Improvement in diastolic intraventricular pressure gradients in patients with HOCM after ethanol septal reduction

Heat-related changes in the velocity and kinetic energy of flowing blood influence the human heart's output during hyperthermia

Passive whole-body hyperthermia increases limb blood flow and cardiac output (Q ̇ $\dot Q$ ), but the interplay between peripheral and central thermo-haemodynamic mechanisms remains unclear. Here we tested the hypothesis that local hyperthermia-induced alterations in peripheral blood flow and blood kinetic energy modulate flow to the heart andQ ̇ $\dot Q$ . Body temperatures, regional (leg, arm, head) and systemic haemodynamics, and left ventricular (LV) volumes and functions were assessed in eight healthy males during: (1) 3 h control (normothermic condition); (2) 3 h of single-leg heating; (3) 3 h of two-leg heating; and (4) 2.5 h of whole-body heating. Leg, forearm, and extracranial blood flow increased in close association with local rises in temperature while brain perfusion remained unchanged. Increases in blood velocity with small to no changes in the conduit artery diameter underpinned the augmented limb and extracranial perfusion. In all heating conditions,Q ̇ $\dot Q$ increased in association with proportional elevations in systemic vascular conductance, related to enhanced blood flow, blood velocity, vascular conductance and kinetic energy in the limbs and head (all R2 ≥ 0.803; P < 0.001), but not in the brain. LV systolic (end-systolic elastance and twist) and diastolic functional profiles (untwisting rate), pulmonary ventilation and systemic aerobic metabolism were only altered in whole-body heating. These findings substantiate the idea that local hyperthermia-induced selective alterations in peripheral blood flow modulate the magnitude of flow to the heart andQ ̇ $\dot Q$ through changes in blood velocity and kinetic energy. Localised heat-activated events in the peripheral circulation therefore affect the human heart's output. KEY POINTS: Local and whole-body hyperthermia increases limb and systemic perfusion, but the underlying peripheral and central heat-sensitive mechanisms are not fully established. Here we investigated the regional (leg, arm and head) and systemic haemodynamics (cardiac output:Q ̇ $\dot Q$ ) during passive single-leg, two-leg and whole-body hyperthermia to determine the contribution of peripheral and central thermosensitive factors in the control of human circulation. Single-leg, two-leg, and whole-body hyperthermia induced graded increases in leg blood flow andQ ̇ $\dot Q$ . Brain blood flow, however, remained unchanged in all conditions. Ventilation, extracranial blood flow and cardiac systolic and diastolic functions only increased during whole-body hyperthermia. The augmentedQ ̇ $\dot Q$ with hyperthermia was tightly related to increased limb and head blood velocity, flow and kinetic energy. The findings indicate that local thermosensitive mechanisms modulate regional blood velocity, flow and kinetic energy, thereby controlling the magnitude of flow to the heart and thus the coupling of peripheral and central circulation during hyperthermia.

Assessment of Early Diastolic Intraventricular Pressure Difference in Children by Blood Speckle-Tracking Echocardiography

BACKGROUND

The lack of reliable echocardiographic techniques to assess diastolic function in children is a major clinical limitation. Our aim was to develop and validate the intraventricular pressure difference (IVPD) calculation using blood speckle-tracking (BST) and investigate the method's potential role in the assessment of diastolic function in children.

METHODS

Blood speckle-tracking allows two-dimensional angle-independent blood flow velocity estimation. Blood speckle-tracking images of left ventricular (LV) inflow from the apical 4-chamber view in 138 controls, 10 patients with dilated cardiomyopathies (DCMs), and 21 patients with hypertrophic cardiomyopathies (HCMs) <18 years of age were analyzed to study LV IVPD during early diastole. Reproducibility of the IVPD analysis was assessed, IVPD estimates from BST and color M mode were compared, and the validity of the BST-based IVPD calculations was tested in a computer flow model.

RESULTS

Mean IVPD was significantly higher in controls (-2.28 ± 0.62 mm Hg) compared with in DCM (-1.21 ± 0.39 mm Hg, P < .001) and HCM (-1.57 ± 0.47 mm Hg, P < .001) patients. Feasibility was 88.3% in controls, 80% in DCM patients, and 90.4% in HCM patients. The peak relative negative pressure occurred earlier at the apex than at the base and preceded the peak E-wave LV filling velocity, indicating that it represents diastolic suction. Intraclass correlation coefficients for intra- and interobserver variability were 0.908 and 0.702, respectively. There was a nonsignificant mean difference of 0.15 mm Hg between IVPD from BST and color M mode. Estimation from two-dimensional velocities revealed a difference in peak IVPD of 0.12 mm Hg (6.6%) when simulated in a three-dimensional fluid mechanics model.

CONCLUSIONS

Intraventricular pressure difference calculation from BST is highly feasible and provides information on diastolic suction and early filling in children with heart disease. Intraventricular pressure difference was significantly reduced in children with DCM and HCM compared with controls, indicating reduced early diastolic suction in these patient groups.

