Qualitative and quantitative descriptions of the mechanisms of action of angioplasty balloon on coronary stenosis: an endovascular ultrasonic study

The barotrauma induced by inflation of the balloon on an obstructive athero sclerotic plaque induces several distinct, complex effects. The object of t his study was to describe these mechanisms based on endovascular echographi c sections of coronary stenoses before and after balloon angioplasty. The 32 lesions analysed were richly cellular (81.2%) and associated with ca lcifications in 31% of cases. The remodelling index before angioplasty was used to individualise a majority of lesions with chronic arterial constrict ion (56.2%). The modelling of the plaque (dilatation or constriction) had n o effect on the final luminal result. Global analysis of the endoluminal ga in (4.38 +/- 2.28 mm(2)) showed that it was mainly due to reduction of plaq ue surface (78.2% of gain) without prejudging the mechanism, and less due t o expansion of the global arterial surface (21.8% of the gain). The type of remodelling affected the mechanisms of action of balloon angioplasty. Diss ection was present in 53.1% of cases. Fragmentation of the plaque with embo lisation is a common phenomenon (28% of cases). The authors conclude that there are four mechanisms which coexist: 1) Reduc tion of plaque thickness cannot physically correspond to simple compression of tissue, The plaque is redistributed longitudinally. 2) Arterial expansi on only plays a minor part in endoluminal gain. 3) Plaque rupture is direct ly related to the acute increase in wall stress often exceeding the thresho lds of rupture of its components. Finally, 4) embolisation by parietal frag mentation, a mechanism often unknown or ignored which plays an essential pa rt in the potentially deleterious effects.