Intravascular Ultrasound for Assessment of Residual Coarctation of the Aorta after Balloon Angioplasty in Infants.

Intravascular ultrasound (IVUS) has been introduced as an accurate and minimally invasive diagnostic technique for the assessment of vascular anatomy and its abnormalities. We believe that IVUS can be used for clarifying the reasons for failure of balloon angiography in infantile coarctation of the aorta (CoA), because post-balloon angioplasty tearing, intimal flap, thrombosis and pseudoaneurysm of the aorta can be evaluated by IVUS with greater sensitivity and specificity. We aimed to assess the outcome of balloon angioplasty of CoA using angiography as the gold standard and IVUS as a new method in infants, comparing the two techniques for the evaluation of the diameter and area of CoA segment pre- and post-procedure. This cross-sectional study was performed on 18 infants hospitalized with a final diagnosis of CoA. All the infants underwent angiography and were also assessed by IVUS to measure the preoperative and postoperative diameter of the narrow segment in the two anterior-posterior and lateral views. In assessment by IVUS, the mean diameter of the coarctation site increased from 2.10 ± 0.30 mm to 4.50 ± 0.94 mm (P < 0.001). Similarly, the average minimum area of the coarctation level increased from 5.26 ± 1.50 mm2 to 13.77 ± 3.48 mm2 after angioplasty (P < 0.001). Comparing these findings, angiography and IVUS showed a high level of agreement. In the assessment of a dissection flap, there was a high level of agreement between angioplasty and IVUS before the procedure, but IVUS had higher accuracy after the procedure. Our study showed that IVUS was more reliable than angiography in the assessment of residual coarctation. IVUS yielded high sensitivity (58.3%) and specificity (100%) for discriminating the presence and absence of residual coarctation as well as the need for repeating the procedure. The assessment of coarctation before and after angioplasty procedures in children is possible using the IVUS method, with high accuracy. IVUS can offer greater accuracy than angiography in the evaluation of the coarctation area, detecting tears, dissection and flaps, and assessment of residual coarctation.

Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation: Impact of Virtual Interventions.

Turbulence and flow eccentricity can be measured by magnetic resonance imaging (MRI) and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, we propose quantitative techniques to assess turbulent kinetic energy (TKE) and flow eccentricity that could assist in the evaluation and treatment of stenotic severities. These hemodynamic parameters were studied in a pre-treated aortic coarctation (CoA) and after several virtual interventions using computational fluid dynamics (CFD), to demonstrate the effect of different dilatation options on the flow field. Patient-specific geometry and flow conditions were derived from MRI data. The unsteady pulsatile flow was resolved by large eddy simulation including non-Newtonian blood rheology. Results showed an inverse asymptotic relationship between the total amount of TKE and degree of dilatation of the stenosis, where turbulent flow proximal the constriction limits the possible improvement by treating the CoA alone. Spatiotemporal maps of TKE and flow eccentricity could be linked to the characteristics of the jet, where improved flow conditions were favored by an eccentric dilatation of the CoA. By including these flow markers into a combined MRI-CFD intervention framework, CoA therapy has not only the possibility to produce predictions via simulation, but can also be validated pre- and immediate post treatment, as well as during follow-up studies.

Noninvasive hemodynamic assessment, treatment outcome prediction and follow-up of aortic coarctation from MR imaging.

PURPOSE: Coarctation of the aorta (CoA) is a congenital heart disease characterized by an abnormal narrowing of the proximal descending aorta. Severity of this pathology is quantified by the blood pressure drop (△P) across the stenotic coarctation lesion. In order to evaluate the physiological significance of the preoperative coarctation and to assess the postoperative results, the hemodynamic analysis is routinely performed by measuring the △P across the coarctation site via invasive cardiac catheterization. The focus of this work is to present an alternative, noninvasive measurement of blood pressure drop △P through the introduction of a fast, image-based workflow for personalized computational modeling of the CoA hemodynamics. METHODS: The authors propose an end-to-end system comprised of shape and computational models, their personalization setup using MR imaging, and a fast, noninvasive method based on computational fluid dynamics (CFD) to estimate the pre- and postoperative hemodynamics for coarctation patients. A virtual treatment method is investigated to assess the predictive power of our approach. RESULTS: Automatic thoracic aorta segmentation was applied on a population of 212 3D MR volumes, with mean symmetric point-to-mesh error of 3.00 ± 1.58 mm and average computation time of 8 s. Through quantitative evaluation of 6 CoA patients, good agreement between computed blood pressure drop and catheter measurements is shown: average differences are 2.38 ± 0.82 mm Hg (pre-), 1.10 ± 0.63 mm Hg (postoperative), and 4.99 ± 3.00 mm Hg (virtual stenting), respectively. CONCLUSIONS: The complete workflow is realized in a fast, mostly-automated system that is integrable in the clinical setting. To the best of our knowledge, this is the first time that three different settings (preoperative--severity assessment, poststenting--follow-up, and virtual stenting--treatment outcome prediction) of CoA are investigated on multiple subjects. We believe that in future-given wider clinical validation-our noninvasive in-silico method could replace invasive pressure catheterization for CoA.

