Twist and Untwist Mechanics of the Left Ventricle

Alveolar Microdynamics during Tidal Ventilation in Live Animals Imaged by SPring-8 Synchrotron

It is self-evident that our chests expand and contract during breathing but, surprisingly, exactly how individual alveoli change shape over the respiratory cycle is still a matter of debate. Some argue that all the alveoli expand and contract rhythmically. Others claim that the lung volume change is due to groups of alveoli collapsing and reopening during ventilation. Although this question might seem to be an insignificant detail for healthy individuals, it might be a matter of life and death for patients with compromised lungs. Past analyses were based on static post-mortem preparations primarily due to technological limitations, and therefore, by definition, incapable of providing dynamic information. In contrast, this study provides the first comprehensive dynamic data on how the shape of the alveoli changes, and, further, provides valuable insights into the optimal lung volume for efficient gas exchange. It is concluded that alveolar micro-dynamics is nonlinear; and at medium lung volume, alveoli expand more than the ducts.

Left ventricular trabeculation in Hominidae: divergence of the human cardiac phenotype

Although the gross morphology of the heart is conserved across mammals, subtle interspecific variations exist in the cardiac phenotype, which may reflect evolutionary divergence among closely-related species. Here, we compare the left ventricle (LV) across all extant members of the Hominidae taxon, using 2D echocardiography, to gain insight into the evolution of the human heart. We present compelling evidence that the human LV has diverged away from a more trabeculated phenotype present in all other great apes, towards a ventricular wall with proportionally greater compact myocardium, which was corroborated by post-mortem chimpanzee (Pan troglodytes) hearts. Speckle-tracking echocardiographic analyses identified a negative curvilinear relationship between the degree of trabeculation and LV systolic twist, revealing lower rotational mechanics in the trabeculated non-human great ape LV. This divergent evolution of the human heart may have facilitated the augmentation of cardiac output to support the metabolic and thermoregulatory demands of the human ecological niche.

Evaluation of left ventricular blood flow kinetic energy in patients with acute myocardial infarction by 4D Flow MRI: a preliminary study

PURPOSE

To evaluate the intracavity left ventricular (LV) blood flow kinetic energy (KE) parameters using four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) in patients with acute myocardial infarction (AMI).

METHODS

Thirty AMI patients and twenty controls were examined via CMR, which included cine imaging, late gadolinium enhancement (LGE) and global heart 4D flow imaging. The KE parameters were indexed to LV end-diastolic volume (EDV) to obtain average, systolic and diastolic KE as well as the proportion of LV in-plane KE (%). These parameters were compared between the AMI patients and controls and between the two subgroups.

RESULTS

Analysis of the LV blood flow KE parameters at different levels of the LV cavity and in different segments of the same level showed that the basal level had the highest blood flow KE while the apical level had the lowest in the control group. There were no significant differences in diastolic KE, systolic in-plane KE and diastolic in-plane KE between the anterior wall and posterior wall (p > 0.05), only the systolic KE had a significant difference between them (p < 0.05). Compared with those in the control group, the average (10.7 ± 3.3 µJ/mL vs. 14.7 ± 3.6 µJ/mL, p < 0.001), systolic (14.6 ± 5.1 µJ/mL vs. 18.9 ± 3.9 µJ/mL, p = 0.003) and diastolic KE (7.9 ± 2.5 µJ/mL vs. 10.6 ± 3.8 µJ/mL, p = 0.018) were significantly lower in the AMI group. The average KE in the infarct segment was lower than that in the noninfarct segment in the AMI group (49.5 ± 18.7 µJ/mL vs. 126.3 ± 50.7 µJ/mL, p < 0.001), while the proportion of systolic in-plane KE increased significantly (61.8%±11.5 vs. 42.9%±14.4, p = 0.001).

CONCLUSION

The 4D Flow MRI technique can be used to quantitatively evaluate LV regional hemodynamic parameters. There were differences in the KE parameters of LV blood flow at different levels and in different segments of the same level in healthy people. In AMI patients, the average KE of the infarct segment decreased, while the proportion of systolic in-plane KE significantly increased.

Torsional and strain dysfunction precede overt heart failure in a mouse model of dilated cardiomyopathy pathogenesis

Detailed assessments of whole heart mechanics are crucial for understanding the consequences of sarcomere perturbations that lead to cardiomyopathy in mice. Echocardiography offers an accessible and cost-effective method of obtaining metrics of cardiac function, but the most routine imaging and analysis protocols might not identify subtle mechanical deficiencies. This study aims to use advanced echocardiography imaging and analysis techniques to identify previously unappreciated mechanical deficiencies in a mouse model of dilated cardiomyopathy (DCM) before the onset of overt systolic heart failure (HF). Mice lacking muscle LIM protein expression (MLP-/-) were used to model DCM-linked HF pathogenesis. Left ventricular (LV) function of MLP-/- and wild-type (WT) controls were studied at 3, 6, and 10 wk of age using conventional and four-dimensional (4-D) echocardiography, followed by speckle-tracking analysis to assess torsional and strain mechanics. Mice were also studied with RNA-seq. Although 3-wk-old MLP-/- mice showed normal LV ejection fraction (LVEF), these mice displayed abnormal torsional and strain mechanics alongside reduced β-adrenergic reserve. Transcriptome analysis showed that these defects preceded most molecular markers of HF. However, these markers became upregulated as MLP-/- mice aged and developed overt systolic dysfunction. These findings indicate that subtle deficiencies in LV mechanics, undetected by LVEF and conventional molecular markers, may act as pathogenic stimuli in DCM-linked HF. Using these analyses in future studies will further help connect in vitro measurements of the sarcomere function to whole heart function.NEW & NOTEWORTHY A detailed study of how perturbations to sarcomere proteins impact whole heart mechanics in mouse models is a major yet challenging step in furthering our understanding of cardiovascular pathophysiology. This study uses advanced echocardiographic imaging and analysis techniques to reveal previously unappreciated subclinical whole heart mechanical defects in a mouse model of cardiomyopathy. In doing so, it offers an accessible set of measurements for future studies to use when connecting sarcomere and whole heart function.

Association between basal septal hypertrophy and left ventricular geometry in a community population

BACKGROUND

Left ventricular (LV) geometry is closely associated with cardiovascular disease; however, few studies have evaluated the relationship between basal septal hypertrophy (BSH) and LV geometry. In this study, we examined the relationship between BSH and LV geometry in a Beijing community population.

METHODS

The clinical and echocardiographic data of 1032 participants from a community in Beijing were analyzed. BSH was defined as a basal interventricular septal thickness ≥ 14 mm and a basal septal thickness/mid-septal thickness ≥ 1.3. On the basis of their echocardiographic characteristics, patients were described as having a normal geometry, concentric remodeling, concentric hypertrophy, or eccentric hypertrophy. Multivariable logistic regression was used to analyze the relationship between BSH, LV mass index (LVMI), and relative wall thickness (RWT).

RESULTS

The prevalence of BSH was 7.4% (95% confidence interval [CI] 5.8-9.0%). Basal and middle interventricular septal thickness, LV posterior wall thickness, and RWT were greater, while LVMI and LV end-diastolic dimension were lower in the BSH group than in the non-BSH group (p < 0.05). The BSH group accounted for the highest proportion of patients with concentric remodeling. A multivariable regression analysis showed that BSH increased by 3.99-times (odds ratio [OR] 3.99, 95% CI 2.05-7.78, p < 0.01) when RWT was > 0.42, but not when LVMI increased (OR 0.16, 95% CI 0.02-1.19, p = 0.07). There were no interactions between BSH and age, body mass index, sex, diabetes mellitus, coronary heart disease, stroke, and smoking in relation to an RWT > 0.42.

