Does left ventricular shape influence clinical outcome in heart failure?

Mitral regurgitation increases systolic strains in remote zone and worsens left ventricular dyssynchrony in a swine model of ischemic cardiomyopathy

Background

Ischemic mitral regurgitation (IMR) imposes volume overload on the left ventricle (LV), accelerating adverse LV remodeling. In this study, we sought to investigate the impact of volume overload due to IMR on regional myocardial contractile mechanics.

Methods

Ten Yorkshire swine were induced with myocardial infarction (MI) by occluding the left circumflex coronary artery (LCx). Cardiac MRI was performed at baseline (BL) and 2.5 months (2.5M) post-MI. IMR was quantified with epicardial echocardiography 3 months post-MI. The animals were then assigned to 2 groups: no/mild MR (nmMR, n = 4) and moderate/severe MR (msMR, n = 6). MRI images were analyzed to assess infarction size, end-diastolic and end-systolic volume (EDV and ESV, respectively), ejection fraction (EF), longitudinal strain (LS), circumferential strain (CS), and systolic dyssynchrony index (SDI). The myocardial region was divided into infarction, border, and remote zones based on the LCx-supplied region.

Results

There was no difference in the infarction size. Group-wise comparison of LS and CS between BL and 2.5M demonstrated that LS and CS in the infarction zone and the border zone decreased at 2.5M in both groups. However, LS and CS in the remote zone were elevated only in the msMR group (LS: -9.81 ± 3.96 vs. -12.58 ± 5.07, p < 0.01; CS; -12.78 ± 3.81 vs. -16.09 ± 3.33, p < 0.01) at 2.5M compared to BL. The SDI of CS was significantly elevated in the msMR group (0.1255 vs. 0.0974, p = 0.015) at 2.5M compared to BL.

Conclusions

Elevated LS and CS in the remote zone were observed in moderate/severe MR and ventricular dyssynchrony. These elevated cardiac strains, coupled with ventricular dyssynchrony, may contribute to the progression of MR, thereby accelerating heart failure.

Analysing functional implications of differences in left ventricular morphology using statistical shape modelling

Functional implications of left ventricular (LV) morphological characterization in congenital heart disease are not widely explored. This study qualitatively and quantitatively assessed LV shape associations with a) LV function and b) thoracic aortic morphology in patients with aortic coarctation (CoA) with/without bicuspid aortic valve (BAV), and healthy controls. A statistical shape modelling framework was employed to analyse three-dimensional (3D) LV shapes from cardiac magnetic resonance (CMR) data in isolated CoA (n = 25), CoA + BAV (n = 30), isolated BAV (n = 30), and healthy controls (n = 25). Average 3D templates and deformations were computed. Correlations between shape data and CMR-derived morphometric parameters (i.e., sphericity, conicity) or global and apical strain values were assessed to elucidate possible functional implications. The relationship between LV shape features and arch architecture was also explored. The LV template was shorter and more spherical in CoA patients. Sphericity was overall associated with global and apical radial (p = 0.001, R² = 0.09; p < 0.0001, R² = 0.17) and circumferential strain (p = 0.001, R² = 0.10; p = 0.04, R² = 0.04), irrespective of the presence of aortic stenosis and/or regurgitation and controlling for age and hypertension status. LV strain was not associated with arch architecture. Differences in LV morphology were observed between CoA and BAV patients. Increasing LV sphericity was associated with reduced strain, independent of aortic arch architecture and functional aortic valve disease.

Ventricular reshaping with a beating heart implant improves pump function in experimental heart failure

OBJECTIVE

The left ventricle remodels from an ellipsoidal/conical shape to a spherical shape after a myocardial infarction. The spherical ventricle is inefficient as a pumping chamber, has higher wall stresses, and can lead to congestive heart failure. We sought to investigate if restoring physiological ventricular shape with a beating heart implant improves pump function.

METHODS

Rats were induced with a myocardial infarction, developing left ventricular dilatation and dysfunction, and becoming spherical over 3 weeks. Thereafter, they were randomized to undergo left ventricular reshaping with a beating heart implant (n = 19) or continue follow-up without an implant (n = 19). Biweekly echocardiography was performed until 12 weeks, with half the rats euthanized at 6 weeks and remaining at 12 weeks. At termination, invasive hemodynamic parameters and histopathology were performed.

RESULTS

At 3 weeks after the infarction, rats had a 22% fall in ejection fraction, 31% rise in end diastolic volume, and 23% rise in sphericity. Transventricular implant reshaping reduced the volume by 12.6% and sphericity by 21%, restoring physiologic ventricular shape and wall stress. Over the 12-week follow-up, pump function improved significantly with better ventricular-vascular coupling in the reshaped hearts. In this group, cardiomyocyte cross-section area was higher and the cells were less elongated.

