Influence of Stent Type/Lesion Location and Intravascular Imaging
Stent Type
If PCI is to be undertaken in LMS disease, it is crucial to minimise ISR and thrombosis. A meta-analysis by Pandya et al. comprising 44 studies, showed that DES were associated with a better outcome than BMS.19 The Intracoronary Stenting and Angiographic Results: Drug- Eluting Stents for Unprotected Coronary Left Main Lesions (ISAR LEFT MAIN) trials have compared different types of DES. The ISAR LEFT MAIN study compared the two first-generation DES (Cypher sirolimus-eluting stent [SES] and Taxus paclitaxel-eluting stent [PES]) and showed similar outcomes with both types of stents.20 The ISAR-LEFT MAIN 2 study compared second-generation zotarolimus-eluting stent (ZES) and everolimus-eluting stent (EES) and once a
gain showed similar clinical and angiographic outcomes at 1 year.21 Thus, the types of DES from a similar generation do not seem to influence outcome.
Lesion Location
In an analysis of the Drug-Eluting Stent For Left Main Coronary Artery Disease (DELTA) registry comparing ostial/mid-shaft lesion versus distal lesions, Naganuma et al. demonstrated a higher rate of TLR with distal lesions.22 This primarily drove the higher MACE rates and while there was a trend towards higher mortality and MI, this was not sustained after propensity score matched analysis.
Distal bifurcation lesions present a particularly challenging anatomy to treat. Notwithstanding the increased complexity of such lesions, no technique has been standardised as the technique of choice in LMS bifurcation treatment. In an analysis of the cohort from the ISARLEFT MAIN study, the need for multiple stents was an independent predictor of adverse MACE.23 There seemed to be a better outcome with the use of the Culotte technique as opposed to the T-stent technique with an ISR rate of 21 % and 56 % and a TLR rate of 15 % and 56 %, respectively.
Intravascular Ultrasound
The potential catastrophic consequences of stent thrombosis or restenosis in the context of a treated LMS lesion place an even stronger emphasis on appropriate stent sizing and apposition. The use of intravascular ultrasound (IVUS)-guided PCI in this context has never been formally inve
stigated in an RCT, but data from registries suggest improved outcomes with the use of adjunctive intravascular imaging.
Park et al. compared the use of IVUS-guided treatment of LMS lesions with conventional angiography in the MAIN-COMPARE registry.24 At 3 years, there was a tendency towards improved mortality rates in the former group (6 % versus 13.6 %; P=0.063). This effect was more pronounced in patients who received DES (4.7 versus 16 %; P=0.048).
The Spanish Working Group on Interventional Cardiology (LITRO) study used a pre-specified minimum lumen area (MLA) cut-off of 6 mm2 to determine revascularisation of LMS lesions.25 This was based on Murray’s law assuming an MLA cut-off of 4 mm2 in the left anterior descending (LAD) and the left circumflex (LCX) arteries. Patients with a MLA <6 mm2 underwent revascularisation with over half of the cohort (55.2 %) being treated with CABG while those with an MLA >6 mm2 were managed medically. There was no statistical difference in outcome from the revascularised group versus the medically deferred group (cardiac death-free survival 94.5 % versus 97.7 %, respectively). A cut-off of 4.8 mm2 has been proposed by Kang et al. based on correspondence to a fractional flow reserve (FFR) of 0.8, though this has not yet been clinically validated.26
In an analysis of four Spanish registries, De la Torre et al. found better 3-year outcomes with IVUS-guided revascularisation with a statistically significant reduction in mortality, TLR and MI (88.7 % versus 83.6 %).27 This was even more relevant in a subgroup analysis of patients with distal LMS lesions with better survival rates despite the lower number of patients in that subset.