A novel troponin T peptide in humans: Assay, biochemistry and preliminary findings in acute coronary syndromes.

INTRODUCTION: High sensitivity assays for cardiac troponin (cTn) have reduced time to diagnosis of myocardial infarction (MI) but at costs to diagnostic specificity. We hypothesised that measurement of an upstream open reading frame peptide (uORF) from the human cTnT gene (TnTuORF) might improve cTn specificity in MI patients. METHODS: A novel immunoassay to TnTuORF was developed and used to document circulating concentrations in normal healthy volunteers (n=150); assess potential trans-organ secretion in patients undergoing cardiac catheterisation (n=16); characterise temporal TnTuORF concentrations during ST-elevation MI (STEMI, n=4) and assess the potential of TnTuORF to assist the diagnosis and prognosis of MI in patients presenting with chest pain suspicious of ACS (n=502). Plasma immunoreactive TnTuORF was characterised on reverse phase and size exclusion HPLC. RESULTS: In normal volunteers and suspected acute coronary syndrome (ACS) patients, TnTuORF had no relationship with TnI or TnT. Trans-organ venous sampling suggested TnTuORF secretion is not exclusively cardiac based. In STEMI patients, TnTuORF concentrations decreased for up to 12h after onset. In suspected ACS patients, TnTuORF could not diagnose MI (ROC AUC=0.446, P=0.117) but could diagnose cardiac disorders other than MI (AUC=0.79, P<0.001). CONCLUSION: This is the first evidence for a circulating uORF peptide. TnTuORF does not appear to aid the diagnosis of MI but further studies to assess its potential in cardiovascular disease are required.

Genetic markers of repolarization and arrhythmic events after acute coronary syndromes.

BACKGROUND: There is a genetic contribution to the risk of ventricular arrhythmias in survivors of acute coronary syndromes (ACS). We wished to explore the role of 33 candidate single nucleotide polymorphisms (SNPs) in prolonged repolarization and sudden death in patients surviving ACS. METHODS: A total of 2,139 patients (1680 white ethnicity) surviving an admission for ACS were enrolled in the prospective Coronary Disease Cohort Study. Extensive clinical, echocardiographic, and neurohormonal data were collected for 12 months, and clinical events were recorded for a median of 5 years. Each SNP was assessed for association with sudden cardiac death (SCD)/cardiac arrest (CA) and prolonged repolarization at 3 time-points: index admission, 1 month, and 12 months postdischarge. RESULTS: One hundred six SCD/CA events occurred during follow-up (6.3%). Three SNPs from 3 genes (rs17779747 [KCNJ2], rs876188 [C14orf64], rs3864180 [GPC5]) were significantly associated with SCD/CA in multivariable models (after correction for multiple testing); the minor allele of rs17779747 with a decreased risk (hazard ratio [HR] 0.68 per copy of the minor allele, 95% CI 0.50-0.92, P = .012), and rs876188 and rs386418 with an increased risk (HR 1.52 [95% CI 1.10-2.09, P = .011] and HR 1.34 [95% CI 1.04-1.82, P = .023], respectively). At 12 months postdischarge, rs10494366 and rs12143842 (NOS1AP) were significant predictors of prolonged repolarization (HR 1.32 [95% CI 1.04-1.67, P = .022] and HR 1.30 [95% CI 1.01-1.66, P = .038], respectively), but not at earlier time-points. CONCLUSION: Three SNPs were associated with SCD/CA. Repolarization time was associated with variation in the NOS1AP gene. This study demonstrates a possible role for SNPs in risk stratification for arrhythmic events after ACS.

Genetic variation in the renin-angiotensin-aldosterone system is associated with cardiovascular risk factors and early mortality in established coronary heart disease.

