Fluid phase biopsy for detection and characterization of circulating endothelial cells in myocardial infarction.

Elevated levels of circulating endothelial cells (CECs) occur in response to various pathological conditions including myocardial infarction (MI). Here, we adapted a fluid phase biopsy technology platform that successfully detects circulating tumor cells in the blood of cancer patients (HD-CTC assay), to create a high-definition circulating endothelial cell (HD-CEC) assay for the detection and characterization of CECs. Peripheral blood samples were collected from 79 MI patients, 25 healthy controls and six patients undergoing vascular surgery (VS). CECs were defined by positive staining for DAPI, CD146 and von Willebrand Factor and negative staining for CD45. In addition, CECs exhibited distinct morphological features that enable differentiation from surrounding white blood cells. CECs were found both as individual cells and as aggregates. CEC numbers were higher in MI patients compared with healthy controls. VS patients had lower CEC counts when compared with MI patients but were not different from healthy controls. Both HD-CEC and CellSearch® assays could discriminate MI patients from healthy controls with comparable accuracy but the HD-CEC assay exhibited higher specificity while maintaining high sensitivity. Our HD-CEC assay may be used as a robust diagnostic biomarker in MI patients.

Author response to comment on "characterization of circulating endothelial cells in acute myocardial infarction".

A substantial number of patients with the appropriate clinical phenotypes must be studied to disprove previous findings that circulating endothelial cell counts and morphology can predict atherosclerotic plaque rupture.

Characterization of circulating endothelial cells in acute myocardial infarction.

Acute myocardial infarction (MI), which involves the rupture of existing atheromatous plaque, remains highly unpredictable despite recent advances in the diagnosis and treatment of coronary artery disease. Accordingly, a clinical measurement that can predict an impending MI is desperately needed. Here, we characterize circulating endothelial cells (CECs) using an automated and clinically feasible CEC three-channel fluorescence microscopy assay in 50 consecutive patients with ST-segment elevation MI and 44 consecutive healthy controls. CEC counts were significantly elevated in MI cases versus controls, with median numbers of 19 and 4 cells/ml, respectively (P = 1.1 × 10(-10)). A receiver-operating characteristic (ROC) curve analysis demonstrated an area under the ROC curve of 0.95, suggesting near-dichotomization of MI cases versus controls. We observed no correlation between CECs and typical markers of myocardial necrosis (ρ = 0.02, creatine kinase-myocardial band; ρ = -0.03, troponin). Morphological analysis of the microscopy images of CECs revealed a 2.5-fold increase (P < 0.0001) in cellular area and a twofold increase (P < 0.0001) in nuclear area of MI CECs versus healthy controls, age-matched CECs, as well as CECs obtained from patients with preexisting peripheral vascular disease. The distribution of CEC images that contained from 2 to 10 nuclei demonstrates that MI patients were the only subject group to contain more than 3 nuclei per image, indicating that multicellular and multinuclear clusters are specific for acute MI. These data indicate that CEC counts may serve as a promising clinical measure for the prediction of atherosclerotic plaque rupture events.

Genome-wide association of implantable cardioverter-defibrillator activation with life-threatening arrhythmias.

OBJECTIVES: To identify genetic factors that would be predictive of individuals who require an implantable cardioverter-defibrillator (ICD), we conducted a genome-wide association study among individuals with an ICD who experienced a life-threatening arrhythmia (LTA; cases) vs. those who did not over at least a 3-year period (controls). BACKGROUND: Most individuals that receive implantable cardioverter-defibrillators never experience a life-threatening arrhythmia. Genetic factors may help identify who is most at risk. METHODS: Patients with an ICD and extended follow-up were recruited from 34 clinical sites with the goal of oversampling those who had experienced LTA, with a cumulative 607 cases and 297 controls included in the analysis. A total of 1,006 Caucasian patients were enrolled during a time period of 13 months. Arrhythmia status of 904 patients could be confirmed and their genomic data were included in the analysis. In this cohort, there were 704 males, 200 females, and the average age was 73.3 years. We genotyped DNA samples using the Illumina Human660 W Genotyping BeadChip and tested for association between genotype at common variants and the phenotype of having an LTA. RESULTS AND CONCLUSIONS: We did not find any associations reaching genome-wide significance, with the strongest association at chromosome 13, rs11856574 at P = 5×10⁻6. Loci previously implicated in phenotypes such as QT interval (measure of the time between the start of the Q wave and the end of the T wave as measured by electrocardiogram) were not found to be significantly associated with having an LTA. Although powered to detect such associations, we did not find common genetic variants of large effect associated with having a LTA in those of European descent. This indicates that common gene variants cannot be used at this time to guide ICD risk-stratification. TRIAL REGISTRATION: ClinicalTrials.gov NCT00664807.

