# Calculation of Intracoronary Pressure-Based Indexes with JLabChart
## 1 Introduction  
Coronary heart disease is a major cause of death and morbidity worldwide [1]. Coronary revascularization by means of Percutaneous Coronary Intervention (PCI) is the most widely used treatment for coronary artery disease (CAD) [2]. Coronary angiography represents the standard diagnostic examination for CAD, to assess coronary stenoses on the basis of their impact on coronary lumen, as it is able to characterize stenosis geometry [3]. In fact, angiography allows a visual evaluation of stenosis severity, but it does not provide details on the actual impact of the stenosis on blood flow. Thus, coronary angiography allows physicians to assess the status of coronary arteries and, in particular, of specific features such as the shape, length, and eccentricity of the lesion [4]. However, it is not able to provide information on the hemodynamic impact of coronary stenoses [5]. For this reason, the Fractional Flow Reserve (FFR) was developed, which represents the mean distal-to-proximalpressure ratio across a coronary stenosis under maximal hyperemia [6]. In other words, FFR is a diagnostic index indicating whether or not a particular stenosis of a coronary artery might be causing myocardial ischemia, that is, an impairment in myocardial blood perfusion because of the physical restraint brought about by the narrowing of vessel lumen (stenosis). FFR has been proven effective in identifying ischemia-causing stenoses [7] and in guiding PCI [8; 9; 10]. FFR is measured by definition under maximal hyperemia (an increase in blood flow), induced by means of a vasodilation of coronary microvasculature (known as hyperemia). To obtain hyperemia, vasodilatory drugs are administered to reduce downward resistance to blood flow. Adenosine is the most frequently used vasodilator for this purpose in clinical practice [11; 12]. As the administration of adenosine requires intravascular injection (either an intracoronary bolus or an intravenous infusion) this requires additional time-consuming procedures. In addition, adenosine might be responsible for adverse effects, such as respiratory problems, a cutaneous rash, or transient bradycardia [13]. For these reasons, adenosine-free indices were developed as an alternative to simplify and to foster the spread of coronary pressure guidance during PCI [14]. Among adenosine-free indices, the instantaneous wave-Free Ratio (iFR) has shown a very high diagnostic agreement with FFR [15; 16; 17], with a similar performance in head-to-head studies on inducible ischemia against multiple comparators [18; 19]. As it does not require hyperemia (and thus adenosine administration), iFR has attracted physicians' attention since it can cut time and costs, as well as enhance patient comfort. The relationship between FFR and iFR has been verified in multiple studies [20; 21]. The diagnostic performance of iFR in the evaluation of the severity of coronary stenosis severity has been assessed against FFR, used as the standard of reference [22; 23; 24; 25]. iFR was tested in different clinical scenarios, including acute coronary syndromes and multivessel disease [22] and left main coronary artery disease, and its use in guiding PCI was recently validated in two large-scale clinical trials [26; 27]. The FFR-guided revascularization strategy has been proven to be more effective than the angiography -guided alternative. Here, we present the architecture and the use of a tool called JLabChart and report on the validation of the proposed tool by means of measurements and tests, proving the efficacy of the resulting measurements. The tool has been compared in terms of measurement values with real tests and synthetic vessels stenosis designed on the Comsol flow simulation commercial tool. The latter allows physicians to design vessels with known values and, thus, with known pressure values.