A Signal in the Noise: Noninvasive Acoustical Evaluation of Continuous Flow Left Ventricular Assist Device

Purpose This is a single center prospective research study using an Apple iPhone 7 stock voice recorder application to assess the relationship between LVAD frequency and invasive hemodynamics. Methods Patients were enrolled prior to their standard of care invasive speed adjustment/optimization study or routine RHC. A 35 second recorded auscultation using an iPhone 7 placed at the location of apex overlying the LVAD. Chest x-ray was utilized for estimation of ideal iPhone placement. Invasive hemodynamic data was recorded and baseline characteristics collected at time of acoustic acquisition. Acoustic data was analyzed post hoc using Audacity sound analysis software to produce frequency and decibel values for each audio file. Variation in frequency and decibels were observed between HVAD and HM3 despite differences in speed and rotational flow. Results 8 consecutive patients were studied, median age 59 years, male (63%) with 75% African American and 25% Caucasian. Mean height 173cm and weight 98kg. HVAD (3), Heartmate II (1) and Heartmate 3 (4) were included. Median CVP was 12mmHg, PCWP 17 mmHg, CO(F) 4.7, CI(F) 2.2, LVEDD 6.45cm and PASAT 62.9%. CVP was evaluated over a range of 7-15 mmHg and PCWP ranged from 10-23 mmHg. Mean frequency of HM3 was 53.5 Hz, HM2 68Hz and HVAD 49.7Hz. LVAD frequencies ranged from 48-63Hz in HM3, 68Hz HM2 and 47Hz-53Hz in HVAD. Pearson Correlation Coefficient R = -0.6616 (R² = 0.4377) for dB and PCWP (P=.07). This moderate negative correlation described a tendency for high dB variable scores to coincide with low PCWP scores. Conclusion This interim analysis demonstrates a relationship between cardiac filling pressures and acoustics. Using a universal audio recording application may aid in the medical management of LVAD patients in the inpatient and outpatient setting. This cross platform technology should be further investigated as a potential diagnostic tool.