A novel indicator derived from heart sound energy map obtained by a wearable device can evaluate LV function.

Background: Assessing cardiac function is important for early diagnosis, prognosis, and out-hospital follow-up for heart failure patients. It is especially crucial to identify a cost-effective and easily adaptable approach for evaluating cardiac function at home.

Objective: Our purpose was to investigate whether some metrics derived from the heart sound energy map obtained by a wearable heart acquisition device could reflect the cardiac function.

Methods: 99 subjects were categorized into two groups based on whether their left ventricular ejection fraction was <50%. In the heart sound energy map mode, time intervals of energy intensity between 2100 and 2400 of the first heart sound was denoted as "a," 1500-1800 as "b," 1200-1500 as "c," and 600-900 as "d." The ratio of the time difference between adjacent energy intensity intervals and the high-energy interval was calculated, referred to as the Red index [(b-a)/a], Brn index [(c-b)/b], and Yel index [(d-c)/c], respectively.

Results: Significant differences were observed in the Red index and Yel index between the two groups (P < .001 and P = 0.017, respectively). The Red and Yel indices showed a significant correlation with ejection fraction (EF) value (r = -0.50 and -0.27, P < .001 and P = .008, respectively). The intraclass correlation coefficient conformance test indicated that the intragroup correlation coefficients of the Red index with EF were 0.57. Receiver operating characteristic analysis revealed that the Red index exhibits strong diagnostic value for EF values <50% with an AUC of 0.86 (95% CI: 78% ~ 94%).

Conclusions: The Red index, derived from the heart sound energy map, demonstrates a significant correlation with both the EF value and Tei index and can identify the reduction of left ventricular EF.