Left ventricular mechanics related to the local distribution of oxygen demand throughout the wall

Additive effects of type 2 diabetes and metabolic syndrome on left ventricular torsion and linear deformation abnormalities during dobutamine stress echocardiography

Objective

The interplay between metabolic syndrome (MS) and type 2 diabetes (T2D) on regional myocardial mechanics and the potential additional effects of their combination remain poorly understood. In this context, we evaluated left ventricular (LV) torsion and linear deformation at rest and under dobutamine (DB) stress in patients with T2D, MS or both.

Methods

Thirty-nine T2D patients without MS (T2D), 37 MS patients free from T2D (MS), 44 patients with both T2D and MS (T2D-MS group) and 38 healthy patients (control group) were prospectively recruited. Speckle-tracking echocardiography (STE) was conducted at rest and low dose DB to evaluate LV myocardial longitudinal (LS) as well as circumferential (CS) strain and early diastolic strain rate (LSrd, CSrd) and twist-untwist mechanics.

Results

At rest, MS, T2D and controls presented with similar resting LS and LSrd while significant lower values were obtained in T2D-MS compared to controls. DB revealed reduced LS, LSrd, CS and CSrd in MS and T2D groups compared to controls. In T2-MS, the decline in LS and LSrd established at rest was exacerbated under DB. Stress echocardiography revealed also lower basal rotation and subsequently lower twist in MS and T2D patients compared to controls. T2D-MS showed major impairments of apical rotation and twist under DB stress, with values significantly lower compared to the 3 other groups. From stepwise multiple linear regression analysis, epicardial adipose tissue for Δ (rest to DB) LS, numbers of MS factors for Δ CS and Δ Twist emerged as major independent predictors.

Conclusion

These results demonstrate synergic and additive effects of T2D and MS on LV torsion and linear deformation abnormalities in asymptomatic patients with metabolic diseases. They also highlight the usefulness of speckle tracking echocardiography under DB stress in detecting multidirectional myocardial mechanics impairments that can remain barely detectable at rest, such as in isolated T2D or MS patients.

Transmural Distribution of Coronary Perfusion and Myocardial Work Density Due to Alterations in Ventricular Loading, Geometry and Contractility

Myocardial supply changes to accommodate the variation of myocardial demand across the heart wall to maintain normal cardiac function. A computational framework that couples the systemic circulation of a left ventricular (LV) finite element model and coronary perfusion in a closed loop is developed to investigate the transmural distribution of the myocardial demand (work density) and supply (perfusion) ratio. Calibrated and validated against measurements of LV mechanics and coronary perfusion, the model is applied to investigate changes in the transmural distribution of passive coronary perfusion, myocardial work density, and their ratio in response to changes in LV contractility, preload, afterload, wall thickness, and cavity volume. The model predicts the following: (1) Total passive coronary flow varies from a minimum value at the endocardium to a maximum value at the epicardium transmurally that is consistent with the transmural distribution of IMP; (2) Total passive coronary flow at different transmural locations is increased with an increase in either contractility, afterload, or preload of the LV, whereas is reduced with an increase in wall thickness or cavity volume; (3) Myocardial work density at different transmural locations is increased transmurally with an increase in either contractility, afterload, preload or cavity volume of the LV, but is reduced with an increase in wall thickness; (4) Myocardial work density-perfusion mismatch ratio at different transmural locations is increased with an increase in contractility, preload, wall thickness or cavity volume of the LV, and the ratio is higher at the endocardium than the epicardium. These results suggest that an increase in either contractility, preload, wall thickness, or cavity volume of the LV can increase the vulnerability of the subendocardial region to ischemia.

Thermodynamic inconsistency disproves the Suga-Sagawa theory of cardiac energetics

The theory proposed by Suga and Sagawa, encompassing the concepts of 'time-varying elastance', 'pressure-volume area' and 'isoefficiency', has been widely applied in cardiac research - albeit not without contention. In this Review, we commence with a brief history of striated muscle energetics as a prelude to re-visiting the Suga-Sagawa Theory. We conclude our discussion by including recent insights into the fundamental flaw underlying the metabolic component of the Theory.

Pathophysiology of Hypertensive Heart Disease: Beyond Left Ventricular Hypertrophy

PURPOSE OF REVIEW

Given that the life expectancy and the burden of hypertension are projected to increase over the next decade, hypertensive heart disease (HHD) may be expected to play an even more central role in the pathophysiology of cardiovascular disease (CVD). A broader understanding of the features and underlying mechanisms that constitute HHD therefore is of paramount importance.

RECENT FINDINGS

HHD is a condition that arises as a result of elevated blood pressure and constitutes a key underlying mechanism for cardiovascular morbidity and mortality. Historically, studies investigating HHD have primarily focused on left ventricular (LV) hypertrophy (LVH), but it is increasingly apparent that HHD encompasses a range of target-organ damage beyond LVH, including other cardiovascular structural and functional adaptations that may occur separately or concomitantly. HHD is characterized by micro- and macroscopic myocardial alterations, structural phenotypic adaptations, and functional changes that include cardiac fibrosis, and the remodeling of the atria and ventricles and the arterial system. In this review, we summarize the structural and functional alterations in the cardiac and vascular system that constitute HHD and underscore their underlying pathophysiology.

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.

Mechanism of Action Potential Prolongation During Metabolic Inhibition in the Whole Rabbit Heart

Myocardial ischemia is associated with significant changes in action potential (AP) duration, which has a biphasic response to metabolic inhibition. Here, we investigated the mechanism of initial AP prolongation in whole Langendorff-perfused rabbit heart. We used glass microelectrodes to record APs transmurally. Simultaneously, optical AP, calcium transient (CaT), intracellular pH, and magnesium concentration changes were recorded using fluorescent dyes. The fluorescence signals were recorded using an EMCCD camera equipped with emission filters; excitation was induced by LEDs. We demonstrated that metabolic inhibition by carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) resulted in AP shortening preceded by an initial prolongation and that there were no important differences in the response throughout the wall of the heart and in the apical/basal direction. AP prolongation was reduced by blocking the I_CaL and transient outward potassium current (I_to) with diltiazem (DTZ) and 4-aminopyridine (4-AP), respectively. FCCP, an uncoupler of oxidative phosphorylation, induced reductions in CaTs and intracellular pH and increased the intracellular Mg²⁺ concentration. In addition, resting potential depolarization was observed, clearly indicating a decrease in the inward rectifier K⁺ current (I_K1) that can retard AP repolarization. Thus, we suggest that the main currents responsible for AP prolongation during metabolic inhibition are the I_CaL, I_to, and I_K1, the activities of which are modulated mainly by changes in intracellular ATP, calcium, magnesium, and pH.

