Using a Mock Circulatory Loop as a Regulatory Science Tool to Simulate Different Heart Failure Conditions

Mechanical circulatory support (MCS) device therapy is one of the primary treatment options for end-stage heart failure (HF), whereby a mechanical pump is integrated with the failing heart to maintain adequate tissue perfusion. The ISO 14708-5:2020 standard prescribes generic guidelines for nonclinical device evaluation and system performance testing of MCS devices using a mock circulatory loop (MCL). However, the utility of MCLs in premarket regulatory submissions of MCS devices is ambiguous, and the specific disease states that the device is intended to treat are not usually simulated. Hence, we aim to outline the potential of MCLs as a valuable regulatory science tool for characterizing MCS device systems by adequately representing target clinical-use HF conditions on the bench. Target pathophysiologic hemodynamics of HF conditions (i.e., cardiogenic shock (CS), left ventricular (LV) hypertrophy secondary to hypertension, and coronary artery disease), along with a healthy adult at rest and a healthy adult during exercise are provided as recommended test conditions. The conditions are characterized based on LV, aorta, and left atrium pressures using recommended cardiac hemodynamic indices such as systolic, diastolic, and mean arterial pressure, mean cardiac output (CO), cardiac cycle time, and systemic vascular resistance. This study is a first step toward standardizing MCLs to generate well-defined target HF conditions used to evaluate MCS devices.

Latest Developments in Adapting Deep Learning for Assessing TAVR Procedures and Outcomes

Aortic valve defects are among the most prevalent clinical conditions. A severely damaged or non-functioning aortic valve is commonly replaced with a bioprosthetic heart valve (BHV) via the transcatheter aortic valve replacement (TAVR) procedure. Accurate pre-operative planning is crucial for a successful TAVR outcome. Assessment of computational fluid dynamics (CFD), finite element analysis (FEA), and fluid-solid interaction (FSI) analysis offer a solution that has been increasingly utilized to evaluate BHV mechanics and dynamics. However, the high computational costs and the complex operation of computational modeling hinder its application. Recent advancements in the deep learning (DL) domain can offer a real-time surrogate that can render hemodynamic parameters in a few seconds, thus guiding clinicians to select the optimal treatment option. Herein, we provide a comprehensive review of classical computational modeling approaches, medical imaging, and DL approaches for planning and outcome assessment of TAVR. Particularly, we focus on DL approaches in previous studies, highlighting the utilized datasets, deployed DL models, and achieved results. We emphasize the critical challenges and recommend several future directions for innovative researchers to tackle. Finally, an end-to-end smart DL framework is outlined for real-time assessment and recommendation of the best BHV design for TAVR. Ultimately, deploying such a framework in future studies will support clinicians in minimizing risks during TAVR therapy planning and will help in improving patient care.

Evaluation of the effects of gabapentin on the physiologic and echocardiographic variables of healthy cats: a prospective, randomized and blinded study

OBJECTIVES

The aim of this study was to evaluate, using echocardiography, the effects of oral administration of a single dose of gabapentin on the physiologic variables (heart rate [HR], respiratory rate [RR] and systolic blood pressure [SBP]) and systolic and diastolic cardiac function of healthy cats.

METHODS

This was a prospective, randomized and blinded study with 40 healthy cats aged between 6 months and 2 years. The cats' health status was assessed on the first appointment (T1) when they underwent a physical examination, complete blood count, biochemical profile, assessment of physiologic variables and echocardiogram. The echocardiogram was used to measure the left ventricle's (LV) internal diameter during systole and diastole, isovolumic relaxation time, transmitral flow, E-wave deceleration time and HR. The cats were randomly divided into two groups: (1) a treatment group with 20 cats that received a single oral dose of gabapentin (100 mg/cat); and (2) a control group with 20 cats that received a single oral dose of placebo. All variables of the physiologic and echocardiographic variables were re-evaluated 1-3 weeks after T1 (T2), 90 mins after medication or placebo administration.

RESULTS

There was no difference in the physiologic variables evaluated in both groups. The proportion of cats in the treatment group that had their ventricular filling waves fused on T1 but did not have them fused on T2 was significantly higher (45%) compared with cats in the control group (15%; P = 0.0384).

CONCLUSIONS AND RELEVANCE

There was no difference between the groups in regard to SBP, HR, RR and echocardiographic variables. Gabapentin improved evaluation of diastolic function on echocardiogram because it reduced the fusion of ventricular filling waves during the evaluation of the diastolic function of the LV. Gabapentin did not cause adverse effects on the cardiovascular hemodynamics of young healthy cats.

