Circulating Progenitor Cells Identify Peripheral Arterial Disease in Patients With Coronary Artery Disease.

RATIONALE: Peripheral arterial disease (PAD) is a clinical manifestation of extracoronary atherosclerosis. Despite sharing the same risk factors, only 20% to 30% of patients with coronary artery disease (CAD) develop PAD. Decline in the number of bone marrow-derived circulating progenitor cells (PCs) is thought to contribute to the pathogenesis of atherosclerosis. Whether specific changes in PCs differentiate patients with both PAD and CAD from those with CAD alone is unknown. OBJECTIVE: Determine whether differences exist in PCs counts of CAD patients with and without known PAD. METHODS AND RESULTS: 1497 patients (mean age: 65 years; 62% men) with known CAD were identified in the Emory Cardiovascular Biobank. Presence of PAD (n=308) was determined by history, review of medical records, or imaging and was classified as carotid (53%), lower extremity (41%), upper extremity (3%), and aortic disease (33%). Circulating PCs were enumerated by flow cytometry. Patients with CAD and PAD had significantly lower PC counts compared with those with only CAD. In multivariable analysis, a 50% decrease in cluster of differentiation 34 (CD34+) or CD34+/vascular endothelial growth factor receptor-2 (VEGFR2+) counts was associated with a 31% (P=0.032) and 183% (P=0.002) increase in the odds of having PAD, respectively. CD34+ and CD34+/VEGFR2+ counts significantly improved risk prediction metrics for prevalent PAD. Low CD34+/VEGFR2+ counts were associated with a 1.40-fold (95% confidence interval, 1.03-1.91) and a 1.64-fold (95% confidence interval, 1.07-2.50) increases in the risk of mortality and PAD-related events, respectively. CONCLUSIONS: PAD is associated with low CD34+ and CD34+/VEGFR2+ PC counts. Whether low PC counts are useful in screening for PAD needs to be investigated.

Circulating progenitor cells and outcomes in patients with coronary artery disease.

BACKGROUND: Low quantities of circulating progenitor cells (CPCs), specifically CD34+ populations, reflect impairment of intrinsic regenerative capacity. This study investigates the relationship between subsets of CPCs and adverse outcomes. METHODS: 1366 individuals undergoing angiography for evaluation of coronary artery disease (CAD) were enrolled into the Emory Cardiovascular Biobank. Flow cytometry identified CPCs as CD45med blood mononuclear cells expressing the CD34 epitope, with further enumeration of hematopoietic CPCs as CD133+/CXCR4+ cells and endothelial CPCs as vascular endothelial growth factor receptor-2 (VEGFR2+) cells. Adjusted Cox or Fine and Gray's sub-distribution hazard regression models analyzed the relationship between CPCs and 1) all-cause death and 2) a composite of cardiovascular death and non-fatal myocardial infarction (MI). RESULTS: Over a median 3.1-year follow-up period (IQR 1.3-4.9), there were 221 (16.6%) all-cause deaths and 172 (12.9%) cardiovascular deaths/MIs. Hematopoietic CPCs were highly correlated, and the CD34+/CXCR4+ subset was the best independent predictor. Lower counts (≤median) of CD34+/CXCR4+ and CD34+/VEGFR2+ cells independently predicted all-cause mortality (HR 1.46 [95% CI 1.06-2.01], p = 0.02 and 1.59 [95% CI 1.15-2.18], p = 0.004) and cardiovascular death/MI (HR 1.50 [95% CI 1.04-2.17], p = 0.03 and 1.47 [95% CI 1.01-2.03], p = 0.04). A combination of low CD34+/CXCR4+ and CD34+/VEGFR2+ CPCs predicted all-cause death (HR 2.1, 95% CI 1.4-3.0; p = 0.0002) and cardiovascular death/MI (HR 2.0, 95% CI 1.3-3.2; p = 0.002) compared to those with both lineages above the cut-offs. CONCLUSIONS: Lower levels of hematopoietic and endothelial CPCs indicate diminished endogenous regenerative capacity and independently correlate with greater mortality and cardiovascular risk in patients with CAD.

