Coronary CT angiography--a Rosetta Stone for understanding and treating bifurcation lesions?

Despite significant refinements in technique andtechnology, percutaneous coronary interventions (PCI)of bifurcation lesions remains a challenge due toincreased risks of restenosis, stent thrombosis, and pro-cedural complications. Given the frequency (10–20%of PCIs) and associated morbidity of bifurcation inter-ventions, several classification systems have beendevised to characterize these lesions and inform treat-ment strategies. One simple and widely acceptedscheme, the Medina classification, uses angiographicdeterminants of stenosis severity in the proximal anddistal main branch as well the side branch to describebifurcation lesions [1]. While useful, the ability of thisclassification to predict adverse events is modest.Intravascular ultrasound (IVUS) improves the assess-ment of bifurcation lesions, however, its use is limitedin the presence of severe, calcified, and tortuous seg-ments [2]. With the advent and subsequent evolutionof coronary computed tomography angiography(CCTA), there is potential for this technique to assistin this challenging subset of patients. CCTA can gobeyond simple evaluation of coronary stenoses andprovide an evaluation of the extent and severity of cor-onary atherosclerosis. On this basis, the investigatorsof the current study evaluated a modified CCTA-basedMedina classification of bifurcation lesions, which notonly included the standard parameters of this well-known system, but also included an assessment of pla-que burden ( 40% for any plaque and 70% forsevere plaque) in each of the bifurcation segments [3].Additionally, plaque location relative to the carina wasevaluated. This novel classification was retrospectivelyapplied to a cohort of patients that were previouslytreated for acute coronary syndromes who agreed toundergo postprocedural CCTA. All bifurcations with aside branch ostial diameter 1.5 mm and located atleast 10 mm from adjacent branches with sufficientimage quality were included in the analysis. The bifur-cation segments included the proximal and distal mainvessel and side branch, up to a distance of 5 mm awayfrom the bifurcation carina.A total of 66 bifurcations (in 44 patients) were ini-tially considered for evaluation. However, 27 (41%)bifurcations were excluded from the analysis due tosuboptimal image quality, significant calcification,presence of trifurcations, and several cases where morethan one bifurcation was located in proximity to eachother precluding isolation for analysis. The vast major-ity (92%) of bifurcations did not demonstrate signifi-cant angiographic stenosis, resulting in a traditionalMedina classification of 0, 0, 0. However, CCTA dem-onstrated a plaque burden 40% in 82–85% of thesebifurcation segments and a severe plaque burden( 70%) in 8–15% of these bifurcations segments.When considering segments with severe plaque burden,the CT-based Medina classification provided additionalinformation in 7 (18%) cases. Furthermore, the investi-gators noted, as has been previously demonstrated inother CCTA and IVUS studies, that plaque tended tobe located opposite to the flow divider while the carinawas relatively immune to the development of athero-sclerosis.While the results are intriguing, there are severallimitations that require comment. First, this is a retro-spective analysis in a population of convenience. It isnot clear that extrapolating the findings from nontargetbifurcation lesions without significant angiographic dis-ease would be broadly applicable. Additionally, thesample size is small with a significant (41%) numberof bifurcation segments excluded from the analysis,further limiting the impact of the findings. From atechnical perspective, the acquisition of the CCTA