Thrombus Aspiration during ST-Segment Elevation Myocardial Infarction

Published - Written by Joshua Allen-Dicker

If there was a broken-down car on your street blocking traffic, would you rather hire a tow truck to remove it, or hire a bulldozer to smash it into smaller pieces?  Most people might pick the first option, but recent results of the TASTE trial (Thrombus Aspiration in ST-Elevation Myocardial Infarction in Scandinavia) suggest that this analogy may not hold true in the case of treating an ST-elevation MI (STEMI).

TASTE, published in this week’s NEJM, is a randomized controlled trial that examined whether removal of a coronary artery thrombus (the tow truck method) prior to stent placement improved 30 day mortality in STEMI patients as compared to placement of a stent without first removing the thrombus (the bulldozer method).

Physiologically, the tow truck method makes sense: removal of the thrombus prior to placing a stent should reduce distal embolization of thrombus fragments and improve overall myocardial recovery.  In fact, prior research supported this line of thinking.  TAPAS (Thrombus Aspiration during Percutaneous Coronary Intervention in Acute Myocardial Infarction Study), published in NEJM in 2008, demonstrated benefits in STEMI patients who were randomized to thrombus aspiration prior to stenting.  Although these results were convincing enough to affect ACC/AHA Joint Guidelines, critics of TAPAS pointed to its lack of clinical end points, other less convincing studies, and a subsequent meta-analysis that raised concerns for an increased risk for stroke.

The authors of TASTE therefore designed a large multisite trial powered for clinical end points such as 30-day and 1-year mortality.  Patients were recruited from a Swedish national database population of all patients presenting with STEMI, defined as presentation within 30 minutes to 24 hours of acute onset chest pain with either ST-elevations or a new left bundle branch block on electrocardiogram.  Patients were randomized to receive thrombus aspiration followed by stenting or stenting alone.  The type of stent and use of a P2Y12 inhibitor was left to physician discretion.  The primary efficacy end point was 30-day mortality.  Additional data were collected on need for rehospitalization or revascularization as well as safety end points that included incidence of heart failure and stroke.

TASTE found no significant difference in 30-day mortality (2.8% in the aspiration group versus 3.0% in the no aspiration group, hazard ratio 0.94, 95% CI 0.72 – 1.22).  Similarly, there was no significant difference identified in risk for rehospitalization, stent thrombosis or any of the safety end points.

While this initially may sound conclusive, it’s not yet time to discard your tow-trucks and 6-french aspiration catheters; TASTE has several limitations.

First, 60% of patients who met criteria for this study were not randomized into the trial.  Second, the population of patients who underwent randomization had significant baseline differences from the population that did not undergo randomization—mainly, they appear to have been less sick.  Third, the outcomes for patients that underwent randomization were significantly better than those who did not undergo randomization (a 30-day mortality of 2.9% versus 10.6%).   Taken together, these factors suggest that selection bias may have had a notable influence on the results of the trial.

Despite these notable results and their shortcomings, the current report may not be decisive in determining the future of thrombus aspiration.  The 1-year mortality data for the TASTE trial are yet to be published, and other trials are in the works.  While we wait, we can mull over results which do not show a primary efficacy benefit, but also do not show a primary safety harm.  For now, the jobs of both tow-truckers and bulldozers are safe.