Lipoprotein (a) and its relationship to risk factors and severity of atherosclerotic peripheral vascular disease

Lipoprotein(a) as a Risk Factor for Cardiovascular Diseases: Pathophysiology and Treatment Perspectives

Cardiovascular disease (CVD) is still a leading cause of morbidity and mortality, despite all the progress achieved as regards to both prevention and treatment. Having high levels of lipoprotein(a) [Lp(a)] is a risk factor for cardiovascular disease that operates independently. It can increase the risk of developing cardiovascular disease even when LDL cholesterol (LDL-C) levels are within the recommended range, which is referred to as residual cardiovascular risk. Lp(a) is an LDL-like particle present in human plasma, in which a large plasminogen-like glycoprotein, apolipoprotein(a) [Apo(a)], is covalently bound to Apo B100 via one disulfide bridge. Apo(a) contains one plasminogen-like kringle V structure, a variable number of plasminogen-like kringle IV structures (types 1-10), and one inactive protease region. There is a large inter-individual variation of plasma concentrations of Lp(a), mainly ascribable to genetic variants in the Lp(a) gene: in the general po-pulation, Lp(a) levels can range from <1 mg/dL to >1000 mg/dL. Concentrations also vary between different ethnicities. Lp(a) has been established as one of the risk factors that play an important role in the development of atherosclerotic plaque. Indeed, high concentrations of Lp(a) have been related to a greater risk of ischemic CVD, aortic valve stenosis, and heart failure. The threshold value has been set at 50 mg/dL, but the risk may increase already at levels above 30 mg/dL. Although there is a well-established and strong link between high Lp(a) levels and coronary as well as cerebrovascular disease, the evidence regarding incident peripheral arterial disease and carotid atherosclerosis is not as conclusive. Because lifestyle changes and standard lipid-lowering treatments, such as statins, niacin, and cholesteryl ester transfer protein inhibitors, are not highly effective in reducing Lp(a) levels, there is increased interest in developing new drugs that can address this issue. PCSK9 inhibitors seem to be capable of reducing Lp(a) levels by 25-30%. Mipomersen decreases Lp(a) levels by 25-40%, but its use is burdened with important side effects. At the current time, the most effective and tolerated treatment for patients with a high Lp(a) plasma level is apheresis, while antisense oligonucleotides, small interfering RNAs, and microRNAs, which reduce Lp(a) levels by targeting RNA molecules and regulating gene expression as well as protein production levels, are the most widely explored and promising perspectives. The aim of this review is to provide an update on the current state of the art with regard to Lp(a) pathophysiological mechanisms, focusing on the most effective strategies for lowering Lp(a), including new emerging alternative therapies. The purpose of this manuscript is to improve the management of hyperlipoproteinemia(a) in order to achieve better control of the residual cardiovascular risk, which remains unacceptably high.

Predictive value of lipoprotein(a) for assessing the prevalence and severity of lower-extremity peripheral artery disease among patients with acute coronary syndrome

Lipoprotein(a) [Lp(a)] is a reliable lipid marker for atherosclerosis. However, the clinical relevance of Lp(a) to lower-extremity peripheral artery disease (LE-PAD) and coronary artery disease (CAD) in the same patient has not been investigated. Patients who received primary percutaneous coronary intervention for the acute coronary syndrome (ACS) were enrolled. Patients who received hemodialysis, required multidisciplinary treatments, or had incomplete medical history were excluded. A total of 175 patients were divided into two groups according to whether they had LE-PAD (n = 21) or did not (n = 154), and three multivariable logistic regression models were used to assess if Lp(a) level is associated with LE-PAD prevalence. In addition, serum Lp(a) levels were compared among three groups according to the severity of LE-PAD (none, unilateral, or bilateral) and CAD. Serum Lp(a) levels were significantly higher in patients with LE-PAD than in those without (31.0 mg/dL vs. 13.5 mg/dL, p = 0.002). After adjusting for confounding factors, higher Lp(a) levels were independently associated with the prevalence of LE-PAD in all three models (p < 0.001 for all). With respect to LE-PAD severity, serum Lp(a) levels were significantly higher in the bilateral LE-PAD groups than in the group with no LE-PAD (p = 0.005 for all), whereas Lp(a) was not associated with CAD severity. Though Lp(a) levels are associated with the prevalence and severity of LE-PAD, are not associated with the severity of CAD among patients with ACS.

Impact of lipoprotein(a) levels on primary patency after endovascular therapy for femoropopliteal lesions

Lipoprotein(a) [Lp(a)] is a risk factor for peripheral artery disease (PAD). However, the relationship between Lp(a) levels and clinical events after endovascular therapy (EVT) for the femoropopliteal artery in PAD patients remains unclear. Thus, this study aimed to assess the impact of Lp(a) levels on primary patency after EVT for de novo femoropopliteal lesions in PAD patients. A retrospective analysis was conducted on 109 patients who underwent EVT for de novo femoropopliteal lesions, and Lp(a) levels were measured before EVT between June 2016 and December 2019. Patients were divided into low Lp(a) [Lp(a) < 30 mg/dL; 78 patients] and high Lp(a) [Lp(a) ≥ 30 mg/dL; 31 patients] groups. The main outcome was primary patency following EVT. Loss of primary patency was defined as a peak systolic velocity ratio > 2.4 on a duplex scan or > 50% stenosis on angiography. Cox proportional hazards analysis was performed to determine whether high Lp(a) levels were independently associated with loss of primary patency. The mean follow-up duration was 28 months. The rates of primary patency were 83 and 76% at 1 year and 75 and 58% at 2 years in the low and high Lp(a) groups, respectively (P = 0.02). After multivariate analysis, High Lp(a)[Lp(a) ≥ 30 mg/dL] (hazard ratio 2.44; 95% CI 1.10-5.44; P = 0.03) and female sex (hazard ratio 2.65; 95% CI 1.27-5.51; P < 0.01) were independent predictors of loss of primary patency. Lp(a) levels might be associated with primary patency after EVT for de novo femoropopliteal lesions.

Lipoprotein (a) and long-term outcome in patients with peripheral artery disease undergoing revascularization

BACKGROUND AND AIMS

Despite low LDL-C goals, the residual risk for further cardiovascular (CV) events in patients with peripheral artery disease (PAD) remains high. Lipoprotein (a) (Lp(a)) is a known risk factor for PAD incidence, but little is known regarding the outcome in patients with symptomatic PAD. Thus, this study investigates Lp(a) and CV mortality in PAD after endovascular repair.

METHODS

A total of 1222 patients with PAD in two cohorts according to Lp(a) assay in nmol/L (n = 964, Lip-LEAD-A) or mg/dl (n = 258, Lip-LEAD-B) were followed up for 4.3 (IQR 3.0-5.6) or 7.6 (IQR 3.2-8.1) years. Lp(a) was measured before endovascular repair for either intermittent claudication (IC) or critical limb ischemia (CLI). Outcome information was obtained from the federal death registry.

RESULTS

In Lip-LEAD-A, 141 CV-deaths occurred (annual calculated CV-death rate 3.4%), whereas 64 CV-deaths were registered in Lip-LEAD-B (annual calculated CV-death rate 3.3%). After adjustment for traditional CV risk factors Lp(a) was neither associated with outcome in Lip-LEAD-A (highest tertile HR 1.47, 95%CI [0.96-2.24]) nor in Lip-LEAD-B (highest tertile HR 1.34 [0.70-2.58]). Subanalyses for IC (HR 1.37 [0.74-2.55]; HR 1.10 [0.44-2.80], CLI (HR 1.55 [0.86-2.80], HR 3.01 [0.99-9.10]), or concomitant coronary artery disease (CAD; HR 1.34 [0.71-2.54]; HR 1.21 [0.46-3.17]) failed to show a significant association between Lp(a) and CV-mortality.

