Comparative performances of soluble urokinase plasminogen activator receptor and Mid-regional proADM to predict composite death and new heart failure rehospitalisation in acutely breathless patients

Background

Soluble urokinase plasminogen activator receptor (suPAR) is a pleotropic receptor, capable of orchestrating plaque vulnerability and vascular immune dysfunction. Mid-regional pro-adrenomedullin (MR-proADM) is the stable peptide precursor of adrenomedullin, with concentrations reflective of vasodilation and cardiac remodelling. We compared the prognostic performances of suPAR and MR-proADM for the composite clinical endpoint of death and new heart failure (HF) in patients with undifferentiated breathlessness.

Methods

Patients presenting to hospital with the primary complaint of acute dyspnoea were recruited in New Zealand (n=612) and in Singapore (n=483)]. Baseline plasma measurements were undertaken for suPAR (ViroGates) and MR-proADM (Thermo Scientific). Cardiac biomarker levels of NT-proBNP (Roche) was available on all patients. Statistical assessment was made using SPSS v28 (IBM), with all biomarkers treated as continuous variables and presented as median [interquartile range (IQR)]. Prognostic performance of suPAR, MR-proADM and NT-proBNP to predict the composite clinical endpoint of death/new HF at 90-days and 1-yr were assessed using receiver operator curve (ROC) area under the curve (AUC) analysis (Z-scores) and Cox hazard regression analysis (per doubling of biomarker concentrations) after adjustment for traditional risk factors. P-value <0.05 was considered statistically significant.

Results

In the entire acutely breathless cohort [median age: 65 years (IQR: 52.9–76.0), 63.1% males], 343/1095 of patients had the final adjudication of ADHF. suPAR and MR-proADM concentrations were higher with increasing age (Spearmans rho, r>0.46, P<0.0001), lower eGFR (r>0.58, P<0.0001) and in those with ADHF (r>0.40, P<0.0001). During the follow-up period, 122 patients were categorised with death/new HF by 90-days, rising to 281 at 1-year. suPAR and MR-proADM were able to predict death/new HF at 90-days (both ROC-AUC >0.77) and at 1-year (both ROC-AUC ≥0.78) (Table 1). All markers were however less accurate in predicting this endpoint in the presence of ADHF (ROC-AUC <0.71). After adjustment in Cox-regression modelling, suPAR obtained HR >1.35 per doubling of suPAR concentrations (P=0.001) for outcomes at 90-days and at 1-year (Table 2), achieving the highest prognostic performance for this clinical endpoint, followed by NT-proBNP (HR >1.29) (Table 2), whilst MR-proADM was not an independent predictor of death/HF in this cohort. suPAR was also an independent predictor of death/HF for patients with ADHF, obtaining HR >1.35 per doubling of concentrations. Above a cut-off concentration of 3.6 ng/mL, suPAR was associated with a HR of 2.1 (95% CI: 1.55–2.91) for death/HF at 1-year for acutely dyspnoeic patients.

Conclusion

suPAR concentrations is superior than MR-proADM in predicting the clinical end-point of death/HF at 1-year in this cohort. It may aid in risk-stratification strategies for the management of acutely breathless patients.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): National Heart Foundation of New ZealandHealth Research Council of New Zealand

150 ProBNP glycosylation of threonine 71 is increased with obesity in patients with heart failure

Funding Acknowledgements

The National Heart Foundation of New Zealand

Background

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. Plasma levels of B-type natriuretic peptide (BNP) or its amino terminal congener (NT-proBNP) are used for HF diagnosis and risk stratification.  Circulating levels of both BNP and NT-proBNP are reduced by obesity and this phenomenon is one of the key weaknesses of the diagnostic performance of the natriuretic peptides in HF.  Formation of BNP from enzymatic cleavage of proBNP1-108 between residues 76 and 77 by corin and/or furin is influenced by the degree of proBNP glycosylation, therefore we investigated the relationship between proBNP glycosylation, plasma NT-proBNP and body mass index (BMI) in HF patients.

Methods

Three assays were developed to distinguish between total proBNP (glycosylated plus non-glycosylated proBNP), proBNP not glycosylated at threonine 71 (NG-T71) and proBNP not glycosylated in the central region (NG-C). Intra and inter-assay CVs were <15%, limits of detection were <2 pmol/L and samples diluted in parallel.

