Dynamics of left ventricular apex rotation during angioplasty: a sensitive index of ischemic dysfunction

Speckle Tracking Echocardiography: Early Predictor of Diagnosis and Prognosis in Coronary Artery Disease

Echocardiography represents a first level technique for the evaluation of coronary artery disease (CAD) which supports clinicians in the diagnostic and prognostic workup of these syndromes. However, visual estimation of wall motion abnormalities sometimes fails in detecting less clear or transient myocardial ischemia and in providing accurate differential diagnosis. Speckle tracking echocardiography (STE) is a widely available noninvasive tool that could easily and quickly provide additive information over basic echocardiography, since it is able to identify subtle myocardial damage and to localize ischemic territories in accordance to the coronary lesions, obtaining a clear visualization with a "polar map" useful for differential diagnosis and management. Therefore, it has increasingly been applied in acute and chronic coronary syndromes using rest and stress echocardiography, showing good results in terms of prediction of CAD, clinical outcome, left ventricular remodeling, presence, and quantification of new/residual ischemia. The aim of this review is to illustrate the current available evidence on STE usefulness for the assessment and follow-up of CAD, discussing the main findings on bidimensional and tridimensional strain parameters and their potential application in clinical practice.

Diabetic Cardiomiopathy Progression is Triggered by miR122-5p and Involves Extracellular Matrix: A 5-Year Prospective Study

OBJECTIVES

The purpose of this study was to follow the long-term progression of diabetic cardiomyopathy by combining cardiac magnetic resonance (CMR) and molecular analysis.

BACKGROUND

The evolution of diabetic cardiomyopathy to heart failure affects patients'morbidity and mortality. CMR is the gold standard to assess cardiac remodeling, but there is a lack of markers linked to the mechanism of diabetic cardiomyopathy progression.

METHODS

Five-year longitudinal study on patients with type 2 diabetes mellitus (T2DM) enrolled in the CECSID (Cardiovascular Effects of Chronic Sildenafil in Men With Type 2 Diabetes) trial compared with nondiabetic age-matched controls. CMR with tagging together with metabolic and molecular assessments were performed at baseline and 5-year follow-up.

RESULTS

A total of 79 men (age 64 ± 8 years) enrolled, comprising 59 men with T2DM compared with 20 nondiabetic age-matched controls. Longitudinal CMR with tagging showed an increase in ventricular mass (ΔLVMi = 13.47 ± 29.66 g/m²; p = 0.014) and a borderline increase in end-diastolic volume (ΔEDVi = 5.16 ± 14.71 ml/m²; p = 0.056) in men with T2DM. Cardiac strain worsened (Δσ = 1.52 ± 3.85%; p = 0.033) whereas torsion was unchanged (Δθ = 0.24 ± 4.04°; p = 0.737), revealing a loss of the adaptive equilibrium between strain and torsion. Contraction dynamics showed a decrease in the systolic time-to-peak (ΔTtP = -35.18 ± 28.81 ms; p < 0.001) and diastolic early recoil-rate (ΔRR = -20.01 ± 19.07 s^-1; p < 0.001). The ejection fraction and metabolic parameters were unchanged. Circulating miR microarray revealed an up-regulation of miR122-5p. Network analysis predicted the matrix metalloproteinases (MMPs) MMP-16 and MMP-2 and their regulator (tissue inhibitors of metalloproteinases) as targets. In db/db mice we demonstrated that miR122-5p expression is associated with diabetic cardiomyopathy, that in the diabetic heart is overexpressed, and that, in vitro, it regulates MMP-2. Finally, we demonstrated that miR122-5p overexpression affects the extracellular matrix through MMP-2 modulation.

CONCLUSIONS

Within 5 years of diabetic cardiomyopathy onset, increasing cardiac hypertrophy is associated with progressive impairment in strain, depletion of the compensatory role of torsion, and changes in viscoelastic contraction dynamics. These changes are independent of glycemic control and paralleled by the up-regulation of specific microRNAs targeting the extracellular matrix. (Cardiovascular Effects of Chronic Sildenafil in Men With Type 2 Diabetes [CECSID]; NCT00692237).

Myocardial Rotation and Torsion in Child Growth

Background

The speckle tracking echocardiography can benefit to assess the regional myocardial deformations. Although, previous reports suggested no significant change in left ventricular (LV) torsion with aging, there are certain differences in LV rotation at the base and apex. The purpose of this study was to evaluate the change and relationship of LV rotation for torsion with aging in children.

Methods

Forty healthy children were recruited and divided into two groups of twenty based on whether the children were preschool-age (2–6 years of age) or school-age (7–12 years of age). After obtaining conventional echocardiographic data, apical and basal short axis rotation were assessed with speckle tracking echocardiography. LV rotation in the basal and apical short axis planes was determined using six myocardial segments along the central axis.

