Influence of catheter technology and adjuvant medication on acute complications in percutaneous coronary angioplasty. We report on the complication rates in 660 consecutive coronary angioplasties (725 lesions) performed using four procedures that differed with respect to catheter technology and adjuvant medication. After the PTCA regimen in our laboratory had been changed from conventional steerable systems to the monorail technique, we observed a significant increase in the incidence of transient vessel occlusions from 2.6% to 7.7%, of permanent occlusions from 3.6% to 8.8%, and of intracoronary thrombus-formation from 2.6% to 5.5%. This was associated with the frequent observation of thrombotic material on the partially Teflon-coated guidewires. Coronary perfusion with urokinase (1,670-6,670 U/min) lead to a further increase in the complication rates (10.4%/10.3%/6.5%). Our present percutaneous transluminal coronary angioplasty (PTCA)-regimen (monorail technique with P.E.T. balloons, fully silicon-coated guidewires, no urokinase) shows an incidence of 3.8% for intermittent and recurrent coronary occlusions and 1.9% for permanent occlusions. Urokinase did not prevent intracoronary thrombus formation with the monorail technique. Furthermore, we suspect that in the case of PTCA-induced regional intimal dissection, fibrinolysis can prevent reestablishment of intima adherence to the vessel wall. Because five procedural deaths were observed in the 212 patients treated with i.c. urokinase as opposed to three deaths in the 448 procedures without urokinase, we feel that i.c. urokinase in PTCA is a potentially harmful regimen. We suggest that the monorail technique should be performed with fully silicon-coated guidewires and without urokinase. 