P1754 Externally recorded cardiac acoustics to optimise cardiac resynchronisation therapy

BACKGROUND: Mechanical characteristics of the left ventricle (LV) may be encoded in cardiac acoustic signatures within low frequency ranges. PURPOSE: We aimed to characterise i) acoustic features in the frequency domain in subjects with normal LV function (Group 1) and patients with heart failure with reduced ejection fraction (HFREF) indicated for cardiac resynchronisation therapy (CRT, Group 2) and ii) their relationship with aortic velocity time integral (VTI) with respect to signal to noise ratio (SNR) during atrio-ventricular (AV) optimisation of CRT. METHOD: 15-seconds segments of heart sounds obtained from electronic (e-) stethoscope recordings of subjects in Group 1 (N¼21), Group 2 (N¼28), and 4 subjects undergoing AV optimization of CRT were subjected to a novel signal processing method to detect S1 and S2 sounds envelopes and extract frequency-domain acoustic features from the detected envelopes. During AV optimization of CRT (pacing at 90bpm), aortic VTI and EA duration were measured with Doppler on echocardiography from a range of paced AV delays (PAVD). The optimal PAVD was found at the highest aortic VTI with the best EA duration and pattern for LV filling. The SNR of the acoustic features were calculated by dividing the range of signals across all the tested PAVD by the average size of the standard error of mean (SEM) (the noise) at each PAVD. RESULTS: 1) Two frequency-domain features extracted from the S1 envelopes (AV_S1_B and AV_S1_C) were higher in Group 1 compared to Group 2 (fig. 1). No difference was found in the same features extracted from the S2 envelopes (AV_S2_B and AV_S2_C) between the 2 groups. 2) During AV optimization of CRT, AV_S1_C correlated with aortic VTI in subjects with high SNR (e.g. SNR¼7.8: N¼10, r¼0.67, p¼0.03, 2-tailed) but not in those with low SNR (e.g. SNR¼3.9: N¼7, r¼-0.322, p¼0.48). 3) In the subject with the highest SNR (7.8), the PAVD at the highest value of AV_S1_C coincides with the optimal PAVD derived from echocardiography (fig. 2). CONCLUSION: e-Cardiac acoustics offer a potential novel method to diagnose HFREF and optimize AVD in CRT. Future studies to confirm the current findings and improve the SNR of this method are needed for clinical utility.