Marked disparity in mechanical wall properties between ascending and descending aorta in patients with tetralogy of Fallot

Significance of End-Diastolic Forward Flow in Patients With Repaired Tetralogy of Fallot - Its Interaction With the Left Ventricular Property and End Organ Damage

BACKGROUND

Although right ventricular (RV) enlargement may affect RV diastolic dysfunction assessed by end-diastolic forward flow (EDFF) in patients with repaired tetralogy of Fallot (TOF), EDFF may also be modified by left ventricular (LV) hemodynamics. We hypothesized that EDFF is affected by LV hemodynamics, not limited to RV diastolic stiffening.Methods and Results: Among 145 consecutive patients with repaired TOF who underwent catheterization, hemodynamic properties in 47 with consistent EDFF and 75 without EDFF were analyzed. Compared with patients without EDFF, those with EDFF had a large RV volume with a high regurgitant fraction. Although cardiac index and central venous pressure (CVP) were similar, contrast injection augmented CVP and LV end-diastolic pressure (EDP) in patients with vs. those without EDFF, suggesting compromised diastolic reserve. In patients with EDFF, the velocity-time integral (VTI) of EDFF was positively correlated with LVEDP and systemic vascular resistance, in addition to RV EDP. EDFF-VTI was correlated with hepatic venous wedge pressure and markers of hepatic dysfunction. Subanalysis of the older (≥6 years) half of the study cohort revealed that EDFF was associated with bi-atrial enlargement independent of RV volume, highlighting the pronounced role of EDFF on the diastolic property in the aged cohort.

CONCLUSIONS

EDFF-VTI in patients with repaired TOF reflects RV diastolic dysfunction, affected by the left heart system. EDFF-VTI indicates blood stagnation, which may be attributed to end-organ damage.

Patterns of Aortic Dilation in Tetralogy of Fallot: An Analysis of 100 Fetal Echocardiograms Compared With Matched Controls

Background Although aortic dilation is common in tetralogy of Fallot (TOF), its progression and risk of dissection are not well understood. The mechanism of dilation is primarily attributed to increased flow in utero; an alternative is unequal septation of the truncus arteriosus resulting in a larger aorta and inherently hypoplastic pulmonary artery (PA). If the latter is true, we hypothesize the aorta to PA ratio in TOF is stable throughout gestation, and sums of great artery dimensions are similar to controls. Methods and Results We performed a single-center retrospective study of fetuses with TOF (2014-2020) and matched controls. We compared sums of diameters, circumferences, and cross-sectional areas of the aorta and PA and evaluated the aorta to PA ratio across gestation in 2 TOF subtypes: pulmonary stenosis and atresia (TOF-PA). There were 100 echocardiograms with TOF (36% TOF-PA) with median gestational age of 31 weeks (interquartile range 26.5-34.4) and median maternal age of 34 years (interquartile range 30-37). There were no differences in sums of great artery dimensions between TOF-pulmonary stenosis and controls. In TOF-PA, sums were significantly lower than controls (P values <0.01). The aorta to PA ratio was stable throughout gestation (Pearson's r=0.08 [95% CI, -0.12 to 0.27], -0.06 [95% CI, -0.25 to 0.14]). Conclusions The aorta in fetal TOF is large but grows proportionally throughout gestation, with sums of great artery dimensions similar to controls. TOF-PA appears distinct from TOF-pulmonary stenosis (with smaller sums), warranting further investigation. In conclusion, our findings suggest an intrinsic developmental mechanism contributes to aortic dilation in TOF.

Is There a Role for Imaging Youth at Risk of Atherosclerosis?

PURPOSE OF REVIEW

Cardiovascular (CV) risk factors such as dyslipidemia, hypertension, diabetes, and obesity are associated with an increased risk for CV events in adults. Noninvasive measures of vascular health are associated with these CV events and can potentially help risk stratify children with CV risk factors. The purpose of this review is to summarize recent literature regarding vascular health in children with cardiovascular risk factors.

RECENT FINDINGS

Adverse changes in pulse wave velocity, pulse wave analysis, arterial distensibility, and carotid intima-media thickness are seen in children with CV risk factors supporting potential utility in risk stratification. Assessing vascular health in children can be challenging due to growth-related changes in vasculature, multiple assessment modalities, and differences in normative data. Vascular health assessment in children with cardiovascular risk factors can be a valuable tool for risk stratification and help identify opportunities for early intervention. Future areas of research include increasing normative data, improving conversion of data between different modalities, and increasing longitudinal studies in children linking childhood risk factors to adult CV outcomes.

