Following the Flow in Chambers

Usefulness of tissue Doppler-derived left ventricular isovolumic contraction velocity in patients with heart failure with preserved ejection fraction

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is a group of diseases classified by left ventricular (LV) EF, a measure of pump function. However, LVEF does not reflect LV contractility. Previous studies have shown that tissue Doppler-derived LV isovolumic contraction velocity (IVCv) correlates well with the LV peak dP/dt, an index of LV contractility. We explored whether LV IVCv is associated with 1-year post-discharge outcomes in HFpEF.

METHODS

We enrolled 113 patients (median age, 86 years, 45 male) with HFpEF (EF on admission ≥ 50%) who were admitted to our hospital for the treatment of acute HF. Clinical characteristics including echocardiographic data were obtained before discharge. IVCv was obtained from the tissue Doppler waveforms of both the septal and lateral mitral annulus of the apical 4-chamber view and averaged data were used. Primary outcomes were all-cause death or unplanned hospitalization due to HF within the first year.

RESULTS

Among all patients, median LVEF was 61%, left atrial diameter was 47 mm, E/e' was 17.5, and IVCv was 4.5 cm/sec; mean tricuspid regurgitation velocity was 2.6 m/sec. Regarding laboratory data, the median plasma B-type natriuretic peptide level was 185 pg/mL. Thirty-four events occurred (15 deaths, 19 unplanned hospitalizations due to HF) within the first year. In multivariate Cox proportional hazards analyses, IVCv was significantly associated with outcomes (hazard ratio .68, 95% confidence interval .50-.89, p = .0095), independent of general characteristics, echocardiographic measures and pertinent laboratory parameters.

CONCLUSION

LV IVCv was independently associated with 1-year outcomes in patients with HFpEF.

Left Ventricular Remodeling Following Balloon Mitral Valvuloplasty in Rheumatic Mitral Stenosis: Magnetic Resonance Imaging Study

Background: Rheumatic heart disease affects primarily cardiac valves, it could involve the myocardium either primarily or secondary to heart valve affection. The influence of balloon mitral valvuloplasty (BMV) on left ventricular function has not been sufficiently studied.

Aim: To determine the influence of balloon mitral valvuloplasty (BMV) on both global and regional left ventricular (LV) function.

Methods: Thirty patients with isolated rheumatic mitral stenosis (MS) were studied. All patients had cardiac magnetic resonance imaging (CMR) before, 6 months and 1 year after successful BMV. LV volumes, ejection fraction (EF), regional and global LV deformation, and LV late gadolinium enhancement were evaluated.

Results: At baseline, patients had median EF of 57 (range: 45–69) %, LVEDVI of 74 (44–111) ml/m² and LVESVI of 31 (14–57) ml/m² with absence of late gadolinium enhancement in all myocardial segments. Six months following BMV, there was a significant increase in LV peak systolic global longitudinal strain (GLS) (−16.4 vs. −13.8, p < 0.001) and global circumferential strain (GCS) (−17.8 vs. −15.6, p = 0.002). At 1 year, there was a trend towards decrease in LVESVI (29 ml/m², p = 0.079) with a significant increase in LV EF (62%, p < 0.001). A further significant increase, compared to 6 months follow up studies, was noticed in GLS (−17.9 vs. −16.4, p = 0.008) and GCS (−19.4 vs. −17.8 p = 0.03).

Conclusions: Successful BMV is associated with improvement in global and regional LV systolic strain which continues for up to 1 year after the procedure.

Impact of balloon mitral valvuloplasty on left ventricular rotational deformation: Magnetic Resonance Imaging follow up study

In patients with rheumatic mitral stenosis (MS), some previous studies have investigated the influence of balloon mitral valvuloplasty (BMV) on left ventricular (LV) systolic function. However, the impact of BMV on LV twisting motion in this clinical setting has not been studied before yet. To describe changes in LV torsion in patients with rheumatic MS following BMV. Thirty patients (median age 33 years, 22 women) with isolated severe MS were studied. CMR myocardial tissue tagging was used for assessment of LV rotational deformation. LV torsion was calculated as the twist value (the net difference between apical counterclockwise and basal clockwise rotation) normalized to the length of the ventricle and multiplied by the mean radius at the base and apex. All patients had CMR studies before, 6 months and 1 year after successful BMV. At baseline, patients had a mitral valve area of 0.9 (0.6-1.3) cm², mean pressure gradient of 12.5 (8-24) mmHg across the valve as measured by transthoracic echocardiography. Median LV ejection fraction (LVEF) estimated by CMR was 57 (range: 45-69) %. A significant improvement in LV base-apex torsion was shown at 6 months (3.3° vs. 2.5°, p < 0.001) with a further improvement at 1 year (4.1° vs. 3.3°, p = 0.05). Similar pattern of change was seen in LV base-mid torsion with a significant increase at 6 months (3.6° vs. 2.3°, p < 0.001) and a further increase at 1 year (4.7° vs. 3.6°, p = 0.007). These changes were associated with a significant increase in LVEF (62% vs. 57%, p < 0.001) at 1 year following BMV. Successful BMV is associated with a significant improvement in LV torsion that is accompanied by a significant improvement in LVEF.

