Left ventricular remodeling and mechanics after successful repair of aortic coarctation

Coarctation duration and severity predict risk of hypertension precursors in a preclinical model and hypertensive status among patients

Background

Coarctation of the aorta (CoA) often leads to hypertension (HTN) post-treatment. Evidence is lacking for the current >20 mmHg peak-to-peak blood pressure gradient (BPGpp) guideline, which can cause aortic thickening, stiffening and dysfunction. This study sought to find the BPGpp severity and duration that avoid persistent dysfunction in a preclinical model, and test if predictors translate to HTN status in CoA patients.

Methods

Rabbits (N=75; 5-12/group) were exposed to mild, intermediate or severe CoA (≤12, 13-19, ≥20 mmHg BPGpp) for ~1, 3 or 22 weeks using dissolvable and permanent sutures with thickening, stiffening, contraction and endothelial function evaluated via multivariate regression. Relevance to CoA patients (N=239; age=0.01-46 years; median 3.7 months) was tested by retrospective review of predictors (preoperative BPGpp, surgical age, etc.) vs follow-up HTN status.

Results

CoA duration and severity were predictive of aortic remodeling and active dysfunction in rabbits, and HTN in CoA patients. Interaction between patient age and BPGpp at surgery contributed significantly to HTN, similar to rabbits, suggesting preclinical findings translate to patients. Machine learning decision tree analysis uncovered that pre-operative BPGpp and surgical age predict risk of HTN along with residual post-operative BPGpp.

Conclusions

These findings suggest the current BPGpp threshold determined decades ago is likely too high to prevent adverse coarctation-induced aortic remodeling. The results and decision tree analysis provide a foundation for revising CoA treatment guidelines considering the interaction between CoA severity and duration to limit the risk of HTN.

Antihypertensive therapy of late arterial hypertension in children following successful coarctation correction

BACKGROUNG

Late arterial hypertension (AH) is the most significant complication of coarctation of the aorta (CoA). Only a few clinical studies described antihypertensive treatment of late AH following successful CoA repair. The primary objective of this multicentre cross-sectional study was to describe real-life antihypertensive therapy for late AH in children after hemodynamically successful CoA repair. The secondary objective was to describe antihypertensive therapy used within different haemodynamic phenotypes of AH.

METHOD

Blood pressure status, echocardiographic parameters and central blood pressure measurements were evaluated in 110 children aged 6-18 years following successful CoA repair with right arm blood pressure not exceeding leg blood pressure by at least 20 mmHg.

RESULTS

AH was found in 62 (56%) patients including 47 who were already treated and 15 with new diagnosed AH of whom seven presented with masked hypertension. Among treated patients, 10 presented with masked hypertension. The dominant phenotype of AH among patients with uncontrolled AH was isolated systolic hypertension (32 patients out of 37; 87.5%). AH was controlled in 53% of treated patients. Fifty-three percent of hypertensive patients had elevated central SBP and 39% had left ventricular hypertrophy with various left ventricle geometry patterns, 23% of them had both. β-adrenergic receptor blockers were the most used antihypertensive drugs followed by angiotensin-converting enzyme inhibitors with doses within the lower recommended range.

CONCLUSION

High prevalence of uncontrolled AH despite successful CoA repair and use of relatively low doses of antihypertensive drugs indicates the need of close blood pressure monitoring and more intensive and combined antihypertensive therapy.

Prognostic Model to Predict Postoperative Adverse Events in Pediatric Patients With Aortic Coarctation

Background: Postoperative adverse events remain excessively high in surgical patients with coarctation of aorta (CoA). Currently, there is no generally accepted strategy to predict these patients' individual outcomes.

Objective: This study aimed to develop a risk model for the prediction of postoperative risk in pediatric patients with CoA.

Methods: In total, 514 patients with CoA at two centers were enrolled. Using daily clinical practice data, we developed a model to predict 30-day or in-hospital adverse events after the operation. The least absolute shrinkage and selection operator approach was applied to select predictor variables and logistic regression was used to develop the model. Model performance was estimated using the receiver-operating characteristic curve, the Hosmer–Lemeshow test and the calibration plot. Net reclassification improvement (NRI) and integrated discrimination improvement (IDI) compared with existing risk strategies were assessed.

Results: Postoperative adverse events occurred in 195 (37.9%) patients in the overall population. Nine predictive variables were identified, including incision of left thoracotomy, preoperative ventilation, concomitant ventricular septal defect, preoperative cardiac dysfunction, severe pulmonary hypertension, height, weight-for-age z-score, left ventricular ejection fraction and left ventricular posterior wall thickness. A multivariable logistic model [area under the curve = 0.8195 (95% CI: 0.7514–0.8876)] with adequate calibration was developed. Model performance was significantly improved compared with the existing Aristotle Basic Complexity (ABC) score (NRI = 47.3%, IDI = 11.5%) and the Risk Adjustment for Congenital Heart Surgery (RACHS-1) (NRI = 75.0%, IDI = 14.9%) in the validation set.

Conclusion: Using daily clinical variables, we generated and validated an easy-to-apply postoperative risk model for patients with CoA. This model exhibited a remarkable improvement over the ABC score and the RACHS-1 method.

