Midwall Shortening After Coarctation Repair: The Effect of Through-plane Motion on Single-plane Indices of Left Ventricular Function

4D modelling for rapid assessment of biventricular function in congenital heart disease

Although more patients with congenital heart disease (CHD) are now living longer due to better surgical interventions, they require regular imaging to monitor cardiac performance. There is a need for robust clinical tools which can accurately assess cardiac function of both the left and right ventricles in these patients. We have developed methods to rapidly quantify 4D (3D + time) biventricular function from standard cardiac MRI examinations. A finite element model was interactively customized to patient images using guide-point modelling. Computational efficiency and ability to model large deformations was improved by predicting cardiac motion for the left ventricle and epicardium with a polar model. In addition, large deformations through the cycle were more accurately modeled using a Cartesian deformation penalty term. The model was fitted to user-defined guide points and image feature tracking displacements throughout the cardiac cycle. We tested the methods in 60 cases comprising a variety of congenital heart diseases and showed good correlation with the gold standard manual analysis, with acceptable inter-observer error. The algorithm was considerably faster than standard analysis and shows promise as a clinical tool for patients with CHD.

An interactive tool for rapid biventricular analysis of congenital heart disease

Cardiac malformations are the most common birth defect. Better interventions in early life have improved mortality for children with congenital heart disease, but heart failure is a significant problem in adulthood. These patients require regular imaging and analysis of biventricular (left and right ventricular) function. In this study, we describe a rapid method to analyse left and right ventricular shape and function from cardiac MRI examinations. A 4D (3D+time) finite element model template is interactively customized to the anatomy and motion of the biventricular unit. The method was validated in 17 patients and 10 ex-vivo hearts. Interactive model updates were achieved through preconditioned conjugate gradient optimization on a multithread system, and by precomputing points predicted from a coarse mesh optimization.

Insights from Cardiac Mechanics after Three Decades from Successfully Repaired Aortic Coarctation

BACKGROUND AND AIMS

Patients who underwent a successful repair of the aortic coarctation show chronic hyperdynamic state and normal left ventricular (LV) geometry; however, there are few data regarding the LV systolic function in the long term. Accordingly, we assessed LV systolic mechanics and factors associated with LV systolic dysfunction (LVSD) in patients with repaired CoA.

METHODS

Clinical and echocardiographic data from 19 repaired CoA were analyzed 28 ± 13 years after surgery. Stress-corrected midwall shortening (sc-MS) and mitral annular peak systolic velocity (S') were analyzed as indexes of LV circumferential and longitudinal systolic function, respectively. Echocardiographic data of CoA patients were compared with 19 patients matched for age and hypertension and 38 healthy controls. Sc-MS was considered impaired if <89%, S' if <8.5 cm/s (10th percentiles of healthy controls, respectively).

RESULTS

There were no statistical differences between study groups in LV volumes, mass and geometry. LV ejection fraction and Sc-MS were similar in all groups, however, CoA group had a significantly lower peak S' in comparison with matched and healthy controls (7.1 ± 1.3, 10.3 ± 1.9, and 11.1 ± 1.5, respectively; all P < 0.001). Prevalence of longitudinal LVSD defined as low S' was 84% in CoA, 13% in matched, and 5% in healthy control group (all P<0.05). Multivariate logistic regression analysis revealed that low peak S' was independently related to higher E/E' ratio and the presence of CoA.

CONCLUSIONS

Patients who underwent a successful repair of CoA commonly show asymptomatic longitudinal LVSD associated with worse LV diastolic function in the long-term follow-up.

Left ventricular contractile reserve in young adults long-term after repair of coarctation of the aorta

We assessed the left ventricular (LV) contractile reserve in young adults with repaired coarctation of the aorta and interrupted aortic arch by determination of LV force-frequency relation (FFR). Eighteen (7 men) patients aged 24.2 ± 5.4 years and 20 (9 men) healthy controls were studied. Blood pressures in the right arm were measured by oscillometry. Transmitral early (E) and late (A) diastolic velocities, tissue Doppler-derived mitral annular systolic (sm), early diastolic (em) and late diastolic (am) velocities, and myocardial isovolumic acceleration (IVA) were measured. The LV FFR and average slope were derived from the IVA measured at different heart rates during supine bicycle exercise. Blood pressures at rest were similar between patients and controls (all p >0.05). At baseline, patients compared with controls had significantly greater E velocity, E/A and E/em ratios, and lower sm and em velocities (all p <0.05) but similar IVA (p = 0.18). At submaximal exercise, diastolic (p = 0.001) and mean (p = 0.003) blood pressures became significantly higher in patients than controls, sm (p = 0.001) and em (p <0.001) velocities remained reduced, whereas the IVA became lower (p <0.001). The weighted average FFR was flattened (p <0.001), and average FFR slope was lower (p <0.001) in patients compared with controls. The average FFR slope correlated negatively with the magnitude of exercise-induced increase in systolic (r = -0.32, p = 0.050), mean (r = -0.41, p = 0.011), and diastolic (r = -0.40, p = 0.013) blood pressures. In conclusion, young adults after coarctation of the aorta and interrupted aortic arch repair exhibit reduced LV contractile reserve, which is related to the blood pressure response during exercise stress.