Emerging genomic applications in coronary artery disease.

Over the last 4 years, an unprecedented number of studies illuminating the genomic underpinnings of common "polygenic" diseases including coronary artery disease have been published. Notably, these studies have established numerous deoxyribonucleic acid (DNA) variants within or near chromosome 9p21.3, the LPA, CXADR, and APOE genes, to name a few, as key coronary artery disease and sudden cardiac death susceptibility markers. Most importantly, many of these DNA variants confer over a 2-fold increase in risk for coronary artery disease, myocardial infarction, and ventricular fibrillation. Additionally, loss-of-function variants in the hepatic cytochrome 2C19 system have now been found to be the predominant genetic mediators of clopidogrel antiplatelet response, with variant carriers having a >3-fold increase in risk for stent thrombosis. In the near future, many additional rare polymorphisms, structural variants, and tissue-specific epigenetic features of the human genome including DNA methylation, histone modifications, and chromatin state will emerge as significant contributors to disease pathogenesis and drug response. In aggregate, these findings will have the potential to radically change the practice of cardiovascular medicine. However, only the individual clinician can ultimately enable the translation of these important discoveries to systematic implementation in clinical practice.

Emerging clinical applications in cardiovascular pharmacogenomics.

Over one-fourth of the 36 million annual outpatient prescriptions filled in the United States are known to have human genomic biomarker information available that predicts drug safety and efficacy, or both. However, to date, we have not systematically implemented strategies to effectively use this data in clinical practice to improve patient outcomes. Part of the difficulty has stemmed from the only modest predictive capacity of previously identified gene variants, lack of replication of data in multiple studies, and the hesitancy of the clinical community to translate data gleaned from basic and translational research to routine clinical practice. Now, additional key variants that strongly impact drug absorption, metabolism, and excretion are rapidly surfacing through the use of genome-wide association technology. Most importantly, these variants are being validated in independent cohorts of thousands of cases and controls. In the near future, the dramatic reduction in the cost of DNA sequencing will lead to further insight into the common and rare genetic variants that strongly predict our individual response to commonly used medications. The clinical community will need to be prepared to utilize this vital data in aiding their selection of the right drug for the right patient if we expect to significantly reduce the ever increasing burden of societies' most common diseases. Herein, we detail the most clinically compelling and robust examples of pharmacogenomics emerging in the field of cardiovascular disease and hopefully foretell how cardiovascular disease might be treated in the era of genomic medicine.

The case for routine genotyping in dual-antiplatelet therapy.

Over 1 million coronary stent procedures are performed annually in the U.S., with dual-antiplatelet therapy, which includes the use of both aspirin and clopidogrel, being a cornerstone in the management of these patients after coronary intervention. Now, recent data have surfaced demonstrating altered active metabolite levels of clopidogrel in patients harboring hepatic cytochrome gene variants. These variants, which have been validated through genome-wide association as the dominant explanation for the marked heterogeneity of clopidogrel response, are linked to a significant increase in the risk for bleeding, stent thrombosis, myocardial infarction, and death. With viable alternatives to clopidogrel now available, including higher clopidogrel maintenance and loading doses, prasugrel, and ticagrelor, clinicians can now effectively guide therapy in those with at-risk gene variants by simple genotyping. Such an individualized approach can potentially prevent tens of thousands of adverse cardiovascular events in the over 30% of those with European ancestry and over 40% of those with Asian or African ancestry who harbor these important clopidogrel gain-of-function and loss-of-function alleles.