This study examined renin-angiotensin-aldosterone (RAAS) system gene variants for associations with cardiovascular risk factors and outcomes in coronary heart disease. Coronary disease patients (n=1186) were genotyped for 21 single-nucleotide polymorphisms (SNPs) within angiotensinogen (AGT), angiotensin-converting enzyme (ACE), angiotensin-II type-1 receptor (AGTR1) and aldosterone synthase (CYP11B2). Associations with all-cause mortality and cardiovascular readmissions were assessed over a median of 3.0 years. The AGT M235T 'T' allele was associated with a younger age of clinical coronary disease onset (P=0.006), and the AGT rs2478545 minor allele was associated with lower circulating natriuretic peptides (P=0.0001-P=0.001) and E/E(1) (P=0.018). Minor alleles of AGT SNPs rs1926723 and rs11122576 were associated with more frequent history of renal disease (P0.04) and type-2 diabetes (P0.02), higher body mass index (P0.02) and greater mortality (P0.007). AGT rs11568054 minor allele carriers had more frequent history of renal disease (P=0.04) and higher plasma creatinine (P=0.033). AGT rs6687360 minor allele carriers exhibited worse survival (P=0.02). ACE rs4267385 was associated with older clinical coronary disease onset (P=0.008) and hypertension (P=0.013) onset, increased plasma creatinine (P=0.01), yet greater mortality (P=0.044). Less history of hypertension was observed with the AGTR1 rs12685977 minor allele (P=0.039). Genetic variation within the RAAS was associated with cardiovascular risk factors and accordingly poorer survival.

Integrated microscopy techniques for comprehensive pathology evaluation of an implantable left atrial pressure sensor.

The safety and efficacy of an implantable left atrial pressure (LAP) monitoring system is being evaluated in a clinical trial setting. Because the number of available specimens from the clinical trial for histopathology analysis is limited, it is beneficial to maximize the usage of each available specimen by relying on integrated microscopy techniques. The aim of this study is to demonstrate how a comprehensive pathology analysis of a single specimen may be reliably achieved using integrated microscopy techniques. Integrated microscopy techniques consisting of high-resolution gross digital photography followed by micro-computed tomography (micro-CT) scanning, low-vacuum scanning electron microscopy (LVSEM), and microground histology with special stains were applied to the same specimen. Integrated microscopy techniques were applied to eight human specimens. Micro-CT evaluation was beneficial for pinpointing the location and position of the device within the tissue, and for identifying any areas of interest or structural flaws that required additional examination. Usage of LVSEM was reliable in analyzing surface topography and cell type without destroying the integrity of the specimen. Following LVSEM, the specimen remained suitable for embedding in plastic and sectioning for light microscopy, using the positional data gathered from the micro-CT to intersect areas of interest in the slide. Finally, hematoxylin and eosin (H&E) and methylene blue staining was deployed on the slides with high-resolution results. The integration of multiple techniques on a single specimen maximized the usage of the limited number of available specimens from the clinical trial setting. Additionally, this integrated microscopic evaluation approach was found to have the added benefit of providing greater assurance of the derived conclusions because it was possible to cross-validate the results from multiple tests on the same specimen.

CYP2D6 genotype and its relationship with metoprolol dose, concentrations and effect in patients with systolic heart failure.

The aims of this study were to examine the relationships between CYP2D6 genotype and metoprolol dose, S- and R-metoprolol concentrations and clinical effects in patients with systolic heart failure. Data were obtained for 52 subjects, of which 27 had 2 functional alleles (24/27, CYP2D6*1/*1), 22 had 1 functional allele (18/22, CYP2D6*1/*4) and 3 had no functional alleles (CYP2D6*4/*4). Median dose-adjusted concentrations of S-metoprolol (active) were 6.3- and 3.2-fold higher in subjects with zero or one functional allele (P=0.016 and P=0.006), respectively, compared with subjects with two functional alleles. For the R-enantiomer (inactive), these concentrations were 10.7- and 3.7-fold higher (P=0.013 and P=0.003), respectively. Despite clear gene-concentration differences, no relationships between CYP2D6 genotype and dose or clinical effects could be shown. Although the number with no functional alleles was too small (n=3) to show effects, in patients with 1 functional allele other sources of variance are likely to be obscuring differences in clinical effects.

B-type natriuretic peptide infusions in acute myocardial infarction.

