Alterations in left ventricular torsion in tachycardia-induced dilated cardiomyopathy

A long duration race induces a decrease of left ventricular strains, twisting mechanics and myocardial work in trained adolescents

BACKGROUND

We investigated the acute cardiac consequences of a long-duration (>5 h) adventure race in adolescent athletes from evaluations of left ventricular (LV) strains and myocardial work.

METHODS

Twenty trained male adolescents (i.e. 8 ± 4 hours/week of endurance sports) aged 14 to 17 years participated in a competitive long-duration adventure race. Blood samples were collected before, immediately and 24 h after the race to determine the time course of troponin I (cTnI) considered as a myocardial damage biomarker. Resting echocardiography were conducted before and after the race to assess myocardial regional strains, LV twisting mechanics and myocardial work using speckle tracking echocardiography.

RESULTS

The mean completion time of the race was 05:38 ± 00:20 h, with a mean heart rate (HR) of 83 ± 5% of maximal HR. cTnI concentration significantly increased in 16/20 participants after the race (pre: 0.001 ± 0.002 vs. post: 0.244 ± 0.203 ng·dL^-1, p < 0.001) and returned to baseline within 24 h. Stroke volume, ejection fraction and global longitudinal strains remained unchanged after the race while LV twist and global myocardial work significantly decreased (8.6 ± 3.3 vs. 6.3 ± 3.3 deg and 2080 ± 250 vs. 1781 ± 334 mmHg%, p < 0.05). Diastolic function, indexes of myocardial relaxation and LV untwisting rate (-91.0 ± 19.0 vs. -56.4 ± 29.1 deg·s^-1, p < 0.001) were affected after the race.

CONCLUSION

We demonstrated for the first time that, in trained adolescents, a high-intensity endurance exercise of several hours induced an increase of the cTnI concentration associated with an alteration of myocardial function.

The effect of fiber-matrix interaction on the kinking instability arising in the torsion of stretched fibrous biofilaments

The response of fibrous soft tissues undergoing torsional deformations is a topic of current interest. Such deformations are common in ligaments and tendons and are also of particular interest in cardiac mechanics. The problem of torsion superimposed on extension of incompressible hyperelastic solid circular cylinders is a classic problem of nonlinear elasticity that has been considered by many authors in the context of rubber elasticity particularly for isotropic materials. A striking feature of such problems is the instability that arises with sufficiently large twist where a kink and then a knot suddenly appears. An energy approach to examining this instability when the extension and twist are prescribed was described by Gent and Hua (2004) and illustrated there for a neo-Hookean isotropic elastic material. The theoretical results were compared with experimental observations on natural rubber rods. Murphy (2015) has shown that the approach of Gent and Hua (2004) for isotropic materials can be simplified when the rods are assumed to be thin and this theory was applied to transversely isotropic materials by Horgan and Murphy (2016). In contrast with the case for isotropic materials, it was shown there that the kinking instability occurs even in the absence of stretch, i.e., for the case of pure torsion. Here we are concerned with the implications of this simplified thin rod instability theory for fiber-reinforced transversely isotropic materials that reflect fiber-matrix interaction. It is again shown that the kinking instability occurs even in the absence of stretch, i.e., for the case of pure torsion. The results are illustrated for a specific strain-energy density function that models fiber-matrix interaction. It is shown that the critical twist at which kinking occurs decreases as a measure of fiber-matrix interaction is increased so that the fiber-matrix interaction has a destabilizing effect. The results are illustrated using experimental data of other authors for skeletal muscles and for porcine brain white matter tissue.

How His bundle pacing prevents and reverses heart failure induced by right ventricular pacing

Ideal heart performance demands vigorous systolic contractions and rapid diastolic relaxation. These sequential events are precisely timed and interdependent and require the rapid synchronous electrical stimulation provided by the His-Purkinje system. Right ventricular (RV) pacing creates slow asynchronous electrical stimulation that disrupts the timing of the cardiac cycle and results in left ventricular (LV) mechanical asynchrony. Long-term mechanical asynchrony produces LV dysfunction, remodeling, and clinical heart failure. His bundle pacing preserves synchronous electrical and mechanical LV function, prevents or reverses RV pacemaker-induced remodeling, and reduces heart failure.

The promising future of ventricular restraint therapy for the management of end-stage heart failure

Complicated pathophysiological syndrome associated with irregular functioning of the heart leading to insufficient blood supply to the organs is linked to congestive heart failure (CHF) which is the leading cause of death in developed countries. Numerous factors can add to heart failure (HF) pathogenesis, including myocardial infarction (MI), genetic factors, coronary artery disease (CAD), ischemia or hypertension. Presently, most of the therapies against CHF cause modest symptom relief but incapable of giving significant recovery for long-term survival outcomes. Unfortunately, there is no effective treatment of HF except cardiac transplantation but genetic variations, tissue mismatch, differences in certain immune response and socioeconomic crisis are some major concern with cardiac transplantation, suggested an alternate bridge to transplant (BTT) or destination therapies (DT). Ventricular restraint therapy (VRT) is a promising, non-transplant surgical treatment wherein the overall goal is to wrap the dilated heart with prosthetic material to mechanically restrain the heart at end-diastole, stop extra remodeling, and thereby ultimately improve patient symptoms, ventricular function and survival. Ventricular restraint devices (VRDs) are developed to treat end-stage HF and BTT, including the CorCap cardiac support device (CSD) (CSD; Acorn Cardiovascular Inc, St Paul, Minn), Paracor HeartNet (Paracor Medical, Sunnyvale, Calif), QVR (Polyzen Inc, Apex, NC) and ASD (ASD, X. Zhou). An overview of 4 restraint devices, with their precise advantages and disadvantages, will be presented. The accessible peer-reviewed literature summarized with an important considerations on the mechanism of restraint therapy and how this acquaintance can be accustomed to optimize and improve its effectiveness.