Impaired ascending aortic elasticity in fetuses with tetralogy of Fallot

OBJECTIVES

Aortic wall stiffness has been reported in infants with tetralogy of Fallot (ToF) and may contribute to long-term aortic dilation even after corrective repair surgery. However, little is known about aortic elasticity in fetuses with ToF and the association with neonatal aortic dilation. The objectives of this study were to assess measures of elasticity of the ascending aorta (AAo) in fetuses with ToF and explore the association with neonatal aortic annular dilation in this population.

METHODS

Seventy-six singleton fetuses with ToF and 76 control fetuses of singleton low-risk pregnancies were enroled into this prospective study. Fetal measures of AAo elasticity, including mean longitudinal strain (MLS), global circumferential strain (GCS) and fractional area change (FAC), were assessed by velocity vector imaging. The z-score of the aortic valve (AV) diameter at the level of the annulus, as a measure of aortic annular dilation, was determined in newborns. Logistic regression analysis was used to investigate the association between fetal measures of AAo elasticity and neonatal aortic annular dilation (defined as an AV annular z-score > 2) in cases with ToF identified prenatally.

RESULTS

Median MLS, GCS and FAC in fetuses with ToF were lower than those in normal fetuses (7.52% vs 12.15% for MLS, 22.05% vs 29.73% for GCS and 34.2% vs 48.3% for FAC, all P < 0.001). Aortic annular dilation was present in 53/76 (69.7%) newborns with ToF. After adjustment for gestational age at fetal echocardiography and birth weight, fetal MLS, GCS and FAC were independently associated with aortic annular dilation neonatally, with odds ratios of 0.66, 0.78 and 0.82, respectively (P < 0.05). The best cut-off values of these prenatal measures of AAo elasticity for predicting neonatal aortic annular dilation in fetuses with ToF were 9.02% for MLS, 23.56% for GCS and 37.2% for FAC (P < 0.001), with areas under the receiver-operating-characteristics curves of 0.94, 0.91 and 0.93, respectively.

CONCLUSION

Measures of AAo elasticity are decreased in fetuses with ToF. Impaired AAo elasticity in the fetal period is associated with aortic annular dilation postnatally. Additional research is needed to evaluate the relationship between the AAo elasticity injury pattern and degeneration of AAo elasticity under stress as well as the long-term outcome in this population. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Realignment of the ventricular septum in tetralogy of Fallot using (partial) direct closure of the ventricular septal defect: Long-term follow-up and comparison to conventional patch repair

Objectives

Aortic dilatation and regurgitation after surgical repair of tetralogy of Fallot (TOF) is known, and beside other factors, mainly addressed to an intrinsic aortopathy. In 2011, we reported the influence of realingement of the left ventricular outflow tract (LVOT) by (partial) direct closure of the ventricular septal defect (VSD) in TOF on aortic structures and function. We now evaluated the further follow-up of this cohort and compared the results to a matched group of TOF patients with classical VSD patch closure.

Patients and Methods

Forty patients with TOF treated between 2003 and 2008 are included in the study, with 20 patients each in the VSD (a) (partial) direct closure and (b) patch closure group. Follow-up time after surgery was 12.3 years (11.3-13.0).

Results

Patient characteristics, echocardiographic measurements, and surgical and intensive care unit parameters were not significantly different between both groups. After surgery and during long-term follow-up, realignement of the LVOT, shown by the angle between the interventricular septum and the anterior aortic annulus in long axis view in echocardiography, was lower in Group A (34 vs. 45°, P < 0.0001). No differences in LVOT or aortic annulus size, aortic regurgitation, or dilation of the ascending aorta and right ventricular outflow tract gradients were found. Transient rhythm disturbances were found in 3 patients in each group, with only one persistent complete atrioventricular block in Group B.

Conclusion

(Partial) direct closure of the VSD in TOF leads to a better realignement of the LVOT and showed comparable short- and long-term results without higher risk for rhythm disturbances during follow-up.

Z-score model of foetal ascending aorta diameter distensibility

Objective

The purpose of this study is to establish Z-scores models of normal fetal ascending aorta diameter and diameter distensibility.

