No Harm From Thrombolytics in SCAD Patients With STEMI

Individuals with STEMI caused by a spontaneous coronary artery dissection (SCAD) who are treated with intravenous thrombolysis prior to coronary angiography fare no worse in the hospital compared with those not treated with thrombolysis, according to registry results.

Overall, in-hospital outcomes, including all-cause mortality, MI, and cardiac arrest, among other cardiovascular endpoints, were similar in the two groups. That’s important, because intravenous thrombolysis is not recommended, and even contraindicated according to some guidelines, in patients with SCAD.

“To be honest, we were surprised,” said lead investigator Cameron McAlister, MBChB (Vancouver General Hospital, Canada). “Theoretically, you might expect some harm from receiving thrombolysis. You could get an extension of the dissection. We’re only looking at early outcomes and all of these patients are in hospital and still have a chance to get an angiogram and treatment if there is a problem, but from the data we’re seeing, although there is a change in the angiographic appearance [with thrombolysis], it doesn’t seem to reflect on outcomes.”

While intravenous thrombolysis is a well-established treatment for STEMI patients if timely PCI is unavailable, there are few data supporting its safety in patients with SCAD. In fact, guidelines typically say that intravenous thrombolysis should be avoided in SCAD, with the European Society of Cardiology even stating that thrombolytic therapy is contraindicated. And since some of these patients are presenting to smaller hospitals without coronary angiography, said McAlister, patients with STEMI resulting from SCAD may be treated with thrombolysis before transfer to a larger, PCI-capable hospital.

Theoretically, you might expect some harm from receiving thrombolysis. You could get an extension of the dissection. Cameron McAlister

Anuradha Tunuguntla, MBBS (CHI Health Nebraska Heart, Lincoln), one of the discussants following the presentation, also expressed surprised there was no significant difference in outcomes between the two treatment groups, noting that intravenous thrombolysis in patients with SCAD might be expected to accentuate bleeding of the intramural hematoma or cause an extension of the dissection. She noted there are even theoretical concerns about the potential risks of standard ACS therapies in patients with SCAD, such as systemic anticoagulation.

The worry is that intravenous thrombolytic therapy “might actually make the situation worse,” said Tunuguntla, but these data suggest that might not be the case.

Difference in Angiographic Outcomes

The new observational study, which was presented as a “Key Abstract” online today as part of a sneak peek at TCT 2021, includes 351 STEMI patients with SCAD included in the Canadian SCAD Study.

Of the patients in this multicenter study, 64 received intravenous thrombolysis, the vast majority tenecteplase (92.1%), and 287 did not receive thrombolytic therapy.

There was no significant difference in baseline characteristics between the two groups. The patients were quite young (52.8 vs 50.2 years in the thrombolysis and no-thrombolysis arms), more than 90% were female, and both groups had a low prevalence of cardiovascular risk factors. In terms of presentation and management, again there was no difference between the two groups. In both cohorts, the majority of patients were treated conservatively with medical therapy and roughly one-quarter underwent coronary revascularization with PCI or CABG surgery.     

On the angiogram, the majority of patients treated with thrombolysis had type 1 SCAD (65.6%), a dissection that shows multiple radiolucent lumens of the arterial wall with contrast staining, and 32.8% had type 2 SCAD, which is identified by long, diffuse arterial narrowing that represents intramural hematoma. For the patients not treated with thrombolysis, the reverse was observed: 25.8% had type 1 SCAD and 72.1% had type 2 SCAD.

The risk of death was very low and did not differ between those who received thrombolysis and those who did not. None of the clinical endpoints, in fact, were statistically different between the two groups, although, if anything, outcomes tended to favor those who were treated with thrombolysis. The in-hospital risk of MACE was 6.3% among those who received thrombolysis and 11.5% in those who were not treated with thrombolytic therapy (P = 0.265). There was no difference in hospital length of stay (5.2 days for both; P = 0.926).

McAlister noted that these are relatively young patients who are otherwise quite healthy, which may explain the low rate of adverse events. While the researchers can’t explain why thrombolysis didn’t cause any harm, the data are reassuring, he said.

Harlan Krumholz, MD (Yale University School of Medicine, New Haven, CT), another of the discussants, said that while the results were not statistically significant, it’s important to know just how wide the confidence intervals were around the individual endpoints given the trend favoring thrombolysis. The study, he noted, doesn’t have a lot of statistical power given the small number of patients. Additionally, Krumholz questioned whether there was any difference in the baseline ECG findings between the two patient groups.

“Part of this is whether the treatment caused the conclusion or whether the selection of patients caused the conclusion, and whether or not people who had certain electrocardiographic presentations were more likely to receive treatment,” he said.

McAlister conceded that the study sample size was small, noting there is also a possible risk of survivor bias, whereby those who received thrombolysis but who didn’t survive to angiography would not be represented in the observational study. However, he suspects that this represents only a small number of patients and likely wouldn’t influence their overall findings.

The bottom line is that if physicians treat a STEMI patient with intravenous thrombolysis before the angiogram reveals SCAD, “you probably haven’t done them any harm,” said McAlister. “Of course, if we know that they have SCAD, then I don’t think we would say to give them thrombolysis. It’s just nice to know that the outcomes aren’t too bad.”