Hemodynamics of acute decompensated heart failure in patients with very low NP levels

Abstract

Abstract Background/Introduction Natriuretic Peptides are hormones secreted by the heart in response to cardiomyocyte stretch. The principal biological action of NP is natriuresis, diuresis and vasodilation. These are salutary effects in acute decompensated heart failure (ADHF). Some patients admitted with ADHF have very low NP levels. It is unknown if this is due to a defect in biosynthesis or inadequate stimulation. Purpose We analyzed data from the National heart Lung and Blood institute sponsored ESCAPE trial which included patients admitted with acute decompensated heart failure who underwent hemodynamic assessment with pulmonary artery catheters at admission and after diuresis. Our aim was to evaluate if there were characteristic hemodynamic findings among patients with very low NP levels at admission which differed from those who had elevated NP levels at admission. Methods We performed a secondary analysis of the ESCAPE Trial. We defined very low BNP as patients with BNP level at admission <50 pg/mL. We then compared baseline characteristics between the groups. Continuous groups were compared using X-square test, and Categorical variables were compared using Wilcoxon-signed-Rank-Sum test. We compared groups by Demographic, Anthropometric, Laboratory, and Functional status. We then performed propensity matching on Age, Sex, and BMI and then compared groups. Results 25/351 patients had very low BNP (<50pg/mL). Patients in the low BNP group had higher BMI than those with elevated BNP (35.8 vs. 28.9 p<0.001). The cohort with low BNP was younger. (50.2 vs. 56.4 p=0.029). In propensity matched cohorts of Age, Sex, BMI. Cardiac output was elevated in the low BNP cohort. (5.2 vs. 3.9 p=0.011). However, Cardiac Index was similar between the groups (2.2 vs. 2.0 p=0.244). Patients in the Low NP group had lower pulmonary capillary wedge pressure (PCWP) compared to those with elevated BNP. (16.5 vs. 25.4 p=0.023). The groups had similar RA pressures (11.5 vs. 13.0 p=0.515). The calculated transmural pressure (PCWP – RA pressure) was lower in the low NP group. There was a reduction in BNP levels at discharge among the group with elevated BNP at admission (1072.6 (baseline) 798.8 (discharge)) In the low BNP group there was an increase in BNP at time of discharge (20.2 (baseline) to 172.7 (discharge)). In follow-up, the low BNP group had reduction in BNP compared to their discharge levels. The group with elevated BNP had elevated BNP at follow-up in 3 and 6 months. Length of stay was shorter in the Low BNP group (6.2 vs. 8.8, p=0.052). Conclusion(s) In this secondary analysis of the ESCAPE trial, we find that those patients admitted with ADHF who have unexpectedly low BNP have lower transmural pressures at baseline compared to those who have elevated BNP levels. This suggests that there may not be adequate stimulus for cardiac wall distention and release of BNP. Funding Acknowledgement Type of funding sources: None.