Association of levels of N-terminal-pro-BNP-type natriuretic peptide with localisation of thrombus in acute pulmonary embolism.

To The Editor: I read the article published in your journal with great interest.1 However, I would like to offer some comments and seek some clarifications on this study. First, whether the study was prospective or retrospective in nature and what was the study duration. Secondly, N-terminal-pro-brain natriuretic peptide (NT-pro-BNP) assay was done before or after confirmation of thrombi by helical computed tomography (CT) scan. Moreover, the cut-off used for NT-pro-BNP in this study2 is actually validated for congestive heart failure and the same may not be applicable for pulmonary embolism. Most other studies have used a higher cut-off ranging from 500 to 1000 pg/mL.3 Thirdly, it is well established that cardiac biomarkers like BNP and NT-pro-BNP are indirect surrogate for right ventricular dysfunction (RVD) and central embolus is a strongest predictor of RVD both by echocardiography and radiologic evaluation.3-5 The degree of right ventricular dysfunction is directly proportional to the amount of pulmonary vascular bed that is compromised by an embolus. More central the obstruction is more the pulmonary vascular resistance and stress on the right heart. In this study NT-pro-BNP was significantly high in patients who had central emboli (9/49) or features of RVD like pulmonary hypertension, interventricular septal hypokinesia and chamber dilatation. The authors have not mentioned what was the total number of patients having RVD and amongst them how many had central or peripheral emboli. It will be ideal to know this data to interpret whether elevated NT-pro-BNP is a better predictor for RVD than the central embolus. Fourthly, NT-pro-BNP is a non-specific biomarker and can be elevated in left ventricular dysfunction, chronic lung diseases and chronic renal failure and pulmonary embolism can be a cause for the acute exacerbation of these conditions. It may not always be possible to differentiate patients with pulmonary embolism alone from those with pulmonary embolism and co-existing diseases that can lead to elevated serum NT-pro-BNP level, especially in emergency department before initiation of treatment. I would like to know how many patients were excluded from this study due to co-existing illness that can elevate NT-pro-BNP level and at what stage of presentation, i.e. in the emergency department, within 24 hour or later in their hospital stay. Even if I exclude these conditions, an elevated NT-pro-BNP level alone may suggest but cannot diagnose pulmonary embolism, and hence, do not avoid the need for a CT angiography which Association of Levels of N-Terminal-Pro-BNP-Type Natriuretic Peptide with Localisation of Thrombus in Acute Pulmonary Embolism