Objectives To develop a technique for automatic inflation of a percutaneous transluminal coronary angioplasty (PTCA) balloon, with continuous measurement of the balloon pressure and volume; to validate the technique for determining the mechanical characteristics of coronary arteries.

Results Of the 17 arteries, eight showed elastic, six plastic, and three fracture pressure–volume deformation characteristics. For the plastic deformations, the first inflation required a higher pressure than subsequent repeat inflations of 82 (61) kPa (mean (SD), range 25 to 175 kPa). For the three in the fracture group, the pressure drop because of the fracture occurred between 210 and 540 kPa. Two of these three showed a tear on visual inspection, and the other showed disruption of the intimal plaque on blinded histological examination. Of the six with plastic deformation characteristics alone, one showed a tear, and on histological examination two others showed splitting of the internal and external elastic lamina and one showed separation of intima and media. None in the elastic group showed any of these characteristics.

Conclusions Plastic and fracture deformation characteristics could be differentiated from elastic characteristics. Visual or histological evidence of fracturing was present in all three arteries identified during angioplasty as having pressure–volume fracture characteristics.