Computed tomographic angiography measures of coronary plaque in clinical trials: opportunities and considerations to accelerate drug translation.

Atherosclerotic coronary artery disease (CAD) is the causal pathological process driving most major adverse cardiovascular events (MACE) worldwide. The complex development of atherosclerosis manifests as intimal plaque which occurs in the presence or absence of traditional risk factors. There are numerous effective medications for modifying CAD but new pharmacologic therapies require increasingly large and expensive cardiovascular outcome trials to assess their potential impact on MACE and to obtain regulatory approval. For many disease areas, nearly a half of drugs are approved by the U.S. Food & Drug Administration based on beneficial effects on surrogate endpoints. For cardiovascular disease, only low-density lipoprotein cholesterol and blood pressure are approved as surrogates for cardiovascular disease. Valid surrogates of CAD are urgently needed to facilitate robust evaluation of novel, beneficial treatments and inspire investment. Fortunately, advances in non-invasive imaging offer new opportunity for accelerating CAD drug development. Coronary computed tomography angiography (CCTA) is the most advanced candidate, with the ability to measure accurately and reproducibly characterize the underlying causal disease itself. Indeed, favourable changes in plaque burden have been shown to be associated with improved outcomes, and CCTA may have a unique role as an effective surrogate endpoint for therapies that are designed to improve CAD outcomes. CCTA also has the potential to de-risk clinical endpoint-based trials both financially and by enrichment of participants at higher likelihood of MACE. Furthermore, total non-calcified, and high-risk plaque volume, and their change over time, provide a causally linked measure of coronary artery disease which is inextricably linked to MACE, and represents a robust surrogate imaging biomarker with potential to be endorsed by regulatory authorities. Global consensus on specific imaging endpoints and protocols for optimal clinical trial design is essential as we work towards a rigorous, sustainable and staged pathway for new CAD therapies.

Primary prevention of cardiovascular disease in women.

Ischemic heart disease is the primary cause of cardiovascular disease (CVD) mortality in both men and women. Strategies targeting traditional modifiable risk factors are essential - including hypertension, smoking, dyslipidemia and diabetes mellitus - particularly for atherosclerosis, but additionally for stroke, heart failure and some arrhythmias. However, challenges related to education, screening and equitable access to effective preventative therapies persist, and are particularly problematic for women around the globe and those from lower socioeconomic groups. The association of female-specific risk factors (e.g. premature menopause, gestational hypertension, small for gestational age births) with CVD provides a potential window for targeted prevention strategies. However, further evidence for specific effective screening and interventions is urgently required. In addition to population-level factors involved in increasing the risk of suffering a CVD event, efforts are leveraging the enormous potential of blood-based 'omics', improved imaging biomarkers and increasingly complex bioinformatic analytic approaches to strive toward more personalized early disease detection and personalized preventative therapies. These novel tactics may be particularly relevant for women in whom traditional risk factors perform poorly. Here we discuss established and emerging approaches for improving risk assessment, early disease detection and effective preventative strategies to reduce the mammoth burden of CVD in women.

Prevalence, distribution and clinical correlates of myocardial fibrosis in systemic lupus erythematosus: a cardiac magnetic resonance study.