CONCLUSIONS

In this large-scale cohort of symptomatic PAD no association of elevated Lp(a) with CV mortality was found over a median observation period of 5 years. Thus, an even longer study including asymptomatic patients is warranted.

Association of Lipoprotein(a) Levels With Incidence of Major Adverse Limb Events

IMPORTANCE

High lipoprotein(a) (Lp[a]) levels are involved in the development of cardiovascular events, particularly in myocardial infarction, stroke, and peripheral artery disease. Studies assessing the Lp(a) levels associated with adverse lower-limb events are lacking.

OBJECTIVE

To assess the association between Lp(a) levels and incidence of major adverse limb events in unselected hospitalized patients.

DESIGN, SETTING, AND PARTICIPANTS

This large retrospective monocentric cohort study was conducted from January 1, 2000, to December 31, 2020. Data were derived from the clinical information system of the Hôpital Européen Georges-Pompidou, a Paris-based university hospital. Patients who underwent at least 1 Lp(a) measurement at the center during the study period were included. Patients who had no follow-up data or who had the first Lp(a) measurement after the study outcome had occurred were excluded. Data analyses were performed from May 2021 to January 2022.

MAIN OUTCOMES AND MEASURES

The primary outcome was the first inpatient major adverse limb event, defined as a major amputation, peripheral endovascular revascularization, or peripheral surgical revascularization, during follow-up. Secondary outcomes included individual components of the primary outcome. Lipoprotein(a) levels were categorized as follows: normal (<50 mg/dL), high (50 to <134 mg/dL), and very high (≥134 mg/dL); to convert Lp(a) values to milligrams per liter, multiply by 0.1.

RESULTS

A total of 16 513 patients (median [IQR] age, 58.2 [49.0-66.7] years; 9774 men [59.2%]) were included in the cohort. The median (IQR) Lp(a) level was 24 (10.0-60.0) mg/dL. The 1-year incidence of major adverse limb event was 2.44% in the overall population and 4.54% among patients with very high Lp(a) levels. High (adjusted accelerated failure time [AFT] exponential estimate: 0.43; 95% CI, 0.24-0.78; Benjamini-Hochberg-corrected P = .01) and very high (adjusted AFT exponential estimate: 0.17; 95% CI, 0.07-0.40; Benjamini-Hochberg-corrected P < .001) Lp(a) levels were independently associated with an increased risk of major adverse limb event.

CONCLUSIONS AND RELEVANCE

Results of this study showed that higher Lp(a) levels were independently associated with an increased risk of a major adverse limb event in hospitalized patients. The Lp(a) measurement needs to be taken into account to improve lower-limb vascular risk assessment.

Circulating Biomarkers in Lower Extremity Artery Disease

Lower extremity artery disease (LEAD), a chronic condition with disturbed lower extremity circulation due to narrowing of the arteries, is predominantly caused by atherosclerosis and is associated with the presence of cardiovascular risk factors and an increased risk of cardiovascular events. LEAD is prevalent among older individuals and predicted to rise with the ageing population. In progressive disease, the patient experiences symptoms of ischaemia when walking and, in advanced critical limb-threatening ischaemia, even at rest. However, LEAD is asymptomatic in most patients, delaying diagnosis and treatment. In this setting, circulating biomarkers may facilitate earlier diagnosis in selected individuals. This review provides a broad overview of the circulating biomarkers investigated to date in relation to LEAD and discusses their usefulness in clinical practice.

Association of apolipoprotein levels with peripheral arterial disease: a meta-analysis of literature studies

AIMS

Lower limb peripheral artery disease (PAD) is a leading cause of atherosclerotic cardiovascular disease (ASCVD). Discordant data are available on the association between apolipoprotein and PAD. We performed a meta-analyses on the association between apolipoprotein (apo)B, apoA-I, and apoB/apoA-I ratio with PAD.

METHODS AND RESULTS

PubMed, Web of Science, Scopus databases were systematically searched. Studies providing data about apoB, apoA-I, apoB/apoA-I ratio in PAD subjects and non-PAD controls were included. Differences between PAD and non-PAD subjects were expressed as mean difference (MD) with pertinent 95% confidence intervals (95%CI). Twenty-two studies were included. Peripheral artery disease subjects showed higher apoB (MD: 12.5 mg/dL, 95%CI: 2.14, 22.87) and lower apoA-I levels (MD: -7.11 mg/dL, 95%CI: -11.94, -2.28) than non-PAD controls. Accordingly, ApoB/ApoA-I ratio resulted higher in PAD subjects than non-PAD controls (MD: 0.11, 95% CI: 0.00, 0.21). Non-HDL-C showed a direct association with the difference in apoB (z-value: 4.72, P < 0.001) and an inverse association with the difference of apoA-I (z-value: -2.43, P = 0.015) between PAD subjects and non-PAD controls. An increasing BMI was associated with an increasing difference in apoA-I values between PAD subjects and non-PAD controls (z-value: 1.98, P = 0.047).

CONCLUSIONS

Our meta-analysis suggests that PAD subjects exhibit increased apoB and reduced apoA-I levels, accompanied by an increased apoB/apoA-I ratio as compared with non-PAD controls.

Relationship Between Lipoprotein(a) and Angiographic Severity of Femoropopliteal Lesions

AIM

High levels of lipoprotein(a) [Lp(a)] are a risk factor for peripheral artery disease (PAD). However, the relationship between Lp(a) levels and the severity of femoropopliteal lesions in patients with PAD has not been systematically studied. This study aimed to assess the impact of Lp(a) levels on angiographic severity of femoropopliteal lesions in patients with PAD.

METHODS

We retrospectively analyzed a single-center database including 108 patients who underwent endovascular therapy for de novo femoropopliteal lesions and measured the Lp(a) levels before therapy between June 2016 and September 2019. Patients were divided into low Lp(a) [Lp(a) ＜30 mg/dL; 77 patients] and high Lp(a) [Lp(a) ≥ 30 mg/dL; 31 patients] groups. Trans-Atlantic Inter-Society Consensus (TASC) II classification, calcification [referring to the peripheral arterial calcium scoring system (PACSS) classification], and lesion length were compared between the groups.

RESULTS

The prevalence of TASC II class D (13% vs 38%, P＜0.01) and severe calcification (PACSS 4) (6% vs 23%, P=0.02) was significantly higher and the lesion length longer (123±88 mm vs 175±102 mm, P＜0.01) in the high Lp(a) group than in the low Lp(a) group. In multivariate analysis, Lp(a) ≥ 30 was an independent predictor for the prevalence of TASC II class D (HR=3.67, 95% CI 1.27-10.6, P=0.02) and PACSS 4 (HR=4.97, 95% CI 1.27-19.4, P=0.02).

CONCLUSION

The prevalence of TASC II class D and severe calcification of femoropopliteal lesions was higher in patients with high Lp(a) than those with low Lp(a).

Impact of serum lipoprotein(a) on endothelium-dependent coronary vasomotor response assessed by intracoronary acetylcholine provocation

BACKGROUND

Lipoprotein(a) [Lp(a)] is an independent risk factor for atherosclerotic vascular disease. However, there are limited data regarding the impact of Lp(a) levels on the incidence and severity of endothelium-dependent coronary vasomotor response.

