MUSTELA Studies Thrombectomy as an Adjunct to Primary PCI

November 10, 2011—Lead Investigator Anna Sonia Petronio, MD, presented findings from the MUSTELA trial at the annual Transcatheter Cardiovascular Therapeutics (TCT) scientific symposium in San Francisco, reported TCT Daily.

MUSTELA is a prospective, randomized trial composed of 208 patients with ST-segment elevation myocardial infarction (STEMI) and thrombus-rich lesions (TIMI thrombus ≥ grade 3). The primary purpose of the MUSTELA trial was to determine whether coronary thrombectomy as an adjunct to primary percutaneous coronary intervention (PCI) in patients with high thrombotic burden improves myocardial perfusion and reduces infarct size as assessed by magnetic resonance imaging (MRI). The patients were randomized to aspiration or no aspiration, with the aspiration patients split between rheolytic and manual methods.

According to TCT Daily, the MUSTELA investigators found that thrombectomy did not reduce infarct size compared to standard PCI after 3 months in the study's high-thrombus burden STEMI population. The procedure was, however, associated with a higher rate of complete ST-segment elevation resolution than PCI alone.

“No significant difference was observed regarding 1-year freedom from MACE,” commented Dr. Petronio, who also noted that thrombectomy was associated with less microvascular obstruction at 3-month MRI; thrombectomy patients tended to have viable tissue interspersed with necrotic areas.

As detailed by TCT Daily, postprocedural TIMI 3 flow was achieved in 90.4% of thrombectomy patients compared with 81.7% of controls (P = .07), and ST-segment elevation resolution of > 70% at 60 minutes was achieved in 57.4% of the thrombectomy group compared with 37.3% of controls (P = .004).

At 3 months, MRI results showed a delayed enhancement area of 20.4% in thrombectomy patients compared with 19.3% of controls (P = .54). At 1 year, freedom from major adverse cardiac events was 93.9% in control patients versus 92.3% in thrombectomy patients (P = .57).

In a subanalysis of the thrombectomy patients, the investigators found that angiographic success was more common in those patients who underwent rheolytic aspiration (n = 54) compared with those patients who underwent manual aspiration (n = 50) (P = .02). Overall, rates of success for the rheolytic versus manual group were 94.4% and 78%, respectively (P = .02). At 3-month MRI, however, there were no significant differences with regard to infarct size. Successful delivery of the manual thrombectomy system was 98% compared with 100% for the rheolytic system.

Baseline characteristics were similar between the thrombectomy and control groups. The average age was 61.5 years in the control group and 63 years in the thrombectomy group, and there were equivalent rates of diabetes, hypertension, and other risk factors. There were less control patients with an initial diagnostic TIMI flow of 0 to 1 (77.9%) than there were thrombectomy patients (91.3%; P = .007). Although it did not reach significance, there was a trend toward a lower pain-to-balloon time in the control group compared with the thrombectomy group (241 minutes vs 260 minutes; P = .07), reported TCT Daily.