OBJECTIVES: To assess the prevalence, distribution and clinical correlates of myocardial fibrosis, as detected by cardiac magnetic resonance (CMR), in systemic lupus erythematosus (SLE). METHODS: Forty-one subjects (average age 39 ± 12 years and 80% female) with SLE underwent CMR imaging at 1.5T, using late gadolinium enhancement (LGE) to quantify the area of myocardial fibrosis in the left ventricle (LV). Subjects also underwent transthoracic echocardiography (TTE) and exercise testing. RESULTS: LGE was detected in 15/41 subjects, 11 with localized LGE (<15% LV mass) and four with extensive LGE (>15% LV mass). The commonest site of LGE was the interventricular septum, with all but one case demonstrating an intramural or inflammatory pattern. The mean age of the >15% LGE group (55 ± 15 years) was significantly higher than the <15% or absent LGE subgroups. Based on both CMR and TTE measurements, subjects with LGE > 15% demonstrated a reduced E/A ratio of 0.9 ± 0.4 relative to the <15% and absent LGE subgroups. LV end-systolic volume (ESVi), end-diastolic volume (EDVi) and maximum exercise capacity were also reduced in the >15% LGE group. CONCLUSIONS: Mid-wall myocardial fibrosis occurs frequently in SLE and is strongly associated with advancing subject age, but not with SLE duration or severity. Extensive LGE may be associated with diastolic dysfunction and impaired exercise capacity, although this may be an epiphenomenon of age. Cardiac magnetic resonance with quantitative assessment of LGE may provide a basis for cardiac risk stratification in SLE.

Prosthetic heart valves in pregnancy, outcomes for women and their babies: a systematic review and meta-analysis.

BACKGROUND: Historically, pregnancies among women with prosthetic heart valves have been associated with an increased incidence of adverse outcomes. OBJECTIVES: Systematic review to assess risk of adverse pregnancy outcomes among women with a prosthetic heart valve(s) over the last 20 years. SEARCH STRATEGY: Electronic literature search of Medline, The Cochrane Library, Cumulative Index to Nursing and Allied Health Literature and Embase to find recent studies. SELECTION CRITERIA: Studies of pregnant women with heart valve prostheses including trials, cohort studies and unselected case series. DATA COLLECTION AND ANALYSIS: Primary analysis calculated absolute risks and 95% confidence intervals (CI) for pregnancy outcomes using a random effects model. The Freeman-Tukey transformation was utilised in secondary analysis due to the large number of individual study outcomes with zero events. MAIN RESULTS: Eleven studies capturing 499 pregnancies among women with heart valve prostheses, including 256 mechanical and 59 bioprosthetic, were eligible for inclusion. Pooled estimate of maternal mortality was 1.2/100 pregnancies (95% CI 0.5-2.2), for mechanical valves subgroup 1.8/100 (95% CI 0.5-3.7) and bioprosthetic subgroup 0.7/100 (95% CI 0.1-4.5), overall pregnancy loss 20.8/100 pregnancies (95% CI 9.5-35.1), perinatal mortality 5.0/100 births (95%CI 1.8-9.8) and thromboembolism 9.3/100 pregnancies (95% CI 4.0-16.5). CONCLUSIONS: Women with heart valve prostheses experienced higher rates of adverse outcomes than expected in a general obstetric population; however, lower than previously reported. Women with bioprostheses had significantly fewer thromboembolic events compared to women with mechanical valves. Women should be counselled pre-pregnancy about risk of maternal death and pregnancy loss. Vigilant surveillance by a multidisciplinary team throughout the perinatal period remains warranted for these women and their infants. TWEETABLE ABSTRACT: Metaanalysis suggests improvement in #pregnancy outcomes among women with #heartvalveprostheses.

Comparison of two dimensional quantitative coronary angiography (2D-QCA) with optical coherence tomography (OCT) in the assessment of coronary artery lesion dimensions.

OBJECTIVES: There is limited data on how well 2D-QCA and OCT agree with each other for measurement of coronary artery lumen dimensions. We aimed to assess the agreement between the two modalities. METHODS: Patients undergoing OCT for assessment of coronary artery lesions were reviewed. Minimum luminal diameter (MLD), proximal reference diameter and distal reference diameter were measured for each lesion prior to stenting. RESULTS: OCT was performed in 64 patients and 40 lesions were suitable for analysis. There was a good correlation for proximal and distal reference diameters (r = 0.86, p < 0.0001 and r = 0.92, p < 0.0001 respectively). There was good agreement on Bland-Altman analysis; the proximal and distal reference diameters measured by QCA were on average 0.09 mm (95% CI, - 0.52 to 0.53 mm) and 0.1 mm (95% CI, - 0.59 to 0.6 mm) smaller than OCT respectively. There was a satisfactory correlation (r = 0.63, p = < 0.0001) between QCA and OCT for MLD. However, the MLD by QCA was 0.49 mm (95% CI, - 1.57 to 0.59 mm) smaller than OCT, suggesting a poor agreement for MLD. CONCLUSIONS: There is a good correlation and agreement between QCA and OCT for measurement of proximal and distal reference diameters. However, the MLD was underestimated by QCA.

