Clinical features of post-COVID-19 period. Results of the international register “Dynamic analysis of comorbidities in SARS-CoV-2 survivors (AKTIV SARS-CoV-2)”. Data from 6-month follow-up

Aim. To study the clinical course specifics of coronavirus disease 2019 (COVID-19) and comorbid conditions in COVID-19 survivors 3, 6, 12 months after recovery in the Eurasian region according to the AKTIV register. Material and methods.The AKTIV register was created at the initiative of the Eurasian Association of Therapists. The AKTIV register is divided into 2 parts: AKTIV 1 and AKTIV 2. The AKTIV 1 register currently includes 6300 patients, while in AKTIV 2 — 2770. Patients diagnosed with COVID-19 receiving in- and outpatient treatment have been anonymously included on the registry. The following 7 countries participated in the register: Russian Federation, Republic of Armenia, Republic of Belarus, Republic of Kazakhstan, Kyrgyz Republic, Republic of Moldova, Republic of Uzbekistan. This closed multicenter register with two nonoverlapping branches (in- and outpatient branch) provides 6 visits: 3 in-person visits during the acute period and 3 telephone calls after 3, 6, 12 months. Subject recruitment lasted from June 29, 2020 to October 29, 2020. Register will end on October 29, 2022. A total of 9 fragmentary analyzes of the registry data are planned. This fragment of the study presents the results of the post-hospitalization period in COVID-19 survivors after 3 and 6 months. Results. According to the AKTIV register, patients after COVID-19 are characterized by long-term persistent symptoms and frequent seeking for unscheduled medical care, including rehospitalizations. The most common causes of unplanned medical care are uncontrolled hypertension (HTN) and chronic coronary artery disease (CAD) and/or decompensated type 2 diabetes (T2D). During 3- and 6-month follow-up after hospitalization, 5,6% and 6,4% of patients were diagnosed with other diseases, which were more often presented by HTN, T2D, and CAD. The mortality rate of patients in the post-hospitalization period was 1,9% in the first 3 months and 0,2% for 4-6 months. The highest mortality rate was observed in the first 3 months in the group of patients with class II-IV heart failure, as well as in patients with cardiovascular diseases and cancer. In the pattern of death causes in the post-hospitalization period, following cardiovascular causes prevailed (31,8%): acute coronary syndrome, stroke, acute heart failure. Conclusion. According to the AKTIV register, the health status of patients after COVID-19 in a serious challenge for healthcare system, which requires planning adequate health system capacity to provide care to patients with COVID-19 in both acute and post-hospitalization period

PROCESS OSCILLATIVITY STUDY IN APERIODIC CONTINUOUS SYSTEMS, GENERATED BY EIGENVALUES MULTIPLICATION FACTOR

The article deals with the steady aperiodic continuous system with state matrix obtaining the spectrum of multiple eigenvalues which multiplicity is equal to dimension of its state vector. It is shown that if the eigenvalue magnitude is less than unity, in system free transient motion on norm of state vector the oscillativity is found which becomes apparent by initial overshoot, being replaced by monotonous movement to quiescent state. It is established that the less eigenvalue modulo and the more its multiplicity, the more overshoot size

PROXIMITY DEGREE FOR SIMPLE AND MULTIPLE STRUCTURES OF THE EIGENVALUES: OVERSHOOT MINIMIZATION FOR FREE MOTION TRAJECTORIES OF APERIODIC SYSTEM

The paper deals with steady aperiodic continuous system, state matrix of which has a real spectrum of the eigenvalues which absolute value is less than unity. The latest authors’ works show that for such absolute values and multiple structure of eigenvalues on the free motion trajectories of the system by norm of the state vector the significant overshoot is detected, alternated by monotonous motion toward a state of rest. In order to minimize the overshoot value, it is proposed to modify the structure of the eigenvalues, transforming it into a simple one. The result of structure modification is the following: initial eigenvalue and shifted along the real axis of the complex plane to the left by a fixed value relative to the adjacent eigenvalues; each of them has unit multiplicity. Such modification gives the possibility to form the estimation of the proximity degree of eigenvalues simple structure to the multiple one. Moreover, it can be defined in a relative form, which guarantees the reduction of the above overshoot for the free motion trajectory. Results of computer experiments illustrate the issues of the paper

Large deviations in linear control systems with nonzero initial conditions

Research in the transient response in linear systems with nonzero initial conditions was initiated by A.A. Feldbaum in his pioneering work [1] as early as in 1948. However later, studies in this direction have faded down, and since then, the notion of transient process basically means the response of the system with zero initial conditions to the unit step input. A breakthrough in this direction is associated with the paper [2] by R.N. Izmailov, where large deviations of the trajectories from the origin were shown to be unavoidable if the poles of the closed-loop system are shifted far to the left in the complex plane. In this paper we continue the analysis of this phenomenon for systems with nonzero initial conditions. Namely, we propose a more accurate estimate of the magnitude of the peak and show that the effect of large deviations may be observed for different root locations. We also present an upper bound on deviations by using the linear matrix inequality (LMI) technique. This same approach is then applied to the design of a stabilizing linear feedback aimed at diminishing deviations in the closed-loop system. Related problems are also discussed, e.g., such as analysis of the transient response of systems with zero initial conditions and exogenous disturbances in the form of either unit step function or harmonic signal.This work was supported in part by the Mega-Grant of the Russian Federation, project no. 14.Z50.31.0031, the Russian Foundation for Basic Research, projects nos. 14-07-00067-a and 14-08-01230-a, and Portugal grants FCT, COMPETE, QREN, FEDER, project VARIANT (PTDC/MAT/111809/2009)

International register “Dynamics analysis of comorbidities in SARS-CoV-2 survivors” (AKTIV SARS-CoV-2): analysis of 1,000 patients

COVID-19 is a severe infection with high mortality. The concept of the disease has been shaped to a greater extent on the basis of large registers from the USA, Spain, Italy, and China. However, there is no information on the disease characteristics in Caucasian patients.Therefore, we created an international register with the estimated capacity of 5,000 patients — Dynamics Analysis of Comorbidities in SARS-CoV-2 Survivors (AKTIV SARS-CoV-2), which brought together professionals from the Russian Federation, Republic of Armenia, Republic of Kazakhstan, and Kyrgyz Republic. The article presents the first analysis of the register involving 1,003 patients. It was shown that the most significant difference of the Caucasian population was the higher effect of multimorbidity on the mortality risk vs other registers. More pronounced effect on mortality of such diseases as diabetes, obesity, hypertension, chronic kidney disease, and age over 60 years was also revealed