CONCLUSION

BSH was independently associated with an RWT > 0.42.

Actuators for Implantable Devices: A Broad View

The choice of actuators dictates how an implantable biomedical device moves. Specifically, the concept of implantable robots consists of the three pillars: actuators, sensors, and powering. Robotic devices that require active motion are driven by a biocompatible actuator. Depending on the actuating mechanism, different types of actuators vary remarkably in strain/stress output, frequency, power consumption, and durability. Most reviews to date focus on specific type of actuating mechanism (electric, photonic, electrothermal, etc.) for biomedical applications. With a rapidly expanding library of novel actuators, however, the granular boundaries between subcategories turns the selection of actuators a laborious task, which can be particularly time-consuming to those unfamiliar with actuation. To offer a broad view, this study (1) showcases the recent advances in various types of actuating technologies that can be potentially implemented in vivo, (2) outlines technical advantages and the limitations of each type, and (3) provides use-specific suggestions on actuator choice for applications such as drug delivery, cardiovascular, and endoscopy implants.

A change of heart: mechanisms of cardiac adaptation to acute and chronic hypoxia

Over the last 100 years, high‐altitude researchers have amassed a comprehensive understanding of the global cardiac responses to acute, prolonged and lifelong hypoxia. When lowlanders are exposed to hypoxia, the drop in arterial oxygen content demands an increase in cardiac output, which is facilitated by an elevated heart rate at the same time as ventricular volumes are maintained. As exposure is prolonged, haemoconcentration restores arterial oxygen content, whereas left ventricular filling and stroke volume are lowered as a result of a combination of reduced blood volume and hypoxic pulmonary vasoconstriction. Populations native to high‐altitude, such as the Sherpa in Asia, exhibit unique lifelong or generational adaptations to hypoxia. For example, they have smaller left ventricular volumes compared to lowlanders despite having larger total blood volume. More recent investigations have begun to explore the mechanisms underlying such adaptive responses by combining novel imaging techniques with interventions that manipulate cardiac preload, afterload, and/or contractility. This work has revealed the contributions and interactions of (i) plasma volume constriction; (ii) sympathoexcitation; and (iii) hypoxic pulmonary vasoconstriction with respect to altering cardiac loading, or otherwise preserving or enhancing biventricular systolic and diastolic function even amongst high altitude natives with excessive erythrocytosis. Despite these advances, various areas of investigation remain understudied, including potential sex‐related differences in response to high altitude. Collectively, the available evidence supports the conclusion that the human heart successfully adapts to hypoxia over the short‐ and long‐term, without signs of myocardial dysfunction in healthy humans, except in very rare cases of maladaptation.

Left Ventricular Rotational Abnormalities in Treated Hypopituitarism: Insights From the Three-Dimensional Speckle-Tracking Echocardiographic MAGYAR-Path Study

Introduction: Hypopituitarism is a rare, often underdiagnosed, complex hormonal disease caused by the decreased secretion of one or more hormones in the pituitary gland. The present study was designed to assess left ventricular (LV) rotational mechanics in patients with treated hypopituitarism. It was also aimed to find possible differences in these parameters according to the origin of hypopituitarism (congenital vs. acquired). Methods: The present prospective study involved 35 treated patients with hypopituitarism; however, 4 patients had to be excluded due to inferior image quality. The mean age of the remaining 31 cases was 56.3 ± 13.2 years (18 males). The control group consisted of 29 age- and sex-matched healthy volunteers (mean age: 55.3 ± 4.8 years, 14 males). In all cases a complete two-dimensional echocardiography examination was performed followed by three-dimensional speckle-tracking echocardiography. Results: No significant differences could be found in LV volumes between the controls and patients with hypopituitarism and hypopituitary subgroups. LV apical rotation (8.1 ± 5.1° vs. 10.6 ± 3.5°, p < 0.05) and LV twist (11.9 ± 5.3° vs. 15.1 ± 3.8°, p < 0.05) were impaired in the hypopituitary group with normally directed LV rotational mechanics as compared to the healthy controls. However, 13% of patients showed a near absence of LV twist called LV "rigid body rotation" (LV-RBR). There were no significant differences regarding LV apical and basal rotations and twist between acquired and congenital hypopituitary subgroups. Conclusions: Impaired LV apical rotation and twist could be demonstrated in hypopituitarism regardless of its origin. In the present study with small number of patients with hypopituitarism, LV-RBR was present in 13% of cases.

Understanding the association between endothelial dysfunction and left ventricle diastolic dysfunction in development of coronary artery disease and heart failure

Cardiovascular diseases (CVDs)  have been the most common cause of death worldwide for decades. Until recently the most affected patients were middle-aged and elderly, predominantly men, with more frequent ST elevation myocardial infarction  (STEMI) caused by obstructive coronary artery disease (CAD). However, in the last two decades we have noticed an increased incidence of ischemia with non-obstructive coronary arteries (INOCA), which includes myocardial infarction with non-obstructive coronary arteries (MINOCA) and non-myocardial infarction syndromes, such as microvascular and vasospastic angina, conditions that have been particularly pronounced in women and young adults - the population we considered low-risky till than. Therefore, it has become apparent that for this group of patients conventional methods of assessing the risk of future cardiovascular (CV) events are no longer specific and sensitive enough. Heart failure with preserved ejection fraction (HFpEF) is another disease, the incidence of which has been rising rapidly during last two decades, and predominantly affects elderly population. Although the etiology and pathophysiology of INOCA and HFpEF are complex and not fully understood, there is no doubt that the underlying cause of both conditions is endothelial dysfunction (ED) which further promotes the development of left ventricular diastolic dysfunction (LVDD). Plasma biomarkers of ED, as well as natriuretic peptides (NPs), have been intensively investigated recently, and some of them have great potential for early detection and better assessment of CV risk in the future.

Assessment of left ventricular twist by 3D ballistocardiography and seismocardiography compared with 2D STI echocardiography in a context of enhanced inotropism in healthy subjects

Ballistocardiography (BCG) and Seismocardiography (SCG) assess the vibrations produced by cardiac contraction and blood flow, respectively, by means of micro-accelerometers and micro-gyroscopes. From the BCG and SCG signals, maximal velocities (VMax), integral of kinetic energy (iK), and maximal power (PMax) can be computed as scalar parameters, both in linear and rotational dimensions. Standard echocardiography and 2-dimensional speckle tracking imaging echocardiography were performed on 34 healthy volunteers who were infused with increasing doses of dobutamine (5-10-20 μg/kg/min). Linear VMax of BCG predicts the rates of left ventricular (LV) twisting and untwisting (both p < 0.0001). The linear PMax of both SCG and BCG and the linear iK of BCG are the best predictors of the LV ejection fraction (LVEF) (p < 0.0001). This result is further confirmed by mathematical models combining the metrics from SCG and BCG signals with heart rate, in which both linear PMax and iK strongly correlate with LVEF (R = 0.7, p < 0.0001). In this setting of enhanced inotropism, the linear VMax of BCG, rather than the VMax of SCG, is the metric which best explains the LV twist mechanics, in particular the rates of twisting and untwisting. PMax and iK metrics are strongly associated with the LVEF and account for 50% of the variance of the LVEF.

