Acoustic cardiography S3 detection use in problematic subgroups and B-type natriuretic peptide "gray zone": Secondary results from the Heart failure and Audicor technology for Rapid Diagnosis and Initial Treatment Multinational Investigation

Background: Dyspneic emergency department (ED) patients present a diagnostic dilemma. The S3, although highly specific for acute heart failure (AHF) and predicting death and readmission, is often difficult to auscultate. The HEart failure and Audicor technology for Rapid Diagnosis and Initial Treatment (HEARD-IT) multinational trial evaluated the S3 via acoustic cardiography (Audicor). Our goal in this secondary analysis was to determine if the strength of the S3 can provide diagnostic/prognostic information in problematic heart failure subgroups. Methods: Dyspneic ED patients older than 40 years and not on dialysis were prospectively enrolled. A gold standard AHF diagnosis was determined by 2 cardiologists blinded to acoustic cardiography results. The S3 strength parameter was delineated on a scale of 0 to 10. This secondary analysis of subgroups from the HEARD-IT database used univariate/multivariate regression to determine the diagnostic/prognostic ability of the S3 strength. Results: In the 995 patients enrolled, S3 strength was a significant prognosticator in univariate analysis for adverse events but not in a multivariable model. In patients with "gray zone" B-type natriuretic peptide (BNP) levels (100-499 pg/mL), acoustic cardiography increased diagnostic accuracy of AHF from 47% to 69%. Acoustic cardiography improved S3 detection sensitivity in obese patients when compared to auscultation. Conclusion: The strength of the S3 gallop provides rapid results that assist with identification of AHF in selected populations. S3 detection complements the use of BNP in the gray zone, and its diagnostic/prognostic ability is largely unaffected by body mass index and renal function. S3 strength shows promise as a diagnostic and prognostic tool in problematic HF subgroups.