Intraventricular pressure gradients change during the development of left ventricular hypertrophy: Effect of salvianolic acid B and beta-blocker

Introduction

Intraventricular pressure gradient is regarded as a non-invasive indicator of diastolic function. Salvianolic acid B (Sal-B), a traditional Asian medicine, revealed its usefulness in myocardial infarction models; however, the hemodynamic effect of salvianolic acid B is still unknown. The present study aimed to investigate the intraventricular pressure gradient changes during the development of left ventricular hypertrophy with or without salvianolic acid B and a beta-blocker.

Methods

In total, 48 rats were divided into four groups; Sham, Non-treatment, salvianolic acid B, and Carvedilol. Aortic coarctation-induced left ventricular hypertrophy was done in three groups and the treatment was started from the third to the sixth week. Blood pressure, conventional echocardiography, and color M-mode echocardiography for measurement of intraventricular pressure gradient were carried out for six consecutive weeks.

Results

At 4.5 weeks, the LV mass was elevated in the coarctation groups but the blood pressure was significantly lower in salvianolic acid B and Carvedilol groups (P < 0.05). In the Non-treatment group, the total intraventricular pressure gradient was increased at 4.5 and 6 weeks (2.60 and 2.65, respectively). Meanwhile, the basal intraventricular pressure gradient was elevated at 3 and 6 weeks (1.67 and 1.75) compared with the Sham group. Salvianolic acid B and Carvedilol significantly reduced the basal intraventricular pressure gradient at six weeks compared with the Non-treatment group (1.52 and 1.51 vs 1.75, respectively).

Conclusions

Salvianolic acid B and Carvedilol promote cardiac function by decreasing the elevated basal intraventricular pressure gradient. The current preclinical results revealed the efficacy of salvianolic acid B as a potential therapy for left ventricular hypertrophy because of the non-blood pressure lowering effect.

A Wavelet Approach to the Estimation of Left Ventricular Early Filling Wave Propagation Velocity from Color M-Mode Echocardiograms

A new approach to calculating left ventricular (LV) early filling propagation velocity (VP) from color M-mode echocardiograms using wavelet analysis is described. Current methods for measuring VP do not account for the spatiotemporal variation in VP. They are confined by empirical assumptions and user inputs that hinder the accuracy of VP, limiting its clinical utility. We evaluated three methods for measuring LV early filling: conventional VP, the strength of propagation (VS) and wavelet propagation velocity (VW) determined from the most energetically significant wave (peak VW). Group A comprised 125 patients (n = 50 normal filling, n = 25 impaired relaxation, n = 25 pseudonormal filling and n = 25 restrictive filling), and group B comprised 69 patients (n = 32 normal, n = 15 dilated and n = 22 hypertrophic). Peak VW most accurately distinguished normal from diseased patients. For group A, the area under the receiver operating characteristic curve was 0.92 for peak VW versus 0.62 for VP, 0.63 for VS and 0.58 for intraventricular pressure difference. These correspond to a 50%-70% improvement in classification ability. Similar improvements were measured in group B. Peak VW may provide a more accurate evaluation of diastolic function than standard methods and enable better diagnostic classification of patients with diastolic dysfunction.

Progression of left ventricular diastolic function in the neonate and early childhood from transmitral color M-mode filling analysis

BACKGROUND

We implemented sophisticated color M-mode analysis to assess age-dependent progression of left ventricular (LV) diastolic function.

METHODS

Normal infants were prospectively enrolled for serial echocardiograms at 1 week, 1 month, 6 months, 1 year, and 2 years. From color M-mode scans, propagation velocity (V_P), strength of filling (V_S), and intraventricular pressure difference (IVPD) in 3 segments along apex-to-mitral valve scan line were measured.

RESULTS

Age-wise comparisons of diastolic filling from 121 echocardiograms in 31 infants showed V_P (cm/s), V_S (cm²/s), and E-wave IVPD (mmHg) at 1 week to be 66.2 ± 11.9, 75.3 ± 19.9, and 1.5 ± 0.4, respectively, while V_P, V_S, and E-wave IVPD at 1 month were 80.3 ± 14.4, 101.2 ± 28.3, and 2.42 ± 1.1, respectively. There were significant differences in V_P and segmental IVPD between first week and first month (p < 0.005) and IVPD between the age groups (p < 0.001).

CONCLUSIONS

Comprehensive analysis of transmitral color M-mode data is feasible in infants, enabling calculation of pressure drop between the LV base and apex and strength of propagation from two distinct slopes. Profound changes very early followed by relatively constant filling mechanics in later infancy indicate significant LV maturation occurring during the first month of life.

IMPACT

We implemented sophisticated analytic methods for color M-mode echocardiography in infants to assess age- and dimension-dependent changes in left ventricular diastolic function. Comprehensive characterization of transmitral color M-mode flow was feasible, enabling calculation of pressure drop between left ventricular base and apex and strength of propagation. Left ventricular diastolic filling function has predictable maturational progression, with significant differences in the intraventricular pressure between infants from birth to 2 years. This study forms the basis for future studies to examine alteration of early diastolic filling in congenital heart disease.