Non-invasive hemodynamic assessment of aortic coarctation: validation with in vivo measurements.

We propose a CFD-based approach for the non-invasive hemodynamic assessment of pre- and post-operative coarctation of aorta (CoA) patients. Under our approach, the pressure gradient across the coarctation is determined from computational modeling based on physiological principles, medical imaging data, and routine non-invasive clinical measurements. The main constituents of our approach are a reduced-order model for computing blood flow in patient-specific aortic geometries, a parameter estimation procedure for determining patient-specific boundary conditions and vessel wall parameters from non-invasive measurements, and a comprehensive pressure-drop formulation coupled with the overall reduced-order model. The proposed CFD-based algorithm is fully automatic, requiring no iterative tuning procedures for matching the computed results to observed patient data, and requires approximately 6-8 min of computation time on a standard personal computer (Intel Core2 Duo CPU, 3.06 GHz), thus making it feasible for use in a clinical setting. The initial validation studies for the pressure-drop computations have been performed on four patient datasets with native or recurrent coarctation, by comparing the results with the invasively measured peak pressure gradients recorded during routine cardiac catheterization procedure. The preliminary results are promising, with a mean absolute error of less than 2 mmHg in all the patients.

Hemodynamic assessment of pre- and post-operative aortic coarctation from MRI.

Coarctation of the aorta (CoA), is a congenital defect characterized by a severe narrowing of the aorta, usually distal to the aortic arch. The treatment options include surgical repair, stent implantation, and balloon angioplasty. In order to evaluate the physiological significance of the pre-operative coarctation and to assess the post-operative results, the hemodynamic analysis is usually performed by measuring the pressure gradient (deltaP) across the coarctation site via invasive cardiac catheterization. The measure of success is reduction of the (deltaP > 20 mmHg) systolic blood pressure gradient. In this paper, we propose a non-invasive method based on Computational Fluid Dynamics and MR imaging to estimate the pre- and post-operative hemodynamics for both native and recurrent coarctation patients. High correlation of our results and catheter measurements is shown on corresponding pre- and post-operative examination of 5 CoA patients.

Assessment of vascular phenotype using a novel very-high-resolution ultrasound technique in adolescents after aortic coarctation repair and/or stent implantation: relationship to central haemodynamics and left ventricular mass.

OBJECTIVES: Coarctation of the aorta (CoA) has been associated with abnormal vascular function, increased blood pressure (BP) and premature cardiovascular disease even after a successful intervention. The objective was to determine the severity of residual cardiovascular abnormalities in youths after CoA repair and their relation to regional BP. DESIGN: Cross-sectional study in tertiary healthcare setting. METHODS: Thirty-six youths with CoA (age 16±1 years; neonatal surgery only: n=16; surgery and/or stent implantation: n=20) and 37 age-matched controls were prospectively examined using a very-high-resolution vascular ultrasound imaging, echocardiography and applanation tonometry. RESULTS: CoA was associated with increased right arm systolic BP (p<0.001), intima-media thickness (IMT) in the common carotid (p<0.001), right brachial (p<0.05) and radial (p<0.05) arteries and ascending aortic stiffness (p<0.05). Carotid IMT correlated positively with age at first intervention (r=0.36, p<0.05). With left subclavian flap-type repair, left-arm systolic BP (p<0.001) and left brachial (p<0.001), radial (p<0.001) and ulnar (p<0.05) arterial IMTs were all reduced. When adjusted for BP, body mass index, age and gender, only carotid IMT (p<0.001) and left ventricular mass (p=0.013) of stented patients, as well as left-arm arterial IMTs (p<0.01) in subclavian flap-type repair patients, remained different from the controls. The significant associations of the stented patients disappeared after the adjustment for later patient age at intervention (median 8.7 vs 0.03 years, p<0.001). Residual arm-leg BP gradients correlated positively with carotid and brachial IMT. No differences between the CoA patients and the controls were found for arterial adventitial thicknesses, lumen dimensions, thigh systolic BP, abdominal aorta and carotid stiffness and right carotid to radial pulse wave velocity. CONCLUSION: CoA repair in early childhood is associated with increased preductal arterial IMT, left ventricular mass and ascending aortic stiffness in adolescents. The more pronounced cardiovascular abnormalities after CoA stent implantation are likely related to older patient age at the time of intervention.

