Radial Thickening Research Articles

Young Investigator Award session - Basic Science: 11/12/2013, 12:45-13:45 * Location: Manisa

Young Investigator Award session - Basic Science: 11/12/2013, 12:45-13:45 * Location: Manisa

Small but thick enough – the Arabidopsis hypocotyl as a model to study secondary growth

The continuous production of vascular tissues through secondary growth results in radial thickening of plant organs and is pivotal for various aspects of plant growth and physiology, such as water transport capacity or resistance to mechanical stress. It is driven by the vascular cambium, which produces inward secondary xylem and outward secondary phloem. In the herbaceous plant Arabidopsis thaliana (Arabidopsis), secondary growth occurs in stems, in roots and in the hypocotyl. In the latter, radial growth is most prominent and not obscured by parallel ongoing elongation growth. Moreover, its progression is reminiscent of the secondary growth mode of tree trunks. Thus, the Arabidopsis hypocotyl is a very good model to study basic molecular mechanisms of secondary growth. Genetic approaches have succeeded in the identification of various factors, including peptides, receptors, transcription factors and hormones, which appear to participate in a complex network that controls radial growth. Many of these players are conserved between herbaceous and woody plants. In this review, we will focus on what is known about molecular mechanisms and regulators of vascular secondary growth in the Arabidopsis hypocotyl.

Stress Echocardiography in Regurgitant Valve Disease

Because of its wide availability, low cost, versatility, and clinical use, stress echocardiography has become increasingly recognized as a valuable tool in the assessment of patients with regurgitant valvular heart disease. Exercise testing is favored compared with pharmacological stress testing for risk stratification in asymptomatic patients and can identify what might otherwise be considered as a moderate valve disease. It has been shown to provide insights into exertional symptoms disproportionate to resting hemodynamics in these patients and to facilitate individual risk stratification. Aggravation of valvular regurgitation severity, exercise-induced pulmonary hypertension (PHT), impaired left ventricular (LV) contractile reserve, inducible ischemia, dynamic LV dyssynchrony, and altered exercise capacity, together with the development of symptoms during exercise echocardiography, provide the clinician with straightforward prognostic information, therefore enabling a more accurate definition of the optimal timing of intervention in patients with valvular regurgitation.1,2 In contrast, dobutamine stress echocardiography has little value in cases of valvular regurgitation. Dobutamine infusion is almost systematically associated with a decrease in the severity of regurgitation; however, it might be of interest in the detection of LV contractile reserve and inducible ischemia. The most common form of exercise used in conjunction with echocardiography is immediate postexercise imaging on a treadmill or upright bicycle ergometer. However, semisupine exercise testing on an appropriate tilted table allows continuous echocardiographic monitoring, which represents an advantageous tool for quantifying changes in valvular regurgitation severity, LV function, and pulmonary pressure (Table). This exercise stress echocardiography modality (ie, per-exercise echocardiography) is the most used in Europe, and we strongly suggest this approach in the setting of valvular heart disease to detect evanescent changes. A symptom-limited graded exercise test is recommended, and ≥80% of the age-predicted upper heart rate should be reached in the absence of symptoms. The test is adapted to the clinical conditions …

Myofiber prestretch magnitude determines regional systolic function during ectopic activation in the tachycardia-induced failing canine heart.

Electrical dyssynchrony leads to prestretch in late-activated regions and alters the sequence of mechanical contraction, although prestretch and its mechanisms are not well defined in the failing heart. We hypothesized that in heart failure, fiber prestretch magnitude increases with the amount of early-activated tissue and results in increased end-systolic strains, possibly due to length-dependent muscle properties. In five failing dog hearts with scars, three-dimensional strains were measured at the anterolateral left ventricle (LV). Prestretch magnitude was varied via ventricular pacing at increasing distances from the measurement site and was found to increase with activation time at various wall depths. At the subepicardium, prestretch magnitude positively correlated with the amount of early-activated tissue. At the subendocardium, local end-systolic strains (fiber shortening, radial wall thickening) increased proportionally to prestretch magnitude, resulting in greater mean strain values in late-activated compared with early-activated tissue. Increased fiber strains at end systole were accompanied by increases in preejection fiber strain, shortening duration, and the onset of fiber relengthening, which were all positively correlated with local activation time. In a dog-specific computational failing heart model, removal of length and velocity dependence on active fiber stress generation, both separately and together, alter the correlations between local electrical activation time and timing of fiber strains but do not primarily account for these relationships.

