Study of the Role of Plasma NT-proBNP in the Diagnosis of Heart Failure.

BACKGROUND

The diagnosis of heart failure (HF) remains essentially clinical-Based. However, the history, physical examination, and chest radiograph findings are often inadequate in the diagnosis because multiple other conditions that affect the cardiopulmonary system mimic the symptoms of HF. N-terminal pro-BNP (NT-proBNP) has long been used for diagnosing HF. N-terminal pro-BNP values vary with different patient parameters. There is a scarcity of Indian studies on this topic. Especially with the use of newer drugs like angiotensin receptor neprilysin inhibitor (ARNI), it is important to have data from our own population on the same.

AIMS AND OBJECTIVES

(i) To assess the role of NT-proBNP in the diagnosis of HF. (ii) Achieve diagnostic clarity in cases having cardiorespiratory symptoms and signs like acute onset dyspnea, pedal edema, and basal crepitations. (iii) To study the effect of various factors like age, body mass index (BMI), and creatinine on NT-proBNP. (iv) Establish a relation between NT-proBNP levels and left ventricular ejection fraction (LVEF), disease severity, and etiology of HF.

MATERIALS AND METHODS

An observational prospective study of 50 patients presenting with acute onset breathlessness was carried out, fulfilling inclusion and exclusion criteria over a period of 10 months. Detailed history and examination of the patients were obtained. Venous sample for the measurement of NT-proBNP was collected within 24 hours of onset of symptoms. Other relevant blood and radiographic investigations were obtained. The NT-proBNP "cut-offs" set forth by the American Heart Association (AHA)/American College of Cardiology (ACC) were used to "rule in" or "rule out" HF. Two-dimensional echocardiography (2D Echo) was used to confirm the diagnosis. The correlation between NT-proBNP and various parameters like age, BMI, creatinine, and LVEF was obtained. Sensitivity and specificity tests were applied as well.

RESULTS

Out of the 50 patients presenting with acute onset dyspnea, the most common cause was ischemic heart disease (IHD) (44%) followed by dilated cardiomyopathy (DCM) (32%), chronic obstructive pulmonary disease (COPD) (10%), anemia (4%), followed by other causes. The median NT-proBNP value was the highest for IHD patients (9485 pg/mL), followed by DCM (8969 pg/mL), followed by COPD (2846 pg/mL), and followed by anemia (850 pg/mL). There is a significant positive correlation between NT-proBNP and age (coefficient of correlation r = 0.4007, significance level p = 0.0389, and class interval = 0.137-0.61). There is a significant negative correlation between creatinine clearance and NT-proBNP (coefficient of correlation r = -0.372, significance level p = 0.007, and class interval = -0.58 to -0.105). There was significant negative correlation between LVEF and NT-proBNP (coefficient of correlation r = -0.36, significance level p = 0.009, and class interval = -0.58 to -0.09). Higher LVEF is associated with lower NT-proBNP values. There is marked heterogeneity in the values though.

CONCLUSION

It is seen that the values of NT-proBNP vary with factors like age, BMI, and creatinine clearance in addition to LVEF. This may lead to falsely positive or falsely negative diagnosis of HF. With the above observations in mind, it can be concluded that NT-proBNP can help diagnose HF but only in addition to clinical findings.