Comparison of Three-Month HIIT and CMT Effects on Left Ventricle Echocardiography Observations in Male Employees

The present study aimed to identify changes in echocardiographic parameters before and after three-month high-intensity interval training (HIIT) and continuous moderate-intensity training (CMT) in male employees. For this purpose, using a convenience sampling method, 33 male employees of the Islamic Republic of Iran Army (office workers with a sedentary lifestyle) aged 30 through 40 were selected. Participants were divided into three groups of HIIT, CMT, and control (11 for each group) including all anthropometric data (body fat percentage, body mass index, height, weight, and VO2 max) with no history of chronic diseases, metabolic syndrome, confirmed heart disease or congenital heart defect, and hospitalization due to chronic diseases or consumption of medication affecting cardiovascular indicators. A one-way ANOVA was conducted to compare the groups. The results demonstrated that the end-systolic volumes (ESVs) (p < 0.01) and relative wall thickness (RWT) in the CMT group (p < 0.01) and the end-diastolic volumes (EDVs) (p < 0.01), stroke volumes (SVs) (p < 0.01), end-systolic and diastolic diameters (ESD, EDD) (p < 0.01), as well as the RWT and left ventricle diastolic function (E/A ratio) in the HIIT group (p < 0.05) were significantly different before and after the 12-week training (Bonferroni correction was used for pairwise comparisons). The results revealed a significant increase in the end-systolic diameters (ESDs) of the HIIT group, whereas no such increase was observed in the ESDs of the CMT group (p < 0.51). Moreover, a significant increase was observed in left ventricular (LV) RWT and aerobic power of both training groups. The significant decrease of ESVs and the significant increase in E/A ratio, ESDs, EDDs following HIIT (two to three sessions per week) may indicate beneficial and optimal LV structural adaptations and improved LV function in nonathletes (even with a sedentary lifestyle).

A method of parameter estimation for cardiovascular hemodynamics based on deep learning and its application to personalize a reduced-order model

Precise model personalization is a key step towards the application of cardiovascular physical models. In this manuscript, we propose to use deep learning (DL) to solve the parameter estimation problem in cardiovascular hemodynamics. Based on the convolutional neural network (CNN) and fully connected neural network (FCNN), a multi-input deep neural network (DNN) model is developed to map the nonlinear relationship between measurements and the parameters to be estimated. In this model, two separate network structures are designed to extract the features of two types of measurement data, including pressure waveforms and a vector composed of heart rate (HR) and pulse transit time (PTT), and a shared structure is used to extract their combined dependencies on the parameters. Besides, we try to use the transfer learning (TL) technology to further strengthen the personalized characteristics of a trained-well network. For assessing the proposed method, we conducted the parameter estimation using synthetic data and in vitro data respectively, and in the test with synthetic data, we evaluated the performance of the TL algorithm through two individuals with different characteristics. A series of estimation results show that the estimated parameters are in good agreement with the true values. Furthermore, it is also found that the estimation accuracy can be significantly improved by a multicycle combination strategy. Therefore, we think that the proposed method has the potential to be used for parameter estimation in cardiovascular hemodynamics, which can provide an immediate, accurate, and sustainable personalization process, and deserves more attention in the future.

Cardiovascular Diseases in Pregnancy - A Brief Overview

Even though, there have been many advances in maternal medical care and fertility treatments, the presence of cardiovascular disease has a significant impact on pregnancy. In pregnant women, several heart conditions, such as valvular heart disease, chronic hypertension, congenital heart defects and non-ischemic cardiomyopathies are linked to increased risk of fetal as well as maternal morbidity and mortality. To date, the management of the co-existing conditions of pregnancy and heart disease has been challenging. Therefore, in-depth information may be beneficial to tackle a difficult case scenario. Towards this end, this paper provides an overview of the recent updated knowledge of pregnancy-related cardiovascular diseases in women.

Use of Ballistocardiography to Monitor Cardiovascular Hemodynamics in Preeclampsia

Objective: Pregnancy requires a complex physiological adaptation of the maternal cardiovascular system, which is disrupted in women with pregnancies complicated by preeclampsia, putting them at higher risk of future cardiovascular events. The measurement of body movements in response to cardiac ejection via ballistocardiogram (BCG) can be used to assess cardiovascular hemodynamics noninvasively in women with preeclampsia.