Exo-organoplasty interventions: A brief review of past, present and future directions for advance heart failure management

Heart failure (HF) is a debilitating disease in which abnormal function of the heart leads to imbalance of blood demand to tissues and organs. The pathogenesis of HF is very complex and various factors can contribute including myocardial infarction, ischemia, hypertension and genetic cardiomyopathies. HF is the leading cause of death and its prevalence is expected to increase in parallel with the population age. Different kind of therapeutic approaches including lifestyle modification, medication and pacemakers are used for HF patients in NYHA I-III functional class. However, for advance stage HF patient's (NYHA IV), ventricle assist devices are clinically use and stem cells are under active investigation. Most of these therapies leads to modest symptoms relief and have no significant role in long-term survival rate. Currently there is no effective treatment for advance HF except heart transplantation, which is still remain clinically insignificant because of donor pool limitation. As HF is a result of multiple etiologies therefore multi-functional therapeutic platform is needed. Exo-organoplasty interventions are studied from almost one century. The major goals of these interventions are to treat various kind of heart disease from outside the heart muscle without having direct contact with blood. Various kind of interventions (devices and techniques) are developed in this arena with the passage of time. The purpose of this review is to describe the theory behind intervention devices, the devices themselves, their clinical results, advantages and limitations. Furthermore, to present a future multi-functional therapeutic platform (ASD) for advance stage HF management.

What About Tachycardia-induced Cardiomyopathy?

Long-standing tachycardia is a well-recognised cause of heart failure and left ventricular dysfunction, and has led to the nomenclature, tachycardia-induced cardiomyopathy (TIC). TIC is generally a reversible cardiomyopathy if the causative tachycardia can be treated effectively, either with medications, surgery or catheter ablation. The diagnosis is usually made after demonstrating recovery of left ventricular function with normalisation of heart rate in the absence of other identifiable aetiologies. One hundred years after the first reported case of TIC, our understanding of the pathophysiology of TIC in humans remains limited despite extensive work in animal models of TIC. In this review we will discuss the proposed mechanisms of TIC, the causative tachyarrhythmias and their treatment, outcomes for patients diagnosed with TIC, and future directions for research and clinical care.

Arrhythmia-Induced Cardiomyopathies: Mechanisms, Recognition, and Management

Arrhythmia-induced cardiomyopathy (AIC) is a potentially reversible condition in which left ventricular dysfunction is induced or mediated by atrial or ventricular arrhythmias. Cellular and extracellular changes in response to the culprit arrhythmia have been identified, but specific pathophysiological mechanisms remain unclear. Early recognition of AIC and prompt treatment of the culprit arrhythmia using pharmacological or ablative techniques result in symptom resolution and recovery of ventricular function. Although cardiomyopathy in response to an arrhythmia may take months to years to develop, recurrent arrhythmia can result in rapid decline in ventricular function with development of heart failure, suggesting residual ultrastructural abnormalities. Reports of sudden death in patients with normalized left ventricular ejection fraction cast doubt on the complete reversibility of this condition. Several aspects of AIC, including specific pathophysiological mechanisms, predisposing factors, optimal therapeutic strategies to prevent ultrastructural changes, and long-term risk of sudden death remain unresolved and need further research.

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.

Effects of small platform catheter-based left ventricular assist device support on regional myocardial signal transduction

OBJECTIVES

Left ventricular (LV) assist device (LVAD) support reduces pathological loading. However, load-induced adaptive responses may be suppressed. Pathological loading dysregulates cardiac G protein-coupled receptor (GPCR) signaling. Signaling through G proteins is deleterious, whereas beta (β)-arrestin-mediated signaling is cardioprotective. We examined the effects of pathological LV loading/LV dysfunction and treatment via LVAD, on β-arrestin-mediated signaling, and genetic networks downstream of load.

METHODS

An ovine myocardial infarction (MI) model was used. Sheep underwent sham thoracotomy (n = 3), mid-left anterior descending coronary artery ligation to produce MI (n = 3), or MI with placement of a small-platform catheter-based LVAD (n = 3). LVAD support was continued for 2 weeks. Animals were maintained for a total of 12 weeks. Myocardial specimens were harvested and analyzed.

RESULTS

MI induced β-arrestin activation. Increased interactions between epidermal growth factor receptor and β-arrestins were observed. LVAD support inhibited these responses to MI (P < .05). LVAD support inhibited the activation of cardioprotective signaling effectors Akt (P < .05), and, to a lesser extent, extracellular regulated kinase 1/2 (P not significant); however, MI resulted in regional activation of load-induced GPCR signaling via G proteins, as assessed by the induction of atrial natriuretic peptide mRNA expression in the MI-adjacent zone relative to the MI-remote zone (P < .05). MI-adjacent zone atrial natriuretic peptide expression was renormalized with LVAD support.