Results

Apical and basal LV rotation did not show the statistical difference with increased age between preschool- and school-age children. Apical radial strain showed significant higher values in preschool-age children, especially at the anterior (52.8 ± 17.4% vs. 34.7 ± 23.2%, p < 0.02), lateral (55.8 ± 20.4% vs. 36.1 ± 22.7%, p < 0.02), and posterior segments (57.1 ± 17.6% vs. 38.5 ± 21.7%, p < 0.01). The torsion values did not demonstrate the statistical difference between two groups.

Conclusion

This study revealed the tendency of higher rotation values in preschool-age children than in school-age children. The lesser values of rotation and torsion with increased age during childhood warrant further investigation.

Left ventricular torsion and circumferential strain responses to exercise in patients with ischemic coronary artery disease

LV torsion during exercise in patients with coronary artery disease (CAD) is not well known. Circumferential strain (CS) and left ventricular (LV) torsion (Tor) have not been evaluated during ischemia in these patients. We aimed to assess the effect of ischemia during exercise echocardiography (ExE) on CS and Tor. We studied a group of 73 patients with true positive ExE results (Ischemic group: ischemia plus an abnormal coronary angiogram) and a matched control group of 66 patients with negative ExE and either normal coronary angiography or low post-test probability of CAD. Basal rotation (Rot) and apical rotation and basal and apical CS were studied by speckle tracking at rest and exercise. Apical CS and apical and basal Rot values were similar between groups at rest, except basal CS which was already worse in the ischemic group. At exercise, all rotational and CS parameters were impaired in the ischemic in comparison with the control group (basal CS: -18 ± 5 vs. -25 ± 7 %, p < 0.001; apical CS: -31 ± 11 vs. - 43 ± 9 %, p < 0.001; time to basal CS: 52 ± 6 vs. 48 ± 7 %, p = 0.001; time to apical CS: 55 ± 7 vs. 49 ± 6 %, p < 0.001; basal rotation: -0.7 ± 6.5° vs. -6.2 ± 8.5°, p < 0.001; LV twist 13.0 ± 10.4° vs.19.7 ± 11.5°, p < 0.001; LV-Tor 1.9 ± 1.6°/cm vs. 2.8 ± 1.7˚/cm, p = 0.001) with the exception of apical rotation which was similar (12.3 ± 7.4° vs. 13.4 ± 7.7°, p = NS). Basal and apical CS and basal rotation impair during exercise-induced ischemia. LV-Tor decreases with ischemia due to worsening of basal rotation, whereas apical rotation does not impair, suggesting the existence of an apical compensatory mechanism.

Relationship between left ventricular mechanics and low free triiodothyronine levels after myocardial infarction: a prospective study

Low free triiodothyronine (fT3) levels following acute myocardial infarction (AMI) are associated with greater impairment in cardiac mechanics compared with patients with AMI who have normal values of thyroid hormones. The objectives are to investigate left ventricular (LV) function and mechanics during a 6-month follow-up after myocardial infarction and to evaluate their prognostic implication using two-dimensional (2D) echocardiography and 2D speckle-tracking echocardiography in patients with low fT3 levels. The study design is prospective cohort study. One hundred forty patients with first-onset AMI were grouped according to serum fT3 levels: low fT3 group (fT3 <3.2 pmol/L; n = 44) and control group (fT3 >3.2 pmol/L; n = 96). Low levels of fT3 were associated with greater LV diameters and LV end-diastolic volume, and decreased systolic LV function. Systolic apical and basal rotation, peak systolic global longitudinal strain and strain rate, and LV twist and torsion were significantly decreased in the low fT3 group. The prognostic implication for predicting low fT3 levels was evaluated using ROC analysis. LV end-diastolic diameter index is the most sensitive (94.12 %), but has low specificity (37.93 %; area = 0.659, p = 0.01). By contrast, LV end-systolic volume is the most specific (94.03 %), but has low sensitivity (26.32 %; area = 0.594, p = 0.04). Low fT3 levels are significantly associated with worse LV mechanics. Low fT3 levels are important for prediction of LV structure, function, rotation, and deformation parameters during the late post-myocardial infarction period.

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.

The cardiac torsion as a sensitive index of heart pathology: A model study

The torsional behaviour of the heart (i.e. the mutual rotation of the cardiac base and apex) was proved to be sensitive to alterations of some cardiovascular parameters, i.e. preload, afterload and contractility. Moreover, pathologies which affect the fibers architecture and cardiac geometry were proved to alter the cardiac torsion pattern. For these reasons, cardiac torsion represents a sensitive index of ventricular performance. The aim of this work is to provide further insight into physiological and pathological alterations of the cardiac torsion by means of computational analyses, combining a structural model of the two ventricles with simple lumped parameter models of both the systemic and the pulmonary circulations. Starting from diagnostic images, a 3D anatomy based geometry of the two ventricles was reconstructed. The myocytes orientation in the ventricles was assigned according to literature data and the myocardium was modelled as an anisotropic hyperelastic material. Both the active and the passive phases of the cardiac cycle were modelled, and different clinical conditions were simulated. The results in terms of alterations of the cardiac torsion in the presence of pathologies are in agreement with experimental literature data. The use of a computational approach allowed the investigation of the stresses and strains in the ventricular wall as well as of the global hemodynamic parameters in the presence of the considered pathologies. Furthermore, the model outcomes highlight how for specific pathological conditions, an altered torsional pattern of the ventricles can be present, encouraging the use of the ventricular torsion in the clinical practice.