Cardiac Rotational Mechanics As a Predictor of Myocardial Recovery in Heart Failure Patients Undergoing Chronic Mechanical Circulatory Support: A Pilot Study

BACKGROUND

Impaired qualitative and quantitative left ventricular (LV) rotational mechanics predict cardiac remodeling progression and prognosis after myocardial infarction. We investigated whether cardiac rotational mechanics can predict cardiac recovery in chronic advanced cardiomyopathy patients.

METHODS AND RESULTS

Sixty-three patients with advanced and chronic dilated cardiomyopathy undergoing implantation of LV assist device (LVAD) were prospectively investigated using speckle tracking echocardiography. Acute heart failure patients were prospectively excluded. We evaluated LV rotational mechanics (apical and basal LV twist, LV torsion) and deformational mechanics (circumferential and longitudinal strain) before LVAD implantation. Cardiac recovery post-LVAD implantation was defined as (1) final resulting LV ejection fraction ≥40%, (2) relative LV ejection fraction increase ≥50%, (iii) relative LV end-systolic volume decrease ≥50% (all 3 required). Twelve patients fulfilled the criteria for cardiac recovery (Rec Group). The Rec Group had significantly less impaired pre-LVAD peak LV torsion compared with the Non-Rec Group. Notably, both groups had similarly reduced pre-LVAD LV ejection fraction. By receiver operating characteristic curve analysis, pre-LVAD peak LV torsion of 0.35 degrees/cm had a 92% sensitivity and a 73% specificity in predicting cardiac recovery. Peak LV torsion before LVAD implantation was found to be an independent predictor of cardiac recovery after LVAD implantation (odds ratio, 0.65 per 0.1 degrees/cm [0.49-0.87]; P=0.014).

CONCLUSIONS

LV rotational mechanics seem to be useful in selecting patients prone to cardiac recovery after mechanical unloading induced by LVADs. Future studies should investigate the utility of these markers in predicting durable cardiac recovery after the explantation of the cardiac assist device.

Age- and Sex-Related Influences on Left Ventricular Mechanics in Elderly Individuals Free of Prevalent Heart Failure: The ARIC Study (Atherosclerosis Risk in Communities)

BACKGROUND

Advanced age is related to left ventricular (LV) remodeling. We sought to investigate the relationships between aging, elevated hemodynamic load, cardiac mechanics, and LV remodeling in an elderly community-based population.

METHODS AND RESULTS

We studied 1105 subjects (76±5 years, 61% women) without prevalent heart failure, who attended the visit 5 of the ARIC study (Atherosclerosis Risk in Communities). LV global longitudinal strain, global circumferential strain, and torsion indices were analyzed using 3-dimensional echocardiography. Advanced age was associated with greater LV concentricity, lower myocardial diastolic relaxation, reduced global longitudinal strain (adjusted estimate, 0.39±0.19% (SE)/decade; P=0.038), borderline greater global circumferential strain (adjusted estimate, -0.59±0.36% (SE)/decade; P=0.08), and higher torsion indices (adjusted estimate for torsion, 0.33±0.04° (SE)/decade; P<0.001). In addition, greater concentricity was associated with decreased global longitudinal strain and greater torsion in multivariable models (all P<0.001). Women showed smaller LV cavity size, greater concentricity, lower myocardial relaxation velocity E', though demonstrated greater global longitudinal strain, global circumferential strain, and torsion than men (all P<0.05). Overall, subjects with hypertension and increasing age were more likely to have higher torsion, though the association between advanced age and greater torsion was more pronounced in women than in men (both interaction P<0.05).

CONCLUSIONS

In an asymptomatic, senescent community-dwelling population, we observed a distinct, sex-specific pattern of cardiac remodeling. Although we observed worse diastolic and longitudinal function with advanced age or elevated load in both sexes, a significant increase of torsion was more pronounced in women.

A combined cellular and surgical ventricular reconstruction therapeutic approach produces attenuation of remodeling in infarcted rats

BACKGROUND

Left ventricular reconstruction (LVR) has been shown to provide transient benefits to the LV structure and function of infarcted hearts; however, long-term results have been disappointing as LVR-induced benefits are typically not sustained. We hypothesized that administration of cardiosphere-derived cells (CDCs), which promote myocardial repair and regeneration, may result in long-term preservation of the beneficial effects of LVR in ischemic cardiomyopathy.

METHODS

Wistar Kyoto rats underwent myocardial infarction (MI) and two weeks later were randomized into 3 groups: in Group 1 (n=9), LVR was performed by plication of the infarcted apex and CDCs were injected in the infarct border zone (IBZ); group 2 animals (n=9) underwent LVR and received vehicle solution in the IBZ; and Group 3 animals (n=10) were injected with vehicle solution in the IBZ without undergoing LVR. Echocardiograms were performed at baseline, 4 days post-apex plication, and at 3 months post-MI.

RESULTS

At baseline, all animal groups had a comparable LVEF, LV end-diastolic volume (EDV) and LV end-systolic volume (ESV). Four days post-LV apex plication, Group 1 and Group 2 animals exhibited comparable significant improvement in EF and comparable significant reduction in LVEDV and LVESV. Three months post-MI, Group 1 animals had a decreased LVEDV, decreased LVESV, less impaired CS, increased peak systolic torsion and increased EF compared to animals in Groups 2 and 3.

CONCLUSION

In infarcted rat hearts, intramyocardial delivery of CDCs in conjunction with LVR resulted in significant and sustained amelioration of LV remodeling and improvement in LV function compared to LVR alone.

Myocardial torsional deformations in cats with hypertrophic cardiomyopathy using two-dimensional speckle-tracking echocardiography

OBJECTIVES

The objective of our study was to quantitatively measure systolic torsional deformations in cats with hypertrophic cardiomyopathy (HCM) and in controls.

ANIMALS

Twenty-six client-owned cats with HCM and 14 healthy cats. HCM cats were categorized based on their symptoms (asymptomatic and symptomatic) and with or without left ventricular outflow tract obstruction (obstructive and non-obstructive).

METHODS

The cats were examined for myocardial deformations using two-dimensional speckle-tracking echocardiography and were evaluated for peak systolic rotation and the rotation rate at each basal and apical view. Cats were also evaluated for the peak systolic torsion and torsion rate.

RESULTS

The peak systolic apical rotation and torsion were higher in asymptomatic and symptomatic cats with HCM than in control cats. Also, the peak systolic apical rotation, apical rotation rate, torsion, and torsion rate were higher in cats with obstructive HCM than in control cats.