Relationship of Multidirectional Myocardial Strain with Radial Thickening and Ejection Fraction and Impact of Left Ventricular Hypertrophy: A Study in a Community‐Based Cohort

Left ventricular (LV) systolic strain provides additional prognostic value to LV ejection fraction (LVEF) and wall motion analysis. However, the relationship between myocardial multidirectional strain and LVEF, and the effect of LV hypertrophy on this relationship, are not completely understood especially in unselected populations. LV global longitudinal (εL ) and circumferential (εC ) systolic strain analysis was performed by two-dimensional speckle tracking echocardiography in 215 participants from a community-based study. LV radial wall thickening was measured as global radial strain (εR ), and LVEF was assessed by biplane Simpson's method. εR was significantly associated with εC (β = -0.56, P < 0.01) and with εL (β = -0.18, P < 0.01). The contribution of εL to εR was especially evident in subjects with lower εC and in presence of LV hypertrophy (β = -0.30, P < 0.01). εL and εC were significantly associated with LVEF (β = -0.36 and β = -0.49, both P < 0.01) independent of LV mass and other confounders, and their interaction significantly improved the prediction of LVEF (R(2) -change = 0.14) but not of εR (R(2) -change = 0.002). εR is mainly related to εC with a smaller contribution of εL , which becomes especially evident in subjects with lower εC and in presence of LV hypertrophy. Therefore, radial thickening may not detect subclinical LV longitudinal function reduction in normal ventricles and when εC is preserved. While a reduction in εL has a limited impact on εR , it exerts a greater effect on global LVEF, therefore for a more accurate LVEF prediction both εL and εC need to be considered.

Three-Dimensional Reconstruction of the Functional Strain-Line Pattern in the Left Ventricle From 3-Dimensional Echocardiography

Advances in 3-dimensional (3D) echocardiography offer a rapid, effective imaging technique with adequate temporal and spatial resolution for left ventricular motion assessment. 3D multidirectional tracking of the endocardial left ventricular layer has shown that the functional pattern of directional strain arrangement during cardiac contraction closely relates with the structural architecture of the myocardial helical muscle fiber orientation.1 In a similar manner, we carried out segmentation tracking of the endocardial-epicardial layers in 10 healthy young athletes (nonprofessional athletes, enrolled at the Sport Medicine Center of the University of Florence, Italy, training 2–3 days a week for 2 hours daily; all exhibiting an excellent echographic window) to evaluate the 3D strain pattern over the whole myocardium thickness and to compare with the hypothesized underlying fiber architecture. An echocardiographic 3D full-volume image of the left ventricular was recorded by a Philips IE33 machine (frame rate, 15–30 Hz). Imaging data were processed by 3D feature tracking (4DLVA 3.0; TomTec Gmbh, Unterschleissheim, Germany), and the endocardial and epicardial tracked surfaces were exported for the following principal strain analysis.1 Principal strain analysis allows to define the direction along which the main contractile strain (S1) develops, accompanied by a secondary strain (S2) that is typically of much …