Results

Applying these assays and an NT-proBNP assay to plasma samples from 106 healthy volunteers and 238 patients with HF determined that concentrations (median(IQR)) of proBNP, NG-T71 and NT-proBNP were greater in HF patients compared to controls (24.9 (3.6-55), 9.4 (1.5-21) and 212 (104-409) pmol/L vs 3.0 (1.5-19), 3.0 (1.5-14.5) and 4.7 (2-8) pmol/L respectively, all p < 0.012).  NG-C was undetectable in most samples. ProBNP levels in HF patients with BMI above and below 30 kg/m2 were not different (21.9 (2.6-70) pmol/L and 25.7 (3.9-53) pmol/L respectively, p = 0.85), whereas HF patients with BMI > 30 had lower NT-proBNP and NG-T71 levels (121 (64-248) and 3 (1.5-16) pmol/L verse 271 (178-486) and 13.5 (1.5-24.2) pmol/L respectively, p < 0.003) and higher proBNP:NT-proBNP and proBNP:NG-T71 ratios  (p = 0.001 and p = 0.02 respectively) than those with BMI < 30.

Discussion and Conclusion

Using three new assays specific for different glycosylated forms of proBNP we have shown that the processing of proBNP is dysregulated in heart failure compared to controls due to increased glycosylation at threonine 71 of proBNP.  Obese patients with HF have even greater dysregulation, demonstrated by decreased concentrations of proBNP that is not glycosylated at T71 (NG-T71), and concomitant decreases in NT-proBNP.  Thus, we have shown for the first time that increased BMI is associated with increased proBNP glycosylation at T71 in patients with heart failure.  Glycosylation-induced impairment of proBNP processing explains, at least in part, the reduction in plasma concentrations of B-type cardiac natriuretic peptides observed in obesity. Using these assays to evaluate the proBNP profile of larger patient cohorts will further develop understanding of the relationships between BNP production, BMI and heart failure pathogenesis, which would be expected to lead to increased diagnostic performance.

P1756The protein APRIL predicts adverse outcomes in DAPT patients better than NT-proBNP and troponin

Aim

Dual antiplatelet therapy (DAPT) is a mainstay of post-ACS treatment. However, prediction of adverse events in these patients needs improving. We show here that the TNFα-related protein APRIL (which is produced in platelets and atherosclerotic plaque) is a superior predictor of MACE and new MI in DAPT recipients post-ACS.

Methods

We prospectively recruited 518 patients presenting with the primary complaint of acute chest pain to our hospital ED. Patients were adjudicated to have ACS by 2 independent cardiologists in accordance with ESC guidelines with hsTnI as biomarker. Plasma EDTA samples taken at presentation and 2 hours after were interrogated for APRIL measurements using a two site ELISA. Clinical data/variables, standard biochemistry analytes, hsTnT and NT-proBNP were also measured. Statistical assessments were made using SPSS v23 (IBM). Data for all biomarkers were treated as continuous variables and are presented as median (interquartile range, (IQR)). Statistical assessment of the comparative diagnostic abilities of APRIL, hsTnT, NT-proBNP and hsTnI were assessed using receiver operator curve (ROC) area under the curve (AUC) analysis. The comparative power of each biomarker (log values) to predict new MACE, MI, bleeding and mortality in 1) the whole group and in 2) DAPT recipients alone, within 2 yrs of index presentation was undertaken using a logistic regression base model (95% CI) that included all clinical variables and hsTnI and hsTnT, with APRIL and NT-proBNP each included in additional multivariate analyses.

Results

Of the 518 recruited patients (median age 63 (IQR: 54–73, 35% female), 152 were adjudicated to have ACS (29%, 115 MI, 37 UAP). Presentation APRIL levels were higher in those with a cardiac versus non-cardiac cause for presentation (3.0, (2.0–4.7) vs. 2.4, (1.6–3.8) ng/mL, P=0.001) and positively correlated with hsTnT and NT-proBNP (all P<0.001), but it did not add to the hsTnI (ROC = 0.96) or hsTnT (ROC =0.92) assisted diagnosis of ACS. In all 518 patients, in the multivariate regression model, APRIL was a significant independent predictor of mortality (n=54, P=0.032), new MI (n=43, P=0.006), new ADHF (n=24, P=0.016) and MACE (n=71, P=0.005) that was additive to NT-proBNP and troponin. In DAPT recipients alone (n=156), APRIL was the only biomarker to independently predict new MI (n=27, 95% CI: 1.125–3.982, P=0.020) and MACE (n=37, 95% CI: 1.058–3.389, P=0.031). None of the markers, only age, predicted bleeding episodes.

