Influence of applying nitroglycerin in whole-heart free-breathing 3D coronary MR angiography

The purpose of our study was to assess the impact of sublingual nitroglycerin (NTG) spray on free-breathing 3D whole-heart coronary MR angiography (MRA).

We compared the timing parameters; measured the lumen diameter of the major coronary arteries; calculated coronary vasodilation, apparent signal-to-noise ratio (SNR), and apparent contrast-to-noise ratio (CNR); and evaluated the image quality on pre- and post-NTG coronary MRA in 15 volunteers. Statistical analysis was performed with p value less than 0.05 considered significant.

The mean trigger delay and optimal acquisition window were shortened significantly and the mean scanning time was prolonged statistically after NTG administration. There was no significant alteration in terms of apparent SNR and apparent CNR. The lumen diameters were significantly larger in coronary MRA post-NTG than in that of pre-NTG, with an average 25.35% +/- 6.51% (SD) increase, and the left circumflex coronary artery (LCX) had slightly lower vasodilation in comparison with the right coronary artery. Image quality scores of 53 (39.3%, 53/135) segments were increased and 15 segments (11.1%, 15/135) decreased after NTG administration, and the remaining 67 segments (49.6%, 67/135) were unchanged.

In general, sublingual NTG is useful for improving visualization of the coronary artery lumen and alleviating the impact of artifact. However, several alterations and disadvantages should be taken into consideration in view of the disturbed assessment of vasodilatory response in the LCX and the impaired quality in a minority of segments after NTG administration. Further studies are needed to evaluate the effect of beta-blockade on eliminating the disadvantages of sublingual NTG.