Transient hemodynamic changes upon changing a BCPA into a TCPC in staged Fontan operation: a computational model study

Deep-learning-based real-time individualization for reduce-order haemodynamic model

The reduced-order lumped parameter model (LPM) has great computational efficiency in real-time numerical simulations of haemodynamics but is limited by the accuracy of patient-specific computation. This study proposed a method to achieve the individual LPM modeling with high accuracy to improve the practical clinical applicability of LPM. Clinical data was collected from two medical centres comprising haemodynamic indicators from 323 individuals, including brachial artery pressure waveforms, cardiac output data, and internal carotid artery flow waveforms. The data were expanded to 5000 synthesised cases that all fell within the physiological range of each indicator. LPM of the human blood circulation system was established. A double-path neural network (DPNN) was designed to input the waveforms of each haemodynamic indicator and their key features and then output the individual parameters of the LPM, which was labelled using a conventional optimization algorithm. Clinically collected data from the other 100 cases were used as the test set to verify the accuracy of the individual LPM parameters predicted by DPNN. The results show that DPNN provided good convergence in the training process. In the test set, compared with clinical measurements, the mean differences between each haemodynamic indicator and the estimate calculated by the individual LPM based on the DPNN were about 10 %. Furthermore, DPNN prediction only takes 4 s for 100 cases. The DPNN proposed in this study permits real-time and accurate individualization of LPM's. When facing medical issues involving haemodynamics, it lays the foundation for patient-specific numerical simulation, which may be beneficial for potential clinical application.

Impact of Respiratory Fluctuation on Hemodynamics in Human Cardiovascular System: A 0-1D Multiscale Model

To explore hemodynamic interaction between the human respiratory system (RS) and cardiovascular system (CVS), here we propose an integrated computational model to predict the CVS hemodynamics with consideration of the respiratory fluctuation (RF). A submodule of the intrathoracic pressure (ITP) adjustment is developed and incorporated in a 0-1D multiscale hemodynamic model of the CVS specified for infant, adolescent, and adult individuals. The model is verified to enable reasonable estimation of the blood pressure waveforms accounting for the RF-induced pressure fluctuations in comparison with clinical data. The results show that the negative ITP caused by respiration increases the blood flow rates in superior and inferior vena cavae; the deep breathing improves the venous return in adolescents but has less influence on infants. It is found that a marked reduction in ITP under pathological conditions can excessively increase the flow rates in cavae independent of the individual ages, which may cause the hemodynamic instability and hence increase the risk of heart failure. Our results indicate that the present 0-1D multiscale CVS model incorporated with the RF effect is capable of providing a useful and effective tool to explore the physiological and pathological mechanisms in association with cardiopulmonary interactions and their clinical applications.

Balloon Deflation Strategy during Primary Percutaneous Coronary Intervention in Acute ST-Segment Elevation Myocardial Infarction: A Randomized Controlled Clinical Trial and Numerical Simulation-Based Analysis

Background

Primary percutaneous coronary intervention (PCI) is the best available reperfusion strategy in patients with acute ST-segment elevation myocardial infarction (STEMI). However, PCI is associated with a serious problem known as no-reflow phenomenon, resulting in poor clinical and functional outcomes. This study aimed to compare the influences of different balloon deflation velocity on coronary flow and cardiovascular events during primary PCI in STEM as well as transient hemodynamic changes in in vitro experiments. Method and Results. 211 STEMI patients were randomly assigned to either a rapid or a slow balloon deflation group during stent deployment. The primary end point was coronary flow at the end of PCI procedure, and secondary end points included myocardial infarct size. Transient hemodynamic changes were evaluated through an in vitro experimental apparatus and a computer model. In clinical practice, the level of corrected TIMI frame count (cTFC) in slow balloon deflation after primary PCI was significantly lower than that of rapid balloon deflation, which was associated with smaller infarct size. Numerical simulations revealed that the rapid deflation led to a sharp acceleration of flow in the balloon-vessel gap and a concomitant abnormal rise in wall shear stress (WSS).

Conclusion

This randomized study demonstrated that the slow balloon deflation during stent implantation improved coronary flow and reduced infarct size in reperfused STEMI. The change of flow in the balloon-vessel gap and WSS resulted from different balloon deflation velocity might be partly accounted for this results.

Lessons Learned From a Critical Analysis of the Fontan Operation Over Three Decades in a Single Institution

Background:

The Fontan operation (FO) has evolved and many centers have demonstrated improved results relative to those from earlier eras. We report a single-institution experience over three decades, describing the outcomes and evaluating risk factors.

Methods:

Successive patients undergoing primary FO were divided into era I (1984-1994), era II (1995-2004), and era III (2005-2014). Clinical and operative notes were reviewed for demographic, anatomic, and procedure details. End points included early and late mortality and a composite of death, heart transplantation (HTX), or Fontan takedown.

Results:

A total of 420 patients underwent 18 atriopulmonary connections, 82 lateral tunnels (LT), and 320 extracardiac conduit (EC) Fontan procedures. Forty-six (11%) patients died; early and late mortality were 7.9% and 3.1%, respectively. Eight (1.9%) patients underwent HTX, 11 (2.6%) underwent Fontan conversion to EC, and 1 (0.2%) takedown of EC to bidirectional Glenn shunt. Prevalence of concomitant valve surgery ( P < .001) and pulmonary artery reconstruction ( P < .001) differed over the eras. Preoperative valve regurgitation was associated with likelihood of early mortality (odds ratio [OR] = 3.5, P = .002). Embolic events (OR = 1.9, P = .047), preoperative valve regurgitation (OR = 2.3, P = .029), diagnosis of unbalanced atrioventricular canal defect (OR = 1.14, P = .03), and concomitant valve replacement (OR = 6.9, P = .001) during the FO were associated with increased risk of the composite end point (death, HTX, or takedown).

Conclusion:

Technical modifications did not result in improved results across eras, due in part to more liberal indications for surgery in the recent years. Valve regurgitation, unbalanced atrioventricular canal, embolic events, or concomitant valve replacement were associated with FO failure.

Simulation of one-dimensional blood flow in networks of human vessels using a novel TVD scheme

An extension of a total variation diminishing (TVD) scheme to solve one-dimensional (1D) blood flow for human circulation is proposed. This method is simple as it involves only a few modifications to existing shock-capturing TVD schemes. We have applied the method to a wide range of test cases including a complete simulation of the human vascular network. Excellent solutions have been demonstrated for problems involving varying and discontinuous mechanical properties of blood vessels. For 1D network simulations, the method has been shown to agree well with the reported computational results. Finally, the method has been demonstrated to compare favorably with in vivo experiments set up to study the impact of circle of Willis anomalies on flow patterns in the cerebral arterial system.