Background and objectives: Intracoronary ultrasound allows to study in vivo the morphology of the arterial wall, the presence and composition of atheroma and the associated lumen encroachment. The objective of our study was to assess the value of intravascular ultrasound to determine the dilatation mechanism after a conventional balloon angioplasty.
Patients and methods: Sixteen patients were examined with intravascular ultrasound before and after they had undergone percutaneous transluminal coronary angioplasty. A mechanical intravascular ultrasound system was used. Two different types of imaging catheters were used in this study: a 20 MHz, 4.8 F catheter in 5 patients and a 30 MHz, 3.5 F in 11 patients.
Results: Quantitative and qualitative assessments were made from the angiograms and the ultrasound images. Seven out of 16 patients had a calcified plaque, in 8 patients the plaque was fibrotic and in 1 patient soft. Rupture of the plaque was the most common dilatation pattern. Post-PTCA the cross-sectional arterial area was increased from 15.3 +/- 5.2 mm2 to 17.3 +/- 6.2 mm2, the intraluminal area was increased from 2.7 +/- 2.5 mm2 to 7.3 +/- 3.4 mm2, and the plaque area was reduced from 12.3 +/- 4.8 mm2 to 9.7 +/- 3.4 mm2. The quantitative analysis showed that the "most frequent dilatation mechanism" found was the reduction of size plaque, an increase in cross-sectional arterial area was present in only 4 patients (25%). The incidence of depth rupture of the plaque was greater in patients with a calcified plaque than in those without (NS).
Conclusions: 1). Intracoronary ultrasound provides a complete description of plaque composition and geometry before and after coronary balloon angioplasty; 2) several morphologic dilatation patterns were found, and plaque tearing was the most common, and 3) increase in luminal area was most frequently due to a reduction in plaque area. Nevertheless an increase in the cross-sectional arterial area was also common, but less important.