Dehydration reduces stroke volume and cardiac output during exercise because of impaired cardiac filling and venous return, not left ventricular function

Dehydration accrued during intense prolonged whole-body exercise in the heat compromises peripheral blood flow and cardiac output ( Q ˙ ). A markedly reduced stroke volume (SV) is a key feature of the dehydration-induced cardiovascular strain, but whether the lower output of the heart is mediated by peripheral or cardiac factors remains unknown. Therefore, we repeatedly quantified left ventricular (LV) volumes, LV mechanics (LV twist, a marker of systolic muscle function, and LV untwisting rate, an independent marker of LV muscle relaxation), left intra-ventricular pressure gradients, blood volume and peripheral blood flow during 2 hr of cycling in the heat with and without dehydration (DEH: 4.0 ± 0.2% body mass loss and EUH: euhydration control, respectively) in eight participants (three females and five males). While brachial and carotid blood flow, blood volume, SV, LV end-diastolic volume (LVEDV), cardiac filling time, systemic vascular conductance and Q ˙ were reduced in DEH compared to EUH after 2 hr, LV twist and untwisting rate tended to be higher (p = .09 and .06, respectively) and intra-ventricular pressure gradients were not different between the two conditions (p = .22). Furthermore, LVEDV in DEH correlated strongly with blood volume (r = .995, p < .01), head and forearms beat volume (r = .98, p < .05), and diastolic LV filling time (r = .98, p < .05). These findings suggest that the decline in SV underpinning the blunted Q ˙ with exercise-induced dehydration is caused by compromised LV filling and venous return, but not intrinsic systolic or diastolic LV function.

Analysis of inter-system variability of systolic and diastolic intraventricular pressure gradients derived from color Doppler M-mode echocardiography

Assessment of intraventricular pressure gradients (IVPG) using color Doppler M-mode echocardiography has gained increasing interest in the evaluation of cardiac function. However, standardized analysis tools for IVPG quantification are missing. We aimed to evaluate the feasibility, the test-retest observer reproducibility, and the inter-system variability of a semi-automated IVPG quantification algorithm. The study included forty healthy volunteers (50% were men). All volunteers were examined using two ultrasound systems, the Philips Epiq 7 and the General Electric Vivid 6. Left ventricular diastolic (DIVPG) and systolic (SIVPG) intraventricular pressure gradients were measured from the spatiotemporal distribution of intraventricular propagation flow velocities using color Doppler M-mode in standard apical views. There was good feasibility for both systolic and diastolic IVPG measurements (82.5% and 85%, respectively). Intra and inter-observer test-retest variability measured with the intraclass correlation coefficient were 0.98 and 0.93 for DIVPG respectively, and 0.95 and 0.89 for SIVPG respectively. The inter-system concordance was weak to moderate with Lin’s concordance correlation coefficient of 0.59 for DIVPG and 0.25 for SIVPG. In conclusion, it is feasible and reproducible to assess systolic and diastolic IVPG using color Doppler M-mode in healthy volunteers. However, the inter-system variability in IVPG analysis needs to be taken into account, especially when using displayed data.

Assessment of methodologies to calculate intraventricular pressure differences in computational models and patients

Intraventricular pressure differences (IVPDs) govern left ventricular (LV) efficient filling and are a significant determinant of LV diastolic function. Our primary aim is to assess the performance of available methods (color M-mode (CMM) and 1D/2D MRI-based methods) to determine IVPDs from intracardiac flow measurements. Performance of three methods to calculate IVPDs was first investigated via an LV computational fluid dynamics (CFD) model. CFD velocity data were derived along a modifiable scan line, mimicking ultrasound/MRI acquisition of 1D (IVPD_CMM/IVPD_{1D MRI}) and 2D (IVPD_{2D MRI}) velocity-based IVPD information. CFD pressure data (IVPD_CFD) was used as a ground truth. Methods were also compared in a small cohort (n = 13) of patients with heart failure with preserved ejection fraction (HFpEF). In silico data showed a better performance of the IVPD_{2D MRI} approach: RMSE values for a well-aligned scan line were 0.2550 mmHg (IVPD_{1D MRI}), 0.0798 mmHg (IVPD_{2D MRI}), and 0.2633 mmHg (IVPD_CMM). In vivo data exhibited moderate correlation between techniques. Considerable differences found may be attributable to different timing of measurements and/or integration path. CFD modeling demonstrated an advantage using 2D velocity information to compute IVPDs, and therefore, a 2D MRI-based method should be favored. However, further studies are needed to support the clinical significance of MRI-based computation of IVPDs over CMM.

Alcohol Septal Ablation to Reduce Heart Failure

Hypertrophic cardiomyopathy is a commonly encountered inheritable cardiac disorder with variable phenotypic expression. Although most patients will have no or mild symptoms, 10% will develop heart failure symptoms refractory to medical management. This article discusses the mechanisms through which hypertrophic cardiomyopathy induces heart failure and how alcohol septal ablation can reverse each of these mechanisms to lead to clinical improvement.

Altered spatial distribution of the diastolic left ventricular pressure difference in heart failure

BACKGROUND

The left ventricle fills in early diastole because of a progressive intraventricular pressure difference (IVPD) that extends from the left atrium to the left ventricular (LV). The aim of this study was to test the hypothesis that in patients with symptomatic heart failure (HF) regardless of LV ejection fraction (EF), an increase in left atrial (LA) pressure maintains early diastolic filling because of a preserved IVPD from the left atrium to the mid left ventricle, while the IVPD from the mid left ventricle to the apex is diminished because of reduced LV suction.