Impact of Right Ventricular Function on Left Ventricular Torsion and Ventricular Deformations in Pulmonary Artery Hypertension Patients

INTRODUCTION

Ventricular interdependence in pulmonary arterial hypertension (PAH) by the use of most recent echocardiographic techniques is still rare. The current case-controlled study aims to assess left ventricular (LV) torsion in patients with PAH.

METHODS

The study included 42 cases of moderate to severe PAH and 42 age and gender-matched healthy controls between March 2016 and January 2018. All the patients and controls undergo routine practice echocardiography using the Vivid 7-echocardiography (2.5MHz transducer) system.

RESULTS

The LV twisting parameters, peak basal rotation, peak apical rotation, and twist were similar among both cases and controls, however, LV torsion was significantly (p=0.04) impacted. Right ventricular (RV) longitudinal deformation was clinically significant in the cases compared to controls: RV systolic strain imaging (p=0.001, 95% CI-9.75 to -2.65), RV systolic strain rate (p=0.01, 95% CI-0.99 to -0.09), and RV late diastolic strain rate (p=0.01, 95% CI-0.64 to -0.85). Although PAH did not impact longitudinal LV deformations significantly. At basal level circumferential strain and strain rate were significantly impacted (p=0.005, 95% CI-4.38 to -0.70; p=0.004, 95% CI-0.35 to -0.07) in the PAH group, while the radial strain was preserved. All RV echocardiographic parameters and LV end-diastolic dimension, LV end-systolic volume in the PAH were affected significantly (p=0.002, 95% CI-19.91 to -4.46; p=0.01, 95% CI-8.44 to -2.77). However, only a weak correlation (p=0.05, r =-0.20) was found between tricuspid annular plane systolic excursion and LV Tei index.

CONCLUSION

RV pressure overload directly affects RV longitudinal systolic deformation further influences the interventricular septal and LV geometry, which impaired LV torsion.

Sex Differences in Cardiovascular Aging and Heart Failure

PURPOSE OF THE REVIEW

This review summarizes sex-related changes in the heart and vasculature that occur with aging, both in the presence and absence of cardiovascular disease (CVD).

RECENT FINDINGS

In the presence of CVD risk factors and/or overt CVD, sex-specific changes in the number of cardiomyocytes, extent of the myocardial extracellular matrix, and myocellular hypertrophy promote unique patterns of LV remodeling in men and women. In addition, age- and sex-specific vascular stiffening is also well established, driven by changes in endothelial dysfunction, elastin-collagen content, microvascular dysfunction, and neurohormonal signaling. Together, these changes in LV chamber geometry and morphology, coupled with heightened vascular stiffness, appear to drive both age-related increases in systolic function and declines in diastolic function, particularly in postmenopausal women. Accordingly, estrogen has been implicated as a key mediator, given its direct vasodilating properties, association with nitric oxide excretion, and involvement in myocellular Ca2+ handling, mitochondrial energy production, and oxidative stress. The culmination of the abovementioned sex-specific cardiac and vascular changes across the lifespan provides important insight into heart failure development, particularly of the preserved ejection fraction variety, while offering promise for future preventive strategies and therapeutic approaches.

Myocardial strain indices and coronary flow reserve are only mildly affected in healthy hypertensive patients

To investigate changes in two-dimensional myocardial strain echocardiography (2DSTE) indices following a dipyridamole stress test (DIPSE) in relatively healthy hypertensive patients and healthy controls. Forty-seven male hypertensive patients (aged 57±9 years) with normal ejection fraction and without left ventricular (LV) hypertrophy and 20 healthy male subjects were studied with conventional and 2DSTE echocardiography at rest and post DIPSE. Coronary flow reserve (CFR) in the left anterior descending artery following DIPSE was also evaluated. Global longitudinal strain (GLS) and TWIST were higher while UNTWIST rate was lower in hypertensives versus controls (p < 0.05 for all); TWIST remained higher in hypertensives (p = 0.021) after adjustment for differences in age and body mass index (BMI) between the groups. CFR was higher in controls compared to hypertensives even after adjustment for confounders (4.14 vs. 2.53, p = 0.001). DIPSE-induced changes did not differ between the groups after adjustment for age and BMI (p > 0.05 for all). DIPSE-induced improvement in GLS was associated with higher CFR only in hypertensive patients (r - 0.372, p = 0.010). The current study showed that well controlled hypertensive patients have only mild echocardiographic differences compared to controls; some of these differences appear to depend on age and BMI. A 'hyper-rotation' phenomenon (i.e. higher TWIST) early in hypertension may be a compensatory mechanism to preserve global systolic LV function. Coronary microcirculatory function was impaired in hypertensive patients, albeit within normal range, and was associated with DIPSE-induced changes in myocardial long-axis systolic function.

Left Ventricular Twist Is Augmented in Hypoxia by β1-Adrenergic-Dependent and β1-Adrenergic-Independent Factors, Without Evidence of Endocardial Dysfunction

BACKGROUND

Left ventricular (LV) twist mechanics are augmented with both acute and chronic hypoxemia. Although the underlying mechanisms remain unknown, sympathetic activation and a direct effect of hypoxemia on the myocardium have been proposed, the latter of which may produce subendocardial dysfunction that is masked by larger subepicardial torque. This study therefore sought to (1) determine the individual and combined influences of β₁-AR (β₁-adrenergic receptor) stimulation and peripheral O₂ saturation (Spo₂) on LV twist in acute and chronic hypoxia and (2) elucidate whether endocardial versus epicardial mechanics respond differently to hypoxia.

METHODS

Twelve males (27±4 years) were tested near sea level in acute hypoxia (Spo₂=82±4%) and following 3 to 6 days at 5050 m (high altitude; Spo₂=83±3%). In both settings, participants received infusions of β₁-AR blocker esmolol and volume-matched saline (double-blind, randomized). LV mechanics were assessed with 2-dimensional speckle-tracking echocardiography, and region-specific analysis to compare subendocardial and subepicardial mechanics.

RESULTS

At sea level, compared with baseline (14.8±3.0°) LV twist was reduced with esmolol (11.2±3.3°; P=0.007) and augmented during hypoxia (19.6±4.9°; P<0.001), whereas esmolol+hypoxia augmented twist compared with esmolol alone (16.5±3.3°; P<0.001). At 5050 m, LV twist was increased compared with sea level (19.5±5.4°; P=0.004), and reduced with esmolol (13.0±3.8°; P<0.001) and Spo₂ normalization (12.8±3.4°; P<0.001). Moreover, esmolol+normalized Spo₂ lowered twist further than esmolol alone (10.5±3.1°; P=0.036). There was no mechanics-derived evidence of endocardial dysfunction with hypoxia at sea level or high altitude.

CONCLUSIONS

These findings suggest LV twist is augmented in hypoxia via β₁-AR-dependent and β₁-AR-independent mechanisms (eg, α₁-AR stimulation), but does not appear to reflect endocardial dysfunction.

Left ventricular torsional mechanics in term fetuses and neonates

OBJECTIVE

Left ventricular (LV) torsion is an important aspect of cardiac mechanics and is fundamental to normal ventricular function. The myocardial mechanics of the fetal heart and the changes that occur during the transition to the neonatal period have not been explored previously. The aim of this study was to evaluate perinatal changes in LV torsion and its relationship with myocardial function.

