Is TRAP-6 suitable as a positive control for platelet reactivity when assessing response to clopidogrel?

Adenosine 5′-diphosphate (ADP) inducible aggregation is used to assess platelet response to thienopyridines. Thrombin receptor-activating peptide-6 (TRAP-6) inducible aggregation may serve as a positive control because it acts via the thrombin receptor protease-activating receptor-1, which is not blocked by thienopyridines. We therefore investigated if TRAP-6 is suitable as a positive control when assessing residual platelet reactivity to ADP. Platelet response to clopidogrel was assessed in 200 patients on dual antiplatelet therapy using ADP inducible platelet aggregation by light transmission aggregometry (LTA), multiple electrode aggregometry (MEA), and the shear-dependent Impact-R. Test specificities were monitored by TRAP-6 inducible platelet aggregation. The aggregation-independent vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay served for comparisons. ADP inducible aggregation was correlated to that by TRAP-6 (r = 0.33 to 0.72; p < 0.001 for all assays). A linear correlation was seen within MEA (r = 0.72). LTA TRAP-6 correlated weakly with the VASP assay (r = 0.19; p = 0.01), while there were no correlations of TRAP-6 responses by MEA or the Impact-R with the VASP assay (r = 0.03 and ?0.09; p > 0.05). In all three assays, differences between ADP and TRAP-6 inducible aggregation varied considerably. Within MEA, TRAP-6 inducible aggregation was almost always stronger than ADP inducible aggregation, while within LTA and the Impact-R, weak responses to ADP were associated with both, weak and strong responses to TRAP-6. In conclusion, the application of TRAP-6 as a positive control for platelet reactivity has major limitations and results need to be cautiously interpreted on an individual basis.     

Traitement du purpura thrombopénique immunologique : étude rétrospective de 40 patients

Purpose

Immune thrombocytopenia (ITP) is an auto-immune disease associating a peripheral platelet destruction without increased central production.

Methods

Forty patients with chronic ITP were retrospectively analyzed for clinical and biological presentation and response to treatment.

Results

Mean age at diagnosis was 54 years. ITP was revealed by hemorrhage in 65 % of the patients. Despite very low platelet count, no life threatening hemorrhage was observed. Platelet associated antibodies were found in 66 %, usually directed against GPIIb/IIIa. Corticosteroids were used as first line treatment, with response in 54 %, and relapse in 86 %. A response was observed in 42.1 % with dapsone, which was well tolerated, a relapse occurring in 37.5 % of the patients. Rituximab (RTX) allowed a response rate of 42.1 %, prolonged in 40 % of the patients. A response was achieved in 42.9 % cases after splenectomy, without any relapse. No factor was identified to predict the response to treatment.

Conclusion

ITP is a rare disorder occurring most frequently in middle aged patients. Because of high relapse or no response rates, many treatments should be used. Dapsone offers a good efficacy without major side effects. RTX is well tolerated and allows a good response rate. The use of new agents like thrombopoietin receptor agonist or new therapeutics against B lymphocytes should be defined.     

Residual platelet activation through protease-activated receptors (PAR)-1 and ‐4 in patients on P2Y12 inhibitors

Background

Dual antiplatelet therapy with aspirin and thienopyridines has improved outcomes of patients after coronary stent implantation. However, current knowledge suggests that thrombin generation is not affected by inhibition of the P2Y12 receptor, and therefore, platelet activation may still occur.

Methods

The response to agonists specific for protease-activated receptors (PAR)-1 and ‐4 was tested by multiple electrode impedance aggregometry in 82 patients on stable doses of clopidogrel or prasugrel, and in 55 healthy controls.

Results

Based on the consensus cut-off value for adenosine diphosphate (ADP) responsiveness, only one out of 19 patients on prasugrel, but 22 out of 63 patients on clopidogrel had high on-treatment residual platelet reactivity in response to exogenous ADP (p = 0.01). Among the patients with adequate ADP P2Y12 receptor inhibition (n = 59), we still observed 32 patients (54.2%) with normal response to the PAR-1 activator SFLLRN (26 patients on clopidogrel, 81.2%; 6 patients on prasugrel, 18.8%), and 37 patients (63.8%) with a normal response to the PAR-4 activator AYPGKF (29 patients on clopidogrel, 78.4%; 8 patients on prasugrel, 21.6%). The degree of PAR-agonists inducible platelet activation was directly correlated with the activation induced by ADP (r > 0.5 and p < 0.001 for both agonists). Moreover, SFLLRN and AYPGKF inducible platelet reactivities were strongly correlated (r = 0.75, p < 0.001).

