Effects of surgical ventricular restoration on left ventricular contractility assessed by a novel contractility index in patients with ischemic cardiomyopathy

Clinical and hemodynamic outcomes of the Dor procedure in adults with ischemic cardiomyopathy

Ischemic cardiomyopathy continues to be a major contributor to congestive heart failure, which places a significant burden on our healthcare system. Improving medications and different coronary revascularization strategies are the mainstays in the management of ischemic cardiomyopathy. Although medications and mechanical circulatory support are playing an ever-increasing role, cardiac transplantation remains the gold standard for treating advanced heart failure. Given the small number of available and suitable donor hearts, transplantation is limited for the majority of patients. Surgical ventricular restoration has repeatedly been suggested as a viable alternative in managing heart failure in select patients, as it is believed that surgically returning the ventricle to its original dimensions is possible and associated with favorable outcomes. The purpose of this manuscript is to comprehensively review the current literature on various surgical strategies for ventricular restoration. We also contextualize the published data with respect to ventricular function, volume, structure, arrhythmias, mitral regurgitation, and clinical outcomes.

Surgical Treatment of Ischemic Dilative Cardiomyopathy by Ventricular Restoration

Patients with symptomatic post-ischemic dilative myocardiopathy of the left ventricle require, in selected cases, an operation to reshape and reduce the volume of the left ventricular chamber, in addition to surgical myocardial revascularization and mitral valve repair, with the aim of prolonging survival, improving the quality of life and minimizing the need for re-hospitalizations related to recurrent heart failure. This procedure is called surgical ventricular restoration (SVR), and is a useful tool for the treatment of heart failure patients as an alternative to heart transplant. This article provides an overview of surgical ventricular restoration for the treatment of dilative ischemic myocardiopathy. It illustrates several surgical options, describes the operative details, and discusses the correct indications for the procedure. Finally, an interesting protocol for one-step cell therapy during SVR is proposed, as an innovative treatment for heart failure patients.

Outcomes after surgical ventricular restoration for ischemic cardiomyopathy

OBJECTIVE

The study objective was to evaluate the short- and long-term outcomes of patients with ischemic cardiomyopathy after surgical ventricular restoration and to identify risk factors related to poor results.

METHODS

Between August 2002 and April 2016, 62 patients affected by ischemic cardiomyopathy underwent surgical left ventricular restoration at our unit. Patients' mean age at operation was 63 years (39-79 years). Mean ejection fraction was 29.6%. The Surgical Treatment for Ischemic Heart Failure trial criteria have been used as indications for surgery. Fifty-seven patients (91%) received surgical myocardial revascularization. Mitral valve repair was performed in 39 patients (63%). The surgical technique consisted of the classic Dor operation or a different approach reducing the equatorial diameter of the left ventricle and avoiding the use of a patch. The data were analyzed retrospectively for perioperative results and short- and long-term clinical outcomes.

RESULTS

One patient died of noncardiac causes within 30 days (1.6%). All-cause death occurred in 36 patients (58%) during follow-up (0.6-14.7 years; median follow-up time, 7.02 years), of whom 15 died of cardiac causes. Age, need for preoperative intra-aortic balloon pump, reduction less than 35% of postoperative left ventricular end-diastolic and end-systolic volumes, type of surgical technique, and ejection fraction less than 25% were identified as risk factors for late cardiac mortality. Perioperative levosimendan administration and presence of preoperative moderate to severe mitral regurgitation influenced early and intermediate-term outcomes, but no statistical relevance on long-term results was demonstrated.

CONCLUSIONS

Patients with ischemic dilative cardiomyopathy have favorable short- and long-term outcomes after ventricular restoration. Age, preoperative ejection fraction less than 25%, inadequate left ventricular surgical reverse remodeling, and type of surgical technique negatively affect long-term survival.

Left Ventricular Wall Stress Is Sensitive Marker of Hypertrophic Cardiomyopathy With Preserved Ejection Fraction

