Transthoracic bioimpedance and brain natriuretic peptide assessment for prognostic stratification of outpatients with chronic systolic heart failure

Abstract

Background: In patients with chronic heart failure, physical evaluation and clinical judgment may be inadequate for prognostic stratification.

Hypothesis: Information obtained with simple bedside tests would be helpful in patient management.

Methods: We report on 142 outpatients with systolic heart failure seen at our heart failure unit from 2007 to 2010 (ages 69.4 ± 8.9 years; ejection fraction [EF] 30.6 ± 6.1%; 43% with implanted defibrillators and/or resynchronization devices). At their first visit, we assessed levels of brain natriuretic peptide (BNP) (pg/mL), evaluated transthoracic conductance (TFC) (1/kΩ) by transthoracic bioimpedance, and performed echocardiography.

Results: Four-year mortality was 21.2%. At multivariate analysis, surviving and deceased subjects did not differ regarding New York Heart Association, age, gender, heart failure etiology, or EF at index visit. Patients who died had higher BNP and TFC (BNP = 884 ± 119 pg/mL vs 334 ± 110 pg/mL; TFC = 50 ± 8/kΩ vs 37 ± 7/kΩ, both P < 0.001]. Patients with BNP < 450 pg/mL and TFC < 40/kΩ had a 2.1% 4-year mortality, compared to 46.5% mortality of patients having BNP ≥ 450 pg/mL and TFC ≥ 40/kΩ. BNP ≥ 450 pg/mL and TFC ≥ 40/kΩ showed high sensitivity (91%) and specificity (88%)in identifying patients who died at follow-up.

Conclusions: The combined use of BNP and impedance cardiography during the first assessment of a patient in a heart failure unit identified those carrying a worse medium-term prognosis. This approach could help the subsequent management of patients, allowing better clinical and therapeutic strategies.

Figure 1

Receiver operating characteristic curve showing the predictive value for 1‐year mortality of the association of brain natriuretic peptide (BNP) ≥450 pg/mL and thoracic fluid content (TFC) ≥40/kΩ. Abbreviations: AUC, area under the curve.

Figure 2

Kaplan‐Meier survival curves in patients divided into 4 groups according to brain natriuretic peptide (BNP) and thoracic fluid content (TFC) values at index visit. Group 1 = BNP < 450 pg/mL and TFC ≤ 40/ kΩ; group 2 = BNP ≥ 450 pg/mL and TFC < 40/kΩ; group 3 = BNP < 450 pg/mL and TFC ≥ 40/kΩ; group 4 = BNP ≥ 450 pg/mL and TFC ≥ 40/kΩ. Comparisons were as follow: groups 2 and 3 vs group 1, P = 0.0028; group 2 and 3 vs group 4, P = 0.0136; group 1 vs group 4, P < 0.0001.