Comparison between proximal thoracic vascular measurements obtained by contrast-enhanced magnetic resonance angiography and by transthoracic echocardiography in infants and children with congenital heart disease

Transthoracic Echocardiography in the Preoperative Assessment of Newborn Coarctation: Limiting Risks Associated with Advanced Imaging Techniques

A newborn male child with prenatally identified aortic arch hypoplasia presented to our facility for cardiac management. He had been started on prostaglandins at the delivery facility and was subsequently placed on a high-flow nasal cannula due to associated apnea. On the day of life three, the patient underwent cardiac computed tomography scan for delineation of his anatomy. The patient remained intubated after his imaging study in anticipation of surgical intervention, which took place at the age of 5 days. The patient required a peritoneal dialysis catheter placement 2 days after his procedure due to oliguria. He progressed into renal failure requiring continuous renal replacement therapy. This patient was subsequently discussed at our departmental morbidity and mortality conference. The short time frame between contrast administration for the computed tomography and surgical intervention was thought to have contributed to his renal failure. We discussed the adequacy of transverse aortic arch imaging by echocardiogram and the utility of advanced imaging in the fragile neonatal period. This discussion resulted in our department asking, "Is transthoracic echocardiography accurate when diagnosing and characterizing aortic coarctation at our institution? Are advanced imaging studies necessary in instances of simple coarctation?"

Proximal Pulmonary Artery Evaluation in Infants With Shunt-Dependent Pulmonary Blood Flow: Computed Tomographic Angiography Versus Transthoracic Echocardiography

Background:

Infants with shunt-dependent pulmonary blood flow are at risk for developing proximal pulmonary artery (PA) stenosis, which may result in morbidity and mortality. Transthoracic echocardiography (TTE) is the primary means of surveillance for PA narrowing but has significant limitations and has not been compared to computed tomographic angiography (CTA)–derived measurements of the proximal PA anatomy in this population.

Methods:

A retrospective chart review identified infants with shunt-dependent pulmonary blood flow who had both TTE and CTA performed <14 days apart during a five-year period. Proximal right pulmonary artery (RPA) and left pulmonary artery (LPA) diameters were measured by TTE and CTA. Pulmonary artery z-score, linear and intraclass correlation (ICC) coefficients, and Bland-Altman plots were computed.

Results:

Seventeen pairs of studies were analyzed. The TTE and CTA proximal PA diameters had moderate linear correlation and agreement ( R = 0.67, P ≤ .0001, ICC = 0.65); the RPA showed stronger correlation and agreement ( R = 0.76, P = .0004, ICC = 0.72) than the LPA (R = 0.59, P = .01, ICC = 0.59). Computed tomographic angiography detected missed PA stenosis ( Z score < −2) in five (14.7%) cases, four of which were on the LPA.

Conclusion:

In this study of infants with shunt-dependent pulmonary blood flow, TTE and CTA proximal PA diameters had only moderate correlation and agreement overall, which was worse when comparing LPA measurements. This resulted in missed PA stenosis by TTE. Computed tomographic angiography may be warranted in patients with poorly visualized PAs by TTE or suspicion for deficient pulmonary blood flow.

Combined blood pool and extracellular contrast agents for pediatric and young adult cardiovascular magnetic resonance imaging

BACKGROUND

A comprehensive cardiac magnetic resonance (cardiac MR) study including both late gadolinium enhancement (LGE) and MR angiography may be indicated for patients with a history of acquired or congenital heart disease.

OBJECTIVE

To study the novel use of an extracellular agent for assessment of LGE combined with a blood pool contrast agent for detailed MR angiography evaluation to yield a comprehensive cardiac MR study in these patients.

MATERIALS AND METHODS

We reviewed clinical cardiac MR studies utilizing extracellular and blood pool contrast agents and noted demographics, clinical data and adverse events. We rated LGE image quality and MR angiography image quality for each vascular segment and calculated inter-rater variability. We also quantified contrast-to-noise ratio (CNR).

RESULTS

Thirty-three patients (mean age 13.9 ± 3 years) received an extracellular contrast agent (10 gadobenate dimeglumine, 23 gadopentetate dimeglumine) and blood pool contrast agent (33 gadofosveset trisodium). No adverse events were reported. MRI indications included Kawasaki disease (8), cardiomyopathy and coronary anatomy (15), repaired congenital heart disease (8), and other (2). Mean LGE quality was 2.6 ± 0.6 with 97% diagnostic imaging. LGE quality did not vary by type of contrast agent given (P = 0.07). Mean MR angiography quality score was 4.7 ± 0.6, with high inter-rater agreement (k = 0.6-0.8, P < 0.002). MR angiography quality did not vary by type of contrast agent used (P = 0.6).

CONCLUSION

Cardiac MR studies utilizing both extracellular and blood pool contrast agents are feasible and safe and provide excellent-quality LGE and MR angiography images. The use of two contrast agents allows for a comprehensive assessment of both myocardial viability and vascular anatomy during the same exam.

Thoracic aorta 3D hemodynamics in pediatric and young adult patients with bicuspid aortic valve

BACKGROUND

To evaluate the 3D hemodynamics in the thoracic aorta of pediatric and young adult bicuspid aortic valve (BAV) patients.

METHODS

4D flow MRI was performed in 30 pediatric and young adult BAV patients (age: 13.9 ± 4.4 (range: [3.4, 20.7]) years old, M:F = 17:13) as part of this Institutional Review Board-approved study. Nomogram-based aortic root Z-scores were calculated to assess aortic dilatation and degree of aortic stenosis (AS) severity was assessed on MRI. Data analysis included calculation of time-averaged systolic 3D wall shear stress (WSSsys ) along the entire aorta wall, and regional quantification of maximum and mean WSSsys and peak systolic velocity (velsys ) in the ascending aorta (AAo), arch, and descending aorta (DAo). The 4D flow MRI AAo velsys was also compared with echocardiography peak velocity measurements.

RESULTS

There was a positive correlation with both mean and max AAo WSSsys and peak AAo velsys (mean: r = 0.84, P < 0.001, max: r = 0.94, P < 0.001) and AS (mean: rS  = 0.43, P = 0.02, max: rS  = 0.70, P < 0.001). AAo peak velocity was significantly higher when measured with echo compared with 4D flow MRI (2.1 ± 0.98 m/s versus 1.27 ± 0.49 m/s, P < 0.001).

CONCLUSION

In pediatric and young adult patients with BAV, AS and peak ascending aorta velocity are associated with increased AAo WSS, while aortic dilation, age, and body surface area do not significantly impact AAo hemodynamics. Prospective studies are required to establish the role of WSS as a risk-stratification tool in these patients.