CONCLUSIONS

Reshaping a postinfarction, failing left ventricle to restore its physiological conical shape significantly improves long-term pump function.

Basic and advanced echocardiography in advanced heart failure: an overview

Advanced chronic heart failure (ACHF) is the last phase in the evolution of heart failure and is characterized by high hospitalization and mortality rates and is refractory to medical therapy, therefore requiring more aggressive therapies, such as mechanical circulatory support or heart transplantation. Over the last years, the incidence of ACHF was continuously growing, together with the increase in population survival rates. Therefore, the early recognition of the transition to ACHF is of crucial importance in HF patients, which also helps in prognostication of such patients, since advanced therapeutic options are limited to selected patients and they also have some important risk implications. Echocardiography is the gold standard tool for the evaluation of patients with HF; moreover, the recent technological advances provided new structural and functional indices of the four cardiac chambers that showed to be comparable to advanced imaging or invasive hemodynamic parameters. This allows us to operate an accurate study of ACHF with first- and second-level echocardiographic techniques, which are now being integrated in daily clinical practice. The present review presents an overview of the currently available tools for the echocardiographic examination of patients with ACHF, with its advantages and limitations, based on the latest supporting evidences.

Prognostic Value of Echocardiographic Right Ventricular Function Parameters in the Presence of Severe Tricuspid Regurgitation

Background: Presence of severe tricuspid regurgitation (TR) has a significant impact on assessment of right ventricular function (RVF) in transthoracic echocardiography (TTE). High trans-valvular pendulous volume leads to backward-unloading of the right ventricle. Consequently, established cut-offs for normal systolic performance may overestimate true systolic RVF. Methods: A retrospective analysis was performed entailing all patients who underwent TTE at our institution between 1 January 2013 and 31 December 2016. Only patients with normal left ventricular systolic function and with no other valvular lesion were included. All recorded loops were re-read by one experienced examiner. Patients without severe TR (defined as vena contracta width ≥7 mm) were excluded. All-cause 2-year mortality was chosen as the end-point. The prognostic value of several RVF parameters was tested. Results: The final cohort consisted of 220 patients, 88/220 (40%) were male. Median age was 69 years (IQR 52–79), all-cause two-year mortality was 29%, median TAPSE was 19 mm (15–22) and median FAC was 42% (30–52). In multivariate analysis, TAPSE with the cutoff 17 mm and FAC with the cutoff 35% revealed non-significant hazard ratios (HR) of 0.75 (95%CI 0.396–1.421, p = 0.38) and 0.845 (95%CI 0.383–1.867, p = 0.68), respectively. TAPSE with the cutoff 19 mm and visual eyeballing significantly predicted survival with HRs of 0.512 (95%CI 0.296–0.886, p = 0.017) and 1.631 (95%CI 1.101–2.416, p = 0.015), respectively. Conclusions: This large-scale all-comer study confirms that RVF is one of the main drivers of mortality in patients with severe isolated TR. However, the current cut-offs for established echocardiographic parameters did not predict survival. Further studies should investigate the prognostic value of higher thresholds for RVF parameters in these patients.

Ventricular remodeling in preterm infants: computational cardiac magnetic resonance atlasing shows significant early remodeling of the left ventricle

BACKGROUND

Premature birth is associated with ventricular remodeling, early heart failure, and altered left ventricular (LV) response to physiological stress. Using computational cardiac magnetic resonance (CMR) imaging, we aimed to quantify preterm ventricular remodeling in the neonatal period, and explore contributory clinical factors.

METHODS

Seventy-three CMR scans (34 preterm infants, 10 term controls) were performed to assess in-utero development and preterm ex-utero growth. End-diastolic computational atlases were created for both cardiac ventricles; t statistics, linear regression modeling, and principal component analysis (PCA) were used to describe the impact of prematurity and perinatal factors on ventricular volumetrics, ventricular geometry, myocardial mass, and wall thickness.

RESULTS

All preterm neonates demonstrated greater weight-indexed LV mass and higher weight-indexed end-diastolic volume at term-corrected age (P < 0.05 for all preterm gestations). Independent associations of increased term-corrected age LV myocardial wall thickness were (false discovery rate <0.05): degree of prematurity, antenatal glucocorticoid administration, and requirement for >48 h postnatal respiratory support. PCA of LV geometry showed statistical differences between all preterm infants at term-corrected age and term controls.