Hypertrophic cardiomyopathy (HCM) patients present altered myocardial mechanics due to the hypertrophied ventricular wall and are typically diagnosed by the increase in myocardium wall thickness. This study aimed to quantify regional left ventricular (LV) shape, wall stress and deformation from cardiac magnetic resonance (MR) images in HCM patients and controls, in order to establish superior measures to differentiate HCM from controls. A total of 19 HCM patients and 19 controls underwent cardiac MR scans. The acquired MR images were used to reconstruct 3D LV geometrical models and compute the regional parameters (i.e., wall thickness, curvedness, wall stress, area strain and ejection fraction) based on the standard 16 segment model using our in-house software. HCM patients were further classified into four quartiles based on wall thickness at end diastole (ED) to assess the impact of wall thickness on these regional parameters. There was a significant difference between the HCM patients and controls for all regional parameters (P < 0.001). Wall thickness was greater in HCM patients at the end-diastolic and end-systolic phases, and thickness was most pronounced in segments at the septal regions. A multivariate stepwise selection algorithm identified wall stress index at ED (σ_i,ED) as the single best independent predictor of HCM (AUC = 0.947). At the cutoff value σ_i,ED < 1.64, both sensitivity and specificity were 94.7%. This suggests that the end-diastolic wall stress index incorporating regional wall curvature—an index based on mechanical principle—is a sensitive biomarker for HCM diagnosis with potential utility in diagnostic and therapeutic assessment.

Computational medical imaging and hemodynamics framework for functional analysis and assessment of cardiovascular structures

Cardiac dysfunction constitutes common cardiovascular health issues in the society, and has been an investigation topic of strong focus by researchers in the medical imaging community. Diagnostic modalities based on echocardiography, magnetic resonance imaging, chest radiography and computed tomography are common techniques that provide cardiovascular structural information to diagnose heart defects. However, functional information of cardiovascular flow, which can in fact be used to support the diagnosis of many cardiovascular diseases with a myriad of hemodynamics performance indicators, remains unexplored to its full potential. Some of these indicators constitute important cardiac functional parameters affecting the cardiovascular abnormalities. With the advancement of computer technology that facilitates high speed computational fluid dynamics, the realization of a support diagnostic platform of hemodynamics quantification and analysis can be achieved. This article reviews the state-of-the-art medical imaging and high fidelity multi-physics computational analyses that together enable reconstruction of cardiovascular structures and hemodynamic flow patterns within them, such as of the left ventricle (LV) and carotid bifurcations. The combined medical imaging and hemodynamic analysis enables us to study the mechanisms of cardiovascular disease-causing dysfunctions, such as how (1) cardiomyopathy causes left ventricular remodeling and loss of contractility leading to heart failure, and (2) modeling of LV construction and simulation of intra-LV hemodynamics can enable us to determine the optimum procedure of surgical ventriculation to restore its contractility and health This combined medical imaging and hemodynamics framework can potentially extend medical knowledge of cardiovascular defects and associated hemodynamic behavior and their surgical restoration, by means of an integrated medical image diagnostics and hemodynamic performance analysis framework.

Atrioventricular junction (AVJ) motion tracking: a software tool with ITK/VTK/Qt

The quantitative measurement of the Atrioventricular Junction (AVJ) motion is an important index for ventricular functions of one cardiac cycle including systole and diastole. In this paper, a software tool that can conduct AVJ motion tracking from cardiovascular magnetic resonance (CMR) images is presented by using Insight Segmentation and Registration Toolkit (ITK), The Visualization Toolkit (VTK) and Qt. The software tool is written in C++ by using Visual Studio Community 2013 integrated development environment (IDE) containing both an editor and a Microsoft complier. The software package has been successfully implemented. From the software engineering practice, it is concluded that ITK, VTK, and Qt are very handy software systems to implement automatic image analysis functions for CMR images such as quantitative measure of motion by visual tracking.

Novel method for atrioventricular motion assessment from three-dimensional cine magnetic resonance imaging

This study was carried out to (i) track the motion of six atrioventricular junction (AVJ) sites from the two-, three-, and four-chamber cardiovascular magnetic resonance (CMR) views in 27 healthy subjects, (ii) extract four clinically most useful AVJ velocities (i.e., myocardial systolic velocities Sm1 and Sm2, early diastolic velocity Em, and late diastolic velocity Am) for each AVJ site, and (iii) assess the relationship between CMR measurements to age and gender, and set up preliminary normal reference ranges for CMR derived AVJ velocites stratified by age and gender. The data obtained by CMR based method demonstrated that men had significant higher Sm1 (10.5±3.7 cm/s vs. 7.8±2.5 cm/s, P<;0.05) and Am (10.5±4.5 cm/s vs. 7.7±2.6 cm/s, P<;0.05), but comparable Sm2 (6.6±2.2 cm/s vs. 6.9±1.6 cm/s, P>0.05) and Em (11.2±3.3 cm/s vs. 11.5±4.3 cm/s, P>0.05) than women. There was no significant correlation between Sm1, Sm2 and age, while Em and Am strongly or moderately correlated with age. The lateral, posterolateral and posterior AVJ velocities were significant higher than the ones in septal, anteroseptal and anterior locations. Atrioventricular motion and derived velocities are independent of imaging reference frames, and thereby computationally light-weight. They can be derived by post-processing three-dimensional routine CMR images without additional image acquisition. This shall potentially extend routine CMR's capability for left ventricular (LV) systolic and diastolic function assessment.

