Diastolic function in chronic kidney disease

Chronic kidney disease (CKD) is characterized by clustered age-independent concentric left ventricular (LV) geometry, geometry-independent systolic dysfunction and age and heart rate-independent diastolic dysfunction. Concentric LV geometry is always associated with echocardiographic markers of abnormal LV relaxation and increased myocardial stiffness, two hallmarks of diastolic dysfunction. Non-haemodynamic mechanisms such as metabolic and electrolyte abnormalities, activation of biological pathways and chronic exposure to cytokine cascade and the myocardial macrophage system also impact myocardial structure and impair the architecture of the myocardial scaffold, producing and increasing reactive fibrosis and altering myocardial distensibility. This review addresses the pathophysiology of diastole in CKD and its relations with cardiac mechanics, haemodynamic loading, structural conditions, non-haemodynamic factors and metabolic characteristics. The three mechanisms of diastole will be examined: elastic recoil, active relaxation and passive distensibility and filling. Based on current evidence, we briefly provide methods for quantification of diastolic function and discuss whether diastolic dysfunction represents a distinct characteristic in CKD or a proxy of the severity of the cardiovascular condition, with the potential to be predicted by the general cardiovascular phenotype. Finally, the review discusses assessment of diastolic function in the context of CKD, with special emphasis on end-stage kidney disease, to indicate whether and when in-depth measurements might be helpful for clinical decision making in this context.

Cardioprotective Effect of Acute Intradialytic Exercise: A Comprehensive Speckle-Tracking Echocardiography Analysis

SIGNIFICANCE STATEMENT

Hemodialysis (HD) can lead to acute left ventricular (LV) myocardial wall motion abnormalities (myocardial stunning) due to segmental hypoperfusion. Exercise during dialysis is associated with favorable effects on central hemodynamics and BP stability, factors considered in the etiology of HD-induced myocardial stunning. In a speckle-tracking echocardiography analysis, the authors explored effects of acute intradialytic exercise (IDE) on LV regional myocardial function in 60 patients undergoing HD. They found beneficial effects of IDE on LV longitudinal and circumferential function and on torsional mechanics, not accounted for by cardiac loading conditions or central hemodynamics. These findings support the implementation of IDE in people with ESKD, given that LV transient dysfunction imposed by repetitive HD may contribute to heart failure and increased risk of cardiac events in such patients.

BACKGROUND

Hemodialysis (HD) induces left ventricular (LV) transient myocardial dysfunction. A complex interplay between linear deformations and torsional mechanics underlies LV myocardial performance. Although intradialytic exercise (IDE) induces favorable effects on central hemodynamics, its effect on myocardial mechanics has never been comprehensively documented.

METHODS

To evaluate the effects of IDE on LV myocardial mechanics, assessed by speckle-tracking echocardiography, we conducted a prospective, open-label, two-center randomized crossover trial. We enrolled 60 individuals with ESKD receiving HD, who were assigned to participate in two sessions performed in a randomized order: standard HD and HD incorporating 30 minutes of aerobic exercise (HDEX). We measured global longitudinal strain (GLS) at baseline (T0), 90 minutes after HD onset (T1), and 30 minutes before ending HD (T2). At T0 and T2, we also measured circumferential strain and twist, calculated as the net difference between apical and basal rotations. Central hemodynamic data (BP, cardiac output) also were collected.

RESULTS

The decline in GLS observed during the HD procedure was attenuated in the HDEX sessions (estimated difference, -1.16%; 95% confidence interval [95% CI], -0.31 to -2.02; P = 0.008). Compared with HD, HDEX also demonstrated greater improvements from T0 to T2 in twist, an important component of LV myocardial function (estimated difference, 2.48°; 95% CI, 0.30 to 4.65; P = 0.02). Differences in changes from T0 to T2 for cardiac loading and intradialytic hemodynamics did not account for the beneficial effects of IDE on LV myocardial mechanics kinetics.