Gametogenesis and Auxospore Development in Actinocyclus (Bacillariophyta)

cGametogenesis and auxospore development have been studied in detail in surprisingly few centric diatoms. We studied the development of sperm, eggs and auxospores in Actinocyclus sp., a radially symmetrical freshwater diatom collected from Japan, using LM and electron microscopy of living cultures and thin sections. Actinocyclus represents a deep branch of the ‘radial centric’ diatoms and should therefore contribute useful insights into the evolution of sexual reproduction in diatoms. Spermatogenesis was examined by LM and SEM and involved the formation of two spermatogonia (sperm mother-cells) in each spermatogonangium through an equal mitotic division. The spermatogonia produced a reduced ‘lid’ valve, resembling a large flat scale with irregular radial thickenings. Sperm formation was merogenous, producing four sperm per spermatogonium, which were released by dehiscence of the ‘lid’ valve. The sperm were spindle-shaped with numerous surface globules and, as usual for diatoms, the single anterior flagellum bore mastigonemes. One egg cell was produced per oogonium. Immature eggs produced a thin layer of circular silica scales before fertilization, while the eggs were still contained within the oogonium. Sperm were attracted in large numbers to each egg and were apparently able to contact the egg surface via a gap formed between the long hypotheca and shorter epitheca of the oogonium and a small underlying hole in the scale-case. Auxospores expanded isodiametrically and many new scales were added to its envelope during expansion. Finally, new slightly-domed initial valves were produced at right angles to the oogonium axis, after a strong contraction of the cell away from the auxospore wall. At different stages, Golgi bodies were associated with chloroplasts or mitochondria, contrasting with the constancy of Golgi–ER–mitochondrion (G-ER-M) units in some other centric diatoms, which has been suggested to have phylogenetic significance. Electron-dense bodies in the vacuole of Actinocyclus are probably acidocalcisomes containing polyphosphate.

Left ventricular myocardial performance assessed by 2-dimensional speckle tracking echocardiography in patients with sickle cell crisis

BackgroundThe status of left ventricle in sickle cell anemia presenting in sickle crisis and follow up has been minimally studied in past. To determine the left ventricular (LV) myocardial performance in these patients, we performed the study to assess two dimensional strains imaging which allowed a rapid and an accurate analysis of global and regional LV myocardial performance in longitudinal, radial, and circumferential directions. MethodsIn this prospective study, 2-dimensional echocardiography (2DE) images of the LV were obtained in 52 subjects which included 32 patients (23 ± 8yrs, 16 male) with homozygous sickle cell anemia (SCA) in sickle cell crisis and 20 healthy controls (23 ± 5 yrs, 11 male) using apical 4-chamber and parasternal short-axis at the basal, mid, and apical levels. Of these 32 patients, 2DE was performed again in 18 patients in follow up (8 months ± 5 days). Longitudinal, circumferential and radial strains (LS, CS and RS respectively) were quantified and compared in an 18-segment model using a novel speckle tracking system (2D Cardiac Performance Analysis, TomTec Imaging System, Munich, Germany). ResultsThere was no significant difference in LV ejection fraction between both the groups (59.32 ± 12.6 vs. 52.3 ± 7.9; p-value > 0.05). In comparison with normal controls and follow up of sickle cell patients, peak LS was significantly attenuated in the subendocardial and subepicardial regions during sickle cell crisis (p < 0.05). However, a significant reduction in circumferential strain was evident only in subepicardial region (p < 0.001). Also patients in sickle cell crisis showed significantly higher radial strain parameters than controls (p < 0.001). ConclusionPatients with SCA presenting in sickle cell crisis have reduced longitudinal shortening. LV myocardial performance remains unaltered due to relatively preserved circumferential shortening and increased radial thickening.