CONCLUSIONS

LVAD support inhibited cardioprotective β-arrestin-mediated signaling. However, net benefits of normalization of load-induced GPCR signaling were observed in the MI-adjacent zone. These findings may have implications for the optimal extent and duration of unloading, and for the development of adjunctive medical therapies.

Atrial fibrillation and heart failure: cause or effect?

Atrial fibrillation (AF) and heart failure (HF) are two epidemics of the century that have a close and complex relationship. The mechanisms underlying this association remain an area of ongoing intense research. In this review, we will describe the relationship between these two public health concerns, the mechanisms that fuel the development and perpetuation of both, and the evolving concepts that may revolutionize our approach to this dual epidemic.

Reversal of cardiomyopathy in patients with congestive heart failure secondary to tachycardia

OBJECTIVES

Tachycardia-induced cardiomyopathy (TCM) is a reversible cause of heart failure. Little is known of the characteristics of tachycardia associated with the development of left ventricular (LV) dysfunction and the reversal of cardiomyopathy after cure of tachycardia. This study aimed to examine the reversal of cardiomyopathy in patients undergoing ablation with congestive heart failure secondary to tachycardia.

METHODS

A total of 625 patients underwent radiofrequency ablation for tachycardiarrhymias between January 2009 and July 2011. Echocardiography analysis was performed to identify patients with depressed LV function, defined as a left ventricular ejection fraction <50 %. Patients with preexisting structural heart disease (n = 10) were excluded. NT-pro-B-type natriuretic peptide (NT-proBNP) assessment was performed before ablation in patients considered to have TCM (n = 17). Repeated echocardiography study and NT-proBNP assessment were measured after a mean follow-up of 3 months. Levels of NT-proBNP before and after ablation were compared. Reversal of cardiomyopathy was also assessed.

RESULTS

The incidence of TCM was 2.7 % (12 males; age, 35.8 ± 17.1 years). Successful ablation was performed in 16 of 17 patients (94.1 %). There was a significant improvement in left ventricular ejection fraction (36.7 ± 7.5 vs. 59.4 ± 9.7 %; P < 0.001). The mean left ventricular end-diastolic diameter before treatment was 59.5 ± 8.3 mm (range, 43 to 70), compared with 51.9 ± 7.4 mm (range, 40 to 67) (P = 0.009) after 3 months follow-up. The levels of NT-proBNP decreased after ablation procedure, from 4,092.6 ± 3,916.6 to 478.9 ± 881.9 pg/ml (P < 0.001). After successful ablation, ventricular function normalized in 15 of 17 (88.2 %) patients at a mean of 3 months.

CONCLUSIONS

Restoration of LV function and reversal of LV remodeling can be achieved with successful elimination of tachycardia in the majority of patients. NT-proBNP level elevates in subjects with TCM and decreases sharply after ablation.

Evaluation of left ventricular torsion by cardiovascular magnetic resonance

Recently there has been considerable interest in LV torsion and its relationship with symptomatic and pre-symptomatic disease processes. Torsion gives useful additional information about myocardial tissue performance in both systolic and diastolic function. CMR assessment of LV torsion is simply and efficiently performed. However, there is currently a wide variation in the reporting of torsional motion and the procedures used for its calculation. For example, torsion has been presented as twist (degrees), twist per length (degrees/mm), shear angle (degrees), and shear strain (dimensionless). This paper reviews current clinical applications and shows how torsion can give insights into LV mechanics and the influence of LV geometry and myocyte fiber architecture on cardiac function. Finally, it provides recommendations for CMR measurement protocols, attempts to stimulate standardization of torsion calculation, and suggests areas of useful future research.

Left ventricular torsional mechanics in uncomplicated pregnancy

BACKGROUND

Alterations in left ventricular (LV) twist (torsion) and untwist have been described for a variety of physiologic and pathologic conditions. Little information is available regarding changes in these parameters during normal pregnancy.

HYPOTHESIS

Pregnancy is associated with significant changes in LV torsional mechanics.

METHODS

Left ventricular twist and untwist was measured in 32 pregnant females (mean gestation 199 ± 48 d) and 23 nonpregnant controls using speckle-tracking echocardiography.

RESULTS

Left ventricular ejection fraction (68 ± 5% vs 66 ± 5%) was similar between the groups (P not significant). There was a significant increase in peak LV twist from nonpregnant controls (9.4 ± 3.7 degrees) to second-trimester (12.0 ± 4.2 degrees) and third-trimester subjects (12.6 ± 5.9 degrees, all P<0.05). Peak LV twist velocity was also increased in second- and third-trimester groups compared with controls (94 ± 24 degrees/sec and 93 ± 30 vs 64 ± 21 degrees/sec, respectively, both P<0.05). Both peak untwist velocity and time to peak untwist velocity were not significantly different between groups (P not significant). Multiple regression analysis indicate that only systolic blood pressure (r = 0.394, P = 0.005) was an independent predictor for increased LV torsion.