Automated quantitative assessment of cardiovascular magnetic resonance-derived atrioventricular junction velocities

The assessment of atrioventricular junction (AVJ) deformation plays an important role in evaluating left ventricular systolic and diastolic function in clinical practice. This study aims to demonstrate the effectiveness and consistency of cardiovascular magnetic resonance (CMR) for quantitative assessment of AVJ velocity compared with tissue Doppler echocardiography (TDE). A group of 145 human subjects comprising 21 healthy volunteers, 8 patients with heart failure, 17 patients with hypertrophic cardiomyopathy, 52 patients with myocardial infarction, and 47 patients with repaired Tetralogy of Fallot were prospectively enrolled and underwent TDE and CMR scan. Six AVJ points were tracked with three CMR views. The peak systolic velocity (Sm1), diastolic velocity during early diastolic filling (Em), and late diastolic velocity during atrial contraction (Am) were extracted and analyzed. All CMR-derived septal and lateral AVJ velocities correlated well with TDE measurements (Sm1: r = 0.736; Em: r = 0.835; Am: r = 0.701; Em/Am: r = 0.691; all p < 0.001) and demonstrated excellent reproducibility [intrastudy: r = 0.921-0.991, intraclass correlation coefficient (ICC): 0.918-0.991; interstudy: r = 0.900-0.970, ICC: 0.887-0.957; all p < 0.001]. The evaluation of three-dimensional AVJ motion incorporating measurements from all views better differentiated normal and diseased states [area under the curve (AUC) = 0.918] and provided further insights into mechanical dyssynchrony diagnosis in HF patients (AUC = 0.987). These findings suggest that the CMR-based method is feasible, accurate, and consistent in quantifying the AVJ deformation, and subsequently in diagnosing systolic and diastolic cardiac dysfunction.

DECREASED LEFT VENTRICULAR CONTRACTILITY AND VENTRICULAR-ARTERIAL MATCHING INDEX CORRELATION WITH N-TERMINAL PRO B-TYPE NATRIURETIC PEPTIDE IN HEART FAILURE

This study is aimed to assess (1) Left ventricle (LV) contractile function and ventricular-arterial matching from echocardiography; (2) whether ventricular-arterial matching (VAM) is associated with N-terminal pro B-type natriuretic peptide (NT-proBNP), and stroke output in patients with heart failure. Normal subjects (n = 81) and heart failure patients (n = 80) underwent echocardiography, Doppler echocardiography and tissue Doppler imaging. Only heart failure patients underwent blood test for NT-proBNP. The LV contractility was calculated as dσ ⁎ /dt max = 3 × (dV/dt) max /2V m = 3 × V peak × (π × D2/4)/(2V m ), and the arterial elastance was calculated as Ea = SBP × 0.9/ SV , wherein V peak and D are peak velocity and diameter of LV outflow tract, Vm is myocardial volume, SBP is the systolic blood pressure and SV is stroke volume measured from LVOT. The VAM index was expressed as the ratio of LV contractility to arterial elastance (dσ ⁎ /dt max /Ea). We found that HF patients had (i) decreased dσ ⁎ /dt max (1.46 ± 0.73 versus 4.06 ± 1.06 s-1), (ii) increased Ea (2.90 ± 0.87 versus 1.81 ± 0.38 mmHg/mL), and (iii) attenuated ventricular-arterial matching index (0.66 ± 0.57 versus 2.38 ± 0.91 mL/mmHg⋅s) (all p < 0.001) compared with normal subjects. The VAM index was correlated inversely with NT-proBNP (r = -0.32, p < 0.05), but positively with the stroke volume (r = 0.85, p < 0.001). The VAM index of < 1.51 was able to clearly differentiate the failing heart from normal hearts (AUC = 0.959, Sensitivity = 0.911, Specificity = 0.905). Heart failure patients demonstrated impaired ventricular contractility, enhanced arterial stiffening, and attenuated ventricular-arterial matching index. The attenuated ventricular-arterial matching index value was associated with elevated NT-proBNP levels and lower cardiac output.