Abstract 548: Variations in Venous Wall Strain Can Be Modeled and Measured Using IVUS-Derived Elastography

Objectives: Iliofemoral venous outflow stenting has been used to treat both acute and chronic venous thrombosis. It may be beneficial to understand the properties of the normal venous wall and the flow through collapsible tubes to develop new stent technology and improve long-term patency. We hypothesize that radial and circumferential strain can be modeled and measured using intravascular ultrasound (IVUS) techniques to describe venous geometry and asymmetric vessel wall characteristics. Methods: A hydrogel phantom was used to mimic the mechanical properties of a homogeneous vein, including geometry and wall compliance. Radio-frequency (RF) echo frames were acquired using a modified IVUS system with an 8.5 Mhz catheter. All RF signals were digitized to 14 bits at 50 MHz. Radial strain was estimated by applying an intensity matching, image registration based algorithm to the digitized frames. Results: The radial strain images (Figure 1) show increasing positive strain (radial wall thickening) on the top and bottom of the phantom with decreasing negative values (radial wall thinning) at either side. Results suggest an asymmetric compression pattern typical of a vessel collapsing under negative pressure. Conclusions: In conclusion, our data suggest that novel strain analysis can be performed on a phantom vessel consistent with the mechanical properties of the venous system. Further work with venous elastography will help define the mechanical properties of the venous wall and facilitate the development of new stent technology to treat venous disease.

Clinical feasibility of targeted cardiac resynchronization lead delivery using a 3D MRI cardiac model

Background Cardiac resynchronization therapy (CRT) aims to reduce dyssynchronous contraction through simultaneous pacing of the right ventricular (RV) septum and left ventricular (LV) lateral wall. Up to 40% of patients do not respond, largely attributed to lack of dysynchrony and/ or transmural scar at pacing sites. In this pilot study we tested the feasibility of guiding LV and RV leads to “optimal” segmental targets using a MRI-based 3D surface rendered cardiac model. Methods Ten consecutive patients planned for CRT were recruited. All patients underwent cardiac MRI inclusive of cine and delayed enhancement (DE) imaging using a 3T scanner. A blinded interpreter determined the time to maximal radial wall thickening (TmWT) and myocardial scar burden for each of 16 segments. All potential LV lead targets were ranked according to scar burden (lowest first) and then sub-ranked by TmWT (highest first). All potential RV lead targets were ranked according to scar burden (lowest first). These rankings were encoded onto a surface rendered cardiac model, displayed in standard fluoroscopic views (Figure 1A) and used to direct lead placement by fluoroscopy. A cardiac gated CT was then performed at a 1-month follow-up visit (Figure 1B) to assess procedural success for target achievement. Results

Myocardial Deformation Imaging

Myocardial deformation imaging is a novel echocardiographic method for assessment of global and regional myocardial function. As this technology has evolved, it has been applied to an increasing number of research questions, and the number of publications incorporating deformation imaging has grown in parallel. Although not yet sufficiently vetted for routine clinical use, these methods offer the long-term potential for more complete, accurate, and reproducible assessment of myocardial function. Evaluation of contractile function with echocardiography has traditionally been limited to volume-based assessment of ejection fraction (EF) and assessment of regional wall motion or visual estimation of regional thickening. These methods have suffered from lack of reproducibility and standardization and are generally considered to be extremely sensitive to loading conditions. These limitations have led to an interest in techniques that provide more objective and reproducible measures of contractile function. During systole, the ventricular myocardium simultaneously shortens in the longitudinal and circumferential planes and thickens in the radial plane, with reciprocal changes in diastole (Figure). Deformation imaging, in the broadest sense, allows for more direct assessment of myocardial muscle shortening and lengthening throughout the cardiac cycle by assessing regional myocardial strain and strain rate. Strain is defined as the change in length of a segment of myocardium relative to its resting length and is expressed as a percentage; strain rate is the rate of this deformation. Longitudinal and circumferential shortening results in negative strain values, whereas radial thickening results in a positive strain value. Previously, assessment of myocardial strain could be performed with the use of sonomicrometry crystals, which can only be performed experimentally1 or with magnetic resonance imaging–based myocardial tagging,2,3 which is limited by relatively low temporal resolution and the limited availability and expense of cardiac magnetic resonance imaging. Extension of these techniques to echocardiography has allowed …

An ultrastructural study of the araucarian pollen grain Cyclusphaera radiata Archangelsky from the Albian of Patagonia

