Anemia as a risk factor for cardiovascular disease

Diffuse reflectance spectra of the palpebral conjunctiva and its utility as a noninvasive indicator of total hemoglobin

The palpebral conjunctiva is an attractive location to qualitatively examine for the presence of anemia; however, this method of diagnosis has not been shown to be accurate. A spectroscopic examination of the palpebral conjunctiva enables the use of a quantitative parameter as a basis for diagnoses. Visible range diffuse reflectance spectra from the palpebral conjunctiva are examined from 30 patients and hemoglobin levels are extracted from these signatures using both a partial least-squares (PLS) multivariate regression model and a discrete spectral region model. Hemoglobin concentration derived from both these models is compared to an in vitro measurement of hemoglobin. Root mean squared errors of cross validation for the two analytical methods are 0.67 g/dL and 1.07 g/dL, respectively. Conjunctival reflectance spectra coupled with a PLS analysis achieve an enhanced specificity and sensitivity for anemia diagnoses over reported observational studies using the palpebral conjunctiva and achieve improved accuracy to other reported methods of noninvasive hemoglobin measurement.

Enhanced programmed cell death of iron-deficient erythrocytes

Exposure of erythrocytes to osmotic shock, oxidative stress, and energy depletion activates Cl--sensitive and Ca2+-permeable cation channels. Subsequent Ca2+ entry triggers eryptosis, characterized by erythrocyte shrinkage, membrane blebbing, and phosphatidylserine exposure all features typical for apoptotic death of nucleated cells. Erythrocytes exposing phosphatidylserine are recognized, bound, engulfed, and degraded by macrophages. Eryptosis thus fosters clearance of affected erythrocytes from circulating blood. Iron deficiency leads to anemia, in part by decreasing erythrocyte life span. In this study, phosphatidylserine exposure, cell size, and cytosolic Ca2+ were measured by FACS analysis of annexin-V binding, forward scatter, and Fluo-3 fluorescence, respectively. Erythrocytes from mice on control diet were compared with erythrocytes from mice exposed 10 weeks to iron-deficient diet. Iron deficiency significantly (P<0.001) enhanced erythrocyte annexin-V binding (from 2.4 to 3.7%), decreased forward scatter (from 544 to 393), and increased cytosolic Ca2+ concentration. 45Ca2+ flux measurements and patch clamp experiments revealed enhanced Ca2+ uptake (by 2.3-fold) and cation channel activity. The half-life of fluorescence-labeled, iron-deficient, or Ca2+-loaded erythrocytes was significantly reduced compared with control erythrocytes. Thus, the experiments reveal a novel mechanism triggered by iron deficiency, which presumably contributes to accelerated clearance of erythrocytes in iron deficiency anemia.

Anemia and heart failure

Over the past few years, anemia has emerged as a powerful independent predictor of adverse outcomes in chronic heart failure (CHF). It affects up to 50% of patients with CHF, depending on the definition of anemia used and on the population studied. Even small reductions in hemoglobin are associated with worse outcome. However, the causes of anemia in CHF remain unclear, although impairment of renal function and inflammatory cytokines are proposed mechanisms. Both may act through impairment of the synthesis or action of erythropoietin. Preliminary studies have demonstrated improvement in symptoms, exercise tolerance, quality of life, and reductions in hospitalizations when patients with severe CHF were treated with erythropoietin. The benefits and the potential risks of such therapies will be further addressed in upcoming larger randomized trials. The recent interest in anemia reflects a new perspective in heart failure therapy, focusing on non-cardiovascular comorbidities.

Treating the patient with kidney failure to reduce cardiovascular disease risk

The reduction of cardiovascular disease risk in kidney failure involves treatment of modifiable risk factors and provision of proven interventions to patients with established disease. Volume status management is key to blood pressure control. Statins are the agents of choice for the treatment of dyslipidemia. Target hemoglobin levels should be achieved using intravenous iron and erythropoietic agents. Combinations of calcium and noncalcium-containing phosphorus binders and vitamin D and its analogues should be used to attain target parathyroid hormone, phosphorus, and calcium phosphorus product levels. beta Blockers and aspirin are recommended in patients with ischemic heart disease and angiotensin-converting enzyme inhibitors (or angiotensin II receptor blockers), and beta blockers are recommended in patients with heart failure with reduced ejection fraction. In patients who require revascularization, studies suggest a survival benefit of coronary artery bypass graft surgery over percutaneous transluminal coronary angioplasty and coronary artery stenting.