Seismocardiography Can Assess Cardiopulmonary Exercise Test Parameters in Patients with Heart Failure

Abstract

Background Cardiopulmonary exercise testing (CPET) is an important risk stratification tool in patients (pts) with heart failure (HF) and measures such as peak VO 2 , VE/VCO 2 slope, Oxygen uptake efficiency slope (OUES) have prognostic value in HF pts. In our previous studies, we have shown that wearable chest patch based seismocardiogram (SCG) signals - the local body vibrations of the chest wall in response to cardiac ejection - can accurately quantify cardiac contractility changes [pre-ejection period (PEP)], which can be used to differentiate between compensated and decompensated HF pts following exercise (six-minute walk test). Hypothesis We hypothesized that CPET variables can be assessed using changes in PEP from simultaneously recorded SCG. The degree of impairment in myocardial contractility should reflect the severity of HF and it could be used for risk stratification. Methods CPET was performed using a modified Naughton protocol. SCG and ECG signals were simultaneously recorded using our custom built wearable chest patch ( Fig. 1 A). We segmented these signals into heart beats and averaged the beats over 30 seconds window and compared the PEP (normalized to the resting values) with corresponding CPET variables. We compared changes in PEP (percentage change from baseline value) following exercise with CPET variables. Results We enrolled 8 patients with HF and reduced ejection fraction (age 61 ± 11, 50% women, ejection fraction 0.25 ± 0.08). We found that normalized PEP at anaerobic threshold (AT) correlated with VO 2 at AT (R 2 = 0.56), while normalized PEP at VO 2 max correlated with OUES (R 2 =0.64) and O 2 pulse at VO 2 max (R 2 =0.43). Percentage change in PEP following exercise correlated with VO 2 at AT (R 2 = 0.61) and VO 2 max (R 2 = 0.48). Conclusions Using SCG and simultaneous ECG we can assess corresponding CPET variables for patients with HF. This wearable device can potentially provide value in stratifying risk in patients with HF by tracking hemodynamic parameters during daily activities.