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Malte Kelm

Publications and source records attributed to Malte Kelm.

At least 19 recordsLinked to original sources

Distinct Genetic Risk Profile in Aortic Stenosis Compared With Coronary Artery Disease.

IMPORTANCE: Aortic stenosis (AS) and coronary artery disease (CAD) frequently coexist. However, it is unknown which genetic and cardiovascular risk factors might be AS-specific and which could be shared between AS and CAD. OBJECTIVE: To identify genetic risk loci and cardiovascular risk factors with AS-specific associations. DESIGN, SETTING, AND PARTICIPANTS: This was a genomewide association study (GWAS) of AS adjusted for CAD with participants from the European Consortium for the Genetics of Aortic Stenosis (EGAS) (recruited 2000-2020), UK Biobank (recruited 2006-2010), Estonian Biobank (recruited 1997-2019), and FinnGen (recruited 1964-2019). EGAS participants were collected from 7 sites across Europe. All participants were of European ancestry, and information on comorbid CAD was available for all participants. Follow-up analyses with GWAS data on cardiovascular traits and tissue transcriptome data were also performed. Data were analyzed from October 2022 to July 2023. EXPOSURES: Genetic variants. MAIN OUTCOMES AND MEASURES: Cardiovascular traits associated with AS adjusted for CAD. Replication was performed in 2 independent AS GWAS cohorts. RESULTS: A total of 18 792 participants with AS and 434 249 control participants were included in this GWAS adjusted for CAD. The analysis found 17 AS risk loci, including 5 loci with novel and independently replicated associations (RNF114A, AFAP1, PDGFRA, ADAMTS7, HAO1). Of all 17 associated loci, 11 were associated with risk specifically for AS and were not associated with CAD (ALPL, PALMD, PRRX1, RNF144A, MECOM, AFAP1, PDGFRA, IL6, TPCN2, NLRP6, HAO1). Concordantly, this study revealed only a moderate genetic correlation of 0.15 (SE, 0.05) between AS and CAD (P = 1.60 × 10-3). Mendelian randomization revealed that serum phosphate was an AS-specific risk factor that was absent in CAD (AS: odds ratio [OR], 1.20; 95% CI, 1.11-1.31; P = 1.27 × 10-5; CAD: OR, 0.97; 95% CI 0.94-1.00; P = .04). Mendelian randomization also found that blood pressure, body mass index, and cholesterol metabolism had substantially lesser associations with AS compared with CAD. Pathway and transcriptome enrichment analyses revealed biological processes and tissues relevant for AS development. CONCLUSIONS AND RELEVANCE: This GWAS adjusted for CAD found a distinct genetic risk profile for AS at the single-marker and polygenic level. These findings provide new targets for future AS research.

Humans↗

Blockade of atrial-specific K+-currents increases atrial but not ventricular contractility by enhancing reverse mode Na+/Ca2+-exchange.

BACKGROUND: AVE0118 (2'-{[2-(4-Methoxy-phenyl)-acetylamino]-methyl}-biphenyl-2-carboxylic acid (2-pyridin-3-yl-ethyl)-amide) blocks atrial ultrarapid delayed rectifier currents (I(Kur)) and prolongs the atrial action potential (AP) plateau without affecting ventricular repolarisation. In patients with atrial contractile dysfunction due to atrial tachyarrhythmias, this response might increase atrial contractility without risk of ventricular proarrhythmia. This study was designed to evaluate the inotropic mechanisms of AVE0118. METHODS AND RESULTS: In isometrically contracting atrial trabeculae, AVE0118 increased contractile force by 55.4% in sinus rhythm patients (n = 9) and by 107.4% in patients with atrial fibrillation (n = 8). In freshly isolated canine atrial myocytes studied under perforated patch current clamp (37 degrees C), AVE0118 increased myocyte fractional shortening from 3.8+/-0.6 to 9.6+/-0.8% and prolonged action potential duration at 30% repolarisation from 9+/-2 to 102+/-11 ms. Clamping cells to an AP waveform recorded during exposure to AVE0118 produced the same inotropic response as the drug itself. In action potential clamp, peak Ca2+ inward current (I(CaL)) current declined from 5.5+/-1.3 pA/pF during control to 4.1+/-0.7 pA/pF when an AP recorded in the presence of AVE0118 was used as command waveform. However, I(CaL) was more sustained with AVE0118 and the time integral did not change (135+/-37 vs. 173+/-30 pA/pFms, p = ns). Importantly, blockade of reverse mode Na+/Ca2+-exchanger activity with 5 microM KBR7943 or using a Na+-free pipette solution abolished the positive inotropic effect of the AP recorded in the presence of AVE0118. In ventricular myocytes AVE0118 did not elicit a positive inotropic response. CONCLUSIONS: Block of I(Kur) by AVE0118 enhances atrial contractility both in patients with sinus rhythm and atrial fibrillation. The positive inotropic effect is atrial-specific and due to the changes of the action potential configuration which enhances Ca2+ entry via reverse mode Na+/Ca2+ exchange.