Implications of Left Ventricular Dysfunction at Presentation for Infants with Coarctation of the Aorta

Infants with aortic coarctation may present with left ventricular (LV) dysfunction which may complicate the postoperative course and lead to increased healthcare costs. We aimed to define the prevalence of moderate to severe left ventricular (LV) systolic dysfunction, evaluate time to recovery, and compare health care costs. Single-center retrospective cohort study at a tertiary care hospital was conducted. Infants < 6 months old at diagnosis with aortic coarctation were identified using surgical codes for coarctation repair between January 2010 and May 2018. Moderate to severe dysfunction was defined as ejection fraction (EF) < 40%. Of 160 infants studied, 18 (11%) had moderate to severe LV dysfunction at presentation. Compared to those with better LV function, infants with moderate to severe LV dysfunction were older at presentation (12 vs. 6 days, p = 0.004), had more postoperative cardiac intensive care unit (ICU) days (5 vs. 3, p < 0.001), and more ventilator days (3.5 vs. 1, p < 0.001). The median time to normal LV EF (≥ 55%) was 6 days postoperatively (range 1-230 days). Infants presenting with moderate to severe LV dysfunction had higher index hospitalization costs ($90,560 vs. $59,968, p = 0.02), but no difference in cost of medical follow-up for the first year following discharge ($3,078 vs. $2,568, p = 0.46). In the current era, > 10% of infants with coarctation present with moderate to severe LV dysfunction that typically recovers. Those with moderate to severe dysfunction had longer duration of mechanical ventilation and postoperative cardiac ICU stays, likely driving higher costs of index hospitalization.

Sudden death in a dog with aortic coarctation

A previously healthy, one-year-old, intact female Vizsla dog collapsed and experienced cardiopulmonary arrest after a stressful event. Postmortem examination identified juxtaductal aortic coarctation (AoCo) with complex morphology. Located in the isthmus aorta adjacent to the ligamentum arteriosum, the AoCo comprised a shelf-like structure caused by invagination of the aortic wall into the lumen. Just distally, a second region of aortic occlusion resulted from an obstructing aortic membrane that restricted blood flow into the descending aorta through a small, eccentric ostium. Plausibly, the AoCo contributed to high afterload which led to reduction of coronary blood flow, myocardial hypoxia, and sudden death during physical stress. Although AoCo is a well-recognized congenital defect in humans, it has been reported only rarely in animals. The present case details the gross and histologic features of a complex, juxtaductal AoCo in a dog who died suddenly after stress. These morphologic findings may be informative when contemplating diagnosis of this anomaly.

Circulating biomarkers of left ventricular hypertrophy in pediatric coarctation of the aorta

OBJECTIVE

Patients undergoing surgical repair of aortic coarctation have a 50% risk of pathologic left ventricular remodeling (increased left ventricular mass or relative wall thickness). Endothelin 1, ST2, galectin 3, norepinephrine and B-natriuretic peptide are biomarkers that have been associated with pathologic LV change in adult populations but their predictive value following pediatric coarctation repair are not known.

HYPOTHESIS

Biomarker levels at coarctation repair will predict persistent left ventricular remodeling at 1-year follow up.

DESIGN

Prospective, cohort study of 27 patients' age 2 days-12 years with coarctation of the aorta undergoing surgical repair. Echocardiograms were performed preoperation, postoperation, and at 1-year follow-up. Plasma biomarker levels were measured at the peri-operative time points. Association between biomarker concentrations and echocardiographic parameters was assessed.

RESULTS

Neither left ventricular mass index nor relative wall thickness varied from pre-op to post-op. At pre-op, relative wall thickness was elevated in 52% and left ventricular mass index was elevated in 22%; at follow-up, relative wall thickness was elevated in 13% and left ventricular mass index was elevated in 8%. Presence of residual coarctation did not predict left ventricular remodeling (AUC 0.59; P > .05). Multivariable receiver operating characteristic curve combining pre-op ST2 and endothelin 1 demonstrated significant predictive ability for late pathologic left ventricular remodeling (AUC 0.85; P = .02).

CONCLUSIONS

Persistent left ventricular hypertrophy and abnormal relative wall thickness at intermediate-term follow-up was rare compared to previous studies. A model combining pre-op endothelin 1 and ST2 level demonstrated reasonable accuracy at predicting persistent abnormalities in this cohort. Larger studies will be needed to validate this finding and further explore the mechanism of persistent left ventricular remodeling in this population.

Treating a 20 mm Hg gradient alleviates myocardial hypertrophy in experimental aortic coarctation

BACKGROUND

Children with coarctation of the aorta (CoA) can have a hyperdynamic and remodeled left ventricle (LV) from increased afterload. Literature from an experimental model suggests the putative 20 mm Hg blood pressure gradient (BPG) treatment guideline frequently implemented in CoA studies may permit irreversible vascular changes. LV remodeling from pressure overload has been studied, but data are limited following correction and using a clinically representative BPG.