Aggregate Clinical and Biomarker-Based Model Predicts Adverse Outcomes in Patients With Coronary Artery Disease.

Despite guideline-based therapy, patients with coronary artery disease (CAD) are at widely variable risk for cardiovascular events. This variability demands a more individualized risk assessment. Herein, we evaluate the prognostic value of 6 biomarkers: high-sensitivity C-reactive protein, heat shock protein-70, fibrin degradation products, soluble urokinase plasminogen activator receptor, high-sensitivity troponin I, and B-type natriuretic peptide. We then develop a multi-biomarker-based cardiovascular event prediction model for patients with stable CAD. In total, 3,115 subjects with stable CAD who underwent cardiac catheterization at Emory (mean age 62.8 years, 17% Black, 35% female, 57% obstructive CAD, 31% diabetes mellitus) were randomized into a training cohort to identify biomarker cutoff values and a validation cohort for prediction assessment. Main outcomes included (1) all-cause death and (2) a composite of cardiovascular death and nonfatal myocardial infarction (MI) within 5 years. Elevation of each biomarker level was associated with higher event rates in the training cohort. A biomarker risk score was created using optimal cutoffs, ranging from 0 to 6 for each biomarker exceeding its cutoff. In the validation cohort, each unit increase in the biomarker risk score was independently associated with all-cause death (hazard ratio 1.62, 95% confidence interval [CI] 1.45 to 1.80) and cardiovascular death/MI (hazard ratio 1.52, 95% CI 1.35 to 1.71). A biomarker risk prediction model for cardiovascular death/MI improved the c-statistic (∆ 6.4%, 95% CI 3.9 to 8.8) and net reclassification index by 31.1% (95% CI 24 to 37), compared with clinical risk factors alone. Integrating multiple biomarkers with clinical variables refines cardiovascular risk assessment in patients with CAD.

Usefulness of Restless Legs Symptoms to Predict Adverse Cardiovascular Outcomes in Men With Coronary Artery Disease.

The relationship between restless legs syndrome (RLS) and cardiovascular disease remains enigmatic in the general population, and its prognostic value in patients with coronary artery disease (CAD) is unknown. In this study, the frequency of RLS-like symptoms was assessed using a validated instrument in 3,266 patients undergoing cardiac catheterization (mean age 64 years, 62% male, 23% Black, and 74% with obstructive CAD). Patients were followed for primary end points of cardiovascular death or incident myocardial infarction. Fine and Gray hazard models explored the association between RLS and incident events after adjustment for demographic and clinical risk factors. In the total cohort, 29% of patients reported mild (rare or sometimes) symptoms, and 15% of patients had moderate/severe (often to almost always) symptoms of RLS. Female sex (odds ratio [OR] 2.11, 95% confidence interval (CI), 1.68 to 2.57), body mass index (OR 1.12 per 5 kg/m2, 95% CI, 1.04 to 1.22), diabetes (OR 1.43, 95%,1.15 to 1.79), and ß-blocker use (OR 1.35, 95% CI, 1.07 to 1.72) were independently associated with moderate/severe symptoms of RLS compared with no symptoms. Over a 5-year follow-up period, 991 patients suffered an adverse event. Compared with those with no symptoms, patients with moderate/severe RLS had significantly higher risk of the primary end point (hazard ratio [HR] = 1.33, 95%),CI 1.01 to 1.76) after adjustment for demographic and clinical risk factors. The association was more significant in men than women, HR 1.98, 95% CI, 1.41 to 2.78 versus HR 0.99 (,95% CI, 0.64 to 1.52, p interaction= 0.013. In conclusion, among men with CAD, moderate-to-severe symptoms of RLS are associated with significantly higher risk of adverse cardiovascular outcomes, independent of traditional risk factors.