PATIENTS AND METHODS

A total of 2416 patients without significant coronary artery lesion (<50% stenosis) by coronary angiography and underwent acetylcholine (ACh) provocation test were enrolled and categorized according to their serum Lp(a) level into four quartile groups: less than 6.70, 6.70-13.30, 13.30-26.27, and more than 26.27 mg/dl. The aim of this study is to estimate the incidence and severity of endothelium-dependent positive ACh provocation test in each group; moreover, to access the incidence of major adverse cardiovascular events, the composite of total death, myocardial infarction, and de novo percutaneous coronary intervention were compared between the four groups up to 5 years.

RESULTS

The group with higher Lp(a) had a higher incidence of coronary heart disease, myocardial infarction, and peripheral arterial disease history. However, there was no difference among the four groups as regards the incidence of positive ACh provocation test, spasm severity, spasm extent, and location. However, at up to 5 years of clinical follow-up, the higher-Lp(a) group showed higher total death, de novo percutaneous coronary intervention, recurrent angina, and total major adverse cardiovascular events compared with the lower-Lp(a) groups.

CONCLUSION

In our study, there was no relationship between the elevated Lp(a) level and the vasospastic response to the intracoronary ACh provocation test; however, higher Lp(a) levels were associated with poor clinical outcomes up to 5 years.

Biomarkers and Genetics in Peripheral Artery Disease

BACKGROUND

Peripheral artery disease (PAD) is highly prevalent and there is considerable diversity in the initial clinical manifestation and disease progression among individuals. Currently, there is no ideal biomarker to screen for PAD, to risk stratify patients with PAD, or to monitor therapeutic response to revascularization procedures. Advances in human genetics have markedly enhanced the ability to develop novel diagnostic and therapeutic approaches across a host of human diseases, but such developments in the field of PAD are lagging.

CONTENT

In this article, we will discuss the epidemiology, traditional risk factors for, and clinical presentations of PAD. We will discuss the possible role of genetic factors and gene-environment interactions in the development and/or progression of PAD. We will further explore future avenues through which genetic advances can be used to better our understanding of the pathophysiology of PAD and potentially find newer therapeutic targets. We will discuss the potential role of biomarkers in identifying patients at risk for PAD and for risk stratifying patients with PAD, and novel approaches to identification of reliable biomarkers in PAD.

SUMMARY

The exponential growth of genetic tools and newer technologies provides opportunities to investigate and identify newer pathways in the development and progression of PAD, and thereby in the identification of newer biomarkers and therapies.

The Relationship Between Circulating Fibrinogen and Lipoprotein (a) Levels in Patients With Primary Dyslipidemia

The correlation between 2 predictors of vascular events, plasma fibrinogen and serum lipoprotein (a), was evaluated in patients referred to a specialist clinic because of primary hyperlipidemia. A significant correlation existed between fibrinogen and lipoprotein (a) in nonsmokers but not in smokers. Plasma fibrinogen concentration correlated positively and significantly with serum lipoprotein (a) levels in men nonsmokers without cardiovascular disease and in women nonsmokers with cardiovascular disease. Nonsmoker women without cardiovascular disease had significantly higher plasma fibrinogen (3.63 g/L versus 3.07 g/L, P < .0001) than the corresponding men. Nonsmoker women with and without cardiovascular disease had significantly higher lipoprotein (a) levels than the corresponding groups of men (0.36 versus 0.18 g/L; P = .0015 and 0.40 versus 0.26 g/L; P = .008), respectively. The relationship between fibrinogen and lipoprotein (a) levels alters markedly depending on the population selected. This relationship is influenced by gender, the presence of cardiovascular disease and smoking status.

Sex and ethnic differences in the associations between lipoprotein(a) and peripheral arterial disease in the Multi-Ethnic Study of Atherosclerosis

OBJECTIVE

Higher lipoprotein(a) [Lp(a)] has been linked with peripheral arterial disease (PAD). Also, elevated Lp(a) serum levels have been observed in women and African Americans (AAs). It remains uncertain if sex and ethnicity modify the association between Lp(a) and PAD.

METHODS

Lp(a) mass concentration was measured with a latex-enhanced turbidimetric immunoassay, from blood collected at baseline clinic visits after a 12-hour fast, in a multiethnic cohort. Also at baseline, the ankle-brachial index was measured. PAD was defined as an ankle-brachial index <1.0. Multivariable logistic regression was used to determine sex and ethnic differences in associations of log-transformed Lp(a) and the presence of PAD.

RESULTS

In 4618 participants, the mean age was 62 ± 10 years; Lp(a) mean was 30 ± 32 mg/dL and median (interquartile range) was 18 (8-40 mg/dL); 48% were male; 36% were European American, 29% were AA, 23% were Hispanic American (HA), and 12% were Chinese American; and 11% had PAD. Across all ethnic groups, serum Lp(a) was higher among women compared with men and highest among AAs compared with other ethnicities. After adjustments for traditional cardiovascular disease risk factors (age, sex, ethnicity, hypertension, diabetes, smoking, total cholesterol, and high-density lipoprotein cholesterol) as well as interleukin-6, fibrinogen, D-dimer, and homocysteine levels, one log unit increase in Lp(a) was associated with greater odds for PAD (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.01-1.25). In fully adjusted models, significant gender(∗)ln[Lp(a)] and ethnicity(∗)ln[Lp(a)] interactions were observed (P = .08 for both). The association between higher Lp(a) and PAD was strongest in HA men (OR, 1.73; 95% CI, 1.07-2.80) and HA women (OR, 1.49; 95% CI, 1.07-2.08). Nonsignificant associations were observed for European American, AA, and Chinese American men and women.

CONCLUSIONS

We observed a significant and independent association between elevated Lp(a) and PAD only among HA women and men, despite higher serum Lp(a) levels among AAs. Future studies are needed to determine the role that lowering of Lp(a) may have on the burden of PAD in HAs.

Hemodialysis Is Associated With Increased Peripheral Artery Occlusive Disease Risk Among Patients With End-Stage Renal Disease: A Nationwide Population-Based Cohort Study

To investigate the effect of different dialysis modalities on the incidence of peripheral artery occlusive disease (PAOD) among patients with end-stage renal disease (ESRD) in a large population-based cohort study. The cohort study included 26,927 ESRD patients who underwent hemodialysis (17,737 patients, hemodialysis [HD] cohort) or peritoneal dialysis (PD, 9190 patients, PD cohort), and 107,588 matched controls between 2000 and 2010. A Cox proportional hazards model was to evaluate the risk of PAOD in the ESRD underwent HD or PD. Based on a mean follow-up period of 2.92, 3.64, and 4.91 years in the PD, HD, and control cohorts, respectively, the incidences of PAOD were 18.1% and 8.10% higher in the HD and PD cohorts, respectively, compared with the control cohort (log-rank test P < 0.001). The patients who underwent HD or PD exhibited a higher risk of PAOD compared with the control cohort regardless of age, sex, and presence or absence of comorbidities. In addition, the incidence of PAOD in the PD cohort and the propensity score-matched HD cohort were 12.4 and 20.7 per 1000 person-years, respectively, with a hazard ratio of 1.92 (95% confidence interval = 1.62-2.28) in HD patients, compared with the PD cohort. This nationwide population-based cohort study suggested a significantly increased risk of PAOD among ESRD patients. Moreover, the PD patients have a lower risk of developing PAOD compared with the HD cohort, indicating the beneficial roles of PD in reducing PAOD risk in ESRD patients.