Conclusion

APRIL is an platelet/plaque derived marker that provides independent risk assessment in ACS patients. In DAPT recipients, the ability of APRIL to predict new MI and MACE is superior to that of cardiac troponins and NT-proBNP and could be used to identify high risk individuals.

Acknowledgement/Funding

Health Research Council of New Zealand; Heart Foundation of New Zealand

P3408The signal peptide of CNP is a novel predictor of MI, MACE and bleeding risk in chest pain patients

Aim

CNP is an important vascular and cardiac derived member of the natriuretic peptide family. We have previously provided the first reports that the signal peptide of CNP (CNPsp) is present in the human circulation and is elevated in those with chest pain suspicious of ACS. Here, show that CNPsp levels are highly predictive of new MI, MACE and post-index bleeding in patients presenting with potential ACS.

Methods

We prospectively recruited 493 patients presenting with the primary complaint of acute chest pain to our hospital ED. Patients were adjudicated as ACS by 2 independent cardiologists in accordance with ESC guidelines with hsTnI as biomarker. Plasma EDTA samples taken at presentation and 2 hours after were interrogated for CNPsp measurements using our validated, specific assay. Clinical data/variables, standard biochemistry analytes, hsTnT and NT-proBNP (both Roche Cobas e411) were also measured. Statistical assessments were made using SPSS v23. Data for all biomarkers were treated as continuous variables and are presented as median (interquartile range, (IQR)). Statistical assessment of the comparative abilities of CNPsp, hsTnT, NT-proBNP and hsTnI (log values) to predict new MACE, MI, bleeding and mortality within 2 yrs of index presentation was undertaken using a logistic regression base model (95% CI) that included all clinical variables and hsTnI and hsTnT and NT-proBNP, with CNPsp added to into the multivariate analyses.

Results

Of the 493 recruited patients (median age 63 (IQR: 54–73, 35% female), 148 were adjudicated to have ACS (30%, 109 MI, 39 UAP). Presentation CNPsp levels were not higher in those with adjudicated ACS versus non-ACS (51, (45–65) vs. 50, (42–63) pmol/L, P=0.412), did not correlate with hsTnI, hsTnT or NT-proBNP, but were significantly lower in those with a history of MI (49, (42–59) vs. 51, (43–64) pmol/L, P=0.044). In contrast, they were significantly higher in those with ECG ST-depression (56, (47–85) vs. 50 (42–62) pmol/L, P=0.038). In the multivariate regression model of all 493 patients, lower values of CNPsp were a significant multivariate predictor of new MI (n=37, 95% CI: 0.06–0.89, P=0.038), MACE (n=64, 95% CI: 0.08–0.81, P=0.020) and new bleeding (n=40, 95% CI: 0.05–0.63, P=0.005) within 2 years of presentation. This predictive ability was additive and independent from NT-proBNP and troponin.

Conclusion

This is the first report that CNPsp measurement provides meaningful and independent risk assessment of important outcomes in ACS patients. In particular, the fact that lower levels of CNPsp are predictive of negative MI, MACE and bleeding outcomes suggests that CNPsp may have an unappreciated protective role in the cardiovascular system.

Acknowledgement/Funding

Health Research Council of New Zealand; Heart Foundation of New Zealand

P2616Soluble urokinase plasminogen activator receptor (suPAR) predicts 1 year mortality in patients with acute breathlessness

Aim

Soluble urokinase plasminogen activator receptor (suPAR) is a pleotropic receptor, capable of orchestrating plaque vulnerability and vascular immune dysfunction. Its concentration in circulation may reflect on CVD associated burden. We examined the prognostic ability of suPAR to predict death in patients suspicious of ADHF.

