Pulsatile Flow Characteristics in a Stenotic Aortic Valve Model: An In Vitro Experimental Study

2019 ◽  
Author(s):  
Ruihang Zhang ◽  
Yan Zhang
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Aortic Valve ◽  
Pulsatile Flow ◽  
Heart Diseases ◽  
Flow Characteristics ◽  
Aortic Valve Area ◽  
Heart Rates ◽  
Valvular Heart Diseases

Abstract Aortic stenosis (AS) is one of the most common valvular heart diseases around the globe. The accurate assessment of AS severity is important and strongly associated with accurate interpretation of the hemodynamic parameters across the stenotic valve. In this study, we conducted in vitro fluid dynamic experiments to investigate the pulsatile flow characteristics of a stenotic aortic valve as a function of heart rate. An in vitro cardiovascular flow simulator was used to generate pulsatile flow with a prescribed waveform (40% systolic period and 4L/min cardiac output) under varied heart rates (50 bpm, 75 bpm and 100 bpm). The stenotic valve was constructed by molding silicone into three-leaflet aortic valve geometries wrapping around thin fabrics which increases its stiffness and tensile strength. Two-dimensional phase-locked particle image velocimetry (PIV) was employed to quantify the flow field characteristics of the stenotic valve. Pressure waveforms were recorded to evaluate the severity of the stenosis via the Gorlin and Hakki equations. Results suggest that as the heart rate increases, the peak pressure gradient across the stenotic aortic valve increases significantly under the same cardiac output. Analysis also shows the estimated aortic valve area (AVA) decreases as the heart rate increases under the same cardiac output using Gorlin equation estimation, while the trend is reversed using Hakki equation estimation. Under phase-locked conditions, quantitative flow characteristics, such as phase-averaged flow velocity, turbulence kinetic energy (TKE) for the stenotic aortic valve were analyzed based on the PIV data. Results suggest that the peak systolic jet velocity downstream of the valve increases as the heart rate increases, implying a longer pressure recovery distance as heart rate increases. While the turbulence at peak systole is higher under the slower heart rate, the faster heart rate contributes to a higher turbulence during the late systole and early diastole phases. Based on the comparison with no-valve cases, the differences in TKE was mainly related to the dynamics of leaflets under different heart rates. Overall, the results obtained in this study demonstrate that the hemodynamics of a stenotic aortic valve is complex and the assessment of AS could be significantly affected by the pulsating rate of the flow.

Effects of Heart Rate on the Pulsatile Flow Characteristics of a Stenotic Aortic Valve Model: An In Vitro Experimental Study

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Ruihang Zhang ◽  
Yan Zhang
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Aortic Valve ◽  
Pressure Gradient ◽  
Pulsatile Flow ◽  
Flow Characteristics ◽  
Aortic Valve Area ◽  
Heart Rates ◽  
Cardiovascular Flow

Abstract In this paper, the characteristics of pulsatile flow past a silicone-based artificial stenotic aortic valve under varied heart rates have been studied using particle image velocimetry (PIV). Pulsatile flow waveforms were generated by a closed-loop cardiovascular flow simulator. Phase-locked PIV was employed to quantify the average and turbulent flow field information. Pressure gradient waveforms were recorded to evaluate the severity of the stenosis. Results suggest that as the heart rate increases, the peak pressure gradient across the stenotic aortic valve increases significantly under the same cardiac output. Under the same cardiac output, the aortic valve area (AVA) estimated using Gorlin equation decreases as the heart rate increases, while the trend is reversed using Hakki equation estimation. PIV results suggest that the peak systolic jet velocity downstream of the valve increases as the heart rate increases, implying a longer pressure recovery distance as heart rate increases. While the turbulence at peak systole is higher under the slower heart rate, the faster heart rate contributes to higher turbulence during the late systole and early diastole phases. Based on the comparison with no-valve cases, the differences in turbulence kinetic energy (TKE) was mainly related to the dynamics of leaflets under different heart rates. Overall, the results obtained in this study demonstrate that the hemodynamics of a stenotic aortic valve is complex, and the assessment of AS could be significantly affected by the pulsating rate of the flow.

scholarly journals Hemodynamic Consequence of Different Pacing Modes after Aortic Valve Replacement

2018 ◽  
Vol 21 (2) ◽  
pp. 090
Author(s):  
Arndt H Kiessling
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Aortic Valve ◽  
Left Ventricular Hypertrophy ◽  
Aortic Valve Replacement ◽  
Diastolic Function ◽  
Valve Replacement ◽  
Ventricular Hypertrophy ◽  
Left Ventricular ◽  
Heart Rates