Methods

The maximum systolic diameter (Dmax), minimum diastolic diameter (Dmin), and diameter distensibility of the sinotubular junction were measured and taken as dependent variables in 490 normal fetuses at 18–40 gestational weeks, and gestational age (GA), biparietal diameter (BPD), and femoral length (FL) were taken as independent variables. The data were subjected to regression analysis, and the best-fitting equations for the dependent variables based on the independent variables were determined. The fitting equations were then applied to construct the Z-scores models.

Results

The Dmax, Dmin and Diameter Distensibility in normal fetuses between 18 and 40 weeks of GA could be evaluated by utilizing the Z-scores models. Dmax and Dmin increased significantly with increasing GA, BPD, and FL. Diameter distensibility, assessed as (Dmax–Dmin)/Dmin, decreased significantly with increasing GA, BPD, and FL.

Conclusion

The Z-scores are valuable, and can be utilized as a potent supplement to the conventional approach as they can indirectly reflect the development of fetal ascending aortic elastic property.

Vascular aging in adult congenital heart disease-a narrative review

Background and Objective

Many studies about the high prevalence of cardiovascular disease in adults with congenital heart disease (CHD) have been published in response to the growing number of adult patients with CHD. The aging process leads to hypertension and cardiovascular disease, which is caused by a degenerative change in the systemic arterial system characterized by the stiffening of elastic arteries (known as arteriosclerosis) and the enlargement of aorta. In patients with CHD, aortic dilatation (so-called aortopathy) is one of the most frequent complications. It is well known the anatomical and histological changes in aortopathy are similar to those in aging process. The increase of pulse wave velocity (PWV) enhances pressure wave reflection, and it augments left ventricular afterload and impairs the coronary supply-workload balance in aging. This article reviews the aortic function in patients with CHD, aiming to provide a new direction for the management of their cardiovascular aging process.

Methods

Papers on vascular physiology in CHD were retrieved. I searched all original papers and reviews about the vascular physiology in CHD using PubMed, published from January 1, 1973 to June 30, 2022, in English.

Key Content and Findings

Enhancement of pressure wave reflection has been reported in many CHDs. Although PWV in whole aorta is not necessarily elevated, the abnormal arterial stiffness gradient is common in patients with CHD.

Conclusions

Many reports concerning functional abnormalities of the aorta have been reported. The abnormalities can result in cardiovascular disease and organ damage. The practitioners should carefully treat patients with CHD while paying attention to their aging process.

Comprehensive Characterization of Arterial and Cardiac Function in Marfan Syndrome-Can Biomarkers Help Improve Outcome?

Background: Marfan Syndrome (MFS) has been associated with increased aortic stiffness and left ventricular dysfunction. The latter may be due to the underlying genotype and/or secondary to aortic stiffening (vascular-ventricular interaction). The aim of this study was to characterize arterial and cardiac function in MFS using a multimodal approach.

Methods: Prospective observational study of MFS patients and healthy controls. Methods included echocardiography, ascending aortic distensibility, common carotid intima media thickness [cIMT], parameters of wave reflection, carotid-femoral pulse wave velocity [cfPWV]), reactive hyperemia index [RHI], and biomarker analysis (Olink, CVII panel).

Results: We included 20 patients with MFS and 67 controls. Ascending aortic distensibility, cIMT and RHI were decreased, while all parameters of arterial wave reflection, stiffness and BNP levels were increased in the MFS group. Both systolic and diastolic function were impaired relative to controls. Within the MFS group, no significant correlation between arterial and cardiac function was identified. However, cfPWV correlated significantly with indexed left ventricular mass and volume in MFS. Bran natriuretic peptide (BNP) was the only biomarker significantly elevated in MFS following correction for age and sex.

Conclusions: MFS patients have generally increased aortic stiffness, endothelial dysfunction and BNP levels while cIMT is decreased, supporting that the mechanism of general stiffening is different from acquired vascular disease. CfPWV is associated with cardiac size, blood pressure and BNP in MFS patients. These may be early markers of disease progression that are suitable for monitoring pharmacological treatment effects in MFS patients.