Methods: Using a previously validated, modified weighing scale for assessment of cardiovascular hemodynamics through measurement of BCG and electrocardiogram (ECG) signals, we collected serial measurements throughout pregnancy and postpartum and analyzed data in 30 women with preeclampsia and 23 normotensive controls. Using BCG and ECG signals, we extracted measures of cardiac output, J-wave amplitude × heart rate (J-amp × HR). Mixed-effect models with repeated measures were used to compare J-amp × HRs between groups at different time points in pregnancy and postpartum.

Results: In normotensive controls, the J-amp × HR was significantly lower early postpartum (E-PP) compared with the second trimester (T2; p = 0.016) and third trimester (T3; p = 0.001). Women with preeclampsia had a significantly lower J-amp × HR compared with normotensive controls during the first trimester (T1; p = 0.026). In the preeclampsia group, there was a trend toward an increase in J-amp × HR from T1 to T2 and then a drop in J-amp × HR at T3 and further drop at E-PP.

Conclusions: We observe cardiac hemodynamic changes consistent with those reported using well-validated tools. In pregnancies complicated by preeclampsia, the maximal force of contraction is lower, suggesting lower cardiac output and a trend in hemodynamics consistent with the hyperdynamic disease model of preeclampsia.

Demonstration of Patient-Specific Simulations to Assess Left Atrial Appendage Thrombogenesis Risk

Atrial fibrillation (AF) alters left atrial (LA) hemodynamics, which can lead to thrombosis in the left atrial appendage (LAA), systemic embolism and stroke. A personalized risk-stratification of AF patients for stroke would permit improved balancing of preventive anticoagulation therapies against bleeding risk. We investigated how LA anatomy and function impact LA and LAA hemodynamics, and explored whether patient-specific analysis by computational fluid dynamics (CFD) can predict the risk of LAA thrombosis. We analyzed 4D-CT acquisitions of LA wall motion with an in-house immersed-boundary CFD solver. We considered six patients with diverse atrial function, three with either a LAA thrombus (removed digitally before running the simulations) or a history of transient ischemic attacks (LAAT/TIA-pos), and three without a LAA thrombus or TIA (LAAT/TIA-neg). We found that blood inside the left atrial appendage of LAAT/TIA-pos patients had marked alterations in residence time and kinetic energy when compared with LAAT/TIA-neg patients. In addition, we showed how the LA conduit, reservoir and booster functions distinctly affect LA and LAA hemodynamics. Finally, fixed-wall and moving-wall simulations produced different LA hemodynamics and residence time predictions for each patient. Consequently, fixed-wall simulations risk-stratified our small cohort for LAA thrombosis worse than moving-wall simulations, particularly patients with intermediate LAA residence time. Overall, these results suggest that both wall kinetics and LAA morphology contribute to LAA blood stasis and thrombosis.

Practical Use of Regularization in Individualizing a Mathematical Model of Cardiovascular Hemodynamics Using Scarce Data

Individualizing physiological models to a patient can enable patient-specific monitoring and treatment in critical care environments. However, this task often presents a unique "practical identifiability" challenge due to the conflict between model complexity and data scarcity. Regularization provides an established framework to cope with this conflict by compensating for data scarcity with prior knowledge. However, regularization has not been widely pursued in individualizing physiological models to facilitate patient-specific critical care. Thus, the goal of this work is to garner potentially generalizable insight into the practical use of regularization in individualizing a complex physiological model using scarce data by investigating its effect in a clinically significant critical care case study of blood volume kinetics and cardiovascular hemodynamics in hemorrhage and circulatory resuscitation. We construct a population-average model as prior knowledge and individualize the physiological model via regularization to illustrate that regularization can be effective in individualizing a physiological model to learn salient individual-specific characteristics (resulting in the goodness of fit to individual-specific data) while restricting unnecessary deviations from the population-average model (achieving practical identifiability). We also illustrate that regularization yields parsimonious individualization of only sensitive parameters as well as adequate physiological plausibility and relevance in predicting internal physiological states.

Optimization of combined measures of airway physiology and cardiovascular hemodynamics in mice

Pulmonary hypertension may arise as a complication of chronic lung disease typically associated with tissue hypoxia, as well as infectious agents or injury eliciting a type 2 immune response. The onset of pulmonary hypertension in this setting (classified as Group 3) often complicates treatment and worsens prognosis of chronic lung disease. Chronic lung diseases such as chronic obstructive lung disease (COPD), emphysema, and interstitial lung fibrosis impair airflow and alter lung elastance in addition to affecting pulmonary vascular hemodynamics that may culminate in right ventricle dysfunction. To date, functional endpoints in murine models of chronic lung disease have typically been limited to separately measuring airway and lung parenchyma physiology. These approaches may be lengthy and require a large number of animals per experiment. Here, we provide a detailed protocol for combined assessment of airway physiology with cardiovascular hemodynamics in mice. Ultimately, a comprehensive overview of pulmonary function in murine models of injury and disease will facilitate the integration of studies of the airway and vascular biology necessary to understand underlying pathophysiology of Group 3 pulmonary hypertension.