Diagnosis and Pathophysiological Mechanisms of Group 3 Hypoxia-Induced Pulmonary Hypertension

PURPOSE OF REVIEW

Group 3 hypoxia-induced pulmonary hypertension (PH) is an important and increasingly diagnosed condition in both the pediatric and adult population. The majority of pulmonary hypertension studies to date and all three classes of drug therapies were designed to focus on group 1 PH. There is a clear unmet medical need for understanding the molecular mechanisms of group 3 PH and a need for novel non-invasive methods of assessing PH in neonates.

RECENT FINDINGS

Several growth factors are expressed in patients and in animal models of group 3 PH and are thought to contribute to the pathophysiology of this disease. Here, we review some of the findings on the roles of vascular endothelial growth factor A (VEGFA), platelet-derived growth factor B (PDGFB), transforming growth factor-beta (TGFB1), and fibroblast growth factors (FGF) in PH. Additionally, we discuss novel uses of echocardiographic parameters in assessing right ventricular form and function. FGF2, TGFB, PDGFB, and VEGFA may serve as biomarkers in group 3 PH along with echocardiographic methods to diagnose and follow right ventricle function. FGFs and VEGFs may also function in the pathophysiology of group 3 PH.

Patient-specific modeling of left ventricular electromechanics as a driver for haemodynamic analysis

Aims

Models of blood flow in the left ventricle (LV) and aorta are an important tool for analysing the interplay between LV deformation and flow patterns. Typically, image-based kinematic models describing endocardial motion are used as an input to blood flow simulations. While such models are suitable for analysing the hemodynamic status quo, they are limited in predicting the response to interventions that alter afterload conditions. Mechano-fluidic models using biophysically detailed electromechanical (EM) models have the potential to overcome this limitation, but are more costly to build and compute. We report our recent advancements in developing an automated workflow for the creation of such CFD ready kinematic models to serve as drivers of blood flow simulations.

Methods and results

EM models of the LV and aortic root were created for four pediatric patients treated for either aortic coarctation or aortic valve disease. Using MRI, ECG and invasive pressure recordings, anatomy as well as electrophysiological, mechanical and circulatory model components were personalized.

Results

The implemented modeling pipeline was highly automated and allowed model construction and execution of simulations of a patient’s heartbeat within 1 day. All models reproduced clinical data with acceptable accuracy.

Conclusion

Using the developed modeling workflow, the use of EM LV models as driver of fluid flow simulations is becoming feasible. While EM models are costly to construct, they constitute an important and nontrivial step towards fully coupled electro-mechano-fluidic (EMF) models and show promise as a tool for predicting the response to interventions which affect afterload conditions.

Advances in Echocardiographic Imaging in Heart Failure With Reduced and Preserved Ejection Fraction

Echocardiography, given its safety, easy availability, and the ability to permit a comprehensive assessment of cardiac structure and function, is an indispensable tool in the evaluation and management of patients with heart failure (HF). From initial phenotyping and risk stratification to providing vital data for guiding therapeutic decision-making and monitoring, echocardiography plays a pivotal role in the care of HF patients. The recent advent of multiparametric approaches for myocardial deformation imaging has provided valuable insights in the pathogenesis of HF, elucidating distinct patterns of myocardial dysfunction and events that are associated with progression from subclinical stage to overt HF. At the same time, miniaturization of echocardiography has further expanded clinical application of echocardiography, with the use of pocket cardiac ultrasound as an adjunct to physical examination demonstrated to improve diagnostic accuracy and risk stratification. Furthermore, ongoing advances in the field of big data analytics promise to create an exciting opportunity to operationalize precision medicine as the new approach to healthcare delivery that aims to individualize patient care by integrating data extracted from clinical, laboratory, echocardiographic, and genetic assessments. The present review summarizes the recent advances in the field of echocardiography, with emphasis on their role in HF phenotyping, risk stratification, and optimizing clinical outcomes.

