From the Guidelines
In obese patients with heart failure, B-type natriuretic peptide (BNP) levels are often lower than expected, with a reported decrease of approximately 20-30% per 10-unit increase in body mass index (BMI) 1.
Key Points
- As a result, a higher BNP threshold of 100-150 pg/mL may be considered for diagnosing heart failure in obese patients 1.
- Obesity is associated with lower BNP levels, which can make diagnosis of heart failure more challenging 1.
- The use of nesiritide, a recombinant human BNP analogue, may be effective in reducing symptoms and improving hemodynamics in these patients, regardless of their BNP levels, although the optimal dose and duration of treatment are not well established 1.
- BNP levels should be interpreted with caution in obese patients, taking into account the potential for lower levels due to obesity-related factors 1.
- A comprehensive diagnostic approach, including clinical evaluation, echocardiography, and measurement of serum natriuretic peptide levels, is recommended for diagnosing heart failure in obese patients 1.
From the Research
B-type Natriuretic Peptide (BNP) Levels in Obese Patients with Heart Failure
- BNP levels are lower in obese patients with heart failure compared to non-obese patients, as shown in studies 2, 3, 4, 5.
- The inverse relationship between BNP levels and body mass index (BMI) has been consistently observed, with lower BNP levels found in patients with higher BMI values 2, 3, 4.
- Studies have suggested that alternative cut-points for BNP should be used in obese patients to improve diagnosis, such as a lower cut-point of 54 pg/mL for severely obese patients 2 and proportionally lowering the currently recommended cut-offs by BMI 6.
- The use of N-terminal pro-B-type natriuretic peptide (NT-proBNP) has also been investigated, with findings indicating that adjusting NT-proBNP concentrations for obesity can increase its clinical utility in the early diagnosis of acute heart failure 6.
- Lower BNP levels have been observed in obese patients with acute heart failure with preserved ejection fraction, highlighting the need to lower the threshold of BNP levels in these patients 5.
Factors Influencing BNP Levels in Obese Patients
- BMI is an independent negative correlate of BNP level, with higher BMI values associated with lower BNP levels 4.
- Age, sex, and New York Heart Association (NYHA) functional class may also influence BNP levels in obese patients, although the relationships between these factors and BNP levels are not fully understood 5.
- Cytokine levels, such as tumor necrosis factor-alpha, interleukin-6, and soluble intercellular adhesion molecule-1, have been investigated in relation to BNP levels in obese patients, but no significant differences have been found 4.
Clinical Implications
- The diagnosis of heart failure in obese patients may be challenging due to lower BNP levels, and alternative diagnostic approaches may be necessary 2, 3, 6, 5.
- Adjusting BNP or NT-proBNP cut-points for obesity may improve the accuracy of heart failure diagnosis in these patients 2, 6.
- Further research is needed to fully understand the relationships between BNP levels, obesity, and heart failure, and to develop effective diagnostic and therapeutic strategies for obese patients with heart failure 2, 3, 6, 4, 5.