Natriuretic Peptide measurements in managing heart failure: in theory and in practice.

Many studies have described the role of B-type natriuretic peptide or its amino-terminal byproduct (NT-pro-B-type natriuretic peptide) in clinical practice, including several published or ongoing randomized clinical trials. However, the debate over natriuretic peptide testing continues, mostly related to the appropriateness of testing as decision support for the management of heart failure. The most accepted use is to improve recognition of heart failure when the diagnosis has been overlooked or questioned after consideration of clinical signs and symptoms.1,2 This is the basis of the class IIa recommendation for natriuretic peptide measurement in the urgent care setting when diagnosis is uncertain.3 It has been further suggested that serial natriuretic peptide measurement in the setting of known heart failure can help guide therapy, whereas critics have argued that evidence-based drug therapy for heart failure should be implemented and titrated similarly regardless of natriuretic peptide levels. Knowing the precise natriuretic peptide level on a routine basis has yet to be consistently proven to improve the delivery of care or to change outcomes for the better. This has led to a class IIb recommendation for serial B-type natriuretic peptide measurement in the latest guideline updates.3 Within the setting of this ambiguity, I will describe my own opinions (and biases) for measuring natriuretic peptide levels (Table 1). First, the absence of information about a specific natriuretic peptide level on a patient does not necessarily interfere with my ability to diagnose heart failure clinically or to assess its severity. The knowledge of a particular natriuretic peptide level does not provide specific indications or contraindications to treatment recommended by the evidence-based clinical guidelines. Therefore, I personally do not routinely measure natriuretic peptide levels on all patients at all clinic visits, nor do I measure natriuretic peptide levels routinely at the time of admission for heart failure. However, I do believe that natriuretic peptide levels can provide an additional objective measure of cardiac insufficiency in the form of a reproducible, widely available, and relatively inexpensive blood test. Assessment of natriuretic peptide levels can be helpful in selected patients at the bedside regarding disposition and treatment plans (especially when patients have been admitted for decompensated heart failure), such as the determination of how closely I need to monitor an individual’s clinical status, when to conduct additional testing, or when to schedule a follow-up appointment after a hospital discharge. In particular, when encountering an unexplained rise in natriuretic peptide levels in a patient without new complaints, I often put more effort toward further investigations into potential contributing factors. In contrast, for a clinically euvolemic patient with persistently high but stable natriuretic peptide levels, I will confirm that all evidence-based drug therapies are being given (potentially attempt to be more aggressive in my neurohormonal and vasodilator therapy prescription) but will be judicious in up-titrating loop diuretics unless there is other evidence suggesting that my volume assessment may be inaccurate. In other words, I use natriuretic peptide levels in the clinical context to refocus the components of evidence for my decisions rather than to drive them. The clinical utility of natriuretic peptide testing may depend on both the patient’s clinical context and the clinician’s comfort level and experience with interpreting the natriuretic peptide levels. In a busy emergency department where multitasking and triage decisions are common, the availability of natriuretic peptide levels may facilitate more prompt decisions to treatment or disposition plans. However, routine testing has yet to confirm incremental benefit even in the urgent care setting.4 In contrast, a seasoned clinician encountering a familiar and well-treated patient with stable clinical status during a routine outpatient clinic visit may find a natriuretic peptide value not particularly additive to the overall assessment and treatment plan. That being said, we also lack data to establish the optimal testing interval and clinical utility for common monitoring tests, such as echocardiography. I do not routinely order follow-up natriuretic levels during heart failure hospitalizations, particularly when patients are responsive to their treatment plans. However, I nonetheless admit that seeing improvements in natriuretic peptide levels can be reassuring, and therefore some clinicians find such information “helpful.” In such cases, the decision to order a follow-up natriuretic peptide level may be based on the level of clinical suspicion or reassurance needed by the clinician. In cases where self-reported symptoms may not be as reliable, following natriuretic peptide levels can be informative. On the other hand, a patient who describes worsening heart failure symptoms with ambiguous clinical signs and exhibits a low natriuretic peptide level may prompt the search for potential underlying noncardiac causes. In my opinion, further routine testing may not be as helpful unless there are changes in the clinical context.