Angiographic, echocardiographic, and three-dimensional magnetic resonance imaging of extracardiac conduits in congenital heart disease

A simplified approach for assessment of intracardiac baffles and extracardiac conduits in congenital heart surgery with two- and three-dimensional magnetic resonance imaging

BACKGROUND

Intracardiac baffles and extracardiac conduits have been used in the reconstructive surgery of a broad spectrum of congenital cardiac malformations. Periodic evaluation of these structures may not lend itself readily to echocardiographic and angiographic imaging. The purpose of the study was to describe the experience of our institution with the use of magnetic resonance imaging (MRI) in evaluating conduits and baffles and to describe the simplified approach we developed to image these structures, which allows for grouping individual lesions into broad categories.

METHODS AND RESULTS

We retrospectively reviewed our MRI experience in visualizing these structures from 1989-1996. One hundred thirty-nine patients underwent MRI to visualize 144 structures (116 baffles, 28 conduits). The 116 baffles included 86 Fontan, 16 Mustard, 6 Senning, 6 left ventricle to aorta, 1 right ventricle to aorta, and 1 pulmonary vein to left atrium baffle. The 28 conduits included 15 right ventricle to pulmonary artery, 4 left ventricular apical to aorta, 2 left ventricle to pulmonary artery, 3 aorta to aorta, 2 inferior vena cava to left atrium conduits, and 2 aortic root replacements. Of the 3 aortic-aortic conduits, 1 was in conjoined twins. Both inferior vena cava-left atrial conduits were in a Baffes procedure. An infectious mass missed by echocardiography in a right ventricle to pulmonary artery conduit was visualized by MRI. With multiplanar reconstruction, contiguous images were stacked atop each other and resliced to define the salient points of the anatomy. Three-dimensional reconstruction further added to this delineation. All structures were visualized successfully, and an assessment of obstruction was made. Multiple examples of conduit and baffle narrowing were diagnosed by spin echo and cine MRI and were subsequently confirmed by catheterization and surgical inspection.

CONCLUSION

MRI, with multiplanar and 3-dimensional reconstruction, is useful in examining the variety of baffles and conduits used in congenital heart surgery. MRI can add to the care of patients whose echocardiographic windows or whose angiographically overlapping structures do not allow adequate delineation of conduits and baffles.

Evaluation and follow-up of patients with left ventricular apical to aortic conduits with 2D and 3D magnetic resonance imaging and Doppler echocardiography: A new look at an old operation

BACKGROUND

Although the interposition of left ventricular apical to descending aorta conduits has diminished with the advent of the Ross-Konno operation, it remains a useful option. We reviewed our institutional experience imaging these conduits and tested the hypothesis that the gradient across the native left ventricular outflow tract (LVOT) by echocardiography correlated with the conduit gradient by cardiac catheterization. In a patient with an unobstructed conduit, no gradient should exist across the native LVOT.

METHODS

This was a retrospective review of the echocardiography, cardiac catheterization, magnetic resonance imaging (MRI) data, and history of 9 patients with these conduits over an 8-year period. In 7 of 9 patients, 8 conduit obstruction events were assessed by Doppler interrogation of the native LVOT and by cardiac catheterization. Five patients underwent 6 MRI scans.

RESULTS

In all cases of obstruction diagnosed by catheterization (56.3 +/- 21.9 mm Hg), Doppler echocardiography demonstrated gradients across the native LVOT (69.3 +/- 21.2 mm Hg, r = 0.67). Because 2D echocardiography could not visualize the entire conduit in any patient, 2- and 3-dimensional MRI was used successfully to evaluate anatomy and identify the site of obstruction. All patients manifested conduit obstruction. Four (44%) of 9 patients died, 3 underwent the Ross operation, 1 continues to live with his original conduit, and 1 was lost to follow-up.

CONCLUSIONS

A gradient by Doppler interrogation of the native LVOT is an indirect means of assessing conduit obstruction. MRI is a useful tool to complement anatomic diagnosis by echocardiography. Conduit obstruction is common, and late mortality rates appear to be high.