Conclusion

PAR responsiveness is preserved in the majority of patients with adequate clopidogrel-mediated inhibition of the platelet P2Y12 receptor, and still in about 20% of those with adequate inhibition by prasugrel.     

MK-383 (Tirofiban) induces a GPIIb/IIIa receptor conformation which differs from the resting and activated receptor

The platelet integrin α_IIb β₃ (GPIIb/IIIa) acts as a receptor for fibrinogen, playing a critical role in platelet aggregation. GPIIb/IIIa antagonists, which block the receptor-ligand interaction, have been accused of causing occasional thrombocytopenia, probably via drug-induced platelet activation or immunogenic neoepitopes. We, therefore, analyzed the effects of the GPIIb/IIIa antagonist MK-383 (tirofiban) on platelet activation and GpIIb/IIIa conformation. At a concentration of 10^-7 mol/l, MK-383 completely inhibited fibrinogen binding to in vitro stimulated platelets. Simultaneously, the GPIIb/IIIa expression density increased, similar to that on activated platelets, but no effect on P-selectin expression or the formation of platelet-leukocyte aggregates could be observed, indicating that MK-383 binding did not induce general platelet activation. The GPIIb/IIIa receptor conformation was further analyzed by fluorescence resonance energy transfer analysis between fluorochrome-labeled antibodies against different GpIIb/IIIa epitopes. As a result, MK-383 induced a receptor conformation that differed from the resting as well as the activated receptor as induced by ADP or TRAP-6. This conformational modulation of GPIIb/IIIa presents an interesting mechanism which may be linked to receptor recruitment without inducing general platelet activation.     

MK-383 (tirofiban) induces a GPIIb/IIIa receptor conformation which differs from the resting and activated receptor

The platelet integrin alphaIIb beta3 (GPIIb/IIIa) acts as a receptor for fibrinogen, playing a critical role in platelet aggregation. GPIIb/IIIa antagonists, which block the receptor-ligand interaction, have been accused of causing occasional thrombocytopenia, probably via drug-induced platelet activation or immunogenic neoepitopes. We, therefore, analyzed the effects of the GPIIb/IIIa antagonist MK-383 (tirofiban) on platelet activation and GpIIb/IIIa conformation. At a concentration of 10(-7) mol/l, MK-383 completely inhibited fibrinogen binding to in vitro stimulated platelets. Simultaneously, the GPIIb/IIIa expression density increased, similar to that on activated platelets, but no effect on P-selectin expression or the formation of platelet-leukocyte aggregates could be observed, indicating that MK-383 binding did not induce general platelet activation. The GPIIb/IIIa receptor conformation was further analyzed by fluorescence resonance energy transfer analysis between fluorochrome-labeled antibodies against different GpIIb/IIIa epitopes. As a result, MK-383 induced a receptor conformation that differed from the resting as well as the activated receptor as induced by ADP or TRAP-6. This conformational modulation of GPIIb/IIIa presents an interesting mechanism which may be linked to receptor recruitment without inducing general platelet activation.     

Agonist-inducible platelet activation in chronic idiopathic autoimmune thrombocytopenia

OBJECTIVE: There are only few studies on agonist-inducible platelet activation in chronic idiopathic autoimmune thrombocytopenia (cAITP). MATERIALS AND METHODS: We compared agonist (TRAP-6, ADP, Arachidonic acid, Epinephrine, and Ristocetin) -inducible P-selectin expression and PAC-1 binding in 40 patients with cAITP (f/m ratio 23/17) with those in 20 healthy controls. Results were correlated with platelet counts, detectable platelet antibodies, and reticulated platelets. RESULTS: The in vivo activation of platelets determined the in vitro inducible response to agonists. The stronger the in vivo activation the less the number of platelets responding to agonists, as illustrated by the inverse correlation of P-selectin expression ex vivo and the relative increase after the exogenous addition of agonists. The agonist-inducible platelet activation was not associated with the presence of detectable platelet antibodies to GPIb/IX or GPIIb/IIIa. Agonist-inducible platelet activation was also not correlated with counts of reticulated platelets. CONCLUSION: Agonist-inducible activation of platelets in cAITP is affected mainly by their in vivo activation.     

