In a calf model, 3 standard and 3 heparin coated intraaortic balloons (IAB) were inserted and left deflated in the descending aorta during 20 min to simulate balloon rupture. At the end of the experiment, the IAB were examined, and 3 samples of each were collected for scanning electron microscopy (SEM) analysis. None of the heparin coated IAB showed any sign of clot or deposit whereas all 3 standard IAB exhibited clots. SEM revealed no deposit on the heparin coated samples while 8 of the 9 standard samples disclosed deposits (p < 0.001). Morphometrically, 16.1+/-21.4% of the surfaces of the standard samples were covered with deposits whereas all the heparin coated samples were free (p = 0.004). The presence of clots on every standard IAB supports the hypothesis that other than local factors of the insertion site can play a role in the vascular complications of IAB. The absence of clots and deposits on the heparin coated IAB suggests a promising role of such devices in circumventing the tendency of clot formation on deflated balloons while avoiding the drawback of systemic anticoagulation.