CMR Subanalysis of EXPLORE May Help Pinpoint Which CTO Regions Benefit From PCI

WASHINGTON, DC—Confirming the primary outcome of the EXPLORE trial from a global LV function standpoint, a subanalysis of serial cardiac magnetic resonance imaging (CMR) data also helps to pinpoint which CTO regions may be most likely to benefit from PCI.

The original trial, which was presented at TCT 2015 and published last month in the Journal of the American College of Cardiology, showed that while performing CTO PCI in STEMI patients can improve patient symptoms, it does not improve LVEF or LV end-diastolic volume at 4 months. At the same time, the study showed no harm with regard to MACE in performing the intervention compared with controls who did not receive it. The researchers also found a signal linking CTO location with patients with LAD lesions seeming to respond better to the procedure.

Delving deeper into the location question, José P.S. Henriques, MD (University of Amsterdam, the Netherlands), yesterday at TCT 2016 presented a serial CMR subanalysis of the 180 patients from EXPLORE who underwent these studies.

In terms of global functional recovery, patients with and without CTO PCI were comparable for LVEF as well as LV end-diastolic volume—supporting the primary outcome of the main trial. As for regional segmental recovery, things become “a little more complicated,” according to Henriques.

When analyzing all of the heart regions, segmental wall thickening did differ between the study cohorts at 4 months (P = 0.28), although segmental wall thickening tended to improve among dysfunctional segments in patients who received CTO PCI compared with those who did not (P = 0.06). “Something might be happening there,” Henriques commented.

Among all segments of CTO territories, CTO PCI patients tended to benefit from the procedure (P = 0.09), and this association was even more substantial when dysfunctional segments alone were analyzed (P = 0.03).

Among larger territories like the LAD, “this is even more clearly shown,” in all segments (P = 0.04) and the dysfunctional ones (P = 0.03), Henriques explained. However, he noted that “the numbers are getting lower and lower, and we could not find a functional recovery on global LV function in the LAD, but it shows there is some improvement on the segmental level.” For that reason, these data should only be “hypothesis generating,” Henriques added.

‘Still a Lot to Explore’

Even though CTO on its own has been known to be associated with poorer LV function, he said that “you never know if you modify the marker that you will actually yield an improvement.” One thing this study has helped him realize “is if there is normal segmental wall thickening, then it's unlikely that you will be able to improve LV function during follow-up,” Henriques said. “If you have dysfunctional segments, you'll be able to recover those segments, and that will probably be the segments that will translate to the improvement of global function.”

He postulated that if the original trial had used ischemia-driven primary endpoints “then we may have had a positive [outcome], because ischemia is likely to be reduced because of their successful PCI procedure. But global LV function I think looking back was perhaps not the best endpoint.”

Despite the study’s limitations, it remains “the largest paired CMR data set in the CTO field,” Henriques concluded. “There’s no data at the moment on whether we can find a clinical translation of this improvement in regional function. Perhaps there are other effects. There is still a lot to explore.”