Comparison of cardiopulmonary exercise testing variables in COPD patients with and without coronary artery disease

Background

Coronary artery disease (CAD) is a common concomitant condition and an important cause of morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD). Since COPD and CAD can both independently cause reduced exercise capacity, it is reasonable to hypothesize that the combination of these diseases may compound the abnormalities observed during cardiopulmonary exercise testing (CPET). However, little is known about the impact of CAD on the CPET response in COPD patients. The aim of this study is to compare exercise capacity and gas exchange variables in COPD patients with and without CAD.

Methods

Fifty-four COPD subjects without CAD (COPDnoCAD) were matched to 54 COPD subjects diagnosed with CAD (COPD/CAD) according to age, gender, body mass index and severity of COPD. All subjects underwent resting pulmonary function and symptom-limited CPET.

Results

Comparing COPDnoCAD patients with COPD/CAD patients revealed that exercise capacity, as measured by % peak oxygen consumption (42 ± 16% vs 53 ± 19%, p = 0.002) and % peak wattage (23 ± 13% vs 32 ± 16%, p = 0.001), was significantly lower in COPD/CAD. Ventilatory response, as measured by VE/VCO₂ nadir (36 ± 9 vs 32 ± 5, p = 0.001), was significantly higher in COPD/CAD, with % peak VO₂ and VE/VCO₂ nadir correlating to % FEV₁ and inversely correlating with %DLCO.

Conclusion

COPD patients with CAD have significantly impaired CPET responses with lower exercise capacity and impaired gas exchange compared to COPD patients without CAD. These findings may affect the clinical interpretation of CPET data in COPD patients who have concomitant CAD.     

Low-grade albuminuria is associated with peripheral artery disease in Chinese diabetic patients

Background

Increasing studies have suggested that albuminuria might be an important risk factor for peripheral artery disease (PAD). However, studies focusing on the association between low-grade albuminuria and PAD are limited. It would be of great interest to elucidate the association between low-grade albuminuria and PAD in diabetic subjects.

Methods

A cross-sectional study was conducted in 1386 diabetic subjects (age ≥ 40 years) with normal urinary albumin levels from Shanghai, China. A first voided early morning spot urine sample was obtained for urinary albumin and creatinine measurements. Subjects were divided into three groups according to sex-specific cutoff points of urinary albumin–creatinine ratio (UACR) tertiles. Subjects in the upper tertile of UACR were classified as having low-grade albuminuria. PAD was defined by ankle–brachial index (ABI) <0.9 or >1.4.

Results

Overall, 106 (7.7%) of the study population had PAD. The prevalence of PAD in tertile 3 of UACR was higher than the prevalence in tertile 2 and tertile 1 (10.2%, 6.4% and 6.4%, respectively; P < 0.05). A fully adjusted logistic regression analysis revealed that compared with subjects in tertile 1 of normal UACR, those in tertile 3 had 1.7-fold increased risk for the presence of PAD.

Conclusions

In diabetic patients, high normal UACR level, which is below the current cutoff point of microalbuminuria, was associated with the increased prevalence of PAD. It suggested that low-grade albuminuria might be an early marker for the detection of PAD in diabetic patients.     

In Vivo and protease-activated receptor-1-mediated platelet activation in patients presenting for cardiac catheterization