The araucarian pollen grain Cyclusphaera radiata Archangelsky is emended based on newly discovered material from the Piedra Clavada Formation of Albian age in Santa Cruz province, Argentina. The general morphology and ultrastructure of the pollen were studied by means of transmitted light, scanning, and transmission electron microscopy. C. radiata is discoid with an equatorial thickening and two large opposite apertures, with radial thickenings in one of them and two central apertural occlusive opercula-like structures. Beneath there is a thick amorphous electron-dense nexine. The combination of characters seen in this pollen type is very unusual, and no parallels are known in fossil or extant gymnosperm grains. Functional interpretation of the apertural exine suggests that the radial thickenings and apertural membranes were involved in harmomegthy, the opercula-like structures in germination, and the apertural nexine perhaps as a strengthening layer. A hypothetical pollination mechanism is also presented for C. radiata. The paleobiogeography of this taxon shows that during the Mesozoic, the plants that produced these grains inhabited an extensive area of Gondwana that included South America, Africa, India and Antarctica.

Abstract 9547: Tissue Doppler and Strain Imaging Can Facilitate Weaning Decisions in Patients with Evidence of Cardiac Recovery Suring Mechanical Ventricular Support

Background: Echocardiographic monitoring of cardiac size and function during “off-pump” trials is the cornerstone for detection of cardiac recovery during mechanical unloading. Parameters such as left ventricular (LV) diameters and LVEF are helpful to predict the outcome after possible LV assist device (LVAD) removal. However, high inter-observer variability and load dependency of EF measurements are important limitations. Because velocity parameters measurable by tissue Doppler and strain imaging are more reliable for estimation of LV function, we assessed their usefulness for evaluation of recovery. Methods: Pulsed-wave tissue Doppler (PW-TD) measurements of systolic wall motion peak velocities (Sm) at the basal posterior wall were performed since 1999 during all “off-pump” trials before LVAD removal and at all follow-up controls of post-weaning cardiac function. Since 2005, 2D strain and strain rate (SR) measurements (radial, circumferential and longitudinal) were also performed before and after LVAD removal. The prospectively collected PW-TD and 2D strain data were evaluated for their usefulness to predict weaning successes. Results: Heart failure (HF) recurrence after LVAD removal occurred in 10 (31.3%) of 32 patients who underwent PW-TD. Longitudinal and radial Sm was lower in these 10 patients than in those with post-weaning cardiac stability (p &lt; 0.01) Stable patients showed Sm &gt; 8 cm/s. Off-pump Sm ≥ 8cm/s showed predictive values between 87 and 90% for 5 year post-weaning stability. Strain and SR measured in 23 patients revealed higher systolic values in patients with post-weaning stability (p &lt; 0.01). In stable patients global systolic strain and SR values were: ≥ 30% and ≥ 0.9/s for radial thickening, ≥ 15% and ≥ 0.8/s for circumferential shortening, ≥ 12% and ≥ 0.65/s for longitudinal shortening, respectively. Sm, strain and SR instability before and early after LVAD removal appeared predictive for post-weaning recurrence of HF. Conclusion: PW-TD and 2D-strain imaging allow distinction between patients with and without the potential to maintain cardiac stability after LVAD removal and can therefore be useful for evaluation of unloading-induced cardiac recovery and also for prognostic assessments before and early after LVAD removal.

Impaired cardiac function in chronic fatigue syndrome measured using magnetic resonance cardiac tagging