CONCLUSIONS

Myocardial torsional deformations assessed by two-dimensional speckle-tracking echocardiography may be useful for evaluating compensatory myocardial function of HCM.

The Effects of Exercise Intensity vs. Metabolic State on the Variability and Magnitude of Left Ventricular Twist Mechanics during Exercise

Increased left ventricular (LV) twist and untwisting rate (LV twist mechanics) are essential responses of the heart to exercise. However, previously a large variability in LV twist mechanics during exercise has been observed, which complicates the interpretation of results. This study aimed to determine some of the physiological sources of variability in LV twist mechanics during exercise. Sixteen healthy males (age: 22 ± 4 years, V˙O_2peak: 45.5 ± 6.9 ml∙kg^-1∙min^-1, range of individual anaerobic threshold (IAT): 32–69% of V˙O_2peak) were assessed at rest and during exercise at: i) the same relative exercise intensity, 40%_peak, ii) at 2% above IAT, and, iii) at 40%_peak with hypoxia (40%_peak+HYP). LV volumes were not significantly different between exercise conditions (P > 0.05). However, the mean margin of error of LV twist was significantly lower (F_2,47 = 2.08, P < 0.05) during 40%peak compared with IAT (3.0 vs. 4.1 degrees). Despite the same workload and similar LV volumes, hypoxia increased LV twist and untwisting rate (P < 0.05), but the mean margin of error remained similar to that during 40%peak (3.2 degrees, P > 0.05). Overall, LV twist mechanics were linearly related to rate pressure product. During exercise, the intra-individual variability of LV twist mechanics is smaller at the same relative exercise intensity compared with IAT. However, the absolute magnitude (degrees) of LV twist mechanics appears to be associated with the prevailing rate pressure product. Exercise tests that evaluate LV twist mechanics should be standardised by relative exercise intensity and rate pressure product be taken into account when interpreting results.

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

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

Patients with Diabetes and Significant Epicardial Coronary Artery Disease Have Increased Systolic Left Ventricular Apical Rotation and Rotation Rate at Rest

OBJECTIVE

The purpose of this study was to determine whether resting myocardial deformation and rotation may be altered in diabetic patients with significant epicardial coronary artery disease (CAD) with normal left ventricular ejection fraction.

DESIGN

A prospective observational study.

SETTING

Diagnosis of epicardial CAD in patients with diabetes.

PATIENTS AND METHODS

Eighty-four patients with diabetes suspected of epicardial CAD scheduled for cardiac catheterization had a resting echocardiogram performed prior to their procedure. Echocardiographic measurements were compared between patients with and without significant epicardial CAD as determined by cardiac catheterization.

MAIN OUTCOME MEASURES

Measurement of longitudinal strain, strain rate, apical rotation, and rotation rate, using speckle tracking echocardiography.

RESULTS

Eighty-four patients were studied, 39 (46.4%) of whom had significant epicardial CAD. Global peak systolic apical rotation was significantly increased (14.9 ± 5.1 vs. 11.0 ± 4.8 degrees, P < 0.001) in patients with epicardial CAD along with faster peak systolic apical rotation rate (90.4 ± 29 vs. 68.1 ± 22.2 degrees/sec, P < 0.001). These findings were further confirmed through multivariate logistic regression analysis (global peak systolic apical rotation OR = 1.17, P = 0.004 and peak systolic apical rotation rate OR = 1.05, P < 0.001).

CONCLUSIONS

Patients with diabetes with significant epicardial CAD and normal LVEF exhibit an increase in peak systolic apical counterclockwise rotation and rotation rate detected by echocardiography, suggesting that significant epicardial CAD and its associated myocardial effects in patients with diabetes may be detected noninvasively at rest.

Differential response of LV sublayer twist during dobutamine stress echocardiography as a novel marker of contractile reserve after acute myocardial infarction: relationship with follow-up LVEF improvement

AIMS

Dobutamine stress echocardiography (DSE) is frequently performed to assess left ventricular (LV) contractile reserve in patients following myocardial infarction (STEMI). Given that resting LV sublayer twist assessment has been proposed as a marker of infarct transmurality, this study aimed to investigate whether response of LV subepicardial twist on DSE represents a novel quantitative marker of contractile reserve.

METHODS AND RESULTS

First STEMI patients treated with primary percutaneous coronary intervention with a resting wall motion abnormality in greater than or equal to two segment(s) at 3 months who underwent full protocol DSE were included. Two-dimensional speckle-tracking was used to calculate LV subepi- and subendocardial twist-defined as the net difference (in degrees) of apical and basal rotation for each sublayer-at rest and peak-dose stages. Primary end point was a ≥5% absolute LV ejection fraction (LVEF) improvement between 3 and 6 months. In total, 61 patients (mean age 61 ± 12, 87% male) were included, of whom 48% (n = 29) demonstrated follow-up LVEF improvement. Mean change in both LV subepicardial (ΔLVsubepi) twist (2.4 ± 3.0 vs. 0.00 ± 2.0°, P = 0.001) and LV subendocardial (ΔLVsubendo) twist (2.7 ± 4.5 vs. 0.25 ± 4.5°, P = 0.04) from rest to peak was significantly higher in LVEF improvers. ΔLVsubepi (odds ratio, OR 1.5, 95% confidence interval, CI 1.1-2.0, P = 0.007), but not ΔLVsubendo (OR 1.1, 95% CI 0.99-1.3, P = 0.07), twist was independently associated with follow-up LVEF improvement following adjustment for baseline LVEF and β-blockade.

CONCLUSION

In post-STEMI patients with resting regional dysfunction, the response of LV subepicardial twist on DSE is associated with follow-up LV function improvement, suggesting recruitment in subepicardial function following STEMI reflects greater extent of contractile reserve.

Regional myocardial three-dimensional principal strains during postinfarction remodeling

BACKGROUND

The purpose of this study was to quantify myocardial three-dimensional (3D) principal strains as the left ventricle (LV) remodels after myocardial infarction (MI). Serial quantification of myocardial strains is important for understanding the mechanical response of the LV to MI. Principal strains convert the 3D LV wall-based strain matrix with three normal and three shear elements, to a matrix with three nonzero normal elements, thereby eliminating the shear elements, which are difficult to physically interpret.

METHODS

The study was designed to measure principal strains of the remote, border zone, and infarct regions in a porcine model of post-MI LV remodeling. Magnetic resonance imaging was used to measure function and strain at baseline, 1 week, and 4 weeks after infarct. Principal strain was measured using 3D acquisition and the optical flow method for displacement tracking.