Assessment and comparison of left ventricular shear in normal and situs inversus totalis hearts by means of magnetic resonance tagging

Situs inversus totalis (SIT) is characterized by complete mirroring of gross cardiac anatomy and position combined with an incompletely mirrored myofiber arrangement, being normal at the apex but inverted at the base of the left ventricle (LV). This study relates myocardial structure to mechanical function by analyzing and comparing myocardial deformation patterns of normal and SIT subjects, focusing especially on circumferential-radial shear. In nine control and nine SIT normotensive human subjects, myocardial deformation was assessed from magnetic resonance tagging (MRT) image sequences of five LV short-axis slices. During ejection, no significant difference in either circumferential shortening (εcc) or its axial gradient (Δεcc) is found between corresponding LV levels in control and SIT hearts. Circumferential-radial shear (εcr) has a clear linear trend from apex-to-base in controls, while in SIT it hovers close to zero at all levels. Torsion as well as axial change in εcr (Δεcr) is as in controls in apical sections of SIT hearts but deviates significantly towards the base, changing sign close to the LV equator. Interindividual variability in torsion and Δεcr values is higher in SIT than in controls. Apex-to-base trends of torsion and Δεcr in SIT, changing sign near the LV equator, further substantiate a structural transition in myofiber arrangement close to the LV equator itself. Invariance of εcc and Δεcc patterns between controls and SIT subjects shows that normal LV pump function is achieved in SIT despite partial mirroring of myocardial structure leading to torsional and shear patterns that are far from normality.

Ventricular mechanics in patients with aortic valve disease: longitudinal, radial, and circumferential components

BACKGROUND

Reduced long-axis shortening despite enhanced global function has been reported in aortic stenosis. We sought to improve the understanding of this phenomenon using multi-dimensional strain analysis in conjunction with the evaluation of left ventricular rotation and twist - ventricular torsion - using tissue Doppler techniques.

METHODS

A total of 57 patients with variable severity of aortic stenosis, aortic regurgitation, or mixed aortic valve disease, subdivided into six groups, were studied. Ventricular morphology was assessed using long-axis/short-axis and mass/volume ratios, afterload using end-systolic meridional wall stress, and global performance using ejection fraction. The circumferential and longitudinal strain was measured from two-dimensional images, and left ventricular rotation and twist were estimated as the difference in rotation between the base and apex of the ventricle.

RESULTS

Aortic stenosis was associated with higher mass/volume, ejection fraction, circumferential strain and left ventricular rotation and twist, significantly lower end-systolic wall stress, and a trend towards lower longitudinal strain compared with normal. Myocardial mechanics in aortic regurgitation were normal despite ventricular dilation. Mixed aortic valve disease showed findings similar to aortic stenosis. Left ventricular rotation and twist correlated with midwall circumferential strain (r = 0.62 and p < 0.0001), endocardial circumferential strain (r = 0.61 and p < 0.0001), and end-systolic wall stress (r = 0.48 and p < 0.0001), but not with longitudinal strain (r = 0.18 and p > 0.05).

CONCLUSIONS

Myocardial mechanics are normal in patients with aortic regurgitation, independent of abnormalities in cardiac geometry. Conversely, in aortic stenosis and mixed aortic valve disease, significant alterations in the patterns of fibre shortening are found. The effects of stenosis on cardiac function seem to dominate the effect of ventricular remodelling.

Regional left ventricular myocardial shortening in normotensive patients late after aortic coarctation repair - normal or impaired?

