Aortic diameter assessment by cardiovascular magnetic resonance: Do we really need contrast enhanced images?

Background: Cardiovascular magnetic resonance (CMR) is widely used for aortic diameter assessment but there is no consensus on the sequence or cardiac cycle phase in which the measures should be taken. The most used sequence is contrast-enhanced-magnetic-resonance-angiography (angiography), usually non-ECG-triggered. An alternative is a navigated 3D-whole-heart-steady-state-free-precession sequence which is contrast-free and breath- and ECG-gated (mostly diastolic gating), producing very sharp anatomical rendering. Nonetheless, its routine use has not yet spread. Our aim was evaluating aortic diameters by a systolic-gated 3D and put additional effort in the validation of diastolic-gated 3D as alternative to angiography. Methods: We retrospectively analysed 30 patients scheduled for routine Angiography. We measured the aorta at 9 standard positions by three different sequences (angiography, 3D-diastole and 3D-systole) and compared the diameters obtained by calculating the differences and by paired t-test analysis. Results: Diameters by 3D-systole were larger than by 3D-diastole and angiography (P<0.01). In the ascending aorta we found the maximal differences between systole and diastole and between systole and angiography which were 1.7± SD 1.02 mm and 1.5± SD 1.07 mm respectively. There was no significant difference between diastolic and angiography measurements (mean difference 0.2± SD 0.16 mm, P not significant). Conclusions: Our results support the use of navigated 3D-whole-heart CMR to evaluate aortic diameters. Systolic-gated 3D produces larger diameter, especially in the ascending aorta.