METHODS

One hundred fifty-one patients with HF (50 with HF with preserved EF [HFpEF; EF ≥ 50%] and 101 with HF with reduced EF [HFrEF; EF < 50%]) and 28 normal controls were prospectively enrolled. The IVPDs from the left atrium to the LV apex (total IVPD), the left atrium to the mid left ventricle (basilar IVPD), and the mid left ventricle to the apex (apical IVPD) were determined using color M-mode Doppler echocardiographic data to integrate the Euler equation. The propagation of early diastolic filling was also assessed by color M-mode Doppler.

RESULTS

The mean LV EF was 0.63 ± 0.07 in patients with HFpEF, 0.32 ± 0.09 in those with HFrEF, and 0.64 ± 0.06 in controls. Peak early diastolic transmitral flow velocities (E) were similar among the groups, and basilar IVPDs were maintained in the HFpEF and HFrEF groups (HFpEF, 1.59 ± 0.62 mm Hg; HFrEF, 1.49 ± 0.75 mm Hg; controls, 1.80 ± 0.61 mm Hg; P = NS, analysis of variance). However, apical IVPDs were decreased in both HF groups (HFpEF, 1.18 ± 0.56 mm Hg [P < .01 vs controls]; HFrEF, 0.87 ± 0.48 mm Hg [P < .01 vs controls]; controls, 1.65 ± 0.62 mm Hg), resulting in decreased total IVPDs in patients with HF (HFpEF, 2.55 ± 0.80 mm Hg [P < .01 vs controls]; HFrEF, 2.16 ± 0.80 mm Hg [P < .01 vs controls]; controls, 3.17 ± 0.91 mm Hg). E/e' ratios were increased in patients with HF, consistent with elevated LA pressure. In patients with HF, E was correlated with basilar IVPD but not with apical IVPD, whereas propagation of the filling was correlated with the apical IVPD but not with the basilar IVPD.

CONCLUSIONS

In patients with HFpEF and those with HFrEF, apical IVPDs were reduced while basilar IVPDs were maintained by elevated LA pressure, resulting in preserved E.

Delay of left ventricular longitudinal expansion with diastolic dysfunction: impact on load dependence of e' and longitudinal strain rate

The effect of diastolic dysfunction (DD) on the timing of left ventricular (LV) diastolic longitudinal and circumferential expansion and their load dependence is not known. This study evaluated the timing of the peak early diastolic LV inflow velocity (E), mitral annular velocity (e′), and longitudinal and circumferential global strain rates (SR_E) in 161 patients in sinus rhythm. The intraventricular pressure difference (IVPD) from the left atrium to the LV apex was obtained using color M‐mode Doppler data to integrate the Euler equation. The diastolic function was graded according to the guidelines. In normals (N = 57), E, e′, longitudinal SR_E, and circumferential SR_E occurred nearly simultaneously during the IVPD. With DD (N = 104), e′ and longitudinal SR_E were delayed occurring after the IVPD (e′: 18 ± 23 msec, longitudinal SR_E: 13 ± 21 msec from the IVPD), whereas circumferential SR_E (−8 ± 28 msec) and E (−2 ± 13 msec) were not delayed. The normal dependence of e′ and longitudinal SR_E on IVPD was reduced in DD; while the relation of circumferential SR_E and E to IVPD were unchanged in DD. Thus, normally, the LV expands symmetrically during early diastole and both longitudinal and circumferential expansions are related to the IVPD. With DD, early diastolic longitudinal LV expansion is delayed, occurring after the IVPD and LV filling, resulting in their relative independence from the IVPD. In contrast, with DD, circumferential SR_E and mitral inflow are not delayed and their normal relation to the IVPD is unchanged.

In patients with diastolic dysfunction, longitudinal LV expansion is delayed occurring after mitral flow and the termination of the pressure difference from the left atrium to the LV apex. Thus, with diastolic dysfunction longitudinal expansion (e' and longitudinal early diastolic global strain rate) become nearly independent of load.

Assessment of left ventricular diastolic dysfunction based on the intraventricular velocity difference by vector flow mapping

OBJECTIVES

The diastolic intraventricular velocity difference represents diastolic function of the left ventricle (LV). Here we analyzed the LV diastolic intraventricular velocity difference in patients with impaired LV function based on the ventricular flow rate profile by vector flow mapping.

METHODS

Patients with LV diastolic dysfunction were divided into 2 groups: chronic heart failure with restricted filling (group 1; n = 27) and hypertension with abnormal relaxation (group 2; n = 34). Healthy participants were identified as controls (group 3; n = 22). Left ventricular inflow color Doppler findings were analyzed by the vector profile model with the vector flow mapping technology offline. The flow velocity rates at the base and apex of the LV were measured from vector profiles with the vector flow mapping technology. The diastolic intraventricular velocity difference was calculated from flow velocity rates.