Cost benefit for assessment of intermediate coronary stenosis with fractional flow reserve in public and private sectors in australia.

BACKGROUND: Fractional Flow Reserve (FFR) is a proven technology for guiding percutaneous coronary intervention (PCI), but is not reimbursed despite the fact that it is frequently used to defer PCI. METHODS: Costs incurred with use of FFR were compared in both the public and private sectors with the costs that would have been incurred if the technology was not available using consecutive cases over a two year period in a public teaching hospital and its co-located private hospital. RESULTS: FFR was performed on 143 lesions in 120 patients. FFR was < 0.80 in 37 lesions in 34 patients and 25 underwent PCI while 11 had CABG. It was estimated that without FFR 78 lesions in 70 patients would have had PCI with 17 patients having CABG with 35 additional functional tests. Despite a cost of $A1200 per wire, FFR actually saved money. Mean savings in the public sector were $1200 per patient while in the private sector the savings were $5000 per patient. CONCLUSIONS: FFR use saves money for the Federal Government in the public sector and for the Private Health Funds in the private sector. These financial benefits are seen in addition to the improved outcomes seen with this technology.

Current concepts on antiplatelet therapy: focus on the novel thienopyridine and non-thienopyridine agents.

Thienopyridines are a class of drug targeting the platelet adenosine diphosphate (ADP) 2 receptor. They significantly reduce platelet activity and are therefore clinically beneficial in settings where platelet activation is a key pathophysiological feature, particularly myocardial infarction. Ticlopidine, the first of the class introduced to clinical practice, was soon challenged and almost completely replaced by clopidogrel for its better tolerability. More recently, prasugrel and ticagrelor have been shown to provide a more powerful antiplatelet action compared to clopidogrel but at a cost of higher risk of bleeding complications. Cangrelor, a molecule very similar to ticagrelor, is currently being evaluated against clopidogrel. Considering the key balance of ischemic protection and bleeding risk, this paper discusses the background to the development of prasugrel, ticagrelor, and cangrelor and aims to characterise their risk-benefit profile and possible implementation in daily practice.

Functional estrogen receptor alpha promoter polymorphism is associated with improved endothelial-dependent vasolidation.

Estrogen receptor alpha (ERalpha) mediates beneficial actions on endothelial nitric oxide synthase (eNOS) and cholesterol metabolism. Genetic variations in the promoter of the ERalpha may therefore influence vascular function. We have identified a single nucleotide polymorphism (T>C) in the transcriptional element "ERNE" upstream of ERalpha which abolished the negative effect of this element in luciferase reporter assays and was associated with reduction in LDL cholesterol in a small association study. We have now examined for the association of this putative functional polymorphism with endothelial function. Endothelial-dependent relaxation (EDR) was measured in organ bath preparations of human saphenous vein obtained from 101 individuals (81 males and 20 females) undergoing coronary artery bypass surgery. The presence of the variant C allele was associated with enhanced EDR independently of hypercholesterolaemia, smoking and diabetes, as well as sex (ANOVA for ACh induced relaxation: p=0.033). In males, the presence of the C allele was associated with a 225% augmentation of endothelial-dependent relaxation compared to wild-type (55.5+/-10%; n=3 vs. 24.7+/-1%; n=78; p<0.001). In summary, a polymorphism in the ERalpha negative transcriptional element which results in increased transcription in vitro is associated with substantial augmentation of endothelial-dependent vasorelaxation.

Natriuretic peptides stimulate the cardiac sodium pump via NPR-C-coupled NOS activation.