Methods

suPAR measurements were undertaken with a CE-marked ELISA (ViroGates) in 444 patients presenting to hospital with the primary complaint of breathlessness to our hospital ED. A second sample at 12–48 hours post ED admission was available for 378 patients. Standard biochemistry analytes; MR-proADM (BRAHMS), NTproBNP and hsTnT (both Roche) were also measured. Statistical assessment was made using SPSS v25 (IBM), with all biomarkers treated as continuous variables and presented as median [interquartile range (IQR)]. Group comparisons were made by Mann-Whitney U test. The singular or combined clinical performances of suPAR, NT-proBNP, hsTnT and MR-proADM were assessed using receiver operator curve (ROC) area under the curve (AUC) (Z-scores) and Cox hazard regression (log-values) analyses. P-value <0.05 was considered significant.

Results

In the breathless cohort [median age 72 yrs (IQR: 62–81, 43% female)], 35.1% had ADHF and 94/444 patients died within the 1st yr of ED presentation. In those who died within this 1st yr, median suPAR concentrations at both time-points; 5.2 ng/mL (IQR: 2.8–5.5) vs. 5.1 ng/mL (IQR: 1.7–2.3) were higher than those who did not die (3.5 ng/mL; IQR: 2.7–5.1) (P<0.0001). Plasma suPAR, for both time points, respectively, could predict death at 30d (n=22, ROC-AUC = 0.77 and 0.76), 90d (n=41, ROC-AUC = 0.77 and 0.75) and 1 yr (ROC-AUC = 0.73 and 0.72). Improvement in 90d mortality prediction was achieved with the inclusion of suPAR in models; for e.g. using ED values, for NTproBNP; ROC-AUC of 0.67 increased to 0.71, for hsTnT; ROC-AUC of 0.69 to 0.76, and for MR-proADM, ROC-AUC of 0.72 to 0.75. Both suPAR time-points (ROC-AUC 0.70) could predict 1 yr new heart failure (HF) (n=68) but did not assist in improving HF prediction when used in combination with NT-proBNP, hsTnT or MR-proADM. After adjustment for conventional risk factors, Cox hazard regression analyses however revealed suPAR as the only biomarker capable of predicting 1 yr mortality (P=0.005) with hazard ratios of 2.8 (CI: 1.4–5.9) and 3.5 (CI: 1.1–11.3) for the ED and inpatient time-points, respectively. In terms of best window for prognostic assessment, suPAR concentrations at ED, outperformed the inpatient concentrations as the superior time-point in predicting 1 yr mortality.

Conclusion

suPAR exhibits excellent prognostic ability in mortality prediction, proving better than NTproBNP, hsTnT and MR-proADM in acutely breathless patients. The usage of suPAR in complementary with current candidate cardiac biomarkers could dramatically improve the prognostic tools available to guide risk management in HF.

Acknowledgement/Funding

New Zealand Heart Foundation, Health Research Council of New Zealand

Regional vascular response to ProAngiotensin-12 (PA12) through the rat arterial system

ProAngiotensin-12 (PA12) is the most recent peptide to be identified as a functional component of the renin-angiotensin system (RAS). PA12 is reported to constrict rat coronary arteries and the aorta, dependent upon angiotensin II-converting enzyme 1 (ACE1) and chymase. The current study employed myography to determine the direct vascular effects of PA12 on a range of isolated rat arteries extending from the core to periphery. PA12 significantly constricted the descending thoracic aorta, right and left common carotid arteries, abdominal aorta and superior mesenteric artery, with little effect on the femoral and renal arteries. AngII was found to produce similar responses to PA12 when administered at the same dose. A potency gradient in response to PA12 was clearly apparent, with vessels in closest proximity to the heart responding with the greatest constriction; while constrictive potency was lost further form the heart. Inhibition of ACE1 and chymase both significantly attenuated PA12-induced vasoconstriction, with chymostatin displaying lesser potency. We postulate ACE1 primarily regulates RAS activity within the circulation, while chymase may have an important role in local, tissue-based RAS activity.

