Noninvasive iPhone Measurement of Left Ventricular Ejection Fraction Using Intrinsic Frequency Methodology*

Abstract

Analysis of carotid waveforms using intrinsic frequency methods can be used to document left ventricular ejection fraction with accuracy comparable with that of MRI. The measurements require no training to perform or interpret, no calibration, and can be repeated at the bedside to generate almost continuous analysis of left ventricular ejection fraction without arterial cannulation.

Proof-of-concept for a non-invasive, portable, and wireless device for cardiovascular monitoring in pediatric patients

“…A one-way ANOVA comparison of ω 1 across the pediatric and adult cohorts demonstrated a significant difference (F = 7.3, Prob>F = 0.0001). Post-hoc analysis revealed a significant difference between the adult cohort (ω 1 = 99 +/-5 bpm) and both the 0-4 year old (ω 1 = 111 +/-2 bpm; p = 0.0006) and [15][16][17][18][19] year old (ω 1 = 105 +/-5 bpm; p = 0.02) cohorts ( Fig 4A). A one-way ANOVA comparison of ω 2 across all pediatric and adult cohorts showed a significant difference (F = 4.8, Prob>F = 0.003).…”

“…We also showed the difference between IFs values (ω 1 and ω 2 ) of pediatric population and of adults with structurally normal hearts and normal LV function. This is clinically significant since physiologically relevant measures such as LVEF can be approximated from ω 1 and ω 2 as shown by Pahlevan et al [17] and Armenian et al [18]). Given the wide range of body size in the pediatric population, the sensor head of the Vivio was modified to assess the ease-of-use and hand pressure required to capture non-invasive carotid artery waveforms in pediatric populations.…”

“…IF can be computed using this formula in a fraction of second. Details regarding mathematical formulation of IF method [12], its computational procedure [12], and its convergence/accuracy [19] can be found in previous publications [12,17,19].…”

“…Exclusion criteria included patients with congenital heart disease or heart failure. A population of 28 adults ages 20-50 years with normal cardiac function and IFs collected from a prior IRB-approved study served as the comparison group [17].…”

“…IF uses an integrative systems approach that considers the LV and arterial network as a coupled dynamical system (LV + arterial tree) that is decoupled upon closure of the aortic valve [13][14][15][16]. Previous clinical studies have shown that the IF method can be used to estimate LVEF from non-invasive arterial waveforms measured by an iPhone [17]. Recently, a wireless handheld prototype device (Vivio) capable of simultaneous collection of arterial pulse waveform and phonocardiogram data from the carotid artery was proven to accurately estimate LVEF using the IF method in a large study of adult patients with anthracycline exposure secondary to treatment of childhood cancer [18].…”