Peripheral arterial disease in the Middle East: Underestimated predictor of worse outcome

Peripheral arterial disease (PAD) is a common manifestation of systemic atherosclerosis and is associated with significant morbidity and mortality. The prevalence of PAD in the developed world is approximately 12% among adult population, which is age-dependent and with men being affected slightly more than women. Despite the strikingly high prevalence of PAD, the disease is underdiagnosed. Surprisingly, more than 70% of primary health care providers in the US were unaware of the presence of PAD in their patients. The clinical presentation of PAD may vary from asymptomatic to intermittent claudication, atypical leg pain, rest pain, ischemic ulcers, or gangrene. Claudication is the typical symptomatic expression of PAD. However, the disease may remains asymptomatic in up to 50% of all PAD patients. PAD has also been reported as a marker of poor outcome among patients with coronary artery disease. Despite the fact that the prevalence of atherosclerotic disease is increasing in the Middle East with increasing cardiovascular risk factors (tobacco use, diabetes mellitus and the metabolic syndrome), data regarding PAD incidence in the Middle East are scarce.

Lipoprotein(a) as a potential marker of residual liver function in hepatocellular carcinoma

The residual liver function is a major clinical index in hepatocellular carcinoma (HCC) patients. As the liver plays a crucial role in lipid and lipoprotein metabolism, the significant impairment of the hepatic function occurring during chronic liver diseases, such as HCC, can influence plasma lipoprotein profiles. Although, lipoprotein(a) (Lp(a)) circulating concentrations are mostly determined by genetic factors, in the majority of reports they have shown a correlation with the hepatic status and a significant decrease in HCC and liver cirrhosis patients than among the controls. In such a way, Lp(a) may represent a new additional and useful marker for a more complete assessment and monitoring of the liver function in patients with HCC and liver cirrhosis. Further studies are needed in order to evaluate the clinical significance of Lp(a) in HCC.

Criticial limb ischemia: epidemiology

Critical limb ischemia is found in 12% of the U.S. adult population. Its clinical presentation varies from no symptoms to intermittent claudication, atypical leg pain, rest pain, ischemic ulcers, or gangrene. Those with critical limb ischemia have a high incidence of cardiovascular comorbidities that reflect a significant systemic atherosclerotic burden; they have increased functional impairment and increased rates of functional decline compared with persons without critical limb ischemia. Interventions for critical limb ischemia and the impact of major amputation have a significant social and economic impact. At 1 year, 25% of patients will be dead, 30% will have undergone amputation, and only 45% will remain alive with both limbs. At 5 years, more than 60% of patients with critical limb ischemia will be dead.

Novel markers of peripheral arterial disease

Peripheral arterial disease (PAD), a relatively common manifestation of atherosclerotic vascular disease, is associated with significant morbidity and mortality. Although conventional risk factors contribute to the onset and progression of PAD, the role of 'novel' biomarkers in pathways of inflammation, thrombosis, lipoprotein metabolism, and oxidative stress in determining susceptibility to PAD is being increasingly recognized. Validation of novel risk factors for PAD may allow earlier detection, an improved understanding of disease etiology and progression, and the development of new therapies. In this review, we discuss available evidence for associations between novel circulating markers and several aspects of PAD including disease susceptibility, progression, functional limitation, and adverse outcomes.

Ethnicity and peripheral artery disease

Peripheral arterial disease (PAD) is an important healthcare problem and is an indicator of widespread atherosclerosis in other vascular territories, such as the cerebral and coronary circulations. PAD is associated with considerable morbidity and mortality. Most population-based studies investigating PAD prevalence and risk factors for its development and progression have been based on predominantly White ethnic groups. Much less is known about the characteristics of this disease in other ethnic groups. Understanding the epidemiology of PAD amongst ethnic minority groups is relevant, given that the population of minority ethnic groups in countries such as the United Kingdom rose by 53% between 1991 and 2001 and is expected to rise further in the future. This article aims to provide an overview of possible pathophysiological differences between ethnic groups for PAD, focussing predominantly on South Asians (people originating from India, Bangladesh and Pakistan) and Blacks (people of Black Caribbean and Black African descent) as these groups comprise the majority of all ethnic minorities in the United Kingdom.

Serum lipoprotein(a) levels in patients with atherosclerotic peripheral vascular disease in Hospital Kuala Lumpur

OBJECTIVE

The objective of this study was to determine the proportion of patients with atherosclerotic peripheral vascular disease (PVD) who had elevated lipoprotein(a) [Lp(a)] levels, as well as to determine the latter's significance as a risk factor for PVD in the local population.

METHODS

This case-controlled study was conducted between June and October 2004 in the Department of Surgery, Kuala Lumpur Hospital. A total of 100 patients were recruited and divided into control and PVD groups. Patients were defined as having PVD if they were symptomatic, with ankle-brachial systolic index < 0.90, or by radiological evidence. Lp(a) concentrations were determined using immunoturbidometry. Absorbance of reaction precipitate was measured by spectrophotometry to give Lp(a) concentration in grams per litre (g/L). The reference value for normal Lp(a) levels was < or = 0.36 g/L.

RESULTS

Mean Lp(a) levels for control and PVD groups were 0.29 g/L and 0.56 g/L, and median values were 0.17 g/L and 0.48 g/L, respectively. Elevated Lp(a) levels in the control group was 26% compared to 58% in the PVD group. Analysis with Pearson's chi-squared test achieved a significant p value of 0.001. Multivariate analysis showed that elevated Lp(a) levels contributed significantly to the probability of having PVD with an odds ratio of 7.69.

CONCLUSION

Elevated serum Lp(a) has a significant role as a risk factor for atherosclerotic PVD in the local population.

The role of fibrinogen and fibrinolysis in peripheral arterial disease

Peripheral arterial disease (PAD) is associated with high rates of cerebrovascular and cardiovascular events; PAD is a marker of systemic atherosclerosis. As a result, standard therapy for all PAD patients should be directed at both peripheral and systemic atherosclerosis. Modification of established risk factors in the form of smoking cessation, correcting hypertension, optimizing diabetic control and normalizing lipids is essential. Furthermore, novel risk factors have emerged including fibrinogen and other hemostatic factors. Fibrinogen is a coagulation factor and a marker of the acute phase response (inflammation), a platelet activator, a major determinant of plasma viscosity and a component of the atherosclerotic plaque. Fibrinogen appears not only to predict the severity of PAD, but also serves as a marker for future development of PAD. Whether reducing the levels of fibrinogen and other coagulation factors will decrease the incidence and progression of PAD remains to be resolved. This review summarizes the role of fibrinogen in the pathogenesis of PAD and its association with other hemostatic factors. The role of fibrinolysis in patients with PAD is also considered.

Novel and traditional cardiovascular risk factors for peripheral arterial disease in incident-dialysis patients

Peripheral arterial disease (PAD), which threatens limb viability and patient survival, is increasing in frequency in the dialysis population, but associated risk factors remain poorly defined. We conducted a cross-sectional analysis of the association of novel and traditional cardiovascular risk factors with PAD in incident-dialysis patients enrolled in the CHOICE study by application of multivariate logistic-regression models with adjustment for confounders. Risk factors were determined by interview, record review, and laboratory analysis of frozen specimens. Among 922 patients, 25% had a diagnosis of PAD. After adjustment, higher prevalence of PAD was associated with increasing age (odds ratio [OR], 95% CI = 1.28 [range: 1.12 to 1.48] per 10-year increase in age); presence of diabetes mellitus (OR, 95% CI = 2.76 [range: 1.72 to 4.42]); higher Index of Co-Existent Disease (ICED), ICED 2 and ICED 3 versus ICED 0-1, (OR, 95% CI = 2.04; [range: 1.24 to 3.35] and OR, 95% CI = 2.81 [range: 1.83 to 4.30], respectively). After adjustment, we found no statistically significant association between CRP and prevalence of PAD. The prevalence of PAD diagnosis was 34% higher per quartile increase in Lp(a) (OR, 95% CI = 1.34 [range: 1.13 to 1.59]). Similarly, the prevalence of PAD diagnosis was 19% higher per quartile increase in total homocysteine (OR, 95% CI = 1.19 [range: 1.05 to 1.35]). The prevalence of PAD is high in incident-dialysis patients and is associated with several novel and traditional cardiovascular risk factors. This study identifies several novel risk factors (eg, Lp(a) and total homocysteine) and underscores the need for further research to reduce the burden of PAD in this high-risk group of patients.