RESULTS

The diastolic intraventricular velocity difference calculated from vector flow mapping was significantly lower in both groups with LV diastolic dysfunction than the control group (mean ± SD, 79.95 ± 9.88 cm/s in controls versus 40.35 ± 6.80 cm/s in group 1 and 48.50 ± 6.03 cm/s in group 2; P < .001 for both). The diastolic intraventricular velocity difference had a significant association with the ejection fraction (P = .0002) and deceleration time (P = .0306). The peak atrial contraction velocity was negatively related to the diastolic intraventricular velocity difference (P = .0003).

CONCLUSIONS

The diastolic intraventricular velocity difference derived from the LV velocity rate by the vector profile model on vector flow mapping can be potentially used for quantitative assessment of LV diastolic function. Vector flow mapping proved to be clinically practical for reflecting LV diastolic dysfunction in pathologic states.

Left intraventricular diastolic and systolic pressure gradients

To describe left ventricular (LV) function comprehensively, it is crucial to characterize precisely transmitral, intraventricular and transaortic pressure–flow relations. The site of measurement is important; as the measurement location is moved from the mitral valve toward the apex and the outflow tract, important regional pressure differences are recorded inside the LV. These intraventricular pressure gradients (IVPGs) play an important role in ventricular filling in the normal heart and may be abolished by systolic or diastolic dysfunction. Despite their apparent importance in ventricular filling and diastolic function, IVPGs have never been utilized in clinical cardiology, due to the complexity of their acquisition. The application of Doppler echocardiography allows the reconstruction of diastolic IVPGs completely non-invasively, thus avoiding the risk and expense of a cardiac catheterization. Regional pressure gradients are also present during ventricular emptying but their correlation with systolic function is not so clear. The current minireview highlights theories and experimental data on invasive and non-invasive assessment of diastolic and systolic IVPGs and their role in LV filling and emptying. We also review the pathophysiological modulation of regional gradients, their importance in understanding and evaluating the complex phenomena underlying ventricular filling, as well as their potential clinical application.

Current and evolving echocardiographic techniques for the quantitative evaluation of cardiac mechanics: ASE/EAE consensus statement on methodology and indications endorsed by the Japanese Society of Echocardiography

Echocardiographic imaging is ideally suited for the evaluation of cardiac mechanics because of its intrinsically dynamic nature. Because for decades, echocardiography has been the only imaging modality that allows dynamic imaging of the heart, it is only natural that new, increasingly automated techniques for sophisticated analysis of cardiac mechanics have been driven by researchers and manufacturers of ultrasound imaging equipment. Several such techniques have emerged over the past decades to address the issue of reader's experience and inter-measurement variability in interpretation. Some were widely embraced by echocardiographers around the world and became part of the clinical routine, whereas others remained limited to research and exploration of new clinical applications. Two such techniques have dominated the research arena of echocardiography: (1) Doppler-based tissue velocity measurements, frequently referred to as tissue Doppler or myocardial Doppler, and (2) speckle tracking on the basis of displacement measurements. Both types of measurements lend themselves to the derivation of multiple parameters of myocardial function. The goal of this document is to focus on the currently available techniques that allow quantitative assessment of myocardial function via image-based analysis of local myocardial dynamics, including Doppler tissue imaging and speckle-tracking echocardiography, as well as integrated back- scatter analysis. This document describes the current and potential clinical applications of these techniques and their strengths and weaknesses, briefly surveys a selection of the relevant published literature while highlighting normal and abnormal findings in the context of different cardiovascular pathologies, and summarizes the unresolved issues, future research priorities, and recommended indications for clinical use.

Current and evolving echocardiographic techniques for the quantitative evaluation of cardiac mechanics: ASE/EAE consensus statement on methodology and indications endorsed by the Japanese Society of Echocardiography

Echocardiographic imaging is ideally suited for the evaluation of cardiac mechanics because of its intrinsically dynamic nature. Because for decades, echocardiography has been the only imaging modality that allows dynamic imaging of the heart, it is only natural that new, increasingly automated techniques for sophisticated analysis of cardiac mechanics have been driven by researchers and manufacturers of ultrasound imaging equipment.Several such technique shave emerged over the past decades to address the issue of reader's experience and inter measurement variability in interpretation.Some were widely embraced by echocardiographers around the world and became part of the clinical routine,whereas others remained limited to research and exploration of new clinical applications.Two such techniques have dominated the research arena of echocardiography: (1) Doppler based tissue velocity measurements,frequently referred to as tissue Doppler or myocardial Doppler, and (2) speckle tracking on the basis of displacement measurements.Both types of measurements lend themselves to the derivation of multiple parameters of myocardial function. The goal of this document is to focus on the currently available techniques that allow quantitative assessment of myocardial function via image-based analysis of local myocardial dynamics, including Doppler tissue imaging and speckle-tracking echocardiography, as well as integrated backscatter analysis. This document describes the current and potential clinical applications of these techniques and their strengths and weaknesses,briefly surveys a selection of the relevant published literature while highlighting normal and abnormal findings in the context of different cardiovascular pathologies, and summarizes the unresolved issues, future research priorities, and recommended indications for clinical use.