Three-dimensional CFD/MRI modeling reveals that ventricular surgical restoration improves ventricular function by modifying intraventricular blood flow

Surgical ventricular restoration (SVR) is designed to normalize distorted ventricular shape and size in patients with left ventricular (LV) dysfunction and akinetic and dyskinetic segments. This study is aimed to quantify the characteristics of LV as a pump for a case before and after SVR, which is followed by coronary artery bypass grafting (CABG). We hypothesize that SVR+CABG improves heart flow. A patient with heart failure had magnetic resonance (MR) scans before and 4 months after SVR. LV endocardial geometries were semi-automated segmented and reconstructed using our customized algorithm. The arbitrary Lagrangian-Eulerian formulation of Navier-Stokes equations was solved to derive the flow patterns and calculate pressure differences in LV. After SVR, LV ejection fraction increased from 34% to 48% in patient but was still lower than normal (70%). Second, LV vortices were stronger than pre-surgery but still weaker than normal. The maximum pressure differences between ventricular base and apex increased from 180 to 400 Pa during diastole, from 252 to 560 Pa during systole, respectively. As anticipated, SVR reduced LV volumes and augmented LV ejection fraction. Three-dimensional CFD/MRI modeling suggests that improved diastolic and systolic ventricular function after SVR is associated with changes in intraventricular blood flow.

Extent of load-independence of pressure-normalized stress in swine

A load-independent index of myocardial contractility provides a measure of cardiac function. Previous contractility indices have been shown to be either load-dependent or invasive. We sought to determine the extent of load (preload and afterload)-independence of dσ*/dtmax (σ* is pressure-normalized stress) in comparison with other well-established indices. Six anaesthetized pigs underwent left ventricular pressure-volume measurements under various load conditions. The average preload was decreased by 70.0 ± 15.0% (from 39.2 ± 6.4 mL to 11.7 ± 7.7 mL) and increased by 49.3 ± 5.9% (from 35.1 ± 7.4 mL to 51.7 ± 8.9 mL). The average afterload was increased by 74.3 ± 43.5% (from 3.3 ± 0.6 mmHg/mL to 5.7 ± 1.7 mmHg/mL). When preload was reduced within an average of 21.7% (39.2 ± 6.4 mL to 30.7 ± 6.2 mL) using occlusion of the inferior vena cava, dσ*/dt max did not change significantly (6.50 ± 1.10 s⁻¹ vs 6.60 ± 0.90 s⁻¹, P = non-significant [NS]). When preload was increased within an average of 29.3% (35.1 ± 7.4 mL to 45.4 ± 7.3 mL) from infusion of normal saline, dσ*/dt max did not change significantly (7.04 ± 1.00 s⁻¹ vs 7.29 ± 1.10 s⁻¹, P = NS). When afterload was increased within an average of 42.4% (3.3 ± 0.6 mmHg/mL to 4.7 ± 1.0 mmHg/mL) using intra-aortic balloon occlusion, dσ*/dtmax did not change significantly (6.72 ± 1.18 s⁻¹ vs 6.89 ± 1.28 s⁻¹, P = NS). As expected, dσ*/dtmax was significantly increased with dobutamine. A linear regression showed no correlation between dσ*/dtmax and preload (r² = 0.02, P = 0.17) within a maximum range of -30% to +50% of preload change, or between dσ*/dtmax and afterload (r² = 0.03, P = 0.36) within maximum range of 0-100% of afterload increase, respectively. In conclusion, dσ*/dtmax is independent of loading conditions within an average of 21.7% of preload decrease, 29.3% of preload increase, 42.4% of afterload increase, and sensitive to dobutamine infusion.

Analysis of patient-specific surgical ventricular restoration: importance of an ellipsoidal left ventricular geometry for diastolic and systolic function

Surgical ventricular restoration (SVR) is a procedure designed to treat heart failure by surgically excluding infarcted tissues from the dilated failing left ventricle. To elucidate and predict the effects of geometrical changes from SVR on cardiac function, we created patient-specific mathematical (finite-element) left ventricular models before and after surgery using untagged magnetic resonance images. Our results predict that the postsurgical improvement in systolic function was compromised by a decrease in diastolic distensibility in patients. These two conflicting effects typically manifested as a more depressed Starling relationship (stroke volume vs. end-diastolic pressure) after surgery. By simulating a restoration of the left ventricle back to its measured baseline sphericity, we show that both diastolic and systolic function improved. This result confirms that the increase in left ventricular sphericity commonly observed after SVR (endoventricular circular patch plasty) has a negative impact and contributes partly to the depressed Starling relationship. On the other hand, peak myofiber stress was reduced substantially (by 50%) after SVR, and the resultant left ventricular myofiber stress distribution became more uniform. This significant reduction in myofiber stress after SVR may help reduce adverse remodeling of the left ventricle. These results are consistent with the speculation proposed in the Surgical Treatment for Ischemic Heart Failure trial (20) for the neutral outcome, that "the lack of benefit seen with surgical ventricular reconstruction is that benefits anticipated from surgical reduction of left ventricular volume (reduced wall stress and improvement in systolic function) are counter-balanced by a reduction in diastolic distensibility."