Action Potentials↗

Imaging of the coronary venous system: retrograde coronary sinus angiography versus venous phase coronary angiograms.

BACKGROUND: Left ventricular lead implantation for cardiac resynchronization therapy (CRT) usually requires a pre- or intraprocedural occlusion contrast venography of the coronary sinus (CS) in order to identify tributaries to the lateral wall. As many patients undergo a preprocedural coronary angiogram, we investigated the diagnostic accuracy of venous phase imaging of the CS in patients prior to CRT implantation. The aim of this study was to assess the quality of venous phase coronary sinus angiography. METHODS: In 24 CRT patients retrograde occlusion venography and venous phase coronary sinus angiography obtained during coronary angiography were compared with respect to image quality, vessel diameters and the ability to identify a coronary sinus side branch suitable for left ventricular lead placement. RESULTS: Suitable target vessels for left ventricular lead implantation were identified in all patients irrespective of the method (retrograde occlusion venography or venous phase coronary sinus angiography). There was a high concordance in vessel diameters between venous phase and retrograde angiography. Visibility was superior in retrograde venography. CONCLUSIONS: In heart failure patients who are scheduled for coronary angiograms venous phase coronary sinus angiography is a time-saving and easy to perform alternative imaging modality. Radiation exposure and the amount of contrast medium needed is reduced as compared to coronary sinus occlusion angiography. The information obtained thereby may be used to plan subsequent CRT implantation without the need for retrograde coronary sinus angiography.

Aged↗

Polymer-based paclitaxel-eluting stents are superior to nonpolymer-based paclitaxel-eluting stents in the treatment of de novo coronary lesions.

Although polymer coating of coronary stents enables sufficient loading and release of incorporated drugs, it has also been associated with potentially negative effects. This study compared the clinical, angiographic, and intravascular ultrasound (IVUS) outcomes of patients treated with polymer- versus nonpolymer-based paclitaxel-eluting stents (PESs). Sixty-five consecutive patients (70 de novo lesions) treated with polymer-based PESs (TAXUS, 1 microg/mm2 of paclitaxel; Boston Scientific Corp.) and 65 consecutive patients (65 de novo lesions) treated with nonpolymer-based PESs (V-Flex Plus, 2.7 microg/mm2 of paclitaxel; Cook, Inc.) were enrolled in the study. Six-month angiographic follow-up was performed on 54 lesions of the polymer-based PES group and 51 lesions of the nonpolymer-based PES group. IVUS at angiographic follow-up was performed in 61 of the first 70 included lesions. At 6-month IVUS follow-up, mean intimal hyperplasia cross-sectional area was 2.36 +/- 1.60 mm2 in the nonpolymer-based PES group versus 0.62 +/- 0.41 mm2 in the polymer-based PES group (p = 0.003). Implantation of polymer-based PESs resulted in significantly lower in-stent late lumen loss (0.22 +/- 0.27 vs 0.74 +/- 0.61 mm, respectively, p <0.001). In-stent binary restenosis rate was 5% versus 20%, respectively (p <0.001). Target lesion revascularization rate was 9% after implantation of polymer-based PES versus 18% (p = 0.128) after implantation of nonpolymer-based PES, and the major adverse cardiac event rate was 9% versus 23%, respectively (p = 0.032). In conclusion, polymer-based PESs result in superior angiographic and IVUS follow-up findings compared with nonpolymer-based PESs.

Coronary Angiography↗

Positive effects of nitric oxide on left ventricular function in humans.

