Pixel-wise absolute pressures in the aortic arch from 3D MRI velocity data and carotid artery applanation tonometry

A pixel-wise method for absolute and local aortic pressures estimation using 3D velocities in MRI and carotid pressure curves to set-up reference pressure values is presented. This method is based on the Navier-Stokes equation and a fast iterative algorithm. Its reliability was demonstrated: 1) in a synthetic phantom by comparison against simplified Bernoulli equation applied at peak velocities, and 2) in a healthy subject and a patient with aortic coarctation, in which absolute pressure distribution within the aortic arch was consistent with established physiopathological knowledge. Such local absolute aortic pressures may be useful in the understanding of hemodynamic changes secondary to cardiovascular alterations. Also, their addition to the already available indices of risk of aortic complications such as dilatation and dissection definition may prove of major clinical usefulness.

Radiology case of the month. Abnormally dilated arteries in an asymptomatic male. RADIOLOGIC DIAGNOSIS: Aortic coarctation. There is narrowing in the region of the aortic isthmus (arrows, Figures 2 and 4). The extent of collateral arterial dilation (arrows, Figures 1 and 3) suggests this to be a hemodynamically significant finding

A 61-year-old male with a past medical history of chronic, uncontrolled hypertension received a non-contrasted computed tomogram (CT) of the chest and abdomen to investigate for possible Conn syndrome. This noncontrast study showed some areas of nodularity around the vertebral bodies bilaterally and extending into the posterior mediastinal region. A CT of the chest with intravenous contrast, and 3D reconstruction were then obtained.

Aortic arch shape is not associated with hypertensive response to exercise in patients with repaired congenital heart diseases

BACKGROUND

Aortic arch geometry is linked to abnormal blood pressure (BP) response to maximum exercise. This study aims to quantitatively assess whether aortic arch geometry plays a role in blood pressure (BP) response to exercise.

METHODS

60 age- and BSA-matched subjects--20 post-aortic coarctation (CoA) repair, 20 transposition of great arteries post arterial switch operation (ASO) and 20 healthy controls--had a three-dimensional (3D), whole heart magnetic resonance angiography (MRA) at 1.5 Tesla, 3D geometric reconstructions created from the MRA. All subjects underwent cardiopulmonary exercise test on the same day as MRA using an ergometer cycle with manual BP measurements. Geometric analysis and their correlation with BP at peak exercise were assessed.

RESULTS

Arch curvature was similarly acute in both the post-CoA and ASO cases [0.05 ± 0.01 vs. 0.05 ± 0.01 (1/mm/m²); p = 1.0] and significantly different to that of normal healthy controls [0.05 ± 0.01 vs. 0.03 ± 0.01 (1/mm/m²), p < 0.001]. Indexed transverse arch cross sectional area were significantly abnormal in the post-CoA cases compared to the ASO cases (117.8 ± 47.7 vs. 221.3 ± 44.6; p < 0.001) and controls (117.8 ± 47.7 vs. 157.5 ± 27.2 mm²; p = 0.003). BP response to peak exercise did not correlate with arch curvature (r = 0.203, p = 0.120), but showed inverse correlation with indexed minimum cross sectional area of transverse arch and isthmus (r = -0.364, p = 0.004), and ratios of minimum arch area/ descending diameter (r = -0.491, p < 0.001).

CONCLUSION

Transverse arch and isthmus hypoplasia, rather than acute arch angulation plays a role in the pathophysiology of BP response to peak exercise following CoA repair.

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.

Including aortic valve morphology in computational fluid dynamics simulations: initial findings and application to aortic coarctation

Computational fluid dynamics (CFD) simulations quantifying thoracic aortic flow patterns have not included disturbances from the aortic valve (AoV). 80% of patients with aortic coarctation (CoA) have a bicuspid aortic valve (BAV) which may cause adverse flow patterns contributing to morbidity. Our objectives were to develop a method to account for the AoV in CFD simulations, and quantify its impact on local hemodynamics. The method developed facilitates segmentation of the AoV, spatiotemporal interpolation of segments, and anatomic positioning of segments at the CFD model inlet. The AoV was included in CFD model examples of a normal (tricuspid AoV) and a post-surgical CoA patient (BAV). Velocity, turbulent kinetic energy (TKE), time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) results were compared to equivalent simulations using a plug inlet profile. The plug inlet greatly underestimated TKE for both examples. TAWSS differences extended throughout the thoracic aorta for the CoA BAV, but were limited to the arch for the normal example. OSI differences existed mainly in the ascending aorta for both cases. The impact of AoV can now be included with CFD simulations to identify regions of deleterious hemodynamics thereby advancing simulations of the thoracic aorta one step closer to reality.