CONCLUSIONS

There are significant changes in LV torsional indices during the course of pregnancy, whereas untwist parameters remain unchanged. Blood pressure is independently associated with increased torsion during pregnancy.

Torsion of the human left ventricle: experimental analysis and computational modeling

We set a twofold investigation: we assess left ventricular (LV) rotation and twist in the human heart through 3D-echocardiographic speckle tracking, and use representative experimental data as benchmark with respect to numerical results obtained by solving our mechanical model of the LV. We aim at new insight into the relationships between myocardial contraction patterns and the overall behavior at the scale of the whole organ. It is concluded that torsional rotation is sensitive to transmural gradients of contractility which is assumed linearly related to action potential duration (APD). Pressure-volume loops and other basic strain measures are not affected by these gradients. Therefore, realistic torsional behavior of human LV may indeed correspond to the electrophysiological and functional differences between endocardial and epicardial cells recently observed in non-failing hearts. Future investigations need now to integrate the mechanical model proposed here with minimal models of human ventricular APD to drive excitation-contraction coupling transmurally.

Kinetics of Left Ventricular Strains and Torsion During Incremental Exercise in Healthy Subjects

Background—

The dynamics of systolic and diastolic strains and torsional mechanics of the left ventricle (LV) and their relation to diastolic filling never have been evaluated at various exercise intensities.

Methods and Results—

Speckle tracking echocardiography was performed in 20 healthy sedentary subjects at rest and during a progressive submaximal exercise test at 20%, 30%, and 40% of maximal aerobic power. LV twist increased progressively with exercise intensity (10.5±3.2 to 15.8±4.5°; P <0.001), whereas longitudinal strain remained unchanged after the first workload, underlining the key role of torsional reserve in systolic-diastolic coupling during exercise. The increase in diastolic untwisting (−88.7±34.2 to −182.9±53.5 deg · s −1 ; P <0.01) was correlated to enhanced systolic twist ( R =0.61; P <0.001), and its magnitude of increase was significantly higher compared to diastolic longitudinal and circumferential strain rates (119±64% versus 65±44% and 57±24%, respectively), emphasizing its contribution to diastolic filling. The timing of peak untwisting and the chronology of diastolic mechanical events were unchanged during effort. Untwisting was driven mainly by apical rotation and determined mitral opening and isovolumic relaxation time ( R =0.47 and 0.61, respectively; P <0.001), whereas basal rotation and longitudinal and circumferential diastolic strain rates were major determinants of increased early diastolic filling ( R =0.64, 0.79, and 0.81, respectively; P <0.001).

Conclusions—

The use of speckle tracking echocardiography gives new insights into physiological adaptive LV mechanics during incremental exercise in healthy subjects, underlining the key role of torsional mechanics. It might be useful to better understand the mechanisms of diastolic dysfunction and exercise intolerance in various pathological conditions.

Hemodynamic improvement in cardiac resynchronization does not require improvement in left ventricular rotation mechanics: three-dimensional tagged MRI analysis

BACKGROUND

Earlier studies have yielded conflicting evidence on whether or not cardiac resynchronization therapy (CRT) improves left ventricular (LV) rotation mechanics.

METHODS AND RESULTS

In dogs with left bundle branch block and pacing-induced heart failure (n=7), we studied the effects of CRT on LV rotation mechanics in vivo by 3-dimensional tagged magnetic resonance imaging with a temporal resolution of 14 ms. CRT significantly improved hemodynamic parameters but did not significantly change the LV rotation or rotation rate. LV torsion, defined as LV rotation of each slice with respect to that of the most basal slice, was not significantly changed by CRT. CRT did not significantly change the LV torsion rate. There was no significant circumferential regional heterogeneity (anterior, lateral, inferior, and septal) in LV rotation mechanics in either left bundle branch block with pacing-induced heart failure or CRT, but there was significant apex-to-base regional heterogeneity.

CONCLUSIONS

CRT acutely improves hemodynamic parameters without improving LV rotation mechanics. There is no significant circumferential regional heterogeneity of LV rotation mechanics in the mechanically dyssynchronous heart. These results suggest that LV rotation mechanics is an index of global LV function, which requires coordination of all regions of the left ventricle, and improvement in LV rotation mechanics appears to be a specific but insensitive index of acute hemodynamic response to CRT.

Significance of mechanical alterations in single ventricle patients on twisting and circumferential strain as determined by analysis of strain from gradient cine magnetic resonance imaging sequences

