Aims: The aim of this study was to use optical coherence tomography (OCT) to predict newly implanted stent expansion for treatment of in-stent restenosis (ISR).
Methods and results: With OCT guidance, 143 ISR lesions were treated with a new stent. Stent underexpansion was defined as minimum stent area (MSA) <4.5 mm2 and MSA/average of reference lumen area <70%. New stent underexpansion was found in 33 lesions (23%). These had a smaller old stent MSA (4.13 [3.32-4.62] versus 5.18 [4.01-6.38] mm2, p=0.001), and had a higher prevalence of multiple old stent layers (51.5% versus 10.9%, p<0.001) and neointimal or peri-stent calcium (69.7% versus 37.3%, p=0.001) compared to those without new stent underexpansion. Old stent underexpansion, multiple layers of old stent, maximum calcium angle >180°, and maximum calcium thickness >0.5 mm were independently associated with new stent underexpansion. Patients with new stent underexpansion had a higher prevalence of major adverse cardiac events (35.5% vs 14.3%, p=0.009), mainly driven by a higher rate of myocardial infarction and target vessel revascularisation at two years.
Conclusions: When re-stenting an ISR lesion, old stent underexpansion, the amount of neointimal or peri-stent calcium, and multiple old stent strut layers are important determinants of new stent underexpansion which is then associated with adverse long-term outcomes.