Sonographic predictors of surgery in fetal coarctation of the aorta

OBJECTIVES

Isolated fetal coarctation of the aorta (CoA) has high false-positive diagnostic rates by cardiologists in tertiary centers. Isthmal diameter Z-scores (I), ratio of isthmus to duct diameters (I:D), and visualization of CoA shelf (Shelf) and isthmal flow disturbance (Flow) distinguish hypoplastic from normal aortic arches in retrospective studies, but their ability to predict a need for perinatal surgery is unknown. The aim of this study was to determine whether these four sonographic features could differentiate prenatally cases which would require neonatal surgery in a prospective cohort diagnosed with CoA by a cardiologist.

METHODS

From 83 referrals with cardiac disproportion (January 2006 to August 2010), we identified 37 consecutive fetuses diagnosed with CoA. Measurements of I and I:D were made and the presence of Shelf or Flow recorded. Sensitivity, specificity and areas under receiver-operating characteristics curves, using previously reported limits of I < - 2 and I:D < 0.74, as well as Shelf and Flow were compared at first and final scan. Associations between surgery and predictors were compared using multivariable logistic regression and changes in measurements using ANCOVA.

RESULTS

Among the 37 fetuses, 30 (81.1%) required surgery and two with an initial diagnosis of CoA were revised to normal following isthmal growth, giving an 86% diagnostic accuracy at term. The median age at first scan was 22.4 (range. 16.6-7.0) weeks and the median number of scans per fetus was three (range, one to five). I < - 2 at final scan was the most powerful predictor (odds ratio, 3.6 (95% CI, 0.47-27.3)). Shelf was identified in 66% and Flow in 50% of fetuses with CoA.

CONCLUSION

Incorporation of these four sonographic parameters in the assessment of fetuses with suspected CoA at a tertiary center resulted in better diagnostic precision regarding which cases would require neonatal surgery than has been reported previously.

Early estimation of left ventricular systolic pressure and prediction of successful aortic constriction in a mouse model of pressure overload by ultrasound biomicroscopy

Elevation of left ventricular end-systolic pressure (LVESP) and hypertrophic response in mice varies after transverse aorta constriction (TAC). Micromanometric catheterization, conventionally used to select mice with successful TAC, is invasive and nonreusable. We aimed to establish noninvasive imaging protocols for early estimation of successful TAC by ultrasound biomicroscopy (UBM). Out of 55 C57BL/6J mice, we randomly selected 45 as TAC group and 10 as controls. UMB was performed before TAC and, at day 3 and day 14, after TAC. In all mice, LVESP was measured with a Millar conductance catheter at day 14. With LVESP ≥ 150 mm Hg set as indicator of successful TAC (TAC+) and LVESP < 150 mm Hg as unsuccessful (TAC-), receiver operating characteristic curve analysis demonstrated that postoperative inner diameter at aortic banding site (IDb), peak flow velocity at aortic banding site (PVb) and peak flow velocity of right/left common carotid artery (PVr/l) at day 3 served as most effective predictors for LVESP at day 14 (area under curve = 0.9016, 0.9143, 0.8254, respectively. p < 0.01 for all). Among all UBM parameters at day 3, IDb, PVb, right common carotid artery peak flow velocity (PVr) and PVr/l correlated best with LVESP at day 14 (R(2) = 0.5740, 0.6549, 0.5208, 0.2274, respectively. p < 0.01 for all). Furthermore, IDb, PVb, and PVr/l at day 3 most effectively predict long-term cardiac hypertrophy, using the cut-off values of 0.45 mm, 2698.00 mm/s, 3.08, respectively. UBM can be a noninvasive and effective option for early prediction of successful TAC.

