Nitrate-induced coronary vasodilation by stress-magnetic resonance imaging: A novel noninvasive test of coronary vasomotion

Abstract

Purpose: To evaluate the feasibility of assessing coronary vasodilation following exogenous nitrates, using magnetic resonance angiography (MRA). The assessment of coronary response to exogenous nitrovasodilators may have a diagnostic and prognostic impact in patients with coronary artery disease. To date, stress imaging of coronary artery vasomotion has been confined to the catheterization laboratory. MRA is emerging as a noninvasive tool for coronary artery imaging. Materials and Methods: Coronary MRA was performed in 20 healthy volunteers (12 males, age = 33 ± 8). We used spiral spoiled gradient echo (SSGE) sequences for imaging of coronary artery lumen. After the baseline short-axis view of the coronary artery was obtained, sublingual nitroglycerin (NTG) (0.3 mg) was administered. In all subjects, shortaxis views of the coronary artery were acquired repetitively (8-10 times) from 1 up to 10 minutes after NTG administration. Measurements were obtained by two independent investigators. Results: Interpretable short-axis view of left anterior descending artery (LAD) was obtained in 15 subjects (75%); in the remaining five subjects the right coronary artery (RCA) was examined. The interobserver variability was 15%, and the intraobserver variability 4%. The NTG-induced maximal vasodilation was 43 ± 22%. The vasodilator response over time after NTG was maximal on average at 279 ± 112 seconds, but with substantial heterogeneity. Conclusion: Entity and time course of nitrate-induced coronary vasodilation in the left anterior descending and/or RCA can be assessed using MRA with high feasibility and reproducibility. Coronary MRA has potential for dynamic imaging of coronary vasomotion.