RESULTS

Principal strains were altered as the LV remodeled. Maximum principal strain magnitude decreased in all regions, including the noninfarcted remote, while maximum principal strain angles rotated away from the radial direction in the border zone and infarct. Minimum principal strain magnitude followed a similar pattern; however, strain angles were altered in all regions. Evolution of principal strains correlated with adverse LV remodeling.

CONCLUSIONS

Using a state-of-the-art imaging and optical flow method technique, 3D principal strains can be measured serially after MI in pigs. Results are consistent with progressive infarct stretching as well as with decreased contractile function in the border zone and remote myocardial regions.

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

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

Ventricular structure, function, and mechanics at high altitude: chronic remodeling in Sherpa vs. short-term lowlander adaptation

Short-term, high-altitude (HA) exposure raises pulmonary artery systolic pressure (PASP) and decreases left-ventricular (LV) volumes. However, relatively little is known of the long-term cardiac consequences of prolonged exposure in Sherpa, a highly adapted HA population. To investigate short-term adaptation and potential long-term cardiac remodeling, we studied ventricular structure and function in Sherpa at 5,050 m (n = 11; 31 ± 13 yr; mass 68 ± 10 kg; height 169 ± 6 cm) and lowlanders at sea level (SL) and following 10 ± 3 days at 5,050 m (n = 9; 34 ± 7 yr; mass 82 ± 10 kg; height 177 ± 6 cm) using conventional and speckle-tracking echocardiography. At HA, PASP was higher in Sherpa and lowlanders compared with lowlanders at SL (both P < 0.05). Sherpa had smaller right-ventricular (RV) and LV stroke volumes than lowlanders at SL with lower RV systolic strain (P < 0.05) but similar LV systolic mechanics. In contrast to LV systolic mechanics, LV diastolic, untwisting velocity was significantly lower in Sherpa compared with lowlanders at both SL and HA. After partial acclimatization, lowlanders demonstrated no change in the RV end-diastolic area; however, both RV strain and LV end-diastolic volume were reduced. In conclusion, short-term hypoxia induced a reduction in RV systolic function that was also evident in Sherpa following chronic exposure. We propose that this was consequent to a persistently higher PASP. In contrast to the RV, remodeling of LV volumes and normalization of systolic mechanics indicate structural and functional adaptation to HA. However, altered LV diastolic relaxation after chronic hypoxic exposure may reflect differential remodeling of systolic and diastolic LV function.

Dobutamine stress echocardiography for assessment of systolic function in dogs with experimentally induced mitral regurgitation

Background

Systolic dysfunction is associated with poor outcomes in dogs with myxomatous mitral valve disease. However, assessment of systolic variables by conventional echocardiographic methods is difficult in these dogs because of mitral regurgitation (MR).

Hypothesis

We hypothesized that assessment of systolic function by dobutamine stress may identify systolic dysfunction in dogs with MR, and that 2‐dimensional speckle‐tracking echocardiography (2D‐STE) could quantitatively evaluate myocardial function.

Animals

Anesthetized dogs with experimentally induced MR.

Methods

Dogs were examined for systolic myocardial deformations using 2D‐STE during dobutamine infusion before and 3 and 6 months after MR induction. We evaluated peak systolic rotation and rotation rate in each basal and apical view; peak systolic torsion and torsion rate were also calculated.

Results

Invasive peak positive first derivatives of left ventricular pressure (dp/dt) were significantly decreased in dogs 6 months after induction of MR compared with pre‐MR results. After 3 and 6 months of MR, dogs had diminished peak systolic torsion values and torsion rates in response to dobutamine infusion compared with pre‐MR results (3 months, P < .001 and P = .006; 6 months, P = .003 and P = .021). These results were significantly correlated with overall invasive dp/dt (r = 0.644, P < .001; r = 0.696, P < .001).

Conclusions and Clinical Importance

Decreased torsion during dobutamine infusion in dogs with MR may reflect latent systolic dysfunction. Dobutamine infusion, therefore, may be useful for the assessment of systolic function in dogs with MR.

Left ventricular torsion changes post kidney transplantation

Background

To quantify changes of left ventricular (LV) torsion in patients' pre and post kidney transplantation.

Methods

A prospective study was conducted on 48 patients who received kidney transplantation for end stage renal disease and without myocardial infarction. The rotation, twist and torsion of LV were studied pre and post kidney transplantation (6 months post transplantation) using velocity vector imaging by echocardiography. The data is expressed as mean ± standard deviation and compared by paired t-test at the p < 0.05 significance level.

Results

Six months post kidney transplantation, left ventricular ejection fraction (from 40.33 ± 11.42 to 61.00 ± 13.68%), ratio of mitral early and late diastolic filling velocity (from 1.04 ± 0.57 to 1.21 ± 0.52), rotation of basal LV (from 4.48 ± 2.66 to 5.65 ± 2.64 degree), rotation of apical LV (from 4.27 ± 3.08 to 5.50 ± 4.25 degree), LV twist (8.75 ± 4.45 to 11.14 ± 5.25 degree) and torsion (from 1.06 ± 0.54 to 1.33 ± 0.61 degree/cm) were increased significantly (p < 0.05). Interventricular septum thickness (from 11.67 ± 2.39 to 9.67 ± 0.48 mm), left ventricular mass index (from 104.00 ± 16.47 to 95.50 ± 21.44 g/m²), systolic blood pressure (from 143.50 ± 34.99 to 121.50 ± 7.09 mmHg), serum blood urea nitrogen (from 42.40 ± 7.98 to 30.43 ± 13.85 mg/dL) and creatinine (from 4.53 ± 1.96 to 2.73 ± 2.57 mg/dL) were decreased significantly (p < 0.05).

Conclusion

Kidney transplantation in end stage renal disease without myocardial infarction results in improvement in left ventricular structure, function and myocardial mechanics as detected by echocardiography and velocity vector imaging. Velocity vector imaging provided valuable information for detection and follow-up of cardiac abnormalities in patients with end stage renal disease.

