Lipoprotein(a): an elusive cardiovascular risk factor

Apheresis in Coronary Heart Disease With Elevated Lp (a): A Review of Lp (a) As a Risk Factor and Its Management

Lipoprotein (a) (Lp (a)) increases global cardiovascular risk, especially when LDL cholesterol is concomitantly elevated. Epidemiologic data show that Lp (a) concentration in plasma can be used to predict the risk of early atherogenesis in a dose-dependent manner and late stages of atherosclerosis are accelerated by elevated Lp (a). Therapeutic means to lower Lp (a) are limited. The most effective method to reduce plasma Lp (a) concentration significantly is therapeutic apheresis. Because apheresis is laborious and expensive, patients considered for this procedure should suffer from high Lp (a) concentrations, well beyond 50 mg/dL, and have manifested and progressive coronary heart disease despite maximal drug therapy. Experimental data and therapeutic results will be discussed in the present paper.

Preoperative carotid artery screening in patients undergoing coronary artery bypass graft surgery

BACKGROUND

The incidence of stroke is 2.1-5.2% in bypass surgery patients with a mortality of 0-38%. This study was designed to evaluate the incidence of significant carotid artery stenosis and its related risk factors in candidates for coronary artery bypass graft (CABG) surgery.

METHODS

One thousand forty five consecutive candidates for CABG underwent carotid artery Doppler examination in a prospective study. The relation of age, sex, smoking and diabetes history, as well as lipid profile with carotid stenosis, was evaluated.

RESULTS

In 1045 CABG candidates with a mean age of 60 years, prevalence of significant carotid stenosis (>60%) was 6.9%. In the patients aged 65 years and older, the rate of significant stenosis was 12.5%. Age >50 years, female gender, hypercholesterolemia and diabetes mellitus are independent risk factors for significant carotid stenosis.

CONCLUSIONS

Significant carotid stenosis has an earlier appearance in our study. Cost-effectiveness studies are recommended for revising the previous screening protocols.

TagSNP evaluation for the association of 42 inflammation loci and vascular disease: evidence of IL6, FGB, ALOX5, NFKBIA, and IL4R loci effects

Inflammatory markers have consistently been associated with vascular disease. Evidence of genetic polymorphisms in inflammatory loci that predict severe carotid artery disease (CAAD) would suggest that this relationship is not secondary to other correlated factors, but related to inflammation itself. We examined the full common genetic variation in 42 inflammatory loci for prediction of severe CAAD versus ultrasound proven controls using a tagSNP approach. For selected loci, monocyte RNA levels were contrasted in subjects with and without CAAD. We confirm the association of IL6(-174), FGB (-455), and ALOX5 with CAAD and show that multiple ALOX5 SNPs independently predict CAAD. We provide evidence for previously unreported associations of SNPs in IL4R, NFKBIA, and PLG with CAAD, and weaker evidence for associations with CSF3, IL10RA, and VCAM1. The NFKBIA and IL10RA expression levels significantly differed between subjects with CAAD and controls. These results support a role for genetic variation related to inflammation in CAAD and a causal role for specific gene products.

Lipoprotein(a) and atherosclerosis: new perspectives on the mechanism of action of an enigmatic lipoprotein

Although elevated plasma concentrations of lipoprotein(a) (Lp(a)) have been identified as a risk factor for coronary heart disease, the pathophysiologic and physiologic roles of Lp(a) continue to elude basic researchers and clinicians alike. Lp(a) is a challenging lipoprotein to study because it has a complex structure consisting of a low-density lipoprotein-like moiety to which is covalently attached the unique glycoprotein apolipoprotein(a) (apo(a)). Apo(a) contains multiply repeated kringle domains that are similar to a sequence found in the fibrinolytic proenzyme plasminogen; differing numbers of kringle sequences in apo(a) give rise to Lp(a) isoform size heterogeneity. In addition to elevated plasma concentrations of Lp(a), apo(a) isoform size has been identified as a risk factor for coronary heart disease, although studies addressing this relationship have been limited. The similarity of Lp(a) to low-density lipoprotein and plasminogen provides an enticing link between the processes of atherosclerosis and thrombosis, although a clear demonstration of this association in vivo has not been provided. Clearly, Lp(a) is a risk factor for both atherothrombotic and purely thrombotic events; a plethora of mechanisms to explain these clinical findings has been provided by both in vitro studies as well as animal models for Lp(a).

