Introduction: It has been extensively highlighted that SARS-CoV-2 affects the RAS (renin-angiotensin system) and the angiotensinconverting enzyme-2 receptors play the most important role in the presentation of the COVID-19 disease 2-5 The ACE2 is type I membrane protein expressed on endothelial cells in the kidney, heart, gastrointestinal tract, blood vessels, and, importantly, lung AT2 alveolar epithelial cells, which are particularly prone to SARS-CoV-2 infection As SARS-CoV-2 is a new coronavirus, and its cardiovascular complications and the underlying pathology is still emerging However, it is accepted that the virus affects the total vasculature in the human body and this infection becomes a highly accelerated process for the target organ damage In the case of acute cardiological manifestation, it is termed as Acute COVID-19 Cardiovascular Syndrome (ACovCS) by the American Heart Association's white paper 6 European Society of Cardiology (ESC) has published a detailed review paper 7 on the involvement of various cardiovascular target organs in COVID-19 disease This review clearly establishes a close two-way relationship between COVID-19 disease and all cardiovascular diseases (CVD) The prognosis is even worse in patients with preexisting cardiovascular system involvement Cardiovascular involvement in COVID-19 is seen as a key manifestation The best way to assess endothelial dysfunction is an assessment of its clinical manifestation, i e , an increase in arterial stiffness There have been multiple in vitro and in vivo studies that have shown that the vascular endothelium is an important factor in setting the vascular tone and endothelial dysfunction leads to arterial stiffness 8 Arterial stiffness and enhanced wave reflections are markers of cardiovascular disease and independent predictors of cardiovascular risk 9-12 Stiffening of the large arteries and enhanced wave reflections lead to increased left ventricular (LV) afterload, disturbed coronary perfusion, and mechanical fatigue of the arterial wall 13 The relationship between systemic inflammation and arterial stiffness is well established in the literature 14 The cause-and-effect relationship that acute systemic inflammation leads to deterioration of large-artery stiffness Findings in study15 on induced inflammation have shown that an acute inflammation caused a temporary increase in central blood pressure and arterial stiffness in terms of pulse wave velocity This implies the increased risk of cardiovascular events associated with acute systemic inflammation in the COVID-19 COVID-19 diseaserelated worldwide research and proposed mechanisms pointed to pathophysiological involvement of endothelial dysfunction and arterial wall compromise However, there was no empirical evidence of the functional compromise of arterial walls Hence, a study was urgently needed to study an increase in arterial stiffness in COVID-19 patients due to systemic inflammation to stratify the risk and mitigate further cardiovascular damage with guided therapeutic treatment based on the severity of arterial stiffness This pressing need is justified by a comprehensive review article16 published after the present study was envisaged We hope that the findings from our study will fulfill the need to a large extent Objectives: Primary objective: To study if the measurement of arterial stiffness using pulse wave velocity in mild-moderate and a severe group of COVID-19 patients can stratify cardiovascular risk Secondary objective: To determine if initial measurements and subsequent changes in arterial stiffness can project the future course of the COVID-19 patient and hence predict the grade of clinical management a confirmed COVID-19 patient would require Materials and methods: The present prospective nonrandomized observational study {titled - “To study the relationship of COVID-19 severity with arterial stiffness: A prospective cross-sectional study” (“COSEVAST study”)} was conducted in the COVID-19 ICU, medical ICU, and various wards of dedicated COVID hospital at AIIMS, Patna, Bihar, India The study protocol, informed consents, and other trial-related documents received the written approval of the Institutional Ethics Committee (IEC No AIIMS/Pat/IEC/2020/595) The study design was registered with the Clinical Trials Registry of India (CTRI No CTRI/2020/10/028489) All COVID-19 patients were subject to RT-PCR test and had a confirmed infection of the SARS-CoV-2 virus Participants, after understanding the study protocol and procedures, gave their written informed consent for the study The exclusion criteria were known history of any of these diseases - diabetes mellitus (DM), hypertension (HTN), CAD, stroke, neuropathy, PAD, nephropathy, MI, pregnancy, peripheral edema or inflammation, cardiac arrhythmia, and any preexisting cardiovascular disorder Patient categorization: The selected patients after fulfilling the inclusion criteria were grouped into three categories - mild, moderate, and severe category based on the latest NIH Guidelines 27 as follows: •Mild category: Individuals with mild signs and symptoms like fever, cough, sore throat, malaise, headache, muscle pain, nausea, vomiting, diarrhea, loss of taste and smell but who do not have shortness of breath, dyspnea, or abnormal chest imaging •Moderate category: Individuals who show evidence of lower respiratory disease during clinical assessment or imaging and who have a saturation of oxygen (SpO2) ≥ 94% on room air at sea level •Severe category: Individuals who have a saturation of oxygen (SpO2) 30 breaths/minute, PaO2/FiO2