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Cardiovascular magnetic resonance assessment of adults late after an atrial redirection operation for transposition is demanding and time consuming. We hypothesised that the relatively fast and standardised 3-dimensional time-resolved contrast-enhanced magnetic resonance angiography, or dynamic angiography, would be valuable in the periodic follow-up of these patients.
We investigated prospectively 36 adults with transposition using dynamic angiography, comparing our results against a comprehensive but non-contrast cardiovascular magnetic resonance protocol. We acquired 6 dynamic angiographic datasets after injection of contrast. The primary aim was to detect significant obstruction of the pathways for venous flow.
In 4 patients (11%), we found evidence of moderate-to-severe, and thus clinically important, obstruction of systemic venous channels on standard cardiovascular magnetic resonance. All these patients were correctly identified by dynamic angiography. In 4 additional patients, we found mild and haemodynamically insignificant obstructions in the systemic venous channels. Of the 8 (22%) patients with any obstruction, 6 were detected by angiography. There were no false positives reported, giving sensitivity of 75% and specificity of 100%, a positive predictive value of 100%, and negative predictive value of 93%. In 1 patient, there was a moderate obstruction of the pulmonary venous compartment which was not readily seen by dynamic angiography.
3-dimensional dynamic angiography is a useful method for detecting anatomically moderate-to-severe, but not mild, obstructions in the systemic venous channels following Mustard repair for transposition. This technique can be used as a single imaging method and/or as complimentary to standard two dimensional cardiovascular magnetic resonance techniques for detection of clinically important obstructions in the systemic venous channels.
Magnetic resonance velocity mapping of intraaortic flow was performed prospectively in adolescents and adults after coarctation repair. The aims were to assess the feasibility and clinical usefulness of the technique in this patient group, and to study flow velocity distributions in repaired regions. Twenty consecutive patients attending for follow-up after repair of aortic coarctation, aged 15–39, mean 25 years, were studied using a 0.5 tesla Picker magnetic resonance machine. Spin echo and cine imaging with phase velocity mapping, echo time 3.6 ms, were used to study anatomy and flow in the repaired region. Transcutaneous ultrasonic examination, with continuous wave Doppler velocity measurement was performed independently on the same day. Velocity maps, acquired successfully in all patients, showed asymmetry and nonhomogeneity of flow in relation to anatomical distortions of repaired regions. Magnetic resonance and Doppler measurements of peak velocity compared as follows: n=20, range 1.2–3.9 m/sec, mean 2.33 m/sec, mean of differences (Doppler-MR) 0.22 m/sec, standard deviation of differences ±0.27 m/sec. Localized velocity peaks adjacent to wall deformations were identified by magnetic resonance in five patients without significant restenosis. Magnetic resonance imaging with velocity mapping proved reliable and informative in follow-up assessment in adolescents and adults after surgical repair of aortic coarctation. There was satisfactory agreement between magnetic resonance and Doppler measurements of peak velocity. Velocity maps showed that localized velocity peaks may occur in limited parts of the stream adjacent to distorted aortic boundaries without stenosis. This could be a cause of overestimation of pressure gradients from peak velocity data, a possibility which requires further investigation.