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

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

MATERNAL CARDIAC TWIST PRE-PREGNANCY: POTENTIAL AS A NOVEL MARKER OF PRE-ECLAMPSIA

Healthy pregnancy is characterised by progressive physiological adaptation of the maternal cardiovascular (CV) system that facilitates optimal fetal development. The adaptations that constitute a healthy or normal progression are not always evident, and, in particular, CV adaptation to pregnancy is highly individualised. Some women develop pregnancy-related CV dysfunction such as pre-eclampsia (PE). Typically, PE is diagnosed by the development of hypertension and proteinuria after 20 weeks of pregnancy and is the leading cause of maternal and perinatal mortality and morbidity. Despite continued efforts to improve the understanding of the aetiology, pathophysiology and subsequently treatment for the disease, CV changes in PE are not well understood. PE before 34 weeks (early onset PE) is believed to differ in pathogenesis from late onset PE (>34 weeks) and can be characterised by a haemodynamic profile of increased systemic vascular resistance (SVR) and lower cardiac output (CO). Early onset PE is more often associated with uteroplacental insufficiency and significant adverse maternal and perinatal outcomes. In contrast, late onset PE (>34 weeks) involves an increased CO and lower SVR and is less likely to be associated with uteroplacental insufficiency and adverse perinatal outcomes. It is not known if PE develops secondary to the CV maladaptation in pregnancy or if a preexisting CV dysfunction predisposes some women to develop PE. Screening, diagnosis and disease management would be vastly improved if more were known about the onset of the maladaptive process associated with PE. To date, a combination of maternal factors including medical history, body mass index, age, parity and blood pressure (BP) have been used to predict the development of PE. In the first trimester, arterial stiffness is significantly increased in women who develop PE. Current hypotheses speculate that CV dysfunction is evident very early in pregnancy in PE and precedes the clinical manifestation at a later stage but whether CV dysfunction is present before pregnancy remains to be elucidated.

Left ventricular twist and circumferential strain in dogs with myxomatous mitral valve disease

BACKGROUND

During the cardiac cycle, the ventricle undergoes a twisting motion because of the oblique orientation of the left ventricular (LV) myofibers. This can be quantified by speckle-tracking echocardiography (STE). In mitral regurgitation (MR) in humans, the short axis deformation has been suggested as being pivotal to LV function. Decreased and delayed LV twist has been described in experimental MR, but has not been studied in myxomatous mitral valve disease (MMVD).

HYPOTHESES

(1) Magnitude (CSt) and rate (CSRs) of systolic circumferential deformation decrease before the onset of congestive heart failure (CHF); (2) magnitude and rate of LV twist decrease, and onset of untwist is delayed, with increasing MMVD severity.

ANIMALS

A total of 97 privately owned small- to medium-sized dogs.

METHODS

Severity of MMVD was assessed by echocardiography and presence of clinical signs of CHF. Magnitude and rate of LV twist and circumferential deformation were evaluated by STE.

RESULTS

Dogs with CHF receiving treatment had increased CSt, CSRs, early diastolic untwisting rate, and delayed onset of untwist compared to dogs with minimal MMVD and increased systolic twist compared to dogs with mild MMVD (all P < .01). CSt and time to onset of untwist increased with echocardiographic variables of MR severity (all P < .002). CSRs and several LV twist variables decreased with increasing systolic LV internal diameter (all P < .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

No STE-derived variable was decreased before onset of CHF. In dogs with CHF receiving treatment, the delayed onset of relaxation might indicate LV dysfunction and the hyperdynamic CSt and LV twist reflect compensatory mechanisms.

Subendocardial increase in reactive oxygen species production affects regional contractile function in ischemic heart failure

AIMS

Heart failure (HF) is characterized by regionalized contractile alterations resulting in loss of the transmural contractile gradient across the left ventricular free wall. We tested whether a regional alteration in mitochondrial oxidative metabolism during HF could affect myofilament function through protein kinase A (PKA) signaling.

RESULTS

Twelve weeks after permanent left coronary artery ligation that induced myocardial infarction (MI), subendocardial (Endo) cardiomyocytes had decreased activity of complex I and IV of the mitochondrial electron transport chain and produced twice more superoxide anions than sham Endo and subepicardial cells. This effect was associated with a reduced antioxidant activity of superoxide dismutase and Catalase only in MI Endo cells. The myofilament contractile properties (Ca(2+) sensitivity and maximal tension), evaluated in skinned cardiomyocytes, were also reduced only in MI Endo myocytes. Conversely, in MI rats treated with the antioxidant N-acetylcysteine (NAC) for 4 weeks, the generation of superoxide anions in Endo cardiomyocytes was normalized and the contractile properties of skinned cardiomyocytes restored. This effect was accompanied by improved in vivo contractility. The beneficial effects of NAC were mediated, at least, in part, through reduction of the PKA activity, which was higher in MI myofilaments, particularly, the PKA-mediated hyperphosphorylation of cardiac Troponin I.

INNOVATION

The Transmural gradient in the mitochondrial content/activity is lost during HF and mediates reactive oxygen species-dependent contractile dysfunction.

CONCLUSIONS

Regionalized alterations in redox signaling affect the contractile machinery of sub-Endo myocytes through a PKA-dependent pathway that contributes to the loss of the transmural contractile gradient and impairs global contractility.

Noninvasive clinical assessment of systolic torsional motions by two-dimensional speckle-tracking echocardiography in dogs with myxomatous mitral valve disease

BACKGROUND

Left ventricular torsional motion plays an important role for effective pump function. However, noninvasive clinical assessment of torsional deformations by two-dimensional speckle-tracking echocardiography (2D-STE) in dogs with myxomatous mitral valve disease (MMVD) has not been reported.

HYPOTHESIS

Left ventricular torsion is determined by the native orientation of the helical myocardial fibers, such that it might provide better assessment of myocardial function than conventional methods.

ANIMALS

Sixty-seven client-owned dogs with MMVD were classified into 3 classes based on the International Small Animal Cardiac Health Council classification and 16 weight- and age-matched healthy dogs.

METHODS

Dogs were examined for myocardial deformations by 2D-STE and were evaluated for peak systolic rotation and rotation rate at each basal and apical view. Dogs also were evaluated for peak systolic torsion and torsion rate.

RESULTS

Peak systolic torsion was higher in class II than in class I (P < .001) dogs. Peak systolic torsion was lower in class III than in class II (P = .001) dogs and controls (P = .003).

CONCLUSIONS AND CLINICAL IMPORTANCE

Torsional deformations assessed by 2D-STE differed among clinical classes of MMVD. Myocardial torsional deformations by 2D-STE may provide more detailed assessment of contractile function in dogs with MMVD.

Age, sex, and hypertension-related remodeling influences left ventricular torsion assessed by tagged cardiac magnetic resonance in asymptomatic individuals: the multi-ethnic study of atherosclerosis

BACKGROUND

The aim of the present study was to evaluate how torsion is influenced by left ventricular (LV) remodeling associated with age, sex, and hypertension in a large community-based population.