Proximal Aortic Dilatation and Pulmonary Valve Replacement in Patients with Repaired Tetralogy of Fallot: Is There a Relationship? A Cardiac Magnetic Resonance Imaging Study

Aortopathy is a known complication whose incidence is growing within the population of tetralogy of Fallot (TOF) patients. Its pathology and relationship with other comorbidities remain unclear. This study was designed to determine the prevalence and predictors of proximal aortic dilatation after TOF repair. We retrospectively investigated all patients who underwent follow-up cardiac magnetic resonance imaging (CMR; at least 4 years after TOF repair) between March 2004 and December 2019. The dimensions at the ascending aorta (AAo) and sinus of Valsalva (SoV) levels were measured. Aortic dilatation was defined as an internal aortic diameter that was >2 standard deviation of the previously published normal values. We included 77 patients (mean age 28.9 ± 10.5 years, 41.5% female, mean follow-up of 24.5 ± 8.1 years). AAo and SoV were dilated in 19 (24.6%) and 43 (55.8%) patients, respectively. Patients with dilated AAo and SoV were older during the corrective surgery (p < 0.001 and p = 0.004, respectively) and during CMR (p = 0.002 and 0.024, respectively) than patients without AAo and SoV dilatation. Patients of the dilated AAo group were more likely to have prior palliative shunt (p = 0.008), longer shunt duration (p = 0.005), and a higher degree of aortic valve regurgitation (AR) fraction (p < 0.001) and to undergo pulmonary (PVR) and/or aortic valve replacement (p < 0.001 and p = 0.013, respectively). PVR (p = 0.048, odds ratio = 6.413, and 95% CI = 1.013-40.619) and higher AR fraction (p = 0.031, odds ratio = 1.194, and 95% CI = 1.017-1.403) were independent predictors for AAo dilatation. Aortopathy is a common progressive complication that may require reintervention and lifelong follow-up. Our study shows that proximal aortic dilatation may be attributed to factors that increase the volume overload across the proximal aorta, including late corrective surgery and palliative shunt. We also found that PVR and higher AR fraction are independent predictors of AAo dilatation.

Arterial Stiffness in Congenital Heart Disease

Transposition of the great arteries (TGA), coarctation of the aorta (CoA), single ventricle (SV) and tetralogy of Fallot (ToF) are forms of congenital heart disease (CHD). Despite advances in treatment, cardiovascular and cerebrovascular complications in patients with repaired CHD occur earlier in life compared to healthy subjects. A factor that may contribute to this increased risk is elevated arterial stiffness. This systematic review provides a critical assessment of current evidence on central arterial stiffness in patients with CHD compared to healthy controls. In July 2020, Medline OVID, EMBASE and Scopus were searched using keywords and MeSH terms. Articles were included if they reported indices of aortic or carotid artery stiffness in patients with TGA, CoA, SV or ToF, and compared these to controls. Additional studies were screened from the reference lists of included articles. Of 1,033 studies identified, 43 were included in the final review. Most studies identified at least one index of central arterial stiffness, commonly in the aortic root or ascending aorta, that was higher in patients with CHD compared to controls. The commonly reported surrogate markers of stiffness were pulse wave velocity, aortic distensibility and the β stiffness index. There was a relatively small number of original studies, and synthesis of data was limited by methodological heterogeneity, highlighting the need for further studies with standardised methods. However, there was consistent evidence of early and/or accelerated arterial stiffening in CHD patients, which may contribute to the increased risk of adverse cardiovascular and cerebrovascular events in this population.

Early vascular aging in adult patients with congenital heart disease

Many studies have reported that adults with congenital heart disease suffer from hypertension and cardiovascular disease even at younger ages. Therefore, we analyzed early vascular aging, which is defined as pulse wave velocity values higher than the 95th percentile for age and sex, and clarified the relationship between early vascular aging and many parameters related to cardiovascular disorders in adults with congenital heart disease. We enrolled 72 adult patients with congenital heart disease and measured their brachial-ankle pulse wave velocity. Comparing the data between age- and sex-matched controls, patients with a pulse wave velocity higher than the 95th percentile for age and sex were defined as exhibiting early vascular aging. The parameters of patients with and without early vascular aging were compared. Early vascular aging was observed in 15.6% of the patients. Age, systolic blood pressure, diastolic blood pressure, pulse pressure, blood sugar, hemoglobin A1c, uric acid, low-density lipoprotein cholesterol, and triglyceride levels were positive determinants of early vascular aging. Logistic regression analysis proved that systolic blood pressure was a significant determinant of early vascular aging (odds ratio, 1.128, 95% confidence interval, 1.049-1.214; p = 0.001). The prevalence of early vascular aging is high in adult patients with congenital heart disease. Because early vascular aging can damage a patient's vulnerable heart, careful follow-up of blood pressure and pulse wave velocity is essential.