MATERIALS AND METHODS

Rabbits underwent CoA at 10 weeks to induce a 20 mm Hg BPG using permanent or dissolvable suture thereby replicating untreated and corrected CoA, respectively. Cardiac function was evaluated at 32 weeks by magnetic resonance imaging using a spoiled cine GRE sequence (TR/TE/FA 8/2.9/20), 14 × 14-cm FOV, and 3-mm slice thickness. Images (20 frames/cycle) were acquired in 6-8 short axis views from the apex to the mitral valve annulus. LV volume, ejection fraction (EF), and mass were quantified.

RESULTS

LV mass was elevated for CoA (5.2 ± 0.55 g) versus control (3.6 ± 0.16 g) and corrected (4.0 ± 0.44 g) rabbits, resulting in increased LV mass/volume ratio for CoA rabbits. A trend toward increased EF and stroke volume was observed but did not reach significance. Elevated EF by volumetric analysis in CoA rabbits was supported by concomitant increases in total aortic flow by phase-contrast magnetic resonance imaging.

CONCLUSIONS

The indices quantified trended toward a persistent hyperdynamic LV despite correction, but differences were not statistically significant versus control rabbits. These findings suggest the current putative 20 mm Hg BPG for treatment may be reasonable from the LV's perspective.

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.

Gene Expression in Experimental Aortic Coarctation and Repair: Candidate Genes for Therapeutic Intervention?

Coarctation of the aorta (CoA) is a constriction of the proximal descending thoracic aorta and is one of the most common congenital cardiovascular defects. Treatments for CoA improve life expectancy, but morbidity persists, particularly due to the development of chronic hypertension (HTN). Identifying the mechanisms of morbidity is difficult in humans due to confounding variables such as age at repair, follow-up duration, coarctation severity and concurrent anomalies. We previously developed an experimental model that replicates aortic pathology in humans with CoA without these confounding variables, and mimics correction at various times using dissolvable suture. Here we present the most comprehensive description of differentially expressed genes (DEGs) to date from the pathology of CoA, which were obtained using this model. Aortic samples (n=4/group) from the ascending aorta that experiences elevated blood pressure (BP) from induction of CoA, and restoration of normal BP after its correction, were analyzed by gene expression microarray, and enriched genes were converted to human orthologues. 51 DEGs with >6 fold-change (FC) were used to determine enriched Gene Ontology terms, altered pathways, and association with National Library of Medicine Medical Subject Headers (MeSH) IDs for HTN, cardiovascular disease (CVD) and CoA. The results generated 18 pathways, 4 of which (cell cycle, immune system, hemostasis and metabolism) were shared with MeSH ID’s for HTN and CVD, and individual genes were associated with the CoA MeSH ID. A thorough literature search further uncovered association with contractile, cytoskeletal and regulatory proteins related to excitation-contraction coupling and metabolism that may explain the structural and functional changes observed in our experimental model, and ultimately help to unravel the mechanisms responsible for persistent morbidity after treatment for CoA.

Left ventricular diastolic function and characteristics in fetal aortic stenosis

Fetal aortic balloon valvuloplasty (FAV) has shown promise in averting progression of midgestation aortic stenosis (AS) to hypoplastic left heart syndrome in a subset of patients. Patients who achieve biventricular circulation after FAV frequently have left ventricular (LV) diastolic dysfunction (DD). This study evaluates DD in fetuses with AS by comparing echocardiographic indices of LV diastolic function in fetuses underwent FAV (n = 20) with controls (n = 40) and evaluates for LV factors associated with DD in patients with FAV. We also compared pre-FAV and post-FAV DD variables (n = 16). Median gestational age (24 weeks, range 18 to 29 weeks) and fetal heart rate were similar between FAV and controls. Compared with controls, patients with FAV had universally abnormal LV diastolic parameters including fused mitral inflow E and A waves (p = 0.008), higher E velocity (p <0.001), shorter mitral inflow time (p = 0.001), lower LV lateral annulus E' (p <0.001), septal E' (p = 0.003), and higher E/E' (p <0.001) than controls. Patients with FAV had abnormal right ventricular mechanics with higher tricuspid inflow E velocity (p <0.001) and shorter tricuspid inflow time (p = 0.03). Worse LV diastolic function (lower LV E') was associated with higher endocardial fibroelastosis grade (r = 0.74, p <0.001), large LV volume (r = 0.55, p = 0.013), and sphericity (r = 0.58, p = 0.009) and with lower LV pressure by mitral regurgitation jet (r = -0.68, p <0.001). Post-FAV, fewer patients had fused mitral inflow E and A than pre-FAV (p = 0.05) and septal E' was higher (=0.04). In conclusion, fetuses with midgestation AS have evidence of marked DD. Worse DD is associated with larger, more spherical LV, with more extensive endocardial fibroelastosis and lower LV pressure.

