First-of-their-kind imaging studies presented at TCT

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Three imaging studies that were presented as late-breaking trials at the 2014 Transcatheter Cardiovascular Therapy (TCT) meeting (13–17 September, Washington, DC, USA) provided, respectively, the first randomised controlled data for routine use of optical coherence tomography (OCT) guidance during stent placement in patients with ST-segment elevation myocardial infarction (STEMI), the role of intravascular ultrasound (IVUS) in patients with chronic total occlusions, and the use of fractional flow reserve (FFR) for guiding provisional stenting in patients with bifurcation lesions.

Pavel ÄŒervinka (Faculty Hospital Hradee Královè/Masaryk Hospital, Czech Republic) told TCT delegates that large randomised trials with long-term follow-up of OCT in STEMI patients undergoing primary PCI are needed because the OCT STEMI study indicated that OCT has “potential merit” in these patients. He explained the objective of the study was to explore the routine use of OCT in guiding stent implantation during primary percutaneous coronary intervention (PCI) in STEMI patients, noting that it was the first randomised trial to evaluate OCT in this setting.

In the study, 201 patients with STEMI were randomised to undergo angiography-guided primary PCI (105) or OCT-guided primary PCI (96). Patients in the OCT-guided group underwent OCT study after the final optimal angiography. If the OCT result was suboptimal, they also underwent post-OCT intervention (eg. post dilation/further stent implantation). The primary endpoint was the rate of major adverse cardiovascular events (MACE) at 30 days and nine months. Furthermore, all patients underwent OCT at nine months to assess the percentage of uncovered struts, the percentage of area stenosis, the minimum lumen in-stent diameter, and minimum lumen in-stent area.

The overall MACE rate at 30 days and at nine months was low, with no significance differences between the OCT and angiography groups at either of these time points. Furthermore, there no complications related to OCT procedure.

According to OCT analysis, OCT-guided primary PCI was associated with a significantly smaller area stenosis compared with angiography-guided primary PCI (4.4±24 vs. 15.9±21.98, respectively; p=0.0011) and was also associated with a trend towards a lower percentage of uncovered struts (12.8±13.1% vs. 16.8±15.8%, respectively; p=0.07). However, OCT-guided primary PCI was also associated with significantly longer fluoroscopy time (11.2±5.33 minutes vs. 8.3±4.6 minutes for angiography-guided PCI), which ÄŒervinka attributed to “aggressive treatment of dissections”.

He said: “The OCT STEMI trial demonstrates the potential merit of OCT guidance during drug-eluting stent implantation in primary PCI. The study also indicates that the procedure is safe for STEMI and large randomised trials with longer-term follow-up are warranted.”

CTO-IVUS

The CTO-IVUS study was the first randomised trial to examine the clinical impact of IVUS guidance for chronic total occlusions. Presenting the data at TCT, Yangsoo Jang (Division of Cardiology, Severance Cardiovascular Hospital, Yonsei University College of Medicine, Seoul, South Korea) stated that 402 patients with chronic total occlusions were randomised to undergo IVUS-guided intervention (201) or angiography-guided intervention (201). Patients were additionally randomised to receive a zotarolimus-eluting stent (Resolute, Medtronic) or a biolimus-eluting stent (Nobori, Termuo)—the data for this part of the study were not presented at TCT. The primary endpoint was a composite of cardiac death, myocardial infarction, and target vessel revascularisation at 12 months.

The study showed that IVUS-guided intervention was associated with, according to Jang, a “more frequent use of high-pressure post-dilation and larger post-procedural minimum lumen diameter compared with angiography-guided intervention”. Also, the rate of the primary endpoint, at 12 months, was significantly lower in the IVUS-guided group—2.6% vs. 7.1% for the angiography-guided group (p=0.035). This difference was mainly driven by a lower rate of cardiac death or myocardial infarction at one year with IVUS-guided intervention (0% vs. 2%, respectively; p=0.045). There was no significant difference in the rate of target lesion revascularisation between groups: 2.6% for IVUS-guided intervention vs. 5.2% for angiography-guided intervention (p=0.186).

Additionally, the percentage of patients who crossed over from the angiography-guided to the IVUS-guided group was significantly higher than those of the IVUS group who crossed over to the angiography group: 17.4% vs. 2.5%, respectively (p<0.01). Jang reported that based on the per-protocol analysis, the rate of the primary endpoint was still significantly lower in the IVUS group (2.2% vs. 8.4%, respectively; p=0.005). He concluded that IVUS-guided intervention in patients with chronic total occlusions “significantly improved clinical outcomes after drug-eluting stent implantation”.

Jang told Cardiovascular News: “IVUS usage in chronic total occlusions for the wire crossing is highly dependent on operator skill. Therefore randomisation at the beginning of the chronic total occlusions procedure is extremely difficult. In this study, patients were randomised after wire crossing of the chronic total occlusions lesion.”

DKCRUSH-VI

The results of the DKCRUSH-VI study, which was the first study to compare fractional flow reserve (FFR) with angiography for determining the need for provisional stenting in patients with bifurcation lesions, were also presented at TCT (by Shao-Ling Chen; Cardiology and Cath Lab, Nanjing Medical University, Nanjing, China).

Of 320 patients with true bifurcation lesions, 160 underwent FFR-guided intervention and 160 underwent angiography-guided intervention. Similar to the IVUS study, the primary endpoint was the rate of major adverse cardiovascular events (MACE)—including cardiac death, myocardial infarction, and target vessel revascularisation—at one year.

Chen reported that there were no significant differences in the percentage of patients who underwent intervention (balloon or stenting; 56.3% for FFR vs. 63.1% for angiography; p=0.07) or in the rate of MACE at one year (18.1% for both groups; p=1). Furthermore, there were no significant differences in any of the individual components of the MACE endpoints—for example, the rate of cardiac death in the FFR group was 1.3% vs. 0.6% for the angiography group (p=0.56).

According to Chen, as they were associated with similar MACE rates, both FFR-guided intervention and angiography-guided intervention may be recommended for provisional side-branch stenting of a true bifurcation lesion. He said: “The FFR technique may result in somewhat fewer stents being implanted and a slightly lower long-term term restenosis rate [as was shown in this study], but may be technically challenging and require the upfront cost of a pressure wire in all patients.”