Natriuretic peptide levels must be interpreted in the light of clinical probability of heart failure
Given the recognition that "choosing appropriate thresholds[for serum natriuretic peptide] is problematic"(1), the best diagnostic strategy for obtaining maximum diagnostic "mileage" from natriuretic peptide levels might be that of interpreting any given result in the light of whether the patient has high, medium, or low clinical probability of heart failure. For that to come about, instead of reinforcing the idea that "Individual symptoms...and signs...are generally weak predictors of heart failure"(2), we should embrace the use of a scoring system such as the one recently compiled in the Netherlands which recognises the diagnostic value of physical examination by allocating points to individual clinical stigmata(3). We must also recognise that, as is the case with biomarkers(such as natriuretic peptides), even echocardiography is hedged in by caveats, not only in systolic heart failure(4), but also in diastolic heart failure(5). In the former context the redeeming feature is that, notwithstanding the fact that a subnormal left ventricular ejection fraction(LVEF) does not equate with clinically overt heart failure(6), in its own right, however, a subnormal LVEF does justify the use of modulators of the renin-angiotensin-aldosterone system(RAAS) such as angiotensin converting enzyme inhibitors(ACE-inhibitors) even if only to exert a favourable influence on the natural history of both subclinical and clinically overt heart failure(6). This means that, even if clinical symptoms and signs are not those of heart failure, ACE_inhibitors would still be justified in the event of a subnormal LVEF. A similar parallel does not exist for left ventricular diastolic dysfunction(when it does not co-exist with left ventricular systolic dysfunction) because there is no evidence base for justifying modulation of the RAAS through the use either of ACE inhibitors or spironolactone(or both) regardless of whether or not left ventricular diastolic dysfunction co-exists with symptoms attributable to heart failure. Accordingly, for patients with intact LVEF in whom echocardiographically validated left ventricular diastolic dysfunction coexists with "problematic" natriuretic peptide blood levels the central issue is whether or not associated clinical signs and symptoms signify clinical congestion and, hence heart failure, whether it be acute or chronic. Evidence-based parameters which have been utilised as criteria for clinical congestion include symptoms such as effort dyspnoea and orthopnoea, signs such as peripheral oedema, resting hugular venous distension, and the presence of a third heart sound, and radiographic stigmata such as cardiomegaly, pulmonary vascular redistribution, interstitial oeadema, and pleural effusion. All these have been evaluated for positive predictive value as well as for negative predictive value(7). We now need to optimise the accuracy of non-echocardiographic stigmata(3)(7) so as to respond constructively to the criticism levelled by a distinguished American physician at the "downplaying" of clinical evelaution in the NICE guidelines, when he said "Clinical evaluation is central to all complex clinical syndromes"(8), References (1)Al-Muhammad A., Mant J Republished technology and guidelines: The diagnosis and management of chronic heart failure: review following the publication of the NICE guidelines Postgrad Med J 2011;87:841-6 (2) Hobbs FDR., Doust J., Mant J., Cowie MR Diagnosis of heart failure in primary care Heart 2010;96:1773-7 (3) Kelder JC., Cramer MJ., van Wijngaarden J et al The diagnostic value of physical examination and additional testing in primary care patients with suspected heart failure Circulation 2011;124:2865-73 (4) Jolobe OMP Usefulness of left ventricular ejection fraction in patients with overt heart failure(letter) Mayo Clinic Proceedings 2006;81:1636-9 (5)Paulus WJ., Tschope C., Sanderson JE et al How to diagnose diastolic heart failure: a consensus statement on the diagnosis of heart failure with normal left ventricular ejection fraction by the Haert Failure and Echocardiography Association of the European Society of Cardiology Eur Heart J 2007;28:1539-50 (6)The SOLVD Investigators Effect of enalapril on mortality and the development of heart failure in asymptomatic patients with reduced left ventricular ejection fractions N Engl J Med 1992;327:685-91 (7)Gheorghiade M., Follath F., Ponikowski P et al Assessing and grading congestion in acute heart failure: A scientific statement from the Acute Heart Failure Committee of the Heart Failure Association of the European Society of Cardiology and endorsed by the European Society of Intensive Care Medicine European Journal of Heart Failuer 2010;12;423-33 (8) Finucane TE NICE Guideline for Management of Chronic Heart Failure in Adults(letter) Annals of Inernal Medicine 2012;156:69
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