Prevalence and long-term predictors of left ventricular hypertrophy, late hypertension, and hypertensive response to exercise after successful aortic coarctation repair

Controversial data exist about the long-term results of aortic coarctation (AC) repair. This study explored the prevalence and predictors of left ventricular (LV) hypertrophy, late hypertension, and hypertensive response to exercise in 48 subjects (age, 15.1 ± 9.7 years) currently followed in the authors' tertiary care hospital after successful AC repair. Data on medical history, clinical examination, rest and exercise echocardiography, and ambulatory blood pressure monitoring were collected. The time from AC repair to follow-up evaluation was 12.9 ± 9.2 years. The prevalence of LV hypertrophy ranged from 23 to 38 %, based on the criteria used to identify LV hypertrophy, and that of concentric geometry was 17 %. One sixth of the patients without residual hypertension experienced late-onset hypertension. One fourth of those who remained normotensive without medication showed a hypertensive response to exercise. Age at AC repair was the strongest independent predictor of LV hypertrophy, defined using indexation either for body surface area (odds ratio [OR], 1.03; p = 0.0090) or for height(2.7) (OR 1.02; p = 0.029), and it was the only predictor of late hypertension (OR 1.06; p = 0.0023) and hypertensive response to exercise (OR 1.09; p = 0.029). The risk of LV hypertrophy was 25 % for repair at the age of 3.4 years but rose to 50 and 75 % for repair at the ages of 5.9 and 8.4 years, respectively. Similar increases were found for the risk of late-onset hypertension and hypertensive response to exercise. A considerable risk of LV hypertrophy, late hypertension, and hypertensive response to exercise exists after successful AC repair. Older age at intervention is the most important predictor of these complications.

Correlation of exercise response in repaired coarctation of the aorta to left ventricular mass and geometry

The role of exercise testing to risk stratify patients with repaired coarctation of the aorta (CoA) is controversial. Concentric left ventricular (LV) hypertrophy, defined as an increase in the LV mass-to-volume ratio (MVR), is associated with a greater incidence of adverse cardiovascular events. The objective of the present study was to determine whether a hypertensive response to exercise (HRE) is associated with increased LVMVR in patients with repaired CoA. Adults with repaired CoA who had a symptom-limited exercise test and cardiac magnetic resonance imaging examination within 2 years were identified. A hypertensive response to exercise was defined as a peak systolic blood pressure >220 mm Hg during a symptom-limited exercise test. The LV mass and volume were measured using cardiac magnetic resonance by an investigator who was unaware of patient status. We included 47 patients (median age 27.3 years, interquartile range 19.8 to 37.3), who had undergone CoA repair at a median age of 4.6 years (interquartile range 0.4 to 15.7). Those with (n = 11) and without (n = 36) HRE did not differ in age, age at repair, body surface area, arm-to-leg systolic blood pressure gradient, gender, or peak oxygen uptake with exercise. Those with a HRE had a greater mean systolic blood pressure at rest (146 ± 18 vs 137 ± 18 mm Hg, p = 0.04) and greater median LVMVR (0.85, interquartile range 0.7 to 1, vs 0.66, interquartile range 0.6 to 0.7; p = 0.04) than those without HRE. Adjusting for systolic blood pressure at rest, age, age at repair, and gender, the relation between HRE and LVMVR remained significant (p = 0.001). In conclusion, HRE was associated with increased LVMVR, even after adjusting for multiple covariates.

A coupled experimental and computational approach to quantify deleterious hemodynamics, vascular alterations, and mechanisms of long-term morbidity in response to aortic coarctation

INTRODUCTION

Coarctation of the aorta (CoA) is associated with morbidity despite treatment. Although mechanisms remain elusive, abnormal hemodynamics and vascular biomechanics are implicated. We present a novel approach that facilitates quantification of coarctation-induced mechanical alterations and their impact on vascular structure and function, without genetic or confounding factors.

METHODS

Rabbits underwent thoracic CoA at 10weeks of age (~9 human years) to induce a 20mmHg blood pressure (BP) gradient using permanent or dissolvable suture thereby replicating untreated and corrected CoA. Computational fluid dynamics (CFD) was performed using imaging and BP data at 32weeks to quantify velocity, strain and wall shear stress (WSS) for comparison to vascular structure and function as revealed by histology and myograph results.

RESULTS

Systolic and mean BP was elevated in CoA compared to corrected and control rabbits leading to vascular thickening, disorganization and endothelial dysfunction proximally and distally. Corrected rabbits had less severe medial thickening, endothelial dysfunction, and stiffening limited to the proximal region despite 12weeks of normal BP (~4 human years) after the suture dissolved. WSS was elevated distally for CoA rabbits, but reduced for corrected rabbits.

DISCUSSION

These findings are consistent with alterations in humans. We are now poised to investigate mechanical contributions to mechanisms of morbidity in CoA using these methods.