Despite successful repair of aortic coarctation (AoC), changes in the left ventricular (LV) regional myocardial function are reported. The aims of this study were (i) to determine LV regional longitudinal deformation in patients who underwent a repair of AoC, who were normotensive and who had normal LV global function; and (ii) to establish a potential correlation between the degree of residual narrowing in the descending aorta and the extent of LV regional deformation. We studied 22 normotensive patients aged 19-58 y (mean 32.6; SD+/-11.3). Maximal strain, epsilon (%), as well as peak systolic and early and late diastolic strain rates (SRs; s(-1)), were obtained on the basis of speckle tracking. The data were compared with those obtained from sex and age-matched controls. Regional SRs were significantly reduced for the LV anterior wall during systole and early diastole -1.1 vs. -1.39; 1.41 vs. 1.86 s(-1), respectively; p<0.05. Transaortic maximal and mean gradients across the coarctation site correlated with epsilon and systolic SR obtained from the midsegment of the LV anterior wall. Despite a successful repair, absence of systemic hypertension and normal global LV function, regional deformation properties of the anterior LV wall were impaired. The degree of longitudinal impairment in this anatomical region correlated with the extent of residual narrowing.

Inappropriate left ventricular mass in children and young adults with chronic renal insufficiency

Increased left ventricular (LV) mass (M) in children with chronic renal insufficiency (CRI) might represent an adaptive mechanism to compensate for increased workload. We hypothesized that in children with CRI, pre-dialysis, values of left ventricular mass (LVM) exceed compensatory values for individual cardiac load. Complete anthropometric characteristics, biochemical profile and echocardiograms were obtained for 33 children with CRI, pre-dialysis (age 1-23 years, mean 12.2 +/- 5.0 years), and 33 age- and gender-matched healthy controls. LV dimensions, wall thicknesses and volume were measured. Endocardial and midwall shortening, ejection fraction, LVM, LVM index, relative wall thickness, circumferential wall stress and excess LVM (as ratio of observed LVM to value predicted from body size, gender and cardiac workload) were analysed. Patients with CRI showed higher values of LVM index, resulting in higher prevalence of LV hypertrophy (36.3% vs 9%, P < 0.05). The ratio of excess LVM was greater in patients with CRI than in healthy controls (126 +/- 19% and 103 +/- 13%, respectively, P < 0.001). LV ejection fraction, midwall fractional shortening and stress-corrected midwall shortening were lower in patients with CRI than in controls. We concluded that, in children with CRI, the values of LVM are higher than those needed to sustain individual cardiac load than in healthy controls, a condition associated with LV hypertrophy and reduced systolic performance.

Abnormal regional myocardial deformation properties and increased aortic stiffness in normotensive patients with aortic coarctation despite successful correction: an ABPM, standard echocardiography and strain rate imaging study

The long-term follow-up data subsequent to a successful repair of AoC (aortic coarctation) show that life expectancy remains reduced. Previous standard echocardiographic studies have demonstrated normal or increased systolic cardiac function in patients following successful repair of AoC. SR (strain rate) imaging is a new technique able to detect subclinical myocardial abnormalities. In the present study we investigated whether young patients (without hypertension, as assessed using ambulatory blood pressure monitoring and an exercise test) following successful AoC repair already have abnormal myocardial deformation properties, and the relationship of the deformation properties with aortic stiffness. We studied 166 subjects, 83 AoC non-hypertensive patients (mean age 12+/-4 years) a number of years after successful repair of AoC and 83 age- and sex-matched subjects as controls. Peak systolic SR (1/s) for both regional longitudinal and radial function was assessed. The aortic stiffness index was calculated from the echocardiographically derived thoracic aortic diameters, and the measurement of blood pressure was obtained by cuff sphygmomanometry. The LV (left ventricular) ejection fraction was significantly increased in AoC patients, whereas regional longitudinal SRs were significantly reduced (-1.1+/-0.9 compared with -2+/-0.5, P<0.0001) in patients. The aortic stiffness index was significantly increased in AoC patients (12+/-9, P<0.0001). At multilinear regression analysis, age at repair (P=0.005; coefficient, -0.201; S.E.M., 0.027) and the aortic stiffness index (P=0.0029; coefficient, 0.334; S.E.M., 0.423) predicted longitudinal SR. Despite the presence of a successful repair for AoC, in the absence of hypertension, longitudinal deformation properties were significantly impaired. Moreover, the degree of longitudinal SR impairment was correlated with age at repair and aortic stiffness. Early repair can delay the onset of hypertension in postcoarctectomy patients, but cannot prevent the innate structural and functional abnormalities of the aorta and their deleterious effect on myocardial deformation properties.