CONCLUSIONS

IDE applied acutely during HD improves regional myocardial mechanics and might warrant consideration in the therapeutic approach for patients on HD.

Loss of left ventricular rotation is a significant determinant of functional mitral regurgitation

AIM

To evaluate insufficient rotational movement of the left ventricle (LV) as a potential novel mechanism for functional regurgitation of the mitral valve (FMR).

METHODS AND RESULTS

We compared reference subjects and patients with LV dysfunction (LVD, ejection fraction EF < 50%) with and without FMR (regurgitant volume RVol>10 ml). Subjects without structural mitral valve pathology undergoing cardiac MRI were evaluated. Delayed enhancement, global LV remodeling parameters, systolic twist and torsion were measured (using manual and novel automated cardiac MRI tissue-tracking). The study included 117 subjects with mean ± SD age 50.4 ± 17.8 years, of which 30.8% were female. Compared to subjects with LVD without FMR (n = 31), those with FMR (n = 37) had similar clinical characteristics, diagnoses, delayed enhancement, EF, and longitudinal strain. Subjects with FMR had significantly larger left ventricles (EDVi:136.6 ± 41.8 vs 97.5 ± 26.2 ml/m, p < 0.0001) with wider separation between papillary muscles (21.1 ± 7.6 vs 17.2 ± 5.7 mm, p = 0.023). Notably, they had lower apical (p < 0.0001) but not basal rotation and lower peak systolic twist (3.1 ± 2.4° vs 5.5 ± 2.5°, p < 0.0001) and torsion (0.56 ± 0.38°/cm vs 0.88 ± 0.52°/cm, p = 0.004). In a multivariate model for RVol including age, gender, twist, LV end-diastolic volume, sphericity index and separation between papillary muscles, only gender, volume and twist were significant. Twist was the most powerful correlate (beta -2.23, CI -3.26 to -1.23 p < 0.001). In patients with FMR, peak systolic twist negatively correlates with RVol (r = -0.73, p < 0.0001).

CONCLUSION

Reduced rotational systolic LV motion is significantly and independently associated with RVol among patients with FMR, suggesting a novel pathophysiological mechanism and a potential therapeutic target.

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.

Concomitant systolic and diastolic alterations during chronic hypertension in pig

The mechanical and cellular relationships between systole and diastole during left ventricular (LV) dysfunction remain to be established. LV contraction-relaxation coupling was examined during LV hypertrophy induced by chronic hypertension. Chronically instrumented pigs received angiotensin II infusion for4weeks to induce chronic hypertension (133 ± 7 mmHg vs 98 ± 5 mmHg for mean arterial pressure at Day 28 vs 0, respectively) and LV hypertrophy. LV function was investigated with the instrumentation and echocardiography for LV twist-untwist assessment before and after dobutamine infusion. The cellular mechanisms were investigated by exploring the intracellular Ca²⁺ handling. At Day 28, pigs exhibited LV hypertrophy with LV diastolic dysfunction (impaired LV isovolumic relaxation, increased LV end-diastolic pressure, decreased and delayed LV untwisting rate) and LV systolic dysfunction (impaired LV isovolumic contraction and twist) although LV ejection fraction was preserved. Isolated cardiomyocytes exhibited altered shortening and lengthening. Interestingly, contraction-relaxation coupling remained preserved both in vivo and in vitro during LV hypertrophy. LV systolic and diastolic dysfunctions were associated to post-translational remodeling and dysfunction of the type 2 cardiac ryanodine receptor/Ca²⁺ release channel (RyR2), i.e., PKA hyperphosphorylation of RyR2, depletion of calstabin 2 (FKBP12.6), RyR2 leak and hypersensitivity of RyR2 to cytosolic Ca²⁺ during both contraction and relaxation phases. In conclusion, LV contraction-relaxation coupling remained preserved during chronic hypertension despite LV systolic and diastolic dysfunctions. This implies that LV diastolic dysfunction is accompanied by LV systolic dysfunction. At the cellular level, this is linked to sarcoplasmic reticulum Ca²⁺ leak through PKA-mediated RyR2 hyperphosphorylation and depletion of its stabilizing partner.