Natriuretic peptides (NPs) and their receptors (NPRs) are expressed in the heart, but their effects on myocyte function are poorly understood. Because NPRs are coupled to synthesis of cGMP, an activator of the sarcolemmal Na(+)-K(+) pump, we examined whether atrial natriuretic peptide (ANP) regulates the pump. We voltage clamped rabbit ventricular myocytes and identified electrogenic Na(+)-K(+) pump current (arising from the 3:2 Na(+):K(+) exchange and normalized for membrane capacitance) as the shift in membrane current induced by 100 micromol/l ouabain. Ten nanomoles per liter ANP stimulated the Na(+)-K(+) pump when the intracellular compartment was perfused with pipette solutions containing 10 mmol/l Na(+) but had no effect when the pump was at near maximal activation with 80 mmol/l Na(+) in the pipette solution. Stimulation was abolished by inhibition of cGMP-activated protein kinase with KT-5823, nitric oxide (NO)-activated guanylyl cyclase with 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ), or NO synthase with N(G)-nitro-L-arginine methyl ester (L-NAME). Since synthesis of cGMP by NPR-A and NPR-B is not NO dependent or ODQ sensitive, we exposed myocytes to AP-811, a highly selective ligand for the NPR-C "clearance" receptor. It abolished ANP-induced pump stimulation. Conversely, the selective NPR-C agonist ANP(4-23) reproduced stimulation. The stimulation was blocked by l-NAME. To examine NO production in response to ANP(4-23), we loaded myocytes with the NO-sensitive fluorescent dye diacetylated diaminofluorescein-2 and examined them by confocal microscopy. ANP(4-23) induced a significant increase in fluorescence, which was abolished by L-NAME. We conclude that NPs stimulate the Na(+)-K(+) pump via an NPR-C and NO-dependent pathway.

Opposing effects of coupled and uncoupled NOS activity on the Na+-K+ pump in cardiac myocytes.

Pharmacological delivery of nitric oxide (NO) stimulates the cardiac Na(+)-K(+) pump. However, effects of NO synthesized by NO synthase (NOS) often differ from the effects of NO delivered pharmacologically. In addition, NOS can become "uncoupled" and preferentially synthesize O(2)(.-), which often has opposing effects to NO. We tested the hypothesis that NOS-synthesized NO stimulates Na(+)-K(+) pump activity, and uncoupling of NOS inhibits it. To image NO, we loaded isolated rabbit cardiac myocytes with 4,5-diaminofluorescein-2 diacetate (DAF-2 DA) and measured fluorescence with confocal microscopy. L-arginine (L-arg; 500 micromol/l) increased DAF-2 DA fluorescence by 51% compared with control (n = 8; P < 0.05). We used the whole cell patch-clamp technique to measure electrogenic Na(+)-K(+) pump current (I(p)). Mean I(p) of 0.35 +/- 0.03 pA/pF (n = 44) was increased to 0.48 +/- 0.03 pA/pF (n = 7, P < 0.05) by 10 micromol/l L-Arg in pipette solutions. This increase was abolished by NOS inhibition with radicicol or by NO-activated guanylyl cyclase inhibition with 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one. We next examined the effect of uncoupling NOS using paraquat. Paraquat (1 mmol/l) induced a 51% increase in the fluorescence intensity of O(2)(.-)-sensitive dye dihydroethidium compared with control (n = 9; P < 0.05). To examine the functional effects of uncoupling, we measured I(p) with 100 micromol/l paraquat included in patch pipette solutions. This decreased I(p) to 0.28 +/- 0.03 pA/pF (n = 12; P < 0.001). The paraquat-induced pump inhibition was abolished by superoxide dismutase (in pipette solutions). We conclude that NOS-mediated NO synthesis stimulates the Na(+)-K(+) pump, whereas uncoupling of NOS causes O(2)(.-)-mediated pump inhibition.

Novel estrogen receptor alpha promoter polymorphism increases ventricular hypertrophic response to hypertension.

