Optimal revascularisation strategy for left main coronary artery disease

1 - PCI versus CABG : The SYNTAX trial in favour of PCI, but only slightly.

Designed as an “all comers” study, the SYNTAX trial has recently randomised to coronary artery bypass graft (CABG) or percutaneous coronary intervention (PCI) a series of patients with left main or three-vessel coronary disease eligible to both types of treatment. Full results, awaited for 2009, have been already communicated both at ESC and TCT congresses in 2008, and they drew the attention of interventional cardiologists for several reasons.

Although the primary end-point was once more in favour of surgery, in fact, the gap between the two techniques has never been so little. Subgroup analyses revealed specific settings in which the difference is even cancelled, or it is slightly in favour of PCI. The temptation of quoting underpowered subset analyses as the trial result, however, should be avoided. These analyses are only hypothesis generating for future studies, and should not be interpreted as clinically proven facts.

Nevertheless, the SYNTAX trial probably represents to date one of the best tools to face the ongoing dilemma between PCI and CABG. In particular, an interesting issue is regarding the application of the SYNTAX score, a scoring system created ad hoc for this study from the merging of several existing angiographic classifications, to achieve the goal of assigning each patient to the optimal revascularization strategy. Patients with a low or intermediate SYNTAX score seem to be good candidates to PCI.
These findings will probably legitimise an increasing number of percutaneous procedures in the near future by interventional cardiologists who argue the equipoise between PCI and CABG, defined as the substantial uncertainty regarding the relative benefits and risks of these competing treatment options. This opinion is also supported by a recently published systematic review on the comparative effectiveness of PCI and CABG, concluding that survival to 10 years was similar for both procedures (1).

2 - Italian registry

A ) DES associated with higher survival than BMS, benefit concentrated within first year after procedure.

The request of a revision of the current guidelines, which indiscriminately assign a class III indication to PCI, is pushed also by several registries whose results continue to assess the safety of this procedure when drug eluting stents (DES) are employed. However, although previous study on DES use in the context of left main coronary artery disease are available, their interpretation is limited to small individual patients numbers, short duration of follow up and lack of a control group.

A few years ago, the Italian Society of Cardiology started a multicentre, retrospective, observational study on patients with ULMCA stenosis treated with PCI. All interventional affiliated high volume centres, performing > 800 procedures per year in Italy were asked to participate in the survey by providing demographic, clinical, procedural and follow up data on consecutive patients with ULMCA stenosis treated with PCI between January 2002 and December 2006.

Nineteen centres agreed to participate and collected data on 1453 procedures. Such a relevant number represents a new and added value for the outcome analysis of patients undergone to left main PCI and also allows to make specific considerations or generate additional hypotheses with regards to some subgroups of great clinical interest.
Compared to previous studies, patients enrolled in this survey were older and had a higher incidence of acute coronary syndromes and concomitant comorbidities, reflecting the current clinical practice in tertiary care centres and showing the impact of DES versus BMS in the real world.

The analysis of the entire series showed that DES use is associated with a significantly higher survival than BMS use (2). The propensity-adjusted landmark analysis of cardiac mortality showed that the benefit of DES versus BMS was concentrated entirely in the period between PCI and 1 year, while in the period between 1 and 2 years and in the period between 2 and 3 years no significant differences could be observed (Figure 1).

B) One-stent” strategy more beneficial than a “two-stent” one.

Another analysis showed that patients undergoing percutaneous treatment of left main bifurcation seem to benefit more from a “one-stent” strategy than a “two-stent” one (3). This benefit in terms of major adverse cardiac events (MACE) is almost entirely driven by a decrease in the need for revascularization (Table 1). After adjusting for age, gender, hypertension, diabetes, smoking, and other variables, logistic regression analysis showed a significantly lower risk of MACE and cardiac mortality or non fatal myocardial infarction at 2 years in the group that received single stents. In addition, the single-stent strategy was found to be an independent predictor of reduced MACE at 2 years compared with 2 stents.

C) Benefits associated with DES use in patients with acute coronary syndrome and diabetic patients.

A further sub-analysis of patients presenting with acute coronary syndrome demonstrated that in this context DES may be beneficial in reducing the incidence of non fatal reinfarction and target lesion revascularization (63% and 62% relative risk reduction, respectively), with similar rates of cardiac mortality as compared with BMS (4) (Figure 2).
Finally, diabetic patients treated with DES are less likely to undergo repeat revascularization as compared with BMS, and show a similar trend towards death and/or myocardial infarction (5). This is particularly important on the light of current concerns related to the occurrence of late thromboses after DES use and indicates that the overall poorer outcome in diabetics is most likely related to the underlining disease, rather than a specific shortcoming of DES.

Figure 1: Propensity-adjusted hazard ratios of cardiac mortality in patients treated with drug eluting stents (DES) versus those treated with bare metal stents (BMS) between 0 and 1 year, 1 and 2 years and 2 and 3 years. The benefit of DES was concentrated only in the period between percutaneous coronary intervention and 1 year, while no significant differences were observed in the periods between 1 and 2 years and between 2 and 3 years.

Figure 2. Propensity score adjusted actuarial rate of target lesion revascularization at 3 years among patients with acute coronary syndromes who received DES or BMS

Table 1. Survival Free of MACE and Related Endpoints among patients receiving one or two stents for PCI treatment of bifurcation

Conclusion:

Overall, these data suggest that, even if CABG is currently considered the standard of care for most patients with left main stenosis, PCI with DES implantation may be a reasonable alternative in an increasing number of subsets. As for settings where several types of treatment are available, a multidisciplinary team is essential to ensure the highest likelihood that the most balanced advice and best treatment options are offered to patients with left main coronary artery disease.