An attempt was made to insert a balloon-tipped pulmonary arterial catheter (Swan-Ganz catheter) in a patient in cardiogenic shock during circulatory support by intraaortic balloon pumping, with a right jugular central venous catheter in place. Due to the low cardiac output it was impossible to advance the catheter tip into the pulmonary artery and after several futile attempts it was decided to withdraw the catheter. However, this was impossible because a knot had formed between the central venous catheter and the Swan-Ganz catheter and surgical removal become necessary. This is the first report on intravasal knot formation between two different catheters. This rare complication has to be included in the long list of complications associated with Swan Ganz catheterisation.