Rationale, design and methodology for Intraventricular Pressure Gradients Study: a novel approach for ventricular filling assessment in normal and falling hearts

BACKGROUND

Intraventricular pressure gradients have been described between the base and the apex of the left ventricle during early diastolic ventricular filling, as well as, their increase after systolic and diastolic function improvement. Although, systolic gradients have also been observed, data are lacking on their magnitude and modulation during cardiac dysfunction. Furthermore, we know that segmental dysfunction interferes with the normal sequence of regional contraction and might be expected to alter the physiological intraventricular pressure gradients. The study hypothesis is that systolic and diastolic gradients, a marker of normal left ventricular function, may be related to physiological asynchrony between basal and apical myocardial segments and they can be attenuated, lost entirely, or even reversed when ventricular filling/emptying is impaired by regional acute ischemia or severe aortic stenosis.

METHODS/DESIGN

Animal Studies: Six rabbits will be completely instrumented to measuring apex to outflow-tract pressure gradient and apical and basal myocardial segments lengthening changes at basal, afterloaded and ischemic conditions. Afterload increase will be performed by abruptly narrowing or occluding the ascending aorta during the diastole and myocardial ischemia will be induced by left coronary artery ligation, after the first diagonal branch.Patient Studies: Patients between 65-80 years old (n = 12), both genders, with severe aortic stenosis referred for aortic valve replacement will be selected as eligible subjects. A high-fidelity pressure-volume catheter will be positioned through the ascending aorta across the aortic valve to measure apical and outflow-tract pressure before and after aortic valve replacement with a bioprosthesis. Peak and average intraventricular pressure gradients will be recorded as apical minus outflow-tract pressure and calculated during all diastolic and systolic phases of cardiac cycle.

DISCUSSION

We expect to validate the application of our method to obtain intraventricular pressure gradients in animals and patients and to promote a methodology to better understand the ventricular relaxation and filling and their correlation with systolic function.

New echocardiographic applications for assessing global left ventricular diastolic function

A number of promising and highly technological echocardiographic imaging tools have recently been introduced to assess left ventricular diastolic function (i.e., the capacity of the ventricle to relax and fill). They permit quantification of distinct features of intraventricular blood flow velocity and pressure fields and myocardial tissue velocities. However, accurate interpretation of the new images and clinical indices is still cumbersome, as basic knowledge about intraventricular hemodynamics and ventricular wall mechanics is often insufficient. This review article provides a comprehensive and original overview of the hemodynamical and mechanical events that occur during diastole and discusses how this new information can be used in the clinical and research setting to evaluate diastolic function in the healthy and the diseased heart. It furthermore aims to explain the underpinnings of the techniques in such a way that the underlying biomechanical concepts (fluid dynamics and wall mechanics) become less obscure to cardiologists and echocardiographers and such that the biomedical engineers are given some insights into the avalanche of diastolic performance indices that currently exist.

Role of Tissue Doppler and Color M-Mode Imaging for Evaluation of Diastolic Function in Ambulatory Patients with LV Systolic Dysfunction

INTRODUCTION

Tissue Doppler imaging (TDI) and color M-mode (CMM) indices provide assessment of left ventricular (LV) relaxation when combined with pulse-wave Doppler (PWD)-derived transmitral inflow, allows for estimation of LV filling pressures. However, use of these indices in patients with LV systolic dysfunction (LVSD) has not been well characterized.

METHODS AND RESULTS

The study included 115 patients (age 58 +/- 11 years, 67% male) with LVSD (LV ejection fraction [LVEF] < 55%). Patients were grouped according to the diastolic LV filling pressure assessed by E/Em(septal) ratio as follows: 1) Normal (NFP), E/Em(septal) < 8; 2) Intermediate (IFP), E/Em(septal): 8-15; and 3) High (HFP), E/Em(septal) >15. Age-, gender-, and LVEF-adjusted analyses were performed. LV volumes and LVEF were significantly different between the groups (P < 0.01). PWD-derived E-wave velocity showed a significant stepwise increase across the three groups and the Em(septal) velocity demonstrated a stepwise decrease (P < 0.01 for both). CMM-derived diastolic intra-ventricular pressure gradient (IVPG) was significantly lower in the HFP compared to the other 2 groups (P < 0.01 for both); Vp was increased in the HFP compared to the other 2 groups (P < 0.01 for both), and Vp exhibited a U-shape relationship to LVEF.

CONCLUSION

In patients with LVSD, abnormal LV relaxation is uniformly observed regardless of LV filling pressure. PWD-derived E-wave velocity and the TDI-derived Em velocity are important measurements to identify elevated LV filling pressures. CMM-derived Vp and IVPG were of limited incremental value for the evaluation of diastolic function in patients with LVSD.

Assessment of left ventricular function by cardiac ultrasound

Our understanding of the physical underpinnings of the assessment of cardiac function is becoming increasingly sophisticated. Recent developments in cardiac ultrasound permit exploitation of many of these newer physical concepts with current echocardiographic machines. This review will first focus on the current approach to the assessment of cardiovascular hemodynamics by cardiac ultrasound. The next focus will be the assessment of global cardiac mechanics in systole and diastole. Finally, relationships between the cardiac structure and regional myocardial function, and the way regional function can be quantified by ultrasound, will be presented. This review also discusses the clinical impact of echocardiography and its future directions and developments.

