A Constitutive Theory for Biomembranes: Application to Epicardial Mechanics

1992 ◽  
Vol 114 (4) ◽  
pp. 461-466 ◽  
Author(s):  
J. D. Humphrey ◽  
R. K. Strumpf ◽  
F. C. P. Yin
Keyword(s):  
Constitutive Relation ◽  
Experimental Approach ◽  
Functional Form ◽  
Biological Membrane ◽  
Left Ventricular ◽  
Constitutive Theory ◽  
Material Parameters ◽  
Biomechanical Behavior ◽  
The Right

We present a new theoretically motivated experimental approach for identifying the functional form of a constitutive relation for any nonlinear, anisotropic pseudoelastic biological membrane. The utility of this approach is illustrated by identifying, from biaxial data, a new constitutive relation for excised ventricular epicardium. Values of the associated material parameters are calculated and compared for right and left ventricular specimens. Based on our findings, we suggest that there are no significant differences in the biomechanical behavior of epicardium excised from the right and left ventricular free walls of canine hearts.

Determination of a Constitutive Relation for Passive Myocardium: II.—Parameter Estimation

1990 ◽  
Vol 112 (3) ◽  
pp. 340-346 ◽  
Author(s):  
J. D. Humphrey ◽  
R. K. Strumpf ◽  
F. C. P. Yin
Keyword(s):  
Constitutive Relation ◽  
Functional Form ◽  
Nonlinear Least Squares ◽  
Transversely Isotropic ◽  
Least Squares Regression ◽  
Material Parameters ◽  
Biomechanical Behavior ◽  
Best Fit

In the first paper of this series, we proposed a new transversely isotropic pseudostrain-energy function W for describing the biomechanical behavior of excised noncontracting myocardium. The specific functional form of W was inferred directly from biaxial data to be a polynomial function of two coordinate invariant measures of the finite deformation and five material parameters. In this paper, best-fit values of the material parameters are determined from biaxial data using a nonlinear least-squares regression. These values of the parameters are shown to be well-determined, and the final constitutive relation is shown to have good predictive capabilities. Since the proposed constitutive relation describes much broader classes of in-vitro biaxial data than previously proposed relations, it may be better applicable to analyses of stress in the passive heart.

Biaxial mechanical behavior of excised ventricular epicardium

1990 ◽  
Vol 259 (1) ◽  
pp. H101-H108 ◽  
Author(s):  
J. D. Humphrey ◽  
R. K. Strumpf ◽  
F. C. Yin
Keyword(s):  
Mechanical Behavior ◽  
Cardiac Mechanics ◽  
Left Ventricular ◽  
Biaxial Stress ◽  
Biomechanical Behavior ◽  
Highly Nonlinear ◽  
Nonlinear Stress ◽  
Parietal Pericardium ◽  
The Right

We present results from in vitro biaxial stress-strain experiments on epicardium excised from the right and left ventricular free walls of canine hearts. These data reveal that the biomechanical behavior of ventricular epicardium is qualitatively similar to atrial epicardium and parietal pericardium but different from noncontracting myocardium. In particular, ventricular epicardium exhibits a highly nonlinear stress-stretch behavior, being initially compliant but then very stiff near the limits of its extensibility. In addition, the epicardium appears to be initially isotropic but becomes markedly anisotropic upon rapid stiffening. Finally, specimens taken from the right and left ventricular free walls behaved similarly. We submit that excised ventricular epicardium is capable of carrying significant in-plane loads and that there is a need to investigate further its role in local and global cardiac mechanics and physiology.

Determination of a Constitutive Relation for Passive Myocardium: I. A New Functional Form

1990 ◽  
Vol 112 (3) ◽  
pp. 333-339 ◽  
Author(s):  
J. D. Humphrey ◽  
R. K. Strumpf ◽  
F. C. P. Yin
Keyword(s):  
Constitutive Relation ◽  
Invariant Measures ◽  
Functional Form ◽  
Transversely Isotropic ◽  
The Other ◽  
Material Symmetry ◽  
Material Parameters ◽  
Experimental Protocols ◽  
Theory And Experiment

The specific aim of this study is to determine a constitutive relation for non-contracting myocardium in terms of a pseudostrain-energy function W whose form is guided by both theory and experiment. We assume that the material symmetry of myocardium is initially and locally transversely-isotropic, and seek a W which depends upon only two coordinate invariant measures of the finite deformation. The specific functional form of such a W is inferred directly from experimental protocols in which one invariant is held constant while the other is varied, and vice versa. On the basis of data from families of these “constant invariant” tests on thin slabs of myocardium taken from the mid-walls of six canine left ventricles, we propose a new polynomial form of W containing only five material parameters.

