TRANSIENT: Treatment Timing Inconsequential When STEMI Resolves Before Revascularization

The delayed and immediate strategies appear “interchangeable,” but outside sources voiced concerns about study limitations.

TRANSIENT: Treatment Timing Inconsequential When STEMI Resolves Before Revascularization

In patients with transient STEMI, where symptoms and ST-segment elevation resolve prior to revascularization, it doesn’t seem to matter whether treatment is immediate or delayed. Both strategies produce similarly good outcomes out to 1 year, new data from the multicenter TRANSIENT trial suggest.

The findings were presented last week at the European Society of Cardiology Congress 2019 in Paris, France, and simultaneously published in JACC: Cardiovascular Interventions.

The TRANSIENT trial enrolled 142 patients with transient STEMI, for whom the best approach to revascularization is still elusive, randomizing them to revascularization at the time of presentation or delayed until the following day (mean 22.7 hours). The vast majority underwent PCI, with only four patients in the delayed group undergoing CABG.

Early data from the trial presented last year at EuroPCR 2018 showed no statistical difference in infarct size as assessed by cardiac MR at 4 days. The latest report extends those findings over the longer term.

“Transient STEMI can be caused by an unstable thrombotic lesion and immediate intervention might limit ongoing infarction,” lead author Gladys N. Janssens, MD (Amsterdam UMC, the Netherlands), and colleagues explain in their paper. “On the other hand, delayed intervention might allow the spontaneous reopened artery to stabilize, potentially preventing harmful distal embolization during PCI.”

Given the ambiguities of managing patients with transient STEMI, the TRANSIENT data are welcome, Robert A. Byrne, MD, and Roisin Colleran, MD (both Deutsches Herzzentrum München, Germany), note in an accompanying editorial. It’s unknown whether STEMI or NSTE ACS protocols are preferred in this situation, they say, “though both US and European guidelines for clinical practice deal with management of this entity in their NSTE ACS guidelines.”

Moreover, Janssens and colleagues note that while the US guidelines recommend performing invasive or noninvasive coronary angiography to detect severe CAD, “no specific reference with regard to timing is given.”

Small, Similar Final Infarct Sizes

In TRANSIENT, repeat cardiac MR at 4 months revealed that average final infarct sizes were small and similar at 0.4% of the LV in both the delayed and immediate groups, and not significantly different from the 4-day scan. Fewer than 5% of patients had an infarct size of 10.0% or greater, with a maximum of 20.8% of the LV noted in one patient randomized to the immediate-invasive group.

LVEF also was similar in the delayed and immediate arms (59.3% vs 59.9; P = 0.63).

At 1 year, rates of MACE were 5.7% in the delayed group and 4.4% in the immediate group (P = 1.00). In all cases, MACE occurred in patients with revascularized culprit arteries and the event rates were equally driven by reinfarction and death. In the delayed-invasive group, three patients died due to pulmonary complications after CABG, aortic aneurysm rupture, and ileus with sepsis. No deaths occurred in the immediate-invasive group. Rates of recurrent MI were 1.4% in the delayed group and 3.0% in the immediate group (P = 0.62), while rates of repeat revascularization were 12.9% and 11.8%, respectively (P = 1.00); three-vessel disease patients were the most likely to need a repeat procedure.

According to Janssens and colleagues, the 1-year TRANSIENT results “support the interchangeability of the two treatment strategies.”

Commenting on the study for TCTMD, Dharam Kumbhani, MD (UT Southwestern Medical Center, Dallas, TX), observed that TRANSIENT confirms that this population, which accounts for a very small subset of those with STEMI, is very low risk. That being said, transient STEMI patients can be difficult to identify. Although Janssens and colleagues attempted to exclude those with severe vasospasm, for example, Kumbhani said it is possible that some of those patients made it into the trial anyway.

“It's a challenging area to study, because it's hard to find people who exactly meet these criteria,” he added.

Methodologic Flaws

Both Kumbhani and the editorialists also note that the study was considerably underpowered. “I'm not sure that them not seeing a difference is the same as being unable to tell that there's actually a difference,” Kumbhani said.

Byrne and Colleran further point out that complications during PCI were numerically higher in the delayed group (7.1% vs 2.0%), as was the rate of microvascular obstruction as assessed at 4 months by cardiac MR (1.9% vs 0%). “Both of these observations speak against the hypothesized benefit of a delayed strategy,” they write.

Another issue is that 22.5% of patients did not undergo the second cardiac MR at 4 years, the editorialists observe. The reasons given by the authors to explain this gap were equal parts patient refusal and claustrophobia. While Byrne and Colleran assert that cardiac MR data are “typically missing not at random,” thus raising implications for the study’s external validity, Kumbhani was more pragmatic. The missing cardiac MR follow-up really is not that unusual, he told TCTMD, since claustrophobia is a common reason many patients give for not wanting to have the test redone.

Byrne and Colleran suggest that a larger, adequately powered trial is now needed. For his part, Kumbhani said while the methodologic shortcomings of TRANSIENT do leave open important questions, thousands of patients fitting strict transient STEMI criteria would be needed to get adequate numbers to power such a trial.

“So, you can look at this two ways. [From one perspective], this is a benign entity and you can sit tight or go in early, and either way you can have good outcomes. Or, you can be a purist and say this trial doesn't inform me that much, but it could help inform future trials,” Kumbhani concluded.

  • Janssens, Colleran, and Kumbhani report no relevant conflicts of interest.
  • Byrne reports receiving lecture fees from B. Braun Melsungen AG, Biotronik, Boston Scientific, and Micell Technologies; and research funding to his institution from Boston Scientific and Celonova Biosciences.

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