CONCLUSIONS

Computational CMR demonstrates that significant LV remodeling occurs soon after preterm delivery and is associated with definable clinical situations. This suggests that neonatal interventions could reduce long-term cardiac dysfunction.

Ultrasonic sensor concept to fit a ventricular assist device cannula evaluated using geometrically accurate heart phantoms

Future left ventricular assist devices (LVADs) are expected to respond to the physiologic need of patients; however, they still lack reliable pressure or volume sensors for feedback control. In the clinic, echocardiography systems are routinely used to measure left ventricular (LV) volume. Until now, echocardiography in this form was never integrated in LVADs due to its computational complexity. The aim of this study was to demonstrate the applicability of a simplified ultrasonic sensor to fit an LVAD cannula and to show the achievable accuracy in vitro. Our approach requires only two ultrasonic transducers because we estimated the LV volume with the LV end-diastolic diameter commonly used in clinical assessments. In order to optimize the accuracy, we assessed the optimal design parameters considering over 50 orientations of the two ultrasonic transducers. A test bench was equipped with five talcum-infused silicone heart phantoms, in which the intra-ventricular surface replicated papillary muscles and trabeculae carnae. The end-diastolic LV filling volumes of the five heart phantoms ranged from 180 to 480 mL. This reference volume was altered by ±40 mL with a syringe pump. Based on the calibrated measurements acquired by the two ultrasonic transducers, the LV volume was estimated well. However, the accuracies obtained are strongly dependent on the choice of the design parameters. Orientations toward the septum perform better, as they interfere less with the papillary muscles. The optimized design is valid for all hearts. Considering this, the Bland-Altman analysis reports the LV volume accuracy as a bias of ±10% and limits of agreement of 0%-40% in all but the smallest heart. The simplicity of traditional echocardiography systems was reduced by two orders of magnitude in technical complexity, while achieving a comparable accuracy to 2D echocardiography requiring a calibration of absolute volume only. Hence, our approach exploits the established benefits of echocardiography and makes them applicable as an LV volume sensor for LVADs.

Role of Myocardial Perfusion Study in Differentiating Ischemic versus Nonischemic Cardiomyopathy Using Quantitative Parameters

PURPOSE

Ischemic cardiomyopathy (ICM) and non-ICM (NICM) causes of dilated cardiomyopathy with similar clinical presentation have different management and prognosis. This study employed myocardial perfusion imaging (MPI) to differentiate between the two using quantitative parameters in Indian population.

METHODS AND MATERIALS

Fifty patients prospectively underwent MPI and ¹⁸F-fluorodeoxyglucose metabolism studies. P values (0.05 as significant) were calculated for the left ventricular ejection fraction (EF), end diastolic volume (EDV) at rest and stress, end systolic volume (ESV) at rest and stress, summed rest score (SRS), summed difference score (SDS), and eccentricity. On 6-month follow-up, rate of hospital admission, change in management and death was correlated for ICM and NICM. Coronary angiography (CAG) being gold standard, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and level of agreement were calculated for MPI.

RESULTS

MPI and CAG had a moderate level of agreement (κ = 0.463) for differentiating ICM and NICM. The sensitivity, specificity, PPV, NPV, and diagnostic accuracy were 79.31%, 66.67%, 76.67%, 70.0%, and 74% for ICM and 66.67%, 79.31%, 70%, 76.67%, and 74% for NICM, respectively. Significant differences were seen in EDV stress (P = 0.045), EDV rest (P = 0.031), ESV rest (P = 0.034), SRS (P = 0.004), Left ventricular EF rest (P = 0.049) and SDS in ICM and NICM, respectively.

CONCLUSION

EDV at rest and stress, ESV at rest, SRS, SDS, and EF at rest obtained using MPI provides precise quantitative information to differentiate ICM and NICM. It is wide and easy availability, noninvasiveness, objectivity, and near absence of complications favors it as a preferable diagnostic tool with its given sensitivity, specificity, and accuracy for the purpose.