METHODS

This was a prospective study of 36 women with an uncomplicated term pregnancy. Fetal and neonatal conventional, spectral tissue Doppler and two-dimensional (2D) speckle tracking echocardiography were performed a few days before and within hours after delivery to measure cardiac indices including LV rotational parameters derived from short-axis views at the base and apex of the heart. Linear regression analysis was used to examine the relationship between LV rotational parameters and cardiac geometric and functional indices in term fetuses and neonates. Perinatal changes in LV rotational parameters were assessed.

RESULTS

There were three patterns of LV twist in term fetuses: those with reversed-apex-type LV twist had the lowest median values of LV torsion (0.1°/cm), with higher values (1.6°/cm) in those with infant-type LV twist and the highest values (4.4°/cm) in those with adult-type LV twist. LV torsion was associated significantly with cardiac geometric and functional indices. Perinatal evaluation revealed a significant increase in LV torsion following delivery in fetuses exhibiting reversed-apex-type LV twist (increase of 2.8°/cm, P = 0.009) and a significant decrease in those with adult-type LV twist (decrease of 3.2°/cm, P = 0.008).

CONCLUSIONS

This study demonstrates the feasibility of 2D speckle tracking imaging for accurate assessment of rotational cardiac parameters in term fetuses. There are unique perinatal patterns of LV twist that demonstrate different values of LV torsion, which was found to correlate with indices of ventricular geometry and myocardial function. Differences in patterns of LV twist may therefore reflect differences in compensatory myocardial adaptation to the physiological environment/loading conditions in late gestation in fetuses and postnatal cardiac adjustment to the acute loading changes that occur at delivery. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Sex-related Left Ventricle Rotational and Torsional Mechanics by Block Matching Algorithm

Background:

The aim of the present study was to evaluate how left ventricular twist and torsion are associated with sex between sex groups of the same age.

Materials and Methods:

In this analytical study, twenty one healthy subjects were scanned in left ventricle basal and apical short axis views to run the block matching algorithm; instantaneous changes in the base and apex rotation angels were estimated by this algorithm and then instantaneous changes of the twist and torsion were calculated over the cardiac cycle.

Results:

The rotation amount between the consecutive frames in basal and apical levels was extracted from short axis views by tracking the speckle pattern of images. The maximum basal rotation angle for men and women were -6.94°±1.84 and 9.85°±2.36 degrees (p-value = 0.054), respectively. Apex maximum rotation for men was -8.89°±2.04 and for women was 12.18°±2.33 (p-value < 0.05). The peak of twist angle for men and women was 16.78 ± 1.83 and 20.95± 2.09 degrees (p-value < 0.05), respectively. In men and women groups, the peak of calculated torsion angle was 5.49°±1.04 and 7.12± 1.38 degrees (p-value < 0.05), respectively.

Conclusion:

The conclusion is that although torsion is an efficient parameter for left ventricle function assessment, because it can take in account the heart diameter and length, statistic evaluation of the results shows that among men and women LV mechanical parameters are significantly different. This study was mainly ascribed to the dependency of the torsion and twist on patient sex.

Design, simulation, and fabrication of a three-dimensional printed pump mimicking the left ventricle motion

The development of accurate replicas of the circulatory and cardiac system is fundamental for a deeper understanding of cardiovascular diseases and the testing of new devices. Although numerous works concerning mock circulatory loops are present in the current state of the art, still some limitations are present. In particular, a pumping system able to reproduce the left ventricle motion and completely compatible with the magnetic resonance environment to permit the four-dimensional flow monitoring is still missing. The aim of this work was to evaluate the feasibility of an actuator suitable for cardiovascular mock circuits. Particular attention was given to the ability to mimic the left ventricle dynamics including both compression and twisting with the magnetic resonance compatibility. In our study, a left ventricle model to be actuated through vacuum was designed. The realization of the system was evaluated with finite element analysis of different design solutions. After the in silico evaluation phase, the most suitable design in terms of physiological values reproduction was fabricated through three-dimensional printing for in vitro validation. A pneumatic experimental setup was developed to evaluate the pump performances in terms of actuation, in particular ventricle radial and longitudinal displacement, twist rotation, and ejection fraction. The study demonstrated the feasibility of a custom pneumatic pump for mock circulatory loops able to reproduce the physiological ventricle movement and completely suitable for the magnetic resonance environment.

Computational modeling of human left ventricle to assess the role of trabeculae carneae on the diastolic and systolic functions

Trabeculae carneae are irregular structures that cover the endocardial surfaces of both ventricles and account for a significant portion of human ventricular mass. The role of trabeculae carneae in diastolic and systolic functions of the left ventricle (LV) is not well understood. Thus, the objective of this study was to investigate the functional role of trabeculae carneae in the LV. Finite element analyses of ventricular functions were conducted for three different models of human LV derived from high-resolution magnetic resonance imaging (MRI). The first model comprised trabeculae carneae and papillary muscles, while the second model had papillary muscles and partial trabeculae carneae, and the third model had a smooth endocardial surface. We customized these patient-specific models with myofiber architecture generated with a rule-based algorithm, diastolic material parameters using Fung strain energy function derived from bi-axial tests and adjusted with the empirical Klotz relationship, and myocardial contractility constants optimized for average normal ejection fraction of the human LV. Results showed that the partial trabeculae cutting model had enlarged end-diastolic volume, reduced wall stiffness and even increased end-systolic function, indicating that the absence of trabeculae carneae increased the compliance of the LV during diastole, while maintaining systolic function.

Invited Article: Emerging soft bioelectronics for cardiac health diagnosis and treatment

Cardiovascular diseases are among the leading causes of death worldwide. Conventional technologies for diagnosing and treating lack the compliance and comfort necessary for those living with life-threatening conditions. Soft electronics presents a promising outlet for conformal, flexible, and stretchable devices that can overcome the mechanical mismatch that is often associated with conventional technologies. Here, we review the various methods in which electronics have been made flexible and stretchable, to better interface with the human body, both externally with the skin and internally with the outer surface of the heart. Then, we review soft, wearable, noninvasive heart monitors designed to be attached to the chest or other parts of the body for mechano-acoustic and electrophysiological sensing. A common method of treatment for various abnormal heart rhythms involves catheter ablation procedures and we review the current soft bioelectronics that can be placed on the balloon or head of the catheter. Cardiac mapping is integral to determine the state of the heart; we discuss the various parameters for sensing aside from electrophysiological sensing, such as temperature, pH, strain, and tactile sensing. Finally, we review the soft devices that harvest energy from the natural and spontaneous beating of the heart by converting its mechanical motion into electrical energy to power implants.

Abnormalities in Left Ventricular Rotation Are Inherent in Young Children with Repaired Tetralogy of Fallot and Are Independent of Right Ventricular Dilation

Left ventricular (LV) dysfunction is a risk factor for adverse outcomes in older children and adults with repaired Tetralogy of Fallot (rToF). Pulmonary regurgitation (PR), right ventricular (RV) dilation, and dysfunction have been shown to result in abnormal LV myocardial mechanics and dysfunction. The aim of our study was to evaluate LV rotational mechanics, especially apical rotation in young children with rToF with and without RV dilation. This is a retrospective, single center study in 28 asymptomatic young children with rToF (16 with RV dilation; 12 without RV dilation); 29 age-matched normal controls. RV and LV systolic and diastolic function was studied using conventional two-dimensional echocardiography (2DE) and speckle tracking echocardiography (STE). Rotational mechanics studied included basal and apical rotation (BR, AR), peak twist (calculated by difference between the apical and basal rotation), twist rate (TR), and untwist rate (UnTR). The mean age of the cohort was 4.7 years (± 2.3). Abnormal AR, BR, TR, and UnTR were noted in patients with rToF. The abnormalities were significant in magnitude as well as the direction of rotation; more pronounced in the absence of RV dilation. LV systolic and diastolic dysfunction as evidenced by abnormal AR and degree of untwist is inherent in rToF and not associated with RV dilation in rToF children. Abnormal BR may reflect a lack of maturation to adult type of rotational mechanics. Further longitudinal studies are required to study the progression of these abnormalities and their correlation with clinical outcomes.