Postnatal left ventricular diastolic function after fetal aortic valvuloplasty

Fetal aortic balloon valvuloplasty (FAV) has shown promise in altering in utero progression of aortic stenosis to hypoplastic left heart syndrome. In patients who achieve a biventricular circulation after FAV, left ventricular (LV) compliance may be impaired. Echocardiographic indexes of diastolic function were compared between patients with biventricular circulation after FAV, congenital aortic stenosis (AS), and age-matched controls. In the neonatal period, patients with FAV had similar LV, aortic, and mitral valve dimensions but more evidence of endocardial fibroelastosis than patients with AS. Patients with FAV underwent more postnatal cardiac interventions than patients with AS (p = 0.007). Mitral annular early diastolic tissue velocity (E') was lower in patients with FAV and those with AS and controls in the neonatal period and over follow-up (p <0.001). Septal E' was similar among all 3 groups in the neonatal period. In follow-up patients, with FAV had lower septal E' than patients with AS or controls (p <0.001). Early mitral inflow velocity/E' was higher in patients with FAV as neonates and at follow-up (p <0.001). Mitral inflow pulse-wave Doppler-derived indexes of diastolic function were similar between groups. In conclusion, echocardiographic evidence of LV diastolic dysfunction is common in patients with biventricular circulation after FAV and persists in short-term follow-up. LV diastolic dysfunction in this unique population may have important implications on long-term risk of left atrial and subsequent pulmonary hypertension.

Bicuspid aortic valve disease

Bicuspid aortic valve (BAV) disease is the most common congenital cardiac defect. While the BAV can be found in isolation, it is often associated with other congenital cardiac lesions. The most frequent associated finding is dilation of the proximal ascending aorta secondary to abnormalities of the aortic media. Changes in the aortic media are present independent of whether the valve is functionally normal, stenotic, or incompetent. Although symptoms often manifest in adulthood, there is a wide spectrum of presentations ranging from severe disease detected in utero to asymptomatic disease in old age. Complications can include aortic valve stenosis or incompetence, endocarditis, aortic aneurysm formation, and aortic dissection. Despite the potential complications, 2 large contemporary series have demonstrated that life expectancy in adults with BAV disease is not shortened when compared with the general population. Because BAV is a disease of both the valve and the aorta, surgical decision making is more complicated, and many undergoing aortic valve replacement will also need aortic root surgery. With or without surgery, patients with BAV require continued surveillance. Recent studies have improved our understanding of the genetics, the pathobiology, and the clinical course of the disease, but questions are still unanswered. In the future, medical treatment strategies and timing of interventions will likely be refined. This review summarizes our current understanding of the pathology, genetics, and clinical aspects of BAV disease with a focus on BAV disease in adulthood.

Measuring aortic pulse wave velocity using high-field cardiovascular magnetic resonance: comparison of techniques

BACKGROUND

The assessment of arterial stiffness is increasingly used for evaluating patients with different cardiovascular diseases as the mechanical properties of major arteries are often altered. Aortic stiffness can be noninvasively estimated by measuring pulse wave velocity (PWV). Several methods have been proposed for measuring PWV using velocity-encoded cardiovascular magnetic resonance (CMR), including transit-time (TT), flow-area (QA), and cross-correlation (XC) methods. However, assessment and comparison of these techniques at high field strength has not yet been performed. In this work, the TT, QA, and XC techniques were clinically tested at 3 Tesla and compared to each other.

METHODS

Fifty cardiovascular patients and six volunteers were scanned to acquire the necessary images. The six volunteer scans were performed twice to test inter-scan reproducibility. Patient images were analyzed using the TT, XC, and QA methods to determine PWV. Two observers analyzed the images to determine inter-observer and intra-observer variabilities. The PWV measurements by the three methods were compared to each other to test inter-method variability. To illustrate the importance of PWV using CMR, the degree of aortic stiffness was assessed using PWV and related to LV dysfunction in five patients with diastolic heart failure patients and five matched volunteers.

RESULTS

The inter-observer and intra-observer variability results showed no bias between the different techniques. The TT and XC results were more reproducible than the QA; the mean (SD) inter-observer/intra-observer PWV differences were -0.12(1.3)/-0.04(0.4) for TT, 0.2(1.3)/0.09(0.9) for XC, and 0.6(1.6)/0.2(1.4) m/s for QA methods, respectively. The correlation coefficients (r) for the inter-observer/intra-observer comparisons were 0.94/0.99, 0.88/0.94, and 0.83/0.92 for the TT, XC, and QA methods, respectively. The inter-scan reproducibility results showed low variability between the repeated scans (mean (SD) PWV difference = -0.02(0.4) m/s and r = 0.96). The inter-method variability results showed strong correlation between the TT and XC measurements, but less correlation with QA: r = 0.95, 0.87, and 0.89, and mean (SD) PWV differences = -0.12(1.0), 0.8(1.7), and 0.65(1.6) m/s for TT-XC, TT-QA, and XC-QA, respectively. Finally, in the group of diastolic heart failure patient, PWV was significantly higher (6.3 +/- 1.9 m/s) than in volunteers (3.5 +/- 1.4 m/s), and the degree of LV diastolic dysfunction showed good correlation with aortic PWV.

CONCLUSIONS

In conclusion, while each of the studied methods has its own advantages and disadvantages, at high field strength, the TT and XC methods result in closer and more reproducible aortic PWV measurements, and the associated image processing requires less user interaction, than in the QA method. The choice of the analysis technique depends on the vessel segment geometry and available image quality.

