Clinical Definitions

A variety of parameters are used to describe stenosis and restenosis, especially as a means of quantifying and reporting the efficacy of DES.

A brief review of key terms follows.

Angiographic Binary Restenosis (ABR) also know as Binary Angiographic Restenosis (BAR) is defined as a decrease in lumen diameter of at least 50% anywhere within the target lesion, when a follow-up angiogram is compared to the post-procedure angiogram.

Late loss (LL) is defined as the difference in minimum lumen diameter (MLD) when a follow-up angiogram is compared to a post-procedure angiogram.
In-stent late loss is the MLD within the stent post-procedure minus the MLD at follow-up.
In-segment late loss is the MLD within the stented segment (5 mm proximal + in-stent + 5 mm distal) post-procedure minus the MLD within the stented segment at follow-up.

Late loss index is defined as the ratio between late loss and acute gain.

Major adverse cardiac events (MACE) is a combination of clinical events: death attributed to the heart, Q-wave and non-Q-wave MI, target lesion revascularization (TLR), and emergent CABG.

Percent diameter stenosis (%DS) refers to the fraction of the lumen filled with neointima, as calculated by quantitative coronary angiography (QCA).

Percent (%) volume obstruction uses three-dimensional IVUS assessment to calculate the percent volume of the lumen within the stented segment filled with intimal hyperplasia.

Target lesion revascularization (TLR) is any repeat percutaneous intervention (PCI) of the previously treated lesion, or bypass surgery of the target vessel
Clinically driven TLR occurs when the patient undergoes PCI or bypass surgery due to ischemic signs or symptoms.
Non-clinically driven TLR occurs when the patient undergoes non-emergent revascularization, typically for a diameter stenosis greater than 50% (as determined by QCA).

Target vessel revascularization (TVR) is any repeat percutaneous intervention of a previously treated target vessel, or bypass surgery of the target vessel

Target vessel failure (TVF) is a combination endpoint comprised of TVR + MACE.