NT Pro-BNP is a marker of ?
A. LV failure
B. LV dysfunction
C. Elevated in both
D. It can be normal in both
Answer: You should have guessed it right. If not, read the following, might help you out.
The first and foremost point is to understand the difference between LV dysfunction and failure. LV failure is a clinical diagnosis. LV dysfunction is an echocardiographic diagnosis.BNP can increase due to any mechanical stretch of LV and may rise even with Atrial stretch . Every patient with baseline LV dysfunction will show mild elevation. Sudden spikes can come with clinical worsening. However, to our surprise the NT pro BNP levels is not found to be correlating with severity dyspnea or orthopnea .
Most importantly NT Pro BNP can elevate in isolated subclinical diastolic dysfunction. This makes interpreting its level more complex.
*Additionally, BNP levels can be falsely elevated in renal failure and may be spuriously normal in obese individuals with left ventricular dysfunction. These disparities are due to variations in contributions from preformed (Granular cell depots) and freshly synthesised NT Pro BNP. The later process is severely impaired in obesity.
The following chart illustrates conditions that can cause elevated NT Pro-BNP levels beyond heart failure.
The answer to the question : Every response A to D is correct.
Final message
Relying too much on biochemistry, such as NT pro BNP to diagnose heart failure clouds our clinical judgment.Please realise ,NT pro BNP is not a creatinine equivalent for renal failure .Diagnosis of cardiac failure should focus on clinical criteria and symptoms, with NT pro BNP serving more as a prognostic rather than a diagnostic tool.(The good old Framingham criteria still stand strong & relevant )
Dr.S.Venkatesan MD 