Postoperative evaluation of congenital heart disease by magnetic resonance imaging

In the last four decades the survival of patients with corrected or palliated congenital heart disease has increased dramatically. However, post-operative abnormalities frequently occur and therefore a noninvasive imaging tool is mandatory for the timely detection of morphological as well as functional abnormalities. Magnetic resonance imaging (MRI) is ideally suited for the noninvasive diagnosis and post-operative follow-up of congenital heart disease. Spin-echo MRI is able to visualize structures that may be difficult to assess with other noninvasive image modalities and is sensitive in the detection of post-interventional stenoses or aneurysms. Because the function of the ventricles may deteriorate over time after correction or palliation of a congenital cardiac malformation, the use of gradient-echo MRI is essential in the follow-up after correction or palliation, as no other conventional technique allows such detailed evaluation of ventricular function, without geometrical assumptions. Phase-contrast MRI is well suited to assess valvular function, allowing accurate measurement of regurgitation or stenosis. Shunt quantification is another application of phase-contrast MRI. J. Magn. Reson. Imaging 1999;10:656-666.

Functional evaluation of extracardiac ventriculopulmonary conduits and of the right ventricle with magnetic resonance imaging and velocity mapping

Extracardiac ventriculopulmonary conduits tend to deteriorate over time, developing both obstruction and regurgitation. In this prospective study, magnetic resonance imaging (MRI) was compared with Doppler echocardiography to determine whether MRI improves the noninvasive evaluation of conduit patients. Twenty-five patients (median age 10 years, range 2.5 to 32) were investigated 27 times with Doppler echocardiography and an MRI protocol with spin echo sequences for morphology, velocity mapping, and multislice gradient echo technique for right ventricular volume measuring. Cardiac catheterization data were available in 6 patients. Echocardiography could assess the morphology of the conduits in 6 patients, whereas MRI demonstrated all conduits efficiently. Doppler echocardiography could evaluate the occurrence of regurgitation in 18 patients and could quantify peak velocity in 20 of the patients. A technically adequate MRI velocity mapping was obtained in 25 patients. There was good agreement between MRI and Doppler echocardiography in establishing or not establishing regurgitation, but Doppler echocardiography was less reliable in evaluating the degree of regurgitation. The correlation between peak velocity determined with Doppler and magnetic resonance imaging was r = 0.63 [corrected]. Correlations between catheterization pressure gradients and noninvasive techniques were r = 0.97 for magnetic resonance imaging [corrected] versus catheterization, and r = 0.86 [corrected] for Doppler versus catheterization. MRI can provide complete information on the morphology and function of extracardiac ventriculopulmonary conduits, as well as of the right ventricle. If the results of MRI and echocardiography with Doppler are in agreement, heart catheterization and angiography can be avoided, even in patients considered for conduit replacement.

MRI and echocardiography: how do they compare in adults?

TTE with color flow imaging remains the most appropriate initial method for imaging CHD in adults. In many patients with minor abnormalities, this will be the only imaging required. For complicated intracardiac anomalies not well shown by TTE, TEE or MRI are usually adequate with the choice of technique being dependent on the availability of appropriate equipment and expertise. For great vessel abnormalities, further evaluation with MRI and MRA is most appropriate. In patients suspected of having significant systemic or pulmonary venous abnormalities or abnormalities of the aortic arch, MRI and MRA should be regarded as the definitive imaging technique. MRI and MRA are robust methods for evaluating intracardiac disease and can provide accurate information on cardiac chamber anatomy relationships, valvar lesions, and shunts. However, in most patients, this information is provided more rapidly and cost effectively by color Doppler echocardiography.

Cardiac MR imaging in congenital heart disease

Magnetic resonance imaging is a unique and insightful tool for the assessment of structure and function in congenital heart disease. For anatomic assessment, the large field of view, lack of limitation by patient size, and ability to create three-dimensional surface displays from routine imaging acquisitions offer several advantages over other modalities. The ability of magnetic resonance imaging to assess the volume and mass of bizarre ventricular shapes accurately and myocardial tissue and blood tagging as well as phase encoded velocity mapping has enhanced research in pediatric cardiology. Newer techniques, such as oxygen-sensitive magnetic resonance imaging and echo-planar magnetic resonance imaging, promise even further advances in research and in clinical applications.