ObjectivesImpaired cardiac function has been confirmed in patients with chronic fatigue syndrome (CFS). Magnetic resonance cardiac tagging is a novel technique that assesses myocardial wall function in vivo. We hypothesized that patients with CFS may have impaired development and release of myocardial torsion and strain.MethodsCardiac morphology and function were assessed using magnetic resonance imaging and cardiac tagging methodology in 12 CFS patients (Fukuda) and 10 matched controls.ResultsCompared to controls, the CFS group had substantially reduced left ventricular mass (reduced by 23%), end-diastolic volume (30%), stroke volume (29%) and cardiac output (25%). Residual torsion at 150% of the end-systolic time was found to be significantly higher in the patients with CFS (5.3 ± 1.6°) compared to the control group (1.7 ± 0.7°, P = 0.0001). End-diastolic volume index correlated negatively with both torsion-to-endocardial-strain ratio (TSR) (r = −0.65, P = 0.02) and the residual torsion at 150% end-systolic time (r = −0.76, P = 0.004), so decreased end-diastolic volume is associated with raised TSR and torsion persisting longer into diastole. Reduced end-diastolic volume index also correlated significantly with increased radial thickening (r = −0.65, P = 0.03) and impaired diastolic function represented by the ratio of early to late ventricular filling velocity (E/A ratio, r = 0.71, P = 0.009) and early filling percentage (r = 0.73, P = 0.008).ConclusionPatients with CFS have markedly reduced cardiac mass and blood pool volumes, particularly end-diastolic volume: this results in significant impairments in stroke volume and cardiac output compared to controls. The CFS group appeared to have a delay in the release of torsion.

The growth and morphology of core/shell heterostructured conical carbon fibers

Core/shell heterostructured conical carbon fibers with silicon-based cores and graphitic carbon sheaths have been grown on silicon carbide (SiC) surfaces exposed to the combustion of methane. The conical carbon fibers (CCFs), which taper from a circular base to a point, appear to form by two simultaneous growth processes, axial tip-growth and radial fiber thickening. Radial fiber thickening results from pyrolytic carbon deposition from gas-phase hydrocarbons. Oxidation of SiC surfaces is proposed to produce gas-phase silicon oxides, which feed axial tip-growth and install the silicon-based core. The unusual morphology of the CCFs, including bending, branching, curving and tapering, is proposed to result from the action and interplay of these two simultaneous processes.

Quantification of Left Ventricular Longitudinal Strain, Strain Rate, Velocity, and Displacement in Healthy Horses by 2‐Dimensional Speckle Tracking

The quantification of equine left ventricular (LV) function is generally limited to short-axis M-mode measurements. However, LV deformation is 3-dimensional (3D) and consists of longitudinal shortening, circumferential shortening, and radial thickening. In human medicine, longitudinal motion is the best marker of subtle myocardial dysfunction. To evaluate the feasibility and reliability of 2-dimensional speckle tracking (2DST) for quantifying equine LV longitudinal function. Ten healthy untrained trotter horses; 9.6 ± 4.4 years; 509 ± 58 kg. Prospective study. Repeated echocardiographic examinations were performed by 2 observers from a modified 4-chamber view. Global, segmental, and averaged peak values and timing of longitudinal strain (SL), strain rate (SrL), velocity (VL), and displacement (DL) were measured in 4 LV wall segments. The inter- and intraobserver within- and between-day variability was assessed by calculating the coefficients of variation for repeated measurements. 2DST analysis was feasible in each exam. The variability of peak systolic values and peak timing was low to moderate, whereas peak diastolic values showed a higher variability. Significant segmental differences were demonstrated. DL and VL presented a prominent base-to-midwall gradient. SL and SrL values were similar in all segments except the basal septal segment, which showed a significantly lower peak SL occurring about 60 ms later compared with the other segments. 2DST is a reliable technique for measuring systolic LV longitudinal motion in healthy horses. This study provides preliminary reference values, which can be used when evaluating the technique in a clinical setting.