Left ventricular twist mechanics in the context of normal physiology and cardiovascular disease: a review of studies using speckle tracking echocardiography

The anatomy of the adult human left ventricle (LV) is the result of its complex interaction with its environment. From the fetal to the neonatal to the adult form, the human LV undergoes an anatomical transformation that finally results in the most complex of the four cardiac chambers. In its adult form, the human LV consists of two muscular helixes that surround the midventricular circumferential layer of muscle fibers. Contraction of these endocardial and epicardial helixes results in a twisting motion that is thought to minimize the transmural stress of the LV muscle. In the healthy myocardium, the LV twist response to stimuli that alter preload, afterload, or contractility has been described and is deemed relatively consistent and predictable. Conversely, the LV twist response in patient populations appears to be a little more variable and less predictable, yet it has revealed important insight into the effect of cardiovascular disease on LV mechanical function. This review discusses important methodological aspects of assessing LV twist and evaluates the LV twist responses to the main physiological and pathophysiological states. It is concluded that correct assessment of LV twist mechanics holds significant potential to advance our understanding of LV function in human health and cardiovascular disease.

Increased LV apical untwist during preload reduction in healthy humans: an echocardiographic speckle tracking study during lower body negative pressure

We sought to investigate the effect of reduced preload on left ventricle (LV) untwist and early diastolic filling in healthy individuals. Twelve healthy men, 22 (22, 23) years of age, were examined at rest and during applied lower body negative pressure (LBNP) of −20 mmHg and −40 mmHg, respectively. Regional untwist and untwist rate during IVRT were calculated at LV basal, papillary, subpapillary, and apical short axis levels by two dimensional speckle tracking echocardiography. Left ventricle early diastolic filling was assessed by transmitral E-wave (E) peak velocity by pulsed Doppler and flow propagation velocity (Vp) by color M-mode Doppler and early diastolic pulsed Doppler tissue velocities (E') from septal and lateral mitral annulus. From rest to LBNP −40 mmHg, the LV untwist and untwist rate at subpapillary level increased from 2.3 (1.4, 3.5) to 4.5 (3.1, 7.6) degrees and from −36 (−51, −25) to −69 (−127, −42) °/s (P < 0.001, P = 0.003), respectively, while apical untwist and untwist rate increased from 3.9 (2.3, 4.3) to 7.6 (6.4, 10.5) degrees and from −51 (−69, −40) to −118 (−170, −84) °/s (P < 0.001, P < 0.001), respectively. Since untwist and untwist rate at the basal level were unchanged, this created markedly larger base to apical untwist and untwist rate gradients from rest to LBNP −40 mmHg. E, Vp, and E' were reduced by 34, 32, and 39%, respectively. LV untwist and untwist rate during IVRT were increased at apical levels, which might be a physiological mechanism to minimize the impairment in LV early diastolic filling during preload reduction.

From speckle tracking echocardiography to torsion: research tool today, clinical practice tomorrow

PURPOSE OF REVIEW

Speckle tracking is the latest available technology in echocardiography. However, the technology is still mainly used as a research tool. The potential applications of speckle tracking are many, including cardiac synchronization, regional wall motion analysis, and in the areas of cardiac mechanic studies. This review presents the background theory of speckle tracking echocardiography (STE) and how this technology can be extended to velocity vector analysis, strain, and torsion measurements. The interpretations of these measurements are covered. We also present some potential applications in the critical care setting.

