Plasma B-type natriuretic peptide level in patients with coronary artery bypass surgery

Abstract

Dear Editor, We read the article “Plasma B-type natriuretic peptide in predicting outcomes of elective coronary artery bypass surgery” by Chen et al with interest [1]. The authors investigated whether B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) are correlated with postoperative complications and outcomes after adjusting for risk factors. They concluded that studies using BNP and NT-proBNP levels for predicting intensive care unit stay and hospitalization in patients who have undergone coronary artery bypass graft must adjust risk factors to present a more appropriate estimation of its clinical outcome. BNP is a cardiac neurohormone secreted by the ventricles in response to end-diastolic pressure, related to volume load. Although most widely used as a marker of systolic or diastolic dysfunction, elevated BNP level has been reported in many conditions [2]. Therefore, it is important to determine diastolic and systolic functions by echocardiography. Performing echocardiography is also important for measurement of pulmonary artery pressure. Pulmonary arterial hypertension is commonly associated with rheumatic diseases and an elevated BNP level may be a result of the increase in pulmonary pressure [3]. Natriuretic peptides are secreted in response to a nonspecific pressure load of any cardiac chamber, which is not only seen in cases of heart failure, but also in cases of systemic hypertension, atrial fibrillation, valvular disease, and even in some noncardiovascular conditions such as renal failure. One of the prominent diseases with elevated BNP level is diseases of the respiratory system such as chronic obstructive pulmonary disease, pulmonary embolism, interstitial lung disease in which BNP level is elevated in response to pressure on the right side of the heart [4]. By contrast, high levels of BNP can be seen in many cases, resulting in increased cardiac output and cardiac stress such as sepsis and hyperthyroidism [3]. The BNP level has been shown to be increased in patients with liver cirrhosis as well [5]. Therefore, determining these conditions may reveal stronger results in studies evaluating the effects of changes in BNP level. One of the important prognostic factors prior to performing coronary artery bypass surgery is estimating BNP level. However, except for cardiac diseases, elevated BNP level may be seen in several diseases. In addition, one should keep in mind that BNP alone without other predictive markers may not give exact information to clinicians about prognostic indication of the patients. Therefore, we think that BNP level should be evaluated along with levels of other serum mortality predictive markers.