Two-dimensional speckle tracking for the assessment of coronary artery disease during dobutamine stress echo: clinical tool or merely research method

BACKGROUND

Two-dimensional speckle tracking provides valuable information for regional wall motion abnormalities. The purpose of this study was to determine the diagnostic value of left ventricular longitudinal strain and torsion to diagnose coronary artery disease during dobutamine stress echocardiography.

METHODS

We studied 100 patients (mean age 60.8 ± 10.7 years, 72 male) with known or suspected coronary artery disease, excluding those with prior history of transmural infraction. All of them underwent dobutamine stress echo and coronary angiography within one month. Wall-motion score index, left ventricular global longitudinal strain and torsion were measured at rest and peak stress. Additionally, the respective differences between rest and stress were also calculated. Optimal cut-offs were derived from receiver operating characteristic curves for strain and torsion values.

RESULTS

Mean left ventricular ejection fraction was 55 ± 5.4 %. Coronary angiography revealed significant lesions in 67 patients. Values regarding sensitivity, and specificity for wall motion score index difference were 78 % and 88 % respectively (area under curve 0.84). Global longitudinal strain difference (median 0.5 %) illustrated 81 % sensitivity and 72 % specificity for disease detection (area under curve 0.80, cut-off value ≤0 %). The respective values for torsion difference (median 4.7°) were 81 % and 82 % (area under curve 0.76, cut-off value ≤6.5°). Combination of wall motion score index difference and torsion difference for disease detection showed 91 % sensitivity and 79 % specificity (area under curve 0.85).

CONCLUSIONS

The implementation of speckle tracking during dobutamine stress echo could serve as an adjunct method for coronary artery disease assessment, providing quantitative diagnostic information.

Left ventricular torsion during exercise in patients with and without ischemic response to exercise echocardiography

INTRODUCTION AND OBJECTIVES

Left ventricular torsion decreases during transmural myocardial ischemia, but the effect of exercise on left ventricular torsion has not been widely studied. We hypothesized that exercise-induced ischemia may impair left ventricular torsion. Therefore, our aim was to study the effects of exercise on left ventricular torsion in patients with an ischemic response to exercise echocardiography and in patients with a normal response.

METHODS

A retrospective analysis was performed in 172 patients with ejection fraction ≥ 50% who were referred for exercise-echocardiography and studied by speckle imaging at rest, peak and postexercise. Torsion was defined as apical rotation - basal rotation (in degrees) / left ventricular length (in centimeters). A total of 114 patients had a normal exercise echocardiography and 58 patients had an ischemic response to exercise echocardiography.

RESULTS

Patients with ischemic response to the test exhibited less basal rotation at peak exercise (+0.30° [2.39°] vs -0.65° [2.61°] in the normal group; P = .03), whereas peak apical rotation was similar (ischemic response to the test, 7.80° [3.51°]; normal response, 7.27° [3.28°]; P =.36). Torsion at peak exercise was also similar (1.07° [0.60°] in the ischemic response to the test group vs 1.16° [0.57°] in normal group; P =.37). A more impaired peak basal rotation was found in patients with anterior or anterior+posterior involvement (anterior ischemic response, +1.22° [2.45°]; anterior + posterior ischemic response, -0.20° [2.25°]; posterior ischemic response, -0.71° [1.96°]; normal response, -0.65° [2.60°]; P =.02).

CONCLUSIONS

Basal rotation at peak exercise is impaired in patients with an ischemic response to exercise echocardiography, particularly in those with anterior involvement. Apical rotation and torsion are similar to those in patients with normal exercise echocardiography.

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.

Robust model-based quantification of global ventricular torsion from spatially sparse three-dimensional time series data by orthogonal distance regression: evaluation in a canine animal model under different pacing regimes

BACKGROUND

Quantification of global ventricular rotational deformation, expressed as twist or torsion, and its dynamic changes is important in understanding the pathophysiology of heart disease and its therapy. Various techniques, such as sonomicrometry, allow tracking of specific sites within the myocardium. Quantification of twist from such data requires a longitudinal reference axis of rotation. Current methods require specific positioning and numbers of myocardial markers and assumptions about temporal positional evolution that may be violated during dyssynchronous contraction.

METHODS

We present a new method to assess myocardial twist that makes minimal fully explicit assumptions while removing extraneous assumptions, by performing a least squares orthogonal distance regression of all position data on an ellipsoidal ventricular model. Rotational deformation is quantified in terms of the ellipsoid's internal coordinate system, allowing intuitive visualization.

