Angela M. Taylor

Efficacy and safety of ventricular tachycardia ablation with mechanical circulatory support compared with substrate-based ablation techniques

AIMS Catheter ablation of ventricular tachycardia (VT) can be limited by haemodynamic instability. In these cases, substrate-based ablation is typically performed. An alternative is to perform activation and entrainment mapping during VT supported by a percutaneous left ventricular assist device (pVAD). We sought to compare the complication and success rates of pVAD-assisted VT ablation with scar-based techniques. METHODS AND RESULTS Thirteen consecutive patients with haemodynamically unstable VT underwent pVAD-assisted ablation (pVAD group) and were retrospectively compared with 18-matched patients undergoing a substrate-based VT ablation (non-pVAD group). There was no significant difference in age or ejection fraction between the groups although pVAD patients tended to have more shocks in the preceding months. Procedure times were longer for the pVAD group. The number of monomorphic VTs induced was greater in the pVAD group (3.2 vs. 1.6, P= 0.04); however, after ablation, there was no difference in inducibility between the pVAD and non-pVAD group (10 of 13 vs. 12 of 18; 77 vs. 67%, P = 0.69). There was no difference in acute complications including stroke or death. At 9 ± 3 months, 1-year freedom from implantable cardioverter-defibrillator (ICD) shocks/therapies for sustained VT were similar (P= 0.96). In multivariable analysis, the absence of atrial fibrillation (hazard ratio=0.15, P= 0.04) was associated with a lower incidence of ICD shocks. CONCLUSIONS In high-risk patients, pVAD-assisted VT ablation guided by activation and entrainment mapping is a feasible alternative to substrate mapping and allows outcomes comparable to substrate mapping.

B-1b Cells Secrete Atheroprotective IgM and Attenuate Atherosclerosis

RATIONALE B cells contribute to atherosclerosis through subset-specific mechanisms. Whereas some controversy exists about the role of B-2 cells, B-1a cells are atheroprotective because of secretion of atheroprotective IgM antibodies independent of antigen. B-1b cells, a unique subset of B-1 cells that respond specifically to T-cell-independent antigens, have not been studied within the context of atherosclerosis. OBJECTIVE To determine whether B-1b cells produce atheroprotective IgM antibodies and function to protect against diet-induced atherosclerosis. METHODS AND RESULTS We demonstrate that B-1b cells are sufficient to produce IgM antibodies against oxidation-specific epitopes on low-density lipoprotein both in vitro and in vivo. In addition, we demonstrate that B-1b cells provide atheroprotection after adoptive transfer into B- and T-cell deficient (Rag1(-/-)Apoe(-/-)) hosts. We implicate inhibitor of differentiation 3 (Id3) in the regulation of B-1b cells as B-cell-specific Id3 knockout mice (Id3(BKO)Apoe(-/-)) have increased numbers of B-1b cells systemically, increased titers of oxidation-specific epitope-reactive IgM antibodies, and significantly reduced diet-induced atherosclerosis when compared with Id3(WT)Apoe(-/-) controls. Finally, we report that the presence of a homozygous single nucleotide polymorphism in ID3 in humans that attenuates Id3 function is associated with an increased percentage of circulating B-1 cells and anti-malondialdehyde-low-density lipoprotein IgM suggesting clinical relevance. CONCLUSIONS These results provide novel evidence that B-1b cells produce atheroprotective oxidation-specific epitope-reactive IgM antibodies and protect against atherosclerosis in mice and suggest that similar mechanisms may occur in humans.

Concurrence of angiographic coronary artery disease in patients with apical ballooning syndrome (tako-tsubo cardiomyopathy)†

Objective: To determine the coexistence of coronary artery disease (CAD) in an unselected cohort of patients with apical ballooning syndrome (ABS). Background: ABS is a clinical condition of unknown etiology with symptoms that mimic an acute coronary syndrome and is characterized by the presence of transient left ventricular dysfunction primarily affecting the apex of the heart. Methods: We conducted a retrospective case series in a single tertiary care hospital. Patients were identified by searching for several inclusive discharge diagnoses in all hospitalized patients. Suspected cases were analyzed using prespecified diagnostic criteria. Demographic, clinical, and imaging data were collected. Coronary lesions were assessed by quantitative angiography. Results: Thirty‐one cases of ABS were identified. The majority of the cases were female, and ischemia was documented in all patients by electrocardiographic or cardiac biomarker criteria. Nineteen patients (61.3%) had angiographic evidence of CAD, with multivessel involvement in seven (23%). Nine patients (29%) had luminal stenosis severity greater than 50% in at least one epicardial vessel. Conclusions: In an unselected cohort of patients with ABS, coronary atherosclerosis is commonly present. Whether CAD simply coexists or is related to the pathophysiology of ABS is unclear.