Effects of Bileaflet Mechanical Mitral Valve Rotational Orientation on Left Ventricular Flow Conditions

We studied left ventricular flow patterns for a range of rotational orientations of a bileaflet mechanical heart valve (MHV) implanted in the mitral position of an elastic model of a beating left ventricle (LV). The valve was rotated through 3 angular positions (0, 45, and 90 degrees) about the LV long axis. Ultrasound scans of the elastic LV were obtained in four apical 2-dimensional (2D) imaging projections, each with 45 degrees of separation. Particle imaging velocimetry was performed during the diastolic period to quantify the in-plane velocity field obtained by computer tracking of diluted microbubbles in the acquired ultrasound projections. The resulting velocity field, vorticity, and shear stresses were statistically significantly altered by angular positioning of the mechanical valve, although the results did not show any specific trend with the valve angular position and were highly dependent on the orientation of the imaging plane with respect to the valve. We conclude that bileaflet MHV orientation influences hemodynamics of LV filling. However, determination of ‘optimal’ valve orientation cannot be made without measurement techniques that account for the highly 3-dimensional (3D) intraventricular flow.

Mechanotransduction mechanisms for intraventricular diastolic vortex forces and myocardial deformations: part 1

Epigenetic mechanisms are fundamental in cardiac adaptations, remodeling, reverse remodeling, and disease. This two-article series proposes that variable forces associated with diastolic RV/LV rotatory intraventricular flows can exert physiologically and clinically important, albeit still unappreciated, epigenetic actions influencing functional and morphological cardiac adaptations and/or maladaptations. Taken in toto, the two-part survey formulates a new paradigm in which intraventricular diastolic filling vortex-associated forces play a fundamental epigenetic role, and examines how heart cells react to these forces. The objectives are to provide a perspective on vortical epigenetic effects, to introduce emerging ideas, and to suggest directions of multidisciplinary translational research. The main goal is to make pertinent biophysics and cytomechanical dynamic systems concepts accessible to interested translational and clinical cardiologists. I recognize that the diversity of the epigenetic problems can give rise to a diversity of approaches and multifaceted specialized research undertakings. Specificity may dominate the picture. However, I take a contrasting approach. Are there concepts that are central enough that they should be developed in some detail? Broadness competes with specificity. Would, however, this viewpoint allow for a more encompassing view that may otherwise be lost by generation of fragmented results? Part 1 serves as a general introduction, focusing on background concepts, on intracardiac vortex imaging methods, and on diastolic filling vortex-associated forces acting epigenetically on RV/LV endocardium and myocardium. Part 2 will describe pertinent available pluridisciplinary knowledge/research relating to mechanotransduction mechanisms for intraventricular diastolic vortex forces and myocardial deformations and to their epigenetic actions on myocardial and ventricular function and adaptations.

Novel methods for assessment of right heart structure and function in pulmonary hypertension

Long-term increases in pulmonary vascular resistance and pulmonary arterial pressure resulting from structural alterations and abnormal vasoreactivity of the pulmonary vasculature may lead to right ventricular (RV) remodeling. Conventional methods of assessment of RV structure and function do not provide sensitive markers of RV remodeling for prognostic information. Advances in cardiac imaging have provided the capability to obtain quantitative information on the RV structure and function. This article reviews the clinical conditions that result in PH and discusses the novel and emerging methods for the assessment of right heart structure and function in PH in infants and children.

Visualization of the intracavitary blood flow in systemic ventricles of Fontan patients by contrast echocardiography using particle image velocimetry

BACKGROUND

Flow patterns in univentricular hearts may have clinical value. Therefore, it is our objective to asses and characterize vortex flow patterns with Fontan circulation in comparison with healthy controls.

METHODS

Twenty-three patients (8 Fontan and 15 normal patients) underwent echocardiography with intravenous contrast agent (Sonovue®) administration. Dedicated software was used to perform particle image velocimetry (PIV) and to visualize intracavitary flow in the systemic ventricles of the patients. Vortex parameters including vortex depth, length, width, and sphericity index were measured. Vortex pulsatility parameters including relative strength, vortex relative strength, and vortex pulsation correlation were also measured.

