Decision-based interactive model to determine re-opening conditions of a large university campus in Belgium during the first COVID-19 wave

Background

The role played by large-scale repetitive SARS-CoV-2 screening programs within university populations interacting continuously with an urban environment, is unknown. Our objective was to develop a model capable of predicting the dispersion of viral contamination among university populations dividing their time between social and academic environments.

Methods

Data was collected through real, large-scale testing developed at the University of Liège, Belgium, during the period Sept. 28th-Oct. 29th 2020. The screening, offered to students and staff (n = 30,000), began 2 weeks after the re-opening of the campus but had to be halted after 5 weeks due to an imposed general lockdown. The data was then used to feed a two-population model (University + surrounding environment) implementing a generalized susceptible-exposed-infected-removed compartmental modeling framework.

Results

The considered two-population model was sufficiently versatile to capture the known dynamics of the pandemic. The reproduction number was estimated to be significantly larger on campus than in the urban population, with a net difference of 0.5 in the most severe conditions. The low adhesion rate for screening (22.6% on average) and the large reproduction number meant the pandemic could not be contained. However, the weekly screening could have prevented 1393 cases (i.e. 4.6% of the university population; 95% CI: 4.4–4.8%) compared to a modeled situation without testing.

Conclusion

In a real life setting in a University campus, periodic screening could contribute to limiting the SARS-CoV-2 pandemic cycle but is highly dependent on its environment.

[Acute heart failure and acute pulmonary edema]

Acute heart failure is a common cause of admission in emergency department. Management requires rapid support when haemodynamic or respiratory parameters are altered. Identifying enabling factors and their specific treatment is an integral part of management. The most common clinical presentation is volume overload, whose treatment remains the combination of diuretics and vasodilators. In case of impaired perfusion, various inotropic supports may be considered, but also more and more circulatory assistance devices.

[Increased heart rate as a risk factor and treatment target in patients with heart failure]

Numerous epidemiological studies have shown that a high resting heart rate is associated with an increased cardiovascular morbidity and mortality, particularly in heart failure. The resting heart rate is not only a risk marker in heart failure, but it is also a risk factor, i.e., modifying heart rate also modifies the risk. Chronotropic drugs have shown benefits in terms of morbidity and mortality. Nevertheless, there is a major difference between the recommended heart rate and the patients’ everyday life heart rate. Indeed, even if the proportion of heart failure patients on beta-blockers is satisfactory, the number of patients with an optimal heart rate remains insufficient. The aim of this article is to examine the deleterious effect of an elevated resting heart rate in heart failure with systolic dysfunction, in order to overcome the therapeutic inertia and to improve the outcome in this patient group.

A fatal case of Perthes syndrome

Perthes syndrome, or traumatic asphyxia, is a clinical syndrome associating cervicofacial cyanosis with cutaneous petechial haemorrhages and subconjonctival bleeding resulting from severe sudden compressive chest trauma. Deep inspiration and a Valsalva maneuver just prior to rapid and severe chest compression, are responsible for the development of this syndrome. Current treatment is symptomatic: urgent relief of chest compression and cardiopulmonary resuscitation if needed. Outcome may be satisfactory depending on the duration and severity of compression. Prolonged thoracic compression may sometimes lead to cerebral anoxia, irreversible neurologic damage and death. We report a fatal case of Perthes syndrome resulting from an industrial accident.

Mathematical multi-scale model of the cardiovascular system including mitral valve dynamics. Application to ischemic mitral insufficiency

Background

Valve dysfunction is a common cardiovascular pathology. Despite significant clinical research, there is little formal study of how valve dysfunction affects overall circulatory dynamics. Validated models would offer the ability to better understand these dynamics and thus optimize diagnosis, as well as surgical and other interventions.

Methods

A cardiovascular and circulatory system (CVS) model has already been validated in silico, and in several animal model studies. It accounts for valve dynamics using Heaviside functions to simulate a physiologically accurate "open on pressure, close on flow" law. However, it does not consider real-time valve opening dynamics and therefore does not fully capture valve dysfunction, particularly where the dysfunction involves partial closure. This research describes an updated version of this previous closed-loop CVS model that includes the progressive opening of the mitral valve, and is defined over the full cardiac cycle.

