## 1 Introduction  
Trans-septal punctures are performed to gain access to the left atrium for several minimally invasive cardiac interventions such as mitral valve repair, left atrial appendage closure, and several left-sided cardiac ablations [1]. Moreover, measurement of left atrial pressure is an assessment of heart diseases. Although trans-septal access to the left side of the heart provides a very promising method for cardiologists, the maneuverability of the catheter remains challenging. Thus, making it difficult to access the desired location of the left atrium. Patent foramen ovale (PFO) is a common condition with probe patency in about 15-35% of the population [2]. It is involved in the etiology of several different pathologies including cryptogenic stroke and decompression sickness in divers. To analyze the concept of atrial septal defect (ASD) and PFO, the anatomical functional characteristic of the interatrial septum is of paramount importance. It not only assists device selection but also helps in the evaluation of the outcome of the trans-septal procedure [2]. The puncture is performed at the thinnest region of the interatrial septum known as the fossa ovalis (FO). A morphological study conducted in apparently 50 normal human hearts confirmed the probe patency and an oval shape of fossa ovalis. The measured transverse and vertical diameters of FO were 14.53 mm and 12.60 mm, respectively [2]. Fossa ovalis is the route for trans-septal access to the left atrium. A detailed study of the anatomy of fossa ovalis and surrounding landmarks plays a vital role in achieving a successful trans-septal procedure. FO is an oval or circular depression of the atrial septum located towards the right atrium above and to the left of the orifice of the inferior vena cava (IVC) [3]. Analysis of the clinical anatomy is essential for atrial septal defect, device selection, and overall success of the trans-septal procedure [4]. A schematic representation of FO and its surrounding landmarks is shown in Figure 1.  
A recent study on trans-septal procedures and the clinical relevance of FO presented similar data such as anteroposterior diameter of FO (14.5 mm), craniocandal diameter (12.6 mm), interatrial septum width (29.3 mm), PFO channel length (10.5 mm), and shape of FO: oval (86%) v circular (14%) [5]. Apart from morphology, this study also focused on imaging modalities such as fluoroscopy and intracardiac echocardiography, which play a vital role in the case of septal repair, PFO portal crossing, or when the anatomy of FO remains ambiguous [5]. A major complication in the trans-septal procedure is the iatrogenic atrial septal defect (iASD), which comes into effect due to the large size of sheaths that cross the septum. Other factors that contribute to the formation of iASD include long procedural times, high pulmonary pressures, and catheter manipulation [6]. A study conducted by [PERSON] et al. aimed to evaluate the initial collagen fiber orientation of soft tissues subjected to indentation testing. This was achieved using a collagen-based tissue-equivalent (TEs) model that helped to explore the structural and functional relationship [7]. Samples with both the isotropic and anisotropic fiber alignment were fabricated using the mold-grip system, where the samples can be secured uniaxially (rectangular mold) and biaxially (cruciform mold). This study subjected the Tes with  
Figure 1: Schematic representation of fossa ovalis and its surrounding landmarks; AO: aortic rim; CS: coronary sinus; EV: eustachian valve; FO: fossa ovalis; IAS: interatrial septum; IR: inferior rim; PR: posterior rim; RAA: right atrial appendage; RPA: right pulmonary artery; RPV: right pulmonary vein; SR: superior rim; SVC: superior vena cava; TV: tricuspid valve. either isotropic or highly anisotropic fiber alignment to stress-relaxation indentation tests with four-step increments.