AIMS: The myocardial effect of tonically released nitric oxide (NO) in humans is still not known. We tested the hypothesis that low-dose NO exerts positive effects on left ventricular (LV) function. METHODS AND RESULTS: Twelve healthy volunteers, 26+/-4 years, were enrolled in this study. Magnetic resonance imaging was used to precisely measure the direct effects of NO on stroke volume index (SVI). The NO pool was monitored by chemiluminescence. We reduced endogenous NO levels with intravenous infusion of the NO synthase-inhibitor N(G)-monomethyl-l-arginine. Replenishment of the NO pool was achieved with the NO donor S-nitrosoglutathione (GSNO) (0.5 micromol iv). To differentiate load-dependent from the direct effects of NO on LV function, changes in SVI in response to GSNO were compared with changes in the NO-independent vasodilator dihydralazine (2.5 mg iv) at matched arterial pressure and heart rate. Inhibition of NO synthesis was followed by reduction in SVI. Subsequent replenishment of the circulating NO with GSNO significantly increased SVI (39+/-8 to 54+/-7 mL m(-2); P=0.001), whereas no significant changes were observed with the NO-independent vasodilator dihydralazine (39+/-8 to 46+/-8 mL m(-2); P=0.0626). CONCLUSION: Inhibition of endogenous NO release reduces, whereas replenishment with exogenous NO increases LV function, pointing towards a positive effect of tonically released NO on LV function in healthy humans.

Adult↗

Plasma nitrite reserve and endothelial function in the human forearm circulation.

Attenuation of endothelium-derived nitric oxide (NO) synthesis is a hallmark of endothelial dysfunction. Early detection of this disorder may have therapeutic and prognostic implications. Plasma nitrite mirrors acute and chronic changes in endothelial NO-synthase activity. We hypothesized that local plasma nitrite concentration increases during reactive hyperemia of the forearm, reflecting endothelial function. In healthy subjects (n = 11) plasma nitrite and nitrate were determined at baseline and during reactive hyperemia of the forearm using reductive gas-phase chemiluminescence and flow-injection analysis, respectively. Endothelium-dependent dilation of the brachial artery was measured as flow-mediated dilation (FMD) using high-resolution ultrasound. Results were compared to patients with endothelial dysfunction as defined by reduced FMD (n = 11). Reactive hyperemia of the forearm increased local plasma nitrite concentration from 68 +/- 5 to 126 +/- 13 nmol/L (p < 0.01), whereas in endothelial dysfunction nitrite remained unaffected (116 +/- 12 to 104 +/- 10 nmol/L; n.s.), corresponding to nitrite reserves of 94 +/- 21 and -8 +/- 4%. This was accompanied by a significantly greater increase in brachial artery diameter (FMD: 8.5 +/- 0.4% vs 2.9 +/- 0.5%, for healthy subjects and endothelial dysfunction, respectively; p < 0.001). This observation suggests that nitrite changes reflect endothelial function. Assessment of local plasma nitrite during reactive hyperemia may open new avenues in the diagnosis of vascular function.

Adult↗

Circulating NO pool in humans.

Nitric oxide (NO) generated from L-arginine by NO synthases in the endothelium and in other cells plays a central role in several aspects of vascular biology and has been linked to many regulatory functions in mammalian cells. Whereas for a long time the signaling actions of NO in the vasculature have been thought to be short-lived as a result of the rapid reaction of NO with hemoglobin, recent studies changed the biochemical thinking of NO. NO is not anymore the paracrine agent with only local effects, but, like a hormone, it disseminates throughout the body. Thus, a circulating pool of NO exists, opening new considerable pharmacological and therapeutical avenues in the diagnosis and therapy of cardiovascular diseases. In this review we briefly discuss the major routes of NO metabolism and transport in the mammalian circulation, considering plasma, red blood cell and tissue compartments separately, with a special focus on the implication of the circulating NO pool in clinical research.

Amines↗

Plasma nitroso compounds are decreased in patients with endothelial dysfunction.

