A study, simultaneously published in The Lancet at presented at the 2016 American College of Cardiology meeting (2-4 April, Chicago, USA), indicates that delaying stenting—compared with conventional percutaneous coronary intervention (PCI)—in patients with ST-segment elevation myocardial infarction (STEMI) does not reduce the risk of death, heart failure, myocardial infarction, or repeat revascularisation. However, the study investigators claim that ongoing studies may “shed further light” on the concept of deferred stenting.
Writing in The Lancet, Henning Kelbaek (Department of Cardiology, Roskilde Hospital, Roskilde, Denmark) and others report that deferring stenting in STEMI patients has potential advantages. They explain: “Intraprocedural flow reduction (slow or no flow) in connection with primary PCI has been reported in many patients in previous studies, and has been regarded as a strong predictor of long-term mortality. Thus, residual thrombosis might best be left to dissolve during subsequent intensive antiplatelet therapy before stent implantation.” The authors add that data from registry studies have indicated that deferred stenting is associated with “an improvement in angiographic, electrocardiographic, and even clinical outcomes”. Therefore in this open-label, randomised controlled trial, Kelbaek et al aimed to “assess whether deferred stent implantation compared with conventional primary PCI would reduce the risk of jeopardised myocardial vascular flow and improve the clinical course of patients with STEMI.”
In the study, patients presenting with STEMI were randomised to receive deferred stenting (603) or conventional PCI (612). In all patients with angiographic thrombolysis in myocardial infarction (TIMI) flow of 0–1 in the infarct-related artery at presentation, the lesion was wired and thrombectomy and balloon dilation were done if necessary. In patients with TIMI flow of 2–3 at arrival, the use of wiring, thrombectomy, and balloon dilation was at the treating clinicians’ discretion. However, in the deferred stenting group, the recommended protocol, after opening of an occluded artery, was for the coronary guidewire (if inserted) to be retracted and for 10 minutes of observation to assure stability of the lesion before removal of the sheath and intravenous administration of either a glycoprotein IIb/IIa antagonist or bivalirudin for at least four hours after the index procedure. In these deferred stenting patients, repeated coronary angiography was scheduled for about 48 hours after the index procedure. Kelbaek et al note that stenting could be waived altogether if the “infarct-related lesion was deemed stable at the second examination (<30% residual stenosis, no significant thrombus burden, and no visible dissection)”. They add that in such cases, patients would be offered additional control angiography three months after the second examination.
The composite primary endpoint of all-cause mortality, hospital admission for heart failure, recurrent infarction, and any unplanned revascularisation of the target vessel occurred in 17% of the deferred stenting patients and in 18% of the conventional primary PCI (a non-significant difference; p=0.92). There were also no significant differences between groups in the individual components of the primary endpoint—apart from the rate of unplanned revascularisation of the target vessel, which was significantly higher in the deferred stenting group: 7% vs. 4% for conventional PCI (p=0.0345). Kelbaek et al comment that the main cause of this higher rate was “the nearly 2% occurrence of reocclusion or worsening of the culprit lesion before the scheduled PCI”, which they say “provokes concern” because it can “lead to a potentially devastating clinical condition of the patients”. However, they add that the reocclusion rate in the deferred stenting arm “seemed to diminish” during the course of the trial, which they say is “reassuring” and “probably represents a learning curve of the ability to predict whether a reopened infarct-related lesion is stale enough to allow deferral of stent implantation.”
Reviewing why, unlike previous studies, their study failed to show a benefit of deferred stenting, Kelbaek et al note that are several potential reasons for their findings. One of these is that their patients were unselected rather than high-risk STEMI patients and therefore, “we cannot rule out that deferred stent implantation might be more efficient in selected patients”. They add that another— and “probably, most important”—reason was that their study was a randomised controlled trial, “emphasising the limitations often encountered when findings from preliminary single-centre registries or efficacy trials do not translate into real-life clinical practice because of a change in directed attention and assessments applied during the non-randomised trials.”
According to the authors, three ongoing randomised trials are comparing deferred stenting (at various time points after the index procedure) with conventional PCI. They note that one of these studies—PRIMACY—is, like their study, looking at clinical endpoints. “We look forward to the results of ongoing randomised trials, which might shed further light on the concept of deferred stenting in STEMI,” Kelbaek et al conclude.
Kelbaek told Cardiovascular News: “At present a routine strategy of deferred stenting in STEMI cannot be recommended, but diving deeply into the course of selected patients with either completely normalised flow and minimal residual lesions at arrival or with a very high thrombus burden that was not removed by thrombectomy, might reveal subgroups that could potentially benefit from this particular strategy.”