Phosphorylation Regulates Id3 Function in Vascular Smooth Muscle Cells

Understanding the mechanisms that regulate cell cycle progression in vascular smooth muscle cells (VSMCs) is key to understanding and modulating vascular lesion formation. Results of the present study provide the first evidence that phosphorylation of the helix-loop-helix factor Id3 in VSMCs occurs in vitro and in vivo and provides a regulatory switch controlling Id3-induced regulation of p21Cip1 and VSMC growth.

Polyoxygenated Cholesterol Ester Hydroperoxide Activates TLR4 and SYK Dependent Signaling in Macrophages

Oxidation of low-density lipoprotein (LDL) is one of the major causative mechanisms in the development of atherosclerosis. In previous studies, we showed that minimally oxidized LDL (mmLDL) induced inflammatory responses in macrophages, macropinocytosis and intracellular lipid accumulation and that oxidized cholesterol esters (OxCEs) were biologically active components of mmLDL. Here we identified a specific OxCE molecule responsible for the biological activity of mmLDL and characterized signaling pathways in macrophages in response to this OxCE. Using liquid chromatography – tandem mass spectrometry and biological assays, we identified an oxidized cholesteryl arachidonate with bicyclic endoperoxide and hydroperoxide groups (BEP-CE) as a specific OxCE that activates macrophages in a TLR4/MD-2-dependent manner. BEP-CE induced TLR4/MD-2 binding and TLR4 dimerization, phosphorylation of SYK, ERK1/2, JNK and c-Jun, cell spreading and uptake of dextran and native LDL by macrophages. The enhanced macropinocytosis resulted in intracellular lipid accumulation and macrophage foam cell formation. Bone marrow-derived macrophages isolated from TLR4 and SYK knockout mice did not respond to BEP-CE. The presence of BEP-CE was demonstrated in human plasma and in the human plaque material captured in distal protection devices during percutaneous intervention. Our results suggest that BEP-CE is an endogenous ligand that activates the TLR4/SYK signaling pathway. Because BEP-CE is present in human plasma and human atherosclerotic lesions, BEP-CE-induced and TLR4/SYK-mediated macrophage responses may contribute to chronic inflammation in human atherosclerosis.

Human Blood Monocyte Subsets

Objective— Human monocyte subsets are defined as classical (CD14++CD16−), intermediate (CD14++CD16+), and nonclassical (CD14+CD16+). Alterations in monocyte subset frequencies are associated with clinical outcomes, including cardiovascular disease, in which circulating intermediate monocytes independently predict cardiovascular events. However, delineating mechanisms of monocyte function is hampered by inconsistent results among studies. Approach and Results— We use cytometry by time-of-flight mass cytometry to profile human monocytes using a panel of 36 cell surface markers. Using the dimensionality reduction approach visual interactive stochastic neighbor embedding (viSNE), we define monocytes by incorporating all cell surface markers simultaneously. Using viSNE, we find that although classical monocytes are defined with high purity using CD14 and CD16, intermediate and nonclassical monocytes defined using CD14 and CD16 alone are frequently contaminated, with average intermediate and nonclassical monocyte purity of ≈86.0% and 87.2%, respectively. To improve the monocyte purity, we devised a new gating scheme that takes advantage of the shared coexpression of cell surface markers on each subset. In addition to CD14 and CD16, CCR2, CD36, HLA-DR, and CD11c are the most informative markers that discriminate among the 3 monocyte populations. Using these additional markers as filters, our revised gating scheme increases the purity of both intermediate and nonclassical monocyte subsets to 98.8% and 99.1%, respectively. We demonstrate the use of this new gating scheme using conventional flow cytometry of peripheral blood mononuclear cells from subjects with cardiovascular disease. Conclusions— Using cytometry by time-of-flight mass cytometry, we have identified a small panel of surface markers that can significantly improve monocyte subset identification and purity in flow cytometry. Such a revised gating scheme will be useful for clinical studies of monocyte function in human cardiovascular disease.

Measurement of microparticle tissue factor activity in clinical samples: A summary of two tissue factor-dependent FXa generation assays

Thrombosis is a leading cause of morbidity and mortality. Detection of a prothrombotic state using biomarkers would be of great benefit to identify patients at risk of thrombosis that would benefit from thromboprophylaxis. Tissue factor (TF) is a highly procoagulant protein that under normal conditions is not present in the blood. However, increased levels of TF in the blood in the form of microparticles (MPs) (also called extracellular vesicles) are observed under various pathological conditions. In this review, we will discuss studies that have measured MP-TF activity in a variety of diseases using two similar FXa generation assay. One of the most robust signals for MP-TF activity (16-26 fold higher than healthy controls) is observed in pancreatic cancer patients with venous thromboembolism. In this case, the TF+ MPs appear to be derived from the cancer cells. Surprisingly, cirrhosis and acute liver injury are associated with 17-fold and 38-fold increases in MP-TF activity, respectively. Based on mouse models, we speculate that the TF+ MPs are derived from hepatocytes. More modest increases are observed in patients with urinary tract infections (6-fold) and in a human endotoxemia model (9-fold) where monocytes are the likely source of the TF+ MPs. Finally, there is no increase in MP-TF activity in the majority of cardiovascular disease patients. These studies indicate that MP-TF activity may be a useful biomarker to identify patients with particular diseases that have an increased risk of thrombosis.

