To Evaluate the Change in Brain Natriuretic Peptide Levels in Outpatients with Ischemic Cardiomyopathy and Its Association with Functional Capacity: A Pilot Study.

INTRODUCTION: Literature is sparse on the clinical correlation of six minute walk test (6MWT) and Brain Natriuretic Peptide (BNP) levels in ischemic Cardiomyopathy (Ischemic CMP) patients. New York Heart Association (NYHA) classification is most commonly used for functional assessment of Heart Failure (HF), which is very subjective. This limitation is overcome by 6MWT which has prognostic significance in addition to assessment of level of functional impairment. Serum BNP correlate with clinical severity of HF as assessed by NYHA class. AIM: To evaluate the change in BNP levels in outpatients with ischemic CMP and its association with functional capacity.
MATERIAL AND METHODS: Sixty seven patients of established ischemic CMP by coronary angiography With Left Ventricular Ejection Fraction (LVEF) <40%, were recruited on an Outpatients Department (OPD) basis and assessed for baseline BNP levels and functional capacity (NYHA class and 6MWT). These patients were managed on OPD basis and the treatment was optimised and all the aggravating factors like uncontrolled diabetes, hypertension and anaemia were corrected. Patients were also advised life style modifications and cessation of smoking and alcohol consumption. All these patients were followed up for six months with optimum medical treatment and repeat 6MWT and BNP levels. Primary end point was change in the functional class and the BNP levels at six months. Statistical analysis was done with paired t-test and Pearson correlation for BNP levels and 6MWT/NYHA class.
RESULTS: A total of 67 patients were enrolled, out of which 48 patients had six months follow up. Thirty two patients were in NYHA Class II and remaining was in NYHA Class III at the time of enrollment. At six months, 37 were in NYHA Class II and 11 in Class III. At enrollment, 37 cases were able to walk >300 m in six minutes and 11 cases walked < 300 m where as at six months 43 walked >300 m and five walked <300 m. As compared to baseline the mean distance covered in 6MWT showed significant improvement and with reduction in BNP levels at six months (p<0.001). Mean BNP levels correlated better with 6MWT (p <0.001) than NYHA class (p<0.67).
CONCLUSION: In patients with established ischemic CMP with LVEF <40%, there is a significant reduction in BNP levels and improvement in 6MWT at six months with optimum medical therapy. A 6MWT correlated better with BNP levels than with NYHA class with a significant p-value. However, larger such studies and a longer duration of follow up is desirable to prove this association.