Accuracy of natriuretic peptides levels in the diagnosis of left ventricular dysfunction Introduction to Medicine – 1st year Class th december 2006 Porto Medical Faculty Systematic Review

Introduction Left ventricular dysfunction; Type-B natriuretic peptides; Use of type-B natriuretic peptides on diagnosis of left ventricular dysfunction;

Left ventricular dysfunction or heart failure (HF) is the pathophysiologic state in which the heart is enable to pump blood at a rate commensurate with the requirements of the metabolizing tissues. [1] Complex clinical syndrome that can result from any structural or functional cardiac disorders that impairs the ability of the ventricle to fill with or eject blood. [2] Left ventricular dysfunction [1] - Braunwald. A textbook of Cardiovascular Medicine. Elsevier Saunders, 7th Edition [2] - Hunt S. ACC/AHA 2005 Guideline for the Diagnosis and Management of CHF in the adult. JACC 2005

4,9 million persons in USA are being treated for heart failure [3] 550,000 new cases diagnosed each year 10% of patients older than 75 years have heart failure Heart failure is the most common cause of hospitalization due to cardiovascular disease in patients over 65 years of age [4] The number of HF deaths has increased steadly despite advances in treatment, in part because of increasing numbers of patients with heart failure [5] [3] - Ho K. The epidemiology of heart failure: the Framingham Study. JACC 1993 [4] - Louis A. A systematic review of telemonitoring for the management of heart failure. Eur J Heart Failure 2003 [5] - American Heart Association. Heart disease and stroke statistics: 2005 update. Dallas; American Heart Association Left ventricular dysfunction

Is a major health care problem and one of the most frequent reasons for patients to be admitted to hospital; Despite significant advances in treatment, the prognosis remains poor. [6] A simple objective definition of CHF is currently impossible as there is no cutoff value of cardiac or ventricular dysfunction or change in flow, pressure, dimension, or volume that can be used reliably to identify patients with heart failure. [7] [6] – Sliwa, K. Heart Failure:Making a cardiac failure diagnosis as early as possible. The Medicine Journal, 2002 [7] - Denolin H. The definition of heart failure. Eur Heart J 1983.

Diagnosing Left Ventricular Dysfunction The clinical diagnosis of heart failure or left ventricular dysfunction is complex, especially in the presence of other pathologies such as respiratory disease or obesity [8, 9] There are three types of tests for the diagnosis of this pathology: –Echocardiography and Doppler flow studies;[10] –ECG and Chest X-rays; –Blood tests for heart failure. [11] [8] – Remes J. Validity of clinical diagnosis of heart failure in primary health care. Eur Heart J [9] – Stevenson LW. The limited reliability of physical signs for estimating hemodynamics in chronic heart failure. JAMA [10] – Nielsen OW. Retrospective analysis of the cost-effectiveness of using plasma brain natiuretica peptide in screening for LVD in the general population. JACC [11] – McCullough PA. B tpe natriuretic peptide and clinical judgment in emergency diagnosis of HF: analysis from Breathing Not Properly Multinational Study. Circulation 2002

Echocardiography and Doppler flow studies The single most useful diagnostic test evaluating patients with suspected heart failure is without doubt the 2-dimentional echocardiogram, coupled with Doppler flow studies [12] With the help of echocardiography the degree of left ventricular systolic dysfunction can be determined which has important prognostic implications; Doppler echocardiography assists in the diagnosis of diastolic dysfunction. [6] Its limited availability and high costs prohibit its use in general screening test [13] [12] – Sim V. The use of brain natriuretic peptide as a screening test for left ventricular systolic dysfunction – cost-effectivenedd in relation to open access echocardiography. Fam Pract [13] – Cheitlin MD. ACC/AHA/ASE 2003 Guideline update for clinical application of echocardiography. JACC 2003

ECG and Chest X-rays Both chest radiography and 12-lead electrocardiograms are important in providing baseline information in most patients, Are both insensitive and nonspecific, Neither the ECG nor the chest radiograph should form the primary bases for determining the specific cardiac abnormality responsible for the development of heart failure. [6] [6] – Sliwa K.Heart Failure: Making a cardiac failure diagnosis as early as possible, The Medicine Journal, March 2002

Blood tests for heart failure Recently the measurement of circulating levels of brain natriuretic peptide (NT- proBNP by Roche diagnostics) has become available as a means of identifying patients with elevated left ventricular filling pressures who are likely to have signs and symptoms of heart failure. [14] [14] - Peacock W. The B-type natriuretic peptide assay: A rapid test for heart failure, Cleveland Clinic Journal of Medicine 2002

Natriuretic Peptides There are three types of natriuretic peptides (NP): –Type-A: produced by atrials myocite cells; –Type-B: produced by ventricular myocites cells; –Type-C: predominantly secreted by noncardiac tissues (e.g., endothelium). [15] The most relevant type of NP for the diagnosis of left ventricular dysfunction is the type-B. [16] [15] – Vanderheyden M. Brain and other natriuretic peptides: molecular aspects. Eur J Heart Failure 2004 [16] – Pfister R. Use of NT-proBNP in routine testing and comparison to BNP. Eur J Heart Failure 2004

