[Evaluation of efficacy and mechanism of action of angioplasty and directed atherectomy assisted by intravascular ultrasonography].

Intravascular ultrasound (IVUS) is a unique method of coronary lumen visualization enabling also examination the structure of the artery wall. Aim of this study was to assess efficacy and mechanisms of action of balloon angioplasty (PTCA) and directional atherectomy by means of IVUS. IVUS examination was performed before and after mechanical revascularization procedure in 37 pts (DCA-19 pts, PTCA-18 pts). Both PTCA and DCA resulted in enlargement of the coronary artery lumen (2.29 +/- 1.19 mm2 vs 2.93 +/- 1.55 mm2) but, also external diameter of the vessel increased after the procedure (1.94 +/- 1.10 mm2 and 0.74 +/- 1.01 mm2 retrospectively). In 55.6% of cases after PTCA plaque rupture or artery wall dissection was observed, mainly in eccentric lesions (70%). IVUS allowed to recognize details of artery lumen and define efficiency of procedure. In about 15% cases decision to continue PTCA or DCA was made on the basis of IVUS images only. The mechanism in which PTCA modifies the artery lumen is diverse and depends on the structure of lesion. Factors possibly responsible for enlargement of the lumen are: stretching, squeezing and translocation of atheroma as well as cracking and dissections along the arterial wall. DCA effectiveness depends on the withdraw of the atheromatous deposit, however, in over one-half of cases also stretching has some effect.