Urotensin II and urotensin II-related peptide (URP) in cardiac ischemia-reperfusion injury

Circulating urotensin II (UII) concentrations and the tissue expression of its cognate receptor (UT) are elevated in patients with cardiovascular disease (CVD). The functional significance of elevated plasma UII levels in CVD is unclear. Urotensin-related peptide (URP) is a paralog of UII in that it contains the six amino acid ring structures found in UII. Although both peptides are implicated as bioactive factors capable of modulating cardiovascular status, the role of both UII and URP in ischemic injury is unknown. Accordingly, we provide here the first report describing the direct cardiac effects of UII and URP in ischemia-reperfusion injury. Isolated perfused rat hearts were subjected to no-flow global ischemia for 45 min after 30min preconditioning with either 1nM rUII or 10nM URP. Both rUII- and URP-induced significant vasodilation of coronary arteries before (both P<0.05) and after ischemia (both P<0.05). Rat UII alone lowered contractility prior to ischemia (P=0.053). Specific assay of perfusate revealed rUII and URP both significantly inhibited reperfusion myocardial creatine kinase (CK) release (P=0.012 and 0.036, respectively) and atrial natriuretic peptide (ANP) secretion (P=0.025). Antagonism of the UT receptor with 1muM palosuran caused a significant increase in perfusion pressure (PP) prior to and post-ischemia. Furthermore, palosuran significantly inhibited reductions in both PP and myocardial damage marker release induced by both rUII and URP. In conclusion, our data suggests rUII and URP reduce cardiac ischemia-reperfusion injury by increasing flow through the coronary circulation, reducing contractility and therefore myocardial energy demand, and inhibiting reperfusion myocardial damage. Thus, UII and URP present as novel peptides with potential cardioprotective actions.

Cardiovascular effects of native and non-native urotensin II and urotensin II-related peptide on rat and salmon hearts

Urotensin II (UII) was first discovered in the urophyses of goby fish and later identified in mammals, while urotensin II-related peptide (URP) was recently isolated from rat brain. We studied the effects of UII on isolated heart preparations of Chinook salmon and Sprague-Dawley rats. Native rat UII caused potent and sustained, dose-dependent dilation of the coronary arteries in the rat, whereas non-native UII (human and trout UII) showed attenuated vasodilation. Rat URP dilated rat coronary arteries, with 10-fold less potency compared with rUII. In salmon, native trout UII caused sustained dilation of the coronary arteries, while rat UII and URP caused significant constriction. Nomega-nitro-(l)-arginine methyl (l-NAME) and indomethacin significantly attenuated the URP and rat UII-induced vasodilation in the rat heart. We conclude that UII is a coronary vasodilator, an action that is species form specific. We also provide the first evidence for cardiac actions of URP, possibly via mechanisms common with UII.

Deconvolution analysis of cardiac natriuretic peptides during acute volume overload

Cardiac natriuretic peptides, especially amino terminal pro-Brain Natriuretic Peptide (NT-proBNP), are emerging as powerful circulating markers of cardiac function. However, the in vivo secretion and elimination (t1/2) of these peptides during acute volume overload have not been studied. We present the first report of the secretion and elimination of cardiac natriuretic peptides, based on deconvolution analysis of endogenous ovine plasma levels measured by specific radioimmunoassay. Four normal, conscious sheep underwent rapid right ventricular pacing (225 bpm) for 1 hour to stimulate acute cardiac natriuretic peptide release. Plasma samples and right atrial pressure measurements were taken at regular intervals 30 minutes before, during, and 4 hours after pacing. Baseline right atrial pressure significantly increased (P:=0.02) during the 1 hour of pacing in association with a prompt increase in plasma BNP (P:=0.03), atrial natriuretic peptide (P:=0.01), and NT-proBNP (P:=0.02). Deconvolution analysis showed that the t1/2 of NT-proBNP (69.6+/-10.8 minutes) was 15-fold longer than BNP (4.8+/-1. 0 minutes). Despite sustained increases in atrial pressure, cardiac secretion of natriuretic peptides (particularly atrial natriuretic peptide) fell during the pacing period, suggesting a finite source of peptide for secretion. Size-exclusion high-performance liquid chromatography revealed NT-proBNP to be a single immunoreactive peak, whereas BNP comprised at least 2 immunoreactive forms. These findings, especially the prompt secretion of BNP and the prolonged t1/2 of NT-proBNP, clarify the metabolism of BNP forms and help to explain the diagnostic value of NT-proBNP measurement as a sensitive marker of ventricular function.

