. Low-density lipoprotein apheresis by dextran sulfate was performed in 8 patients (7 homozygotes, 1 heterozygote). Six patients (4 homozygotes, 2 heterozygotes) underwent a procedure of extracorporeal erythrocyte filtration with the same extracorporeal volume as for low-density lipoprotein apheresis, but with the exclusion of the passage of plasma through the dextran sulfate column. Cerebral blood flow velocity (transcranial Doppler), cardiac output, and systemic vascular resistance (electric bioimpedance cardiography) were determined by noninvasive techniques before and 1 day and 7 days after low-density lipoprotein apheresis or extracorporeal erythrocyte filtration. Plasma and blood viscosities were measured at the same time.

RESULTS

Before apheresis, mean and diastolic cerebral flow velocities were abnormally low in hypercholesterolemic patients (P < .01 and P < .02 vs healthy control subjects, respectively). After apheresis, low-density lipoprotein cholesterol was lowered by 40% to 60% from baseline, and cerebral blood flow velocities (mean, systolic, and diastolic velocities) were increased (P < .01). Cardiac output, systemic vascular resistance, and viscosity values were not significantly modified. Extracorporeal erythrocyte filtration (without passage of plasma through the dextran sulfate column) did not modify serum lipids, hemodynamic parameters, or viscosity values.

CONCLUSIONS

Low-density lipoprotein apheresis produces potentially useful hemodynamic effects. They are not adequately explained by changes in blood viscosity alone and might reflect a restoration of endothelium-mediated vasodilation, which is inhibited by high concentrations of low-density lipoprotein.

Differentiation of light-dye effects in the microcirculation

Activation of photosensitive compounds has been used in the treatment of tumors and as a technique to study various microcirculatory phenomena. This technique may be accompanied by deleterious effects which may complicate interpretations of experimental results. However, the relevant physiological mechanisms that induce toxicity and the light doses needed to produce different toxic reactions have not been well defined. In the current study, the rat cremaster muscle preparation was used with in vivo fluorescent television microscopy and subsequently with electron and light microscopy to evaluate toxic reactions of light activation of fluorescein isothiocyanate. The most sensitive photoactive reactions were macromolecular leakage and platelet activation, occurring with 120 J/cm2 activation energy. Macromolecular leakage was at least partially restricted by perivenular and pericapillary pericytes and there was no morphological damage with this light dose. Since macromolecular leakage was significantly inhibited by pretreatment with diphenhydramine or Compound 48/80, it is in part due to the release of histamine from tissue mast cells. 720 J/cm2 reduced the red blood cell column in the venules by over 50% due to platelet thrombus formation, an effect that was accentuated by pretreatment with indomethacin. This suggests an inhibitory role of prostaglandins in platelet thrombus formation. In addition, 720 J/cm2 caused endothelial and smooth muscle cell swelling and ruptures, gap formation, and leukocyte and protein accumulation in the vessel walls.

On lowering lipids in the post-infarction patient

In patients with coronary heart disease (CHD) elevated serum cholesterol levels, like other classical risk factors, remain predictive of further coronary events. The excess risk attributable to raised cholesterol levels is considerable, and greater than that in subjects without CHD. A recent meta-analysis of all eight qualifying trials of secondary prevention of CHD by cholesterol lowering is reviewed. There were significant reductions in recurrent non-fatal and fatal CHD, with a downward trend in total mortality. Mechanisms underlying the relationship between cholesterol lowering and secondary prevention are reviewed. The implication of this analysis of trials for clinical practice is that hypercholesterolaemia should be sought and effectively treated in patients with CHD, unless contraindications are present.