Serum Levels of Natriuretic Peptides in Children before and after Treatment for an Atrial Septal Defect, a Patent Ductus Arteriosus, and a Coarctation of the Aorta-A Prospective Study

Background and Objectives. We evaluated and compared the influence of treatment for atrial septal defect (ASD), patent ductus arteriosus (PDA), and coarctation of the aorta (CoA) on serum levels of N-terminal proatriopeptide and N-terminal probrain natriuretic peptide. Correlations between peptide levels and echocardiographic measurements were calculated. Patients and Methods. Peptide levels were measured and echocardiography performed before and 6-12 months after treatment in 21 children with ASD, 25 with PDA, 15 with CoA, and 76 control children. Results. ANPN levels were higher than in controls at baseline in all patient groups, and NT-proBNP in patients with ASD and PDA. Both peptide levels were elevated 6 months after treatment and decreased thereafter. Peptide levels were higher in patients with volume than pressure overload. They correlated with echocardiographic measurements. At the 6-month follow-up, dimensions of the originally overloaded ventricle had normalized only in patients with PDA. Conclusions. After intervention, peptide levels decrease but normalization takes over 6 months. The type of correlation between peptide levels and echocardiography varies according to the loading condition. Measurement of peptide levels can be used for monitoring the course of a patient's heart disease.

Ventricular–Vascular Stiffening in Patients With Repaired Coarctation of Aorta

Background— Despite successful repair, patients with coarctation of the aorta (COA) often show persistent hypertension at rest and/or during exercise. Previous studies indicated that the hypertension is mainly due to abnormalities in the arterial bed and its regulatory systems. We hypothesized that ventricular systolic stiffness also contributes to the hypertensive state in these patients in addition to increased vascular stiffness.

Methods and Results— The study involved 43 patients with successfully repaired COA and 45 age-matched control subjects. Ventricular systolic stiffness (end systolic elastance) and arterial stiffness (effective arterial elastance) were measured invasively by ventricular pressure–area relationship during varying preload before and after β-adrenergic stimulation. The mean systolic blood pressure was significantly higher with concomitant increases in both end systolic elastance and effective arterial elastance in patients with COA compared with control subjects (113.2±16.8 versus 91.0±9.1 mm Hg, 44.5±17.0 versus 19.2±6.7 mm Hg/mL/m 2 , and 27.8±11.4 versus 20.2±4.8 mm Hg/mL/m 2 , respectively; P <0.01 for each). End systolic elastance and effective arterial elastance of patients with COA showed exaggerated responses to β-adrenergic stimulation, further amplifying blood pressure elevation. Quantification analyses assuming that ventricular systolic stiffness of patients with COA is equal to that of the control revealed that ventricular systolic stiffness accounts for approximately 50% to 70% of the elevated blood pressure in patients with COA. Furthermore, combined ventricular–arterial stiffening amplified systolic pressure sensitivity to increased preload during abdominal compression and limited stroke volume gain/relaxation improvement induced by β-adrenergic stimulation.

Conclusions— Increased ventricular systolic stiffness, coupled with increased arterial stiffness, plays important roles in hypertension in patients with repaired COA. Thus, ventricular systolic stiffness is a potentially suitable target for reduction of blood pressure and improvement of prognosis of patients with COA.

Factors affecting left ventricular remodelling and mechanics in the long-term follow-up after successful repair of aortic coarctation

AIMS

To identify factors predisposing to abnormal left ventricular geometry and mechanics in 52 patients after successful repair of aortic coarctation.

METHODS AND RESULTS

We evaluated left ventricular remodelling, systolic midwall mechanics, and isthmic gradient by echo-Doppler, systemic blood pressure at rest/exercise and by ambulatory blood pressure monitoring, and the aortic arch by magnetic resonance imaging. Echocardiographic findings were compared with those of 142 controls. The patients with aortic coarctation showed an increased indexed left ventricular end-diastolic volume, increased mass index, increased ratio of mass to volume and systolic chamber function. The contractility, estimated at midwall level, was increased in 21 percent of the patients. In 26 (50 percent) of the patients, we found abnormal left ventricular geometry, with 9 percent showing concentric remodelling, 33 percent eccentric hypertrophy, and 8 percent concentric hypertrophy. These patients were found to be older, underwent a later surgical repair, and to have higher systolic blood pressures at rest and exercise as well as during ambulatory monitoring. The relative mural thickness and mass index of the left ventricle showed a significant correlation with different variables on uni- and multivariate analysis. Age and diastolic blood pressure at rest are the only factors associated with abnormal left ventricular remodelling.

CONCLUSIONS

Patients who have undergone a seemingly successful surgical repair of aortic coarctation may have persistently abnormal geometry with a hyperdynamic state of the left ventricle. This is more frequent in older patients, and in those with higher diastolic blood pressures.

Elastic properties of the ascending aorta in young children after successful coarctoplasty in infancy

BACKGROUND

Based on the hypothesis that vascular dysfunction in the ascending aorta can cause morbidity, we undertook this study on the elastic properties of ascending aorta and left ventricular (LV) function in young children who received coarctoplasty in early infancy.

METHODS

Blood pressures (BP) in the right arm and ascending aortic internal diameters determined by M-mode ultrasound at rest and after exercise were measured in 25 patients (mean age, 6.4+/-3 years) and 22 control subjects (mean age, 5.8+/-2.4 years). Ascending aortic stiffness index and distensibility were calculated using BP measurements and ascending aortic internal diameters. In addition, LV parameters (systolic and diastolic function, mass index) were evaluated.

