Circulating Plasma Proteins in Aortic Stenosis: Associations With Severity, Myocardial Response, and Clinical Outcomes

Abstract

Background: Echocardiographic indexes of aortic stenosis may not comprehensively reflect disease morbidity. Plasma proteomic profiling may add prognostic value in these patients.

Methods and results: Proximity extension assays (Olink) of 183 circulating cardiovascular and inflammatory proteins were performed in a prospective follow-up study of 122 asymptomatic/minimally symptomatic patients (mean±SD age, 69.1±10.9 years; 61% men) with moderate to severe aortic stenosis and preserved left ventricular ejection fraction. Protein signatures of higher-risk echocardiographic subgroups were determined. Associations of proteins with the primary composite outcome (heart failure hospitalization, progression to New York Heart Association class III-IV, or all-cause mortality) were evaluated using competing risk analyses, with aortic valve replacement being the competing risk. Network analysis unveiled mutually exclusive communities of proteins and echocardiographic parameters, connected only through NT-proBNP (N-terminal pro-B-type natriuretic peptide). Members of the tumor necrosis factor receptor superfamily (TNFRSF1A, TNFRSF1B, and TNFRSF14), and trefoil factor-3 were major hub proteins among the circulating biomarkers. Left ventricular global longitudinal strain >-15% was associated with higher levels of proteins, primarily of inflammation and immune regulation, whereas aortic valve area <1 cm², E/e' >15, and left atrial reservoir strain <20% were associated with higher levels of NT-proBNP. Of 14 proteins associated with the primary end point, phospholipase-C, C-X-C motif chemokine-9, and interleukin-10 receptor subunit β demonstrated the highest hazard ratios after adjusting for clinical factors (q<0.05).

Conclusions: Plasma proteins involved in inflammation and immune regulation were differentially expressed in patients with aortic stenosis with reduced left ventricular global longitudinal strain, and associated with adverse clinical outcomes. Their incorporation into aortic stenosis risk stratification warrants further assessment.

Keywords: aortic stenosis; biomarkers; inflammation; proteomics.

Figure 1. Study design.

Study design of 122 participants with available proteomic evaluation. AVA indicates aortic valve area; LVEF, left ventricular ejection fraction; NYHA, New York Heart Association; TTE, transthoracic echocardiography; and V_max, peak transaortic velocity.

Figure 2. Network analysis of circulating and echocardiographic biomarkers.

Undirected graph estimated from a merged data set of echocardiographic parameters (orange) and plasma protein (green: inflammatory; blue: cardiovascular) abundance measurements (OLINK) using the graphical lasso estimator. Color and thickness of edges represent the direction and magnitude of Pearson correlations (red: positive; blue: negative). See Data S1. for a list of biomarkers. Aortic MeanPG indicates transaortic mean pressure gradient; AVA continuity, aortic valve area by continuity equation; AVA planimetry, aortic valve area by planimetry; AVAi, aortic valve area index; corr, correlation; CVD, cardiovascular disease; DI, dimensionless index; E/e’‐Avg, ratio of mitral early diastolic velocity to averaged lateral and septal annular early diastolic velocities; ELI, energy loss index; IVSd, interventricular septal thickness in diastole; LA‐a’, lateral annular early diastolic velocity; LA‐e’, lateral annular late diastolic velocity; LA‐E/e’, ratio of mitral early diastolic velocity to lateral annular early diastolic velocity; LA‐s, lateral annular systolic velocity; LAScd‐Ave, average left atrial conduit strain; LASct‐Ave, average left atrial contractile strain; LASr‐Ave, average left atrial reservoir strain; LAVI, left atrial volume index; LVEDV, left ventricular end‐diastolic volume; LVEF, left ventricular ejection fraction; LVESV, left ventricular end‐systolic volume; LVIDd, left ventricular internal dimension in diastole; LVIDs, left ventricular internal dimension in systole; LVMI, left ventricular mass index; LVPWd, left ventricular posterior wall thickness in diastole; Mitral DT, mitral deceleration time; PASP, pulmonary artery systolic pressure; SA‐a’, septal annular early diastolic velocity; SA‐e’, septal annular late diastolic velocity; SA‐E/e’, ratio of mitral early diastolic velocity to septal annular early diastolic velocity; SRa‐Ave, average left atrial late diastolic strain rate; SRe‐Ave, average left atrial early diastolic strain rate; SRs‐Ave, average left atrial systolic strain rate; SWL, stroke work loss; TR‐V _max, Maximum velocity of tricuspid regurgitation

Figure 3. Subgroup analyses of protein abundance.

A, Volcano plots from differential abundance analyses between subgroups of echocardiographic classification, adjusted for age, sex, hypertension, serum creatinine, and body mass index. B Heat map of normalized values of statistically significant variables from subgroup analyses, with groups and statistical significance (−log10 q[value]) shown on top and left margin, respectively. See Data S1. for a list of biomarkers. AVA indicates aortic valve area; E/e’, ratio of mitral early diastolic velocity to averaged annular early diastolic velocities; GLS, global longitudinal strain; LASr, left atrial reservoir strain; NPX, normalized protein expression.

Figure 4. Plasma protein associations with clinical outcomes.

Volcano plot from the competing‐risks regression models with aortic valve replacement (AVR) as the competing risk to the primary clinical outcome. See Data S1. for a list of biomarkers.

Figure 5. Proteomic evaluation in moderate to severe aortic stenosis.

In asymptomatic/minimally symptomatic patients with moderate to severe aortic stenosis (AS) and preserved left ventricular ejection fraction (LVEF), proteomic analysis of 184 circulating cardiovascular and inflammatory proteins identified (1) independent clustering of circulating biomarkers and cardiac structural/functional parameters, (2) distinct protein signatures for echocardiographic indexes of higher‐risk AS subgroups, and (3) the primacy of novel prognostic circulating biomarkers over echocardiographic parameters of AS. CXCL9 indicates C‐X‐C motif chemokine 9; E/e’, ratio of mitral early diastolic velocity to averaged annular early diastolic velocities; IL10RB, IL10‐receptor subunit β; LASr, left atrial reservoir strain; LV‐GLS, left ventricular global longitudinal strain; NT‐proBNP, N‐terminal pro‐B‐type natriuretic peptide; NYHA, New York Heart Association; and PLC, phospholipase C.