N8-Acetylspermidine: A Polyamine Biomarker in Ischemic Cardiomyopathy With Reduced Ejection Fraction.

Background Patients with ischemic cardiomyopathy (ICM) have worse outcomes than those with coronary artery disease alone and those with non-ICM. N8-acetylspermidine (N8AS) is a polyamine that regulates ischemic cardiac apoptosis and resultant cardiac dysfunction. We hypothesized that N8AS is a mechanistic biomarker of adverse outcomes in patients with ICM. Methods and Results High-resolution plasma metabolomics profiling and mass spectrometry were used to quantitate N8AS levels in a discovery cohort of 474 patients with coronary artery disease (age: 68±11 years, 12% black, 26% women): 154 with ICM, and 320 without ICM; and in an external validation cohort of 85 patients with ICM (age: 60±12 years, 37% black, 19% women). Patients without heart failure (HF) at baseline were followed for incident HF. The association between N8AS (log2-transformed, standardized) and outcomes of all-cause mortality and incident HF were examined using Cox regression. N8AS was higher (10.39 [interquartile range, 7.21-17.75] versus 8.29 nmol/L [interquartile range, 5.91-11.42]; P<0.001) in patients with ICM compared with patients who had coronary artery disease without ICM. Higher N8AS levels were associated with higher mortality in patients with ICM (hazard ratio [HR], 1.48; 95% CI, 1.19-1.85 per SD increase [P=0.001]), independent of B-type natriuretic peptide, high-sensitivity troponin I, and high-sensitivity C-reactive protein. Findings were validated in the independent cohort. Moreover, higher N8AS level was associated with incident HF in patients without HF at baseline (HR, 4.16; 95% CI, 1.41-12.25 per SD increase [P=0.01]). Conclusions Independent of traditional HF measures, higher N8AS levels are associated with higher mortality in patients with ICM and incident HF in those who have coronary artery disease without HF. N8AS is a novel mechanistic biomarker in ICM.

Untargeted high-resolution plasma metabolomic profiling predicts outcomes in patients with coronary artery disease.

OBJECTIVE: Patients with CAD have substantial residual risk of mortality, and whether hitherto unknown small-molecule metabolites and metabolic pathways contribute to this risk is unclear. We sought to determine the predictive value of plasma metabolomic profiling in patients with CAD. APPROACH AND RESULTS: Untargeted high-resolution plasma metabolomic profiling of subjects undergoing coronary angiography was performed using liquid chromatography/mass spectrometry. Metabolic features and pathways associated with mortality were identified in 454 subjects using metabolome-wide association studies and Mummichog, respectively, and validated in 322 subjects. A metabolomic risk score comprising of log-transformed HR estimates of metabolites that associated with mortality and passed LASSO regression was created and its performance validated. In 776 subjects (66.8 years, 64% male, 17% Black), 433 and 357 features associated with mortality (FDR-adjusted q<0.20); and clustered into 21 and 9 metabolic pathways in first and second cohorts, respectively. Six pathways (urea cycle/amino group, tryptophan, aspartate/asparagine, lysine, tyrosine, and carnitine shuttle) were common. A metabolomic risk score comprising of 7 metabolites independently predicted mortality in the second cohort (HR per 1-unit increase 2.14, 95%CI 1.62, 2.83). Adding the score to a model of clinical predictors improved risk discrimination (delta C-statistic 0.039, 95%CI -0.006, 0.086; and Integrated Discrimination Index 0.084, 95%CI 0.030, 0.151) and reclassification (continuous Net Reclassification Index 23.3%, 95%CI 7.9%, 38.2%). CONCLUSIONS: Differential regulation of six metabolic pathways involved in myocardial energetics and systemic inflammation is independently associated with mortality in patients with CAD. A novel risk score consisting of representative metabolites is highly predictive of mortality.