Preliminary speckle-tracking echocardiographic studies show that patients with single ventricles (SVs) have significantly decreased twisting and dyssynchrony of twisting. This could be related to abnormal cardiac looping, which leads to hearts that lack helical fiber patterns. The aim of this study was to analyze gradient cine magnetic resonance imaging (MRI) using Velocity Vector Imaging to assess cardiac mechanics. Subjects were 38 patients (aged 8 to 37 years) with SVs of left ventricular (n = 30) and indeterminate (n = 8) type who underwent cardiac MRI. Controls were 14 normal children and adults. Gradient cine MRI sequences close to the apex were subjected to a Velocity Vector Imaging analysis program adapted for MRI. In the control group, mean circumferential strain was -18.02 +/- 7.31%, mean dispersion of peak circumferential strain was 44.23 +/- 37.14 ms, and average rotation was -7.7 +/- 1.38 degrees . The rotation values were negative, or counterclockwise. In patients with SVs, mean circumferential strain was -8.87 +/- 7.30%, mean dispersion of peak circumferential strain was 181.55 +/- 76.07 ms, and average rotation was -2.6 +/- 1.24 degrees (p <0.001). Mean dispersion of the peak of rotation in the control group was 39.6 +/- 22.8 ms, compared to 166.5 +/- 72.4 ms in patients with SVs. In conclusion, this study showed a dramatic decrease in apical rotation and circumferential strain in the SV group compared to the control group. Strain and rotation mechanics at the apex in patients with SVs showed marked dyssynchrony.

Tachycardia-mediated cardiomyopathy: recognition and management

Tachycardia-mediated cardiomyopathy is a cause of ventricular dysfunction due to, at least partially, persistent tachycardia leading to cellular and extracellular perturbations. Cardiomyopathy may take years to develop, but pharmacologic management to achieve rate control and reverse remodeling, as well as cardioversion or ablative strategies to stop the tachycardia, can result in rapid recovery from symptoms and gradual improvement in left ventricular ejection fraction. However, ultrastructural changes can remain and may lead to a rapid decline in ventricular function if tachycardia recurs. Ultrastructural changes may also explain a propensity toward sudden death even if the ejection fraction normalizes. Although the etiology, pathophysiology, and late clinical manifestations of tachycardia-mediated cardiomyopathy are beginning to be understood, investigation continues, focusing on prevention, early recognition, and acute and long-term management in an attempt to lessen heart failure and prevent risk of sudden death.

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 twist mechanics in a canine model of reversible congestive heart failure: a pilot study

BACKGROUND

Left ventricular (LV) twist dynamics play an important role in LV systolic and diastolic function. The aim of this preliminary study was to investigate LV twist dynamics in a canine model of reversible congestive heart failure (CHF).

METHODS

Pacing systems were implanted in adult dogs, and continuous chronic right ventricular pacing (230-250 beats/min) was applied until CHF induction. Pacing was then stopped to allow the heart to recover. Echocardiography and LV catheterization were performed at baseline, during CHF while pacing was temporarily switched off, and during recovery. LV twist was computed as the difference between apical and basal rotation measured using 2-dimensional speckle tracking. Torsion was further calculated as LV twist divided by the LV long axis. The untwisting rate was computed as the peak diastolic time derivative of twist.

RESULTS

In 6 dogs that completed the study, we found that CHF developed after 2 to 4 weeks of pacing, with LV end-diastolic volume, end-systolic volume, end-diastolic pressure, and the time constant of relaxation during isovolumic relaxation period (tau) all increasing significantly compared with baseline and recovering to normal levels 2 to 4 weeks after pacing was stopped. LV twist, torsion, and untwisting rate decreased significantly with CHF compared with baseline and improved during recovery from CHF.

CONCLUSION

LV twist dynamics reflect pacing-induced CHF and its reversal as assessed by echocardiographic speckle tracking.

Left ventricular torsion and recoil: implications for exercise performance and cardiovascular disease

In recent years, advancements in echocardiography assessment techniques have allowed for the quantification of left ventricular (LV) rotation. This information has provided new insight into LV function in health and disease. In this review, we discuss the importance of assessing LV circumferential rotation for understanding cardiac function in a wide range of populations. We provide a synopsis of LV rotational mechanics in the context of the various techniques currently available to assess LV rotation. We also highlight the factors that alter LV function at rest and during exercise. Finally, we discuss the influences of age, sex, and cardiac pathology on LV rotation. Collectively, this review highlights the importance of understanding LV rotation and its measurement in both health and disease.

Reduced systolic torsion in chronic "pure" mitral regurgitation

BACKGROUND

Global left ventricular (LV) torsion declines with chronic ischemic mitral regurgitation (MR), which may accelerate the LV remodeling spiral toward global cardiomyopathy; however, it has not been definitively established whether this torsional decline is attributable to the infarct, the MR, or their combined effect. We tested the hypothesis that chronic "pure" MR alone reduces global LV torsion.

METHODS AND RESULTS

Chronic "pure" MR was created in 13 sheep by surgically punching a 3.5- to 4.8-mm hole (HOLE) in the mitral valve posterior leaflet. Nine control (CNTL) sheep were operated on concurrently. At 1 (WK-01) and 12 weeks (WK-12) postoperatively, the 4D motion of implanted radiopaque markers was used to calculate global LV torsion. MR-grade in HOLE was greater than CNTL at WK-01 and WK-12 (2.5+/-1.1 versus 0.6+/-0.5, P<0.001 at WK-12). HOLE LV mass index was larger at WK-12 compared with CNTL (195+/-14 versus 170+/-17 g/m(2), P<0.01), indicating LV remodeling. Global LV systolic torsion decreased in HOLE from WK-01 to WK-12 (4.1+/-2.8 degrees versus 1.7+/-1.7 degrees , P<0.01), but did not change in CNTL (5.5+/-1.8 degrees versus 4.2+/-2.7 degrees , P=NS). Global LV torsion was lower in HOLE relative to CNTL at WK-12 (P<0.05) but not at WK-01 (P=NS).