Association of novel risk factors with the ankle brachial index in African American and non-Hispanic white populations

OBJECTIVES

To investigate whether novel risk factors, including C-reactive protein (CRP), fibrinogen, lipoprotein(a) [Lp(a)], and homocysteine levels, are associated with the ankle brachial index (ABI) in African American and non-Hispanic white populations and whether novel risk factors account for ethnic differences in peripheral arterial disease (PAD).

PARTICIPANTS AND METHODS

Between December 2000 and October 2004, original participants in the Genetic Epidemiology Network of Arteriopathy study returned for a second study visit to undergo measurement of risk factors and ABI. The CRP, Lp(a), and homocysteine levels were log transformed to reduce skewness. Multivariable regression analyses were used to assess whether a novel risk factor was associated with ABI after adjustment for conventional risk factors and whether ethnicity was associated with PAD (ABI, <or=0.95) after adjustment for conventional and novel risk factors.

RESULTS

Of 2229 study participants, the ABI was determined in 1395 African American participants (mean +/- SD age, 63 +/- 9 years; 71% women) and 834 white participants (mean +/- SD age, 58 +/- 9 years; 62% women) who belonged to hypertensive sibships. The mean ABI was lower in African American than in white individuals (0.99 +/- 0.1 vs 1.13 +/- 0.1; P < .001). In both ethnic groups, higher levels of CRP, fibrinogen, and homocysteine were each associated with a lower ABI after adjustment for conventional risk factors. In African American participants, the Lp(a) level was also significantly associated with the ABI. African American ethnicity was associated with the presence of PAD after adjustment for conventional risk factors (men: odds ratio [OR], 3.04; 95% confidence interval [CI], 1.80-5.15; women: OR, 2.82; 95% CI, 1.85-4.29), but the risk was significantly attenuated after additional adjustment for novel risk factors (men: OR, 2.11; 95% CI, 1.21-3.70; women: OR, 1.98; 95% CI, 1.26-3.11).

CONCLUSION

Novel risk factors are associated with interindividual variation in ABI in African American and non-Hispanic white populations and partly account for the increased risk of PAD associated with African American ethnicity.

Plasma Lipoprotein(a) Indicates Risk for 4 Distinct Forms of Vascular Disease

Background: Increased lipoprotein(a) [Lp(a)] concentrations are predictive for coronary artery disease (CAD). The risk conferred by Lp(a) for other types of vascular disease compared with CAD has not been investigated within a single population. This study aimed to investigate Lp(a) risk association for 4 different types of vascular disease (including CAD) within a predominantly white population.

Methods: We used an Lp(a) ELISA that measures Lp(a) independently of apolipoprotein(a) size to measure plasma Lp(a) in patients [384 CAD, 262 peripheral vascular disease, 184 ischemic stroke (stroke), 425 abdominal aortic aneurysm] and 230 disease-free controls. We then conducted association studies with logistic regression, integrating the potential confounding effects of age, sex, diabetes, plasma lipids, and a history of previous hypertension, hypercholesterolemia, and smoking.

Results: Multivariate analyses with Lp(a) concentrations of &gt;45 nmol/L (the 75th percentile value for controls) as the clinical cutoff showed increased Lp(a) concentrations to be a risk factor for all disease groups, with adjusted odds ratios ranging from 1.96 [95% confidence interval (CI) 1.24–3.08] for CAD to 2.33 (95% CI 1.39–3.89) for PVD. The risk conferred by Lp(a) appeared to be independent of other confounders, including exposure to statin/fibrate therapies. Similar odds ratios and CIs between disease groups indicated that increased Lp(a) conferred a similar risk for all groups studied.

Conclusions: Lp(a) constitutes a stable risk factor of similar magnitude for 4 major forms of vascular disease. This association was not altered by exposure to standard lipid-lowering therapy.

Arginyl-glycyl-aspartyl (RGD) epitope of human apolipoprotein (a) inhibits platelet aggregation by antagonizing the IIb subunit of the fibrinogen (GPIIb/IIIa) receptor

An unknown epitope of apolipoprotein (a) antagonizes fibrinogen binding to agonist-stimulated platelet's fibrinogen (GPIIb/IIIa) receptor yielding lipoprotein (a) mediated decreased platelet aggregation. The purpose of this study was to test the hypothesis that human apolipoprotein (a)'s single arginyl-glycyl-aspartyl (RGD) epitope, unique to apolipoprotein (a) in lipoprotein (a) binds to the RGD binding motif on the IIb subunit of the GPIIb/IIIa receptor thus reducing platelet-bound fibrinogen and consequently decreasing agonist-stimulated platelet aggregation. Platelets (N=30 subjects) were prepared from fresh plasma, washed three times in Tyrode's buffer and stimulated using 10 microM ADP or 2 microg/ml collagen. Lipoprotein (a) was isolated from plasma using lectin affinity chromatography followed by ultracentrifugation. The peptide RGDS inhibited (125)I-labelled lipoprotein (a) binding to autologous platelets with IC-50's of 25.1+/-2.2 (mean+/-SEM) and 15.4+/-1.3 microM for collagen- and ADP-stimulation respectively. Further, RGDS reduced platelet binding of (125)I-labelled fibrinogen IC-50's of 35.5+/-3.2 (mean+/-SEM) and 20.7+/-2.2 microM for collagen- and ADP-stimulation respectively. The monoclonal antibody PAC-1, uniquely directed at the RGD binding motif on the IIb subunit on collagen- and ADP-stimulated platelets, inhibited binding of (125)I-labelled lipoprotein (a) with IC-50's of 6.4+/-0.7 and 2.5+/-2.2 microg/10(8) platelets for collagen- and ADP-stimulation respectively. Additionally, PAC-1 reduced platelet bound of (125)I-labelled fibrinogen with IC-50's of 9.0+/-1.4 and 4.1+/-2.2 microg/10(8) platelets for collagen- and ADP-stimulation respectively. In a dose-related fashion, a polyclonal antibody, specific for the RGD epitope on apolipoprotein (a), restored platelet aggregation to control levels, inhibited (125)I-labelled lipoprotein (a) binding, and increased (125)I-labelled fibrinogen by displacing lipoprotein (a) from the GPIIb/IIIa receptor. Thus a never before demonstrated aspect of the mechanism of lipoprotein (a)'s suggested novel role as an endogenous regulator of fibrinogen binding to collagen- and ADP-stimulated platelets has been shown. In conclusion, lipoprotein (a), via apolipoprotein (a)'s RGD epitope, binds to the RGD binding motif on the IIb protein of the GPIIb/IIIa receptor consequently reducing platelet-bound fibrinogen which results in decreased platelet aggregation.