Algisyl-LVR™ with coronary artery bypass grafting reduces left ventricular wall stress and improves function in the failing human heart

BACKGROUND

Left ventricular (LV) wall stress reduction is a cornerstone in treating heart failure. Large animal models and computer simulations indicate that adding non-contractile material to the damaged LV wall can potentially reduce myofiber stress. We sought to quantify the effects of a novel implantable hydrogel (Algisyl-LVR™) treatment in combination with coronary artery bypass grafting (i.e. Algisyl-LVR™+CABG) on both LV function and wall stress in heart failure patients.

METHODS AND RESULTS

Magnetic resonance images obtained before treatment (n=3), and at 3 months (n=3) and 6 months (n=2) afterwards were used to reconstruct the LV geometry. Cardiac function was quantified using end-diastolic volume (EDV), end-systolic volume (ESV), regional wall thickness, sphericity index and regional myofiber stress computed using validated mathematical modeling. The LV became more ellipsoidal after treatment, and both EDV and ESV decreased substantially 3 months after treatment in all patients; EDV decreased from 264 ± 91 ml to 146 ± 86 ml and ESV decreased from 184 ± 85 ml to 86 ± 76 ml. Ejection fraction increased from 32 ± 8% to 47 ± 18% during that period. Volumetric-averaged wall thickness increased in all patients, from 1.06 ± 0.21 cm (baseline) to 1.3 ± 0.26 cm (3 months). These changes were accompanied by about a 35% decrease in myofiber stress at end-of-diastole and at end-of-systole. Post-treatment myofiber stress became more uniform in the LV.

CONCLUSIONS

These results support the novel concept that Algisyl-LVR™+CABG treatment leads to decreased myofiber stress, restored LV geometry and improved function.

Myocardial contractile dysfunction associated with increased 3-month and 1-year mortality in hospitalized patients with heart failure and preserved ejection fraction

BACKGROUND

There is a clinical need for a contractility index that reflects myocardial contractile dysfunction even when ejection fraction (EF) is preserved. We used novel relative load-independent global and regional contractility indices to compare left ventricular (LV) contractile function in three groups: heart failure (HF) with preserved ejection fraction (HFPEF), HF with reduced ejection fraction (HFREF) and normal subjects. Also, we determined the associations of these parameters with 3-month and 1-year mortality in HFPEF patients.

METHODS

199 HFPEF patients [median age (IQR): 75 (67-80) years] and 327 HFREF patients [69 (59-76) years] were recruited following hospitalization for HF; 22 normal control subjects [65 (54-71) years] were recruited for comparison. All patients underwent standard two-dimensional Doppler and tissue Doppler echocardiography to characterize LV dimension, structure, global and regional contractile function.

RESULTS

The median (IQR) global LV contractility index, dσ*/dtmax was 4.30s(-1) (3.51-4.57s(-1)) in normal subjects but reduced in HFPEF [2.57 (2.08-3.64)] and HFREF patients [1.77 (1.34-2.30)]. Similarly, median (IQR) regional LV contractility index was 99% (88-104%) in normal subjects and reduced in HFPEF [81% (66-96%)] and HFREF [56% (41-71%)] patients. Multi-variable logistic regression analysis on HFPEF identified sc-mFS <76% as the most consistent predictor of both 3-month (OR=7.15, p<0.05) and 1-year (OR=2.57, p<0.05) mortality after adjusting for medical conditions and other echocardiographic measurements.

CONCLUSION

Patients with HFPEF exhibited decreased LV global and regional contractility. This population-based study demonstrated that depressed regional contractility index was associated with higher 3-month and 1-year mortality in HFPEF patients.

NONDIMENSIONAL PHYSIOLOGICAL INDICES FOR MEDICAL ASSESSMENT

In medicine, for making a diagnosis, many tests are needed. It may so happen that some test results may be in the normal range, while some test results may be abnormal. So how is the doctor going to precisely decide how "sick" is the patient: is s/he at risk, or marginal, or very sick?

