Objectives: Intravenous dipyridamole (DP) can induce transient perfusion abnormalities in the heart but also the brain indicated by brain SPECT. L-arginine can regulate the vascular tone via nitric oxide (NO). Therefore, we examined cerebral blood volume (CBV) by perfusion MRI and L-arginine level before and after DP stress in patients, who developed transient neurological signs, and compared these to unaffected patients.
Design: A total of nine patients with ischemic coronary disease after myocardial perfusion scintigraphy were selected for this prospective pilot study. Four had DP-induced transient mild neurologic signs during myocardial perfusion scintigraphy, while five had no neurological signs. By using perfusion MRI in both groups in a second stage, we examined CBV in identical areas of the two hemispheres before and during DP stress. Besides, pre-and post-stress L-arginine serum levels were also analyzed by high-performance liquid chromatography. Trial registration: NCT03688815.
Results: CBV in the sensory-motor area at baseline was significantly higher in patients with DP-induced transient neurological signs compared to patients without signs (p = 0.028). Intravenous DP normalized the higher perfusion by decreasing CBV, and also increased serum L-arginine level (p = 0.001).
Conclusions: Intravenous DP changed the CBV accompanied by a systemic elevation of L-arginine: this indicates a direct vasorelaxing effect on brain vessels, and an indirect vasodilator effect through L-arginine release presumably via NO. In areas with decreased CBV before DP, such double effects caused transient neurological symptoms presumably due to steal phenomenon. Therefore, intravenous DP may have a potential to identify patients with high risk for cerebral ischemia.
Keywords: Dipyridamole; arginine; cerebral blood volume; magnetic resonance imaging; prevention.