BACKGROUND: Natriuretic peptides have actions likely to ameliorate cardiac dysfunction. B-type natriuretic peptide (BNP) is indicated as treatment for decompensated cardiac failure. OBJECTIVE: To determine the utility of BNP in acute myocardial infarction (MI). DESIGN: Double-blind randomised placebo-controlled trial. SETTING: Tertiary hospital coronary care unit. PATIENTS: 28 patients with acute MI with delayed or failed reperfusion and moderate left ventricular dysfunction. INTERVENTIONS: Infusion of BNP or placebo for 60 hours after MI. MAIN OUTCOME MEASURES: Neurohormonal activation and renal function in response to BNP infusion, secondary end points of echocardiographic measures of left ventricular function and dimension. RESULTS: BNP infusion resulted in a significant rise in BNP (276 pg/l vs 86 pg/l, p = 0.001). NT-proBNP levels were suppressed by BNP infusion (p = 0.002). Atrial natriuretic peptide (ANP) and NT-proANP levels fell with a significant difference in the pattern between BNP infusion and placebo during the first 5 days (p<0.005). C-type natriuretic peptide (CNP) and NT-proCNP levels rose during the infusion with higher levels than placebo at all measurements during the first 3 days (p<0.01). Cyclic guanosine monophosphate (cGMP) was raised during the infusion period showing a peak of 23 pmol/l on day 2 (placebo 8.9 pmol/l, p = 0.002), with a correlation between BNP and cGMP levels (p<0.001). Glomerular filtration rate (GFR) fell with BNP infusion but was not significantly lower than with placebo (71.0 (5.6) vs 75.8 (5.4) ml/min/1.73 m2, p = 0.62). Patients receiving nesiritide exhibited favourable trends in left ventricular remodelling. CONCLUSIONS: Nesiritide, given soon after MI, induced increments in plasma cGMP and CNP and decrements in other endogenous cardiac peptides with a neutral effect on renal function and a trend towards favourable ventricular remodelling.

B-type natriuretic peptide levels are not a surrogate marker for invasive hemodynamics during management of patients with severe heart failure.

BACKGROUND: We sought to assess the utility of serial BNP measurements in patients with severe heart failure and attempted to correlate values with invasively derived data. METHODS: In a retrospective study, we analyzed serial BNP levels in patients receiving hemodynamically guided therapy for severe heart failure and sought correlation with invasively derived data. RESULTS: Thirty-nine patients with New York Heart Association Class III-IV, with an ejection fraction of 35% or less, who had a pulmonary artery catheter inserted for hemodynamically tailored heart failure therapy, were identified and serial BNP measurements reviewed. BNP was estimated on admission, at 12 and 36 hours. Normally distributed variables are expressed as mean +/- SD and otherwise as median +/- interquartile range. Mean ejection fraction was 16% +/- 6%. Mean pulmonary artery occlusion pressures (PAOP) fell with therapy and were 25 +/- 7 mmHg, 18 +/- 7 mmHg and 19 +/- 7 mmHg at admission, 12 hours and 36 hours respectively ( P < 0.05). Median BNP levels fell from 1200 +/- 641 to 771 +/- 803 at 12 hours and to 805 +/- 771 at 36 hours (P < .001). There was no correlation between BNP and any hemodynamically derived variable. A change in BNP was not associated with a change in PAOP in any individual patient. Only 42% remained alive on medical therapy at 30 days. CONCLUSIONS: In patients with severe heart failure, BNP levels do not accurately predict serial hemodynamic changes and do not obviate the need for pulmonary artery catheterization.

Brain natriuretic peptide-guided therapy for heart failure.

The drug treatment of heart failure, once simple, has become complex. Apart from a loop diuretic and digoxin, most patients should now be receiving an angiotensin-converting enzyme inhibitor (or angiotensin II receptor blocker), a beta-blocker and spironolactone. Newer drugs, such as endothelin-receptor antagonists and combined blockers of converting-enzyme and neutral endopeptidase, might soon become available. When to introduce these drugs and what dose is optimal for any individual, are questions that currently vex clinicians. We proposed that plasma levels of the cardiac hormone brain natriuretic peptide (BNP, or better, its 1-76 amino-acid N-terminal fragment, N-BNP), would provide an objective index for guiding drug treatment in patients with established, stable cardiac failure. In a pilot study, 69 patients were randomized to drug treatment based on clinical criteria, or based on plasma levels of N-BNP. After a median follow-up of 9.6 months, those in the N-BNP group had fewer clinical end-points than those in the group managed by clinical criteria alone (19 vs 54; P= 0.02). These preliminary data encourage the concept that the increasingly complex pharmacotherapy for heart failure, both chronic (as in this trial) and acute, might best be guided by an objective measure such as plasma levels of BNP or N-BNP.

