Two techniques are available to evaluate cardiac function. Cine imaging of the heart creates movie-like displays of the ventricles. Abnormal heart wall motion can be identified by inspection. Measurements of ventricle size during different times during the cardiac cycle allows for quantitative function of the heart. This technique is the gold standard for evaluation of cardiac function. Unlike echocardiography or angiography, the shape of the heart is not important to the accuracy of the measurements. Only magnetic resonance imaging gives a quantitatively accurate evaluation of the right ventricle.

A large atrial septal defect is identified on a short axis cine image.	Enlargement of the right ventricle is demonstrated by a three-dimension model.

Flow analysis is the second technique for evaluating cardiac function. The velocity of blood flow can be tracked using magnetic resonance. The technique is similar to Doppler echocardiography, but has some important advantages. The cross-section of an artery, vein, or cardiac valve can be measured at the same time as the blood velocity allowing for accurate measurements of blood flow. Doppler echocardiography is best performed at an angle from the vessel different from the ideal imaging plane making volume flow measurements impractical. Flow analysis is useful for evaluating stenoses such as coarctation of the aorta and valve regurgitation. Flow analysis is also useful for evaluating shunts and complex surgery such as Fontan operations. The technique can also be used to measure ventricle function.

A three-dimensional image shows the ascending aorta and pulmonary artery.

Flow analysis detected pulmonary regurgitation. A normal flow pattern is present in the aorta (blue), but reversal of flow during diastole is present in the pulmonary artery (red).

In recent years, gadolinium-enhanced magnetic resonance angiography has become important for evaluating vascular disease in adults. Arkansas Children’s Hospital has become a major center for gadolinium-enhanced magnetic resonance imaging in children. The smallest child to date having such an angiogram weighed only 600 grams. The technique allows rapid imaging of arteries and veins with a relatively small peripheral venous injection. No radiation or iodinated contrast is used. In addition to pulmonary artery and aorta evaluation in children with congenital heart disease, the technique has been useful to evaluate acquired abnormalities such as arterial or venous thromboses and vascular malformations.

A three-dimensional gadolinium-enhanced magnetic resonance angiogram clearly identifies a patent ductus arteriosus.

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