Hence, we have developed the new concept of a Nondimensional Physiological Index (NDPI). This NDPI is made up of a number of parameters characterizing organ function and dysfunction or a physiological system function and disorder or an anatomical structure's property and pathology, in the format of a medical assessment test; the NDPI combines these parameters into one nondimensional number. Thus, the NDPI enables the doctor to integrate all the parameters' values from the medical test into one nondimensional index value or number. Then, by examining a large number of patients, we can determine the statistical distribution of that particular NDPI into normal and abnormal categories. This makes it convenient for the doctor to make the medical assessment or diagnosis.

Now for an organ or physiological system assessment test (such as a Treadmill test or Glucose tolerance test) or for an anatomical structure's property and pathology determination (such as for determining mitral valve calcification and pathology), the method of formulating and evaluating the NDPI (from the medical test) entails developing its bioengineering model equation incorporating the parameters characterizing the organ state or physiological system function or the anatomical structural constitutive property. These parameters are adroitly combined into a NDPI, so that the NDPI unambiguously conveys the normal and abnormal state of the organ or physiological system or anatomical structure. This bioengineering model's governing equation or solution (involving the model parameters) is then applied to fit or simulate the monitored test data of the physiological system or the anatomical structure. The model parameters are then evaluated (from the simulated solution to the test data), and their ranges are determined for normal and abnormal states of the organ or physiological system or anatomical structure. Then, the NDPI (composed of the parameters of the organ function or physiological system function or the anatomical structural constitutive property) is also evaluated for normal and abnormal states of the patient's organ or physiological system or anatomical structure.

In this way, we can apply these NDPIs to reliably diagnose the patient's state of health, from preferably noninvasive medical assessment tests. In this paper, we have developed a number of noninvasive medical tests involving NDPIs, based on biomedical engineering formulations of organ function, physiological system functional performance and anatomical structural constitutive property, to provide the means for reliable medical assessment and diagnosis. These tests include (i) some conventional tests, such as Treadmill and Glucose tolerance tests, (ii) determination of cardiac contractility (and myocardial infarcted segments) and lung ventilation performance characteristics (and lung diseases) as well as (iii) some of our newly formulated tests, to detect arteriosclerosis, aortic pathology, mitral valve calcification, and osteoporosis.

CARDIAC CONTRACTILITY MEASURES OF LEFT VENTRICULAR SYSTOLIC FUNCTIONAL ASSESSMENT OF NORMAL AND DISEASED HEARTS

Left ventricular (LV) contraction is the basis of LV systolic function, impairment of which underlies heart failure pathophysiology. Its accurate quantification in the form of LV contractility indices is imperative for diagnostic and follow-up assessment of LV systolic function in heart failure.

Herein, we analyze LV contractile performance by focusing on LV contractility indices at different physiological organizational levels: from sarcomere dynamics to LV myocardial properties (such as elastic modulus and elastance), and from LV wall contractile stress development to the generation of intra-LV blood flow velocities and pressure distributions. Further, we present the development analyses of these indices and their medical applications. Using improved development of invasive and noninvasive techniques for measuring ventricular pressure, geometry, and volume, we show how these indices have become more amenable for clinical usage to obtain better patient assessment.

The purpose of this paper is to present a comprehensive coverage of LV contraction physiology, indices to qualify LV contraction, formulation, and medical applications of some major intrinsic LV contractility indices, so as to provide the basis of functional assessment of normal versus diseased hearts.

Increased ascending aortic wall stress in patients with bicuspid aortic valves

BACKGROUND

Patients with bicuspid aortic valves (BAV) are at increased risk of ascending aortic dilatation, dissection, and rupture. We hypothesized that ascending aortic wall stress may be increased in patients with BAV compared with patients with tricuspid aortic valves (TAV).

METHODS

Twenty patients with BAV and 20 patients with TAV underwent electrocardiogram-gated computed tomographic angiography. Patients were matched for diameter. The thoracic aorta was segmented, reconstructed, and triangulated to create a mesh. Utilizing a uniform pressure load of 120 mm Hg, and isotropic, incompressible, and linear elastic shell elements, finite element analysis was performed to predict 99th percentile wall stress.

RESULTS

For patients with BAV and TAV, aortic root diameter was 4.0 ± 0.6 cm and 4.0 ± 0.6 cm (p = 0.724), sinotubular junction diameter was 3.6 ± 0.8 cm and 3.6 ± 0.7 cm (p = 0.736), and maximum ascending aortic diameter was 4.0 ± 0.8 cm and 4.1 ± 0.9 cm (p = 0.849), respectively. The mean 99 th percentile wall stress in the BAV group was greater than in the TAV group (0.54 ± 0.06 MPa vs 0.50 ± 0.09 MPa), though this did not reach statistical significance (p = 0.090). When normalized by radius, the 99 th percentile wall stress was greater in the BAV group (0.31 ± 0.06 MPa/cm vs 0.27 ± 0.03 MPa/cm, p = 0.013).