Healthy Aging and Cardiovascular Function: Invasive Hemodynamics During Rest and Exercise in 104 Healthy Volunteers

OBJECTIVES

The aim of this study was to evaluate the association between age and invasive cardiovascular hemodynamics during upright exercise among healthy adults.

BACKGROUND

The marked age-related decline in maximal exercise oxygen uptake (peak VO₂) may contribute to the high burden of heart failure among older individuals and their greater severity of exertional symptoms. However, the mechanisms underlying this decline are not well understood.

METHODS

A total of 104 healthy community-dwelling volunteers age 20 to 76 years well screened for cardiovascular disease underwent exhaustive upright exercise with brachial and pulmonary artery catheters; radionuclide ventriculography; and expired gas analysis for the measurement of peak VO₂, cardiac output, left ventricular stroke volume, end-diastolic volume, end-systolic volume, ejection fraction, pulmonary capillary wedge pressure, and arteriovenous oxygen difference.

RESULTS

Over a 5.5-decade age range, there was a 40% decline in peak VO₂ due primarily to reduced peak exercise cardiac output; peak arteriovenous oxygen difference was unaffected by age. The lower age-related exercise cardiac output was related to lower peak exercise heart rate and stroke volume. Aging was also associated with lower peak exercise ejection fraction, indicating reduced inotropic reserve. Peak exercise end-diastolic volume was lower with aging despite similar left ventricular filling pressure, suggesting age-related reduced diastolic compliance limiting the use of the Frank-Starling mechanism to compensate for reduced chronotropic and inotropic reserves. These age relationships were unaffected by sex.

CONCLUSIONS

The age-related decline in exercise capacity among healthy persons is due predominantly to cardiac mechanisms, including reduced chronotropic and inotropic reserve and possibly reduced Frank-Starling reserve. Peak exercise left ventricular filling pressure and arteriovenous oxygen difference are unchanged with healthy aging.

Maternal hemodynamics: a method to classify hypertensive disorders of pregnancy

BACKGROUND

The classification of hypertensive disorders of pregnancy is based on the time at the onset of hypertension, proteinuria, and other associated complications. Maternal hemodynamic interrogation in hypertensive disorders of pregnancy considers not only the peripheral blood pressure but also the entire cardiovascular system, and it might help to classify the different clinical phenotypes of this syndrome.

OBJECTIVE

This study aimed to examine cardiovascular parameters in a cohort of patients affected by hypertensive disorders of pregnancy according to the clinical phenotypes that prioritize fetoplacental characteristics and not the time at onset of hypertensive disorders of pregnancy.

STUDY DESIGN

At the fetal-maternal medicine unit of Ziekenhuis Oost-Limburg (Genk, Belgium), maternal cardiovascular parameters were obtained through impedance cardiography using a noninvasive continuous cardiac output monitor with the patients placed in a standing position. The patients were classified as pregnant women with hypertensive disorders of pregnancy who delivered appropriate- and small-for-gestational-age fetuses. Normotensive pregnant women with an appropriate-for-gestational-age fetus at delivery were enrolled as the control group. The possible impact of obesity (body mass index ≥30 kg/m²) on maternal hemodynamics was reassessed in the same groups.