Initial and six-year results of stent implantation for aortic coarctation in children

Although stenting has been used as a treatment option for aortic coarctation (CoA) at increasingly younger ages, limited information is available on the long-term follow-up of stent implantation for CoA in pediatric patients. A total of 74 patients with CoA (mean age 8 ± 3 years) underwent stent implantation; 42 were treated for isolated native CoA and 32 for recurrent CoA. A total of 87 stents were implanted (bare metal stents in 71 patients and covered stents in 3 patients). Redilation of a previously implanted stent was performed in 32 patients. Immediately after stenting, the peak systolic pressure gradient decreased from 68 ± 16 mm Hg to 8 ± 5 mm Hg (p <0.05), and the CoA diameter increased from 5 ± 3 mm to 16 ± 3 mm (p <0.05). The most important procedural complication was aneurysm formation in 1 patient that was successfully treated with implantation of a covered stent. No early or late deaths occurred and no evidence was found of late aneurysm formation during a follow-up period of 6 years. Late stent fracture was observed in 3 patients. At the end of follow-up, no cases of recoarctation were identified on multislice computed tomography or magnetic resonance imaging, and 67 (85%) of the 74 patients were normotensive, receiving no medications. In conclusion, stent implantation is an effective and safe treatment alternative to conventional surgical management for the treatment of CoA in selected pediatric patients.

Use of covered Cheatham-Platinum stent as the primary modality in the treatment for native coarctation of the aorta

BACKGROUND

Bare stent implantation in the treatment for native and recurrent coarctation of the aorta (CoA) has become established as an alternative to surgery and balloon angioplasty. However, this modality still encounters significant complications during the procedure and/or follow-up. The covered Cheatham-Platinum (CP) stent commonly used to be chosen as a rescue treatment in these patients. The purpose of this study was to evaluate the use of covered CP stent as the primary modality in the treatment for native CoA.

METHODS

Twenty-five covered CP stents and 2 bare CP stents were implanted in 25 patients with native CoA. All patients after the intervention were invited for follow-up examinations.

RESULTS

The peak systolic gradient across the lesion decreased significantly from a median value of 67.5 mmHg (quartile range, 19.3 mmHg) to 2 mmHg (quartile range, 4.0 mmHg) (P < 0.0001). Stenotic segment diameter increased from a median value of 5.0 mm (quartile range, 1.5 mm) to 17.9 mm (quartile range, 2.5 mm) (P < 0.0001). The median ratio of diameter of the coarctation postprocedure to preprocedure was 4.2 (quartile range, 1.6). All of the CP stents were placed in the suitable position without any acute complications. During a follow-up period of up to 72 months, no complications were encountered. Most of the patients (21/25) were normotensive, apart from four patients requiring antihypertensive medication during the follow-up.

CONCLUSION

The implantation of covered CP stent as the primary modality is safe and effective in the treatment for native CoA in adolescents and adults.

Midaortic syndrome in a premature infant

Hypertension is an unusual finding in premature infants and warrants an extensive workup. Well-known causes of hypertension include endocrine, renal and cardiac anomalies. Coarctation of the thoracic aorta, a well-recognized cardiac anomaly leading to hypertension can manifest at various ages including the newborn period. In contrast, midaortic syndrome (MAS), also known as midaortic dysplastic syndrome, is a rare clinical syndrome involving hypoplasia of the abdominal aorta (AA) 1 with varying degrees of narrowing of the visceral branches, often presenting as intractable hypertension. Though there are case reports describing this condition in older children and adults, the diagnosis of MAS can be extremely difficult in neonates, especially in preterm low-birth-weight infants. We describe a rare case of a premature infant who presented with congestive heart failure in utero and intractable hypertension postnatally. This is the youngest reported case of MAS with autopsy confirmation in the literature.

Hypertension in adult after operation of aortic coarctation

AIM

The benefit of coarctation repair on the resolution of systolic hypertension in adults has been questioned.

METHODS

Between March 1997 and July 2009, 65 consecutive adult patients (≥ 16 years) underwent repair of aortic coarctation. There were 40 men (65%) and 25 women (35%) with a mean age of 22.3 ± 4.8 years (range, 16 to 34 years). All patients had critical systolic blood hypertension (SBP ≥ 140 mmHg). SBP ranged from 140 to 205 mmHg, with a mean of 163.5 ± 17.6 mmHg. The mean diastolic BP was 95.1 ± 18.3 mmHg (range, 70 to 120 mmHg). Most patients (41/65, 74%) were on a regimen of at least one antihypertensive drug.