Objectives: Ventricular pacemaker stimulation may cause deterioration of hemodynamics in patients with left-ventricular hypertrophy following aortic valve replacement. Since the diastolic function is often impaired, it remains unclear which heart rate best optimizes cardiac output. Low heart rates are suggested to treat impaired diastolic function chronically, but it is possible that cardiac output may be augmented by increasing the heart rate in patients with a fixed stroke volume (SV). The aim of this study is the identification of the best pacing mode and heart rate for the surrogate parameter SV and cardiac index(CI) in patients with left ventricular hypertrophy.Methods: Various pacemaker stimulation modes and different heart rates, as well as their influence on hemodynamics, were tested following aortic valve replacement in 48 patients with severe left-ventricular hypertrophy (Intraventricular septum (IVS)>1.5 cm) and aortic stenosis. SV and cardiac output were recorded by pulse curve analysis. Four modes of stimulation (right ventricular pacemaker stimulation (DDDright), left ventricular pacemaker stimulation (DDDleft), biventricular pacemaker stimulation (DDDbi), atrial pacemaker stimulation (AAI)) were documented at five different rates (60, 80, 100, 120, 140 beats/min) and three different postoperative time points (intraoperatively, 3h and 24h postoperatively).Results: The highest CI was found at linear rates between 60 to 140bpm. AAI was the best mode of stimulation in the majority of cases (35%), but in others, either left, right and/or biventricular stimulation was found to be better (15%). SV showed a u-shaped trend with a peak at 100 beats/min.Conclusion: An increase in the heart rate does not lead to a notable drop in SV postoperatively in left-ventricular hypertrophy; hence a rise in cardiac output can be anticipated up to a rate of 100 beats/min. A standardized response in terms of an ideal pacemaker stimulation mode could not be identified.

The efficacy of sinus plication in aortic valvuloplasty for bicuspid aortic valve: experiments in a pulsatile flow simulation model

2021 ◽  
Author(s):  
Satoshi Arimura ◽  
Jumpei Takada ◽  
Gohki Nishimura ◽  
Natsuki Nakama ◽  
Eita Kawasaki ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Bicuspid Aortic Valve ◽  
Pulsatile Flow ◽  
Flow Simulation ◽  
Ultrasound Measurement ◽  
Hydrodynamic Effect ◽  
Promising Tool ◽  
Aortic Valvuloplasty ◽  
Flow Simulator

Abstract OBJECTIVES Sinus plication has emerged as a promising tool that can lead to better stability in bicuspid aortic valve (BAV) repair. However, the mechanisms underlying the efficacy of this technique are unclear. We evaluated the hydrodynamic effect of sinus plication using the experimental pulsatile flow simulator and our original BAV model in vitro. METHODS Based on the computed tomography data of a BAV patient who had undergone aortic valvuloplasty, a BAV model (group C, n = 6) was developed with bovine pericardium and vascular prosthesis (J-graft Shield Neo Valsalva 24 mm). We performed sinus plication (group SP, n = 6) in the BAV model and compared hydrodynamic data with the control model in the pulsatile flow simulator. Non-fused cusp angle, annulus diameter and effective height were measured by ultrasonography. RESULTS The average flow was significantly increased in group SP compared to group C (4.24 ± 0.14 l/min vs 4.14 ± 0.15 l/min, respectively, P = 0.034). The mean transvalvular pressure gradient and regurgitant fraction were significantly decreased in group SP compared to group C (11.6 ± 4.3 mmHg vs 16.6 ± 5.0 mmHg, respectively, P = 0.009 and 14.1 ± 2.0% vs 17.4 ± 2.1%, respectively, P = 0.001). Ultrasound measurement indicated that non-fused cusp angle was significantly increased in group SP compared to group C (163.8° ± 9.2° vs 153.0° ± 4.6°, respectively, P = 0.012). CONCLUSIONS Sinus plication in the BAV model significantly increased the commissural angle. It was effective in not only controlling regurgitation but also improving valve opening. These finding should be confirmed by evaluating cusp stress and/or long-term durability in the future studies.