Metabolic disorders in patients with psoriasis and psoriatic arthritis

Psoriasis is one of the common complex disorders in Western world, affecting 2% to 3% of the population. Recent studies indicate that psoriasis is associated with an increased risk of comorbidity and mortality compared to the general population. It appears that patients with psoriasis have a higher prevalence of metabolic disorders such as diabetes, hypertension, obesity, and hyperlipidemia, as well as a higher frequency of cigarette smoking. These concomitant diseases can complicate the treatment of psoriasis. Even though the etiology of these associations is elusive, physicians should be aware of them and take active steps to reduce the risk profiles of patients with psoriasis and psoriatic arthritis, in order to lessen mortality and comorbidity.

Relationship of smoking and smoking cessation with ankle-to-arm blood pressure index in elderly Japanese men

BACKGROUND

Cigarette smoking is associated with an increased risk of peripheral arterial disease, but the relationship between smoking cessation and preclinical peripheral atherosclerosis is uncertain.

DESIGN AND METHODS

A cross-sectional, population-based study to examine the effect of smoking and smoking cessation on the prevalence of peripheral arterial disease among 1215 men aged 60-79 years in two Japanese communities in 1999-2000. The ankle-to-arm systolic blood pressure index (AAI) was used as an estimate of the presence of peripheral atherosclerosis.

RESULTS

The mean AAI correlated inversely and linearly with smoking status and pack-years of smoking. The multivariate prevalence odds ratio [95% confidence interval (CI)] of low AAI (< 0.90) compared with never-smokers was 3.7 (95% CI 1.1-12.7) for current smokers and 4.2 (95% CI 1.2-14.6) for men with 45 or more pack-years of smoking. In men who have quit smoking for 20 years or more, the mean AAI was higher and the prevalence of low AAI (< 0.90) was lower than those of current smokers, but similar to those of never-smokers.

CONCLUSIONS

Our results confirm that current smoking and pack-years of smoking correlate with the presence of peripheral artery disease. The results suggest that smoking cessation for 20 years or more is associated with the regression of atherosclerosis in peripheral arteries. This finding needs to be confirmed by a prospective study.

Statins and Peripheral Arterial Disease: Potential Mechanisms and Clinical Benefits

Peripheral arterial disease (PAD) is a manifestation of widespread atherosclerosis. Lipid modification (especially with statins) is a component of the treatment of patients with PAD since this condition is considered a coronary heart disease equivalent. This review considers the mechanism of action of statins in PAD. Statins have been shown to reduce the incidence of new coronary events in patients with PAD. However, surveys suggest that many such patients remain undertreated. Statins can also increase walking distance in patients with PAD. There is also evidence that statins can improve renal function in these patients. Several other actions of statins are considered in this review. PAD patients have an increased morbidity and mortality, largely due to myocardial infarction and stroke. Recognizing and treating these high-risk patients as early as possible should be a priority.

Phenotypic and genotypic risk factors for cardiovascular events in an incident dialysis cohort

Cardiovascular disease (CVD) remains the major cause of death in patients with end-stage renal disease (ESRD). Traditional risk factors do not explain the high prevalence of CVD in this population, and other non-traditional cardiovascular (CV) risk markers have now been described. Therefore, the potential relationship between CVD and phenotypic and genotypic risk markers was investigated prospectively in incident dialysis patients cohort. The 279 patients (244 on hemodialysis, 35 on peritoneal dialysis) within the Diamant Alpin Dialysis Cohort Study were investigated. Phenotypic and genotypic parameters were determined at dialysis initiation, patients monitored over a 2-year period, and CV events (morbidity and mortality) recorded. Globally, 82 CV events occurred and 26 patients (9.3%) died from CVD, whereas 28 (10%) died from non-CV causes. Previous CV events were strongly predictive of CV events occurrence, whatever patients had had one (hazard ratio (HR) 2, 95% confidence intervals (CI) 1.1-3.5) or more (HR 3.9, 95% CI 2.1-7.1) CV accidents before starting dialysis. Both lipoprotein(a) (HR 1.67, 95% CI 1-2.5) and total plasma homocysteine at cutoff 30 micromol/l (HR 1.7, 95% CI 1.1-2.8) were independent predictors of CV events outcome. In the subgroup of patients with homocysteine < 30 micromol/l, methylenetetrahydrofolate reductase (MTHFR) TT was the sole biological parameter predictive of CV event outcome (HR 2.5, 95% CI 1.1-10, P = 0.03). ESRD patients who enter chronic dialysis with a previous CV event, high total homocysteinemia levels, or MTHFR 677TT genotype must be considered at high risk of incident CV events.

Risk factors for progression of peripheral arterial disease in large and small vessels

BACKGROUND

Data on the natural history of peripheral arterial disease (PAD) are scarce and are focused primarily on clinical symptoms. Using noninvasive tests, we assessed the role of traditional and novel risk factors on PAD progression. We hypothesized that the risk factors for large-vessel PAD (LV-PAD) progression might differ from small-vessel PAD (SV-PAD).

METHODS AND RESULTS

Between 1990 and 1994, patients seen during the prior 10 years in our vascular laboratories were invited for a new vascular examination. The first assessment provided baseline data, with follow-up data obtained at this study. The highest decile of decline was considered major progression, which was a -0.30 ankle brachial index decrease for LV-PAD and a -0.27 toe brachial index decrease for SV-PAD progression. In addition to traditional risk factors, the roles of high-sensitivity C-reactive protein, serum amyloid-A, lipoprotein(a), and homocysteine were assessed. Over the average follow-up interval of 4.6+/-2.5 years, the 403 patients showed a significant ankle brachial index and toe brachial index deterioration. In multivariable analysis, current smoking, ratio of total to HDL cholesterol, lipoprotein(a), and high-sensitivity C-reactive protein were related to LV-PAD progression, whereas only diabetes was associated with SV-PAD progression.

CONCLUSIONS

Risk factors contribute differentially to the progression of LV-PAD and SV-PAD. Cigarette smoking, lipids, and inflammation contribute to LV-PAD progression, whereas diabetes was the only significant predictor of SV-PAD progression.

Increased prevalence of peripheral arterial disease in osteoporotic postmenopausal women

The aim of this study was to investigate the prevalence and correlates of peripheral arterial disease (PAD) in a population of osteoporotic postmenopausal women. The presence of PAD was assessed by ankle brachial index (ABI) in 345 ambulatory osteoporotic postmenopausal women, and in 360 community-based, age- and race-matched postmenopausal women with normal bone mineral density (BMD) (control group). PAD was detected in 63/345 (18.2%) osteoporotic women and in 14/360 (3.8%) control subjects (P < 0.0001). The mean ABI values were significantly lower in the osteoporosis group than in the control group (0.98 +/- 0.09 vs. 1.04 +/- 0.06, P < 0.0001). No difference in cardiovascular risk factors was observed between osteoporotic patients and controls, or between osteoporotic patients with and without PAD. Osteoporotic patients with PAD had lower femoral neck BMD T scores than those without PAD (-4.2 +/- 0.7 vs. -2.3 +/- 0.7, P < 0.0001). Only 4 PAD patients (5.1%) had intermittent claudication. In multivariate logistic regression analysis, factors independently associated with PAD within osteoporotic patients were lower femoral neck BMD T score (odds ratio (OR) = 0.20, 95% confidence interval (CI), 0.05-0.70, P = 0.01) and systolic blood pressure (OR = 1.02, 95% CI, 1.00-1.03, P = 0.01). This study shows for the first time an increased prevalence of PAD among osteoporotic postmenopausal women, with a lower femoral neck BMD T score being a significant independent predictor. The findings suggest that vascular status evaluation should be done in osteoporotic postmenopausal women in order to identify candidate patients for preventive and therapeutic cardiovascular interventions.