RECENT FINDINGS

Speckle tracking is almost always available in high-end ultrasound machines. The technology has been applied to velocity vector analysis, strain and strain rate measurements, and twist and torsion analysis. Torsion analysis and velocity vector analyses are impossible without using speckle tracking. Speckle tracking-derived strain is superior to tissue Doppler strain because it is angle-independent. A number of studies demonstrated that STE is useful in left and right heart assessments and can be used in assessing preload and afterload.

SUMMARY

Speckle tracking can be used to measure instantaneous myocardial contractility, strain, and left ventricular torsion. It is still a research tool at present, but shows the promise of being a clinical tool in the future.

Left ventricular twist and untwist rate provide reliable measures of ventricular function in myocardial ischemia and a wide range of hemodynamic states

Although rotational parameters by speckle tracking echocardiography (STE) have been previously compared to sonomicrometry and cardiac magnetic resonance imaging, few have examined the relationship between left ventricular (LV) rotational mechanics and intraventricular measures of load-independent contractility, LV stiffness, or ventriculoarterial coupling. The aim of this study was to compare the changes in LV rotational indices to intraventricular pressure–volume (PV) relationships under a range of inotropic states induced by pharmacological interventions, acute ischemia, and changes in preload. In nine pigs, simultaneous echocardiographic imaging and LVPV measurements were performed during pharmacologically induced high or low inotropy and during acute ischemia by ligation of the left anterior descending coronary artery (LAD). Maximal ventricular elastance (E_max), arterial elastance (E_a), ventricular–arterial coupling (E_max/E_a), dP/dt, tau, and other hemodynamic parameters were determined. Dobutamine and esmolol infusions led to inversely correlated changes in hemodynamic measurements of LV function. Apical but not basal rotation and diastolic rotation rate were decreased by esmolol and increased by dobutamine. The LV twist correlates well with E_max (r = 0.83) and E_max/E_a (r = 0.80). Apical diastolic rotation rate also correlates with dP/dt_min (r = −0.63), τ (r = −0.81), and LV stiffness (r = −0.52). LAD ligation decreased systolic and diastolic LV rotation in apical (P < 0.05), but not basal myocardium. Occlusion of the inferior vena cava, to reduce preload, increased apical rotation in systole and diastole. LV rotational parameters measured by STE provide quantitative and reproducible indices of global LV systolic and diastolic function during acute changes in hemodynamics.

Worsening left ventricular apical peak strain early after right ventricular pacing

We aimed to determine the effect of short-term right ventricle pacing (RV) on left ventricle (LV) mechanics using speckle tracking analysis. Conventional echocardiography and two-dimensional strain imaging was studied in 38 patients, mean age 81.6 ± 7.0, that had undergone pacemaker placement and were greater than 90% ventricularly paced. Mean duration of 24 months of RV pacing resulted in a significant decline in: LV apical diastolic rotational velocities (-59.0 ± -38.9 °/s to -28.0 ± -11.5 °/s, p 0.02), peak strain in the LV apical septal wall (-15.6 ± 8.5 to -13.5 ± 7.6, p 0.02), peak strain in LV apical lateral wall (-13.4 ± 8.9 to -11.4 ± 7.3, p 0.02). Thus, with only 24 months of RV pacing, there was a significant decline in peak strain of the LV apex and in apical diastolic rotational velocity that could account for eventual decline in left ventricular function.

The role of 3D wall motion tracking in heart failure

Heart failure is a major health problem in developed countries and a growing one in developing countries. Cardiac remodeling in heart failure affects myocardial mechanics, which requires comprehensive evaluation in three dimensions. The novel technique of 3D wall motion tracking applies speckle tracking technology to full volume, 3D echocardiographic datasets. Quantification of conventional and novel left ventricular (LV) parameters including volumes, ejection fraction, global and regional 3D strain, endocardial area strain, twist, and dyssynchrony, and identification of the site of latest mechanical activation are feasible on the basis of a single acquisition of a full-volume dataset. Clinical applications of 3D wall motion tracking include the assessment of global and regional LV performance in ischemic and nonischemic heart diseases, evaluation of mechanics in cardiomyopathies and congenital heart disease, potential selection of patients for cardiac resynchronization therapy and prediction of their response, and detection of subclinical cardiac dysfunction in diseases with likelihood of progression to heart failure. Technological advances with improvement in spatial and temporal resolution of this novel imaging modality are expected. Although 3D wall motion tracking is still in its infancy, this method has begun to provide new insights into LV mechanics and has already found clinical applications. Future developments in 3D assessment of right ventricular and myocardial layer-specific mechanics are awaited.