Soft robotic sleeve supports heart function

There is much interest in form-fitting, low-modulus, implantable devices or soft robots that can mimic or assist in complex biological functions such as the contraction of heart muscle. We present a soft robotic sleeve that is implanted around the heart and actively compresses and twists to act as a cardiac ventricular assist device. The sleeve does not contact blood, obviating the need for anticoagulation therapy or blood thinners, and reduces complications with current ventricular assist devices, such as clotting and infection. Our approach used a biologically inspired design to orient individual contracting elements or actuators in a layered helical and circumferential fashion, mimicking the orientation of the outer two muscle layers of the mammalian heart. The resulting implantable soft robot mimicked the form and function of the native heart, with a stiffness value of the same order of magnitude as that of the heart tissue. We demonstrated feasibility of this soft sleeve device for supporting heart function in a porcine model of acute heart failure. The soft robotic sleeve can be customized to patient-specific needs and may have the potential to act as a bridge to transplant for patients with heart failure.

Effect of exercise training on left ventricular mechanics after acute myocardial infarction-an exploratory study

BACKGROUND

Cardiac rehabilitation (CR) exercise training is beneficial after myocardial infarction (MI). Whilst the peripheral adaptations to training are well defined, little is known regarding the effect on left ventricular (LV) remodelling, particularly LV function. Efficient LV ejection and filling is achieved through deformation and rotation of the myocardium in systole and diastole - LV mechanics. The response of LV mechanics to CR exercise training in MI patients is unknown.

METHODS

In this observational exploratory study, 36 (of 40 enrolled) male, MI patients completed either 10-weeks of twice-weekly gym based cardiovascular exercise at 60-80% VO_2peak (n=18), or a non-exercise control period (n=18). Cardiopulmonary exercise testing and speckle tracking echocardiography were performed at baseline and 10 weeks.

RESULTS

Compared to the non-exercise group, VO_2peak improved with CR exercise training (Difference: +4.28 [95% CI: 1.34 to 7.23] ml.kg^-1.min^-1, P=0.01). Neither conventional LV structural or functional indices, nor LV global longitudinal strain, significantly changed in either group. In contrast, LV twist and twist velocity decreased in the exercise group and increased in the non-exercise group (Difference: -3.95° [95% CI: -7.92 to 0.03°], P=0.05 and -19.2°.s^-1 [95% CI: -35.9 to -2.7°.s^-1], P=0.02, respectively).

CONCLUSION

In MI patients who completed CR exercise training, LV twist and twist velocity decreased, whereas these parameters increased in patients who did not exercise. These preliminary data may indicate reverse LV functional remodelling and improved functional reserve. The assessment of LV twist may serve as an indicator of the therapeutic benefit of CR exercise training and should be investigated in larger trials.

New Cardiac Imaging Algorithms to Diagnose Constrictive Pericarditis Versus Restrictive Cardiomyopathy

PURPOSE OF REVIEW

Echocardiography is the mainstay in the diagnostic evaluation of constrictive pericarditis (CP) and restrictive cardiomyopathy (RCM), but no single echocardiographic parameter is sufficiently robust to accurately distinguish between the two conditions. The present review summarizes the recent advances in echocardiography that promise to improve its diagnostic performance for this purpose. The role of other imaging modalities such as cardiac computed tomography, magnetic resonance imaging, and invasive hemodynamic assessment in the overall diagnostic approach is also discussed briefly.

RECENT FINDINGS

A recent study has demonstrated improved diagnostic accuracy of echocardiography with integration of multiple conventional echocardiographic parameters in to a step-wise algorithm. Concurrently, the studies using speckle-tracking echocardiography have revealed distinct and disparate patterns of myocardial mechanical abnormalities in CP and RCM with their ability to distinguish between the two conditions. The incorporation of machine-learning algorithms into echocardiography workflow permits easy integration of the wealth of the diagnostic data available and promises to further enhance the diagnostic accuracy of echocardiography. New imaging algorithms are continuously being evolved to permit accurate distinction between CP and RCM. Further research is needed to validate the accuracy of these newer algorithms and to define their place in the overall diagnostic approach for this purpose.

Early detection of left ventricular diastolic dysfunction using conventional and speckle tracking echocardiography in a large animal model of metabolic dysfunction

Left ventricular (LV) diastolic dysfunction is one of the important mechanisms responsible for symptoms in patients with heart failure. The aim of the current study was to identify parameters that may be used to detect early signs of LV diastolic dysfunction in diabetic pigs on a high fat diet, using conventional and speckle tracking echocardiography. The study population consisted of 16 healthy Göttingen minipigs and 18 minipigs with experimentally induced metabolic dysfunction. Echocardiography measurements were performed at baseline and 3-month follow-up. The ratio of peak early (E) and late filling velocity (E/A ratio) and the ratio of E and the velocity of the mitral annulus early diastolic wave (E/Em ratio) did not change significantly in both groups. Peak untwisting velocity decreased in the metabolic dysfunction group (- 30.1 ± 18.5 vs. - 23.4 ± 15.5 °/ms) but not in controls (- 38.1 ± 23.6 vs. - 42.2 ± 23.0 °/ms), being significantly different between the groups at the 3-month time point (p < 0.05). In conclusion, whereas E/A ratio and E/Em ratio did not change significantly after 3 months of metabolic dysfunction, peak untwisting velocity was significantly decreased. Hence, peak untwisting velocity may serve as an important marker to detect early changes of LV diastolic dysfunction.

Left ventricular torsion assessed by two-dimensional echocardiography speckle tracking as a predictor of left ventricular remodeling and short-term outcome following primary percutaneous coronary intervention for acute myocardial infarction: A single-center experience

AIMS

Left ventricular (LV) torsion is a novel method to assess systolic LV function. This study aimed at exploring the utility of 2D speckle tracking-based assessment of left ventricular torsion in patients with acute myocardial infarction (AMI) undertaking primary percutaneous intervention (pPCI) in predicting left ventricular remodeling.

METHODS AND RESULTS

The study included 115 patients (mean±SD, age 52.2±9.67, males 84.3%) who underwent pPCI for AMI. Echocardiographic assessment of LV torsion by two-dimensional speckle tracking was performed early after the index pPCI. Patients underwent repeat echocardiography at 6 months to detect remodeling. LV torsion in the acute setting was significantly lower in those who demonstrated LV remodeling at follow-up compared to those without remodeling (7.56±1.95 vs 15.16±4.65; P<.005). Multivariate analysis identified peak CK & CK-MB elevation (β=-0.767 and -0.725; P<.001), SWMA index (β=-0.843; P<.001), and Simpson's derived LV ejection fraction (LVEF; β=0.802; P<.001) as independent predictors of baseline LV torsion. It also identified peak LV torsion (β: 0.27; 95% CI: 0.15-0.5, P=.001) and SWMA index (β: 1.07, 95% CI: 1.03-1.12, P=.005) as independent predictors of LV remodeling. Baseline Killip's grades II and higher (β: 48.6; 95% CI 5.5-428, P<.001) and diabetes mellitus (β: 29.7; 95% CI 1.1-763, P<.05) were independent predictors of mortality.