RESULTS

Compared with control subjects, patients had increased stiffness index (at rest: 4.87+/-1.94 versus 3.57+/-1.19, P=0.021; after exercise: 4.33+/-1.91 versus 3.2+/-1.26, P=0.034) and decreased distensibility (at rest: 6.90+/-3.15 versus 8.72+/-2.77, P=0.02; after exercise: 5.69+/-2.39 versus 7.88+/-3.44 cm2 dyn(-1) 10(-6), P=0.023). BP and LV parameters showed no consistent differences between the two groups. In patients, distensibility was significantly correlated with systolic BP (at rest: P=0.008; after exercise: P=0.014) and pulse pressure (at rest: P=0.013; after exercise: P=0.001).

CONCLUSIONS

This study suggests that vasculopathy of ascending aorta is possible in some young children despite early correction. However, long-term tracking study is needed to clarify the significance of the study.

Ambulatory blood pressure, left ventricular mass, and conduit artery function late after successful repair of coarctation of the aorta

OBJECTIVES

We sought to evaluate the determinants of hypertension during daily life and left ventricular (LV) hypertrophy in patients with successfully repaired coarctation of the aorta (CoA), as well as their relationship to abnormalities of arterial function.

BACKGROUND

Arterial hypertension may recur late after repair of CoA, which is related to a more adverse outcome. Furthermore, patients with normal resting blood pressure (BP) may have hypertension during daily life and LV hypertrophy. The determinants of these two adverse prognostic factors have not been investigated.

METHODS

We studied 72 patients (9 to 58 years of age) who underwent coarctation repair at age 0.1 to 480 months (42 [60%] at <1 year) and had been followed up for 155 +/- 76 months. They underwent ambulatory BP monitoring, echocardiography for LV mass, studies of brachial artery responses to flow (i.e., flow-mediated dilation [FMD]) and glyceryl trinitrate (GTN), and determination of pulse wave velocity (PWV) and measures of arterial reactivity and stiffness. Findings were compared with those of 53 healthy volunteers.

RESULTS

Patients had higher 24-h systolic BP and LV mass than controls. Both endothelium-dependent FMD and the response to the smooth muscle dilator GTN were reduced, and PWV was increased. There was a negative independent correlation between GTN response and 24-h systolic BP in both patients and control subjects. Systolic BP at 24 h was an independent predictor of LV mass, having an accentuated impact in coarctation subjects as compared with controls.

CONCLUSIONS

In patients with repaired coarctation, reduced vascular reactivity is associated with hypertension during daily life and with increased LV mass, both of which are important predictors for late morbidity and mortality.

Left ventricular remodeling, mechanics, and tissue characterization in congenital aortic stenosis

BACKGROUND

As the response of the myocardium to pressure overload is age-dependent, this study was designed to examine left ventricular (LV) remodeling, mechanics, and tissue characterization in children with moderate congenital aortic stenosis.

METHODS

We studied by echocardiography Doppler 22 patients (mean age 12.4 +/- 5.6 years) with peak and mean transvalvular gradient of 63 +/- 6 and 32 +/- 4 mm Hg, respectively. In addition, 30 age- and body surface area-matched participants with structurally normal hearts were used as a control group. Sex- and age-specific cut-off levels for LV mass/height(2.7) and relative wall thickness were defined to assess LV geometry. As a load-independent index of myocardial contractility, the relation between the rate-corrected velocity of circumferential fiber shortening both at endocardium and midwall, and meridional end-systolic stress was assessed. In addition, LV diastolic function was also evaluated by the mitral flow indexes. Finally, ultrasonic tissue characterization of the LV myocardium was performed by calculating the magnitude of cyclic variation, which reflects the intramural contractile function, and the averaged myocardial intensity of integrated backscatter, which is directly related to the myocardium collagen content.

RESULTS

The endocardial velocity of circumferential fiber shortening endocardium and meridional end-systolic stress relationship was within the normal range (mean +/- 2SD) in 18 of 22 patients (81.8%), and midwall velocity of circumferential fiber shortening at endocardium and meridional end-systolic stress was normal in all 22 patients. No mitral flow index of LV diastolic function was significantly different between aortic stenosis group and normal participants. In our study population, 16 of 22 patients (72.7%) showed normal LV geometry, 3 (13.6%) had a pattern of concentric remodeling, and 3 (13.6%) concentric hypertrophy. LV hypertrophy was not marked (left ventricular mass index [LVMI] < 51 g/m(2.7)) in any patient. Finally, compared with control participants our study population showed, both at interventricular septum and posterior wall, comparable values of cyclic variation integrated backscatter, but significantly higher values of averaged myocardial integrated backscatter intensity (P <.01).

CONCLUSIONS

In children with moderate congenital aortic stenosis, the total amount of myocardial collagen was increased despite normal LV myocardial contractility and diastolic function. Furthermore, LV remodeling was abnormal in only about a quarter of our patients and none had more than mild hypertrophy. Although the majority of these patients do not have markers now recognized to predict higher risk of cardiovascular events, the long-term significance of myocardial fibrosis and its response to treatment remain to be investigated.