RESULTS

Maternal age, parity, body mass index, and blood pressure were not significantly different between the hypertensive disorders of pregnancy/appropriate-for-gestational-age and hypertensive disorders of pregnancy/small-for-gestational-age groups. The mean uterine artery pulsatility index was significantly higher in the hypertensive disorders of pregnancy/small-for-gestational-age group. The cardiac output and cardiac index were significantly lower in the hypertensive disorders of pregnancy/small-for-gestational-age group (cardiac output 6.5 L/min, cardiac index 3.6) than in the hypertensive disorders of pregnancy/appropriate-for-gestational-age group (cardiac output 7.6 L/min, cardiac index 3.9) but not between the hypertensive disorders of pregnancy/appropriate-for-gestational-age and control groups (cardiac output 7.6 L/min, cardiac index 4.0). Total vascular resistance was significantly higher in the hypertensive disorders of pregnancy/small-for-gestational-age group than in the hypertensive disorders of pregnancy/appropriate-for-gestational-age group and the control group. All women with hypertensive disorders of pregnancy showed signs of central arterial dysfunction. The cardiovascular parameters were not influenced by gestational age at the onset of hypertensive disorders of pregnancy, and no difference was observed between the women with appropriate-for-gestational-age fetuses affected by preeclampsia or by gestational hypertension with appropriate-for-gestational-age fetuses. Women in the obese/hypertensive disorders of pregnancy/appropriate-for-gestational-age and obese/hypertensive disorders of pregnancy/small-for-gestational-age groups showed a significant increase in cardiac output, as well as significant changes in other parameters, compared with the nonobese/hypertensive disorders of pregnancy/appropriate-for-gestational-age and nonobese/hypertensive disorders of pregnancy/small-for-gestational-age groups.

CONCLUSION

Significantly low cardiac output and high total vascular resistance characterized the women with hypertensive disorders of pregnancy associated with small for gestational age due to placental insufficiency, independent of the gestational age at the onset of hypertension. The cardiovascular parameters were not significantly different in the women with appropriate-for-gestational-age or small-for-gestational-age fetuses affected by preeclampsia or gestational hypertension. These findings support the view that maternal hemodynamics may be a candidate diagnostic tool to identify hypertensive disorders in pregnancies associated with small-for-gestational-age fetuses. This additional tool matches other reported evidence provided by uterine Doppler velocimetry, low vascular growth factors in the first trimester, and placental pathology. Obesity is associated with a significantly higher cardiac output and outweighs other determinants of hemodynamics in pregnancy; therefore, in future studies on hypertensive disorders, obesity should be studied as an additional disease and not simply as a demographic characteristic.

Model-Based Comparison of the Normal and Fontan Circulatory Systems-Part III

BACKGROUND

For patients with the Fontan circulatory arrangement, angiotensin-converting enzyme inhibition, guanylate cyclase activation, phosphodiesterase 5 inhibition, and endothelin receptor antagonism have so far resulted in little or no improvement in [Formula: see text] or peak cardiac index (CI), suggesting that our understanding of the factors that most impact the exercise hemodynamics is incomplete.

METHODS

To facilitate comparisons with clinical reports of the exercise performance of preadolescent Fontan patients, we rescaled our previously reported computational models of a two-year-old normal child and similarly aged Fontan patient, extended our Fontan model to capture the nonlinear relationship between flow and resistance quantified from previous computational fluid dynamic analyses of the total cavopulmonary connection (TCPC), and added respiration as well as skeletal muscle contraction.

RESULTS

(1) Without respiration, the computational model for both the normal and the Fontan cannot attain the values for CI at peak exercise reported in the clinical literature, (2) because flow through the TCPC is much greater during inspiration than during expiration, the effect on the CI of the dynamic (flow-related) TCPC resistance is much more dramatic during exercise than it is in breath-hold mode at rest, and (3) coupling breathing with skeletal muscle contraction leads to the highest augmentation of cardiac output, that is, the skeletal muscle pump is most effective when the intrathoracic pressure is at a minimum-at peak inspiration.

CONCLUSIONS

Novel insights emerge when a Fontan model incorporating dynamic TCPC resistance, full respiration, and skeletal muscle contraction can be compared to the model of the normal.

History of right heart catheterization: 100 years of experimentation and methodology development

The development of right heart catheterization has provided the clinician the ability to diagnose patients with congenital and acquired right heart disease, and to monitor patients in the intensive care unit with significant cardiovascular illnesses. The development of bedside pulmonary artery catheterization has become a standard of care for the critically ill patient since its introduction into the intensive care unit almost 40 years ago. However, adoption of this procedure into the mainstream of clinical practice occurred without prior evaluation or demonstration of its clinical or cost-effectiveness. Moreover, current randomized, controlled trials provide little evidence in support of the clinical utility of pulmonary artery catheterization in the management of critically ill patients. Nevertheless, the right heart catheter is an important diagnostic tool to assist the clinician in the diagnosis of congenital heart disease and acquired right heart disease, and moreover, when catheter placement is proximal to the right auricle (atria), this catheter provides an important and safe route for administration of fluids, medications, and parenteral nutrition. The purpose of this manuscript is to review the development of right heart catheterization that led to the ability to conduct physiologic studies in cardiovascular dynamics in normal individuals and in patients with cardiovascular diseases, and to review current controversies of the extension of the right heart catheter, the pulmonary artery catheter.