RESULTS

The patients were followed up after coarctation repair for 2 to 144 months (mean, 68 ± 39 months). There was no death. No other major complications occurred. There have been no repeat interventions during follow-up. Four patients were lost to follow-up. Of the 61 patients with preoperative hypertension, 53 (87%) were normotensive (SBP <140 mmHg) at the most recent follow-up visit. The remaining eight patients showed substantial improvement versus the preoperative status. The mean SBP after operation was 122.5 ± 12.4 mmHg. Mean diastolic blood pressure was 79.5 ± 11.6 mmHg. Forty-one (67%) patients were taking no medication at the last follow-up.

CONCLUSION

Surgical repair of coarctation of the aorta in adults can lead to regression of systolic hypertension and a decreased requirement for antihypertensive medication.

Coarctectomy combined with an interdigitating arch reconstruction results in a lower incidence of recurrent arch obstruction after the Norwood procedure than coarctectomy alone

OBJECTIVE

Recurrent aortic arch obstruction after the Norwood procedure continues to be a source of morbidity. We sought to determine if a modified interdigitating technique for aortic arch reconstruction during the Norwood procedure decreased recurrent arch obstruction.

METHODS

A total of 142 consecutive infants undergoing the Norwood procedure were divided into groups according to surgical technique: Group 1 (n = 79, January 1999 to May 2003) underwent arch reconstruction with complete coarctectomy followed by anastomosis of the descending aorta to the transverse arch. Group 2 (n = 63, June 2003 to September 2006) underwent complete coarctectomy plus a modified interdigitating technique. Catheterization before stage 2 palliation was reviewed for hemodynamics and angiographic arch dimensions, and a coarctation index was calculated.

RESULTS

Reintervention for recurrent coarctation occurred in 28% (22/79) of group 1 patients compared with 2% (1/63) of group 2 patients (P = .001). Aortic pressures, gradients, dimensions, and coarctation index were consistently more favorable for group 2.

CONCLUSIONS

Coarctectomy plus an interdigitating arch anastomosis was superior to coarctectomy alone and resulted in a dramatically decreased incidence of recurrent arch obstruction.

Contribution of nitric oxide synthase (NOS) activity in blood-brain barrier disruption and edema after acute ischemia/reperfusion in aortic coarctation-induced hypertensive rats

BACKGROUND

Nitric oxide synthase (NOS) activity is increased during hypertension and cerebral ischemia. NOS inactivation reduces stroke-induced cerebral injuries, but little is known about its role in blood-brain barrier (BBB) disruption and cerebral edema formation during stroke in acute hypertension. Here, we investigated the role of NOS inhibition in progression of edema formation and BBB disruptions provoked by ischemia/reperfusion injuries in acute hypertensive rats.

METHODS

Rats were made acutely hypertensive by aortic coarctation. After 7 days, the rats were randomly selected for the recording of carotid artery pressure, or regional cerebral blood flow (rCBF) using laser Doppler. Ishcemia induced by 60-min middle cerebral artery occlusion (MCAO), followed by 12-h reperfusion. A single i.p. dose of L-NAME (1 mg/kg) was injected before MCAO. After evaluation of neurological disabilities, rats were slaughtered under deep anesthesia to assess cerebral infarction volume, edema, or BBB disruption.

RESULTS

A 75-85% reduction in rCBF was occurred during MCAO which returned to pre-occluded levels during reperfusion. Profound neurological disabilities were evidenced after MCAO alongside with severe cerebral infarctions (628 ± 98 mm3), considerable edema (4.05 ± 0.52%) and extensive BBB disruptions (Evans blue extravasation, 8.46 ± 2.03 mug/g). L-NAME drastically improved neurological disabilities, diminished cerebral infarction (264 ± 46 mm3), reduced edema (1.49 ± 0.47%) and BBB disruption (2.93 ± 0.66 mug/g).

CONCLUSION

The harmful actions of NOS activity on cerebral microvascular integrity are intensified by ischemia/reperfusion injuries during acute hypertension. NOS inactivation by L-NAME preserved this integrity and diminished cerebral edema.