Three-dimensional analysis of interventricular septal curvature from cardiac magnetic resonance images for the evaluation of patients with pulmonary hypertension

Although abnormal septal motion is a well-known sign of increased pulmonary arterial pressures, it is not routinely used to quantify the severity of pulmonary hypertension (PH). This determination relies on invasive measurements or Doppler echocardiographic estimation of right ventricular (RV) pressures, which is not always feasible or accurate in patients with PH. We hypothesized that dynamic 3D analysis of septal curvature from cardiac magnetic resonance (CMR) images may reveal differences between patients with different degrees of PH. Forty-four patients (14 controls; 30 PH patients who underwent right heart catheterization) were studied using CMR and echocardiography. CMR imaging was performed using Philips 1.5T scanner with a phased-array cardiac coil, in a retrospectively gated steady-state free precession cine mode at 30 frames per cardiac cycle. Patients were divided into 3 subgroups according to pulmonary arterial pressure. CMR images were used to reconstruct dynamic 3D left ventricular endocardial surfaces, which were analyzed to calculate septal curvature throughout the cardiac cycle. 3D curvature analysis was feasible in 88% patients. Septal curvature showed different temporal patterns in different groups. Curvature values progressively decreased with increasing severity of PH, and correlated well with invasive pressures (r-values 0.78-0.79), pulmonary vascular resistance (r = 0.83) and Doppler-derived RV peak-systolic pressure (r = 0.75). 3D analysis of septal curvature from CMR images may become a useful component in the CMR examination in patients with known or suspected PH.

Feasibility of regional and global left ventricular shape analysis from real-time 3d echocardiography

Combined assessment of left ventricular (LV) shape and function could provide new insights into the process of LV remodeling. Real-time 3D echocardiography (RT3DE) allows rapid and accurate semi-automated extraction of LV endocardial surfaces. Our aims were to quantify LV morphology both globally and regionally, using new ellipsoidal (E), spherical (S) and conical (C) shape indices, in a large population in order to define normal values. During systole the LV became less spherical and more conical, while E index remained unchanged. LV volume estimation was more affected by operator subjectivity than C and S indexes computation. These results constitute a reference for future comparisons with serial follow-up of patients during LV remodeling.

Feasibility of left ventricular shape analysis from transthoracic real-time 3-D echocardiographic images

Despite the potential ability of left ventricular (LV) shape analysis to provide independent information complementary to ventricular size and function, in clinical practice only ejection fraction (EF) is currently assessed while LV shape is not routinely quantified. Moreover, geometric assumptions in the computation of EF from multiple two-dimensional (2-D) cut-planes by disc summation or area-length methods, introduce inaccuracies in the estimates. Also, previous approaches for the quantification of LV shape were based on geometric modeling and, as a result, proved inaccurate. Our aims were (1) to develop and test a three-dimensional (3-D) technique for direct quantification of LV shape from real-time 3-D echocardiographic (RT3DE) images without the need for geometric modeling using a new class of LV shape indices; and (2) to study the relationship between these indices and ventricular size and function in normal and abnormal ventricles. Spherical (S), ellipsoidal (E) and conical (C) shape indices were calculated using custom software for analysis of transthoracic RT3DE images on both global and regional levels and initially tested on computer simulated objects of different shapes. The feasibility of using these indices to differentiate between normal and abnormal ventricles was tested in three groups of patients: normal volunteers (NL, n=9), dilated cardiomyopathy (DCM, n=9) and coronary artery disease with apical regional wall motion abnormalities (RWMA, n=9). Computer simulation demonstrated that these shape indices are size-independent and can correctly classify the simulated objects. In human ventricles, both S and C but not E correlated well with LV volumes and EF. Also, S and C changed throughout the cardiac cycle while E remained almost constant. In addition, both regional and global S and C were able to identify differences between NL and abnormal ventricles: normal ventricles were less spherical and more conical than those of patients with DCM at both end-systole and end-diastole (p<0.05) both globally and regionally. In contrast, in patients with RWMA, similar differences were noted only at end-systole, both on a global level and in the apical region. In this study, we demonstrated the feasibility of quantifying LV shape from transthoracic RT3DE images at both global and regional levels. Potentially, such 3-D shape analysis could be combined with conventional evaluation of LV volume and function to provide a more comprehensive assessment of left ventricular performance.

A curvature-based approach for left ventricular shape analysis from cardiac magnetic resonance imaging

It is believed that left ventricular (LV) regional shape is indicative of LV regional function, and cardiac pathologies are often associated with regional alterations in ventricular shape. In this article, we present a set of procedures for evaluating regional LV surface shape from anatomically accurate models reconstructed from cardiac magnetic resonance (MR) images. LV surface curvatures are computed using local surface fitting method, which enables us to assess regional LV shape and its variation. Comparisons are made between normal and diseased hearts. It is illustrated that LV surface curvatures at different regions of the normal heart are higher than those of the diseased heart. Also, the normal heart experiences a larger change in regional curvedness during contraction than the diseased heart. It is believed that with a wide range of dataset being evaluated, this approach will provide a new and efficient way of quantifying LV regional function.