Characterization of left ventricular diastolic function in hypertension by use of Doppler tissue imaging and color M-mode techniques

BACKGROUND

Abnormalities in left ventricular (LV) relaxation and/or increased filling pressures are indicators of LV diastolic dysfunction in patients with hypertension (HTN). The purpose of this study was to assess clinical use of pulsed wave Doppler, Doppler tissue imaging (DTI), and color M-mode (CMM) indices for determination of diastolic function in patients with HTN.

METHODS

In all, 278 ambulatory patients with normal LV systolic function were grouped according to the presence of HTN with and without LV hypertrophy (LVH) (determined by the 2-dimensional area-length method) as follows: healthy control subjects (NC, n = 122), HTN without LVH (HTN, n = 70), and HTN with LVH (HTN+LVH, n = 86). Pulsed wave Doppler-derived measurements included transmitral E- and A-wave velocities, E/A ratio, and deceleration and isovolumic relaxation time intervals; DTI-derived early diastolic (Em) velocities were obtained at 4 LV annular sites. CMM-derived flow propagation velocity and the intraventricular pressure gradient were also calculated. Analysis of covariance adjusted for age and sex of diastolic indices was performed to compare the differences among groups.

RESULTS

Only DTI-derived filling pressures demonstrated progressive statistically significant differences among all 3 groups (ie, HTN vs NC, HTN+LVH vs NC, and HTN vs HTN+LVH). However, CMM-derived flow propagation velocity and intraventricular pressure gradient indices were similar among the groups.

CONCLUSION

DTI is a robust method compared with pulsed wave Doppler- and CMM-derived indices for the quantitative assessment of LV relaxation and filling pressures in patients with HTN.

Scaling of diastolic intraventricular pressure gradients is related to filling time duration

In early diastole, pressure is lower in the apex than in the base of the left ventricle (LV). This early intraventricular pressure difference (IVPD) facilitates LV filling. We assessed how LV diastolic IVPD and intraventricular pressure gradient (IVPG), defined as IVPD divided by length, scale to the heart size and other physiological variables. We studied 10 mice, 10 rats, 5 rabbits, 12 dogs, and 21 humans by echocardiography. Color Doppler M-mode data were postprocessed to reconstruct IVPD and IVPG. Normalized LV filling time was calculated by dividing filling time by RR interval. The relationship between IVPD, IVPG, normalized LV filling time, and LV end-diastolic volume (or mass) as fit to the general scaling equation Y = kMβ, where M is LV heart size parameter, Y is a dependent variable, k is a constant, and β is the power of the scaling exponent. LV mass varied from 0.049 to 194 g, whereas end-diastolic volume varied from 0.011 to 149 ml. The β values relating normalized LV filling time with LV mass and end-diastolic volume were 0.091 (SD 0.011) and 0.083 (SD 0.009), respectively ( P < 0.0001 vs. 0 for both). The β values relating IVPD with LV mass and end-diastolic volume were similarly significant at 0.271 (SD 0.039) and 0.243 (SD 0.0361), respectively ( P < 0.0001 vs. 0 for both). Finally, β values relating IVPG with LV mass and end-diastolic volume were −0.118 (SD 0.013) and −0.104 (SD 0.011), respectively ( P < 0.0001 vs. 0 for both). As a result, there was an inverse relationship between IVPG and normalized LV filling time ( r = −0.65, P < 0.001). We conclude that IVPD decrease, while IVPG increase with decreasing animal size. High IVPG in small mammals may be an adaptive mechanism to short filling times.

Relationship among diastolic intraventricular pressure gradients, relaxation, and preload: impact of age and fitness

Diastolic intraventricular pressure gradients (IVPGs) are a measure of the ability of the ventricle to facilitate its filling using diastolic suction. We assessed 15 healthy young but sedentary subjects, aged <50 yr (young subjects; age, 35 ± 9 yr); 13 healthy but sedentary seniors, aged >65 yr with known reductions in ventricular compliance (elderly sedentary subjects; age, 70 ± 4 yr); and 12 master athletes, aged >65 yr, previously shown to have preserved ventricular compliance (elderly fit subjects; age, 68 ± 3 yr). Pulmonary capillary wedge pressure (PCWP) and echocardiography measurements were performed at baseline, during load manipulation by lower body negative pressure at −15 and −30 mmHg, and after saline infusion of 10 and 20 ml/kg (elderly) or 15 and 30 ml/kg (young). IVPGs were obtained from color M-mode Doppler echocardiograms. Baseline IVPGs were lower (1.2 ± 0.4 vs. 2.4 ± 0.7 mmHg, P < 0.0001), and the time constant of pressure decay (τ0) was longer (60 ± 10 vs. 46 ± 6 ms, P < 0.0001) in elderly sedentary than in young subjects, with no difference in PCWP. Although PCWP changes during load manipulations were similar ( P = 0.70), IVPG changes were less prominent in elderly sedentary than in young subjects ( P = 0.02). Changes in stroke volume and IVPGs during loading manipulations correlated ( r = 0.96, P = 0.0002). PCWP and τ0 were strong multivariate correlates of IVPGs ( P < 0.001, for both). IVPG response to loading interventions in elderly sedentary and elderly fit subjects was similar ( P = 0.33), despite known large differences in ventricular compliance. The ability to regulate IVPGs during changes in preload is impaired with aging. Preserving ventricular compliance during aging by lifelong exercise training does not prevent this impairment.