RESULTS

We tested this method on a set of sparse, noisy sonomicrometric crystal data in dogs under different pacing regimes to model dyssynchrony and cardiac resynchronization. We found that this method yielded robust and plausible data. This technique is also fully automated while identifying when data may be insufficient for reliable quantification of rotational deformation.

CONCLUSION

This approach may allow future analysis of myocardial contraction with less tracking sites and relaxed positioning requirements while identifying situations where data are insufficient for reliable quantification of rotational deformation.

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.

[Myocardial MR tagging: analysis of regional and global myocardial function]

Myocardial MR tagging is a powerful method which allows for assessment of myocardial function and may become an important tool for clinical evaluation of cardiac dysfunction, particularly in ischemic heart disease. In addition to visual assessment it allows direct quantification of myocardial deformation and strain to measure contractility. The use of myocardial tagging has provided new insights into the (patho)physiology of regional wall motion, and several parameters have been described as being useful to identify an ischemic response of the myocardium. One challenge encountered with tagging at 1.5 T is the fading of tags at end-diastole, greatly limiting the evaluation of myocardial function during diastole. Due to longer T(1) relaxation times of the myocardium, tagging at 3 T has shown to have a higher CNR(Tag) and better tag persistence when compared to current clinical gradient-echo tagging protocols at 1.5 T. As a consequence, tagging at higher field strengths may be well suited for the characterization of the diastolic portion of the cardiac cycle in future applications.

Left ventricular strain and untwist in hypertrophic cardiomyopathy: relation to exercise capacity

Background

Nonobstructive hypertrophic cardiomyopathy (nHCM) is often associated with reduced exercise capacity despite hyperdynamic systolic function as measured by left ventricular ejection fraction. We sought to examine the importance of left ventricular strain, twist, and untwist as predictors of exercise capacity in nHCM patients.

Methods

Fifty-six nHCM patients (31 male and mean age of 52 years) and 43 age- and gender-matched controls were enrolled. We measured peak oxygen consumption (peak Vo₂) and acquired standard echocardiographic images in all participants. Two-dimensional speckle tracking was applied to measure rotation, twist, untwist rate, strain, and strain rate.

Results

The nHCM patients exhibited marked exercise limitation compared with controls (peak Vo₂ 23.28 ± 6.31 vs 37.70 ± 7.99 mL/[kg min], P < .0001). Left ventricular ejection fraction in nHCM patients and controls was similar (62.76% ± 9.05% vs 62.48% ± 5.82%, P = .86). Longitudinal, radial, and circumferential strain and strain rate were all significantly reduced in nHCM patients compared with controls. There was a significant delay in 25% of untwist in nHCM compared with controls. Both systolic and diastolic apical rotation rates were lower in nHCM patients. Longitudinal systolic and diastolic strain rate correlated significantly with peak Vo₂ (r = −0.34, P = .01 and r = 0.36, P = .006, respectively). Twenty-five percent untwist correlated significantly with peak Vo₂ (r = 0.36, P = .006).

Conclusions

In nHCM patients, there are widespread abnormalities of both systolic and diastolic function. Reduced strain and delayed untwist contribute significantly to exercise limitation in nHCM patients.

Evaluation of left ventricular rotation in obese subjects by velocity vector imaging

AIMS

Obesity is a well-known risk factor in the development of cardiovascular disease. We hypothesize that early left ventricular (LV) dysfunction secondary to obesity could be signalled by abnormal LV rotation.

METHODS AND RESULTS

This prospective study examined 60 subjects divided into two groups: obese group with body mass index (BMI) >or=30 and control group with BMI <25. The peak rotation, twist, and torsion of the left ventricle were studied in obese and control subjects, using velocity vector imaging. Age and gender were comparable between the two groups. Obese subjects had higher BMI, waist circumference, fasting glucose, triglycerides, systolic and diastolic blood pressure, low-density lipoprotein cholesterol, and lower high-density lipoprotein cholesterol (P < 0.05). In obese subjects, LV mass and LV mass index were increased, and the ratio of mitral early and late diastolic filling velocity was decreased (P < 0.05). In obese subjects, the peak twist and torsion of the left ventricle displayed a lower trend, and the peak rotation of the left ventricle apex decreased significantly (3.81 +/- 2.09 degrees vs. 5.77 +/- 3.27 degrees , P < 0.001).

CONCLUSION

Obesity was associated with changes in LV rotation. Velocity vector imaging is a feasible and reproducible echocardiographic technique for the detection of early subclinical LV dysfunction.

Validation of cardiac accelerometer sensor measurements

In this study we have investigated the accuracy of an accelerometer sensor designed for the measurement of cardiac motion and automatic detection of motion abnormalities caused by myocardial ischaemia. The accelerometer, attached to the left ventricular wall, changed its orientation relative to the direction of gravity during the cardiac cycle. This caused a varying gravity component in the measured acceleration signal that introduced an error in the calculation of myocardial motion. Circumferential displacement, velocity and rotation of the left ventricular apical region were calculated from the measured acceleration signal. We developed a mathematical method to separate translational and gravitational acceleration components based on a priori assumptions of myocardial motion. The accuracy of the measured motion was investigated by comparison with known motion of a robot arm programmed to move like the heart wall. The accuracy was also investigated in an animal study. The sensor measurements were compared with simultaneously recorded motion from a robot arm attached next to the sensor on the heart and with measured motion by echocardiography and a video camera. The developed compensation method for the varying gravity component improved the accuracy of the calculated velocity and displacement traces, giving very good agreement with the reference methods.

