Background Medical treatments of coronary myocardial bridging (CMB) have been explored negative inotropic and/or negative chronotropic agents. Nitroglycerin is known to augment vessel wall squeezing. Nicorandil (N-(2-hydroxyethyl) nicotinamide dinitrate) is a hybrid of a nitrate and a potassium channel opener. However, the effect of nicorandil on CMB is unknown. We evaluated the effect of intracoronary nicorandil on CMB. Methods We analyzed nicorandil reactivity at the site with CMB in 11 patients (12 lesions). Maximal and minimal diameters of CMB during a cardiac cycle were measured by quantitative angiography at baseline and at 60 seconds after intracoronary administration of 200 關g nicorandil. Angiographically determined percent vessel narrowing of CMB was calculated as {(end-diastolic diameter – end-systolic diameter)/end-diastolic diameter} X 100. Results The maximal diameter during diastole increased from 2.11짹0.43 mm to 2.42짹0.45 mm after administration of nicorandil (P <0.001), and the minimal diameter during systole increased from 1.23짹0.64 mm to 1.68짹0.65 mm (P <0.001). Thus, nicorandil reduced the percent vessel narrowing from 36.1짹26.5 mm to 20.9짹21.6 mm (P <0.001). Conclusion These results indicate that nicorandil could dilate coronary arteries during diastole as well as systole in patients with CMB. However, precise mechanism of nicorandil on CMB is not known. Further studies are necessary to establish the exact role of nicorandil in therapy of CMB by intravascular ultrasound, intracoronary Doppler ultrasound, and intracoronary pressure devices.

Baseline       Nicorandil          P

Diastolic diameter (mm)           2.11짹0.43      2.42짹0.45       <0.001 Systolic diameter (mm)            1.23짹0.64      1.68짹0.65       <0.001 Percent CMB narrowing           36.1짹26.5      20.9짹21.6       <0.001