OBJECTIVES: We investigated whether plasma nitros(yl)ated species (RXNOs) that mediate systemic nitric oxide (NO) bioactivity are depleted in individuals with cardiovascular risk factors and endothelial dysfunction. BACKGROUND: Endothelium-derived NO acts not only as a regional messenger but exerts significant systemic effects via formation of circulating RXNOs delivering NO to sites of impaired production. METHODS: Endothelial function was assessed in 68 patients with one to four major cardiovascular risk factors (RF) and 39 healthy control subjects (C) by measurement of flow-mediated dilation (FMD) of the brachial artery using high-resolution ultrasound. In parallel, plasma RXNOs were determined by reductive gas phase chemiluminescence. RESULTS: Increasing numbers of risk factors were accompanied by a progressive decrease in FMD: 6.5 +/- 0.4% (C); 4.7 +/- 0.5% (one RF); 2.8 +/- 0.4% (two RF); 2.2 +/- 0.4% (three RF); and 1.0 +/- 0.3% (four RF). Progressively impaired vascular function was associated with a concomitant decrease in plasma RXNOs (p < 0.01): 39 +/- 2 nmol/l (C); 30 +/- 2 nmol/l (one RF); 24 +/- 3 nmol/l (two RF); 22 +/- 3 nmol/l (three RF); and 15 +/- 2 nmol/l (four RF), with univariate correlation between FMD and RXNO (r = 0.41, p < 0.001). In a multivariate regression model, RXNO was an independent predictor of endothelial function. CONCLUSIONS: Endothelial dysfunction in patients with cardiovascular risk factors is associated with decreased levels of circulating RXNOs. Plasma RXNOs may be diagnostically useful markers of NO bioavailability and a surrogate index of endothelial function. Whether the observed decrease in concentration reflects impaired NO formation, accelerated decomposition, and/or consumption of RXNOs and whether these processes play a causal role in the pathophysiology of arteriosclerosis remain to be investigated.

Adult↗

(-)-Epicatechin mediates beneficial effects of flavanol-rich cocoa on vascular function in humans.

Epidemiological and medical anthropological investigations suggest that flavanol-rich foods exert cardiovascular health benefits. Endothelial dysfunction, a prognostically relevant key event in atherosclerosis, is characterized by a decreased bioactivity of nitric oxide (NO) and impaired flow-mediated vasodilation (FMD). We show in healthy male adults that the ingestion of flavanol-rich cocoa was associated with acute elevations in levels of circulating NO species, an enhanced FMD response of conduit arteries, and an augmented microcirculation. In addition, the concentrations and the chemical profiles of circulating flavanol metabolites were determined, and multivariate regression analyses identified (-)-epicatechin and its metabolite, epicatechin-7-O-glucuronide, as independent predictors of the vascular effects after flavanol-rich cocoa ingestion. A mixture of flavanols/metabolites, resembling the profile and concentration of circulating flavanol compounds in plasma after cocoa ingestion, induced a relaxation in preconstricted rabbit aortic rings ex vivo, thus mimicking acetylcholine-induced relaxations. Ex vivo flavanol-induced relaxation, as well as the in vivo increases in FMD, were abolished by inhibition of NO synthase. Oral administration of chemically pure (-)-epicatechin to humans closely emulated acute vascular effects of flavanol-rich cocoa. Finally, the concept that a chronic intake of high-flavanol diets is associated with prolonged, augmented NO synthesis is supported by data that indicate a correlation between the chronic consumption of a cocoa flavanol-rich diet and the augmented urinary excretion of NO metabolites. Collectively, our data demonstrate that the human ingestion of the flavanol (-)-epicatechin is, at least in part, causally linked to the reported vascular effects observed after the consumption of flavanol-rich cocoa.

Administration, Oral↗

[Morphology and function of the intrinsic cardiac nervous system].

Access to the intrinsic cardiac autonomic nervous system can now be achieved via percutaneous catheter stimulation techniques. Thereby, cardiac functions like atrioventricular nodal conduction, sinus cycle length and ventricular inotropy can be dynamically regulated. The present article provides examples of this new technique in acute and chronic models but also first human applications.

Animals↗

Predictors of death or myocardial infarction during follow-up after coronary stenting with the sirolimus-eluting stent. Results from the prospective multicenter German Cypher Stent Registry.

