DILATATION MECHANISM OF BALLOON ANGIOPLASTY IN CHILDREN - ASSESSMENT BY ANGIOGRAPHY AND INTRAVASCULAR ULTRASOUND

Purpose: Little information is available about the dilatation mechanis m in children. This prospective study aimed to (1) evaluate the dilata tion mechanism of balloon angioplasty in children with arterial stenos is, and (2) compare the morphological changes seen by intravascular ul trasound (IVUS) and angiography.Methods: Twenty consecutive patients, who had undergone a total of 23 procedures, were examined before and i mmediately after balloon angioplasty with a 4.3 Fr, 30 MHz rotational tip IVUS system. The lesions for IVUS study had resulted from coarctat ion of the aorta in six patients, pulmonary arterial stenosis in five, Blalock-Taussig shunt stenosis in three, subclavian artery stenosis i n two, renal artery stenosis in two, coronary artery stenosis in one a nd ductus arteriosus in one. Results: Four distinctive morphological t ypes were identified: type I with arterial stretching, type IIa with s uperficial tearing, type IIb with deep intimal-medial tearing, type II I with flap formation, and type IV with dissection. The diameter of th e narrowest site before and after balloon angioplasty increased signif icantly from 2.1 +/- 1.4 mm to 4.6 +/- 3.4 mm (p < 0.001). Eighteen of the 23 angioplasty procedures (78%) were considered to be successful, with a dilatation ratio of more than 50%. In most patients with succe ssful dilatation, non-stretch mechanisms such as tearing, flap formati on, or dissection were found. The positive percent (70%) of non-stretc h mechanisms seen by IVUS was significantly higher than the positive f indings (39%) by angiography (X-2 = 6.47, p < 0.02). Conclusions: Non- stretch morphology of the arterial wall may be a common mechanism of d ilatation after balloon angioplasty in children with arterial stenosis . IVUS is a useful modality for evaluating the effectiveness of balloo n angioplasty and the mechanism of dilatation in individual cases.