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Aim: To assess efficacy of dihydropyridine calcium antagonists nifedipine and amlodipine for prevention of spasm of internal mammary artery after mammary-coronary bypass grafting., Material and Methods: Eighty eight men (age 56,5-/+7.2 years) subjected to mammary-coronary grafting were randomized to 3 groups. Patients of group 1 (n=35) received nifedipine (10 mg t.i.d.), patients of group 2 (n=30) received amlodipine (5 mg o.d.) and patients of group 3 (n=23) did not receive calcium antagonists. The following parameters were studied: mean linear and volume velocity of blood flow, graft lumen diameter, systolic-diastolic index. Dynamics of flow was assessed during 2 weeks after surgery., Results: In nifedipine treated patients blood flow through grafts to posterior interventricular, anterior interventricular, anterior interventricular and diagonal branches rose by 61.2, 37.4, and 102.9%, respectively. In amlodipine treated patients these figures were 103.4, 113.1 and 147.1%, respectively. Treatment with nifedipine was associated with decrease of graft systolic-diastolic index by 20.2, 20.7, 19.9%, respectively, treatment with amlodipine--by 27.3, 20.6, 32.9%, respectively. Lumen diameter of grafts to posterior interventricular, anterior interventricular, anterior interventricular and diagonal branches in nifedipine treated patients increased by 9.5, 17.6, and 7.7%, respectively, in amlodipine treated patients--by 20, 22.7, and 25.9%, respectively. Moreover amlodipine was better tolerated., Conclusion: The first dose of nifedipine and amlodipine increased diameter of mammary-coronary grafts and blood flow through them. Augmentation of these effects which occurred during further use of nifedipine and amlodipine for 2 weeks was milder and more gradual in amlodipine treated patients.