Given the strong genetic contribution to blood pressure and left ventricular hypertrophy (LVH), and the influence of estrogen on these parameters, we hypothesized that polymorphisms in the estrogen receptor alpha (ERalpha) promoter may influence LVH. Three novel polymorphisms were identified upstream of the ERalpha alternatively spliced exon 1E, within sequence which demonstrated significant promoter activity in vitro. Demonstration of ERalpha E isoform expression in human ventricle by RT-PCR supported a possible functional role for the 1E novel polymorphisms in estrogen signaling in the heart. Indeed, G>A (-721 E) was significantly associated with LVH after controlling for systolic blood pressure and sex in a healthy population (n=74), contributing to 23% of interventricular septum (IVS) width variance (p<0.001) and 9.4% of left ventricular mass index (LVMI) variance (p=0.035). In a separate hypertensive cohort, male carriers of the A allele (n=8) had a 17% increase in IVS (95% CI: 6-28%) and a 19% increase in LVMI (3-34%) compared to GG homozygotes (n=84). We conclude that a novel polymorphism in the promoter of a cardiac mRNA splice isoform of ERalpha is associated with LVH.

17beta-estradiol potentiates the cardiac cystic fibrosis transmembrane conductance regulator chloride current in guinea-pig ventricular myocytes.

There is a well-characterized membrane chloride current (ICl,cAMP) in the heart that can be activated by beta-adrenergic agonists and is due to expression of the cardiac isoform of the epithelial cystic fibrosis transmembrane conductance regulator (CFTR). We have investigated whether 17beta-estradiol (E2) modulates ICl,cAMP in single ventricular myocytes. Under whole-cell tight-seal voltage-clamp conditions, ICl,cAMP was evoked by exposing cells to 20 nM isoprenaline. On the addition of 30 microM E2, membrane slope conductance, measured at potentials near 0 mV, increased over that induced by isoprenaline alone by 2.46 +/- 0.16 (p < 0.001). The effects of E2 were concentration-dependent and described by a Hill Plot with an EC50 of 8.2 microM and a Hill coefficient of 1.63. The application of membrane-impermeant E2 conjugated to bovine serum albumin (E2-BSA) potentiated isoprenaline-evoked ICl,cAMP by approximately the same degree as that for the equivalent level of free E2. Cell surface binding was observed with confocal microscopy by using BSA-FITC tagged E2. This binding was inhibited by nonlabeled, nonconjugate E2, the specific E2 antagonist ICl 182,780, and incubation of E2coBSA with a specific anti-E2 antibody (E2885). ICl 182,780 (100 microM) significantly reduced the increase in ICl,cAMP evoked by 10 microM E2 to 1.46 +/- 0.10 (p < 0.02). The preincubation of myocytes with the NOS inhibitor N-omega-nitro-arginine (L-NNA, 1 mM) reduced the potentiation of ICl,cAMP by 30 microM E2, to 1.93 +/- 0.06 (p < 0.02), and for 10 microM E2, to 1.32 +/- 0.05 (p < 0.002). E2 also increased ICl,cAMP evoked by bath application of 0.5 microM Forskolin. These experiments demonstrate that, under our experimental conditions, E2 dramatically increases ICl,cAMP in ventricular myocytes by mechanisms involving a contribution by NOS, but that can be only partially accounted for through binding to classical plasma membrane estrogen receptor sites. This potentiation of ICl,cAMP by E2 may play a significant role in the observed clinical actions of E2 on the incidence of cardiac arrhythmias and hypertrophy.

Tamoxifen acutely relaxes coronary arteries by an endothelium-, nitric oxide-, and estrogen receptor-dependent mechanism.

