Intrinsic Frequency and the Single Wave Biopsy

Abstract

Insulin resistance is the hallmark of classical type II diabetes. In addition, insulin resistance plays a central role in metabolic syndrome, which astonishingly affects 1 out of 3 adults in North America. The insulin resistance state can precede the manifestation of diabetes and hypertension by years. Insulin resistance is correlated with a low-grade inflammatory condition, thought to be induced by obesity as well as other conditions. Currently, the methods to measure and monitor insulin resistance, such as the homeostatic model assessment and the euglycemic insulin clamp, can be impractical, expensive, and invasive. Abundant evidence exists that relates increased pulse pressure, pulse wave velocity (PWV), and vascular dysfunction with insulin resistance. We introduce a potential method of assessing insulin resistance that relies on a novel signal-processing algorithm, the intrinsic frequency method (IFM). The method requires a single pulse pressure wave, thus the term " wave biopsy."

Cardiac Triangle Mapping: A New Systems Approach for Noninvasive Evaluation of Left Ventricular End Diastolic Pressure

“…The decoupling coordinates are represented as the relative height of decoupling at the dicrotic notch (RHDN) and the time of decoupling at the dicrotic notch (T 0 ). Previous studies [8,17] have indicated that LVEF (surrogate of LV contractility), LV-arterial coupling optimality, and central pulse wave velocity (a major determinant of arterial impedance and pulsatile afterload) can be evaluated as a function of IF parameters [9,10,12,14] (Figure 2). Previous results indicate that LV contractility and afterload can be approximated as a function of IFs (ω 1 , ω 2 , .…”

“…Recently, we introduced the intrinsic frequency (IF) concept that reveals clinically relevant information about the dynamics of the left ventricle (LV), arterial system, and their interactions [7][8][9][10]. IF frequencies are operating frequencies based on the Sparse Time-Frequency Representation (STFR) [11], treating the LV combined with the aorta and the remaining peripheral arteries as a coupled dynamical system (heart + aortic tree), which is decoupled upon closure of the aortic valve [8,9,12].…”

“…The first IF, ω 1 , describes the dynamics of the systolic phase of the cardiac cycle where the LV and aorta (vasculature) are a coupled dynamic system [7][8][9]. The second IF, ω 2 , is dominated by the dynamics of the vasculature [9,10,12].…”

“…Previous studies have indicated that ω 1 is mainly determined by the LV contractility while ω 2 is mostly determined by vascular function (e.g., arterial stiffness, arterial wave dynamics, and afterload) [9,10,12,14]. In a blind clinical study [8], it was shown LV ejection fraction (LVEF, a surrogate of LV contractility) derived using IF applied to carotid waveforms extracted using an iPhone [8] were similar to those measured from cardiac magnetic resonance imaging (CMRI) (r = 0.74, p < 0.00001).…”

Intrinsic Frequencies of Carotid Pressure Waveforms Predict Heart Failure Events

“…Their results indicated that ω 2 values were similar among younger participants but gradually diverged with age or progressive disease states. 12 , 15 In addition, the prior theoretical work showed that cardiac pulsatile power reaches a minimum at any given arterial stiffness at a heart rate where the difference between ω 1 and ω 2 is zero. 12 Thus, it was concluded that the total frequency variation (Δω=ω 1 −ω 2 ) may provide an additional novel measure of optimal ventricular vascular coupling and vascular health.…”