Molecular genetics of atrial fibrillation.

Atrial fibrillation (AF) is the most common persistent cardiac dysrhythmia and the number one cause of arrhythmia-related hospitalizations. In addition, AF is a major contributor to stroke. With life expectancies increasing, the growing global disability from AF has crippling implications for society. Several family studies have shown a strong polygenetic predisposition for AF but, so far, most of the linkage analysis and candidate gene studies have discovered only monogenic, rare, deleterious mutations. Recent breakthroughs in high-throughput genotyping technology have allowed improved scanning of the genome with greater statistical power to detect susceptibility alleles for AF. Using this technology, a region on 4q25 has now been identified and validated in thousands of cases as a common susceptibility factor for AF with an odds ratio of over 3.0 for homozygotes. The Paired-like homeodomain transcription factor 2 (PITX2) gene, which is involved in embryonic cardiac development, has now been identified as the causal variant for the 4q25 susceptibility locus. Additional susceptibility variants are anticipated that will have direct ramifications for prognosis and treatment of this highly pervasive and clinically significant disorder.

Future use of genomics in coronary artery disease.

Coronary artery disease (CAD) remains the number one cause of death in industrialized countries despite our collective efforts to minimize attributable risk from known contributors to CAD such as hypertension, dyslipidemia, and smoking. In addition, clinical trials have consistently demonstrated a family history of coronary disease to be predictive for future cardiovascular events beyond that which would be explained by traditional risk factors. These findings support and have prompted widespread investigation into the genomic basis of CAD and myocardial infarction (MI). Recent advances in genotyping technology have allowed for easier identification and confirmation of susceptibility genes for complex traits across different cohorts via increased power of studies stemming from faster accrual of cases and control subjects and more precise genetic mapping. These technological advances have resulted in defining the genes contributing to a substantial or even majority of population-attributable risk for type 2 diabetes and age-related macular degeneration (AMD) cases. Similar progress in replicating novel susceptibility genes for CAD and specifically MI is now rapidly occurring, with a recent gene marker on chromosome 9p21 representing a highly significant and common variant susceptibility factor. With improved resequencing technology and better phenotypic characterization of our CAD cases and control subjects, we should achieve successes in gene identification and confirmation similar to diabetes and AMD, thereby allowing us to better quantify CAD risk earlier in life and institute more effective therapy reducing the individual propensity to develop CAD.

Early- and medium-term outcomes after paclitaxel-eluting stent implantation for sirolimus-eluting stent failure.

The optimal treatment for sirolimus-eluting stent (SES) restenosis is not known. This study evaluated the safety and clinical outcome of paclitaxel-eluting stent (PES) implantation for SES restenosis. From March 2004 to July 2005, PESs were implanted in 125 patients with 140 lesions with SES restenosis. Acute and 6-month clinical outcomes were determined through review of the medical record and/or telephone interview. In-hospital major adverse cardiac events (death, nonfatal myocardial infarction, or repeat revascularization) occurred in 14 patients (11.2%), driven entirely by postprocedure non-Q-wave myocardial infarction. At a mean clinical follow-up of 7.2 +/- 1.8 months, the incidence of target lesion revascularization (TLR) was 14.0%, and the rate of major adverse cardiac events was 17.2%. Subacute thrombosis occurred in 2 patients (1.6%). Length of PES implanted, postprocedure diameter stenosis, and total occlusion of the target lesion were independent predictors of TLR. In patients with de novo SES restenosis, TLR was only 8.7%. In conclusion, at medium-term follow-up, PES implantation for SES failure appears to be safe and effective, although efficacy is decreased in the setting of total occlusions, greater residual diameter stenosis, and longer PESs.