CONCLUSIONS

Twelve weeks of chronic "pure" MR resulting in mild global LV remodeling is associated with significantly increased LV mass index and reduced global LV systolic torsion, but no other significant changes in hemodynamics. MR alone is a major component of torsional deterioration in "pure" MR and may be an important factor in chronic ischemic mitral regurgitation.

Cardiac Mechanics Revisited

The keynote to understanding cardiac function is recognizing the underlying architecture responsible for the contractile mechanisms that produce the narrowing, shortening, lengthening, widening, and twisting disclosed by echocardiographic and magnetic resonance technology. Despite background knowledge of a spiral clockwise and counterclockwise arrangement of muscle fibers, issues about the exact architecture, interrelationships, and function of the different sets of muscle fibers remain to be resolved. This report (1) details observed patterns of cardiac dynamic directional and twisting motions via multiple imaging sources; (2) summarizes the deficiencies of correlations between ventricular function and known ventricular muscle architecture; (3) correlates known cardiac motions with the functional anatomy within the helical ventricular myocardial band; and (4) defines an innovative muscular systolic mechanism that challenges the previously described concept of “isovolumic relaxation.” This new knowledge may open new doors to treating heart failure due to diastolic dysfunction.

Structure and function relationships of the helical ventricular myocardial band

OBJECTIVE

Understanding cardiac function requires knowledge of the architecture responsible for the normal actions of emptying and filling. Newer imaging methods are surveyed to characterize directional (narrowing, shortening, lengthening, and widening) and twisting motions.

METHODS

These movements are defined and then compared with a spectrum of models to introduce a useful "functional anatomy" that explains cardiac spatial and temporal relationships. The sequential nature of normal contraction differs from a synchronous beat.

RESULTS

The prior concept of constriction is replaced by understanding that clockwise and counterclockwise helical motions are necessary to cause the predominant twisting motion. The helical ventricular myocardial band model of Torrent-Guasp fulfills the architectural structure to define normal function. Expansion of information from this model allows novel understanding of mechanisms that explains why a component of ventricular suction involves a systolic event, clarifies septum function, determines diastolic dysfunction, introduces new treatments, shows how knowledge of the helical structure influences understanding of atrioventricular and biventricular pacing, and creates novel methods for introducing septal pacing stimuli.

CONCLUSION

Further testing of these spatial anatomic concepts is needed to create a more accurate understanding of the architectural mechanisms that underlie cardiac dynamics to address future problems in unhealthy hearts.

Effect of mechanical dyssynchrony and cardiac resynchronization therapy on left ventricular rotational mechanics

Alterations in rotational mechanics can bring new aspects to the understanding of left ventricular (LV) dyssynchrony. The aims of this study were to investigate LV rotational mechanics in candidates for cardiac resynchronization therapy (CRT) and to assess the effect of CRT by speckle-tracking echocardiography. Fifty-four patients with heart failure and 33 healthy controls were studied. Thirty-three underwent CRT. Speckle tracking was applied to short- and long-axis views. Radial and longitudinal dyssynchrony were assessed as previously defined. Apical and basal rotations were measured as the average angular displacement about the LV central axis. LV twist and torsion were then calculated. Peak apical and basal rotation, peak LV twist and torsion, apical and basal rotation at aortic valve closure (AVC), and LV twist and torsion at AVC were significantly lower in patients than controls. Apical-basal rotation delay and AVC-to-peak LV twist interval were longer in patients and associated with decreased peak LV twist and LV twist at AVC, respectively. In patients, rotational indexes, particularly LV twist and torsion, were correlated strongly with radial dyssynchrony. LV torsion (cutoff 0.1 degrees /cm) and twist (cutoff 1 degrees ) at AVC had the highest sensitivity (90%) and specificity (77%) to predict CRT responders among all other parameters, including radial and longitudinal dyssynchrony. In conclusion, LV dyssynchrony is associated with discoordinate rotation of the apical and basal regions, which in turn significantly decreases peak LV twist and torsion and LV twist and torsion at AVC. CRT significantly restored the altered rotational mechanics in responders. These parameters have potential for predicting responders to CRT.

Effect of pregnancy on left ventricular motion (twist) in women with aortic stenosis