Pathways of platelet activation that are not targeted by current antithrombotic therapy may be crucial for the development of ischemic events in patients undergoing coronary angiography. We therefore investigated whether in vivo and thrombin receptor activating peptide (TRAP)-stimulated platelet activation and monocyte-platelet aggregate (MPA) levels can serve as independent risk markers for adverse outcomes in aspirin-treated patients presenting for cardiac catheterization. In vivo and TRAP-stimulated platelet surface P-selectin, activated glycoprotein IIb/IIIa (GPIIb/IIIa) and MPA levels were determined in 682 consecutive patients undergoing cardiac catheterization and in 47 healthy controls. Two-year follow-up data were obtained from 562 patients. In vivo platelet surface P-selectin, activated GPIIb/IIIa and MPA levels were significantly higher in patients with angiographically-proven coronary artery disease than in healthy controls (all p≤0.02). Patients with an acute coronary syndrome (ACS; n=125) had significantly higher levels of in vivo MPA than patients without ACS (n=437; p=0.01). In the overall study population (n=562) the surface expression of P-selectin and activated GPIIb/IIIa, and the levels of MPA in vivo and in response to TRAP were similar in patients without and with subsequent ischemic events (all p>0.05). Similar results were obtained when only patients with angiographically-proven coronary artery disease (n=459), stent implantation (n=205) or ACS (n=125) were analyzed. Receiver-operating characteristic curve analyses did not reveal cut-off values for P-selectin, activated GPIIb/IIIa, and MPA levels for the prediction of ischemic events. In conclusion, in vivo and TRAP-stimulated platelet activation and MPA levels did not predict adverse ischemic outcomes in aspirin-treated patients presenting for cardiac catheterization.     

Association of borderline ankle-brachial index with mortality and the incidence of peripheral artery disease in diabetic patients

Objective

Peripheral artery disease (PAD) and diabetes mellitus are significant risk factors for all-cause death or cardiovascular death. PAD occurs more frequently in diabetic than in non-diabetic patients. However, the association of ankle-brachial index (ABI), especially borderline ABI, with clinical outcomes has not been fully elucidated in diabetic patients. This study aimed to investigate the association of ABI with mortality and the incidence of PAD in Japanese diabetic patients.

Methods

This observational study included 3981 diabetic patients (61.0 ± 11.8 years of age, 59.4% men), registered in the Kyushu Prevention Study for Atherosclerosis. Patients were divided into 3 groups according to the value of ABI at baseline: ABI ≤0.90 (abnormal ABI:354 patients), 0.91 ≤ ABI ≤ 0.99 (borderline ABI:333 patients), and 1.00 ≤ ABI ≤ 1.40 (normal ABI:3294 patients).

Results

Cumulative incidence of all-cause death was significantly higher in patients with abnormal and borderline ABI than in those with normal ABI (34.4% vs. 13.5%, P < 0.0001 and 26.1% vs. 13.5%, P < 0.0001, respectively). In multivariate analysis, the risks for all-cause death in patients with abnormal ABI (HR:2.16; 95%CI:1.46–3.14; P = 0.0002) and borderline ABI (HR:1.78; 95%CI:1.14–2.70; P = 0.01) were significantly higher than in those with normal ABI. The incidence of PAD was remarkably higher in patients with borderline ABI than in those with normal ABI (32.2% vs.9.6%, P < 0.0001). After adjustment, the risk for PAD was significantly higher in patients with borderline ABI than in those with normal ABI (HR:3.10; 95%CI:1.90–4.95; P < 0.0001).

Conclusions

Borderline ABI in diabetic patients was associated with significantly higher risks for mortality and PAD compared with normal ABI.     

Correlation between a positive family risk score and peripheral artery disease in one case-control and two population-based studies

Objective

To evaluate the association between a family history of cardiovascular and metabolic diseases or risk factors and the presence of peripheral artery disease (PAD).

Methods

Participants were recruited within one PAD case-control study (CAVASIC, n = 481) and two population-based studies (KORA-F3, n = 3118; KORA-F4, n = 1325). In the KORA studies, an ankle-brachial-index <0.9 and/or symptomatic claudication was defined as PAD. For myocardial infarction, stroke, diabetes mellitus, hypertension, PAD, and obesity, family risk scores (FamRS) were calculated taking into account the number and age of diseased parents and siblings and regressed on prevalent PAD or ankle-brachial-index.

Results

A significant association with PAD was found for family history of myocardial infarction and hypertension in a combined analysis of all studies and for family history of PAD in the case-control study. A combined family history score was derived from FamRS myocardial infarction, stroke, diabetes mellitus, hypertension and PAD. A positive family history of at least two and/or a strong positive family history of at least one of these diseases was found to be associated with increased risk of prevalent PAD in all three studies, even after adjustment for classical risk factors (OR = 1.93, 95%CI = [1.53–2.44], p = 2.6 × 10⁻⁸).