The impact of isometric handgrip testing on left ventricular twist mechanics

Left ventricular (LV) rotation occurs due to contraction of obliquely oriented myocardial fibres. Left ventricular twist (LVT) results from rotation of the apex and base in opposite directions. Although LVT is altered in various cardiac diseases, physiological factors that affect LVT remain incompletely understood. Isometric handgrip testing (IHGT), a well-established laboratory-based technique to increase LV afterload, was performed for 3 min at 40% maximum force generation in healthy human subjects (n = 18, mean age 29.7 ± 2.7 years). Speckle-tracking echocardiography was used to measure LV volumes, LV apical and basal rotation, peak systolic LVT and peak early diastolic untwisting rate (UTR) at rest and at peak IHGT. IHGT led to significant increase in systemic blood pressure (systolic, 120.6 ± 9.7 vs. 155.6 ± 14.5 mmHg, P < 0.001; diastolic, 67.5 ± 6.4 vs. 94.1 ± 21.1 mmHg, P < 0.001) and LV end-systolic volume (44.2 ± 7.8 vs. 50.5 ± 10.8 ml, P = 0.005), as well as a significant increase in heart rate (62.8 ± 11.7 vs. 84.7 ± 13.8 beats min−1; P < 0.001). IHGT produced a significant acute reduction in LV stroke volume (63.9 ± 12.0 vs. 49.4 ± 7.8 ml, P < 0.001). In this setting, there was a significant decrease in peak systolic apical rotation (11.9 ± 3.0 vs. 8.6 ± 2.2 deg, P < 0.001) and a resultant 25% decrease in peak systolic LVT (16.6 ± 2.8 vs. 12.5 ± 2.8 deg, P < 0.001). The magnitude of peak early diastolic UTR did not change (−114.5 ± 26.4 vs. −110.6 ± 39.8 deg s−1, P = 0.71). Peak systolic apical rotation and LVT decrease during IHGT in healthy humans. This impairment of LV twist mechanics may in part underlie the LV dysfunction that can occur in the clinical context of acute increase in afterload.

Left ventricular twist is load-dependent as shown in a large animal model with controlled cardiac load

BACKGROUND

Left ventricular rotation and twist can be assessed noninvasively by speckle tracking echocardiography. We sought to characterize the effects of acute load change and change in inotropic state on rotation parameters as a measure of left ventricular (LV) contractility.

METHODS

Seven anesthetised juvenile pigs were studied, using direct measurement of left ventricular pressure and volume and simultaneous transthoracic echocardiography. Transient inflation of an inferior vena cava balloon (IVCB) catheter produced controlled load reduction. First and last beats in the sequence of eight were analysed with speckle tracking (STE) during the load alteration and analysed for change in rotation/twist during controlled load alteration at same contractile status. Two pharmacological inotropic interventions were also included to examine the same hypothesis in additionally conditions of increased and decreased myocardial contractility in each animal. Paired comparisons were made for different load states using the Wilcoxon's Signed Rank test.