Need for comprehensive vascular assessment before surgical repair of aortic coarctation in PHACES syndrome.

Children with PHACES syndrome commonly present with aortic coarctation and abnormalities of the supra-aortic and intracranial arteries. We describe a case of complex aortic coarctation in the context of PHACES syndrome, where preoperative detection of abnormalities in supra-aortic and intracranial arteries led to modification of the surgical technique adopted, in order to avoid potential neurological damage.

[Magnetic resonance imaging in long-term assessment after surgery for aortic coarctation]. / Valoración a largo plazo con resonancia magnética en pacientes corregidos de coartación de aorta.

OBJECTIVES: Spin echo or gradient echo magnetic resonance imaging provides enough information to plan patient management and can be completed with the use of three-dimensional magnetic resonance angiography to evaluate the need for reintervention, assess follow-up, or discharge the patient. PATIENTS AND METHODS: From 1990-2003, we evaluated 101 patients after initial corrective surgery for aortic coarctation at the age of 3.1 +/- 3 years, with subsequent postoperative assessment at 1 year and again 12.4 +/- 4.2 years later. No mortality was registered during the follow-up. Corrective surgery was performed in 32 patients (31.6 %) before the first month of life. All the patients were evaluated with spin-echo and echo gradient and 34 were evaluated with magnetic resonance angiography. The patients were classified into two groups: group A consisted of 68 patients (11 < 1 month old) with no complications. End-to-end anastomosis was performed in 55, the Alvarez technique in five, the Waldhausen technique in six, and conduit in two. Group B consisted of 33 patients complicated with early aortic recoarctation (21 corrected before the age of 1 month). End-to-end anastomosis was performed in 29, the Alvarez technique in two, and grafting in two. During the follow-up, 43 reinterventions were performed. Isthmus diameter/descending aorta diameter at the diaphragmatic level and repaired site diameter/descending aorta diameter at the diaphragmatic level were measured. RESULTS: Group A: the isthmus diameter/descending aorta diameter at the diaphragmatic level index was 0.92 +/- 0.08 and the repaired site diameter/ descending aorta diameter at diaphragmatic level index was 0.90 +/- 0.05. Twenty-three patients were assessed by means of three-dimensional magnetic resonance angiography, which revealed two late stenosis (one in a 10-year-old patient with an end-to-end anastomosis performed previously, and another in an 18-year-old patient with a proximal and distal obstructed conduit). Group B: the isthmus diameter/descending aorta diameter index was 0.84 +/- 0.1 and the repaired site diameter/ descending aorta diameter index was 0.82 +/- 0.11. Eleven patients were assessed by means of three-dimensional magnetic resonance angiography, which revealed five stenosis indexes (0.53-0.73) surgically corrected before the age of 2 months, four with an initial technique based on end-to-end anastomosis and one with a graft. CONCLUSIONS: Our results support the influence of young age, the use of end-to-end anastomosis and grafts in recoarctation and their late influence on recurrent recoarctation. The patients in group A were discharged in childhood or adulthood after periodic follow-up every 5 years with magnetic resonance angiography for 18 years with results within the normal range, while patients in group B required longer follow-up.

Exercise systolic blood pressures are of questionable value in the assessment of the adult with a previous coarctation repair.

