Located in a crucial position, left main coronary artery supplies 75% of the left ventricular myocardium (100% in a left dominant circulation), thus making its disease ominous. It is involved in 3 to 5% of all angiograms and more than 70% stenosis is associated with a poor prognosis with a 3 year survival of only 41%. After the first left main angioplasty done in 1979 by Gruntzig, it was largely abandoned in a short span of time due to a very high mortality rate (up to 9% in elective cases and 50% in acute cases). With the development of newer generation drug eluting stents and improvement in outcomes, it is slowly come into vogue again. This has been supported by the results of SYNTAX and EXCEL trials which have shown equivalence of PCI (percutaneous coronary intervention) to CABG (coronary artery bypass grafting) in patients with syntax score of less than 32.
However, major challenge persist in the form of involvement of left main bifurcation in 80% of the cases associated with a high restenosis and thrombosis rate. Main branch stenting (1 stent approach), provisional stenting and dedicated bifurcation stenting are the 3 options available for tackling the left main bifurcation. However, the best method to approach the bifurcation lesion has remained controversial.
The initial experience from the Nordic bifurcation study, BBC ONE trial and CACTUS trial have shown no advantage of dedicated 2 stent strategy over a provisional one. But the applicability of this data to left main bifurcation remains flawed due to paucity of left main bifurcation cases in these studies. Provisional stenting is limited by the fact that crossover to a 2 stent strategy is required in more than one third of the cases.
Further, rescue or bailout stenting in these cases may be associated with imprecise stent placement, incomplete stent expansion or failure to deliver a stent leading to a poorer outcome as compared to a dedicated 2 stent approach. Of the dedicated 2 stent strategies available (T stenting and protrusion, V stenting, Culotte technique and double kissing (DK) crush technique crush), double kissing crush technique has shown the best results.
DKCRUSH III trial compared DK crush technique with culotte technique applied to left main bifurcation lesions and showed a better 12 month MACE free survival with DK crush (93.8% vs 83.7%, p = 0.001). Recently, DKCRUSH-V trial compared DK crush with provisional stenting in unprotected left main true bifurcation lesions (Medina 1,1,1 or 0,1,1) by randomizing 484 patients to either strategy.
At 12 months, primary end point in the form of target lesion failure was noted in 10.7% patients in the provisional stenting group and 5.0% in the DK crush group [HR 0.46 (CI: 0.23-0.91), p = 0.022). DK crush also resultedin lower rates of target vessel myocardial infarction (2.9% vs. 0.4%; p = 0.03) and definite or probable stent thrombosis (3.3% vs. 0.4%; p = 0.02).
Clinically driven target lesion revascularization (7.9% vs. 3.8%; p = 0.06) and angiographic restenosis within the LM complex (14.6% vs. 7.1%; p ¼ 0.10) also tended to be less frequent with DK crush compared with provisional stenting group. On subgroup analysis, DK crush performed better in both simple and complex bifurcation lesions with the advantage being more in complex bifurcation lesions. The major limitation of the trial include limited use of IVUS, FFR, POT and FKBI in provisional stenting group. Also, it remains important to note that DK crush is a challenging technique and the primary operators in the trial were required to perform at least 300 PCI /year and 20 left main PCI /year for 5 years to be a part of the trial.
To sum up, left main PCI should be attempted by experienced operators at high volume centres. While DK crush is the preferred dedicated 2 stent strategy for true bifurcation lesions, single stent strategy may be used in cases with insignificant left circumflex ostial disease.
The author, Dr. Viveka Kumar is MD – General Medicine, DM(Cardiology ) and is Senior Director – Cath Lab Max Super Speciality Hospital, Saket.He is on Editorial Board of Indian Heart Journal and is also principal investigator and sub-investigator of more than 14 international trials.