A Noninvasive Method for Assessing Impaired Diastolic Suction in Patients With Dilated Cardiomyopathy

BACKGROUND

Diastolic suction is a major determinant of early left ventricular filling in animal experiments. However, suction remains incompletely characterized in the clinical setting.

METHODS AND RESULTS

First, we validated a method for measuring the spatio-temporal distributions of diastolic intraventricular pressure gradients and differences (DIVPDs) by digital processing color Doppler M-mode recordings. In 4 pigs, the error of peak DIVPD was 0.0+/-0.2 mm Hg (intraclass correlation coefficient, 0.95) compared with micromanometry. Forty patients with dilated cardiomyopathy (DCM) and 20 healthy volunteers were studied at baseline and during dobutamine infusion. A positive DIVPD (toward the apex) originated during isovolumic relaxation, reaching its peak shortly after mitral valve opening. Peak DIVPD was less than half in patients with DCM than in control subjects (1.2+/-0.6 versus 2.5+/-0.8 mm Hg, P<0.001). Dobutamine increased DIVPD in control subjects by 44% (P<0.001) but only by 23% in patients with DCM (P=NS). DIVPDs were the consequence of 2 opposite forces: a driving force caused by local acceleration, and a reversed (opposed to filling) convective force that lowered the total DIVPD by more than one third. In turn, local acceleration correlated with E-wave velocity and ejection fraction, whereas convective deceleration correlated with E-wave velocity and ventriculo:annular disproportion. Convective deceleration was highest among patients showing a restrictive filling pattern.

CONCLUSIONS

Patients with DCM show an abnormally low diastolic suction and a blunted capacity to recruit suction with stress. By raising the ventriculo:annular disproportion, chamber remodeling proportionally increases convective deceleration and adversely affects left ventricular filling. These previously unreported mechanisms of diastolic dysfunction can be studied by using Doppler echocardiography.

Doppler-Derived Ejection Intraventricular Pressure Gradients Provide a Reliable Assessment of Left Ventricular Systolic Chamber Function

BACKGROUND

Ejection intraventricular pressure gradients are caused by the systolic force developed by the left ventricle (LV). By postprocessing color Doppler M-mode (CDMM) images, we can measure noninvasively the ejection intraventricular pressure difference (EIVPD) between the LV apex and the outflow tract. This study was designed to assess the value of Doppler-derived EIVPDs as noninvasive indices of systolic chamber function.

METHODS AND RESULTS

CDMM images and pressure-volume (conductance) signals were simultaneously acquired in 9 minipigs undergoing pharmacological interventions and acute ischemia. Inertial, convective, and total EIVPD curves were calculated from CDMM recordings. Peak EIVPD closely correlated with indices of systolic function based on the pressure-volume relationship: peak elastance (within-animal R=0.98; between-animals R=0.99), preload recruitable stroke work (within-animal R=0.81; between-animals R=0.86), and peak of the first derivative of pressure corrected for end-diastolic volume (within-animal R=0.88; between-animals R=0.91). The correlation of peak inertial EIVPD with these indices was also high (all R>0.75). Load dependence of EIVPDs was studied in another 5 animals in which consecutive beats obtained during load manipulation were analyzed. During caval occlusion (40% EDV reduction), dP/dtmax, ejection fraction, and stroke volume significantly changed, whereas peak EIVPD remained constant. Aortic occlusion (40% peak LV pressure increase) significantly modified dP/dtmax, ejection fraction, and stroke volume; a nearly significant trend toward decreasing peak EIVPD was observed (P=0.06), whereas inertial EIVPD was unchanged (P=0.6). EIVPD beat-to-beat and interobserver variabilities were 2+/-12% and 5+/-11%, respectively.

CONCLUSIONS

Doppler-derived EIVPDs provide quantitative, reproducible, and relatively load-independent indices of global systolic chamber function that correlate closely with currently available reference methods.

Colour M-mode velocity propagation: a glance at intra-ventricular pressure gradients and early diastolic ventricular performance

The physiology of early-diastolic filling comprises ventricular performance and fluid dynamical principles. Elastic recoil and myocardial relaxation rate determine left ventricular early diastolic performance. The integrity of left ventricular synchrony and geometry is essential to maintain the effect of their timely action on early diastolic left ventricular filling. These factors not only are prime determinants of left ventricular pressure decay during isovolumic relaxation and immediately after mitral valve opening; they also instigate the generation of a sufficient intra-ventricular pressure gradient, which enhances efficient early diastolic left ventricular filling. Accurate assessment of diastolic (dys)function by non-invasive techniques has important therapeutic and prognostic implications but remains a challenge to the cardiologist. The evaluation of left ventricular relaxation by the standard Doppler echocardiographic parameters is hindered by their preload dependency. The colour M-mode velocity propagation of early diastolic inflow (Vp) correlates with intra-ventricular pressure gradients and is a largely preload independent index of ventricular diastolic performance. In this article, the physiologic background, utility and limitations of this promising new tool for the study of early diastolic filling are reviewed.