Diabetes treatments have differential effects on nontraditional cardiovascular risk factors

OBJECTIVE

The aim of this study was to determine the effect of basal insulin, alone or with a sensitizer, or a combination of oral agents on nontraditional risk factors for cardiovascular disease (CVD).

RESEARCH DESIGN AND METHODS

We randomized 57 patients with T2DM to either (1) continuous subcutaneous basal Lispro insulin at a single rate using an insulin pump (basal insulin) or (2) basal insulin and oral pioglitazone 30 mg daily (basal insulin +Pio) or (3) a sulfonylurea and metformin (SU+M). We measured glycosylated hemoglobin (HbA1c), plasma high-sensitivity C-reactive protein (hs-CRP), plasminogen activator inhibitor-1 (PAI-1), 8-epi-prostaglandin F2 alpha (PGF2alpha), serum lipoprotein (a) [Lp (a)], and lipoprotein profile at baseline and after 20 weeks of treatment.

RESULTS

HbA1c decreased by >or=2% (P<.001) and to comparable levels (P=NS) in all groups. Despite improved glycemia, hsCRP did not change in any group, whereas plasma PAI-1 fell with basal insulin +Pio (P<.02) and SU+M (P<.01). PGF2alpha declined with basal insulin (P<.02) and SU+M (P<.001). High-density lipoprotein cholesterol (HDL-C) increased only with basal insulin +Pio (18.2%, P<.05). Lp (a) increased with basal insulin therapy alone (P<.01). Data were pooled from all groups to determine the overall effect of glycemic control-there was a significant (P<.001) decline in HbA1c, PAI-1, and PGF2alpha and an increase in HDL-C (P<.001). There was no correlation between HbA1c reduction and changes in these parameters.

CONCLUSIONS

We conclude that excellent glycemic control per se does not impact nontraditional risk factors for CVD equally, but various diabetes medications have different effects on these risk factors. These findings may have implications for making appropriate therapeutic choices for patients with Type 2 diabetes, although larger studies with more appropriate treatment comparisons may be necessary.

Risk factors for peripheral arterial disease incidence in persons with diabetes: the Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Some risk factors for peripheral arterial disease (PAD) have been identified, but little information is available on PAD risk factors in individuals with diabetes.

METHODS

Using data from the Atherosclerosis Risk in Communities (ARIC) Study, we assessed the relation of traditional and non-traditional risk factors with the risk of PAD in 1651 participants with diabetes, but not PAD, at baseline. Incident PAD was defined as an ankle-brachial index (ABI)<0.9 assessed at regular examinations; hospital discharge codes for PAD, amputation, or leg revascularization; or claudication assessed by annual questionnaire.

RESULTS

Over a mean of 10.3 years of follow-up, 238 persons developed incident PAD identified, yielding a PAD event rate of 13.9 per 1000 person years. Adjusted for sex, age, race, and center, the risk of developing PAD was increased 1.87-fold (95% confidence interval (95% CI): 1.36-2.57) in persons who were current smokers versus non-smokers, 2.27-fold (95% CI: 1.57-3.26) for baseline coronary heart disease (CHD) versus no baseline CHD, and 1.75-fold (95% CI: 1.18-2.60) for the highest quartile versus lowest quartile of triglycerides. We found no evidence of an association with other blood lipids or hypertension. Compared with the lowest quartiles, comparably-adjusted relative risks for the highest quartiles were 1.60 (95% CI: 1.10-2.33) for waist-to-hip ratio, 2.52 (95% CI: 1.70-3.73) for fibrinogen, 1.70 (95% CI: 1.17-2.47) for factor VIII, 1.73 (95% CI: 1.18-2.54) for von Willebrand factor, 2.15 (95% CI: 1.43-3.24) for white blood cell count, 1.81 (95% CI: 1.19-2.74) for serum creatinine, 0.55 (95% CI: 0.37-0.83) for serum albumin, and 2.73 (95% CI: 1.77-4.22) for carotid intima-media thickness. Persons who had a prior history of diabetes and were taking insulin had a relative risk of 1.97 (95% CI: 1.35-2.87) for future PAD events, compared with those with newly identified diabetes at baseline. In our final multivariable model, current smoking, prevalent CHD, elevated fibrinogen and carotid IMT, and a prior history of diabetes with insulin treatment were independently associated with greater PAD incidence.

CONCLUSION

These markers might be useful to identify individuals with diabetes at particular risk for PAD.

Lipoprotein(a): an emerging cardiovascular risk factor

Lipoprotein(a) is a cholesterol-enriched lipoprotein, consisting of a covalent linkage joining the unique and highly polymorphic apolipoprotein(a) to apolipoprotein B100, the main protein moiety of low-density lipoproteins. Although the concentration of lipoprotein(a) in humans is mostly genetically determined, acquired disorders might influence synthesis and catabolism of the particle. Raised concentration of lipoprotein(a) has been acknowledged as a leading inherited risk factor for both premature and advanced atherosclerosis at different vascular sites. The strong structural homologies with plasminogen and low-density lipoproteins suggest that lipoprotein(a) might represent the ideal bridge between the fields of atherosclerosis and thrombosis in the pathogenesis of vascular occlusive disorders. Unfortunately, the exact mechanisms by which lipoprotein(a) promotes, accelerates, and complicates atherosclerosis are only partially understood. In some clinical settings, such as in patients at exceptionally low risk for cardiovascular disease, the potential regenerative and antineoplastic properties of lipoprotein(a) might paradoxically counterbalance its athero-thrombogenicity, as attested by the compatibility between raised plasma lipoprotein(a) levels and longevity.

Serum apolipoprotein AI levels in atherosclerotic and diabetic patients

OBJECTIVE

To evaluate the association between Apolipoprotein AI (ApoAI), Apolipoprotein B100 (ApoB) and the presence of lower limb atherosclerotic occlusive disease.

MATERIALS AND METHODS

Serum lipids, lipoprotein fractions, ApoAI, ApoB and Lp(a) were measured in 52 patients (28 diabetics and 24 non-diabetics) with lower limb occlusive disease. They were evaluated according to patients' glucose and compared with those in 75 healthy controls.

RESULTS

There was a significant decrease in HDL-cholesterol and ApoAI serum levels (p = 0.000001) and an increase in Lp(a) (p = 0.000001) in patients as compared to controls. No difference was observed in total cholesterol, non HDL-cholesterol or triglycerides. Multiple regression analysis revealed a significant association between low ApoAI (or HDL) levels and the disease as well as between high Lp(a) levels and the disease. ApoAI (p = 0.0003), HDL-cholesterol (p = 0.00005) and total cholesterol (p = 0.01) levels were significantly lower in diabetic patients compared to non-diabetic patients. Lp(a) levels did not correlate with fasting glucose concentration. Multiple regression analysis revealed a significant association between low ApoAI (or HDL) levels and diabetes.

CONCLUSION

Decreased ApoAI appears to be a main component of the dyslipidaemic serum profile observed in patients with atherosclerotic occlusive disease of the lower extremities. Increased Lp(a) levels is an independent risk factor. Decreased HDL-cholesterol is also involved in the dyslipidaemic profile.

