The Control of the Cardiovascular System in Health and Disease

Wednesday, June 16 at 02:15am (PDT)
Wednesday, June 16 at 10:15am (BST)
Wednesday, June 16 06:15pm (KST)

SMB2021 SMB2021 Follow Tuesday (Wednesday) during the "MS11" time block.
Note: this minisymposia has multiple sessions. The second session is MS12-NEUR (click here).

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Mette Olufsen (North Carolina State University, USA), Brian Carlson (University of Michigan, USA), Justen Geddes (North Carolina State University, USA)


The cardiovascular system delivers oxygen to all tissues in the body. The system is tightly controlled to supply oxygen under a diverse range of physiological conditions such as at rest, during postural changes, and exercise. Many studies have found that in a range of diseases, including COVID-19, cardiovascular function is compromised significantly impacting quality of life. The cardiovascular control system responds to mechanical, neural and hormonal stimuli and is difficult to study experimentally, as the system is best studied in the awake condition. Therefore, experimental measures e.g., heart rate, blood pressure, and respiration rate are typically non-invasive, and clinical invasive measures e.g., right heart catheterization, are only taken when the risk to the patient is minimal. A better understanding of how these non-invasive and low risk invasive measures can be used to quantitatively describe cardiovascular function is essential for improving diagnosis and treatment protocols. Numerous studies have used modeling to examine cardiovascular function and its control in animals and humans; however, more work is needed to translate these results to improve clinical protocols. This minisymposium focuses on exploring cardiovascular function - highlighting contributions that combine mathematical modeling, machine learning and signal processing.

Leszek Pstras

(Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland)
"Blood Volume Regulation During Hemodialysis"
Hemodialysis is the most common renal replacement therapy allowing for the removal of excess body water and waste products of metabolism in patients with chronic or acute kidney failure. Unfortunately, this life-sustaining treatment often puts a lot of strain on the cardiovascular system. During a typical dialysis session, a few liters of fluid are gradually removed from the blood flowing through the dialyzer, which usually leads to a progressive decrease in blood volume. The proper function of the cardiovascular system relies then on the microvascular absorption of fluid from tissues (the vascular refilling mechanism) and the activity of blood pressure regulatory mechanisms. In many dialysis patients, however, these mechanisms work insufficiently, leading to a drop in blood pressure and accompanying symptoms. Intradialytic hypotension is a multi-factorial and still not fully understood phenomenon and remains the major issue in dialysis units for both patients and staff. In this talk, a lumped-parameter mathematical model of the cardiovascular response to hemodialysis will be presented to discuss the cardiovascular regulatory mechanisms focusing on the mechanical aspects of blood volume regulation at the level of microcirculation.

Nikolai L. Bjørdalsbakke

(Norwegian University of Science and Technology, Trondheim, Norway)
"Is Non-Invasive Finger Pressure Informative About Cardiovascular Adaptation to Physical Activity Interventions?"
Non-invasive finger pressure is a simple and flexible method to continuously record blood pressure waves in various clinical settings; however, the waveform is substantially different from the central aortic blood pressure waveform, and further the systolic and diastolic values may differ from hypertension research's gold standard of 24 hour ambulatory brachial-cuff measured systolic and diastolic blood pressure. We present preliminary analysis of non-invasive finger pressure before and after physical activity intervention in pre-hypertensive and hypertensive adults. Additionally, we present the results of interpreting these blood pressure data through both mechanistic and data driven models as a means to quantify cardiovascular adaptations.

Justen Geddes

(North Carolina State University, Raleigh, NC, USA)
"Cardiovascular Regulation in POTS Patients"
Postural Orthostatic Tachycardia Syndrome (POTS) is characterized by an excessive increase in heart rate upon an upright postural change along with the presence of orthostatic symptoms possibly caused by an overactive baroreflex control system. The main contributor to heart-rate control is the baroreflex control system, a negative feedback system operating at a resonance frequency of ~0.1 Hz. Another sign that the control system is overactive is that POTS patients exhibit larger low-frequency (~0.1 Hz) heart rate and blood pressure oscillations than controls. In this talk we use signal processing to demonstrate the presence of 0.1 Hz oscillations and we build a cardiovascular systems model predicting baroreflex control of heart rate and blood pressure for controls and POTS patients. The cardiovascular model uses an RC electrical circuit analogy while the baroreflex control is modeled using first-order equations controlling heart rate, vascular resistance, and cardiac contractility ensuring saturation at high and low pressure. Our model is able to predict amplified low-frequency oscillations observed in POTS patient heart rate and blood pressure data both at rest and during head-up tilt, and we show how control changes for the various hypothesized causes of POTS known as endophenotypes.

Feng Gu

(University of Michigan, Ann Arbor, MI and Xiangya Hospital, Central South University, Changsha, Hunan, China, USA)
"Probing the Potential Role of Intermittent Functioning of Baroreflexes in the Etiology of Hypertension Using an Integrated Computational and Experimental Approach"
The potential role of the baroreflexes in long‐term arterial blood pressure (BP) regulation and in the etiology of primary hypertension have been long debated. To elucidate the potential mechanisms underlying the pathophysiology of primary hypertension, we analyzed dynamic baroreflex responses to spontaneous fluctuations in arterial pressure in the conscious spontaneously hypertensive rat (SHR), the most widely used genetic rat model of primary hypertension, as well as in the Wistar-Kyoto (WKY), the Dahl salt-sensitive, the Dahl salt-resistant, and the Sprague-Dawley rat. Observations revealed the existence of long intermittent periods (lasting up to several minutes) of continuous engagement and disengagement of baroreflex-mediated control of heart rate. Analysis of these intermittent periods reveals a predictive relationship between increased mean arterial pressure and progressive baroreflex disengagement that is present in the SHR and WKY strains but absent in others. To further investigate the mechanism underlying the intermittent baroreflexes engagement/disengagement, video was recorded during measurements of spontaneous dynamic baroreflex function in animals. Preliminary results indicate a positive correlation between baroreflex disengagement periods and activity levels. Measurements on human subjects reveal that, rather than the relationship between BP and progressive baroreflex disengagement observed in the rat models, baroreflex disengagement is more closely associated with arterial blood pH, suggesting a competitive interaction between baroreflex- and chemoreflex-mediated regulation of autonomic function. Based on these observations we hypothesize that chemoreflex-mediated sympathetic outflow can override baroreflex-derived parasympathetic outflow causing an apparent intermittent functioning of the baroreflex and potentially leading to hyper-sympathetic activity. We further hypothesize that in the SHR rat this intermittent chemoreflex-mediated override of the baroreflex contributes chronically elevated BP.

Hosted by SMB2021 Follow
Virtual conference of the Society for Mathematical Biology, 2021.