METHODS AND RESULTS

Myocardial shortening and torsion were assessed by tagged cardiac magnetic resonance in 1478 participants without clinically apparent cardiovascular disease in the Multi-Ethnic Study of Atherosclerosis (MESA). Torsion was defined as the difference between apical and basal rotation divided by slice distance. In multivariable linear regression models, older age was associated with lower stroke volume (-3.6 mL per decade; P<0.001) and higher LV mass-to-volume ratio (0.03 g/mL per decade; P<0.001), along with lower circumferential shortening (-0.17% per decade; P<0.05). Torsion, however, was greater at older ages (0.14° per decade; P<0.001) and in women (0.37°/cm versus men; P<0.001). Hypertensive participants had higher LV mass and LV mass-to-volume ratio (15.5 g and 0.07 g/mL, respectively; P<0.001 for both). Circumferential shortening was lower in hypertensive (-0.42%; P<0.01), whereas torsion was higher after adjustment for age and sex (0.17°/cm; P<0.05).

CONCLUSIONS

Older age is associated with lower LV volumes and greater relative wall thickness and is accompanied by lower circumferential myocardial shortening, whereas torsion is greater with older age. Hypertensive individuals have greater LV volumes and relative wall thickness and lower circumferential shortening. Torsion, however, is greater in hypertension independently of age and sex. Torsion may therefore represent a compensatory mechanism to maintain an adequate stroke volume and cardiac output in the face of the progressively reduced LV volumes and myocardial shortening associated with hypertension and aging.

Relation of torsion and myocardial strains to LV ejection fraction in hypertension

OBJECTIVES

The goal of this study was to define the mechanism of preserved ejection fraction (EF) despite depressed myocardial strains in hypertension (HTN).

BACKGROUND

Concentric left ventricular (LV) remodeling in HTN may have normal or supranormal EF despite depressed myocardial strains. The reason for such discordance is not clear. The aim of this study was to comprehensively evaluate the LV mechanics in a well-defined HTN population to define underlying reasons for such a paradox.

METHODS

Sixty-seven patients with resistant HTN and 45 healthy control subjects were studied by cardiac magnetic resonance imaging and tissue tagging with 3-dimensional analysis. Amplitude and directional vector of longitudinal (Ell), circumferential (Ecc), and principal strain for maximal shortening (E3) were computed at basal, mid, and distal LV levels, respectively. LV torsion, defined as the rotation angle of apex relative to base, and LV twist, which accounts for the effects of differential LV remodeling on torsion for comparison among the 2 groups, were also calculated.

RESULTS

LV mass index and LV mass/LV end-diastolic volume ratio were significantly higher in the HTN group compared with controls, consistent with concentric LV remodeling. Ell and Ecc were significantly decreased in amplitude with altered directional vector in HTN compared with controls. However, the amplitude of E3 was similar in the 2 groups. Torsion and twist were significantly higher in HTN, which was mainly due to increase in apical rotation. The HTN group demonstrated significantly increased LV wall thickening compared with controls that resulted in greater LVEF in the HTN group compared with controls (70% vs. 65%, p < 0.001, respectively).

CONCLUSIONS

In compensated LV remodeling secondary to HTN, there is increased LV wall thickening with preserved E3 and increased torsion compared with normal controls. This, therefore, contributes to supranormal LVEF in HTN despite depressed longitudinal and circumferential strains.

Left ventricular mechanics in humans with high aerobic fitness: adaptation independent of structural remodelling, arterial haemodynamics and heart rate

Individuals with high aerobic fitness have lower systolic left ventricular strain, rotation and twist (‘left ventricular (LV) mechanics’) at rest, suggesting a beneficial reduction in LV myofibre stress and more efficient systolic function. However, the mechanisms responsible for this functional adaptation are not known and the influence of aerobic fitness on LV mechanics during dynamic exercise has never been studied. We assessed LV mechanics, LV wall thickness and dimensions, central augmentation index (AIx), aortic pulse wave velocity (aPWV), blood pressure and heart rate in 28 males (age: 21±2 years SD) with a consistent physical activity level (no change>6 months). Individuals were examined at rest and during exercise (40% peak exercise capacity) and separated post hoc into a moderate and high aerobic fitness group (˙V(O2peak): 49 ± 5 and 63 ± 7ml kg−1 min−1, respectively, P <0.0001). At rest and during exercise, there were no significant differences in gross LVstructure, AIx, blood pressure or heart rate (P >0.05).However, for the same AIx, the high ˙V(O2peak) group had significantly lower LV apical rotation (P =0.002) and LV twist (P =0.003) while basal rotation and strain indices did not differ between groups (P >0.05).We conclude that young males with high aerobic fitness have lower LVapical rotation at rest and during submaximal exercise that can occur without changes in gross LV structure, arterial haemodynamics or heart rate. The findings suggest a previously unknown type of physiological adaptation of the left ventricle that may have important implications for exercise training in older individuals and patient populations in which exercise training has previously failed to show clear benefits for LV function.

Abnormal left ventricular torsion and cardiac autonomic dysfunction in subjects with type 1 diabetes mellitus

Left ventricular torsion is increased and cardiac energetics are reduced in uncomplicated type 1 diabetes mellitus (T1DM). Our aim was to determine the relationships of these abnormalities to cardiovascular autonomic neuropathy (CAN) in subjects with T1DM. A cross-sectional study was conducted in 20 subjects with T1DM free of known coronary heart disease attending an outpatient clinic. Cardiovascular autonomic neuropathy was assessed using heart rate variability studies and the continuous wavelet transform method. Left ventricular function was determined by speckle tracking echocardiography. Magnetic resonance spectroscopy and stress magnetic resonance imaging were used to measure cardiac energetics and myocardial perfusion reserve index, respectively. Twenty subjects (age, 35 ± 8 years; diabetes duration, 16 ± 9 years; hemoglobin A(1c), 8.0% ± 1.1%) were recruited. Forty percent of the subjects exhibited definite or borderline CAN. Log peak radial strain was significantly increased in subjects with CAN compared with those without (1.56 ± 0.06 vs 1.43 ± 0.14, respectively; P = .011). Data were adjusted for log duration of diabetes, and log left ventricular torsion correlated (r = 0.593, P = .01) with log low-frequency to high-frequency ratio during the Valsalva maneuver. Log isovolumic relaxation time correlated significantly with log Valsalva ratio and log proportion of differences in consecutive RR intervals of normal beats greater than 50 milliseconds during deep breathing. However, CAN did not correlate with cardiac energetics or myocardial perfusion reserve index. Spectral analysis of low-frequency to high-frequency ratio power during the Valsalva maneuver is associated with altered left ventricular torsion in subjects with T1DM. Parasympathetic dysfunction is closely associated with diastolic deficits. Cardiovascular autonomic neuropathy is not however the principal cause of impaired cardiac energetics. The role of CAN in the development of cardiomyopathy warrants further evaluation.