CONCLUSION

Left ventricular torsion in acute MI setting is impaired and predicts subsequent LV remodeling at 6-month follow-up.

Longitudinal rotation: a new way to detect the cardiotoxicity of anthracycline-based chemotherapy in breast cancer patients

Background and aims

The study was to compare cardiac parameters before and after anthracycline-based chemotherapy and identify a parameter for detecting cardiotoxicity in breast cancer patients.

Methods

Cardiac function in 43 female breast cancer patients was evaluated at three time points: baseline, 1-3 days before the initiation of anthracycline-based chemotherapy; 3 weeks and 6 months after the final cycle of chemotherapy. At each visit, the peak longitudinal velocity; strain rate; peak systolic strain; peak systolic longitudinal displacement, and segmental and global longitudinal rotation degrees of the left ventricular were measured.

Results

The peak early-diastole left ventricular wall velocity at baseline was significantly higher than the values at 3 weeks and 6 months after the final cycle of chemotherapy. The absolute value of the lateral wall peak systolic longitudinal rotation degrees was significantly higher at baseline than at 3 weeks and 6 months after the final cycle of chemotherapy, whereas the absolute value of the global peak systolic longitudinal rotation degrees at baseline was significantly lower than the values at 3 weeks and 6 months after the final cycle of chemotherapy. None of the measured parameters differed significantly between the 3 weeks and 6 months after the final cycle of chemotherapy.

Conclusions

Cardiac diastolic and systolic dysfunction was found after anthracycline-based chemotherapy in this study, and the peak systolic longitudinal rotation degrees can be used to detect dysfunction after chemotherapy. The cardiotoxicity of epirubicin-based chemotherapy is stronger than that of therarubicin-based chemotherapy.

Directional analysis of cardiac motion field from gated fluorodeoxyglucose PET images using the Discrete Helmholtz Hodge Decomposition

OBJECTIVES

Extract directional information related to left ventricular (LV) rotation and torsion from a 4D PET motion field using the Discrete Helmholtz Hodge Decomposition (DHHD).

MATERIALS AND METHODS

Synthetic motion fields were created using superposition of rotational and radial field components and cardiac fields produced using optical flow from a control and patient image. These were decomposed into curl-free (CF) and divergence-free (DF) components using the DHHD.

RESULTS

Synthetic radial components were present in the CF field and synthetic rotational components in the DF field, with each retaining its center position, direction of motion and diameter after decomposition. Direction of rotation at apex and base for the control field were in opposite directions during systole, reversing during diastole. The patient DF field had little overall rotation with several small rotators.

CONCLUSIONS

The decomposition of the LV motion field into directional components could assist quantification of LV torsion, but further processing stages seem necessary.

Delayed and decreased LV untwist and unstrain rate in mutation carriers for hypertrophic cardiomyopathy

Background

The echocardiographic focus to detect abnormalities in genetically hypertrophic cardiomyopathy (HCM) affected subjects without left ventricular (LV) hypertrophy (G+/LVH-) has been on diastolic abnormalities in transmitral flow and longitudinal myocardial function with tissue Doppler imaging. The aim of this study was to assess diastolic LV unstrain and untwist.

Methods and results

Forty-one consecutive genotyped family members of HCM patients (mean age 37 ± 11 years, 16 men) and 41 age- and gender-matched healthy volunteers underwent speckle-tracking echocardiography to measure untwist and unstrain. No significant differences between G+/LVH- and control subjects were seen in maximal systolic twist and global longitudinal strain. In diastole, the early peak untwist rate was significantly lower in G+/LVH- subjects compared with control subjects (62 ± 19°s - 1 vs. 76 ± 30°s - 1, P <0.05), whereas the late peak untwist rate tended to be higher. Untwist from maximal twist until the first 20% of diastole was delayed in G+/LVH- subjects (39.3 ± 12.9% vs. 51.3 ± 15.6%, P <0.005). Late diastolic unstrain rate was significantly higher in G+/LVH- subjects in the inferoseptal wall (111 ± 33 s - 1 vs. 94 ± 32 s - 1, P = 0.024), the inferolateral wall (105 ± 42 vs. 75 ± 35 s - 1, P = 0.007) and the anteroseptal wall (97 ± 26 vs. 80 ± 23 s - 1, P = 0.010). Unstrain from maximal twist until the first 20% of diastole was delayed in G+/LVH- subjects in the inferoseptal (18.9 ± 14.0% vs. 30.1 ± 17.7%, P = 0.005), inferolateral (27.1 ± 16.3% vs. 39.2 ± 18.0%, P = 0.015) and anteroseptal (19.1 ± 14.7% vs. 35.8 ± 18.5%, P = 0.0003) segments.

Conclusions

In mutation carriers, for HCM LV, untwist and unstrain are delayed and untwist rate and unstrain rate are decreased.

Time series analysis of physiologic left ventricular reconstruction in ischemic cardiomyopathy

OBJECTIVE

The history of left ventricular reconstruction has demonstrated that the full spectrum of recoverable physiologic parameters is essential for a good functional result. We report the long-term outcome of a new surgical technique that arranges myocardial fibers in a near-normal disposition, also recovering left ventricular twisting.

METHODS

Between May 2006 and October 2013, 29 consecutive patients with previous anterior myocardial infarction and heart failure symptoms underwent physiologic left ventricular reconstruction surgery and coronary revascularization. Patients were examined by means of standard echocardiography and 2-dimensional speckle tracking at 8 time steps until 7 years after surgery. Ten geometric and functional parameters were evaluated at each step and analyzed by the linear mixed model test.

RESULTS

Hospital mortality was 0%. The mean percentage of indexed end-diastolic and end-systolic volume reduction was 45.7% and 50.9%, respectively. Ejection fraction and all of the volumes were significantly different in the postoperative period with a steady correction during time. Diastolic parameters were not worsened by surgical reconstruction. Ejection fraction and deceleration time showed a significant improvement during time. Left ventricular torsion increased immediately after the surgical correction from 2.8 ± 4.4 degrees to 8.7 ± 3.9 degrees (P = .02) and was still present 4 years after surgery.

CONCLUSIONS

Surgical conduction of ventricular reconstruction should be standardized to achieve the full spectrum of recoverable physiologic parameters. The renewal of ventricular torsion should be pursued as an adjunctive element of ventricular efficiency, mainly in ventricles that work at a critical level in the Frank-Starling relationship and pressure-volume loop.

Clinical Characteristics and Outcomes of Cardiomyopathy in Barth Syndrome: The UK Experience

Barth syndrome (BTHS) is an X-linked disorder characterised by cardiomyopathy, neutropenia, skeletal myopathy and growth delay. This study describes the UK national clinical experience and outcome of cardiomyopathy in BTHS. The clinical course and echocardiographic changes of all patients with BTHS in the UK were reviewed from 2004 to 2014. In addition, strain analysis using 2D speckle tracking echocardiography was performed to further assess left ventricular function in the most recent follow-up. At last follow-up, 22 of 27 patients were alive with a median age of 12.6 (2.0-23.8) years; seven underwent cardiac transplantation at a median age of 2 (0.33-3.6) years, and five died (18.5%) at a median age of 1.8 (0.02-4.22) years. All deaths were related to cardiomyopathy or its management. Left ventricular diastolic dimension and systolic function measured by fractional shortening tended to normalise and stabilise after the first 3 years of life in the majority of patients. However, patients with BTHS (n = 16) had statistically significant reduction in global longitudinal and circumferential strain compared to controls (n = 18), (p < 0.001), despite apparent normal conventional measures of function. There was also reduced or reversed apical rotation and reduced left ventricular twist. Sustained ventricular arrhythmia was not seen at follow-up. Cardiac phenotype in BTHS is variable; however, longer-term outcome in our cohort suggests good prognosis after the first 5 years of life. Most patients appeared to have recovered near normal cardiac function by conventional echocardiographic measures, but strain analysis showed abnormal myocardial deformation and rotational mechanics.