BACKGROUND: Drug-eluting coronary stents are the most recent "breakthrough" technology in interventional cardiology. Whereas risk factors influencing restenosis and need for target vessel revascularization are well known, risk factors for dying or developing a myocardial infarction (MI) after drug-eluting coronary stent implantation need to be evaluated yet. METHODS: We evaluated data from the German Cypher Stent Registry. RESULTS: From April 2002 to December 2004, 7445 patients at 122 hospitals, who received at least one sirolimus-eluting stent during percutaneous coronary intervention, were included. Complete follow-up at a median of 6.6 months (quartiles 6.1-8.1 months) was available in 6755 patients (91%). Death occurred in 1.8% (120/6755) of patients, nonfatal MI in 2.3% (156/6635), and death or MI in 4.1% (276/6755) of patients. Independent predictors of death or MI were initial presentation with ST-elevation MI or non-ST-elevation MI (OR [odds ratio] 2.21, 95% CI 1.66-2.95, P < .0001), cardiogenic shock (OR 3.05, 95% CI 1.67-5.55, P = .0003), renal insufficiency (OR 1.74, 95% CI 1.24-2.44, P = .0017), reduced left ventricular function (OR 1.74, 95% CI 1.21-2.50, P = .0027), age (per decade) (OR 1.19, 95% CI 1.05-1.36, P = .0058), diabetes mellitus (OR 1.39, 95% CI 1.05-1.84, P = .0183), 3-vessel disease (OR 1.32, 95% CI 0.99-1.77, P = .043), and prior MI (OR 1.35, 95% CI 1.01-1.80, P = .0468), whereas interventional and lesion characteristics showed no significant association. CONCLUSIONS: These results demonstrate that the most powerful predictors of death or MI after sirolimus-eluting stent implantation during percutaneous coronary intervention are presentation with an acute coronary syndrome, impaired left ventricular ejection fraction, and conventional risk factors for coronary heart disease. Interventional and lesion characteristics do not play a major role.

Acute Disease↗

Flavanols and cardiovascular health: effects on the circulating NO pool in humans.

Atherosclerosis is the major cause for chronic vascular diseases. The key event in the pathogenesis of atherosclerosis is believed to be dysfunction of the endothelium and disruption of endothelial homeostasis, leading to vasoconstriction, inflammation, leukocyte adhesion, thrombosis, and proliferation of vascular smooth muscle cells. Endothelium-derived nitric oxide (NO) plays a major role in vascular homeostasis and a decrease in NO-bioavailability accelerates the development of atherosclerosis. Given that endothelial dysfunction is at least in part reversible, the characterization of endothelial function and therapeutical approaches have gained much attention over the past years. Recent studies demonstrated that especially the consumption of plant-derived foods rich in certain flavonoids can improve endothelial function in both compromised and healthy humans. Furthermore, various physiologic and biochemical measures have been used previously as biomarkers for the assessment of the proposed beneficial effects of flavonoids in this context. More recently, the analysis of plasma nitros(yl)ated species (RXNOs), referred to as the circulating NO pool, has gained recognition, especially as a marker for endothelial function. This review is aimed at evaluating the suitability of quantifying this NO pool as a biomarker for cardiovascular function in humans, in particular during dietary interventions with flavonoid-rich foods.

Endothelium, Vascular↗

Endothelial function, nitric oxide, and cocoa flavanols.

Endothelial dysfunction is the pathophysiologic principle involved in the initiation and progression of arteriosclerosis, thus endothelial function serves as a "barometer" for cardiovascular health that can be used for the evaluation of new therapeutic strategies. This review provides an introduction to the concept of endothelial dysfunction, and it explores the importance of this prognostic marker in the context of clinical, dietary interventions in humans. Moreover, we summarize and evaluate the findings of various clinical trials that demonstrated an improvement of endothelial dysfunction in subjects with cardiovascular risk factors after the acute and chronic consumption of flavanol-rich foods, including cocoa products, red wine, and tea.

Cacao↗

Red blood cells express a functional endothelial nitric oxide synthase.