Evaluation of left ventricular twist in acute myocardial infarction patients using speckle tracking imaging

The aim of this study is to evaluate the differences of left ventricular (LV) twist and untwisting rate in patients with acute myocardial infarction (AMI) as compared with healthy subjects by means of Speckle Tracking Imaging (STI). 45 AMI patients (AMI group) and 48 healthy subjects (NOR group) were studied. Two-dimensional STI was performed in all patients. Peak apical rotation, peak basal rotation, peak LV twist, peak basal untwisting rate, peak apical untwisting rate, peak LV untwisting rate, time to peak LV twist, and untwisting rate were measured. In comparison with the NOR group, peak LV rotational parameters were found to be decreased in the AMI group (P < 0.01). A strong correlation was found between the peak LV twist and LV ejection fraction in the overall study population (P < 0.001). The LV twist is strongly related to LV systolic function, and the impairment of LV function observed in patients with AMI is associated with a decrease of LV twist and untwist rate. The STI appears to accurately evaluate LV function.

Altered in vivo left ventricular torsion and principal strains in hypothyroid rats

The twisting and untwisting motions of the left ventricle (LV) lead to efficient ejection of blood during systole and filling of the ventricle during diastole. Global LV mechanical performance is dependent on the contractile properties of cardiac myocytes; however, it is not known how changes in contractile protein expression affect the pattern and timing of LV rotation. At the myofilament level, contractile performance is largely dependent on the isoforms of myosin heavy chain (MHC) that are expressed. Therefore, in this study, we used MRI to examine the in vivo mechanical consequences of altered MHC isoform expression by comparing the contractile properties of hypothyroid rats, which expressed only the slow β-MHC isoform, and euthyroid rats, which predominantly expressed the fast α-MHC isoform. Unloaded shortening velocity (V(o)) and apparent rate constants of force development (k(tr)) were measured in the skinned ventricular myocardium isolated from euthyroid and hypothyroid hearts. Increased expression of β-MHC reduced LV torsion and fiber strain and delayed the development of peak torsion and strain during systole. Depressed in vivo mechanical performance in hypothyroid rats was related to slowed cross-bridge performance, as indicated by significantly slower V(o) and k(tr), compared with euthyroid rats. Dobutamine infusion in hypothyroid hearts produced smaller increases in torsion and strain and aberrant transmural torsion patterns, suggesting that the myocardial response to β-adrenergic stress is compromised. Thus, increased expression of β-MHC alters the pattern and decreases the magnitude of LV rotation, contributing to reduced mechanical performance during systole, especially in conditions of increased workload.

Left ventricular rotational mechanics in acute myocardial infarction and in chronic (ischemic and nonischemic) heart failure patients

Left ventricular (LV) twist and untwisting rate are emerging as global and thorough parameters for assessment of LV function. This study explored differences of LV twist and untwisting rate in patients with acute myocardial infarction (AMI) and patients with ischemic and nonischemic chronic heart failure (HF). Fifty patients with AMI, 49 with ischemic HF, and 38 with nonischemic HF were studied. As a control group, 28 subjects without evidence of structural heart disease were included. Speckle-tracking analysis was applied to LV short-axis images at basal and apical levels. LV twist was defined as the net difference of apical and basal rotations at isochronal time points. The first time derivative of LV untwist was defined as the LV untwisting rate. Compared with control subjects, peak LV twist was decreased in patients with AMI and extremely decreased in those with HF (p <0.001, analysis of variance). A strong correlation (r = 0.87, p <0.001) was found between peak LV twist and LV ejection fraction in the overall study population. LV untwisting rate was progressively decreased in patients with AMI and HF compared with control subjects (p <0.001, analysis of variance). A moderate correlation (r = 0.56, p <0.001) was noted between peak LV untwisting rate and grade of diastolic dysfunction in the overall study population. In conclusion, LV twist and untwisting rate are strongly related to LV systolic and diastolic functions, respectively. Impairment of LV function observed in patients with AMI and HF is associated with a decrease of LV twist and untwisting rate.

Hypertension and heart failure: a dysfunction of systole, diastole or both?

The pathological myocardial hypertrophy associated with hypertension contains the seed for further maladaptive development. Increased myocardial oxygen consumption, impaired epicardial coronary perfusion, ventricular fibrosis and remodelling, abnormalities in long-axis function and torsion, cause, to a varying degree, a mixture of systolic and diastolic abnormalities. In addition, chronotropic incompetence and peripheral factors such as lack of vasodilator reserve and reduced arterial compliance further affect cardiac output particularly on exercise. Many of these factors are common to hypertensive heart failure with a normal ejection fraction as well as systolic heart failure. There is increasing evidence that these apparently separate phenotypes are part of a spectrum of heart failure differing only in the degree of ventricular remodelling and volume changes. Furthermore, dichotomizing heart failure into systolic and diastolic clinical entities has led to a paucity of clinical trials of therapies for heart failure with a normal ejection fraction. Therapies aimed at reversing myocardial fibrosis, and targets outside the heart such as enhancing vasodilator reserve and improving chronotropic incompetence deserve further study and may improve the exercise capacity of hypertensive heart failure patients. Hypertension heart disease with heart failure is simply not a dysfunction of systole and diastole. Other peripheral factors including heart rate and vasodilator response with exercise may deserve equal attention in an attempt to develop more effective treatments for this disorder.

Age dependency in the timing of mitral annular motion in relation to ventricular filling in healthy subjects: Umea General Population Heart Study

AIMS

Peak left ventricular (LV) relaxation normally precedes peak filling (E), which supports the hypothesis that LV suction contributes to early-diastolic filling. The significance of similar temporal discordance in late diastole has previously not been studied. We describe the time relationships between mitral annular motion and LV filling in early and late diastole and examine the effect of normal ageing on these time intervals.

METHODS AND RESULTS

A total of 128 healthy subjects aged 25-88 years were studied. Transmitral and pulmonary venous flow reversals (Ar) were recorded by Doppler echocardiography. Mitral annular diastolic displacement-early (E(m)) and late (A(m))-were recorded by Doppler tissue imaging. With reference to electrocardiographic R and P-waves, the following measurements were made: R to peak E-wave (R-E) and E(m) (R-E(m)); onset P to peak A-wave (P-pA), A(m) (P-pA(m)), and Ar (P-pAr). The differences between [(R-E) and (R-E(m))] for early-diastolic temporal discordance (EDTD) and [(P-A) and (P-A(m))] for late-diastolic temporal discordance (LDTD) were calculated. Isovolumic relaxation time (IVRT) was also measured. Early-diastolic temporal discordance was approximately 26 ms in all age groups. Late-diastolic temporal discordance, however, was inversely related to age (r = -0.35, P < 0.001) and IVRT (r = -0.34, P < 0.001) and therefore decreased in the elderly vs. young (13 +/- 10 vs. 23 +/- 10 ms; P < 0.001). In multivariate analysis, age failed to predict LDTD in the presence of IVRT. A, A(m), and Ar were simultaneous at onset, and peak A(m) coincided with peak Ar in all age groups (r = 0.97, P < 0.001). No significant differences were noted in the RR intervals.