Thoracic Aortic Dissection in Tetralogy of Fallot: A Review of the National Inpatient Sample Database

Background

Thoracic aortic aneurysm is common in patients with tetralogy of Fallot (TOF); the incidence of thoracic aortic dissection (TAD) is unknown, but generally considered to be uncommon. The purpose of this study was to determine incidence and risk factors for TAD in TOF patients.

Methods and Results

This work is a retrospective review of the National Inpatient Sample (NIS) database for cases of ascending TAD among all hospital admissions in adults with TOF, 2000–2014. Of 18 353 admissions in TOF patients, 11 (0.06%; 6 per 10 000 admissions) of these were TAD‐related admissions. For the TAD‐related admissions, mean age was 49.8±7.2 years; aortic surgical interventions were performed during 8 of the admissions, and overall in‐hospital mortality was 45% (5 of 11). Risk factors associated with TAD‐related admission were age >60 years (odds ratio, 2.41; 95% CI, 1.23–3.25; P=0.013), male sex (odds ratio, 6.91; 95% CI, 4.85–8.54; P<0.001), and hypertension (odds ratio, 1.74; 95% CI, 1.06–3.19; P=0.037).

Conclusions

This is the first population‐based study of TAD outcomes in patients with TOF, and it showed a low risk of TAD in this population. This has important clinical implication with regard to surveillance and surgical intervention. Given that prevalence of thoracic aortic aneurysm is higher in TOF patients compared with the general population; therefore, making clinical decisions based on outcomes data and practice guidelines derived from patients with degenerative and bicuspid aortic valve–related aortopathies may lead to overtreatment. Further studies are required to better understand the pathobiology of this disease in order to make evidence‐based recommendations for surveillance and treatment.

Aortopathy in tetralogy of Fallot-a collective review

The pathophysiology of aortic diseases in Tetralogy of Fallot has been analyzed in various studies, focusing on the histopathology of the aortic root, altered hemodynamics, and effect of early corrective repair on the incidence of aortic root dilatation. In this review article, we sought to integrate these studies for a better understanding of the natural history and practical implications of aortic root dilatation in Tetralogy of Fallot. This better equips us to appropriately implement potentially effective interventions.

Is it important to assess the ascending aorta after tetralogy of Fallot repair?

INTRODUCTION AND OBJECTIVES

Aortic dilatation can develop late after tetralogy of Fallot repair. Its extension beyond the aortic root is not clearly understood. We aimed to assess the prevalence and predictors of ascending aorta dilatation to set up an imaging protocol.

METHODS

In this prospective study including adult patients after tetralogy of Fallot repair followed at a referral center, we assessed the aorta by cardiovascular magnetic resonance and defined ascending aorta dilatation as an observed-to-expected ratio >1.5.

RESULTS

We included 78 adults (mean age 31±10 years; 56% female), with a mean follow-up of 23±7 years since tetralogy of Fallot repair. The prevalence of ascending aorta dilatation was 11.5%. The ascending aorta was larger than the sinuses of Valsalva in 12.8% of cases. Patients with ascending aorta dilatation were older, predominantly male, with later repair and larger left ventricular mass and volumes. By multivariate analysis left ventricular mass index (LVMI) was the only factor independently associated with ascending aorta dilatation (odds ratio 1.10, 95% confidence interval 1.01-1.20, p=0.03). A cut-off value of ≥57.9 g/m² for LVMI had 89% sensitivity and 71% specificity for ascending aorta dilatation.

CONCLUSIONS

Ascending aorta assessment as part of a routine cardiovascular magnetic resonance study after tetralogy of Fallot repair is recommended to screen for future aortic complications, particularly in males and older patients, and those with later repair and larger left ventricles. LVMI assessment has potential as a screening tool for ascending aorta dilatation with future clinical implications.

Utility of arterial stiffness assessment in children

Atherosclerotic cardiovascular disease is a leading cause of death and disability worldwide, and the atherosclerotic process begins in childhood. Prevention or containment of risk factors that accelerate atherosclerosis can delay the development of atherosclerotic cardiovascular disease. Although current recommendations are to periodically screen for commonly prevailing risk factors for atherosclerosis in children, a single test that could quantify the cumulative effect of all risk factors on the vasculature, thus assessing arterial health, would be helpful in further stratifying risk. Measurement of pulse wave velocity and assessment of augmentation index - measures of arterial stiffness - are easy-to-use, non-invasive methods of examining arterial health. Various studies have assessed pulse wave velocity and augmentation index in children with commonly occurring conditions including obesity, hypertension, insulin resistance, diabetes mellitus, dyslipidaemia, physical inactivity, chronic kidney disease, CHD and acquired heart diseases, and in children who were born premature or small for gestational age. This article summarises pulse wave velocity and augmentation index assessments and the effects of commonly prevailing chronic conditions on arterial health in children. In addition, currently available reference values for pulse wave velocity and augmentation index in healthy children are included. Further research to establish widely applicable normative values and the effect of lifestyle and pharmacological interventions on arterial health in children is needed.