Type-B Natriuretic Peptides They are produced in the form of an inactive hormone, proBNP; This inactive hormone is enzimaticly cleaved to two peptides: one active, BNP; and another inactive, NT- proBNP; In this reaction, NT-proBNP is produced in the same proportion as BNP [17] This hormones are metabolized mostly in the kidneys; Although the proportion of this reaction is 1:1, the blood levels of NT-proBNP are higher, since BNP is also metabolized by endopeptidases and endotelial receptores.[18] [17] – Hulsmann M. Incidence of normal values of natriuretic peptides in patients with chronic heart failure and impact on survival: A direct comparison of N-terminal atrial natriuretic peptide, N-terminal brain natriuretic peptide and brain natriuretic peptide.. Eur J Heart Failure 2005 [18] – Wu A. Biological variation of natriuretic peptides and their role in monitoring patients with heart failure. Eur J Heart Failure 2004

Type-B Natriuretic Peptides The active form, BNP, induces the relaxation of the cardiac muscle in response to hemodinamic stress; The increase of the hemodinamic stress causes the rise of the plasmatic levels of the NP; This rise is commonly a sign of heart failure.[19] [19] – Larsen A. The effect of altering haemodynamics on the plasma concentrations of natriuretic peptides in heart failure. Eur J Heart Failure 2006

Natriuretic Peptides on the Diagnosis of Left Ventricular Dysfunction The assay that determines the levels of NP consists on a blood test of imunofluorescence that measures the plasmatic levels of BNP or NT-proBNP; The cut value for the concentration of BNP is 100 pg/mL and for the concentration of NT-proBNP is 175 pg/mL; above this levels, the patient is considered in risk of suffering of an heart failure; It is economically viable and it is easy to perform.[14, 20] [14] – Peacock W. The B-type natriuretic peptide assay: A rapid test for heart failure, Cleveland Clinic Journal of Medicine 2002 [20] – Mueller C. Use of B-type natriuretic peptide in the evaluation and management of acute dyspnea. NEJM 2004.

Natriuretic Peptides on the Diagnosis of Left Ventricular Dysfunction The test is, nowadays used to diagnose patients in risk of heart failure and to decide which patients need internment; It can also be used to stratify the patients, according to the severity of the pathology; In the future, clinicians may be able to adjust the therapy bearing in mind the levels of NP of the patients; This levels can also be used to predict the evolution (prognosis) of the patient. [21] [21] – Isakson S. Natriuretic peptides as prognosticators in congestive heart failure. BMJ 2006

Aim of the study To evaluate the sensibility and specify of natriuretic peptide levels in the diagnosis of systolic left ventricular dysfunction.

Methods Systematic review Bibliographic research in medical databases:  Cochrane’s  PubMed’s Query used to search PubMed: (("Ventricular Dysfunction, Left"[MeSH ] OR "Heart Failure, Congestive"[MeSH] OR "Cardiac failure" OR "ventricular dysfunction" OR "heart failure" OR "cardiac dysfunction" OR "heart dysfunction") AND ("Natriuretic Peptide, Brain"[MeSH] OR "natriuretic peptide" OR "probnp" OR "bnp" OR "ntprobnp") AND ("Sensitivity and Specificity"[MeSH] OR sensitivity OR specificity OR "ROC Curve"[MeSH] OR "ROC Curve" OR "likelihood ratio" OR accuracy OR “ Predivtive value of tests”[MeSH] OR "predictive value")) NOT review

Query used to search Cochrane: (("Ventricular Dysfunction, Left" OR "Heart Failure, Congestive" OR "Cardiac failure" OR "ventricular dysfunction" OR "heart failure" OR "cardiac dysfunction" OR "heart dysfunction") AND ("Natriuretic Peptide, Brain” OR "natriuretic peptide" OR "probnp" OR "bnp" OR "ntprobnp") AND ("Sensitivity and Specificity" OR sensitivity OR specificity OR "ROC Curve" OR "ROC Curve" OR "likelihood ratio" OR accuracy OR "Predictive Value of Tests")) Methods

Definition of exclusion criteria (tracing): this task was performed by one group made of three reviewers. Definition of inclusion criteria (tracing): this task was performed by one group made of four reviewers. The selection of the articles will be made under the overall approval.

Criterias Inclusion Publications on the accuracy or sensitivity and specificity of BNP levels in the diagnosis of heart failure or left ventricular dysfunction. Compare the diagnostic accuracy of NTproBNP or BNP to the traditional means of diagnosing the heart failure, such as echocardiography, or clinical criterias. Be written in English, Portuguese, French or Spanish.

Criterias Exclusion To be a randomized clinical trial. To be limited to very restrictive study groups such as patients with Duchenne disease, Chagas disease or Brugada syndrome. To be performed in non human population To associate the cardiac failure to congenital or hereditary diseases.

Data Extraction Data on study identification, year of publication, diagnostic cross table, spectrum of patients and methodological aspects are to be extracted from original studies; The study population data is going to incorporate the inclusion/exclusion criteria, type of assay (extractive, immunofluorescence) and the reference standard evaluated (cardiac failure vs left ventricular systolic dysfunction) The methodological quality of the individual studies is going to be appraised using QUADAS tool [22] [22] – Whiting P. The development of QUADAS: a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews. BMC Med Res Methodol 2003

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