Postnatal neonatal myocardial adaptation is associated with loss of tolerance to tachycardia: a simultaneous invasive and noninvasive assessment

Doppler studies at rest suggest left ventricular (LV) diastolic function rapidly improves from the neonate to infant. Whether this translates to its response to hemodynamic challenges is uncertain. We sought to explore the impact of early LV maturation on its ability to tolerate atrial tachycardia. As tachycardia reduces filling time, we hypothesized that the neonatal LV would be less tolerant of atrial tachycardia. Landrace cross piglets of two age groups (1-3 days; NPs; 14-17 days, YPs; n = 7/group) were instrumented for an atrial pacing protocol (from 200 to 300 beats/min) and assessed by invasive monitoring and echocardiography. NPs maintained their LV output and blood pressure, whereas YPs did not. Although negative dP/dt in NPs at baseline was lower than that of YPs (-1,599 ± 83 vs. -2,470 ± 226 mmHg/s, respectively, P = 0.007), with increasing tachycardia negative dP/dt converged between groups and was not different. Both groups had similar preload reduction during tachycardia; however, NPs maintained shortening fraction while YPs decreased (NPs: 35.4 ± 1.4 vs. 31.8 ± 2.2%, P = 0.35; YPs: 31.4 ± 0.8 vs. 22.9 ± 0.8%, P < 0.001). Contractility measures did not differ between groups. Peak LV twist and untwisting rate also did not differ; however, NPs tended to augment LV twist through increased apical rotation and YPs through increasing basal rotation (P = 0.009). The NPs appear more tolerant of atrial tachycardia than the YPs. They have at least similar diastolic performance, enhanced systolic performance, and different LV twist mechanics, which may contribute to improved tachycardia tolerance of NPs.

The association among age, early mitral leaflet closure, cardiac structure, diastolic indices and NT-proBNP in an asymptomatic Taiwanese population

Background

Advanced age is associated with left ventricular (LV) remodeling and impaired diastole. The association among aging, mitral leaflet closure (EF slope), cardiac structures, and diastolic indices in an asymptomatic Taiwanese population is largely unknown.

Methods

We studied 8103 asymptomatic participants (49.5 ± 11.6 years, 38.2% women) from a health evaluation cohort (2004–2012) in a tertiary center in Taiwan. Echo-derived LV structure/function, and M-mode based EF slope (mm/s) and serum NT-proBNP level were obtained. The association between EF slope and the other clinical or echo-based parameters was investigated.

Results

Average values for EF slope among various age groups in the Taiwanese population were determined for both genders. Advanced age was associated with reductions in EF slope (adjusted estimate: − 0.35/per decade). Reduced EF slope was associated with older age, higher blood pressure and greater body mass index in multivariate models (all p < 0.05). Reduced EF slope was correlated with greater cardiac concentricity, abnormal E′ and E/E′ (AUROC: 0.74 and 0.77, respectively, both p < 0.05) and elevated NT-proBNP (Coef: 5.98 pg/mL, per − 10 mm/s EF slope, 95% CI: 7.82 to 4.17, p < 0.001). EF-slope also clearly discriminated individuals with abnormal estimated LV filling (E/E′ categorized by < 8, ≥ 8 & < 15, ≥ 15, ANOVA p < 0.001).

Conclusions

EF-slope reduction in the asymptomatic Taiwanese population was correlated with age, several unfavorable LV remodeling, and impaired diastolic function parameters, and EF-slope can be an effective clinical diagnostic tool for identifying poor E′ and elevated LV filling pressure. In addition, our data provided reference values for EF-slope in various age groups.

The value of myocardial torsion and aneurysm volume for evaluating cardiac function in rabbit with left ventricular aneurysm

Objective

This study aimed to investigate the effect of left ventricular aneurysm (LVA) volume and left ventricular global torsion on cardiac function by real time three-dimensional echocardiography (RT-3DE) and two-dimensional speckle tracking imaging(2D-STI), to determine the accuracy of RT-3DE and 2D-STI in assessing LV function.

Methods

Thirty New Zealand rabbit models of with LVA were prepared by ligation of the middle segment of the left anterior descending and left circumflex arteries. Four weeks post-procedure, RT-3DE was conducted to obtain data on LVEF, left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and LVA volume (LVAV), Peak rotation angles at the mitral valve annulus level (MV-ROT), peak rotation angles at the apical level (AP-ROT), and left ventricular global torsion angles (LV-TOR) were measured by 2D-STI.

Results

Compared with controls, LVEDV and LVESV were significantly increased in the LVA group, while LVEF, MV-ROT, AP-ROT, and LV-TOR were consistently reduced (p<0.01). Moreover, LVEF correlated with LVA volume and LV torsion angle (r= -0.778 and 0.821, p<0.01). LVA volume/LVEDV had the strongest inverse relationship with LVEF (r= -0.911, p<0.01).

Conclusion

LVA volume, LVA volume/LVEDV, and LV torsion may be used as an indicator for evaluation of cardiac function after LVA. Moreover, LVA volume/LVEDV may be a more sensitive and reliable marker of cardiac function after LVA formation.

Acute Effects of Pacing at Different Ventricular Sites on Left Ventricular Rotational Mechanics in a Porcine Model

OBJECTIVE

The purpose of this study was to examine the acute effects of pacing at different ventricular sites on hemodynamics and left ventricular (LV) rotational mechanics using speckle-tracking echocardiography (STE) in a porcine model.

DESIGN

A prospective laboratory investigation.

SETTING

University research laboratory.

PARTICIPANTS

Yorkshire pigs.

INTERVENTIONS

In 9 pigs, after midline sternotomy, epicardial pacing was performed from the right ventricular outflow tract (RVOT), right ventricular apex (RVA), and LV free wall.

MEASUREMENTS AND MAIN RESULTS

Two-dimensional STE and conductance catheter-derived LV pressure-volume measurements were made to determine the impact of pacing from various sites on LV rotational parameters (twist/untwist) and hemodynamics. RVOT pacing caused the least decrease in end-systolic pressure from baseline (-9.5%), when compared with RVA (-19.1%) and LV (-23.4%). Systolic and diastolic parameters (Emax, Tau) also were different among RVOT (4.7±0.8 mmHg/mL, 32±4 ms), RVA (3.9±0.7 mmHg/mL, 37±6 ms), and LV sites (3.6±0.8 mmHg/mL, 42±7 ms). Similar to the effects of pacing on hemodynamics, RVOT pacing better preserved LV twist (11.1±1.8 v 8.6±1.7, 5.9±0.7 °) and untwisting rate (64.6±8.5 v 56.2±5.3, 48.2±8.5 °/s) when compared with RV apical pacing and LV pacing. Furthermore, prolongation of conduction from LV lateral to anteroseptal at LV base (26.5±3.8 v 13.8±3.3 ms, p<0.05) and LV midpapillary muscle level (35.6±5.6 v 14.1±2.4 ms, p<0.05) was observed with LV pacing compared with RVOT pacing.