The combination of fixed outflow obstruction from aortic stenosis (AS) and the hemodynamic changes of pregnancy increased the risk of maternal or fetal deterioration. Left ventricular (LV) response in patients with AS to the hemodynamic changes of pregnancy has not been examined. We studied and compared myocardial mechanics with echocardiography in 3 groups of 10 women each, including (1) pregnant with bicuspid aortic valve (BAV; peak aortic gradient 59 +/-7 mm Hg, aortic valve area 0.9 +/- 0.04 cm2), (2) pregnant without BAV, and (3) nonpregnant, healthy volunteer. Measurements in the pregnant BAV group were made on 3 occasions, within a year before pregnancy (baseline), in the antepartum period, and at least 6 weeks postpartum. Tissue tracking ultrasound was used to assess longitudinal strain and LV twist. During pregnancy, peak AS gradient rose from 59 +/- 7 to 70 +/- 9 mm Hg (p = 0.004) whereas valve area remained unchanged 0.9 +/- 0.04 to 0.8 +/- 0.04 cm2 (p = 0.48) as compared with baseline (before pregnancy). Overall, in all patients, there was no significant change in the longitudinal strain (-22 +/- 1, -21 +/- 0.6, -20 +/- 0.6 percent, p = 0.21)] at baseline, during pregnancy, or after pregnancy, respectively. Patients with AS had a higher baseline LV twist compared with both control groups (5.4 +/- 0.3, pregnant, with AS; 4.1 +/- 0.8, pregnant, without AS; 3.6 +/- 0.3, nonpregnant volunteer; expressed in degrees; p = 0.023). Additionally, all but 2 patients had a significant increase in LV twist during pregnancy compared with baseline. These 2 women had symptomatic deterioration requiring urgent aortic balloon valvuloplasty. Postpartum, in all AS patients, LV twist returned to antepartum values. In conclusion, we found that LV twist was significantly increased in women with congenital AS. During pregnancy, LV twist further increased in the antepartum period, except in those women who experienced functional deterioration.

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.

Decreased left ventricular torsion and untwisting in children with dilated cardiomyopathy

The purpose of this study was to analyze left ventricular (LV) torsion and untwisting, and to evaluate the correlation between torsion and other components of LV contraction in children with dilated cardiomyopathy (DCM). Segmental and global rotation, rotational rate (Vrot) were measured at three levels of LV using the two dimensional (2D) speckle tracking imaging (STI) method in 10 DCM patients (range 0.6-15 yr, median 6.5 yr, 3 females) and 17 age- and sex-matched normal controls. Global torsion was decreased in DCM (peak global torsion; 10.9 +/- 4.6 degrees vs. 0.3 +/- 2.1 degrees , p<0.001). Loss of LV torsion occurred mainly by the diminution of counterclockwise apical rotation and was augmented by somewhat less reduction in clockwise basal rotation. In DCM, the normal counterclockwise apical rotation was not observed, and the apical rotation about the central axis was clockwise or slightly counterclockwise (peak apical rotation; 5.9 +/- 4.1 degrees vs. -0.9 +/- 3.1 degrees , p<0.001). Systolic counterclockwise Vrot and early diastolic clockwise Vrot at the apical level were decreased or abolished. In DCM, decreased systolic torsion and loss of early diastolic recoil contribute to LV systolic and diastolic dysfunction. The STI method may facilitate the serial evaluation of the LV torsional behavior in clinical settings and give new biomechanical concepts for better management of patients with DCM.

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.

Alterations of regional myocardial function in a swine model of myocardial infarction assessed by echocardiographic 2-dimensional strain imaging

BACKGROUND

Tissue Doppler strain and strain rate imaging have been introduced for quantitative assessment of regional myocardial function. These techniques are largely limited to the evaluation of overall longitudinal myocardial function. This study attempted to apply radial strain, circumferential strain, radial displacement, and strain-based torsion analysis to differentiating the infarct, adjacent, and remote zones in a swine model of myocardial infarction.

METHODS

Seven pigs, body weight 24 to 26 kg, were subjected to myocardial infarction by occlusion of the left anterior descending coronary artery (LAD) and followed up for 8 weeks. Regional radial and circumferential deformations were quantified noninvasively by ultrasonic strain rate imaging before LAD occlusion, LAD occlusion immediately, and 4, 6, and 8 weeks after LAD occlusion. Strain-based left ventricular torsion was assessed at the same time points.

RESULTS

Both radial and circumferential strains, and torsion, were decreased significantly in the LAD territory areas as a result of myocardial ischemia and infarction. There were no significant changes in radial and circumferential strains, or torsion, in the areas of adjacent and remote zones over time.

CONCLUSIONS

These findings demonstrate that speckle-tracking strain imaging may be suitable for noninvasive quantification of left ventricular segmental function of ischemic heart disease.

Assessment of left ventricular rotation and torsion with two-dimensional speckle tracking echocardiography

BACKGROUND

Speckle tracking echocardiography (STE) has a unique feature of angle independence and, thus, may provide a powerful means of assessing left ventricular (LV) torsion (LVtor). The aims of this study were to assess: (1) the feasibility of 2-dimensional STE in the measurement of LVtor; and (2) the relationship of LVtor with age and conventional echocardiographic parameters.

METHODS

We consecutively recruited 160 healthy volunteers. After obtaining conventional echocardiographic parameters, apical and basal short-axis rotations were assessed with STE. LVtor was defined as the net difference between rotation angles in the two short-axis planes normalized for LV longitudinal length.

RESULTS

Reliable LVtor measurement was possible only in 56 volunteers (35%). This low feasibility was largely a result of the failure to obtain reliable basal rotation values. In 56 volunteers who were finally enrolled in this study, a significant correlation was found between LV ejection fraction and LVtor (r = 0.56, P < .001) and this correlation was attributed to apical (r = 0.47, P < .001) but not basal (P = .14) rotation. There was no significant change in LVtor with aging. However, initial counterclockwise motion (r = -0.51, P = .001) and its interval (r = -0.44, P = .001) in the basal rotation gradually decreased with aging, and correlated with early transmitral inflow velocity (r = 0.44 and 0.49, respectively) and its deceleration time (r = -0.43 and -0.48, respectively) (all P < .001). In contrast, such correlations were not found for initial clockwise motion and its interval in the apical rotation.