Conclusion

The presence of a positive family history for cardiovascular and metabolic diseases or risk factors was shown to be associated with the presence of PAD. A FamRS calculation tool that considers age and family size can guide a physician to perform extended examinations to prevent complications and progression of PAD.     

Impaired Responsiveness to the Platelet P2Y12 Receptor Antagonist Clopidogrel in Patients With Type 2 Diabetes and Coronary Artery Disease

Background

Several studies have shown that patients with diabetes mellitus (DM) exhibit an impaired response to clopidogrel. This may contribute to their increased risk of recurrent atherothrombotic events, despite the use of dual-antiplatelet therapy. The mechanisms for impaired clopidogrel response in DM patients have not been fully elucidated.

Objectives

The aim of this study was to explore the mechanisms for impaired clopidogrel-mediated platelet inhibition in patients with DM using a comprehensive methodological approach embracing both pharmacokinetic (PK) and pharmacodynamic (PD) assessments as well as ex vivo and in vitro investigations.

Methods

Patients (DM, n = 30; non-DM, n = 30) with stable coronary artery disease taking aspirin 81 mg/day and P2Y₁₂ antagonist naive were enrolled. Blood was collected before and at various times (0.5, 1, 2, 4, 6, and 24 h) after a 600-mg loading dose of clopidogrel. PD assessments included vasodilator-stimulated phosphoprotein, light transmission aggregometry, and VerifyNow P2Y₁₂ ex vivo, before and after dosing and following in vitro incubation with escalating concentrations (1, 3, and 10 μM) of clopidogrel’s active metabolite (Clop-AM). Exposure to Clop-AM was also determined.

Results

PD assessments consistently showed that during the overall 24-h study time course, residual platelet reactivity was higher in DM patients compared with non-DM patients. In vitro incubation with Clop-AM revealed altered functional status of the P2Y₁₂ signaling pathway in DM platelets as measured by vasodilator-stimulated phosphoprotein, but not with other PD assays. Clop-AM exposure was ∼40% lower in DM patients than in non-DM patients.

Conclusions

The present study suggests that among DM patients, impaired P2Y₁₂ inhibition mediated by clopidogrel is largely attributable to attenuation of clopidogrel’s PK profile. This is characterized by lower plasma levels of Clop-AM over the sampling time course in DM patients compared with non-DM patients and only modestly attributed to altered functional status of the P2Y₁₂ signaling pathway.     

Impaired responsiveness to clopidogrel and aspirin in patients with recurrent stent thrombosis following percutaneous intervention for peripheral artery disease

Patients with peripheral artery disease (PAD) following peripheral percutaneous transluminal angioplasty (PTA) with stent implantation are prone to stent thrombosis despite treatment with aspirin and clopidogrel. Impaired clopidogrel responsiveness is associated with increased risk of ischemic events in patients following coronary stent implantation. We sought to assess platelet responsiveness to clopidogrel and aspirin in patients with PAD and recurrent stent thrombosis. Platelet aggregation induced by 5 and 20?µmol/l adenosine diphosphate (ADP) and 0.5?mmol/l arachidonic acid (AA), together with platelet reactivity index (PRI) and serum thromboxane B₂ (TXB₂), were determined in 11 patients with PAD and a history of stent thrombosis (mean, 3.1?±?1.14) after PTA and in 15 patients with PAD with no such history, also in 11 controls with coronary artery disease (CAD) and previous stent thrombosis. Platelet aggregation to 5?µmol/l ADP was higher in subjects with PAD and stent thrombosis than in those without stent thrombosis (p?=?0.0003) and CAD subjects (p?=?0.002). Aggregation induced by 20?µmol/l ADP was higher in PAD group with stent thrombosis than in PAD subjects without thrombosis (p?=?0.004). The PAD group with stent thrombosis had higher AA-induced platelet aggregation than CAD controls (p?=?0.007) and serum TXB₂ concentrations higher than PAD group without thrombosis (p?=?0.002) and CAD group (p?=?0.02). Concluding, platelet responsiveness to clopidogrel and aspirin is impaired in patients with PAD and recurrent stent thrombosis following PTA, as compared with similar individuals with CAD, and PAD with no history of stent thrombosis. This indicates that atherosclerosis burden affects platelet function and might contribute to stent thrombosis following percutaneous intervention in peripheral arteries.     