ON CONSTRUCT OF THE RIGHT OF PRE-EMPTION IN RESPECT OF PARTICIPATORY INTEREST (SHARES)

2020 ◽  
Vol 20 (4) ◽  
pp. 94-219
Author(s):  
I.S. CHUPRUNOV
Keyword(s):  
General Rule ◽  
Constitutive Theory ◽  
Freedom Of Contract ◽  
Legal Nature ◽  
Public Corporation ◽  
Russian Law ◽  
Right Of First Refusal ◽  
The Right

The paper provides analysis of the legal nature and the mechanism for exercise of the right of pre-emption (right of first refusal) in respect of execution of a contract taking as an example of right of first refusal to purchase a stake in a non-public corporation, and also examines the boundaries of parties’ autonomy and freedom of contract in this area. The author comes to the conclusion that the key elements of the construction of the right of pre-emption are the transformation powers that belong to the right holder. The author also demonstrates that, notwithstanding their dominance in Russian law, the views, which suggest that exercise of the right of pre-emption leads to “transfer of rights and obligations of a purchaser” (the translative theory), should be rejected. These views must be replaced with the constitutive theory, according to which exercise of the right of pre-emption results in a new contract between the right holder and the seller (as a general rule, on the same terms that were agreed between the seller and the purchaser).

Prevalence and Localization of Hibernating Myocardium Among Patients with Left Ventricular Dysfunction

2019 ◽  
Vol 15 (9) ◽  
pp. 884-889
Author(s):  
Emine Acar ◽  
Ayşegül Aksu ◽  
Gökmen Akkaya ◽  
Gamze Çapa Kaya
Keyword(s):  
Scar Tissue ◽  
Left Ventricular ◽  
Hibernating Myocardium ◽  
Circumflex Artery ◽  
Irrigation Area ◽  
Left Circumflex Artery ◽  
Pet Ct ◽  
Perfusion Defects ◽  
The Right ◽  
Fdg Pet Ct

Objective: This study evaluated how much of the myocardium was hibernating in patients with left ventricle dysfunction and/or comorbidities who planned to undergo either surgical or interventional revascularization. Furthermore, this study also identified which irrigation areas of the coronary arteries presented more scar and hibernating tissue. Methods: At rest, Tc-99m MIBI SPECT and cardiac F-18 FDG PET/CT images collected between March 2009 and September 2016 from 65 patients (55 men, 10 women, mean age 64±12) were retrospectively analyzed in order to evaluate myocardial viability. The areas with perfusion defects that were considered metabolic were accepted as hibernating myocardium, whereas areas with perfusion defects that were considered non-metabolic were accepted as scar tissue. Results: Perfusion defects were observed in 26% of myocardium, on average 48% were associated with hibernation whereas other 52% were scar tissue. In the remaining Tc-99m MIBI images, perfusion defects were observed in the following areas in the left anterior descending artery (LAD; 31%), in the right coronary artery (RCA; 23%) and in the Left Circumflex Artery (LCx; 19%) irrigation areas. Hibernation areas were localized within the LAD (46%), LCx (54%), and RCA (64%) irrigation areas. Scar tissue was also localized within the LAD (54%), LCx (46%), and RCA (36%) irrigation areas. Conclusion: Perfusion defects are thought to be the result of half hibernating tissue and half scar tissue. The majority of perfusion defects was observed in the LAD irrigation area, whereas hibernation was most often observed in the RCA irrigation area. The scar tissue development was more common in the LAD irrigation zone.

scholarly journals Hemodynamic Support Using Percutaneous Transfemoral Impella 5.0 and Impella RP for Refractory Cardiogenic Shock

2019 ◽  
Vol 2019 ◽  
pp. 1-6 ◽  
Author(s):  
Pratik K. Dalal ◽  
Amy Mertens ◽  
Dinesh Shah ◽  
Ivan Hanson
Keyword(s):  
Left Ventricle ◽  
Pulmonary Artery ◽  
Cardiogenic Shock ◽  
Ventricular Function ◽  
Standard Of Care ◽  
Left Ventricular ◽  
Biventricular Failure ◽  
Ventricular Support ◽  
The Right ◽  
Flow Pump

