The impact of untreated coronary dissections on acute and long-term outcome after intravascular ultrasound guided PTCA

Aim: Vessel size adapted PTCA results in the use of larger balloons with an increased incidence of severe vascular dissections. The aim of our trial was (a) to evaluate the effect of severe dissections on the acute outcome and (b) to study the natural history of dissections after 1 year.

Methods and results: One hundred and seventy-eight patients with 195 lesions underwent vessel size adapted PTCA using intravascular ultrasound. Clinical and angiographic 1 year follow-up was obtained for all patients. Intravascular ultrasound was performed before PTCA to measure the external elastic membrane diameter at the lesion site so that the balloon size could be adopted (external elastic membrane-10%) and post-interventionally to determine the procedural success and the incidence of intracoronary dissections. Stent implantation was reduced to persistently flow limiting dissections (TIMI I, II). Dissections were detected by intravascular ultrasound in 128/195 (66%) lesions (by angiography in 111/195 [58%] lesions) and classified by intravascular ultrasound criteria into four groups: group I: no dissection (67 lesions [34%]), group II: mild dissections (21 lesions [11%]), group III: medium dissections (19 lesions [10%]) and group IV: severe dissections (88 lesions [45%]). Because of threatened vessel closure, GPIIb/IIIa antagonists were used in eight (4.5%) patients and a stent was implanted in two (1. 1%) patients. The cumulative event rate after 1 year was 12% and the global angiographic restenosis rate was 19%. The post-interventional evidence of severe dissections was associated with a decrease in clinical events during long-term follow up (group I: 13 events [19%] vs group IV: seven events [7%];P=0.03). This was also true for the occurrence of restenosis which was significantly lower in patients with severe dissections (group I: 19 [28%] lesions vs group IV:10 [11%] lesions;P=0.01).

Conclusions: According to the theory of 'therapeutic dissections', our data suggest that substantial dissections following PTCA, which do not diminish antegrade blood flow, do not lead to an increase in acute or long-term events. The natural history of vessel injury seems to provide favourable wound healing without increase of restenosis. Thus, stenting for treatment of large dissections without flow limitation does not seem to be mandatory.