Neurohormones in an ovine model of compensated postinfarction left ventricular dysfunction

Clinical heart failure, often the result of myocardial infarction, may be preceded by a period of compensated left ventricular impairment. There is substantial need for an experimental model that reflects this human condition. In sheep, coronary artery ligation produced consistent left ventricular anteroapical myocardial infarctions resulting in chronic (5 wk), stable hemodynamic changes compared with sham controls, including reductions in ejection fraction (51 +/- 2 vs. 30 +/- 5%, P < 0.001), cardiac output (6.3 +/- 0.2 vs. 5.1 +/- 0.2 l/min, P < 0.01), and arterial pressure (93 +/- 2 vs. 79 +/- 3 mmHg, P < 0.001), and increases in cardiac preload (left atrial pressure, 3.3 +/- 0.1 vs. 8.3 +/- 1.3 mmHg, P < 0.001). These changes were associated with acute and sustained increases in plasma concentrations of atrial natriuretic peptide (ANP; 5 wk, 11 +/- 2 vs. 27 +/- 5 pmol/l, P < 0.001), brain natriuretic peptide (BNP; 3 +/- 0.2 vs. 11 +/- 2 pmol/l, P < 0.001), and amino-terminal pro-brain natriuretic peptide (NT-BNP; 17 +/- 3 vs. 42 +/- 12 pmol/l, P < 0.001). Significant correlations were observed between plasma levels of the natriuretic peptides (ANP, day 7 to week 5 samples; BNP and NT-BNP, day 1 to week 5 samples) and changes in left ventricular volumes and ejection fraction. In contrast, renin activity, aldosterone, catecholamines, and endothelin were not chronically elevated postinfarction and were not related to indexes of ventricular function. Coronary artery ligation in sheep produces the pathological, hemodynamic, and neurohormonal characteristics of compensated left ventricular impairment secondary to myocardial infarction. Plasma concentrations of the cardiac natriuretic peptides are sensitive markers of left ventricular dysfunction. This is a reproducible model that reflects the clinical condition and should prove suitable for investigating the pathophysiology of, and experimental therapies in, early left ventricular dysfunction.

Amino-terminal proBNP in ovine plasma: evidence for enhanced secretion in response to cardiac overload

We have recently identified a novel amino-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) in the circulation of humans, the concentration of which increases progressively as the left ventricle fails. To clarify the origins of NT-proBNP in experimental animals, we have developed an RIA for NT-proBNP based on residues 52-71 of ovine proBNP-(1-103) and used it to study cardiac processing, secretion, and metabolism of BNP in sheep with cardiac overload induced by coronary artery ligation (CAL) or rapid left ventricular pacing (rLVP). The concentration of NT-proBNP in left atrial plasma extracts drawn from normal control sheep was threefold that of mature BNP. Size-exclusion and reverse-phase HPLC analyses of plasma extracts coupled to RIA revealed a single peak of immunoreactive (ir) NT-proBNP [ approximately 8,000 relative molecular weight (Mr)], quite distinct from a single peak of ir-mature BNP ( approximately 3,000 Mr). In contrast, ovine cardiac tissue contained only a single immunoreactive peak of high-molecular-weight BNP ( approximately 11,000 Mr), consistent in size with proBNP-(1-103). Sampling from the cardiac coronary sinus in normal control sheep (n = 5) and sheep with CAL (n = 5) revealed that the molar ratio of NT-proBNP to mature BNP was similar. There was a significant gradient of both mature and NT-proBNP across the heart in normal sheep, whereas after CAL the gradient was significant for mature BNP only. In both forms of cardiac overload (CAL and rLVP), left atrial plasma levels of NT-proBNP were significantly increased above normal levels, in contrast with mature BNP levels, which were raised only in the rLVP group of animals. Blockade of natriuretic peptide metabolism in sheep with heart failure (induced by rLVP) raised mature BNP levels threefold but did not affect levels of NT-proBNP. In conclusion, these studies show that NT-proBNP is formed from proBNP stores during secretion and, compared with mature BNP, accumulates in plasma because metabolism of NT-proBNP appears to differ from that of mature BNP. Although its function, if any, remains unclear, plasma NT-proBNP may prove to be a sensitive marker of cardiac overload and/or decompensation.