Circulating Progenitor Cells in Patients With Coronary Artery Disease and Renal Insufficiency.

Patients with coronary artery disease and renal insufficiency (RI) (estimated glomerular filtration rate <60 ml/min/1.73 m2) are at an increased risk of cardiovascular events. The contribution of regenerative capacity, measured as circulating progenitor cell (CPC) counts, to this increased risk is unclear. CPCs were enumerated as cluster of differentiation (CD) 45med+ mononuclear cells expressing CD34+, CD133+, CXCR4+ (chemokine [C-X-C motif] receptor 4), and VEGF2R+ (vascular endothelial growth factor receptor 2) epitopes in 1,281 subjects with coronary artery disease (35% with RI). Patients with RI and low (median) were at a similar risk as those without RI.

Low Educational Attainment is a Predictor of Adverse Outcomes in Patients With Coronary Artery Disease.

Background Educational attainment is an indicator of socioeconomic status and is inversely associated with coronary artery disease risk. Whether educational attainment level (EAL) among patients with coronary artery disease influences outcomes remains understudied. Methods and Results Patients undergoing cardiac catheterization had their highest EAL assessed using options of elementary/middle school, high school, college, or graduate education. Primary outcome was all-cause mortality and secondary outcomes were a composite of cardiovascular death/non-fatal myocardial infarction and non-fatal myocardial infarction during follow-up. Cox models adjusted for clinically relevant confounders were used to analyze the association of EAL with outcomes. Among 6318 patients (63.5 years, 63% men, 23% black) enrolled, 16%, 42%, 38%, and 4% had received graduate or higher, college, high school, and elementary/middle school education, respectively. During 4.2 median years of follow-up, there were 1066 all-cause deaths, 812 cardiovascular deaths/non-fatal myocardial infarction, and 276 non-fatal myocardial infarction. Compared with patients with graduate education, those in lower EAL categories (elementary/middle school, high school, or college education) had a higher risk of all-cause mortality (hazard ratios 1.52 [95% CI 1.11-2.09]; 1.43 [95% CI 1.17-1.73]; and 95% CI 1.26 [1.03-1.53], respectively). Similar findings were observed for secondary outcomes. Conclusions Low educational attainment is an independent predictor of adverse outcomes in patients undergoing angiographic coronary artery disease evaluation. The utility of incorporating EAL into risk assessment algorithms and the causal link between low EAL and adverse outcomes in this high-risk patient population need further investigation.

Contemporary cardiovascular device clinical trials (trends and patterns 2001 to 2012).

Device uptake and development have progressed over the last decade, but few quantitative data exist examining the overall operating characteristics and temporal trends of these clinical trials. We performed a systematic analysis of all cardiovascular device clinical trials from 2001 to 2012 published in medical and cardiovascular journals with the 8 highest impact factors. Of the 1,224 identified cardiovascular clinical trials, 299 (24.4%) focused specifically on devices. Each trial included a median of 335 patients (162 to 745) recruited from a median of 14 sites (3 to 38) over a median enrollment duration of 1.9 years (1.2 to 3.3). Median enrollment rate was 1.1 patients/site/month (0.5 to 4.2). Most device trials targeted coronary artery disease (55.2%), followed by arrhythmias (17.4%). Most were industry sponsored (53.6%) and included mortality as a primary end point (69.6%). The median number of patients (225 to 499, p <0.001 for trend) and enrolling sites (11 to 19, p = 0.07 for trend) increased from 2001 to 2012. During the study period, multinational enrollment grew and approached 50% (p = 0.03), whereas trials enrolling in North America exclusively decreased from 30% to 17% (p = 0.10 for trend). Approximately 70% of device trials met their primary end points; this rate did not significantly change over time. In conclusion, this descriptive study of the contemporary cardiovascular device clinical trials highlights recent trends toward larger, more international trial programs. These aggregate data may help inform future cardiovascular device development.