Biological variation for N-terminal pro- and B-type natriuretic peptides and implications for therapeutic monitoring of patients with congestive heart failure.

Given the limitations of low enrollments, this study suggests that a change of 130% for B-type natiuretic peptide (BNP) and 90% for N-terminal (NT)-proBNP are necessary before results of serially collected data can be considered statistically different. This study also shows that there are important differences in the performance of BNP versus NT-proBNP in monitoring patients with congestive heart failure that need to be further explored.

Prognostic value of the Ortho Vitros cardiac troponin I assay in patients with symptoms of myocardial ischemia. Risk stratification using European Society of Cardiology/American College of Cardiology recommended cutoff values.

We evaluated the risk assessment value of a commercial cardiac troponin (cTn; Ortho Vitros ECi, Ortho-Clinical Diagnostics, Raritan, NJ) I assay in patients with symptoms of myocardial ischemia suggestive of acute coronary syndrome and compared findings with those for a commercial cTnT assay in the same population. The cTn levels were measured by both assays in plasma samples from 273 patients during 24 hours after admission. Baseline and maximum concentrations were used for risk stratification; cutoffs were the 99th percentile and 10% coefficient of variation. End points were all-cause death and cardiac events within 60 days. Relative risks (RRs) were estimated using Cox proportional hazards regression models and Kaplan-Meier curves. RRs of cardiac events and death were significantly higher with increased baseline and maximum concentrations using either cTnI cutoff. The respective mortality rates for baseline cTnI of more than 0.08 microgram/L vs 0.08 microgram/L or less were 17.4% vs 2.9% (P = .001); cardiac event rates were 11.5% vs 3.6% (P = .03). Exclusion of patients with ST-segment elevation had no significant effect on rates for either assay. Mortality was higher in the intermediate (0.09-0.2 microgram/L) than in the low (< or = 0.08 microgram/L) group for cTnI, with directionally similar results for cTnT. Our findings validate the Ortho cTnI assay as a risk stratification biomarker in patients with symptoms of myocardial ischemia.

Correlation of B-type natriuretic peptide level to 6-min walk test performance in patients with left ventricular systolic dysfunction.

BACKGROUND: B-type natriuretic peptide (BNP) is a neurohormone that can be measured in blood and is useful in patients with congestive heart failure (CHF). We compared whole blood BNP concentrations to distance walked during a 6-min walk test in patients with CHF. METHODS: Forty-four patients with CHF underwent a 6-min walk test. The distance walked was compared to the BNP concentration on blood collected prior to the walk test. Patients were followed for 16 +/- 2.8 months after testing. RESULTS: A significant correlation was observed between the BNP concentration and the distance walked (r = -0.47, p < 0.001). One patient without congestion died suddenly. Two patients died of progressive heart failure, and two other patients underwent cardiac transplantation. Each of the latter four patients had high BNP concentrations (median 1080 ng/l) and walked short distances (median 183 m). This study indicates that the BNP concentration in blood correlates inversely with the degree of physical capability of patients with heart failure. CONCLUSIONS: The BNP concentration could be used as an alternative to the 6-min walk test to assess the severity of heart failure. The assay for BNP is non-invasive, inexpensive, and results are available at the bedside or in a heart failure clinic.

A 24-hour comparison of serum growth hormone concentrations in patients with heart failure versus healthy controls.

STUDY OBJECTIVE: To compare endogenous serum growth hormone concentrations over a 24-hour period in patients with chronic heart failure (CHF) and matched controls. DESIGN: Prospective, 24-hour, endogenous concentration comparison. SETTING: Hospital research center. PATIENTS: Eight evaluable patients with nonischemic dilated cardiomyopathy and 10 healthy control subjects, matched for age and sex. INTERVENTION: Over a 24-hour period, blood was drawn from the study participants every 20 minutes for determination of growth hormone. MEASUREMENTS AND MAIN RESULTS: For each patient, the area under the concentration-time curve from time 0-24 hours (AUC0-24), maximum concentration (Cmax), and minimum concentration (Cnadir) of growth hormone were determined. The AUC0-24 and Cmax were 74% (p < 0.05) and 62% (p < 0.05) lower in patients with CHF than in controls, respectively. The Cnadir for all participants was 0 microg/L. Variability in growth hormone concentrations over the 24 hours was considerable for all study participants. CONCLUSIONS: Growth hormone concentrations are suppressed over a 24-hour period in patients with CHF versus healthy controls. Variability in levels throughout the day suggests that a single point evaluation cannot be used to determine deficiency or abundance of growth hormone.

A rapid B-type natriuretic peptide assay accurately diagnoses left ventricular dysfunction and heart failure: a multicenter evaluation.

BACKGROUND: B-Type natriuretic peptide (BNP), a protein released from the left ventricle in response to volume expansion and pressure overload, has emerged as the first whole blood marker for the identification of individuals with congestive heart failure (CHF). OBJECTIVE: The purpose of this study was to assess the performance of a point-of-care assay to diagnose and evaluate the severity of CHF on the basis of the New York Heart Association (NYHA) classification system. METHODS: Through a prospective, multicenter trial, whole blood samples were collected from a total of 1050 inpatients, outpatients, and healthy control patients. Participants were divided into subgroups for BNP analysis: patients without cardiovascular CHF (n = 473), patients with hypertension and no cardiovascular disease (n = 168), NYHA class I CHF (n = 73), class II CHF (n = 135), class III CHF (n = 141), and class IV CHF (n = 60). RESULTS: Circulating BNP concentrations determined from the bedside assay increased with CHF severity, as determined by the NYHA classification system, but were only statistically significant (P <.001) between individuals with and without CHF. Individuals without CHF had a median BNP concentration of 9.29 pg/mL. Median BNP values, with their corresponding interquartile ranges, for NYHA classification I through IV were 83.1 pg/mL (49.4-137 pg/mL), 235 pg/mL (137-391 pg/mL), 459 pg/mL (200-871 pg/mL), and 1119 pg/mL (728->1300 pg/mL), respectively. With the use of a decision threshold of 100 pg/mL, the assay demonstrated 82% sensitivity and 99% specificity for distinguishing control patients and patients with CHF. CONCLUSIONS: BNP concentrations obtained from whole blood samples are useful in the diagnosis of CHF and staging the severity of the disease.