Developmental Changes in Aortic Mechanical Properties in Normal Fetuses and Fetuses with Cardiovascular Disease

BACKGROUND

We hypothesized that fetal aortic mechanical properties assessed by aortic diameter (AoD) and flow show maturational changes during the gestational period, and that these properties are different in fetuses with congenital heart diseases and fetuses with normal development.

METHODS

Phasic changes in ascending AoD along with Doppler flow profile were measured in 84 consecutive normal fetuses (gestational age, 18-36 weeks) and in 30 consecutive fetuses with cardiovascular diseases (gestational age, 22-39 weeks).

RESULTS

AoD and cardiac output significantly increased with gestational age. Fetal aortic compliance (AC), assessed as (maximum AoD - minimum AoD)/stroke volume, significantly decreased with gestational age in normal fetuses, indicating maturational changes in aortic wall properties. Importantly, fetuses with Marfan syndrome and tetralogy of Fallot that exhibit "aortopathy" showed significantly lower AC than normal fetuses of the same gestational age, suggesting intrinsic abnormalities in aortic wall properties in these diseases. Fetuses with trisomy 18 and Noonan syndrome also had AC values below the normal ranges.

CONCLUSION

Measurements of phasic changes in fetal AoD and flow measurements can provide useful information about aortic mechanical properties and may help clarify abnormal arterial hemodynamics in pathologic conditions.

Noninvasive Assessment of Vascular Function in Postoperative Cardiovascular Disease (Coarctation of the Aorta, Tetralogy of Fallot, and Transposition of the Great Arteries)

Using noninvasive techniques, we sought to assess arterial stiffness, impedance, hydraulic power, and efficiency in children with postoperative tetralogy of Fallot (TOF), coarctation of the aorta (COA), and transposition of the great arteries (TGAs). Results were compared with those of healthy peers. Fifty-five children with repaired congenital heart disease (24 TOFs, 20 COAs, and 11 TGAs) were compared with 55 age-matched control subjects (CTRL). Echocardiographic Doppler imaging and carotid artery applanation tonometry were preformed to measure aortic flow, dimensions, and calculate pulse wave velocity, vascular impedance and arterial stiffness indexes, hydraulic power (mean and total), and hydraulic efficiency (HE) which were calculated using standard fluid dynamics equations. All congenital heart disease subgroups had higher pulse wave velocity than CTRL. Only the COA group had higher characteristic impedance. Mean power was higher in TGA than in CTRL and TOF, and total power was higher in TGA than in CTRL and TOF. Hydraulic efficiency was higher in TOF than in COA and TGA. In conclusion, children with TOF, COA, and TGA have stiffer aortas than CTRL. These changes may be related to intrinsic aortic abnormalities, altered integrity of the aorta due to surgical repair, and/or acquired postsurgery. These patients may be at increased long-term cardiovascular risk, and long-term follow-up is important for monitoring and assessment of efforts to reduce risk.

Mechanism of aortic root dilation and cardiovascular function in tetralogy of Fallot

The aortic root dilation in tetralogy of Fallot (TOF) is a long-term clinical problem, because a severely dilated aorta can lead to aortic regurgitation, dissection, or rupture, which can be fatal, necessitating surgical intervention. The details of the mechanism of aortic root dilation, however, are unclear. We have shown that aortic stiffness is increased in patients with repaired TOF, and may mirror the histological abnormality of elastic fiber disruption and matrix expansion. This aortic stiffness is related closely to the aortic dilation, indicating that aortic stiffness may be a predictor of outcome of aortic dilation. Furthermore, the aortic volume overload is a very important determinant of aortic diameter in TOF patients before corrective surgery. In addition, a chromosomal abnormality and the transforming growth factor-β signaling pathway, a major contributor to aortic dilation in Marfan syndrome, also affect this mechanism. In this way, aortic dilation in TOF patients is suggested to be a multifactorial disorder. The aim of this review was therefore to clarify the mechanism of aortic dilation in TOF, focusing on recent research findings. Studies linking histopathology, mechanical properties, molecular/cellular physiology, and clinical manifestations of aortic dilation facilitate appropriate treatment intervention and improvement of long-term prognosis of TOF.

