## 1 Introduction  
Monitoring heart activity and its associated hemodynamic parameters plays a significant role in managing cardiovascular disorders (CVD). Dysfunction related to the heart muscle, aside from issues within the vessel network, encompasses conditions such as heart failure (HF), heart valve disease, arrhythmia and stroke [1; 2; 3; 4]. One of the key cardiovascular markers is left ventricular ejection time (LVET or ET), which characterizes ventricular performance metrics, including contractility. It offers insights into the efficiency of the heart's pumping mechanism and can aid in the diagnosis and management of the afore-mentioned disorders. Moreover, being supported by additional markers such as isovolumetric contraction time (IVCT) and relaxation time (IVRT), it derives the MyocardialPerformance Index (MPI or TEI-index), a simple tool to identify cardiac dysfunction. In recent years, there has been growing interest in measuring this parameter for therapeutic purposes with novel drugs [2]. A significant advancement in personalized healthcare would involve making LVET assessment accessible through wearable technologies. Individuals could seamlessly integrate this parameter into their daily lives through portable devices aimed at hemodynamic monitoring. The continuous data stream would not only provide valuable insights into their cardiovascular health but also enable the early detection of abnormalities and timely intervention. The potential benefits in terms of preventing heart-related complications and improving overall well-being are immense. Also, due to the portability capabilities of wearable devices, cardiovascular performance could be monitored remotely, reducing the need for periodic visits to a medical office. Over the last decade, wearable devices have gained significant traction in the healthcare domain by providing accurate readings, such as heart rate (HR) and blood oxygen saturation ratio SpO2 [5; 6; 7]. Photoplethysmography (PPG) is one of the most popular current technologies used in these devices, holding enormous potential in the field of hemodynamics. As a result, companies like Samsung have developed smartwatches with blood pressure (BP) estimation [8; 9], although there are still challenges to overcome. Therefore, this capability is more addressable to the general market user rather than being primarily intended for clinical applications. Given that PPG waveform morphology closely resembles arterial blood pressure (ABP) tracing [10; 11; 12; 13], it shares vital cardiovascular information. The most distinctive fiducial points along the signal contour are the tidal wave (TDW) and the dicrotic wave (DCW). However, advancements cannot be achieved without a proper interpretation of the waveform in synergy with human physiology and the associated deviations. The dicrotic wave feature has been reported since [PERSON]'s studies in the cardiovascular domain [14; 15], where he published the first cardiac phase diagram, depicted in Figure 1a. This fiducial point has shown a strong link with vasomotor activity, especially during the action of therapeutic drugs [16; 17; 18]. Under vasopressor infusion, the dicrotic wave decreases in amplitude and moves toward the systolic point (SYS). Conversely, in the opposite effect, the point's location moves to the next diastolic valley (DIA) region at the same time with an amplitude amplification effect. Initially, this cardiovascular marker was also associated with the ending of the systolic phase, marked by LVET. However, during the development of medical signal processing, the correlation between DCW and ejection time was not thoroughly investigated. The technical limitations of the devices used to record cardiac events primarily consisted of two factors [19; 20; 21]. Firstly, the mechanical nature of the transducer used, such as manometers, had a reduced dynamic response due to fluid inertia, reducing the ability to record rapid changes during invasive arterial waveform tracing.