The Effect of Heart Rate on Aortic Valve Area Calculated by Continuity Equation

1995 ◽  
Vol 25 (3) ◽  
pp. 629
Author(s):  
Yoon-Sik Choi ◽  
Jung-Don Seo ◽  
Young-Woo Lee ◽  
Hyeon-Cheol Gwon ◽  
Kee-Joon Choi ◽  
...  
Keyword(s):  
Heart Rate ◽  
Aortic Valve ◽  
Continuity Equation ◽  
Aortic Valve Area ◽  
Valve Area

scholarly journals MicroRNAs in Valvular Heart Diseases: Biological Regulators, Prognostic Markers and Therapeutical Targets

2021 ◽  
Vol 22 (22) ◽  
pp. 12132
Author(s):  
Francesco Nappi ◽  
Adelaide Iervolino ◽  
Sanjeet Singh Avtaar Singh ◽  
Massimo Chello
Keyword(s):  
Mitral Valve ◽  
Mitral Valve Prolapse ◽  
Heart Diseases ◽  
Osteoblastic Differentiation ◽  
New Drugs ◽  
Expression Vectors ◽  
Chordae Tendineae ◽  
Valvular Heart Diseases

miRNAs have recently attracted investigators’ interest as regulators of valvular diseases pathogenesis, diagnostic biomarkers, and therapeutical targets. Evidence from in-vivo and in-vitro studies demonstrated stimulatory or inhibitory roles in mitral valve prolapse development, aortic leaflet fusion, and calcification pathways, specifically osteoblastic differentiation and transcription factors modulation. Tissue expression assessment and comparison between physiological and pathological phenotypes of different disease entities, including mitral valve prolapse and mitral chordae tendineae rupture, emerged as the best strategies to address miRNAs over or under-representation and thus, their impact on pathogeneses. In this review, we discuss the fundamental intra- and intercellular signals regulated by miRNAs leading to defects in mitral and aortic valves, congenital heart diseases, and the possible therapeutic strategies targeting them. These miRNAs inhibitors are comprised of antisense oligonucleotides and sponge vectors. The miRNA mimics, miRNA expression vectors, and small molecules are instead possible practical strategies to increase specific miRNA activity. Advantages and technical limitations of these new drugs, including instability and complex pharmacokinetics, are also presented. Novel delivery strategies, such as nanoparticles and liposomes, are described to improve knowledge on future personalized treatment directions.

In the Loop—Left Ventricular Pressures

2011 ◽  
pp. 42-47
Author(s):  
James R. Munis
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Aortic Valve ◽  
Left Ventricle ◽  
Stroke Volume ◽  
Cardiovascular System ◽  
Aortic Root ◽  
Left Ventricular ◽  
Root Pressure ◽  
The Third

We've already looked at 2 types of pressure that affect physiology (atmospheric and hydrostatic pressure). Now let's consider the third: vascular pressures that result from mechanical events in the cardiovascular system. As you already know, cardiac output can be defined as the product of heart rate times stroke volume. Heart rate is self-explanatory. Stroke volume is determined by 3 factors—preload, afterload, and inotropy—and these determinants are in turn dependent on how the left ventricle handles pressure. In a pressure-volume loop, ‘afterload’ is represented by the pressure at the end of isovolumic contraction—just when the aortic valve opens (because the ventricular pressure is now higher than aortic root pressure). These loops not only are straightforward but are easier to construct just by thinking them through, rather than by memorization.

Effect of altered thyroid status on in vitro cardiac performance in rats

1987 ◽  
Vol 252 (4) ◽  
pp. H788-H795 ◽  
Author(s):  
K. H. McDonough ◽  
V. Chen ◽  
J. J. Spitzer
Keyword(s):  
Heart Rate ◽  
Body Weight ◽  
Cardiac Output ◽  
Thyroid Hormone ◽  
Systolic Pressure ◽  
Heart Weight ◽  
The Difference ◽  
Altered Thyroid ◽  
Similar Body

Effect of a chronic excess or deficit of thyroid hormone on intrinsic myocardial performance in rats was assessed. Animals were thyroidectomized or treated with thyroid hormone or vehicle 6-7 wk before the study. Body weight and heart weight were decreased in the hypothyroid group, and heart weight was elevated in the hyperthyroid group. Hearts were removed from thyroidectomized, euthyroid or thyroid-treated animals and studied as isolated, perfused working heart preparations. Ventricular function curves were generated by increasing left atrial filling pressure, whereas outflow resistance was not varied. Coronary flow, aortic outflow (and thus cardiac output), heart rate, and peak aortic systolic pressure were measured as a function of preload. These studies showed that performance of hearts from hyperthyroid animals was similar to that of euthyroid controls. Hearts from hypothyroid rats had decreased rate, pressure, and cardiac output but normal stroke volume. Since heart weight was 55% lower than control, normalization of volume work to dry heart weight reversed the difference in cardiac output. Comparison of hearts from hypothyroid animals to control rats of similar weight showed minimal differences in pump function. Thus hyperthyroidism did not result in altered in vitro cardiac output or peak systolic pressure as a function of changing preload when compared with age-matched euthyroid controls, hypothyroidism resulted in a decreased in vitro heart rate but greater cardiac output normalized to heart weight when compared with age-matched controls and hyperthyroid animals; external pacing of hypothyroid hearts yielded myocardial work parameters that were comparable to euthyroid control rats of similar body weight; and cardiac efficiency was significantly greater in hypothyroid hearts than in hyperthyroid hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract 18440: Cardiac Output Reserve Predicts Exercise Capacity and Need for Surgery in Aortic Stenosis