Results

Simulations of the cardiovascular system with healthy mitral valve are performed, and, the global hemodynamic behaviour is studied compared with previously validated results. The error between resulting pressure-volume (PV) loops of already validated CVS model and the new CVS model that includes the progressive opening of the mitral valve is assessed and remains within typical measurement error and variability. Simulations of ischemic mitral insufficiency are also performed. Pressure-Volume loops, transmitral flow evolution and mitral valve aperture area evolution follow reported measurements in shape, amplitude and trends.

Conclusions

The resulting cardiovascular system model including mitral valve dynamics provides a foundation for clinical validation and the study of valvular dysfunction in vivo. The overall models and results could readily be generalised to other cardiac valves.

[Isolated spontaneous dissection of the superior mesenteric artery: a case report]

We report the case of a 38-year-old man admitted at the emergency department for abdominal pain of abrupt onset. Computed tomographic examination revealed a spontaneous isolated dissection of the superior mesenteric artery and an anevrysm of the coeliac artery caused by the arcuate ligament. Outcome was favorable under conservative medical treatment and a three months follow-up was uneventful. This observation offers the opportunity to present recent insights concerning this pathology.

Correction of pressure waveforms recorded by fluid-filled catheter recording systems: a new method using a transfer equation

BACKGROUND

Pressure measuring systems using fluid-filled catheters can result in the recording of distorted pressure waveforms. It results in phase delay, overestimation of systolic and, to a lesser extent, of diastolic pressure. We designed and evaluated a method to correct this pressure waveform distortion using an appropriate transfer equation obtained from the dynamic response of the fluid-filled catheter. This transfer equation is based on the principle that a fluid-filled catheter recording system is considered as an underdamped dynamic system fully characterized by its natural frequency (omega n) and damping ratio (zeta).

METHODS

Pressure waveforms, simultaneously recorded in vitro or in vivo by a fluid-filled catheter (Pc) and a micromanometer-tipped catheter (Pref), were used to validate the method. Dynamic response of the catheter used was obtained from a fastflush test. The corrected signal (Ppred) was obtained using omega n, zeta and the following transfer equation: d2Pc/dt2 + 2 omega n zeta dPc/dt + omega n 2Pc = C Ppred (t) After correction of Pc, Ppred was compared, using a linear regression, with Pref taken as reference.

RESULTS

Our results showed that Ppred was fitted to Pref with excellent coefficient correlation (0.99). The mean error and the standard error of estimate were respectively -1.16 mmHg and 1.4 mmHg.

CONCLUSION

This new method can convert the distorted pressure waveforms transmitted by any fluid-filled catheters into high-fidelity signals. It suppresses the phase delay and the over-estimation of systolic pressure induced by fluid-filled catheters.

Comparison of cardiac function in double-muscled calves and in calves with conventional muscular conformation

During growth, central venous, right ventricular, pulmonary arterial, pulmonary capillary wedge, and systemic arterial pressures, heart rate, and cardiac output were repeatedly measured in 41 Friesian calves, considered as having conventional muscular conformation, and in 19 Belgian White and Blue double-muscled calves. A total of 123 and 70 recordings were collected in conventional and double-muscled calves, respectively. These circulatory indices were calculated: stroke volume, cardiac and stroke indices, pulmonary and systemic pulse pressures, pulmonary and systemic vascular resistance indices, and right and left ventricular work indices. Results indicated that systemic arterial and pulse pressures, as well as cardiac output, stroke volume, cardiac and stroke indices, and right and left ventricular work indices were significantly (P < or = 0.05 to 0.001) lower but, in contrast, pulmonary and systemic vascular resistance indices were significantly (P < or = 0.001) higher in double-muscled than in conventional calves. Right-sided vascular pressures and heart rate were similar in the 2 groups. These results indicated that global cardiac performance may be considerably poorer in double-muscled calves. Diminished cardiac performance of double-muscled calves appears to be related neither to relative bradycardia nor to reduced ventricular preload. The potential role of increased ventricular afterload or of reduced myocardial contractility in double-muscled cattle should be determined by direct measurements.