CONCLUSIONS

Patients with BAV, regardless of aortic diameter, have increased 99 th percentile wall stress in the ascending aorta. Ascending aortic three-dimensional geometry may account in part for the increased propensity to aortic dilatation, rupture, and dissection in patients with BAV.

Left ventricular wall stress compendium

Left ventricular (LV) wall stress has intrigued scientists and cardiologists since the time of Lame and Laplace in 1800s. The left ventricle is an intriguing organ structure, whose intrinsic design enables it to fill and contract. The development of wall stress is intriguing to cardiologists and biomedical engineers. The role of left ventricle wall stress in cardiac perfusion and pumping as well as in cardiac pathophysiology is a relatively unexplored phenomenon. But even for us to assess this role, we first need accurate determination of in vivo wall stress. However, at this point, 150 years after Lame estimated left ventricle wall stress using the elasticity theory, we are still in the exploratory stage of (i) developing left ventricle models that properly represent left ventricle anatomy and physiology and (ii) obtaining data on left ventricle dynamics. In this paper, we are responding to the need for a comprehensive survey of left ventricle wall stress models, their mechanics, stress computation and results. We have provided herein a compendium of major type of wall stress models: thin-wall models based on the Laplace law, thick-wall shell models, elasticity theory model, thick-wall large deformation models and finite element models. We have compared the mean stress values of these models as well as the variation of stress across the wall. All of the thin-wall and thick-wall shell models are based on idealised ellipsoidal and spherical geometries. However, the elasticity model's shape can vary through the cycle, to simulate the more ellipsoidal shape of the left ventricle in the systolic phase. The finite element models have more representative geometries, but are generally based on animal data, which limits their medical relevance. This paper can enable readers to obtain a comprehensive perspective of left ventricle wall stress models, of how to employ them to determine wall stresses, and be cognizant of the assumptions involved in the use of specific models.

Attenuation of Stress-based Ventricular Contractility in Patients with Heart Failure and Normal Ejection Fraction

Introduction: The maximal rate of change of pressure-normalised wall stress dσ*/dtmax has been proposed as cardiac index of left ventricular (LV) contractility. In this study, we assessed the capacity of dσ*/dtmax to diagnose heart failure with normal ejection fraction (HFNEF). Materials and Methods: One hundred healthy normal controls and 140 patients admitted with heart failure (100, HFREF and 40, HFNEF) underwent echocardiography for stress-based contractility dσ*/dtmax. Patients with significant valvular heart disease were excluded. Tissue Doppler indices were also measured. Results: dσ*/dtmaxwas 4.43 ± 1.27 s-1 in control subjects; reduced in HFNEF, 3.02 ± 0.98 s-1; and HFREF, 2.00 ± 0.67 s-1 (P <0.001). In comparison with age- and sex-matched groups (n = 26 each), we found similar trend on reduction of dσ*/dtmax (normal control; 3.91 ± 0.87 s-1; HFNEF, 2.90 ± 0.84 s-1; HFREF, 1.84 ± 0.59 s-1, P <0.001). On multivariate analysis, dσ*/dtmax was found to be the independent predictor of HFNEF and HFREF. The area under the curve of the receiver operating characteristics (ROC) in detecting HFNEF compared with normal controls (dσ*/dtmax >3.2 s-1) was 0.84 (P <0.0001), and in detecting HFREF compared with HFNEF (dσ*/dtmax >2.32 s-1) was 0.88 (P <0.0001). Conclusion: This data confirms that dσ*/dtmax on echocardiography is a powerful independent predictor in patients with HFNEF. In a population with a high suspicion of HFNEF, dσ*/dtmax may significantly contribute to early diagnosis and hence be useful in the triage and management of HFNEF patients. Key words: Echocardiography, Heart failure with normal ejection fraction, Normalised wall-stress

Low-risk profile for malignant ventricular arrhythmias and sudden cardiac death after surgical ventricular reconstruction

BACKGROUND

Although it has been recently demonstrated that there was no significant difference in total survival and clinical outcomes between patients who underwent coronary artery bypass grafting (CABG) with or without surgical ventricular reconstruction (SVR), the question of whether or not SVR decreases the arrhythmic risk profile in this population has not been clarified yet.

OBJECTIVE

To determine the real incidence of sudden cardiac death (SCD) and sustained ventricular tachycardia/ventricular fibrillation (sustained VT/VF) in patients following CABG added to SVR and to define their clinical and echocardiographic parameters predicting in-hospital and long-term arrhythmic events (SCD + sustained VT/VF).