Expanding role of cardiovascular magnetic resonance in left and right ventricular diastolic function

This article focuses on the role of cardiovascular magnetic resonance (CMR) in understanding the physiology of diastolic function and on the future applications of CMR as they relate to diastolic function evaluation. CMR has a demonstrated potential to define diastolic function and quantify its properties, in terms of active and passive stages, and its relaxation and compliance characteristics. CMR is also useful for assessing inflow and myocardial velocities, and untwisting properties of the chamber and myocardium, thus providing insights not fully available in other invasive and noninvasive strategies. CMR, which offers the necessary capabilities to evaluate the complex structure of the right ventricle, can serve in the future as the standard for evaluating diastolic function as it currently does for systolic function.

Left ventricular torsion in paced patients

BACKGROUND

In healthy people the left ventricle presents a counter-clockwise apical rotation and a clockwise basal rotation ending in late systole. In early systole (during isovolumic contraction) there is a fast and inverse rotation (counter-clockwise at the base and clockwise at the apex). This opposite rotation between apex and base produces the systolic torsion of the left ventricle. The effect of permanent conventional pacing on this torsion is little known.

OBJECTIVES

The aim of this study was to assess, by speckle tracking echocardiography, left ventricular rotation and torsion in patients conventionally paced at the apex of the right ventricle.

METHODS

Left ventricular apical and basal rotation and the consequent torsion were evaluated by means of speckle tracking echocardiography, in 13 paced patients, without ischemic or valvular disease, and in 17 healthy participants. Left ventricular dyssynchrony was evaluated by means of temporal uniformity of strain.

RESULTS

In the paced group there was a significant reduction in early-systolic clockwise torsion (-0.4 degrees +/- 1.2 vs. -1.5 degrees +/- 1.6; P = 0.04), and in late-systolic counter-clockwise torsion (15.1 degrees +/- 4.3 vs. 19.1 degrees +/- 5.5; P = 0.03). Circumferential temporal uniformity of strain averaged significantly lower in paced patients.

CONCLUSIONS

Conventional pacing from the apex of the right ventricle alters both the torsional mechanic and the synchrony of the left ventricle.

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.

Apical rotation by speckle tracking echocardiography: a simplified bedside index of left ventricular twist

OBJECTIVE

The study objective was to determine whether left ventricular (LV) apical rotation by speckle tracking echocardiography (STE) may serve as a clinically feasible index of LV twist. LV twist has been proposed as a sensitive marker of LV function, but clinical implementation has not been feasible because of the complexity and limitations of present methodologies.

METHODS

The relationship between apical rotation and LV twist was investigated in anesthetized dogs (n = 9) and a clinical study that included healthy controls (n = 18) and patients (n = 27) with previous myocardial infarction. Rotation by STE was compared with twist measured by magnetic resonance imaging and sonomicrometry in humans and dogs, respectively.

RESULTS

In dogs, apical rotation by STE correlated well with LV twist over a wide range of loading conditions and inotropic states, and during myocardial ischemia (R = 0.94, P < .01). Similarly, in humans there was a strong correlation between apical rotation and twist (R = 0.88, P < .01) but only a weak correlation between basal rotation and twist (R = 0.53, P < .01). Apical rotation accounted for 72% +/- 14% and 73% +/- 15% of the twisting deformation by magnetic resonance imaging in controls and patients, respectively. In dogs, apical rotation and twist decreased during myocardial ischemia (P < .05). In patients, LV twist and apical rotation were reduced (P < .05) only when LV ejection fraction was less than 50%.

CONCLUSION

Apical rotation represents the dominant contribution to LV twist, and apical rotation by STE reflects LV twist over a wide range of hemodynamic conditions. These findings suggest that apical rotation by STE may serve as a simple and feasible clinical index of LV twist.

Clinical assessment of left ventricular systolic torsion: effects of myocardial infarction and ischemia

BACKGROUND

The helical arrangement of myocardial fibers leads to left ventricular (LV) torsion, a vital contributor to systolic and diastolic function. Rotation and torsion can now be measured; we sought to determine the utility of torsion as a marker of LV function at rest and after stress in patients with myocardial infarctions (MIs) and ischemia.

METHODS

Dobutamine echocardiography was performed in 125 patients. After the exclusion of 40 patients with suboptimal images, LV systolic rotation and torsion were measured offline using speckle-tracking echocardiography in 44 patients with and 41 without prior MIs. Hemodynamic findings and the extent of infarction and ischemia were correlated with length-corrected torsion measurements at baseline and at peak-dose dobutamine.