Peripheral vascular disease risk factors among patients undergoing hemodialysis

Peripheral vascular disease (PVD) is common among patients undergoing hemodialysis, but little is known regarding the risk factors for PVD in this population. Data from waves 1, 3, and 4 of the United States Renal Data System Dialysis Morbidity and Mortality Study were used to examine cross-sectional associations of a range of conventional cardiovascular risk factors and uremia- or dialysis-related variables with PVD. Univariate and multivariate logistic regression models were developed using wave 3 and 4 data. Odds ratios for the multivariate model derived using wave 3 and 4 data were then compared with those obtained with the wave 1 data set. For both data sets, PVD was positively associated with the duration of dialysis (vintage) and malnourished status and was negatively associated with serum albumin and parathyroid hormone levels and predialysis diastolic BP. Kt/V was negatively associated with PVD in waves 3 and 4 but not in wave 1. PVD was associated with increasing age, white (versus non-white) race, male gender, diabetes mellitus, coronary artery disease, cerebrovascular disease, smoking, and left ventricular hypertrophy, as for the general population, but not with hypertension or hyperlipidemia. In conclusion, PVD among hemodialysis patients is associated with both dialysis-specific variables and most conventional cardiovascular risk factors other than hypertension and hyperlipidemia. Future studies should prospectively examine the association of these variables identified in cross-sectional analyses with the de novo development of PVD in this population.

Peripheral arterial disease

Lower extremity peripheral arterial disease (PAD) most frequently presents with pain during ambulation, which is known as "intermittent claudication". Some relief of symptoms is possible with exercise, pharmacotherapy, and cessation of smoking. The risk of limb-loss is overshadowed by the risk of mortality from coexistent coronary artery and cerebrovascular atherosclerosis. Primary therapy should be directed at treating the generalised atherosclerotic process, managing lipids, blood sugar, and blood pressure. By contrast, the risk of limb-loss becomes substantial when there is pain at rest, ischaemic ulceration, or gangrene. Interventions such as balloon angioplasty, stenting, and surgical revascularisation should be considered in these patients with so-called "critical limb ischaemia". The choice of the intervention is dependent on the anatomy of the stenotic or occlusive lesion; percutaneous interventions are appropriate when the lesion is focal and short but longer lesions must be treated with surgical revascularisation to achieve acceptable long-term outcome.

Lipoprotein (a) level and mortality in patients with critical lower limb ischaemia

OBJECTIVE

to investigate if serum lipoprotein (a) level is a predictor of survival in patients with lower limb atherosclerotic occlusive disease.

DESIGN

prospective follow up study.

METHODS

demographic, biochemical and disease variables were collected prospectively in 441 patients with lower limb arterial occlusive disease. Survival data were obtained at a mean follow up of 44 months, and significant risk factors identified by the life table method and multivariate Cox regression analysis.

RESULTS

the cumulative survival for all patients at three and five years was 79% and 63%. Lipoprotein (a) level was the only significant independent biochemical predictor for all deaths and cardiorespiratory deaths on multivariate analysis, along with age, diabetes mellitus, renal impairment, cardiac diseases and major amputation. An elevated Lipoprotein(a) level of >24 mg/dl incurred a 107% and 45% increase in mortality at three and five years respectively. The higher mortality associated with elevated Lipoprotein (a) was particularly evident in patients with critical ischemia, in whom three and five year survival was reduced from 85% to 63% and 67% to 53% (p=0.0064). In claudicants a survival discrepancy was manifested only after five years (73% vs 62%), and the overall association did not reach statistic significance (p=0.52).

CONCLUSIONS

lipoprotein (a) level is a reliable biochemical marker for survival in patients with critical ischemia where traditional atherosclerosis risk factors were prevalent.

Intermittent claudication: magnitude of the problem, patient evaluation, and therapeutic strategies

Intermittent claudication (IC), the symptom of exercise-induced muscle ischemia of peripheral arterial disease (PAD), afflicts and limits the activities of a significant number of patients. Incidence and prevalence of IC depends on the population studied and the diagnostic instruments used. In large studies, prevalence has ranged from 3% to 10%, with a sharp increase in those aged > or =70 years. Over the next 20 years, the total number of patients affected is expected to increase significantly due to anticipated demographic changes. Analysis of the natural history of IC demonstrates that the risk of cardiovascular morbidity and mortality far exceeds that of severe limb ischemia or limb loss. In fact, only 2% to 4% of all patients with IC will require a major amputation in their lifetime. However, life expectancy is approximately 10 years less than that of an age-matched cohort. By now, PAD is well recognized as a marker of systemic atherosclerosis. The cornerstone of patient evaluation is a history and physical examination, including a detailed atherosclerotic risk-factor assessment. In the differential diagnosis of IC, clinicians should consider etiologies such as arthritis, spinal stenosis, radiculopathy, venous claudication, or inflammatory processes. In >80% of all patients, it is possible to locate the responsible arterial segment by combining the location and severity of pain with a pulse examination. Noninvasive diagnostic studies help determine the level of disease, may unmask a hemodynamically significant stenosis, and are useful in follow-up. Arteriography is reserved for patients in whom the decision for revascularization has been made. Knowing the anatomic detail of a lesion allows the clinician to determine whether and what type of intervention is feasible. Standard therapy for all patients should be directed at both peripheral and systemic atherosclerosis, beginning with risk-factor modification in the form of smoking cessation, optimal diabetes control, and lipid normalization. The benefits of supervised exercise rehabilitation include significantly increased walking distance and enhanced quality of life. Platelet inhibition has been shown to reduce the risk of ischemic stroke, myocardial infarction, and vascular death and should be prescribed for all but those in whom it is medically contraindicated. Symptom-specific pharmacotherapy with a broad range of medications has yielded disappointing results in the past. However, recent studies have demonstrated that patients receiving the novel agent cilostazol experienced increases in walking distance and improvements in quality of life.

Lipoprotein (a) and stroke

Strokes are one of the most common causes of mortality and long term severe disability. There is evidence that lipoprotein (a) (Lp(a)) is a predictor of many forms of vascular disease, including premature coronary artery disease. Several studies have also evaluated the association between Lp(a) and ischaemic (thrombotic) stroke. Several cross sectional (and a few prospective) studies provide contradictory findings regarding Lp(a) as a predictor of ischaemic stroke. Several factors might contribute to the existing confusion--for example, small sample sizes, different ethnic groups, the influence of oestrogens in women participating in the studies, plasma storage before Lp(a) determination, statistical errors, and selection bias. This review focuses on the Lp(a) related mechanisms that might contribute to the pathogenesis of ischaemic stroke. The association between Lp(a) and other cardiovascular risk factors is discussed. Therapeutic interventions that can lower the circulating concentrations of Lp(a) and thus possibly reduce the risk of stroke are also considered.

Serum Lp(a) lipoprotein levels in patients with atherosclerotic occlusive disease of the lower extremities

OBJECTIVE

To evaluate the association between Lp(a) lipoprotein levels, other serum lipids and the presence of lower limb atherosclerotic occlusive disease.

MATERIALS AND METHODS

Angiographic findings in 36 patients were related to serum Lp(a). Total cholesterol, triglycerides, LDL-cholesterol, HDL-cholesterol and Lp(a) levels were compared with those of 73 age- and sex-matched healthy controls.

RESULTS

Atheromatous lesions were localised in the femoropopliteal ( approximately 60%) and aortoiliac ( approximately 40%) segments. The number of stenosed arteries was > or =2 and the range of stenosis severity was between 40% and 100%. There was a significant increase in serum Lp(a) (p= 0.000001) and a decrease in serum HDL (p= 0.000009) levels in patients compared to controls. No difference was observed in total cholesterol, LDL-cholesterol or triglyceride. However, the ratio of total cholesterol/HDL-cholesterol was significantly higher (p= 0.005) in patients.

CONCLUSION

A dyslipidaemic serum profile, characterised by increased Lp(a) levels and decreased HDL-cholesterol levels, is associated with atherosclerotic occlusive disease of the lower extremities.