Novel mechanisms for cerebral blood flow regulation in patients with congenital heart disease

BACKGROUND

The mechanisms that regulate cerebral flow in patients after surgery for congenital heart diseases (CHDs) remain poorly understood. We tested our hypothesis that postoperative patients with CHD have disease- or hemodynamic-specific compensatory mechanisms for maintaining cerebral perfusion.

METHODS

A total of 89 children with specific hemodynamics including Glenn (n = 14), Fontan (n = 19), repaired tetralogy of Fallot (n = 24), and control patients (n = 32) were enrolled. The resistance and blood flow distribution between the brain (Rc and CIc) and lower body (Rs and CIs) were calculated by measuring the hemodynamic changes resulting from inferior vena cava occlusion during cardiac catheterization.

RESULTS

Despite considerable differences in cardiac index and superior vena cava pressure (SVCp), cerebral blood flow was preserved in all noncontrol groups, with a ratio between the vascular resistances in the cerebral and lower body circulation (Rc/Rs) that was significantly lower than that in controls. Interestingly, the reduced Rc/Rs of Glenn patients was mediated by the reduced Rc, whereas augmented Rs was conducive to the reduced Rc/Rs in the Fontan and tetralogy of Fallot groups. Multivariate analysis revealed that high SVCp was significantly associated with low Rc. Although low cardiac index was significantly associated with increased Rc and Rs, its impact was much greater on Rs than on Rc.

CONCLUSIONS

Compensatory mechanisms for cerebral flow regulation occur according to hemodynamic abnormality type in postoperative patients with CHD. Because such a regulation mechanism implies cerebral circulation fragility, further investigations are needed to address the impacts of cerebral circulation properties on neurodevelopmental outcomes.

Aortic dilatation and aortopathies in congenital heart disease

PURPOSE OF REVIEW

The objective of this review is to summarize the recent data pertaining to aortic dilatation in congenital heart disease (CHD) and to discuss the current understanding of the pathophysiology and management of this disease.

RECENT FINDINGS

Aortic dilatation is a common finding in CHD. However, acute aortic complications appear to be relatively rare. Multiple factors predispose this population to aortic dilatation, including underlying genetics, cellular-based mechanisms, and abnormalities in aortic mechanics and valve morphology.

SUMMARY

Although aortic dilatation is common in CHD, data about adverse long-term outcomes are limited. Optimal disease-specific management strategies have yet to be developed, and further research is needed to guide care in this population.

Progressive aortic dilation and aortic stiffness in children with repaired tetralogy of Fallot

Progressive aortic dilation occurs in patients with tetralogy of Fallot (TOF), possibly due to abnormal histopathology of the aortic media that weakens the aortic wall. This medial histopathology may be reflected as aortic stiffness, which in turn may predict progressive aortic dilation. To test this theory, we studied the relationship between aortic wall stiffness, measured by pulse wave velocity (PWV), and subsequent aortic dilation in 32 consecutive patients with repaired TOF. The ascending aortic diameter (AOD) was obtained by two-dimensional transthoracic echocardiography performed at baseline and at the follow-up examination, 7.6 ± 2.0 years after baseline. TOF patients exhibited significantly greater AODs than normal reference values, at baseline (19.8 ± 5.0 vs 14.3 ± 3.1 mm; P = 0.0001) and at the follow-up examination (25.9 ± 3.8 vs 18.1 ± 2.4 mm; P = 0.0001). The observed change in AOD during the follow-up period (0.83 ± 0.43 mm/year) was significantly larger than the change that would be expected by the patient's growth (0.50 ± 0.25 mm/year; P = 0.0001). The PWV at baseline correlated positively with both AOD at follow-up (P = 0.0018) and the annual rate of aortic dilation (P = 0.0007). On multivariate regression analysis, PWV remained a significant and independent predictor of subsequent aortic dilation. These results suggest a causative role for aortic stiffening in the progressive aortic dilation noted in TOF, indicating that incorporating aortic stiffness as well as aortic diameter in the assessment of TOF aortopathy may help better define the need for, and the timing of, medical intervention.