Lipoprotein(a) is an independent risk factor for cardiovascular disease in heterozygous familial hypercholesterolemia

BACKGROUND

The role of lipoprotein(a) [Lp(a)] as a predictor of cardiovascular disease (CVD) in patients with heterozygous familial hypercholesterolemia (HFH) is unclear. We sought to examine the utility of this lipoprotein as a predictor of CVD outcomes in the HFH population at our lipid clinic.

METHODS

This was a retrospective analysis of clinical and laboratory data from a large multiethnic cohort of HFH patients at a single, large lipid clinic in Vancouver, Canada. Three hundred and eighty-eight patients were diagnosed with possible, probable, or definite HFH by strict clinical diagnostic criteria. Multivariate Cox regression analysis was used to study the relationship between several established CVD risk factors, Lp(a), and the age of first hard CVD event.

RESULTS

An Lp(a) concentration of 800 units/L (560 mg/L) or higher was a significant independent risk factor for CVD outcomes [hazard ratio (HR) = 2.59; 95% confidence interval (CI), 1.53-4.39; P < 0.001]. Other significant risk factors were male sex [HR = 3.19 (1.79-5.69); P < 0.001] and ratio of total to HDL-cholesterol [1.18 (1.07-1.30); P = 0.001]. A previous history of smoking or hypertension each produced HRs consistent with increased CVD risk [HR = 1.55 (0.92-2.61) and 1.57 (0.90-2.74), respectively], but neither reached statistical significance (both P = 0.10). LDL-cholesterol was not an independent predictor of CVD risk [HR = 0.85 (0.0.71-1.01); P = 0.07], nor was survival affected by the subcategory of HFH diagnosis (i.e., possible vs probable vs definite HFH).

CONCLUSION

Lp(a) is an independent predictor of CVD risk in a multiethnic HFH population.

Lipoprotein(a) as a cardiovascular risk factor

Evidence for the role of lipoprotein(a) (Lp[a]) in atherosclerosis and thrombosis has considerably increased over the past few years. Therefore, Lp(a) is currently classified as an emerging lipid risk factor for cardiovascular disease. High Lp(a) plasma levels carried in particles with small-sized apolipoprotein(a) isoforms are associated with preclinical vascular changes, cardiovascular disease and the mode of presentation of coronary artery disease (acute coronary syndromes). However, randomized clinical trials with an emphasis on agents that specifically lower plasma Lp(a) do not exist. At present, screening for increases in Lp(a) in the general population is not recommended. The measurement of Lp(a) may be of value in individuals with an increased risk of cardiovascular disease, particularly in patients with high low-density lipoprotein cholesterol plasma levels, since a high Lp(a) concentration in such subjects further increases the risk of coronary heart disease.

Coronary heart disease and polymorphisms in genes affecting lipid metabolism and inflammation

Several biologic systems contribute to the pathophysiology of atherosclerosis and its complications, and within each of these systems many genes have been explored to establish the possible implication of their variability in coronary heart disease (CHD) risk. This report is focused on recent results pertaining to lipid and inflammatory genes, their variability, and their relationship with intermediate phenotypes and CHD. For both systems, there is no evidence at the present time that testing genetic polymorphisms might be of any benefit to the patient, for the diagnosis or prognosis of CHD, or for tailoring drug prescription. Understanding the genetics of complex traits like CHD will require a system approach that allows a modeling of the interaction among genes as well as between genetic and nongenetic sources of variation.