Ovine brain natriuretic peptide in cardiac tissues and plasma: effects of cardiac hypertrophy and heart failure on tissue concentration and molecular forms

Whereas numerous studies have examined the cardiac tissue content and secretion of atrial natriuretic peptide (ANP), the response of brain natriuretic peptide (BNP) in states of experimental cardiac overload is less well documented. Our recent partial cloning of the ovine BNP gene has enabled us to study changes in cardiac tissue concentration, together with tissue and circulating molecular forms of ANP and BNP, in response to cardiac overload induced by rapid ventricular pacing (n = 7) and aortic coarctation (n = 6). In normal sheep, although highest levels of BNP were found in atrial tissue (15-fold those of the ventricle), the BNP/ANP concentration ratio in the ventricles was 10- to 20-fold higher than the ratio calculated for atrial tissue. Compared with normal sheep, significant depletion of both ANP and BNP concentrations within the left ventricle occurred after rapid ventricular pacing. Size exclusion and reverse phase HPLC analysis of atrial and ventricular tissue extracts from normal and overloaded sheep showed a single peak of high molecular weight BNP consistent with the proBNP hormone. In contrast, immunoreactive BNP extracted from plasma drawn from the coronary sinus was all low molecular weight material. Further analysis of plasma BNP using ion exchange HPLC disclosed at least 3 distinct immunoreactive peaks consistent with ovine BNP forms 26-29 amino acid residues in length. These findings show that BNP is stored as the prohormone in sheep cardiac tissues and that complete processing to mature forms occurs at the time of secretion. The capacity to process the prohormone at secretion is not impaired by chronic heart failure.

Natriuretic peptides in sheep with pressure overload left ventricular hypertrophy

To examine tissue and plasma atrial (ANP) and brain natriuretic peptide (BNP) responses to left ventricular hypertrophy (LVH) 7 sheep underwent suprarenal aortic banding (20 mmHg initial pressure differential). Median survival time was 15 days. Proximal mean aortic pressure (MAP) increased from 65.1 +/- 5.0 mmHg (baseline) to 111.6 +/- 7.5 mmHg (day 7, p < 0.0001). Distal systolic aortic pressure fell from 85.5 +/- 8.7 mmHg (baseline) to 55.6 +/- 6.4 mmHg (day 7, p = 0.0002). Maximal plasma ANP (26.9 +/- 3.6 vs 10.1 +/- 1.2 pmol/L, p = 0.005) and BNP (15.3 +/- 3.6 vs. 3.5 +/- 1.0 pmol/L, p = 0.006) were recorded at 15 +/- 4.0 days. Coarctation induced rapid increases in PRA and plasma aldosterone and a fall in urinary sodium. Post-mortem examination of hearts confirmed LVH. Compared with controls, tissue ANP concentration was reduced in left atrium (p = 0.04) and LV (p = 0.04). BNP concentration was reduced in left atrium (p = 0.02) but tended to be higher in LV. In conclusion, suprarenal aortic coarctation leads to progressive hypertension resulting in LVH, progressive increases in plasma ANP and BNP and, in most cases, death from heart failure.

Single medial injection peribulbar anaesthesia using prilocaine

A prospective randomised study is reported comparing a single peribulbar injection into the medial compartment of the orbit and the standard two injection peribulbar technique. One hundred and seven patients undergoing elective intra-ocular surgery were randomly allocated to receive either a single medial injection, or two injections, using prilocaine 3% with felypressin. Akinesia and pain during surgery were assessed following the injection(s). There was no significant difference in pain during surgery and globe akinesia between the two groups. The single medial peribulbar injection is as effective as two injections using prilocaine 3%.

Peribulbar and retrobulbar anesthesia with prilocaine: a comparison of two methods of local ocular anesthesia

Prilocaine (Citanest) has been shown to be a satisfactory alternative to lignocaine, with certain important advantages, including superior diffusion. The latter may be especially important in peribulbar anesthesia, where the level of diffusion is a critical factor in providing a timely, high-quality block. In a prospective randomized study, we compared the effectiveness of peribulbar vs retrobulbar administration of prilocaine. Eighty-seven patients undergoing elective intraocular surgery were randomized to receive either retrobulbar or peribulbar anesthesia with prilocaine 3% with felypressin and hyaluronidase. Pain of injection, akinesia, and anesthesia were evaluated at predetermined intervals after injection. Except for the fact that lid akinesia occurred earlier in the peribulbar group, there was no difference in the quality or rate of onset of overall akinesia in the two groups. Nor were there any differences in the pain associated with injection. Both groups had excellent operative anesthesia and akinesia.