• Acute myocardial infarction
• Percutaneous coronary intervention

Implantation of bare-metal stents (BMS) in the early 1990s was a milestone in the development of interventional cardiology.1 Stents provided benefits compared with balloon angioplasty alone by reducing the risk of acute vessel occlusion and recurrent ischaemia, and by optimising acute lumen gain and preventing early vessel recoil. A decade later the implementation of drug-eluting stents (DES) has further improved clinical outcomes mainly by substantially reducing restenosis, the Achilles′ heel of BMS. However, because of impaired vascular healing, there was a higher risk of late and very late stent thrombosis (ST) associated with the first-generation DES when compared with BMS. ST is a potentially catastrophic event so the widespread perception that BMS may be safer than DES was initiated and, as a consequence, the frequency of DES implantations substantially decreased around the world.

To overcome the safety concerns of the first-generation DES, newer devices have been developed with new stent platforms and designs, with more biocompatible polymers or without polymers and with new antiproliferative agents. The outcomes after implantation of the second-generation DES have been much better in comparison to BMS and the first-generation DES in terms of efficacy and safety.2 The results achieved with the new-generation DES are so convincing that in a recent review published in the European Heart Journal, the authors conclude: “We suggest that BMS should be honourably retired and added to the history books (…)”.3 They also cite a multicentre, prospective registry in which it has been reported that BMS are still being implanted despite the evidence for better outcomes with DES: large vessel diameter (32.4% of all BMS implantations); ST-segment elevation myocardial infarction (17.7%); reimbursement reasons (9,4%); advanced age (12.4%); planned non-cardiac surgery within the next year (5.5%); concomitant treatment with oral anticoagulants (11.3%); increased bleeding risk, cancer or anaemia (9.5%) and anticipated poor dual antiplatelet therapy (DAPT) compliance (1.7%).4

Unexpectedly for many interventionalists, the NORSTENT study published in 2016 demonstrated that in a cohort of nearly all comers with different presentations: acute myocardial infarction (AMI), unstable and stable angina, new-generation BMS fared nearly as good as DES. After a 5-year follow-up, there were neither significant differences in the primary composite outcome of death from any cause or non-fatal spontaneous myocardial infarction nor differences in the individual end points of death, myocardial infarction, stroke or hospitalisation for unstable angina.5

An area of even more uncertainty regarding which coronary stents are better is in the setting cardiogenic shock (CS) complicating AMI. The data are scarce, controversial, come from mainly small and single centre, observational, non-randomised studies, with only one study analysing a larger cohort of patients thus far. Some of this research has shown the superiority of DES in terms of all-cause mortality, whereas others, in contrary, have shown a trend towards higher mortality with DES.

With this background, we have now new data coming from a German multicentre Intra-aortic Balloon Pump in Cardiogenic Shock II (IABP-SHOCK II) trial, which has proved no survival benefit from the intra-aortic balloon pump use in patients with AMI complicated by CS.6 The purpose of this analysis was to assess outcomes of patients receiving DES compared with BMS and the composite primary endpoint was 1-year mortality or reinfarction. And again the results and conclusions are somewhat astonishing: after adjustment for risk factors, 1-year outcome of patients treated with DES compared with BMS was similar. The decision, which stent to implant, has been left to the discretion of operators and it turned out that BMS were chosen for more morbid, older patients with poorer prognosis in comparison to DES patients.

How to put this important trial into clinical context, how to interpret the outcomes? Will this study have any impact on our clinical practice? Is it a relevant which stent we implant in this subset of patients or it does not matter at all? We do not have more data to answer these important questions right now. Probably BMS protagonists will interpret these data as convincing for choosing BMS and vice versa, DES protagonists will find arguments supporting their point of view.

In our personal opinion, this non-randomised retrospective analysis could not answer the questions mentioned above because there are too many factors, which have not been analysed and taken into account.

First, it is currently unknown how the effects of CS with subsequent vital organ derangement may impact pharmacokinetics and pharmacodynamics of drugs. Several studies have shown that during shock blood flow to gastrointestinal tract, liver and other organs is severely impaired.7 The pharmacokinetic parameters affected by impaired organs include drug absorption, distribution, metabolism and excretion. All these factors in a different way impact different drugs. In our opinion, it is very difficult to draw conclusions having three different antiplatelet drugs and reliable propensity adjustment must be multifactorial and extremely difficult.

Second, there are no data on the use of therapeutic hypothermia in the study population, while it is known that hypothermia has a profound impact on antiplatelet drug’s efficacy,8 and most probably on other drugs as well.

Third, there are no data regarding late ST and DAPT duration. In the study by Iqbal et al, it has been shown that CS is an independent and the most powerful predictor of definite and probable ST (HR 8.3), even more important than lack of DAPT (HR 2.4).9 One of the most important issues that influence the decision which stent to implant in a particular patient, BMS or DES, is DAPT duration and its safety. However, in the setting of CS, some patient-related factors are not readily apparent, (ie, a history of medication non-compliance, need for upcoming non-cardiac surgery, unclear bleeding status, potential need of anticoagulation therapy, etc). These are probably the most important reasons why BMS implantation has been so frequent in the study population. Despite the guidelines recommending DAPT duration for 12 months in patients after acute coronary syndrome independently from the implanted stent type, in case of emergency, the decision about discontinuation of this therapy seems to be easier in patients after BMS implantation. Nowadays, newly developed DES may be an alternative, yet it has not been investigated in CS.

Fourth, there are no other data that might be relevant like the type of antithrombotic treatment (heparin vs bivalirudin), access mode (femoral vs radial), precise stent type, onset and door-to-balloon time, the achievement of full revascularisation or the presence of ST-segment resolution.

In conclusion, there are still more questions than answers regarding the issue of optimal stent for patients with AMI and CS. There is definitely room and need for a future randomised trial having one powerful antiplatelet agent (cangrelor?) in all patients in both arms, one kind of new-generation BMS and DES, similar mechanical circulatory support (MCS) and hypothermia use, similar door-to-balloon times, shock stages and so on. On the other hand, probably prompt and durable revascularisation together with powerful intravenous antiplatelet agent and prompt use of MCS play much more important role than the kind of stent.