We describe a new diagnostic catheter specifically designed for selective catheterization of the left internal mammary artery via the ipsilateral radial approach. We used this catheter to assess the patency of the distal mammary-left anterior descending coronary artery anastomosis in 30 consecutive patients early after minimally invasive direct coronary artery bypass grafting. The new catheter design allowed easy and fast engagement of the left internal mammary artery leading to optimal vessel opacification in all cases. Angiography revealed graft problems in seven (23.3%) patients, two of whom required anastomosis revision, surgical in one case and with PTCA in the other. No LIMA injury occurred as a result of selective catheterization. Patients with functionally normal anastomosis were discharged on the same day of the diagnostic procedure.