Hyperlipemia and oxidation of LDL induce vascular smooth muscle cell growth: an effect mediated by the HLH factor Id3.

Hyperlipemia and oxidized LDL (ox-LDL) are important independent cardiovascular risk factors. Ox-LDL has been shown to stimulate vascular smooth muscle cell (VSMC) proliferation. However, the effects of hyperlipemia and the molecular mechanisms mediating hyperlipemia and ox-LDL effects on VSMC growth are poorly understood. The helix-loop-helix (HLH) transcription factor, Id3, is a redox-sensitive gene expressed in VSMC in response to mitogen stimulation and vascular injury. Accordingly, we hypothesize that Id3 is an important mediator of ox-LDL and hyperlipemia-induced VSMC growth. Aortas harvested from hyperlipemic pigs demonstrated significantly more Id3 than normolipemic controls. Primary VSMC were stimulated with ox-LDL, native LDL, sera from hyperlipemic pigs, or normolipemic pigs. VSMC exposed to hyperlipemic sera demonstrated increased Id3 expression, VSMC growth and S-phase entry and decreased p21cip1 expression and transcription. Cells stimulated with ox-LDL demonstrated similar findings of increased growth and Id3 expression and decreased p21cip1 expression. Moreover, the effects of ox-LDL on growth were abolished in cells devoid of the Id3 gene. Results provide evidence that the HLH factor Id3 mediates the mitogenic effect of hyperlipemic sera and ox-LDL in VSMC via inhibition of p21cip1 expression, subsequently increasing DNA synthesis and proliferation.

Plasma Chemokine Levels Are Associated with the Presence and Extent of Angiographic Coronary Collaterals in Chronic Ischemic Heart Disease

Background In patients with chronic ischemic heart disease (IHD), the presence and extent of spontaneously visible coronary collaterals are powerful determinants of clinical outcome. There is marked heterogeneity in the recruitment of coronary collaterals amongst patients with similar degrees of coronary artery stenoses, but the biological basis of this heterogeneity is not known. Chemokines are potent mediators of vascular remodeling in diverse biological settings. Their role in coronary collateralization has not been investigated. We sought to determine whether plasma levels of angiogenic and angiostatic chemokines are associated with of the presence and extent of coronary collaterals in patients with chronic IHD. Methodology/Principal Findings We measured plasma concentrations of angiogenic and angiostatic chemokine ligands in 156 consecutive subjects undergoing coronary angiography with at least one ≥90% coronary stenosis and determined the presence and extent of spontaneously visible coronary collaterals using the Rentrop scoring system. Eighty-eight subjects (56%) had evidence of coronary collaterals. In a multivariable regression model, the concentration of the angiogenic ligands CXCL5, CXCL8 and CXCL12, hyperlipidemia, and an occluded artery were associated with the presence of collaterals; conversely, the concentration of the angiostatic ligand CXCL11, interferon-γ, hypertension and diabetes were associated with the absence of collaterals (ROC area 0.91). When analyzed according to extent of collateralization, higher Rentrop scores were significantly associated with increased concentration of the angiogenic ligand CXCL1 (p<0.0001), and decreased concentrations of angiostatic ligands CXCL9 (p<0.0001), CXCL10 (p = 0.002), and CXCL11 (p = 0.0002), and interferon-γ (p = 0.0004). Conclusions/Significance Plasma chemokine concentrations are associated with the presence and extent of spontaneously visible coronary artery collaterals and may be mechanistically involved in their recruitment.

Extent and Severity of Coronary Disease and Mortality in Patients with End-Stage Renal Failure Evaluated for Renal Transplantation

The purpose of this study is to explore the relationship between coronary artery disease (CAD), transplantation status and subsequent mortality in end‐stage renal disease (ESRD) patients undergoing evaluation for renal transplantation. Two hundred fifty‐three ESRD patients at high risk for CAD underwent coronary angiography as part of a renal transplant evaluation. The cohort was divided into three groups: Group 1 (n = 127) had no vessels with ≥50% stenosis, Group 2 (n = 56) had one vessel with ≥50% stenosis and Group 3 (n = 70) had two or more vessels with ≥50% stenosis. Long‐term survival was determined; median follow‐up was 3.3 years. The baseline characteristics were similar except for older age and higher proportion of diabetes mellitus, dyslipidemia and peripheral vascular disease in Groups 2 and 3 patients as compared to Group 1. Survival was worse in Group 3 compared to Group 1 (p < 0.0001). Each of the three subgroups had better survival with renal transplantation than those who did not undergo transplantation (p < 0.0001). Although the degree of CAD is related to subsequent mortality, transplantation is associated with better survival regardless of the extent and severity of CAD. Thus, the presence of CAD should not exclude ESRD patients from consideration for this therapy.