B-type natriuretic peptide may help guide mitral valve surgery decisions
medwireNews: B-type natriuretic peptide (BNP) is a “powerful predictor” of survival in patients with degenerative mitral valve regurgitation (DMR) receiving medical treatment, researchers report.
They found that elevated BNP activation, expressed as a ratio to the upper limit of normal for patient age and gender and assay type (BNP ratio), was independently associated with worse survival.
And, importantly, there was evidence of a quantitative link, with higher BNP ratios signalling a greater degree of excess mortality, making them a potentially useful prompt for surgical referral, stress Maurice Enriquez-Sarano (Mayo Clinic, Rochester, Minnesota, USA) and team in the Journal of the American College of Cardiology.
“BNP is not yet included in guidelines, but is essential to consider in the management of patients with DMR”, conclude Enriquez-Sarano et al.
Helmut Baumgartner (University hospital Muenster, Germany) agrees in a related editorial that BNP is likely to improve the timing of surgery, but believes that the findings are not conclusive on whether BNP activation is “an indication for surgery by itself even if the other currently accepted triggers for intervention are not present”.
Following mitral valve surgery, BNP ratios no longer independently predicted survival, which the researchers suggest indicates “successful interruption of deleterious myocardial damage after surgical correction of DMR.”
Among 1331 patients with moderate-to-severe DMR (mean ejection fraction 64%; mean regurgitant volume 67 mL) aged a mean of 64 years, the median BNP and BNP ratios were 91 pg/mL and 1.01, respectively, with values ranging from the 25th to 75th percentiles.
Half of the patients had BNP clinical activation at diagnosis and 229 died over a mean follow-up of 5.1 years. A raised BNP ratio at diagnosis was associated with a significant 33% increased likelihood of death, whereas there was no association with absolute BNP levels.
Among the 770 managed conservatively, an elevated BNP ratio significantly increased the risk of death by 61%, and when patients were split into categories for BNP activation (BNP ratio ≤4, >4), each degree of activation was associated with incremental excess mortality versus normal BNP levels (BNP ratio ≤1).
Indeed, the risk of death was increased 2.28-fold for patients with a moderately elevated BNP ratio (≤4), compared with normal levels, and 3.71-fold for those with severely (>4) elevated levels, with a 1.62-fold difference between groups with severe and moderate elevations.
The effect of BNP activation on mortality was particularly evident in patients with severe DMR, but was consistent across all subgroups. And a significant link to worse survival was even seen in the 287 asymptomatic patients, demonstrating an effect independent of classical markers such as atrial fibrillation, heart failure, pulmonary hypertension, left ventricular ejection fraction and left ventricular end systolic diameter.
In terms of the role the BNP ratios may play in optimising the timing of surgery, editorialist Baumgartner believes the strongest finding is that for asymptomatic patients, “a normal BNP is reassuring that further conservative follow-up is safe and surgery is not indicated.”
The survival rates for such patients in the current study were 90% at 8 years versus 53% for patients with a BNP ratio above 1.
“Determining when elevated BNP should prompt intervention in the absence of any other currently accepted surgical triggers requires further research”, he concludes, adding that “[i]n any case, elevated neurohormones should cause further comprehensive patient elevation and reconsideration of treatment decisions.”
By Lucy Piper
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