METHODS

Pre- and postoperative clinical and echocardiographic values as well as postoperative electrocardiogram Holter data of 65 patients (21 female, 63 ± 11 years) who underwent SVR + CABG were retrospectively evaluated.

RESULTS

 Mean follow-up was 1,105 ± 940 days. At 3 years, the SCD-free rate was 98% and the rate free from arrhythmic events was 88%. Multivariate logistic analysis identified a preoperative left ventricular end-systolic volume index (LVESVI) > 102 mL/m(2) (odds ratio [OR] 1.4, confidence interval [CI] 1.073-1.864, P = 0.02; sensitivity 100%, specificity 94%) and a postoperative pulmonary artery systolic pressure (PASP) > 27 mmHg (OR 2.3, CI 1.887-4.487, P = 0.01; sensitivity 100%, specificity 71%) as independent predictors of arrhythmic events.

CONCLUSIONS

Our and previous studies report a low incidence of arrhythmic events in patients following SVR added to CABG, considering the high-risk profile of the study population. A preoperative LVESVI > 102 mL/m(2) and a postoperative PASP > 27 mmHg had a good sensitivity and specificity in predicting arrhythmic events.

Impact of surgical ventricular restoration on ventricular shape, wall stress, and function in heart failure patients

Surgical ventricular restoration (SVR) was designed to treat patients with aneurysms or large akinetic walls and dilated ventricles. Yet, crucial aspects essential to the efficacy of this procedure like optimal shape and size of the left ventricle (LV) are still debatable. The objective of this study is to quantify the efficacy of SVR based on LV regional shape in terms of curvedness, wall stress, and ventricular systolic function. A total of 40 patients underwent magnetic resonance imaging (MRI) before and after SVR. Both short-axis and long-axis MRI were used to reconstruct end-diastolic and end-systolic three-dimensional LV geometry. The regional shape in terms of surface curvedness, wall thickness, and wall stress indexes were determined for the entire LV. The infarct, border, and remote zones were defined in terms of end-diastolic wall thickness. The LV global systolic function in terms of global ejection fraction, the ratio between stroke work (SW) and end-diastolic volume (SW/EDV), the maximal rate of change of pressure-normalized stress (dσ*/dt(max)), and the regional function in terms of surface area change were examined. The LV end-diastolic and end-systolic volumes were significantly reduced, and global systolic function was improved in ejection fraction, SW/EDV, and dσ*/dt(max). In addition, the end-diastolic and end-systolic stresses in all zones were reduced. Although there was a slight increase in regional curvedness and surface area change in each zone, the change was not significant. Also, while SVR reduced LV wall stress with increased global LV systolic function, regional LV shape and function did not significantly improve.

Three-dimensional echocardiography for the preoperative assessment of patients with left ventricular aneurysm

BACKGROUND

Surgical ventricular reconstruction has been proposed as a treatment option in heart failure patients with left ventricular (LV) aneurysm. The feasibility of this procedure has some limitations, and extensive preoperative evaluation is necessary to give the correct indication. For this purpose, magnetic resonance imaging (MRI) is currently considered the gold standard, providing accurate quantification of LV shape, size, and global and regional function together with the assessment of myocardial scar and mitral regurgitation severity. The aim of this study was to evaluate the accuracy of real-time three-dimensional echocardiography (RT3DE) as a potential alternative to MRI for this evaluation.

METHODS

A total of 52 patients with ischemic cardiomyopathy and LV aneurysm underwent a comprehensive analysis with two-dimensional echocardiography, RT3DE, and MRI.

RESULTS

Excellent correlation (r=0.97, p<0.001) and agreement were found between RT3DE and MRI for quantification of LV volumes, ejection fraction, and sphericity index; in a segment-to-segment comparison, RT3DE was shown to be accurate also for the analysis of wall motion abnormalities (k=0.62) and LV regional thickness (k=0.56) as a marker of myocardial scar. In contrast, two-dimensional echocardiography significantly underestimated these variables. Furthermore, mitral regurgitant volume assessed by RT3DE showed excellent correlation (r=0.93) with regurgitant volume measured by MRI, without significant bias (=-0.7 mL/beat).

CONCLUSIONS

In the management of heart failure patients with LV aneurysm, RT3DE provides an accurate and comprehensive assessment, including quantification of LV size, shape, global systolic function, regional wall motion, and myocardial scar together with precise evaluation of the severity of mitral regurgitation.