Combined effects of fibrinogen genetic variability on atherosclerosis in patients with or without stable angina pectoris: Focus on the coagulation cascade and endothelial function

Background

Fibrinogen is a coagulation/inflammatory biomarker strongly associated with atherogenesis. Data have reported that the genetic variability on fibrinogen chains may affect the atherosclerotic process and the risk of coronary artery disease (CAD). We examined the combined effects of the G455A and the G58A fibrinogen genetic polymorphisms on prothrombotic profile, endothelial function and the risk of CAD in a Caucasian population.

Methods

We recruited 422 patients with angiographically documented CAD and 277 controls matched for age and gender. The two polymorphisms were genotyped by polymerase chain reaction and restriction endonuclease digestion. Fibrinogen and D-Dimers levels, as well as factors' (f) V, X activity were measured by standard coagulometry techniques. Endothelial function was assessed by the flow mediated dilatation (FMD) of the brachial artery.

Results

The two polymorphisms had no significant effect on the risk for CAD. Although the 58AA subjects had not significantly different levels of fibrinogen compared with the 58GG + GA in both groups (p = NS), we importantly found that the 455AA homozygosity was associated with increased fibrinogen levels not only in the control group (p = 0.035), but also in the CAD group (p < 0.001) compared to the G allele carriers. Moreover, both the 58AA (p = 0.016) and 455AA homozygotes (p = 0.022) presented with higher levels of D-Dimers in the CAD group. Interestingly, the 455AA homozygotes had increased fV activity in the CAD group (p = 0.048). However, no significant effects were observed on fX activity and FMD.

Conclusions

Both fibrinogen polymorphisms are capable to modify the atherosclerotic process via their effects on the coagulation cascade.     

Time from blood draw to multiple electrode aggregometry and association with platelet reactivity

Results from multiple electrode aggregometry (MEA) may vary according to pre-analytic factors. This study aimed to analyze the association of time from blood draw to MEA in patients undergoing percutaneous coronary intervention (PCI). In this observational single-center cohort study, platelet aggregation (aggregation units, U) was quantified by MEA (Multiplate Analyzer) after stimulation with adenosine diphosphate (ADP; final concentration [Fc] 6.4 μM), thrombin receptor activating peptide (TRAP; Fc 32 μM), or arachidonic acid (AA; Fc 0.5 mM) in patients treated with ASA and clopidogrel following PCI. High on-clopidogrel platelet reactivity (HPR) was defined as ADP-induced platelet aggregation ≥ 46 U. The manufacturer recommends performing the analysis within 30–180 min after blood draw. Patients were grouped according to the time from blood draw to MEA: 30–180 min, < 30 min, or > 180 min. Platelet function of 273 patients with coronary artery disease undergoing PCI with dual antiplatelet therapy was analyzed. The median age was 72 years (interquartile range, IQR 62–79) and 179 (66%) were male. Median ADP-, TRAP-, and AA-induced aggregation was 25 (IQR 18–36) U, 79 (IQR 63–96) U, and 12 (IQR 7–18) U, respectively. For those analyzed within 30–180 min from blood draw, no significant correlation of time from blood draw to MEA was observed 1) ADP (r = − 0.04, p = 0.51); 2) TRAP (r = − 0.06, p = 0.32); 3) AA (r = − 0.03, p = 0.67). In patients undergoing percutaneous coronary intervention and treated with dual antiplatelet therapy, the time from blood draw to multiple electrode aggregometry does not correlate with ADP- induced aggregation when the measurement occurred within the recommended time interval of 30–180 min after blood draw.

     

Validation of the association between a branched chain amino acid metabolite profile and extremes of coronary artery disease in patients referred for cardiac catheterization

Objective

To validate independent associations between branched-chain amino acids (BCAA) and other metabolites with coronary artery disease (CAD).

Methods

We conducted mass-spectrometry-based profiling of 63 metabolites in fasting plasma from 1983 sequential patients undergoing cardiac catheterization. Significant CAD was defined as CADindex ≥ 32 (at least one vessel with ≥95% stenosis; N = 995) and no CAD as CADindex ≤ 23 and no previous cardiac events (N = 610). Individuals (N = 378) with CAD severity between these extremes were excluded. Principal components analysis (PCA) reduced large numbers of correlated metabolites into uncorrelated factors. Association between metabolite factors and significant CAD vs. no CAD was tested using logistic regression; and between metabolite factors and severity of CAD was tested using linear regression.