Quantification of in Vivo Left Ventricular Torsion and Principal Strains in Mouse Models of Hypertrophic and Dilated Cardiomyopathy

The deformations and twisting of the left ventricular (LV) wall, quantified by strain and torsion, provide insight into its regional and global contractile function. In this study, we investigated the influence of proteins entailing myocyte contractility and structural stability on ventricular biomechanics using mouse models with alterations in contractile proteins. The pattern and timing of LV strain and torsion in 2∼3 month mice that lack cardiac myosin binding protein-C (cMyBP-C-/-, n=6, cMyBP-C+/-, n=6), a thick filament-associated sarcomeric protein, and muscle LIM protein (MLP-/-, n=6), a cytoskeleton protein that is thought to be involved in transmission of mechanical stress, were evaluated against wild-type mice (n=6) in vivo using magnetic resonance imaging. Both cMyBP-C-/- and MLP-/- mice exhibited a severe depression in systolic function as indicated by decreased LV ejection fractions compared to wild-type mice. A significant reduction in LV torsion and principal strains E1 and E2, associated with radial wall thickening and circumferential shortening, respectively, were observed in cMyBP-C -/- and MLP-/- mice. Interestingly, reductions in LV torsion were also observed in heterozygous cMyBP-C null mice (cMyBP-C+/-). The time course of peak fiber torsion and strain appeared to be accelerated in cMyBP-C-/- mice, while peak strain development was slowed in MLP-/- mice. The lack of MyBP-C and MLP in the cardiac myocyte led to hypertrophic and dilated cardiomyopathy, respectively, and resulted in severe deficits in the overall contractile function of the heart. However, the pattern and time course of LV torsion and principal strain development appear to differ in these two models of heart failure, reflecting a contrast in the functional roles of cMyBP-C and MLP in the myocyte.

A new method for quantification of left ventricular systolic function using a corrected ejection fraction

Left ventricular ejection fraction (EF) is a suboptimal measure of ventricular function. Recent mathematical modelling of left ventricular contraction has shown that the EF is determined by both myocardial shortening (strain) and by end-diastolic wall thickness. Increasing end-diastolic wall thickness resulted in augmented radial wall thickening. This may result in a significant 'overestimation' of ventricular systolic function as assessed by the EF. This study proposes a new measure of ventricular systolic function, the corrected EF (EF(c)) to allow for the presence of concentric left ventricular hypertrophy (LVH). The study uses a new two-layer, three-dimensional mathematical model of ventricular contraction. Changes in end-diastolic wall thickness in addition to long-axis and mid-wall circumferential strain were modelled. Iso-strain lines were obtained where myocardial shortening (strain) is constant; EF increases with increasing end-diastolic wall thickness. The corrected EF is determined by following the iso-strain lines to the equivalent EF in the absence of hypertrophy (e.g. 9 mm thickness). For example, an individual with a mean end-diastolic wall thickness of 20 mm and measured EF of 60% has a corrected EF (EF(c)) of 37%. The study shows that the EF is determined by absolute wall thickening and provides a nomogram for comparing EF when LVH is present. The EF(c) is a potential new measure of left ventricular systolic function. Its possible role will need validating in mortality trials.

Iron overload in polytransfused patients without heart failure is associated with subclinical alterations of systolic left ventricular function using cardiovascular magnetic resonance tagging.