Differing thresholds for modulatory effects of adrenomedullin infusion on haemodynamic and hormone responses to angiotensin II and adrenocorticotrophic hormone in healthy volunteers.

Experimental data indicate that adrenomedullin (AM) interacts at various levels with the renin-angiotensin-aldosterone system and the hypothalamic-pituitary-adrenal axis, but data from humans are scant. We examined the effects of intermediate-dose, short-term AM infusion on angiotensin II- and adrenocorticotrophic hormone (ACTH)-mediated hormone and haemodynamic responses in healthy subjects. Seven normal volunteers (age 18-25 years) completed a placebo-controlled crossover study. Each subject was studied on day 4 of two periods of a low-salt diet (40 mmol of sodium and 80 mmol of potassium daily), receiving incremental infusions of angiotensin II in the morning and ACTH in the afternoon of each study day, on a background infusion of AM (4 pmol.min(-1).kg(-1)) or vehicle (hemaccel). Achieved plasma AM levels (23+/-6 pmol/l) and peak angiotensin II levels (160 pmol/l) were similar on the two experimental days. While the pressor action of angiotensin II was attenuated by AM (P<0.01) and noradrenaline levels rose (P<0.05), the aldosterone response was unaltered. During ACTH infusion, AM increased heart rate (P<0.01), plasma adrenaline (P<0.01) and plasma noradrenaline (P<0.05), and augmented the cortisol response (P<0.01), but was without effect on aldosterone levels and blood pressure. We conclude that the threshold for the effects of AM on aldosterone secretion in humans is set higher than for other biological responses to this hormone, namely blood pressure, heart rate, sympathetic activity and cortisol secretion, under these experimental conditions.

Hypotensive and natriuretic actions of adrenomedullin in subjects with chronic renal impairment.

Plasma levels of adrenomedullin are increased in chronic renal failure. The significance of this finding is uncertain, because the biological effects of adrenomedullin in renal impairment are unknown. Therefore, we studied the effects of adrenomedullin infusion in subjects with chronic renal impairment. Eight males with IgA nephropathy and plasma creatinine of 0.19+/-0.03 mmol/L (mean+/-SEM) were studied in a vehicle-controlled crossover design. Each subject was studied twice; subjects were administered either adrenomedullin at a low dose and then a high dose (2.9 and 5.8 pmol/kg per minute, respectively, for 2 hours each) or a 4-hour vehicle control (Hemaccel), in random order, on day 4 of controlled metabolic diets. Adrenomedullin infusion achieved plasma adrenomedullin concentrations in the pathophysiological range after the low (31.2+/-5.1 pmol/L) and high (47.4+/-4.3 pmol/L) dose, and plasma cAMP was increased. Compared with vehicle control, high-dose adrenomedullin increased peak heart rate (+21.7+/-3.3 bpm, P<0.01) and cardiac output (+2.9+/-0.2 L/min, P<0.01) and lowered both systolic and diastolic blood pressures by >10 mm Hg (P<0.05). Plasma renin activity, angiotensin II, and norepinephrine increased by up to 50% above baseline levels (P<0.05 for all), whereas aldosterone and epinephrine were unchanged. Urinary volume and sodium excretion increased significantly (P<0.05) with low-dose adrenomedullin, whereas creatinine clearance was stable, and proteinuria tended to decrease. In subjects with chronic renal impairment due to IgA nephropathy, adrenomedullin infusion lowered blood pressure, stimulated sympathetic activity and renin release, and caused diuresis and natriuresis. Adrenomedullin may have a role in modulating blood pressure and kidney function in renal disease.