BACKGROUND: The role of exercise testing in the follow up of adults with a coarctation repair is unclear. Exercise induced systolic hypertension has been advocated as an indication for further investigation; however, the value of exercise testing in this role has been questioned, especially in paediatric populations. OBJECTIVE: To assess the value of resting and exercise blood pressure measurements in a cohort of adults with repaired coarctation. SETTING: Tertiary referral centre for adult congenital cardiac disease. PATIENTS: 56 patients (33 male, 23 female) with a previous coarctation repair, and 33 age matched controls. MAIN OUTCOME MEASURES: Resting and exercise blood pressures, including arm-leg systolic blood pressure gradients; standard echocardiographic measurements of left ventricular mass, aortic root diameter, and repair site gradient. RESULTS: The coarctation cohort had higher resting upper limb blood pressures than the controls (systolic: 129.7 v 120.7 mm Hg, p = 0.014; diastolic: 76.8 v 72.2 mm Hg, p = 0.02). Mean resting arm-leg systolic blood pressure gradient was also higher, at 3.6 v -2.2 mm Hg, p = 0.027. However, there were no differences between the peak exercise systolic blood pressures of the two groups. Peak exercise systolic blood pressure did not correlate with resting arm-leg blood pressure gradient (r = 0.24, p = 0.13) or with repair site gradient (r = 0.14, p = 0.39). Resting upper limb systolic blood pressure and resting arm-leg systolic blood pressure gradient were related to repair site gradient (r = 0.33, p = 0.03, and r = 0.47, p = 0.002). CONCLUSIONS: Measurements of upper limb blood pressure during exercise are of limited value in the assessment of the post-repair coarctation patient. If routine exercise testing is to be advocated in this population it must be for another indication.

Coarctation of the aorta: collateral flow assessment with phase-contrast MR angiography.

OBJECTIVE: The purpose of this report is to describe a new use of MR imaging in coarctation of the aorta. The specific question addressed was how well collateral blood flow in intercostal arteries, as determined by phase-contrast MR angiography, correlated with findings during surgery or catheterization in patients with coarctation of the aorta. CONCLUSION: Phase-contrast MR angiography is an excellent technique for detecting the presence or absence of collateral blood flow in the intercostal arteries of patients with coarctation of the aorta. Knowing whether collateral blood flow is present in patients with narrowing of the juxtaductal aorta should help assess the clinical hemodynamic significance of the coarctation.

Comparison of transthoracic three dimensional echocardiography with magnetic resonance imaging in the assessment of right ventricular volume and mass.

OBJECTIVE: Assessment of right ventricular volume and mass with three dimensional echocardiography and comparison with magnetic resonance imaging. METHODS: Measurements of right ventricular volumes performed on three dimensional datasets acquired by transthoracic echocardiography were compared to those obtained from magnetic resonance imaging performed on the same day. Volumes were measured in end systole and end diastole and ejection fraction calculated. Right ventricular mass was assessed in end systole. With both methods, the areas of a 2 mm thick slice of the ventricle were manually outlined and multiplied by the slice thickness to obtain slice volume. Slice volumes were multiplied by the number of measured slices to obtain the ventricular volume. PATIENTS: 16 patients were studied: three with normal hearts, three after surgical repair of coarctation of the aorta, nine following repair of tetralogy of Fallot, and one with Mustard atrial repair of complete transposition of the great arteries. RESULTS: Correlation between end diastolic volumes measured by both methods was r = 0.95 with limits of agreement ranging from -3.5 to 12.5 ml; correlation for end systolic volumes was r = 0.87 with limits of agreement between -4.0 and 16.4 ml; correlation for end systolic right ventricular mass was r = 0.81 with limits of agreement between -7.0 and 20.6 g. Interobserver variability ranged from 4.3% (range 0.2% to 9.3%) for end diastolic volume to 7.6% (1.8% to 15.4%) for mass measurements. CONCLUSIONS: With transthoracic three dimensional echocardiography, end diastolic right ventricular volumes can be assessed with acceptable accuracy in normal hearts and those with enlarged right ventricles, whereas the current method of three dimensional echocardiography is less good for end systolic volumes and not satisfactory for right ventricular mass measurements.

Intravascular ultrasound assessment of regional aortic wall stiffness, distensibility, and compliance in patients with coarctation of the aorta.