RESULTS

The inferior vena cava balloon occlusion (IVCBO) load change compared for first to last beat resulted in LV twist increase (11.67° ±2.65° vs. 16.17° ±3.56° respectively, p < 0.004) during the load alteration and under adrenaline stimulation LV twist increase 12.56° ±5.1° vs. 16.57° ±4.6° (p < 0.013), and though increased, didn't reach significance in negative inotropic condition. Untwisting rate increased significantly at baseline from -41.7°/s ±41.6°/s vs.-122.6°/s ±55.8°/s (P < 0.039) and under adrenaline stimulation untwisting rate increased (-55.3°/s ±3.8°/s vs.-111.4°/s ±24.0°/s (p < 0.05), but did not systematically changed in negative inotropic condition.

CONCLUSIONS

Peak systolic LV twist and peak early diastolic untwisting rate are load dependent. Differences in LV load should be included in the interpretation when serial measures of twist are compared.

Load independence of two-dimensional speckle-tracking-derived left ventricular twist and apex-to-base rotation delay in nonischemic dilated cardiomyopathy: implications for left ventricular dyssynchrony assessment

BACKGROUND

Left ventricular (LV) twist mechanics are a promising, sensitive tool for assessing pathophysiologic changes in patients with systolic heart failure. Although LV twist is known to be load dependent in healthy volunteers, this has not been examined in patients with "long-standing" dilated cardiomyopathy (DCM). The aim of this study was to determine whether LV twist remains load dependent in the setting of long-standing, nonischemic DCM.

METHODS

Thirty-four patients with DCM with baseline LV ejection fractions (LVEFs) < 40% and 13 subjects with preserved LVEFs (≥50%) were enrolled. After baseline measurements, pneumatic compression of the lower extremities (Pcom) was used to increase LV afterload. Subsequently, sublingual nitroglycerin (SL-NG) was administered to modify preload. Conventional echocardiographic parameters, LV end-systolic wall stress, net LV twist angle, and apex-to-base-rotation delay (ABRD) were assessed under each condition.

RESULTS

In patients with DCM, although LV end-systolic wall stress significantly increased under Pcom (196.9 ± 64.9 g/m(2) at baseline vs 231.8 ± 78.9 g/m(2) under Pcom, P < .017) and decreased after SL-NG application (231.8 ± 78.9 g/m(2) under Pcom vs 197.4 ± 67.4 g/m(2) after SL-NG, P < .017), net LV twist angle and ABRD showed no significant changes depending on LV loading condition (for LV twist, 7.63 ± 4.47° at baseline vs 7.03 ± 4.13° under Pcom vs 7.35 ± 4.36° after SL-NG, P = 0.65; for ABRD, 16.56 ± 13.81% at baseline vs 17.19 ± 14.81% under Pcom vs 15.95 ± 13.27% after SL-NG, P = .53). Careful examination of individual patient data revealed that LV twist was load independent when patients had LV twist < 12°. ABRD was also found to be load independent, but only in patients with LVEFs < 34%. In contrast, LV twist and ABRD were load dependent in patients with preserved LVEFs.

CONCLUSIONS

LV twist and its component, ABRD, had relatively load insensitive properties in patients with long-standing DCM and can be used in future clinical trials as load-independent indexes of LV dyssynchrony.

[State of the art: new developments in cardiac imaging]

Cardiac imaging continues to reveal new anatomical and functional insights into heart disease. In echocardiography, both transesophageal and transthoracic three-dimensional imaging have been fully developed and optimized, and the value of the techniques that have increased our understanding of cardiac mechanics and ventricular function is well established. At the same time, the healthcare industry has released new devices onto the market which, although they are easier to use, have limitations that restrict their use for routine assessment. Tomography's diagnostic and prognostic value in coronary artery disease continues to increase while radiation exposure becomes progressively lower. With cardiac magnetic resonance imaging, myocardial injury and recovery in ischemic heart disease and following acute coronary syndrome can be monitored in exquisite detail. The emergence of new combined tomographic and gamma camera techniques, exclusively developed for nuclear cardiology, have improved the quality of investigations and reduced radiation exposure. The hybrid or fusion images produced by combining different techniques, such as nuclear cardiology techniques and tomography, promise an exciting future.