Bioactivity of adrenomedullin and proadrenomedullin N-terminal 20 peptide in man.

Although the biological effects of adrenomedullin (AM) and PAMP have been reported extensively in animal studies and from in-vitro experiments, relatively little information is available on responses to the hormone administered to man. This review summarizes data from the few studies carried out in man. In healthy volunteers, i.v. infusion of AM reduces arterial pressure, probably at a lower rate of administration than is required to elicit other responses. AM stimulates heart rate, cardiac output, plasma levels of cAMP, prolactin, norepinephrine and renin whilst inhibiting any concomitant response in plasma aldosterone. Little or no increase in urine volume or sodium excretion has been observed. Patients with essential hypertension differ only in showing a greater fall in arterial pressure and in the development of facial flushing and headache. In patients with heart failure or chronic renal failure, i.v. AM has similar effects to those seen in normal subjects but also induces a diuresis and natriuresis, depending on the dose administered. Infusion of AM into the brachial artery results in a dose-related increase in forearm and skin blood flow, more prominent and more dependent on endogenous nitric oxide in healthy volunteers than in patients with cardiac failure. When infused into a dorsal hand vein, AM partially reversed the venoconstrictor action of norepinephrine. Although much more information is required to clarify the role of AM under physiological and pathophysiological circumstances, it is clear that it has prominent hemodynamic and neurohormonal effects, though generally lesser urinary effects when administered short-term in doses sufficient to raise its levels in plasma to those seen in a number of clinical disorders. The only study of PAMP in man showed that its skeletal muscle vasodilator potency, when infused into the brachial artery of healthy volunteers, was less than one hundredth that of AM, and it was without effect on skin blood flow.

Beneficial renal and hemodynamic effects of omapatrilat in mild and severe heart failure.

Omapatrilat is a member of the new drug class of vasopeptidase inhibitors that may offer benefit in the treatment of heart failure (HF) through simultaneous inhibition of angiotensin-converting enzyme and neutral endopeptidase. We examined the effects of omapatrilat in a placebo-controlled crossover study using a pacing model of HF. Seven sheep were paced sequentially at 180 bpm (mild HF) and then 225 bpm (severe HF) for 7 days each. Omapatrilat (0.005 mg/kg) or vehicle was administered by intravenous bolus on days 4 to 7 of each paced period. Omapatrilat lowered mean arterial and left atrial pressure and increased cardiac output acutely and chronically in both mild and severe HF (P<0.01 for all). Plasma atrial and brain natriuretic peptide and cGMP levels were stable acutely (P=NS), while brain natriuretic peptide increased after repeated dosing in severe HF (P<0.05). Plasma renin activity rose, whereas angiotensin II and aldosterone levels fell after acute and repeated dosing in both states (P<0.01 for all). Omapatrilat increased urinary sodium excretion by day 7 in both mild and severe HF (P<0.05). Effective renal plasma flow and glomerular filtration rate increased or were stable after omapatrilat in mild and severe HF after both acute and repeated dosing. Omapatrilat exhibited pronounced acute and sustained beneficial hemodynamic and renal effects in both mild and severe heart failure.

Hemodynamic, hormone, and urinary effects of adrenomedullin infusion in essential hypertension.

