Bedside B-Type Natriuretic Peptide and Functional Capacity in Chronic Heart Failure

OBJECTIVES: To determine if B-type natriuretic peptide (BNP) measurement could be useful in determination of functional capacity in patients suffering from chronic heart failure. BACKGROUND: Evaluating functional capacity is a crucial factor in the follow-up of patients with chronic heart failure. There are numerous methods for measuring functional capacity and their relative merits remain under discussion. Clinical classifications are very subjective and other methods are difficult to use in clinical practice. METHODS: We evaluated functional capacity in 151 consecutive patients using the 6-min walk test. All patients were clinically classified using the New York Heart Association (NYHA) classification. We measured BNP plasma levels using a bedside BNP test. RESULTS: Six minute walk test performance decreased through NYHA classes 1 to 4 (469+/-87, 411+/-82, 325+/-83 and 196+/-63 m, respectively, P<0.01) and BNP levels increased through NYHA classes 1 to 4 (26.3+/-7.2, 73+/-13, 401+/-74 and 924+/-84 pg/ml, respectively, P<0.001). There was a significant correlation between 6-min walk test performance and BNP plasma levels (R=0.69 P<0.001) and a weaker correlation between BNP and left ventricular ejection fraction (R=0.45 P<0.04). In some patients there was a mismatch between NYHA classification and 6-min walk test performance. In all cases BNP could correct the clinical estimation of functional capacity. When we divided the patients into three sub-groups within each NYHA class, we showed that using BNP could better define functional capacity in patients suffering from chronic heart failure in NYHA classes I to III. CONCLUSION: The measurement of BNP levels thus usefully supplements the clinical examination. The existence of bedside BNP testing methods facilitates its use in routine clinical practice. It also permits easier follow-up of patients with chronic heart failure.