RESULTS

Resting global and regional LV systolic torsion were significantly reduced in patients with compared with those without previous MIs (1.16 +/- 1.15 degrees /cm vs 3.16 +/- 1.3 degrees /cm, P < .001), and global systolic torsion was an independent correlate of LV ejection fraction (LVEF) (P = .04). There was no difference in global LV systolic torsion in patients with anteroapical or inferoposterior infarcts (1.81 +/- 1.13 degrees /cm vs 2.27 +/- 1.18 degrees /cm, P = NS) and no differences in regional torsion. Torsion was most impaired in patients with multiple areas of infarction (1.03 +/- 0.89 degrees /cm, P < .001). However, dobutamine-induced ischemia (2.59 +/- 1.14 ischemic segments) had no effect on global and regional systolic torsion at peak dose or change in torsion from rest to peak dose.

CONCLUSIONS

The influence of MI on LV systolic torsion appears to be related to infarct size rather than site, and torsion was an independent determinant of resting function. LV torsion was not significantly influenced by stress-induced myocardial ischemia.

Echocardiography in Heart Failure

Echocardiography is well qualified to meet the growing need for noninvasive imaging in the expanding heart failure (HF) population. The recently-released American College of Cardiology/American Heart Association guidelines for the diagnosis and management of HF labeled echocardiography "the single most useful diagnostic test in the evaluation of patients with HF...," because of its ability to accurately and noninvasively provide measures of ventricular function and assess causes of structural heart disease. It can also detect and define the hemodynamic and morphologic changes in HF over time and might be equivalent to invasive measures in guiding therapy. In this article we will discuss: 1) the clinical uses of echocardiography in HF and their prognostic value; 2) the use of echocardiography to guide treatment in HF patients; and 3) promising future techniques for echocardiographic-based imaging in HF. In addition, we will highlight some of the limitations of echocardiography.

Effect of right ventricular pacing on cardiac apex rotation assessed by a gyroscopic sensor

To quantify cardiac apex rotation (CAR), the authors recently proposed the use of a Coriolis force sensor (gyroscope) as an alternative to other complex techniques. The aim of this study was to evaluate the effects of right ventricular (RV) pacing on CAR. A sheep heart was initially paced from the right atrium to induce a normal activation sequence at a fixed heart rate (AAI mode) and then an atrioventricular pacing was performed (DOO mode, AV delay = 60 ms). A small gyroscope was epicardially glued on the cardiac apex to measure the angular velocity (Ang V). From AAI to DOO pacing mode, an increase (+9.2%, p < 0.05) of the maximum systolic twisting velocity (Ang VMAX) and a marked decrease (-19.9%, p < 0.05) of the maximum diastolic untwisting velocity (Ang VMIN) resulted. RV pacing had negligible effects (-3.1%, p = 0.09) on the maximum angle of CAR, obtained by integrating Ang V. The hemodynamic parameters of systolic (LVdP/dtMAX) and diastolic (LVdP/dtMIN) cardiac function showed slight variations (-3.8%, p < 0.05 and +3.9%, p < 0.05, respectively). Results suggest that cardiac dyssynchrony induced by RV pacing can alter the normal physiological ventricular twist patterns, particularly affecting diastolic untwisting velocity.

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.

First Experimental Evaluation of Cardiac Apex Rotation with an Epicardial Coriolis Force Sensor

Cardiac apex rotation, quantified by sophisticated techniques (radiopaque markers and tagged magnetic resonance), has been shown to provide a sensitive index of left ventricle (LV) dynamics. The authors describe the first experimental assessment of cardiac apex rotation using a gyroscopic sensor based on Coriolis force, epicardially glued on the apex. Dynamics of apex rotation were evaluated in a sheep at baseline, after a positive inotropic drug infusion, and after impairment of cardiac function induced by coronary ligation. To evaluate the efficacy of the sensor to monitor cardiac function, results were compared to contractility variations expressed by the maximum value of the first derivative of LV pressure (LVdP/dtMAX). After inotropic drug infusion, a parallel increasing trend resulted for LVdP/dtMAX, for the maximum value of angular velocity measured by the sensor, and for apex rotation angle derived from velocity signal (+146%, +155%, and +11% from baseline, respectively), whereas a decreasing trend of all three parameters resulted after coronary ligation (-35%, -31%, and -65%). The twist pattern also was altered from baseline. These initial results suggest that the use of an implantable rotation sensor based on Coriolis force can be an efficient and effective tool to assess LV torsional deformation both in normal and failing hearts.

