In a calf model, heparin coated intra-aortic balloon (IAB) was compared with standard balloon. In group 1, 9 of each IAB type were set to the automatic mode for 15 min, 45 min and 6 hours respectively, while in group 2, 3 of each IAB type were left deflated during 20 minutes to simulate balloon dysfunction. At the end of the procedures, 3 samples of each IAB were analyzed with scanning electron microscopy (SEM) for surface deposits. Macroscopically, the 12/12 heparin coated IAB of both groups and the 9/9 standard IAB of group 1 were free of deposits, whereas the 3/3 standard IAB of group 2 exhibited clot deposits. SEM revealed deposit-free surfaces in the 36/36 heparin coated samples of both groups, while 14/27 standard samples of group 1 (p<0.01 when compared with heparin coated samples) and 8/9 standard samples of group 2 (p = 0.02, same comparison) disclosed blood cells and fibrin deposits. Morphometrically, the proportion of standard sample surfaces covered with deposits, estimated according to a score system (0% = 0; 0.1-25% = 1; 25.1-50% = 2; 50.1-75% = 3; 75. 1-100% = 4), was 0.69+/-0.82 in group 1 (p<0.01 when compared with heparin coated samples) and 1.22+/-0.83 in group 2 (p<0.01, same comparison). Thus heparin coated IAB presents no deposits either after 6 hours of intravascular ballooning or after 20 minutes of stagnation. It seems to be a promising strategy for patients with absolute or relative contraindications to systemic heparinization.