RESULTS

The data from this study show that it is feasible to perform particle velocimetry in Fontan patients. Vortex length (VL) was significantly lower (0.51 ± 0.09 vs 0.65 ± 0.12, P = 0.010) and vortex width (VW) (0.32 ± 0.06 vs 0.27 ± 0.04, p = 0.014), vortex pulsation correlation (VPC) (0.26 ± 0.25 vs -0.22 ± 0.87, p = 0.05) were significantly higher in Fontan patients. Sphericity index (SI) (1.66 ± 0.48 vs 2.42 ± 0.62, p = 0.005), relative strength (RS) (0.77 ± 0.33 vs 1.90 ± 0.47, p = 0.0001), vortex relative strength (VRS) (0.18 ± 0.13 vs 0.43 ± 0.14, p = 0.0001) were significantly lower in the Fontan patients group.

CONCLUSIONS

PIV using contrast echocardiography is feasible in Fontan patients. Fontan patients had aberrant flow patterns as compared to normal hearts in terms of position, shape and sphericity of the main vortices. The vortex from the Fontan group was consistently shorter, wider and rounder than in controls. Whether vortex characteristics are related with clinical outcome is subject to further investigation.

Left ventricular muscle and fluid mechanics in acute myocardial infarction

Left ventricular (LV) diastolic filling is characterized by the formation of intraventricular rotational bodies of fluid (termed "vortex rings") that optimize the efficiency of LV ejection. The aim of the present study was to evaluate the morphology and dynamics of LV diastolic vortex ring formation early after acute myocardial infarction (AMI), in relation to LV diastolic function and infarct size. A total of 94 patients with a first ST-segment elevation AMI (59 ± 11 years; 78% men) were included. All patients underwent primary percutaneous coronary intervention. After 48 hours, the following examinations were performed: 2-dimensional echocardiography with speckle-tracking analysis to assess the LV systolic and diastolic function, the vortex formation time (VFT, a dimensionless index for characterizing vortex formation), and the LV untwisting rate; contrast echocardiography to assess LV vortex morphology; and myocardial contrast echocardiography to identify the infarct size. Patients with a large infarct size (≥ 3 LV segments) had a significantly lower VFT (p <0.001) and vortex sphericity index (p <0.001). On univariate analysis, several variables were significantly related to the VFT, including anterior AMI, LV end-systolic volume, LV ejection fraction, grade of diastolic dysfunction, LV untwisting rate, and infarct size. On multivariate analysis, the LV untwisting rate (β = -0.43, p <0.001) and infarct size (β = -0.33, p = 0.005) were independently associated with VFT. In conclusion, early in AMI, both the LV infarct size and the mechanical sequence of diastolic restoration play key roles in modulating the morphology and dynamics of early diastolic vortex ring formation.

Tissue Doppler image-derived measurements during isovolumic contraction predict exercise capacity in patients with reduced left ventricular ejection fraction

OBJECTIVES

We explored the incremental value of quantification of tissue Doppler (TD) velocity during the brief isovolumic contraction (IVC) phase of the cardiac cycle for the prediction of exercise performance in patients referred for cardiopulmonary exercise testing (CPET).

BACKGROUND

Experimental studies have shown that rapid left ventricular (LV) shape change during IVC is essential for optimal onset of LV ejection. However, the incremental value of measuring IVC velocities in clinical settings remains unclear.

METHODS

A total of 82 subjects (age 53+/-14 years, 56 men) were studied with echocardiography and CPET. Reduced LV ejection fraction (EF) (EF<50%) was present in 38 (46%) subjects. Pulsed-wave annular TD velocities were averaged from the LV lateral and septal annulus during isovolumic contraction (IVCa), ejection, isovolumic relaxation, and early and late diastole (Aa) and compared with peak oxygen consumption (VO2) and percentage of the predicted peak VO2 (% predicted peak VO2) obtained from CPET.

RESULTS

Patients with reduced EF had lower IVCa (6.3 vs. 4.5 cm/s, p=0.04), ejection (7.7 vs. 5.5 cm/s, p<0.001), and Aa velocities (7.9 vs. 6.6 cm/s, p=0.04). Similarly, % predicted peak VO2 was lower in patients with reduced EF (52.9% vs. 73.1%, p<0.001) and correlated with the variations in IVCa (r=0.7, p=0.001). Multivariate analysis of 2-dimensional and Doppler variables in the presence of reduced LV EF revealed only IVCa and Aa as independent predictors of % predicted peak VO2 (r2=0.612, p=0.02 for IVCa and p=0.009 for Aa). The overall performance of IVCa in the prediction of exercise capacity was good (area under the curve=0.86, p<0.001).

CONCLUSIONS

Assessment of TD-derived IVC and atrial stretch velocities provide independent prediction of exercise capacity in patients with reduced LV EF. Assessment of LV pre-ejectional stretch and shortening mechanics at rest may be useful for determining the myocardial functional reserve of patients with reduced EF.