Molecular ratio of mature B-type natriuretic peptide in acute heart failure: an indicator for ventricular contractile recovery

Heart failure with improved ejection fraction: Beyond diagnosis to trajectory analysis

Left ventricular (LV) systolic dysfunction represents a highly treatable cause of heart failure (HF). A substantial proportion of patients with HF with reduced ejection fraction (EF;HFrEF) demonstrate improvement in LV systolic function (termed HF with improved EF [HFimpEF]), either spontaneously or when treated with guideline-directed medical therapy (GDMT). Although it is a relatively new HF classification, HFimpEF has emerged in recent years as an important and distinct clinical entity. Improvement in LVEF leads to decreased rates of mortality and adverse HF-related outcomes compared to patients with sustained LV systolic dysfunction (HFrEF). While numerous clinical and imaging factors have been associated with HFimpEF, identification of which patients do and do not improve requires further investigation. In addition, patients improve at different rates, and what determines the trajectory of HFimpEF patients after improvement is incompletely characterized. A proportion of patients maintain improvement in LV systolic function, while others experience a recrudescence of systolic dysfunction, especially with GDMT discontinuation. In this review we discuss the contemporary guideline-recommended classification definition of HFimpEF, the epidemiology of improvement in LV systolic function, and the clinical course of this unique patient population. We also offer evidence-based recommendations for the clinical management of HFimpEF and provide a roadmap for future directions in understanding and improving outcomes in the care of patients with HFimpEF.

B-Type Natriuretic Peptide (BNP) Revisited—Is BNP Still a Biomarker for Heart Failure in the Angiotensin Receptor/Neprilysin Inhibitor Era?

Simple Summary

Active BNP-32, less active proBNP-108, and inactive N-terminal proBNP-76 all circulate in the blood. The circulating protease neprilysin has lower substrate specificity for BNP than ANP, while proBNP and N-terminal proBNP are not degraded by neprilysin. Currently available BNP immunoassays react with both mature BNP and proBNP; therefore, measured plasma BNP is mature BNP + proBNP. Because ARNI administration increases mature BNP, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI administration reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase of mature BNP due to inhibition of degradation by neprilysin, resulting in lower plasma BNP levels. In the ARNI era, BNP remains a useful biomarker for heart failure, though mild increases early during ARNI administration should be taken into consideration.

Abstract

Myocardial wall stress, cytokines, hormones, and ischemia all stimulate B-type (or brain) natriuretic peptide (BNP) gene expression. Within the myocardium, ProBNP-108, a BNP precursor, undergoes glycosylation, after which a portion is cleaved by furin into mature BNP-32 and N-terminal proBNP-76, depending on the glycosylation status. As a result, active BNP, less active proBNP, and inactive N-terminal proBNP all circulate in the blood. There are three major pathways for BNP clearance: (1) cellular internalization via natriuretic peptide receptor (NPR)-A and NPR-C; (2) degradation by proteases in the blood, including neprilysin, dipeptidyl-peptidase-IV, insulin degrading enzyme, etc.; and (3) excretion in the urine. Because neprilysin has lower substrate specificity for BNP than atrial natriuretic peptide (ANP), the increase in plasma BNP after angiotensin receptor neprilysin inhibitor (ARNI) administration is much smaller than the increase in plasma ANP. Currently available BNP immunoassays react with both mature BNP and proBNP. Therefore, BNP measured with an immunoassay is mature BNP + proBNP. ARNI administration increases mature BNP but not proBNP, as the latter is not degraded by neprilysin. Consequently, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase in mature BNP mediated by inhibiting degradation by neprilysin, which lowers plasma BNP levels. These results suggest that even in the ARNI era, BNP can be used for diagnosis and assessment of the pathophysiology and prognosis of heart failure, though the mild increases early during ARNI administration should be taken into consideration.

A new biomarker of cardiac resynchronization therapy response: cGMP to mature BNP ratio

BACKGROUND

Biomarkers that can predict cardiac resynchronization therapy (CRT) response have not yet been identified. The purpose of this study was to assess whether individual measurements of four brain/B-type natriuretic peptide (BNP) forms, coupled with cyclic guanosine monophosphate (cGMP) might contribute to the prediction of echocardiographic CRT responders.

METHODS

A BNP precursor (proBNP) and total BNP (= proBNP + mature BNP) were measured with newly developed kits, while an N-terminal fragment of proBNP (NT-proBNP) and cGMP were measured with commercial kits on the day before CRT implantation. Estimated mature BNP (emBNP = total BNP-proBNP), and the ratio of cGMP to each BNP form, as well as the concentrations of three other BNP forms, were prospectively investigated for their capability in predicting a response to CRT. A CRT responder was defined as an improvement in left ventricular ejection fraction >10% and/or a reduction in left ventricular end-systolic volume >15% at 6-month follow-up.

RESULTS

Out of 77 patients, 46 (60%) were categorized as CRT responders. Among the measurement parameters, only the highest quartile of the cGMP to emBNP ratio was an independent predictor of CRT responders (odds ratio 4.87, 95% confidence interval 1.25-18.89, p = 0.02). The cGMP to emBNP ratio was associated with the cumulative events of heart failure hospitalization within one year following CRT implantation (log-rank p = 0.029).

CONCLUSIONS

The cGMP to emBNP ratio could be utilized as a predictive biomarker of CRT responders. (Clinical Study on Responder Prediction in Cardiac Resynchronization Therapy Using Individual Molecular Measurement of Natriuretic Peptide: UMIN R000038927).