In epidemiological studies tamoxifen has been associated with a reduction in the incidence of fatal myocardial infarction in women. However, the effects of tamoxifen on coronary artery reactivity are unknown. We hypothesized that tamoxifen would relax precontracted isolated rabbit coronary arteries. Rings of coronary artery from adult male and nonpregnant female New Zealand White rabbits were suspended in organ baths containing Krebs' solution; isometric tension was measured. Tamoxifen (0.1-100 microM) induced significant endothelium-dependent relaxation in precontracted rabbit coronary arteries. This relaxation was inhibited by N(omega)-nitro-L-arginine methyl ester and the estrogen receptor antagonist ICI 182,780. There was no significant effect on calcium concentration-dependent contraction curves. These data suggest that tamoxifen has beneficial effects on coronary reactivity that could, at least in part, account for the reduction in risk of fatal myocardial infarction in women taking tamoxifen.

Plant-derived estrogens relax coronary arteries in vitro by a calcium antagonistic mechanism.

OBJECTIVES: To investigate the potential for plant derived estrogens (phytoestrogens) genistein, phloretin, biochanin A and zearalanone to relax rabbit coronary arteries in vitro and to determine the mechanism(s) of such relaxation. BACKGROUND: Epidemiological data suggests a reduction in the incidence of coronary heart disease in humans who have a high intake of phytoestrogens. METHODS: Isolated rabbit coronary artery rings were suspended in individual organ baths, precontracted with potassium chloride (30 mM), and the relaxing effects and mechanisms of relaxation to genistein, phloretin, biochanin A and zearalanone were determined by measurement of isometric tension. RESULTS: Genistein, phloretin and biochanin A induced significant gender-independent relaxation in rings with and without endothelium. Inhibition of nitric oxide and prostaglandin synthesis with L-NAME and indomethacin had no effect on genistein-induced relaxation. Relaxation was unaffected by the specific estrogen receptor antagonist ICI 182,780, the ATP-sensitive potassium channel inhibitor glibenclamide and the potassium channel inhibitor, barium chloride. Calcium concentration-dependent contraction curves in high potassium depolarization medium were significantly shifted to the right and downward after incubation with genistein and zearalanone. An inhibitory effect of genistein (2 microM) on L-type calcium current in guinea-pig ventricular myocytes confirmed a calcium antagonist relaxing mechanism of action. In healthy volunteers, plasma genistein levels of approximately 2 microM are achieved after ingestion of a commercially available soy protein drink (Supro) containing 37 mg genistein. CONCLUSIONS: This study demonstrates that phytoestrogens induce endothelium-independent relaxation of coronary arteries; the mechanism involves calcium antagonism. These mechanisms may contribute to the potential long-term cardiovascular protective effect of these substances.

Raloxifene acutely relaxes rabbit coronary arteries in vitro by an estrogen receptor-dependent and nitric oxide-dependent mechanism.

BACKGROUND: Selective estrogen receptor modulators (SERMs) have been defined as compounds that display tissue specificity with regard to estrogenic effects. They appear to share the beneficial effects of estrogen on bone and lipids but are not associated with an increased risk of breast or uterine carcinoma. Estrogen relaxes coronary arteries and has long-term protective effects on the vascular system. The effect of SERMs on the coronary vasculature is unknown. We therefore investigated the effects of the SERM raloxifene on isolated rabbit coronary arteries. METHODS AND RESULTS: Rings of coronary artery from adult male and nonpregnant female New Zealand White rabbits were suspended in organ baths containing Krebs solution; isometric tension was then measured. Raloxifene induced coronary arterial relaxation in male and female coronary arteries by an endothelium-dependent and estrogen receptor-dependent mechanism involving nitric oxide. Raloxifene also had a direct calcium antagonistic effect on the coronary myocyte. Estrogen, however, induced only endothelium-independent coronary arterial relaxation. The endothelium-dependent component of relaxation induced by raloxifene 10(-6) mol/L resulted in almost 100% (79+/-7% versus 43+/-3%, P<0.001) more relaxation than that induced by estrogen 10(-6) mol/L. CONCLUSIONS: These data demonstrate that raloxifene has vascular relaxing properties. The surprising finding is that the receptor-dependent effects via the endothelium are observed in coronary arteries from both male and female animals.