Cor Vasa 2006, 48(2):48-54 | DOI: 10.33678/cor.2006.021

Can severe essential hypertension raise BNP levels resulting in a misdiagnosis of heart failure?

Peter Jakubík^1,*, Tomáš Janota¹, Dan Wichterle², Jiří Widimský ml.¹, Hana Benáková³, Tomáš Zelinka¹, Jaromír Hradec¹, Tomáš Zima³

¹ II. interní klinika

² II. interní klinika

³ Oddělení klinické biochemie a laboratorní diagnostiky, Všeobecná fakultní nemocnice a 1. lékařská fakulta Univerzity Karlovy, Praha, Česká republika

In heart failure, ventricular cardiomyocytes respond to increased wall tension by increased brain natriuretic peptide (BNP) production. Consequently, measurement of plasma BNP levels has been identified by the European Society of Cardiology guidelines as a major tool used to diagnose heart failure. However, cardiomyocyte overload may also result from a simple rise in blood pressure (BP). The problem is that the currently available data on increased BNP production by a heart coping with high BP are not fully consistent.


Aim of study:
To study the effect of high BP on plasma BNP levels, to establish a correlation between BNP levels and degree of left ventricular hypertrophy (LVH), and to assess the risk for misdiagnosing heart failure based on a potential rise in BNP in individuals with severe essential hypertension.

Methods:
The group of hypertensive patients presenting to our center was used to select 35 individuals with severe and moderate essential hypertension without LVH (non-LVH), 35 individuals with LVH, and a control group of 35 healthy age-and sex-matched individuals. A thorough examination of individuals with their antihypertensive medication withdrawn ruled out a secondary etiology of hypertension and other serious conditions. Enrolled into the study were only patients with normal echocardiographic left ventricular systolic function. Blood pressure was determined while collecting blood for BNP determination; hypertensive patients also had ambulatory blood pressure monitoring (ABPM). BNP levels were determined by immunofluorescence (Centaur Bayer, Leverkusen, Germany).

Results:
The blood pressure of hypertensive patients was significantly higher (183 ± 22/108 ± 13 mm Hg) compared with that of the control group (121 ± 15/75 ± 11 mm Hg; p < 0.001). The measured BNP levels showed a considerable spread in hypertensives (0.2-277 ng/l); however, they were higher both in the LVH group (median and quartile range 29.8 [19.7-51.2] ng/l) and in the non-LVH group (24.6 [7.1-43.1] ng/l) compared with controls (12.5 [5.0-25.7] ng/l). The difference against controls was significant with the LVH group (p = 0.006) and with all hypertensives combined (p = 0.015). Among hypertensives, BNP levels correlated with their casual BP as well as 24-hour means of BP (sBP: r = 0.28, p = 0.004; dBP: r = 0.36, p = 0.0002; mean BP: r = 0.36, p = 0.002, 24H-sBP: r = 0.29, p = 0.016, 24H-dBP: r = 0.30, p = 0.011). BNP levels also correlated with left ventricular mass index (LVMI) (r = 0.238, p = 0.027), interventricular septum thickness (IVSd) (r = 0.26, p = 0.014) and left ventricular ejection fraction (EF) (r = -0.22, p = 0.030). Eight patients (11%) with severe hypertension (seven in the LVH group and one in the non-LVH group) showed BNP levels over the cutoff limit for the diagnosis of heart failure (100 ng/l). Multivariant regression analysis, while identifying sBP, dBP, IVSd, and EF as significant BNP determinants, showed the above parameters contributed to BNP variability by mere 6%, 10%, 4%, and 3%, respectively.

Conclusion:
While results of the study have confirmed an effect of high BP on plasma BNP levels, BNP values of hypertensive individuals were only slightly higher compared with those of controls. The rise in BNP was more appreciable in hypertensives with LVH. Though significant, the correlations between BNP and BP were fairly loose. The contribution of BP to BNP variability was small. Still, in individual cases (and in LVH patients in particular), high BP may result in a rise in BNP to values considered diagnostic for heart failure.

Keywords: BNP; Essential hypertension; Left ventricular hypertrophy; Heart failure

Published: February 1, 2006  Show citation