Clinical reality of lowering total and LDL cholesterol

Interrelationships between the fibrinolytic system and lipoproteins in the pathogenesis of coronary atherosclerosis

The fibrinolytic system is comprised of a series of serine proteases and serine protease inhibitors which are involved in the dissolution of fibrin in the vascular lumen, but also in the migration of cells and in the remodeling of the extracellular matrix of the vascular wall. The transcription, expression and degradation of the various fibrinolytic enzymes by cells in the vascular wall is influenced by lipoproteins and this interrelationship may play a significant role in the development of the atherosclerotic plaque: the transcription of plasminogen activator inhibitor-1 is influenced by very low-density lipoproteins, the expression of both tissue plasminogen activator and plasminogen activator inhibitor-1 is influenced by low-density lipoproteins and lipoprotein(a) (Lp(a)) and the internalization of the urokinase: plasminogen activator inhibitor-1 complex occurs via the low-density lipoprotein related protein. Several clinical studies have shown correlations between fibrinolytic parameters and lipoproteins in healthy populations and in patients with dyslipidemia, but the correlation between single plasma fibrinolytic enzymes and the severity of coronary atherosclerosis is less well documented. The reduction of plasma lipids with lipid-lowering drugs also affects the concentration of fibrinolytic enzymes, although this may also be due to direct effects of the drugs on the expression of the various fibrinolytic enzymes. The reduction of fibrinolytic and proteolytic activity in the atherosclerotic plaque by their lipid-lowering effect and by their direct action on the fibrinolytic system may be one of the mechanisms by which some lipid-lowering drugs achieve plaque stabilization.

Low-density lipoprotein apheresis for the treatment of refractory hyperlipidemia

The advent of treatment with 3-hydroxy-3-methylglutaryl coenzyme A inhibitors has meant that, with a combination of diet and drug therapy, adequate control of serum cholesterol concentrations can be achieved in most patients with hypercholesterolemia. However, some patients, primarily those with familial hypercholesterolemia (FH), may require additional therapy to lower their cholesterol levels. In recent years, low-density lipoprotein (LDL) apheresis has emerged as an effective method of treatment in these patients. The criteria for commencement of LDL apheresis are LDL cholesterol levels of 500 mg/dL or higher for homozygous FH patients, 300 mg/dL or higher for heterozygous FH patients in whom medical therapy has failed, and 200 mg/dL or higher for heterozygous FH patients with documented coronary disease and in whom medical therapy has failed. In addition to cholesterol lowering in patients with FH, other indications for LDL apheresis are emerging. These include its use in the treatment of graft vascular disease in patients receiving cardiac transplants as well as in the treatment of certain glomerulonephritides. This review examines the role of LDL apheresis in the management of lipid disorders and the evidence available to support its use in clinical practice.

Effects of lipid-lowering drugs on left ventricular function and exercise tolerance in dyslipidemic coronary patients

Previous studies suggested that certain lipid-lowering drugs such as statins suppress ubiquinone, affect mitochondrial function, and may have deleterious effect on skeletal or cardiac muscles with potentially serious clinical consequences, especially in patients with established coronary heart disease and left ventricular dysfunction. In this double-blind study, we assessed the effects of 20 mg simvastatin (S, n = 32) or 200 mg micronized fenofibrate (F, n = 32, control group) on rest and exercise left ventricular function in hypercholesterolemic survivors of a previous Q-wave acute myocardial infarction. Left ventricular radionuclide imaging was performed at rest and during submaximal exercise and global and segmental (nine segment regional wall-motion score) ejection fractions were measured before treatment and 12 weeks later. Serum ubiquinone was reduced after treatment (p = 0.03) in the S but not the F group, whereas total and low-density lipoprotein (LDL) cholesterol were significantly reduced in both groups. Before treatment, mean global ejection fraction was 52.1+/-12.2% and 49.3+/-11.8% at rest in F and S patients, respectively, and increased (56.0+/-13.7% in F and 52.1+/-12.9% in S) at peak exercise (no difference between groups). After treatment, the increase in ejection fraction tended to be lower in S (0) than in F (+3.8%) but not significantly. However, ejection fraction at rest increased after treatment in S (p = 0.009) but not in F. Subgroup analyses indicated that the improvement in rest ejection fraction in S was essentially observed in patients with ejection fraction <40% (n = 8, +6%), whereas it was stable in patients with ejection fraction >40% (+1.8%). Finally, the numbers of akinetic or hypokinetic segments at rest and during exercise were not different in the two groups before and after treatment. Mean maximal exercise load (113+/-23 watts in F vs. 104+/-27 W in S before treatment) was not modified by the treatment (111+/-21 and 104+/-27 W). Thus a 12-week lipid-lowering treatment with either S or F did not negatively alter left ventricular function during exercise in dyslipidemic patients with established coronary heart disease and did not affect their ability to exercise. The improvement in left ventricular function at rest after simvastatin in patients with left ventricular dysfunction warrants confirmation in further studies with large sample size.