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Pathological abnormalities of the pulmonary vein are relatively rare and difficult to diagnose because of restricted echo window or dilution of contrast agent during conventional angiography.1 2 It is usual to distinguish between pulmonary venous stenosis and anomalous pulmonary venous connection of one or more pulmonary veins, which may be associated with other cardiac malformations. Magnetic resonance (MR) imaging offers different advantages because of the wide field of view and multi planar imaging. We report on the use of contrast enhanced magnetic resonance angiography in patients with anomalies of the pulmonary veins.
Between June 1999 and October 2000, six consecutive patients in whom anomalies of pulmonary vein were suspected and/or additional imaging data were required, underwent contrast enhanced MR angiography of the heart. Patient 1 was 8 years old, patient 2 was 13 years old, patient 3 was a neonate, patient 4 was 2 months old, patient 5 was 30 months old, and patient 6 was 10 years old. Before MR angiography, five of them had undergone two dimensional echocardiography, and three had undergone cardiac catheterisation.
All MR examinations were performed after informed consent on 1.5 Tesla imaging system (Vision, Siemens, Erlanghen, Germany) without ECG triggering and breath-holding. The sequence parameters were: time of repetition 3.5 ms; time of echo 1.3 ms; matrix 170 × 250; field of view 300 × 400; one signal acquired. An injection of 0.1 mmol/kg gadopentetate dimeglumine (Dotarem, Guerbet, Villepinte, France) was intravenously administered by means of an injector (Medrad, France). This injection was previously timed by a test bolus of 1 ml of gadolinium to provide maximum contrast material concentration in the vessels of interest during acquisition of central, contrast determining portion of κ space. Acquisitions were performed in coronal and sagittal planes and timed such that the peak gadolinium concentration coincided with the sampling of the central orders of κ space. Acquisition time for three dimensional MR angiography ranged from 22–44 seconds, mean (SD) 28 (10) seconds. The study was displayed as a maximum intensity projection with three dimensional multi planar reformations and was interpreted from source and reformatted images.
All patients tolerated the MR angiography well with no adverse events to the gadolinium. In patients 1 and 2, MR angiography showed partial anomalous pulmonary venous drainage to the superior vena cava with re-routing of the right pulmonary vein to the left atrium in one of them following surgery. In patient 3, MR angiography showed hypoplasia of the right pulmonary artery on axial transverse planes, and demonstrated by coronal projections the existence of a large single pulmonary vein coursing adjacent to the right border of the heart and connected to the inferior vena cava leading to the diagnosis of scimitar syndrome (fig 1). In patient 4 with severe pulmonary hypertension, MR angiography showed all right and left lower pulmonary veins connected to the left atrium but a small signal of the left upper pulmonary vein on transverse and coronal projections. Hypoplasia of this vein was suspected and confirmed on subsequent left upper lobectomy. In patient 5 with a past history of tetralogy of Fallot, MR angiography demonstrated an aneurysm of the left pulmonary artery (20 mm in diameter) and a resultant stenosis of the left lower pulmonary vein repaired at surgery. In patient 6 with pericardial agenesis, MR angiography showed normal connection of the pulmonary veins to the left atrium but a stenosis of the left lower pulmonary vein with flow void on cine-MR imaging probably resulting from the bulging heart.
Recently, a new strategy in MR angiography has been developed to assess the aorta and its branch vessels.3 In fact, such imaging can also be used to image the intracardiac anatomical structures or vessels4 similar to conventional angiography with iodinated contrast agent. This technique overcomes many of the problems that degrade conventional MR angiography by using T1 shortening effect of a dynamic paramagnetic agent such as gadolinium to achieve vessel contrast. Thus, the blood contrast is no longer flow dependent but is directly related to intravascular enhancement from gadolinium chelates and three dimensional data acquisition within the heart and vessels while imaging data are being collected.3
The major advantage of three dimensional MR angiography is to provide images of the pulmonary veins that look like the venous phase of a conventional pulmonary angiogram for clinicians.5 In fact, such imaging is new and can depict a three dimensional perspective of the pulmonary vein connections and course,4 as observed in our patients with partial anomalous venous drainage, but is usually not available with other imaging techniques. Reconstruction in the three dimensions facilitates delineation of such complex anatomy. It is clear that three dimensional MR angiography appears more attractive for clinicians than the in-plane view with classical MR sequences or the projection data obtained from conventional angiography. This could be helpful to plan subsequent surgical correction as observed in the two patients with stenosis/hypoplasia of the pulmonary vein. A second advantage of MR angiography is its short duration, which is clearly less than that of the conventional spin echo technique, allowing its use in infants and young children. In fact the possibility to image such complex anomalies in about 30 seconds without breath-holding is clearly an advantage for use in young children. Other advantages include absence of ionising radiation, safety profile of the paramagnetic contrast agent, and lack of operator dependence.1 3 4
The main limitation of this technique is related to the partial sensitivity and blurring from respiratory and cardiac motion. In fact, image quality is acceptable in most patients and such degradation is mainly related to the absence of breath-holding during data acquisition.1 4 The answer is to perform MR angiography with general anaesthesia in young children and/or to combine it with navigator echo technique.
This study shows that contrast enhanced MR angiography provides an excellent visualisation and three dimensional perspective of pulmonary vein anatomy. Therefore, MR angiography should be used with increasing frequency, even in infancy, as a method to evaluate suspected cases of pulmonary venous anomaly, especially when echocardiography has failed to demonstrate them, while avoiding the need for conventional angiography.