CONCLUSIONS

The present data showed that the LV twist/untwist and cardiac systolic and diastolic function were least affected by RVOT pacing. This finding may be explained by the proximity of this location to the native ventricular conduction system.

Disease-specific differences of left ventricular rotational mechanics between cardiac amyloidosis and hypertrophic cardiomyopathy

Left ventricular (LV) twist (LVT) and untwisting (LVUT) rate are global and thorough parameters of LV function. The aim of the present study was to investigate the differences in LV rotational mechanics between patients with cardiac amyloidosis (CA) and hypertrophic cardiomyopathy (HCM). Twenty consecutive patients with CA, 20 consecutive patients with HCM, and 20 consecutive subjects without evidence of structural heart disease were included. Cardiac magnetic resonance (CMR) with late gadolinium enhancement (LGE) imaging was performed to evaluate biventricular function, LV mass index, and presence/extent of LGE. Feature-tracking analysis was applied to LV basal and apical short-axis images to determine peak LVT, time to peak LVT, peak LVUT rate, and time to peak LVUT rate. Peak LVT and peak LVUT rate were significantly impaired in patients with CA compared with controls (P < 0.05 for both). In patients with HCM, peak LVT was increased (P < 0.05) compared with controls, whereas peak LVUT rate was preserved (P > 0.05). Time to peak LVUT rate was significantly prolonged in patients with CA and in patients with HCM compared with controls (ANOVA P < 0.001). At multivariate analysis, age (P = 0.007), LV ejection fraction (P = 0.035) and extent of LGE (P < 0.001) were independently related to peak LVT, and LV mass index (P = 0.015) and extent of LGE (P = 0.004) were independently related to peak LVUT rate, whereas extent of LGE (P < 0.001) was the only variable independently related to time to peak LVUT rate. In conclusion, CA and HCM have specific behavior of LV rotational mechanics. The extent of LGE significantly influences the LV rotational mechanics.

Basal septal hypertrophy

A significant clinical problem is patients presenting with exercise-limiting dyspnoea, sometimes with associated chest pain, in the absence of detectable left ventricular (LV) systolic dysfunction, coronary artery disease, or lung disease. Often the patients are older, female, and have isolated basal septal hypertrophy (BSH), frequently on a background of mild hypertension. The topic of breathlessness in patients with clinical heart failure, but who have a normal ejection fraction (HFNEF) has attracted significant controversy over the past few years. This review aims to analyse the literature on BSH, identify the possible associations between BSH and HFNEF, and consequently explore possible pathophysiological mechanisms whereby clinical symptoms are experienced.

Left ventricular energetics: new insight into the plasticity of regional contributions at rest and during exercise

Although the human left ventricle (LV) operates as a functional syncytium and previous studies have reported a single value for LV stroke work at rest, more intricate plasticity of regional LV energetics may be required during enhanced cardiovascular demand. We compared kinetic energy of the LV base and apex, respectively, during ventricular contraction and relaxation at rest and during continuous and discontinuous incremental exercise. At rest, prior to both exercise trials, the accumulated kinetic energy during contraction and relaxation was significantly higher at the LV base compared with the apex ( P ≤ 0.05). With increasing exercise intensity, kinetic energy during contraction increased significantly more at the LV base (interaction effect: P < 0.0001), while kinetic energy during relaxation increased significantly more at the apex during high-intensity exercise (interaction effect: P < 0.001). Total kinetic energy produced over the entire cardiac cycle was significantly greater at the LV apex during high exercise intensities ( P < 0.05). We further show that the region-specific differences in kinetic energy at rest and during exercise are explained by significantly different wall mechanics, showing heterogenic contributions from radial, circumferential, and angular components at the base and apex, respectively. In conclusion, the present findings provide unique insight into human LV function by demonstrating that within this functional syncytium, significant differences in the regional contributions of kinetic energy to overall LV work exist. Importantly, regional contributions are not fixed but highly plastic and the underpinning LV wall energetics adjust according to the prevailing cardiovascular demand.

Assessment of the rotation motion at the papillary muscle short-axis plane with normal subjects by two-dimensional speckle tracking imaging: a basic clinical study

Background

The aim of this study was to observe the rotation patterns at the papillary muscle plane in the Left Ventricle(LV) with normal subjects using two-dimensional speckle tracking imaging(2D-STI).

Methods

We acquired standard of the basal, the papillary muscle and the apical short-axis images of the LV in 64 subjects to estimate the LV rotation motion by 2D-STI. The rotational degrees at the papillary muscle short-axis plane were measured at 15 different time points in the analysis of two heart cycles.

Results

There were counterclockwise rotation, clockwise rotation, and counterclockwise to clockwise rotation at the papillary muscle plane in the LV with normal subjects, respectively. The ROC analysis of the rotational degrees was performed at the papillary muscle short-axis plane at the peak LV torsion for predicting whether the turnaround point of twist to untwist motion pattern was located at the papillary muscle level. Sensitivity and specificity were 97% and 67%, respectively, with a cut-off value of 0.34°, and an area under the ROC curve of 0.8. At the peak LV torsion, there was no correlation between the rotational degrees at the papillary muscle short-axis plane and the LVEF in the normal subjects(r = 0.000, p = 0.998).

Conclusions

In the study, we conclude that there were three rotation patterns at the papillary muscle short-axis levels, and the transition from basal clockwise rotation to apical counterclockwise rotation is located at the papillary muscle level.

Left ventricular twist during dobutamine stress echocardiography after acute myocardial infarction: association with reverse remodeling

Left ventricular (LV) twist is emerging as a marker of global LV contractility after acute myocardial infarction (AMI). This study aimed to describe stress-induced changes in LV twist during dobutamine stress echocardiography (DSE) after AMI and investigate their association with LV reverse remodeling at 6 months follow-up. In 82 consecutive first AMI patients (61 ± 12 years, 85 % male) treated with primary percutaneous coronary intervention, DSE was performed at 3 months follow-up. Two-dimensional speckle-tracking-derived apical and basal rotation and LV twist were calculated at rest, low- and peak-dose stages. LV reverse remodeling was defined as ≥10 % decrease in LV end-systolic volume between baseline and 6 months follow-up. Patterns of LV twist response on DSE consisted of either a progressive increase throughout each stage (n = 18), an increase at either low- or peak-dose (n = 53) or no significant increase (n = 11). LV reverse remodeling occurred in 28 (34 %) patients, who showed significantly higher peak-dose LV twist (8.51° vs. 6.69°, p = 0.03) and more frequently progressive LV twist increase from rest to peak-dose (39 vs. 13 %, p < 0.01) compared to patients without reverse remodeling. Furthermore, increase in LV twist from rest to peak-dose was the only independent predictor of LV reverse remodeling at 6 months follow-up (OR 1.3, 95 % CI 1.1-1.5, p = 0.005). Both the pattern of progressive increase in LV twist and the stress-induced increment in LV twist on DSE are significantly associated with LV reverse remodeling at 6 month follow-up after AMI, suggesting its potential use as a novel marker of contractile reserve.

New Insights Into Diastolic Dysfunction and Heart Failure With Preserved Ejection Fraction

As the population ages, the incidence of patients presenting for surgical procedures with diastolic dysfunction and heart failure with preserved ejection fraction will rise. This review will discuss the most current and relevant information on the pathophysiology, treatment, and perioperative management of these patients.