Intrinsic Frequency Method for Noninvasive Diagnosis of Left Ventricular Systolic Dysfunction

We have recently developed a new mathematical method, intrinsic frequency (IF) method, that views the left ventricle-arterial system as a coupled dynamic pumping system which is decoupled upon the closure of the aortic valve. Utilizing this method, given an arterial blood pressure waveform we are able to extract two intrinsic frequencies ($\omega_{1}$ and $\omega_{2})$ correlating to systole when the left ventricle (LV) and aorta (vasculature) act as a coupled dynamic pumping system and diastole where the dynamics of the LV is removed. Each of these dynamical pumping states has an inherent frequency of operation ($\omega _{1}$ and $\omega_{2})$ which gives information about LV systolic function ($\omega_{1})$ as well as arterial dynamics ($\omega_{2})$. IF methodology extracts $\omega_{1}$ and $\omega_{2}$ from the pressure wave. This method was applied to invasive aortic pressure waveforms and noninvasively measured carotid pressure waveforms. Our results shows that $\omega_{1}$ is elevated in patients with LV systolic dysfunction (LVSD). However, $\omega _{1}$ remains relatively constant under healthy conditions as age advances. Our results indicate that IF methodology can be used to detect LVSD from a single pressure waveform. One unique advantage of the IF method is only the shape of the waveform is required. Therefore, $\omega _{1}$ can be easily derived from noninvasive measurements and monitored continuously.