Energetics of Blood Flow in Cardiovascular Disease

Abstract

Visualization and quantification of the adverse effects of distorted blood flow are important emerging fields in cardiology. Abnormal blood flow patterns can be seen in various cardiovascular diseases and are associated with increased energy loss. These adverse energetics can be measured and quantified using 3-dimensional blood flow data, derived from computational fluid dynamics and 4-dimensional flow magnetic resonance imaging, and provide new, promising hemodynamic markers. In patients with palliated single-ventricular heart defects, the Fontan circulation passively directs systemic venous return to the pulmonary circulation in the absence of a functional subpulmonary ventricle. Therefore, the Fontan circulation is highly dependent on favorable flow and energetics, and minimal energy loss is of great importance. A focus on reducing energy loss led to the introduction of the total cavopulmonary connection (TCPC) as an alternative to the classical Fontan connection. Subsequently, many studies have investigated energy loss in the TCPC, and energy-saving geometric factors have been implemented in clinical care. Great advances have been made in computational fluid dynamics modeling and can now be done in 3-dimensional patient-specific models with increasingly accurate boundary conditions. Furthermore, the implementation of 4-dimensional flow magnetic resonance imaging is promising and can be of complementary value to these models. Recently, correlations between energy loss in the TCPC and cardiac parameters and exercise intolerance have been reported. Furthermore, efficiency of blood flow through the TCPC is highly variable, and inefficient blood flow is of clinical importance by reducing cardiac output and increasing central venous pressure, thereby increasing the risk of experiencing the well-known Fontan complications. Energy loss in the TCPC will be an important new hemodynamic parameter in addition to other well-known risk factors such as pulmonary vascular resistance and can possibly be improved by patient-specific surgical design. This article describes the theoretical background of mechanical energy of blood flow in the cardiovascular system and the methods of calculating energy loss, and it gives an overview of geometric factors associated with energy efficiency in the TCPC and its implications on clinical outcome. Furthermore, the role of 4-dimensional flow magnetic resonance imaging and areas of future research are discussed.

Wearable and Implantable Devices for Cardiovascular Healthcare: from Monitoring to Therapy Based on Flexible and Stretchable Electronics

“…Continuous measurement of blood flow also plays an important role in the diagnosis and characterization of cardiovascular health by providing microvascular and macrovascular flow information regarding kinetic energy along its course through the body. Abnormal blood flow patterns caused by abnormal geometry of vessels or valves induce unavoidable frictional loss of energy, hence it may ultimately result in heart failure . There are several principles to measure blood flow including mechanical, optical, acoustic, and thermal methods.…”

Energetics of blood flow in Fontan circulation under VAD support

“…At the same time, there is a high risk of the cardiovascular system to fail due to various reasons such as ventricular dysfunction, elevated pulmonary vascular impedance, inadequate preload to the ventricle, increased neurohumoral activation, and elevated systemic venous pressure . In order to increase the patients’ survival rate and the quality of their life, along with different TCPC connections oriented to improve blood hemodynamics, mechanical circulatory support (MCS) is applied as another auspicious treatment option …”

“…Techniques described in modern studies allow the analysis of the blood flow behavior and improvement of the geometry of the TCPC connection. It was shown that 3D and 4D blood flow data received from computational fluid dynamics (CFD) and magnetic resonance imaging can be used for measuring the adverse energetics . Whereas multi‐scale modeling can be used for the simulation of the hemodynamic effects of the Fontan circulation .…”

“…The Fontan procedure introduced in 1968 to treat patients with tricuspid atresia 1 currently is a standard and by far the best palliative treatment method for most patients with a functionally univentricular heart. 2,3 In order to form a connection typically known as "Total Cavopulmonary Connection" (TCPC) during the Fontan procedure, the caval veins are anastomosed to the pulmonary arteries. TCPC allows to support an acceptable level of pulmonary circulation 4 with reduction of the patients' morbidity and mortality.…”

“…It was shown that 3D and 4D blood flow data received from computational fluid dynamics (CFD) and magnetic resonance imaging can be used for measuring the adverse energetics. 3 Whereas multi-scale modeling can be used for the simulation of the hemodynamic effects of the Fontan circulation. 6 In theory, an optimal TCPC connection should decrease the loading level of a single ventricle and extend the life of the Fontan patients.…”