Acute myocardial infarction (AMI) resulting in cardiogenic shock continues to be a substantial source of morbidity and mortality despite advances in recognition and treatment. Prior to the advent of percutaneous and more durable left ventricular support devices, prompt revascularization with the addition of vasopressors and inotropes were the standard of care in the management of this critical population. Recent published studies have shown that in addition to prompt revascularization, unloading of the left ventricle with the placement of the Impella percutaneous axillary flow pump can lead to improvement in mortality. Parameters such as the cardiac power output (CPO) and pulmonary artery pulsatility index (PAPi), obtained through pulmonary artery catheterization, can help ascertain the productivity of right and left ventricular function. Utilization of these parameters can provide the information necessary to escalate support to the right ventricle with the insertion of an Impella RP or the left ventricle with the insertion of larger devices, which provide more forward flow. Herein, we present a case of AMI complicated by cardiogenic shock resulting in biventricular failure treated with the percutaneous insertion of an Impella RP and Impella 5.0 utilizing invasive markers of left and right ventricular function to guide the management and escalation of care.

scholarly journals Right ventricular function and its coupling with the pulmonary circulation in acute heart failure

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
M Barki ◽  
M Losito ◽  
M.M Caracciolo ◽  
F Bandera ◽  
M Rovida ◽  
...  
Keyword(s):  
Heart Failure ◽  
Acute Heart Failure ◽  
Acute Phase ◽  
Pulmonary Circulation ◽  
Heart Function ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Response To Treatment ◽  
The Right ◽  
B Lines

Abstract Background The right ventricle (RV) is extremely sensitive to hemodynamic changes and increased impedance. In acute heart failure (AHF), the development of pulmonary venous congestion and the increase of left ventricular (LV) filling pressures favors pulmonary vascular adverse remodeling and ultimately RV dysfunction, leading to the onset of symptoms and to a further decay of cardiac dynamics. Purpose The aim of the study was to evaluate RV morphology and functional dynamics at admission and discharge in patients hospitalized for AHF, analyzing the role and the response to treatment of the RV and its coupling with pulmonary circulation (PC). Methods Eighty-one AHF patients (mean age 75.75±10.6 years, 59% males) were prospectively enrolled within 24–48 hours from admission to the emergency department (ED). In either the acute phase and at pre-discharge all patients underwent M-Mode, 2-Dimensional and Doppler transthoracic echocardiography (TTE), as well as lung ultrasonography (LUS), to detect an increase of extravascular lung water (EVLW) and development of pleural effusion. Laboratory tests were performed in the acute phase and at pre-discharge including the evaluation of NT-proBNP. Results At baseline we observed a high prevalence of RV dysfunction as documented by a reduced RV systolic longitudinal function [mean tricuspid annular plane systolic excursion (TAPSE) at admission of 16.47±3.86 mm with 50% of the patients exhibiting a TAPSE<16mm], a decreased DTI-derived tricuspid lateral annular systolic velocity (50% of the subjects showed a tricuspid s' wave<10 cm/s) and a reduced RV fractional area change (mean FAC at admission of 36.4±14.6%). Furthermore, an increased pulmonary arterial systolic pressure (PASP) and a severe impairment in terms of RV coupling to PC was detected at initial evaluation (mean PASP at admission: 38.8±10.8 mmHg; average TAPSE/PASP at admission: 0.45±0.17 mm/mmHg). At pre-discharge a significant increment of TAPSE (16.47±3.86 mm vs. 17.45±3.88; p=0.05) and a reduction of PASP (38.8±10.8 mmHg vs. 30.5±9.6mmHg, p<0.001) was observed. Furthermore, in the whole population we assisted to a significant improvement in terms of RV function and its coupling with PC as demonstrated by the significant increase of TAPSE/PASP ratio (TAPSE/PASP: 0.45±0.17 mm/mmHg vs 0.62±0.20 mm/mmHg; p<0.001). Patients significantly reduced from admission to discharge the number of B-lines and NT-proBNP (B-lines: 22.2±17.1 vs. 6.5±5 p<0.001; NT-proBNP: 8738±948 ng/l vs 4227±659 ng/l p<0.001) (Figure 1). Nonetheless, no significant changes of left atrial and left ventricular dimensions and function were noted. Conclusions In AHF, development of congestion and EVLW significantly impact on the right heart function. Decongestion therapy is effective for restoring acute reversal of RV dysfunction, but the question remains on how to impact on the biological properties of the RV. Funding Acknowledgement Type of funding source: None

scholarly journals Comparing Ventricular Synchrony in Left Bundle Branch and Left Ventricular Septal Pacing in Pacemaker Patients