BACKGROUND: Impaired aortic pulsatility has been demonstrated by angiography in children and in studies of experimental animals with coarctation of the aorta. OBJECTIVES: The purpose of this study was to assess regional aortic stiffness, distensibility, and compliance before and after balloon dilation in patients with coarctation of the aorta. METHODS AND RESULTS: Intravascular ultrasound examination was performed in 13 pediatric patients with the diagnosis of coarctation of the aorta to yield aortic diameter. Area transverse sections at both systolic and diastolic period were measured at three aortic levels: the proximal, distal, and coarctation segments. Balloon dilation was also performed in eight of 13 patients. By using pressures measured in the same areas, an aortic stiffness index (beta) was calculated as In(Ps/Pd)/(Ds-Dd), where In is natural logarithm, Ps is systolic pressure, Pd is diastolic pressure, Ds is systolic diameter, and Dd is diastolic diameter. Aortic distensibility and an estimation of aortic compliance were also calculated. The beta stiffness index of the coarctation and the proximal segments of the aorta were significantly greater than that of the distal segment of the aorta (p < 0.01). The aortic wall stiffness beta index did not acutely change after successful balloon dilation, but the distensibility and compliance of distal aorta were nonetheless significantly decreased after balloon dilation (p < 0.01, p < 0.05) as a function of changes of pulsatility of flow. CONCLUSIONS: Abnormal proximal aortic stiffness may be a strong contributing factor that promotes the genesis of hypertension in patients with coarctation even after successful repair or balloon angioplasty.

Comparison of magnetic resonance imaging with cross-sectional echocardiography in the assessment of left ventricular mass in children without heart disease and in aortic isthmic coarctation.

Although left ventricular (LV) mass may be important to judge effects of left-sided cardiac obstruction or hypertension, reproducible noninvasively determined normal data in the pediatric age group are scarce. To validate cross-sectional echocardiographic LV mass determination, our data were compared with LV mass assessed by magnetic resonance imaging (MRI). MRI was considered to be a good reference method because there is usually no problem in defining endo- and epicardial borders with MRI. LV mass was assessed in 14 children aged 5.3 years (10 days to 14.7 years) with a mean body surface area of 0.78 m2 (range 0.25 to 1.61). With cross-sectional echocardiography the epicardial and endocardial volumes were calculated using a Simpsons rule algorithm in the apical 2- and 4-chamber view. The difference between epi- and endocardial volumes was multiplied by 1.05 to yield the mass. Mass was assessed with MRI using a multislice technique; the area of each myocardial slice was calculated and multiplied with the slice thickness, and the resultant slice volumes were added to obtain the myocardial volume. On cross-sectional echocardiography, the mass was 55 g (range 12 to 126) or 64 g/m2 (range 46 to 79); on MRI it was 60 g (range 33 to 87) or 69 g/m2 (range 46 to 89). Regression analysis yielded an r value of 0.98 with a standard error of the estimate of 5.7 g or a 10% difference. In older children, LV mass determined by MRI was bigger than the one derived by echocardiography. It is concluded that cross-sectional echocardiography can reliably assess LV myocardial mass in pediatric patients.

Continuous wave Doppler echocardiography and coarctation of the aorta: gradients and flow patterns in the assessment of severity.

Indices of the severity of coarctation derived from non-invasive Doppler echocardiography were compared with measurements derived from cardiac catheterisation and angiography. In 24 Doppler studies from 17 children instantaneous peak systolic and diastolic gradients and time to half peak systolic and diastolic velocities were compared with the ratio of the coarctation diameter to the diameter of descending aorta at the level of diaphragm obtained from angiographic systolic frames of the aorta. A high peak systolic gradient (greater than 40 mm Hg) or long time to half peak diastolic velocity (greater than 100 ms) (that is, maintenance of flow in diastole) were both highly specific (100%) in detecting coarctation of the aorta where the angiographic ratio was less than or equal to 0.5. Diastolic measurements, however, were more sensitive (79% both for peak diastolic gradient and for time to half peak diastolic velocity) than systolic (57% for peak systolic gradient and 64% for time to half peak systolic velocity). Even higher sensitivity (93%) was obtained when the peak systolic gradient was greater than 40 mm Hg or the time to half peak diastolic velocity was greater than 100 ms. Examination by continuous wave Doppler echocardiography is an effective non-invasive method of assessing the severity of coarctation of the aorta, particularly when systolic and diastolic events are considered together. This approach overcomes the relatively low sensitivity of peak systolic gradient alone.