Novel Imaging Modality Used to Assess Effect of Thrombus Aspiration in STEMI

SAN FRANCISCO, CALIF.—Optical frequency domain imaging was capable of detecting and quantifying with high precision remnant thrombi intra-stent post-PCI, according to study results presented at TCT 2011.

The prospective, single blind, multicenter TROFI study, led by Patrick W. Serruys, MD, PhD, of Erasmus Medical Center, Rotterdam, the Netherlands,  used the new optical frequency domain imaging technique (OFDI, Terumo Corporation) to assess the effects of thrombus aspiration in patients with STEMI. The study  included 141 STEMI patients presenting less than 12 hours from the onset of chest pain who were randomized to primary PCI with (n=71) or without (n=70) thrombectomy.

A new, effective imaging tool

Thrombectomy was 100% successful in reaching and crossing lesions.

The imaging technique showed a trend for larger minimal flow area in the thrombectomy arm when compared with the PCI-only arm (see Figure). However, Serruys noted, “the difference of 0.57 mm2 did not reach the predetermined statistical assumption of a difference of 0.72 mm2 that was previously observed in non-randomized historical series.” He suggested that the study may have been underpowered.

The mean flow area, defined by Serruys as “the area which is functionally capable to accommodate flow,” also tended to be larger in the thrombectomy arm, although this was not significant.

Despite randomization, there was a difference in mean and minimum stent area (see Figure). This could either be due to chance in patient selection or the result of non-documented pre-treatment effects of thrombectomy, according to Serruys. “We are currently trying to look at quantitative coronary angiography… [to] see if there was really a difference in lesion size,” he said.

Lastly, results showed that quantitative intra-stent assessment of remnant thrombus cannot discriminate between backward removal or forward embolization of the thrombus.

When moderator Jeffrey J. Popma, MD, of Beth Israel Deaconess Medical Center, Boston, questioned the ability to incorporate physiologic flow into optical frequency domain imaging, Serruys said this is a query to be answered with future research. “We are working on that,” he said. “We are talking about finite analysis to get some notion about flow and gradient, but it’s too early right now.”

Additional study details

Participants in the trial were aged 61 years on average, with 72% male, 46% smokers and 11% diagnosed with diabetes. Participants also had visible stenosis greater than 30% or TIMI flow grade scores of 0 to 2 in de novo lesions. Twenty-one percent of all patients were treated using radial access; thrombectomy patients received less glycoprotein IIb/IIIa inhibitors when compared with the PCI-alone group.