Results

Of twelve PCA-derived metabolite factors, two were associated with CAD in multivariable models: factor 10, composed of BCAA (adjusted odds ratio, OR, 1.20; 95% CI 1.05–1.35, p = 0.005) and factor 7, composed of short-chain acylcarnitines, which include byproducts of BCAA metabolism (adjusted OR 1.30; 95% CI 1.14–1.48, p = 0.001). After adjustment for glycated albumin (marker of insulin resistance [IR]) both factors 7 (p = 0.0001) and 10 (p = 0.004) remained associated with CAD. Severity of CAD as a continuous variable (including patients with non-obstructive disease) was associated with metabolite factors 2, 3, 6, 7, 8 and 9; only factors 7 and 10 were associated in multivariable models.

Conclusions

We validated the independent association of metabolites involved in BCAA metabolism with CAD extremes. These metabolites may be reporting on novel mechanisms of CAD pathogenesis that are independent of IR and diabetes.     

Association between postprandial triglycerides and coronary artery disease detected by coronary computed tomography angiography

Background

Studies have demonstrated the association of severe anatomical coronary artery disease (CAD) with postprandial triglycerides (TG) concentrations. Nevertheless the relationship between less severe atherosclerosis plaque burden and postprandial TG is less established.

Objective

to study the relationship between postprandial TG and CAD detected by coronary computed tomographic angiography (CTA).

Material and methods

130 patients who underwent an oral fat tolerance test were enrolled (85 with CAD detected by CTA and 45 without). Postprandial lipemia was studied by measuring TG from T0h to T6h with 2-h intervals, and analyzed the TG change over time using a longitudinal multivariable linear mixed effects model with the log normal of the TG as the primary outcome.

Results

The majority of individuals with CAD had non-obstructive disease (63.3%) Patients with CAD had a slower clearance of postprandial TG change from 4 h to 6 h (p < 0.05) compared to patients without CAD. These results remained significant after adjustment for fasting TG and glucose, age, gender, body mass index, and waist circumference. However, those differences did not reach statistical significance after adjustment for fasting HDL-C.

Conclusion

Patients with mild (<25% lumen obstruction) and moderate CAD (25–50% lumen obstruction) detected by coronary CTA had an impaired postprandial metabolism, with a delayed TG clearance, when compared to individuals with no CAD. This difference was partially explained by the lower HDL-C. Thus, though postprandial TG may contribute to the development of CAD, this association is partially related to low HDL-C.     

Fibroblast growth factor 23, the ankle-brachial index,and incident peripheral artery disease in the Cardiovascular Health Study

Background

Fibroblast growth factor 23 (FGF23) has emerged as a novel risk factor for mortality and cardiovascular events. Its association with the ankle-brachial index (ABI) and clinical peripheral artery disease (PAD) is less known.

Methods

Using data (N = 3143) from the Cardiovascular Health Study (CHS), a cohort of community dwelling adults >65 years of age, we analyzed the cross-sectional association of FGF23 with ABI and its association with incident clinical PAD events during 9.8 years of follow up using multinomial logistic regression and Cox proportional hazards models respectively.

Results

The prevalence of cardiovascular disease (CVD) and traditional risk factors like diabetes, coronary artery disease, and heart failure increased across higher quartiles of FGF23. Compared to those with ABI of 1.1–1.4, FGF23 per doubling at baseline was associated with prevalent PAD (ABI < 0.9) although this association was attenuated after adjusting for CVD risk factors, and kidney function (OR 0.91, 95% CI 0.76–1.08). FGF23 was not associated with high ABI (>1.4) (OR 1.06, 95% CI 0.75–1.51). Higher FGF23 was associated with incidence of PAD events in unadjusted, demographic adjusted, and CVD risk factor adjusted models (HR 2.26, 95% CI 1.28–3.98; highest versus lowest quartile). The addition of estimated glomerular filtration and urine albumin to creatinine ratio to the model however, attenuated these findings (HR 1.46, 95% CI, 0.79–2.70).