2021 ◽  
Vol 10 (4) ◽  
pp. 822
Author(s):  
Luuk I.B. Heckman ◽  
Justin G.L.M. Luermans ◽  
Karol Curila ◽  
Antonius M.W. Van Stipdonk ◽  
Sjoerd Westra ◽  
...  
Keyword(s):  
Left Ventricular ◽  
Activation Time ◽  
Ventricular Synchrony ◽  
Septal Pacing ◽  
Ventricular Activation ◽  
Qrs Morphology ◽  
Conversion Matrix ◽  
Qrs Duration ◽  
The Right ◽  
Electrophysiological Effects

Background: Left bundle branch area pacing (LBBAP) has recently been introduced as a novel physiological pacing strategy. Within LBBAP, distinction is made between left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP, no left bundle capture). Objective: To investigate acute electrophysiological effects of LBBP and LVSP as compared to intrinsic ventricular conduction. Methods: Fifty patients with normal cardiac function and pacemaker indication for bradycardia underwent LBBAP. Electrocardiography (ECG) characteristics were evaluated during pacing at various depths within the septum: starting at the right ventricular (RV) side of the septum: the last position with QS morphology, the first position with r’ morphology, LVSP and—in patients where left bundle branch (LBB) capture was achieved—LBBP. From the ECG’s QRS duration and QRS morphology in lead V1, the stimulus- left ventricular activation time left ventricular activation time (LVAT) interval were measured. After conversion of the ECG into vectorcardiogram (VCG) (Kors conversion matrix), QRS area and QRS vector in transverse plane (Azimuth) were determined. Results: QRS area significantly decreased from 82 ± 29 µVs during RV septal pacing (RVSP) to 46 ± 12 µVs during LVSP. In the subgroup where LBB capture was achieved (n = 31), QRS area significantly decreased from 46 ± 17 µVs during LVSP to 38 ± 15 µVs during LBBP, while LVAT was not significantly different between LVSP and LBBP. In patients with normal ventricular activation and narrow QRS, QRS area during LBBP was not significantly different from that during intrinsic activation (37 ± 16 vs. 35 ± 19 µVs, respectively). The Azimuth significantly changed from RVSP (−46 ± 33°) to LVSP (19 ± 16°) and LBBP (−22 ± 14°). The Azimuth during both LVSP and LBBP were not significantly different from normal ventricular activation. QRS area and LVAT correlated moderately (Spearman’s R = 0.58). Conclusions: ECG and VCG indices demonstrate that both LVSP and LBBP improve ventricular dyssynchrony considerably as compared to RVSP, to values close to normal ventricular activation. LBBP seems to result in a small, but significant, improvement in ventricular synchrony as compared to LVSP.

scholarly journals Heart in Acromegaly: The Echocardiographic Characteristics of Patients Diagnosed with Acromegaly in Various Stages of the Disease

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Agata Popielarz-Grygalewicz ◽  
Jakub S. Gąsior ◽  
Aleksandra Konwicka ◽  
Paweł Grygalewicz ◽  
Maria Stelmachowska-Banaś ◽  
...  
Keyword(s):  
Right Ventricular ◽  
Healthy Volunteers ◽  
Global Longitudinal Strain ◽  
Interventricular Septum ◽  
Left Ventricular ◽  
Volume Index ◽  
Control Group ◽  
Glucose Metabolism Disorders ◽  
Acromegalic Cardiomyopathy ◽  
The Right

To determine whether the echocardiographic presentation allows for diagnosis of acromegalic cardiomyopathy. 140 patients with acromegaly underwent echocardiography as part of routine diagnostics. The results were compared with the control group comprising of 52 age- and sex-matched healthy volunteers. Patients with acromegaly presented with higher BMI, prevalence of arterial hypertension, and glucose metabolism disorders (i.e., diabetes and/or prediabetes). In patients with acromegaly, the following findings were detected: increased left atrial volume index, increased interventricular septum thickness, increased posterior wall thickness, and increased left ventricular mass index, accompanied by reduced diastolic function measured by the following parameters: E’med., E/E’, and E/A. Additionally, they presented with abnormal right ventricular systolic pressure. All patients had normal systolic function measured by ejection fraction. However, the values of global longitudinal strain were slightly lower in patients than in the control group; the difference was statistically significant. There were no statistically significant differences in the size of the right and left ventricle, thickness of the right ventricular free wall, and indexed diameter of the ascending aorta between patients with acromegaly and healthy volunteers. None of 140 patients presented systolic dysfunction, which is the last phase of the so-called acromegalic cardiomyopathy. Some abnormal echocardiographic parameters found in acromegalic patients may be caused by concomitant diseases and not elevated levels of GH or IGF-1 alone. The potential role of demographic parameters like age, sex, and/or BMI requires further research.

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