Differences in left ventricular long-axis function from mice to humans follow allometric scaling to ventricular size

While the heart size maintains a constant proportion to body size, heart function parameters, such as heart rate and cardiac output, show a more complex scaling pattern. How these phenomena affect the long-axis left ventricular (LV) function is unknown. We studied 10 mice, 15 rats, 6 rabbits, 8 mongrel dogs and 38 human volunteers. Doppler tissue echocardiography data were postprocessed to reconstruct mitral annulus (MA) peak systolic velocity and displacement. The relationship between MA peak velocity, MA displacement and LV ejection time, and LV end-diastolic volume (and mass) were fit to an allometric (power-law) equation Y=kMbeta. LV mass varied from 0.062 to 255 g, while end-diastolic volume varied from 0.014 to 205 ml. beta values of the relation between LV ejection time and LV end-diastolic volume and mass were 0.247+/-0.017 and 0.267+/-0.018, respectively. beta values of the relationship between MA displacement and LV end-diastolic volume and mass were 0.358+/-0.047 and 0.390+/-0.051 (P<0.023 versus beta of LV ejection time). beta values of the relationship between MA peak systolic velocity and LV end-diastolic volume and mass were 0.096+/-0.012 and 0.100+/-0.013, respectively (P<0.0001 versus 0). Finally, beta values of the relationship between the long-to-short axis displacement ratio and LV end-diastolic volume and mass were 0.077+/-0.017 and 0.086+/-0.019 (P<0.0001 versus 0). We conclude that MA velocity, displacement, and long-to-short axis displacement ratio scale allometrically to heart size. This reduces the relative long-axis contribution to heart function in small mammals.

Magnetic resonance stress tagging in ischemic heart disease

High-dose dobutamine magnetic resonance stress testing has been shown to be superior to dobutamine stress echocardiography for diagnosis of coronary artery disease (CAD). We determined the feasibility of quantitative myocardial tagging during low- and high-dose dobutamine stress and tested the ability of global systolic and diastolic quantitative parameters to identify patients with significant CAD. Twenty-five patients suspected of having significant CAD were examined with a standard high-dose dobutamine/atropine stress magnetic resonance protocol (1.5-T scanner, Philips). All patients underwent invasive coronary angiography as the standard of reference for the presence (n = 13) or absence (n = 12) of significant CAD. During low-dose dobutamine stress, systolic (circumferential shortening, systolic rotation, and systolic rotation velocity) and diastolic (velocity of circumferential lengthening and diastolic rotation velocity) parameters changed significantly in patients without CAD (all P < 0.05 vs. rest) but not in patients with CAD. Identification of patients without and with CAD during low-dose stress was possible using the diastolic parameter of "time to peak untwist." At high-dose stress, none of the global systolic or diastolic parameters showed the potential to identify the presence of significant CAD. With myocardial tagging, a quantitative analysis of systolic and diastolic function was feasible during low- and high-dose dobutamine stress. In our study, the diastolic parameter of time to peak untwist as assessed during low-dose dobutamine stress was the most promising global parameter for identification of patients with significant CAD. Thus quantitative myocardial tagging may become a tool that reduces the need for high-dose dobutamine stress.

Cardiac rotation and relaxation in patients with chronic heart failure

BACKGROUND

The normal left ventricle shows a systolic wringing motion with clockwise rotation at the base and counterclockwise rotation at the apex.

PURPOSE

The aim of the present study was (1) to assess left ventricular (LV) contraction and relaxation in patients with chronic heart failure (CHF), and (2) to evaluate the effect of medical therapy on LV contraction-relaxation behavior.

METHODS

Magnetic resonance was used to examine LV motion by labeling specific LV regions in three planes (myocardial tagging). Twenty-three subjects were included, nine healthy controls and 14 CHF patients. Cardiac motion was determined from the deformation of a rectangular grid in a basal and apical plane. CHF patients were put on triple therapy with ACE-inhibitors, beta-blockers and spironolactone. Follow-up examination (n=9) was performed after 6 months.

RESULTS

In controls, systolic rotation was -9.5+/-2 degrees at the base and +3.3+/-1 degrees at the apex. In CHF patients, rotation was reduced both at the base (-3.4+/-2 degrees , P<0.01) and the apex (+0.9+/-3 degrees , P<0.05). Similarly, regional ejection fraction (REF) was reduced in CHF patients both at the base and the apex. Medical therapy was associated with an improvement in REF, but systolic rotation improved only at the base (-4.6+/-2 degrees , P<0.05).

CONCLUSIONS

Systolic wringing motion with clockwise rotation at the base and counterclockwise rotation at the apex is maintained in CHF although reduced. Heart failure treatment is associated with an improvement in REF, whereas rotation improved only at the base, but not at the apex. Thus, there is an uncoupling between regional shortening and rotation in CHF patients.