Vascular remodeling in adults after coarctation repair: impact of descending aorta stenosis and age at surgery

Background

Patients after successful repair of coarctation of aorta (CoAo) are at risk of hypertension at rest and associated end-organ damage. The aim of the study was to assess arterial stiffness and function in adults after coarctation repair in relation to descending aorta (AoD) residual coarctation and patient’s age at operation.

Methods

85 patients after CoAo repair (53 males) aged 34.6 ± 10.3 years; median age at operation 0.9 ± 8.2 years. The control group—30 individuals (18 males) at mean age 33.6 ± 8.2 years. The following central parameters: augmentation pressure (AP) and augmentation index (AI) as well as peripheral vascular parameters: flow-mediated dilatation (FMD), nitroglycerin-mediated vasodilatation (NMD), intima-media thickness (IMT) and pulse wave velocity (PWV) were measured.

Results

47 CoAo-repaired patients were normotensive, and compared to control, they presented higher values of central parameters AP (7.3 ± 4.6 vs. 4.4 ± 3.6 mmHg; p = 0.002) and AI (18.6 ± 10.4 vs. 13.5 ± 4.3%; p = 0.03); as well as the increased PWV (6.8 ± 1.2 vs. 5.4 ± 0.9 m/s; p = 0.003), while IMT was comparable (0.53 ± 0.01 vs. 0.51 ± 0.01 mm; p = 0.06). The vasodilatation was impaired in the normotensive patients: FMD (4.8 ± 2.8 vs. 8.5 ± 2.3%; p = 0.00003) and NMD (11.3 ± 4.6 vs. 19.8 ± 7.2%; p = 0.00001). The comparison of recoarctation (46, 54%) to non-recoarctation (39, 46%) patients did not reveal any significant differences in resting systolic and diastolic pressures, as well as the values of AI and the peripheral vascular parameters; the value of AP was higher in the recoarctation patients (10.5 ± 6.9 vs. 7.5 ± 4.1; p = 0.02) and correlated positively with the gradient across AoD (r = 0.295, p = 0.01). There was no significant linear correlation between age at the time of surgery and any of peripheral arterial parameters.

Conclusions

Residual stenosis in AoD does not affect the arterial vasodilatation nor stiffness in patients after CoAo repair. Early operation has no impact on peripheral vascular remodeling or central pressure which supports the claim that coarctation of the aorta is a systemic vascular disorder which leads to progressive vascular and end-organ damage despite early correction.

Left ventricular and ascending aortic function after stenting of native coarctation of aorta

Patients with surgically corrected aortic coarctation have increased proximal aortic stiffness that might contribute to the known worse cardiovascular outcomes. We examined the effect of stenting on the mid-term ascending aortic elastic properties and its relation to cardiac structure and function in adults with native coarctation of the aorta. A total of 20 consecutive patients (13 men, age at stenting 30 + or - 8 years) were prospectively studied before and 14 + or - 2 months after coarctation stenting. The aortic stiffness index was calculated using the ascending aortic diameters and right arm blood pressure values. The ventricular long-axis function was assessed using pulsed-wave tissue Doppler imaging at the septal site. The results were compared to those from 31 normal controls. Statistically significant improvement was found in aortic narrowing (catheter-derived gradient 32 + or - 11 vs 10 + or - 6 mm Hg), left ventricular mass index (132.8 + or - 50.1 vs 114.7 + or - 47.7 g/m(2)), long-axis function, and left atrial volume index (26.5 + or - 5.3 vs 23.7 + or - 5.6 mm(3)/m(2)). The patients continued to have a thicker left ventricle, reduced long-axis function, and larger left atrium after intervention than did the controls. They also had impaired proximal aortic function with respect to the controls that remained unchanged after stenting (aortic stiffness index 10.7 + or - 4.5 to 10.1 + or - 3.0). The poststenting aortic stiffness index correlated modestly with the left ventricular mass index and reduced long-axis velocity. In conclusion, aortic stenting resulted in partial mid-term improvement in cardiac structure and function in adults with coarctation of aorta but the ascending aortic elastic properties remained abnormal. Such a degree of impairment was related to residual left ventricular hypertrophy and dysfunction. Early identification of such patients and optimum management might avoid these irreversible ventriculoaortic disturbances and their known consequences.