CONCLUSIONS

Sequential prolongation of IVRT with ageing reduces LDTD, thus converging the peaks of A(m), A, and Ar (atrial mechanical alignment)-a potential novel method to identify subjects at increased dependency on atrial contraction for late-diastolic filling.

Contribution of the Pericardium to Left Ventricular Torsion and Regional Myocardial Function in Patients with Total Absence of the Left Pericardium

OBJECTIVE

The relationship between left ventricular (LV) torsional deformation and myocardial function has recently been recognized. However, little is known about whether the pericardium affects this relationship. Our aim was to identify the contribution of the pericardium to LV torsion and regional myocardial function in the clinical setting.

METHODS

We examined LV torsion in basal and apical LV short-axis views, and regional LV myocardial function, such as longitudinal strain in apical 4-chamber view, and circumferential and radial strains in parasternal LV short-axis views using 2-dimensional speckle-tracking imaging method in 5 patients with congenital total absence of the left pericardium and systolic paradoxical ventricular septal motion on M-mode echocardiogram and in 10 control subjects. Diagnosis of the pericardial defect was based on chest radiograph, computed tomography, jugular phlebogram, and M-mode and 2-dimensional echocardiogram. LV torsion was defined as the net difference in LV rotation in the basal and apical planes.

RESULTS

There was no significant difference in LV ejection fraction determined by 2-dimensional echocardiography between the pericardial defect and control groups. LV torsion was markedly decreased in the pericardial defect group compared with the control group. There were no significant differences in longitudinal, radial, and circumferential systolic strains and systolic and early diastolic strain rates in the LV walls and in longitudinal systolic strains and systolic and early diastolic strain rates in the left atrial walls between the two groups.

CONCLUSIONS

Pericardial defects cause a lack of LV torsion while maintaining LV regional myocardial function in patients with systolic paradoxical ventricular septal motion. Therefore, pericardium plays an important role in LV torsion.

Study of myocardial fiber pathway using magnetic resonance diffusion tensor imaging

The purpose of this study was to investigate myocardial fiber pathway distribution in order to provide supplemental information on myocardial fiber architecture and cardiac mechanics. Diffusion tensor imaging (DTI) with medium diffusion resolution (15 directions) was performed on normal canine heart samples (N=6) fixed in formalin. With the use of diffusion tensor fiber tracking, left ventricle (LV) myocardial fiber pathways and helix angles were computed pixel by pixel at short-axis slices from base to apex. Distribution of DTI-tracked fiber pathway length and number was analyzed quantitatively as a function of fiber helix angle in step of 9 degrees . The long fiber pathways were found to have small helix angles. They are mostly distributed in the middle myocardium and run circumferentially. Fiber pathways tracked at the middle and upper LV are generally longer than those near the apex. Majority of fiber pathways have small helix angles between -20 degrees and 20 degrees , dominating the fiber architecture in myocardium. Likely, such myocardial fiber pathway measurement by DTI may reflect the spatial connectiveness or connectivity of elastic myofiber bundles along their preferential pathway of electromechanical activation. The dominance of the long and circumferentially running fiber pathways found in the study may explain the circumferential predominance in left ventricular contraction.

Contraction Pattern of the Systemic Right Ventricle

OBJECTIVES

The aim of the present study was to characterize the contraction pattern of the systemic right ventricle (RV).

BACKGROUND

Reduced longitudinal function of the systemic RV compared with the normal RV has been interpreted as ventricular dysfunction. However, longitudinal shortening represents only one aspect of myocardial deformation, and changes in contraction in other dimensions have not previously been described.

METHODS

Fourteen Senning-operated patients age 18.4 +/- 0.9 years (mean +/- SD) with transposition of the great arteries were studied. We compared the contraction pattern of the systemic RV with findings in the RV and left ventricle (LV) of normal subjects (n = 14) using tissue Doppler imaging and magnetic resonance imaging.

RESULTS

In the systemic RV free wall, circumferential strain exceeded longitudinal strain (-23.3 +/- 3.4% vs. -15.0 +/- 3.0%, p < 0.001) as was also the case in the normal LV (-25.7 +/- 3.1% vs. -16.5 +/- 1.7%, p < 0.001), opposite from the findings in the normal RV (-15.8 +/- 1.3% vs. -30.7 +/- 3.3%, p < 0.001). Strain in the interventricular septum did not differ from normal. Ventricular torsion was essentially absent in the systemic RV (0.3 +/- 1.8 degrees ), in contrast to a torsion of 16.7 +/- 4.8 degrees in the normal LV (p < 0.001).

CONCLUSIONS

In the systemic RV as in the normal LV, there was predominant circumferential over longitudinal free wall shortening, opposite from findings in the normal RV. This may represent an adaptive response to the systemic load. Noticeably, however, the systemic RV did not display torsion as found in the normal LV.

From Organ to Molecules: Steps and Consequences

The classic cardiac research programs revolved around measurable properties such as pressures, work done, vascular blood flow, electrical propagation, and other such parameters that defined the global heart functions in health and decease. Consistently, the first Henry Goldberg Workshop, held in Haifa in 1984, focused on the interactions between cardiac mechanics, electrical activation, perfusion, and metabolism of the whole heart. Questions focused on the macroscale cardiac function and performance. These studies involved engineering science, simulation, and modeling tools that were essential for the understanding of the complex interactions within the cardiac system. Three-dimensional imaging, ventricular structure, fiber mechanics, circulation and cardiovascular flow, electrical propagation, and blood pumping were all major foci of research at that time. However, it was soon obvious that in order to understand organ level characteristics, one must explore the complex cellular and intracellular control mechanisms; these became the foci of our subsequent workshops. Better understanding of organ level performance required integrated studies of organ and tissue structure and function with genetic, molecular, and cellular characteristics, including cellular communication and ionic and molecular signaling. Analysis of the cardiac system thus depends on continuous probing of the heart system with modern measurement techniques and on integrating data and acquired knowledge with analytical models, constantly evolving to match reality.