Conclusions

In community dwelling older adults, FGF23 was not associated with baseline low or high ABI or incident PAD events after adjusting for confounding variables. These results suggest that FGF23 may primarily be associated with adverse cardiovascular outcomes through non atherosclerotic mechanisms.     

High-risk plaque in the superficial femoral artery of people with peripheral artery disease: Prevalence and associated clinical characteristics

Objective

We used magnetic resonance imaging (MRI) to study the prevalence and associated clinical characteristics of high-risk plaque (defined as presence of lipid-rich necrotic core [LRNC] and intraplaque hemorrhage) in the superficial femoral arteries (SFA) among people with peripheral artery disease (PAD).

Background

The prevalence and clinical characteristics associated with high-risk plaque in the SFA are unknown.

Methods

Three-hundred-three participants with PAD underwent MRI of the proximal SFA using a 1.5 T S platform. Twelve contiguous 2.5 mm cross-sectional images were obtained.

Results

LRNC was present in 68 (22.4%) participants. Only one had intra-plaque hemorrhage. After adjusting for age and sex, smoking prevalence was higher among adults with LRNC than among those without LRNC (35.9% vs. 21.4%, p = 0.02). Among participants with vs. without LRNC there were no differences in mean percent lumen area (31% vs. 33%, p = 0.42), normalized mean wall area (0.71 vs. 0.70, p = 0.67) or maximum wall area (0.96 vs. 0.92, p = 0.54) in the SFA. Among participants with LRNC, cross-sectional images containing LRNC had a smaller percent lumen area (33% ± 1% vs. 39% ± 1%, p < 0.001), greater normalized mean wall thickness (0.25 ± 0.01 vs. 0.22 ± 0.01, p < 0.001), and greater normalized maximum wall thickness (0.41 ± 0.01 vs. 0.31 ± 0.01, p < 0.001), compared to cross-sectional images without LRNC.

Conclusions

Fewer than 25% of adults with PAD had high-risk plaque in the proximal SFA using MRI. Smoking was the only clinical characteristic associated with presence of LRNC. Further study is needed to determine the prognostic significance of LRNC in the SFA.

Clinical trial registration—URL

http://www.clinicaltrials.gov. Unique identifier: NCT00520312.     

Relationship between nitroglycerine-induced vasodilation and clinical severity of peripheral artery disease

Objective

Nitroglycerine-induced vasodilation is usually used as a control test for flow-mediated vasodilation (FMD). However, nitroglycerine-induced vasodilation per se has also been reported to be impaired in patients with atherosclerosis. The purpose of this study was to determine the relationship between nitroglycerine-induced vasodilation and the clinical severity of peripheral artery disease (PAD).

Methods and results

We measured nitroglycerine-induced vasodilation and FMD in 144 subjects (mean age: 63.8 ± 15.1 years), including 32 PAD patients with critical limb ischemia (CLI group), 28 PAD patients without CLI (non-CLI group), 60 age- and sex-matched patients without established cardiovascular disease (at-risk group), and 24 healthy subjects (healthy group). Nitroglycerine-induced vasodilation was significantly impaired in the CLI group compared to that in the other three groups (healthy group, 16.0 ± 5.3%; at-risk group, 12.9 ± 3.8%; non-CLI group, 10.3 ± 5.1%; CLI group, 6.7 ± 3.9%; P < 0.05, respectively). Even after multivariate adjustment, the differences remained significant. On the other hand, FMD was significantly impaired in the at-risk, non-CLI, and CLI group compared with that in the healthy group (healthy group, 7.1 ± 2.9%; at-risk group, 3.4 ± 2.3%; non-CLI group, 3.5 ± 2.7%; CLI group, 3.0 ± 2.8%; P < 0.001, respectively), but the differences among the at-risk, non-CLI, and CLI groups were not significant. Multivariate analysis revealed that nitroglycerine-induced vasodilation (odds ratio: 0.77, 95% confidence interval [CI]: 0.61–0.97) and diabetes mellitus (odds ratio: 8.75, 95% CI: 1.74–44.2) were independent variables for CLI in PAD patients.

Conclusions

There was no significant difference in FMD between PAD patients with and those without CLI, but nitroglycerine-induced vasodilation was significantly smaller in PAD patients with CLI compared with those without CLI.