Detection of acute myocardial ischemia during percutaneous transluminal coronary angioplasty by endocardial acceleration

The first heart sound is generated by vibrations from the myocardium during isovolumic contraction. Peak endocardial acceleration (PEA) has been used previously to measure these vibrations in humans and correlates with myocardial contractility during inotropic interventions. It is unknown if changes in PEA can be used to characterize a reduction in contractility during ischemic episodes. This study was designed to evaluate the use of an endocardial accelerometer for the detection of acute myocardial ischemia. Thirteen patients undergoing routine percutaneous transluminal coronary angioplasty (PTCA) consented to having a single-axis, lead-based accelerometer positioned in the right ventricular apex. PEA was defined as the maximum peak-to-peak amplitude during a window 50 ms before to 200 ms following the peak R wave. Time of endocardial acceleration (TEA) was defined as the time from the peak R wave to the maximum accelerometer signal within this window. To obtain a more robust estimate of the strength of vibrations, a 100-beat template of the accelerometer signal was constructed at baseline and applied as a matched filter during ischemia. The peak magnitude of the filtered endocardial accelerometer signal (Max Filtered EA) was used as an index of signal intensity. Median baseline PEA, TEA, and Max Filtered EA were 0.91 +/- 0.35 g, 75.2 +/- 16.2 ms, and 0.40 +/- 0.20 g, respectively. PEA and Max Filtered EA significantly decreased by 7% during ischemia (0.91 to 0.85 g and 0.40 to 0.37 g, both P < 0.05, respectively). TEA did not significantly change from baseline (77.0 ms, P = ns). The results of this study suggest that acute ischemia can be detected with an endocardial accelerometer in humans.

Alterations of systolic left ventricular twist after acute myocardial infarction

We sought to characterize the alterations of left ventricular (LV) twist after acute myocardial infarction in humans and to study their relationship to usual parameters of LV function. Systolic LV twist was measured by color tissue Doppler echocardiography (TDE) in 34 patients after anterior myocardial infarction and in 20 controls. In a subset of controls and patients, the assessment of LV twist by TDE was validated against magnetic resonance (MR) tissue tagging with good agreement between the two methods. Myocardial ischemia was responsible for a decrease in LV twist in infarct patients (P < 0.01). The decrease in LV twist was correlated with the extent of the asynergic area and global LV function as assessed by LV cineangiography (P < 0.001). Thus acute myocardial ischemia is responsible for a decrease in LV twist that is related to global LV function. Color TDE is a promising technique for straightforward assessment of LV twist in humans.

MRI assessment of LV relaxation by untwisting rate: a new isovolumic phase measure of tau

Most noninvasive measures of diastolic function are made during left ventricular (LV) filling and are therefore subject to "pseudonormalization," because variation in left atrial (LA) pressure may confound the estimation of relaxation rate. Counterclockwise twist of the LV develops during ejection, but untwisting occurs rapidly during isovolumic relaxation, before mitral opening. We hypothesized that the rate of untwisting might reflect the process of relaxation independent of LA pressure. Recoil rate (RR), the velocity of LV untwisting, was measured by tagged magnetic resonance imaging and regressed against the relaxation time constant (tau), recorded by catheterization, in 10 dogs at baseline and after dobutamine, saline, esmolol, and methoxamine treatment. RR correlated closely (average r = -0.86) with tau and was unaffected by elevated LA pressure. Multiple regression showed that tau, but not LA or aortic pressure, was an independent predictor of RR (P < 0.0001, P = 0.99, and P = 0.18, respectively). The rate of recoil of torsion, determined wholly noninvasively, provides an isovolumic phase, preload-independent assessment of LV relaxation. Use of this novel parameter should allow the detailed study of diastolic function in states known to affect filling rates, such as aging, hypertension, and congestive heart failure.

Cardiac rotation and relaxation after anterolateral myocardial infarction

BACKGROUND

Both systolic and diastolic dysfunction have been observed in patients with anterolateral myocardial infarction. Diastolic dysfunction is related to disturbances in relaxation and diastolic filling.

OBJECTIVE

To analyse cardiac rotation, regional shortening and diastolic relaxation in patients with anterolateral infarction.

METHODS

Cardiac rotation and relaxation in controls and patients with chronic anterolateral infarction were assessed by myocardial tagging. Myocardial tagging is based on magnetic resonance imaging and allows us to label specific myocardial regions for imaging cardiac motion (rotation, translation and radial displacement). A rectangular grid was placed on the myocardium (basal, equatorial and apical short-axis plane) of each of 18 patients with chronic anterolateral infarction and 13 controls. Cardiac rotation, change in area and shortening of circumference were determined in each case.

RESULTS

The left ventricle in controls performs a systolic wringing motion with a clockwise rotation at the base and a counterclockwise rotation at the apex when viewed from the apex. During relaxation a rotational motion in the opposite direction (namely untwisting) can be observed. In patients with anterolateral infarction, there is less systolic rotation at the apex and diastolic untwisting is delayed and prolonged in comparison with controls. In the presence of a left ventricular aneurysm (n = 4) apical rotation is completely lost. There is less shortening of circumference in infarcted and remote regions.

CONCLUSIONS

The wringing motion of the myocardium might be an important mechanism involved in maintaining normal cardiac function with minimal expenditure of energy. This mechanism no longer operates in patients with left ventricular aneurysms and operates significantly less than normal in those with anterolateral hypokinaesia. Diastolic untwisting is significantly delayed and prolonged in patients with anterolateral infarction, which could explain the occurrence of diastolic dysfunction in these patients.