CONCLUSIONS

Currently, STE has limited feasibility in the measurement of LVtor. There was no significant age-related change in LVtor. In LV rotations, basal rotation was affected by the age-related changes in the LV early diastolic filling, whereas apical rotation was mainly related to LV systolic performance.

The Assessment of Left Ventricular Twist in Anterior Wall Myocardial Infarction Using Two-dimensional Speckle Tracking Imaging

BACKGROUND

Two-dimensional speckle tracking imaging allows noninvasive measurement of left ventricular (LV) strain, rotation, and displacement. We investigated whether LV twist would be depressed in anterior wall myocardial infarction (MI) as a result of reduced apical rotation.

METHODS

Basal and apical LV short-axis images were acquired in 30 patients with anterior wall MI. Using commercially available 2-dimensional strain software, time domain speckle tracking was performed, and regional LV strain, rotation, and radial displacement were obtained in each plane. LV twist was defined as apical LV rotation relative to the base. Patients were divided into two groups according to global LV systolic function (normal LV ejection fraction [LVEF] group [LVEF > or = 45%, n = 16] and abnormal LVEF group [LVEF < 45%, n = 14]).

RESULTS

Circumferential strain in the apex was significantly reduced in abnormal LVEF group compared with normal LVEF group (-7.3 +/- 2.6 vs -13.5 +/- 4.1, P < .001). Peak LV twist was significantly reduced in abnormal LVEF group (5.6 +/- 2.6 vs 9.8 +/- 4.0 degrees, P < .005) mainly because of reduced apical rotation. Peak positive and negative twist velocity was also significantly depressed (38.8 +/- 11.3 vs 52.1 +/- 19.3 degree/s, P < .05, and -42.6 +/- 17.8 vs -63.4 +/- 28.0 degree/s, P < .05, respectively). Significant correlation was noted between peak twist and LVEF (r = 0.73, P < .001) and LV end-systolic volume (r = 0.56, P < .001). The twist-displacement loop was markedly distorted in abnormal LVEF group.

CONCLUSIONS

Systolic twist was decreased and diastolic untwisting was depressed in accordance with LV systolic dysfunction in anterior wall MI. These results suggest the significant impact of global LV systolic function on LV twist and twist-displacement loops in patients with anterior wall MI.

Effect of aging on twist-displacement loop by 2-dimensional speckle tracking imaging

BACKGROUND

Newly developed 2-dimensional (2D) speckle tracking imaging provides simultaneous information on both cardiac rotation and radial displacement throughout the cardiac cycle, thus, providing the opportunity to noninvasively construct twist-displacement loops. The aim of this study was to examine the effect of aging on twist-displacement loops.

METHODS

Basal and apical 2D left ventricular (LV) short-axis images with high frame rates were acquired in 59 asymptomatic healthy volunteers. Using commercially available software, LV rotation and radial displacement were obtained at each plane by 2D speckle tracking analysis. LV twist was defined as apical LV rotation relative to the base. To adjust intersubject differences in heart rate, the time sequence was normalized to the percentage of systolic and diastolic duration. Volunteers were divided into 3 groups according to age.

RESULTS

Twist-displacement loops were characterized by a figure of 8 configuration. There was a linear relation between twist and displacement during systole (r = 0.97), with its slope being significantly larger in the older group compared with the young group. During early diastole, a substantial degree of untwisting developed despite a relatively small reversal of systolic radial displacement, resulting in a much steeper twist-displacement relationship observed in all groups. Subsequent diastolic expansion occurred with more gradual additional untwisting.

CONCLUSION

We found that 2D speckle tracking imaging successfully provides twist-displacement loop, noninvasively. Aging affects the systolic component of the twist-displacement loop. The assessment of twist-displacement loop may be useful for evaluating LV function.

Age-related changes in left ventricular twist assessed by two-dimensional speckle-tracking imaging

The aim of this study was to determine the normal value of left ventricular (LV) twist, and to examine the effects of aging on LV twist by newly developed 2-dimensional ultrasound speckle-tracking imaging. We acquired basal and apical LV short-axis second harmonic images in 118 healthy volunteers. Using commercially available 2-dimensional strain software, time-domain speckle tracking was performed, and mean value of LV rotation obtained at each plane. LV twist was defined as apical rotation relative to the base. Adequate data were obtained in 113 volunteers. During systole, the LV performs a wringing motion with a counterclockwise rotation at the apex and a clockwise rotation at the base. The mean value of peak twist was 7.7 +/- 3.5 degrees. Immediately after end systole, rapid untwisting develops. Different LV twist profiles are noted according to age. Peak LV twist was significantly higher, and the rate of LV untwisting significantly reduced and delayed, with advancing age. LV twist can be measured noninvasively by 2-dimensional ultrasound speckle-tracking imaging. The observed reduced and delayed diastolic untwisting with aging may contribute toward the tendency of diastolic dysfunction. This novel method allows the detailed study of diastolic function in various cardiovascular diseases.

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.