Pressure-flow loops and instantaneous input impedance in the thoracic aorta: another way to assess the effect of aortic bypass graft implantation on myocardial, brain, and subdiaphragmatic perfusion

BACKGROUND

The serious disturbances in ventriculoarterial coupling after thoracic aorta bypass grafting are addressed through aortic entry impedance in the frequency domain from flow-pressure waves. We designed a method for synthesizing pressure and flow waves to evaluate opposal to aortic flow along the cardiac cycle, addressing myocardial, brain, and visceral tissue perfusions from pressure-flow hysteresis loops and forward-backward aortic entry impedance in the ascending aorta, transverse aortic arch, and distal descending aorta, respectively, before and after extra-anatomic grafting of the descending aorta in the swine.

METHODS

Twelve pigs underwent extra-anatomic grafting (woven double-velour prosthesis, 18-mm diameter), bypassing the descending aorta. Periarterial flow and endovascular pressure signals were mathematically synthesized (error minimization) to yield continuous functions of flow, pressure along the cardiac cycle before treatment for mean hemodynamics, pressure-flow hysteresis loops, and aortic entry impedance.

RESULTS

Grafting of the descending aorta overshadowed pressure-flow hysteresis loops in the ascending aorta by shortening maximum pressure delay on maximum flow and diastolic flow reversal. Clamping of the descending aorta substantially restored hemodynamics in the ascending aorta, although the diastolic flow decrease was accelerated. Identical processes developed in the transverse aorta. Subdiaphragmatic descending aortic flow was flattened after grafting and restored, although thickened, after clamping of the descending aorta. Flow wave peak was framed by a diastolic aortic entry impedance peak, which was damped along the transverse aortic arch (aortic entry impedance peak in the ascending aorta, 1700 +/- 102 kN x s x m(-5); aortic entry impedance peak in the descending aorta, 292 +/- 45 kN x s x m(-5); P <.05). After grafting, the aortic entry impedance peak was transferred to early systole (aortic entry impedance peak in the transverse aortic arch, 2104 +/- 94 kN x s x m(-5); aortic entry impedance peak in the descending aorta, 450 +/- 75 kN x s x m(-5); P <.05). Clamping of the descending aorta attenuated the early systolic aortic entry impedance peak (aortic entry impedance peak in the transverse aortic arch, 1269 +/- 104 kN x s x m(-5); aortic entry impedance peak in the descending aorta, 491 +/- 75 kN x s x m(-5); P <.05), although aortic entry impedance in the descending aorta remained higher than before grafting (P <.05). Specifically, the backward flow ascending aorta to coronary trunks generated a backward aortic entry impedance peak (2234 +/- 350 kN x s x m(-5)) superimposed onto the forward aortic entry impedance peak with asymptotic boundaries that diminished after grafting and further enlarged after clamping of the descending aorta.

CONCLUSIONS

Hemodynamic opposition of grafting of the descending aorta are specific to the aortic site and cardiac cycle and are dependent on clamping of the descending aorta. Our approach to thoracic aorta hemodynamics could enable optimization of bypass grafting.

Surgery for aortic coarctation: a 30 years experience

OBJECTIVE

A retrospective study to review the experience of a single center with surgery for aortic coarctation over a period of 30 years (1970-1999).

METHODS

Criteria for inclusion: (a) aortic coarctation, isolated or associated with congenital heart defect; (b) surgery between 1970 and 1999. Data recorded: (1) date of surgery; (2) age at surgery; (3) associated lesions; (4) surgical technique; (5) simultaneous surgical procedures; (6) early and late surgical results in term of: (a) deaths; (b) need for reoperation because of re-coarctation or other cardiac lesion; (c) residual/recurrent pressure gradient, evaluated at cuff/Doppler at rest; (d) systemic hypertension, requiring medical treatment.

RESULTS

One hundred and forty-one patients underwent surgery for aortic coarctation: 30 neonates, 29 infants, 45 children and 37 adults. Associated lesions were found in 8/37 (=21.6%) adults and in 73/104 (=70.1%) pediatric patients. There were no hospital deaths. During the follow-up there were one late death in the adults group (1/37=2.7%) and three late deaths in the pediatric group (3/104=2.9%), all unrelated with aortic coarctation. Re-operation because of re-coarctation occurred only in ten late survivors of the pediatric group (10/101=9.9%), 9/10 operated on before 1980 (P<0.00001). End-to-end anastomosis, enlarged to the aortic arch in neonates, was associated with the lowest incidence of re-coarctation (P<0.005). A significant (>20 mmHg at rest) pressure gradient was found in none of the adults, and in seven of the 91 pediatric patients (7/91=7.7%) late survivors. Three adults (3/36=8.3%) late survivors are on medical treatment to control systemic hypertension.

CONCLUSIONS

The long-term results of our retrospective study confirm that surgery has to be considered the gold standard for the treatment of aortic coarctation. The interventional angioplasty techniques have to provide long-term outcome at least similar to the results obtained with surgery.