BackgroundIt remains incompletely understood whether patients with transfusion related cardiac iron overload without signs of heart failure exhibit already subclinical alterations of systolic left ventricular (LV) dysfunction. Therefore we performed a comprehensive evaluation of systolic and diastolic cardiac function in such patients using tagged and phase-contrast CMR.Methods19 patients requiring regular blood transfusions for chronic anemia and 8 healthy volunteers were investigated using cine, tagged, and phase-contrast and T2* CMR. LV ejection fraction, peak filling rate, end-systolic global midventricular systolic Eulerian radial thickening and shortening strains as well as left ventricular rotation and twist, mitral E and A wave velocity, and tissue e' wave and E/e' wave velocity ratio, as well as isovolumic relaxation time and E wave deceleration time were computed and compared to cardiac T2*.ResultsPatients without significant iron overload (T2* > 20 ms, n = 9) had similar parameters of systolic and diastolic function as normal controls, whereas patients with severe iron overload (T2* < 10 ms, n = 5), had significant reduction of LV ejection fraction (54 ± 2% vs. 62 ± 6% and 65 ± 6% respectively p < 0.05), of end-systolic radial thickening (+6 ± 4% vs. +11 ± 2 and +11 ± 4% respectively p < 0.05) and of rotational twist (1.6 ± 0.2 degrees vs. 3.0 ± 1.2 and 3.5 ± 0.7 degrees respectively, p < 0.05) than patients without iron overload (T2* > 20 ms) or normal controls. Patients with moderate iron overload (T2* 10-20 ms, n = 5), had preserved ejection fraction (59 ± 6%, p = NS vs. pts. with T2* > 20 ms and controls), but showed reduced maximal LV rotational twist (1.8 ± 0.4 degrees). The magnitude of reduction of LV twist (r = 0.64, p < 0.001), of LV ejection fraction (r = 0.44, p < 0.001), of peak radial thickening (r = 0.58, p < 0.001) and of systolic (r = 0.50, p < 0.05) and diastolic twist and untwist rate (r = -0.53, p < 0.001) in patients were directly correlated to the logarithm of cardiac T2*.ConclusionMultiple transfused patients with normal ejection fraction and without heart failure have subclinical alterations of systolic and diastolic LV function in direct relation to the severity of cardiac iron overload. Among all parameters, left ventricular twist is affected earliest, and has the highest correlation to log (T2*), suggesting that this parameter might be used to follow systolic left ventricular function in patients with iron overload.

089 Effect of circumferential and longitudinal strain on radial function: implications for regional vs global left ventricular function: Abstract 089 Table 1

<h3>Introduction</h3> Hypertrophic left ventricular disease occurs in numerous conditions including hypertension, aortic stenosis, hypertrophic cardiomyopathy, Fabry disease, amyloid and heart failure with a normal ejection fraction. Many clinical studies have showed the presence of abnormal longitudinal and circumferential left ventricular regional function (strain, strain rate, peak shortening velocities etc) in patients with concentric left ventricular hypertrophy. In addition, there is significantly reduced radial strain in many of these conditions despite the apparent normal radial ‘function’ and ejection fraction. In order to improve understanding of the relationship between strain and wall thickening, this study assesses the effect of left ventricular end-diastolic wall thickness and circumferential/longitudinal strain on radial strain and wall thickening. <h3>Methods</h3> The deformation characteristics of an isolated cube of myocardium 9×9×9 mm were assessed. The myocardial tissue was assumed to be a non-compressible elastomer. Circumferential (CS) and longitudinal strain (LS) were adjusted as follows, normal (–20%), moderately reduced (−15%) and severely reduced (–10%). The effect of changing end-diastolic wall thickness (EDWT) and LS/CS on radial strain (RS ie, relative wall thickening) and absolute wall thickening were calculated. <h3>Results</h3> Increasing end-diastolic wall thickness, with constant LS and CS, increased end-systolic wall thickness and absolute wall thickening but radial strain remained constant. When LS &amp; CS were reduced, end-systolic wall thickness, RS and absolute thickening decreased. However, in the presence of an increase in end-diastolic wall thickness, absolute wall thickening remained normal despite a reduction in radial strain (see abstract 089 table 1) <h3>Conclusion</h3> LS &amp; CS determine RS. However, absolute radial thickening is determined by both end-diastolic wall thickness and RS. Since, the external left ventricular circumference reduces by only 3% the absolute radial thickening determines most of the endocardial displacement and hence determines stroke volume. It is essential to differentiate between absolute and relative radial thickening when describing radial function. An increase in end-diastolic wall thickness with normal shortening must lead to an increased absolute thickening; in order for the absolute wall thickening to remain normal, myocardial shortening must be reduced. Myocardial strain has to be reduced proportionally to the degree of concentric hypertrophy otherwise the ejection fraction and stroke volume will be inappropriately increased. This study explains the geometric findings in hypertrophic heart disease regardless of the cause. A normal ejection fraction does not equate to normal deformation or even normal systolic function. The term ‘global systolic function’ is unhelpful, misleading and should be abandoned.