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Matthew Lumley ◽  
Rupert Williams ◽  
Michelle Navales ◽  
Denise Parkin ◽  
Helen Rimington ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Aortic Valve ◽  
Aortic Stenosis ◽  
Exercise Capacity ◽  
Maximal Exercise ◽  
Univariate Analysis ◽  
Exercise Duration ◽  
Exercise Stress ◽  
Peak Exercise ◽  
Aortic Valve Area

Background: The development of symptoms in patients with aortic stenosis (AS) relates inconsistently with echocardiographic measures of stenosis severity. This is a reflection of the dynamic interaction between the valve and ventricle on exercise, which is not captured by any single parameter. We hypothesised that cardiac output reserve (COR), the ratio of cardiac output at peak exercise to cardiac output at rest, would predict exercise capacity (EC) and the need for aortic valve surgery. Methods: 40 patients with moderate-severe AS, were prospectively recruited. All patients underwent resting transthoracic echocardiography, modified Bruce exercise treadmill testing (ETT), B-type natriuretic peptide measurement and bicycle exercise stress echocardiography. EC was defined by exercise duration during the ETT. The decision to refer the patient for surgery was made by the specialist valve team who had access to all data but were blinded to COR results. Regression analysis was performed using independent variables shown to correlate with each outcome measure on univariate analysis. Results: The mean±SD of the EC was 645±294s, aortic valve area (AVA) 0.92±0.28cm 2 and COR 1.86±0.39. 22 of the 40 patients were referred for surgery. Exercise Capacity: On univariate analysis, resting AVA or mean/peak pressure gradient (AVG) did not correlate with EC. EC significantly correlated with COR (r = 0.71, p < 0.000001), age (r = -0.63, p < 0.00005), BNP (r = -0.49, p = 0.03), peak AVG at maximal exercise (peak AVG ex ) (r = 0.32, p = 0.04) and tissue Doppler lateral mitral valve annulus systolic velocity, Sa (r = 0.32, p = 0.05). By multiple linear regression, only COR (β = 0.5, p = 0.0004) and peak AVG ex (β = 0.3, p = 0.09) were predictive of EC. Referral for Surgery: By ROC analysis, a COR of 1.8 (AUC 0.87, 95% CI 0.77-0.98) best predicted the need for surgery. Energy loss index at maximal exercise, meanAVG at rest and AVA at maximal exercise were also predictors of need for surgery. By binary logistic regression, only COR was predictive of the need for surgery (OR 0.02, 95% CI 0.00001-0.53, p = 0.03) Conclusion: Cardiac Output Reserve is a novel index that predicts exercise capacity and the need for surgery in moderate to severe AS.

Cardiac output of the hypothermic rat

1959 ◽  
Vol 196 (2) ◽  
pp. 415-419 ◽  
Author(s):  
Robert W. Bullard
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Arterial Pressure ◽  
Total Peripheral Resistance ◽  
Peripheral Resistance ◽  
Total Resistance ◽  
Vascular Geometry ◽  
Per Se ◽  
Colonic Temperature

As the colonic temperature of the rat was lowered the heart rate and cardiac output fell linearly with the temperature. The arterial pressure did not fall linearly indicating an increase of total peripheral resistance. The increase of hematocrit ratio and the effect of cold on blood per se combined to increase the in vitro viscosity threefold as the colonic temperature approached 15°C. It appears from these data that the increase in viscosity of the blood is the important factor in the increase in total resistance to flow and that little change in total or average vascular geometry took place. However, comparison of the local clearances of 1131 from specific extravascular areas shows that individual vascular geometries may be changing but in such a fashion as to balance out each other.

Sign in / Sign up

Export Citation Format

Share Document