The synthesis of nitric oxide (NO) in the circulation has been attributed exclusively to the vascular endothelium. Red blood cells (RBCs) have been demonstrated to carry a nonfunctional NO synthase (NOS) and, due to their huge hemoglobin content, have been assumed to metabolize large quantities of NO. More recently, however, RBCs have been identified to reversibly bind, transport, and release NO within the cardiovascular system. We now provide evidence that RBCs from humans express an active and functional endothelial-type NOS (eNOS), which is localized in the plasma membrane and the cytoplasm of RBCs. This NOS is regulated by its substrate L-arginine, by calcium, and by phosphorylation via PI3 kinase. RBC-NOS activity regulates deformability of RBC membrane and inhibits activation of platelets. The NOS-dependent conversion of L-arginine in RBCs is comparable to that of cultured human endothelial cells. RBCs in eNOS-/- mice in contrast to wild-type mice lack NOS protein and activity, strengthening the evidence of an eNOS in RBCs. These data show an eNOS-like protein and activity in RBCs serving regulatory functions in RBCs and platelets, which may stimulate new approaches in the treatment of NO deficiency states inherent to several vascular and hematologic diseases.

Base Sequence↗

Plasma nitrite concentrations reflect the degree of endothelial dysfunction in humans.

A reduced nitric oxide availability is a hallmark of endothelial dysfunction occurring early in atherosclerosis. Recently, we have shown that plasma nitrite mirrors acute changes in endothelial nitric oxide synthase activity in various mammals, including humans. Here, we examined the hypothesis that plasma nitrite levels are reduced in humans with endothelial dysfunction and the decrease is correlated with increasing numbers of cardiovascular risk factors (RF). Plasma nitrite concentrations were quantified by flow-injection analysis. The coefficient of variation for repeated measurements of plasma nitrite was <8%, and heart rate and blood pressure at the time of blood sampling had no significant effect on nitrite values measured (n=10). Baseline levels of plasma nitrite followed a normal distribution in each group studied and decreased progressively with increasing numbers of cardiovascular risk factors (n=351, p<0.001): 351+/-13 (0 RF), 261+/-10 (1 RF), 253+/-11 (2 RF), 222+/-18 (3 RF), and 171+/-29 nmol/L (4 RF). Intima media thickness (IMT) and flow-mediated dilation (FMD) were determined via ultrasound. Plasma nitrite and FMD levels were lower, whereas IMT was greater in individuals with endothelial dysfunction (n=12) compared to healthy volunteers (n=12). Nitrite correlated significantly with FMD (r=0.56, p<0.001) and inversely with IMT (r= -0.49, p<0.01). Plasma nitrite levels are reliably measurable in humans, indicate endothelial dysfunction, and correlate with cardiovascular risk factors. Future studies are necessary to identify the prognostic relevance of plasma nitrite determination in patients suffering from cardiovascular disease.

Adult↗

Acute consumption of flavanol-rich cocoa and the reversal of endothelial dysfunction in smokers.

OBJECTIVES: This study was designed to assess the effect of flavanol-rich food on the circulating pool of bioactive nitric oxide (NO) and endothelial dysfunction in smokers. BACKGROUND: Studies suggest that smoking-related vascular disease is caused by impaired NO synthesis and that diets rich in flavanols can increase bioactive NO in plasma. METHODS: In smokers (n = 11), the effects of flavanol-rich cocoa on circulating NO species in plasma (RXNO) measured by reductive gas-phase chemiluminescence and endothelial function as assessed by flow-mediated dilation (FMD) were characterized in a dose-finding study orally administering cocoa containing 88 to 370 mg flavanols and in a randomized double-blind crossover study using 100 ml cocoa drink with high (176 to 185 mg) or low (<11 mg) flavanol content on two separate days. In addition to cocoa drink, ascorbic acid and NO-synthase inhibitor L-NMMA (n = 4) were applied. RESULTS: There were significant increases in RXNO (21 +/- 3 nmol/l to 29 +/- 5 nmol/l) and FMD (4.5 +/- 0.8% to 6.9 +/- 0.9%, each p < 0.05) at 2 h after ingestion of 176 to 185 mg flavanols, a dose potentially exerting maximal effects. These changes correlated with increases in flavanol metabolites. Cocoa-associated increases in RXNO and FMD were reversed by L-NMMA. Ascorbic acid had no effect. CONCLUSIONS: The circulating pool of bioactive NO and endothelium-dependent vasodilation is acutely increased in smokers following the oral ingestion of a flavanol-rich cocoa drink. The increase in circulating NO pool may contribute to beneficial vascular health effects of flavanol-rich food.

Adult↗