We examined the effects of the vasodilator peptide adrenomedullin (AM) infused intravenously into subjects with essential hypertension. Eight men 39 to 58 years old with uncomplicated hypertension (147/96+/-5/3 mm Hg at baseline) were studied in a placebo-controlled, crossover design. Each subject received intravenous AM in a low and a high dose (2.9 and 5.8 pmol. kg(-1). min(-1) for 2 hours each) or vehicle-control (Hemaccel) infusion in a random order on day 4 of a controlled metabolic diet (80 mmol/d Na(+), 100 mmol/d K(+)). Plasma AM reached pathophysiological levels during infusion (18+/-4 pmol/L in low dose, 34+/-9 pmol/L in high dose) with a concurrent rise in plasma cAMP (+8.4+/-1.2 pmol/L, P:<0. 05 compared with control). Compared with control, high-dose AM increased peak heart rate (+17.8+/-2.3 bpm, P<0.01), lowered systolic (-24.6+/-0.9 mm Hg; P<0.01) and diastolic (-21.9+/-1.4 mm Hg; P<0.01) blood pressure, and increased cardiac output (+1.0+/-0. 1 L/min in low dose, +2.9+/-0.2 L/min in high dose; P<0.01 for both). Despite a rise in plasma renin activity during high dose (P<0.05), aldosterone levels did not alter. Plasma norepinephrine levels increased 1295+/-222 pmol/L (P<0.001) and epinephrine increased 74+/-15 pmol/L (P<0.05) with high-dose AM compared with control. AM had no significant effect on urine volume and sodium excretion. In subjects with essential hypertension, the intravenous infusion of AM to achieve pathophysiological levels produced significant falls in arterial pressure, increased heart rate and cardiac output, and stimulated the sympathetic system and renin release without concurrent increase in aldosterone. Urinary parameters were unaltered. Although AM has potent hemodynamic and neurohumoral effects in subjects with essential hypertension, the threshold for urinary actions is set higher.

Treatment of heart failure guided by plasma aminoterminal brain natriuretic peptide (N-BNP) concentrations.

BACKGROUND: There is currently no objective practical guide to intensity of drug treatment for individuals with heart failure. We hypothesised that pharmacotherapy guided by plasma concentrations of the cardiac peptide aminoterminal brain natriuretic peptide (N-BNP) would produce a superior outcome to empirical trial-based therapy dictated by clinical acumen. METHODS: 69 patients with impaired systolic function (left-ventricular ejection fraction <40%) and symptomatic heart failure (New York Heart Association class II-IV) were randomised to receive treatment guided by either plasma N-BNP concentration (BNP group) or standardised clinical assessment (clinical group). FINDINGS: During follow-up (minimum 6-months, median 9.5 months), there were fewer total cardiovascular events (death, hospital admission, or heart failure decompensation) in the BNP group than in the clinical group (19 vs 54, p=0.02). At 6 months, 27% of patients in the BNP group and 53% in the clinical group had experienced a first cardiovascular event (p=0.034). Changes in left-ventricular function, quality of life, renal function, and adverse events were similar in both groups. INTERPRETATION: N-BNP-guided treatment of heart failure reduced total cardiovascular events, and delayed time to first event compared with intensive clinically guided treatment.

Hemodynamic, hormonal, and renal effects of short-term adrenomedullin infusion in healthy volunteers.

The actions of adrenomedullin (ADM), a 52-amino acid peptide, are not well defined in man. We, therefore, studied eight normal volunteers aged 1832 yr in a placebo-controlled crossover study. On the 2 study days, subjects received, in random order, ADM in "low" and "high" dose (2.9 pmol/kg x min and 5.8 pmol/kg x min for 2 h each) or vehicle (hemaccel) infusion on day 4 of a metabolic diet (Na+ 80 mmol/day, K+ 100 mmol/day). Achieved plasma ADM levels were in the pathophysiological range, and plasma cAMP values rose 5 pmol/L during the higher dose. Compared with time-matched vehicle infusion, high-dose ADM increased peak heart rate by 10 beats per minute (P < 0.05) and lowered diastolic (by 5 mm Hg, P < 0.01) blood pressure. Cardiac output increased in both phases of ADM (low dose, 7.6 L/min; high dose, 10.2 L/min; vehicle, 6 L/min; P < 0.05 for both). Despite a 2-fold rise in PRA during high-dose ADM (P < 0.01), aldosterone levels were unaltered. Norepinephrine levels increased by 50% during high-dose ADM (P < 0.001), but epinephrine levels were unchanged. Plasma PRL levels increased during high-dose ADM (P = 0.014). ADM had no significant effect on urine volume and sodium excretion. Infusion of ADM to achieve pathophysiological plasma levels produced significant hemodynamic effects, stimulated renin but inhibited the aldosterone response to endogenous angiotensin II, and activated the sympathetic system and PRL without altering urine sodium excretion in normal subjects.