Should Aspiration Thrombectomy Be Performed in All, Most, or Few Primary PCI Procedures?

December 02, 2009

In This Article

Aspiration Thrombectomy

Outcomes using manual or aspiration thrombectomy as adjunctive therapy with primary PCI have been more encouraging. All the aspiration catheters are similar and have two lumens—one lumen for passage of the catheter over a coronary wire and a second lumen for manual aspiration of thrombus and atheromatous debris.

The large Thrombus Aspiration During Percutaneous Coronary Intervention in Acute Myocardial Infarction Study (TAPAS) randomized 1,071 STEMI patients to aspiration thrombectomy followed by stenting versus stenting alone.[6] Aspiration was successfully performed in 90% of patients, thrombus or atheroma was retrieved in 72% of patients, and direct stenting (without predilatation) was performed in 59% of patients. The frequency of MBG 3 (the primary endpoint) and complete STR (the secondary endpoint) was significantly higher with aspiration thrombectomy. These improved results in myocardial reperfusion were associated with clinical benefit at 1 year, with a lower incidence of cardiac death (3.6% vs. 6.7%, p = 0.02) and cardiac death or MI (5.6% vs. 9.9%, p = 0.008) (Slide 3).[7]

Slide 3.

TAPAS Trial - Aspiration Thrombectomy With Primary PCI

The meta-analysis performed by Drs. Bavry and Bhatt evaluated 13 randomized trials with manual thrombectomy and found that thrombectomy improved myocardial perfusion, measured both by MBG and STR, and was associated with lower mortality (Slide 2).[3] In a separate meta-analysis, De Luca and colleagues evaluated nine randomized trials comparing PCI with aspiration thrombectomy versus PCI alone and found that patients treated with thrombectomy had less distal emboli, a higher frequency of TIMI 3 flow and MBG 3 post-PCI, and lower 30-day mortality (Slide 4 and Slide 5).[8]

Slide 4.

Randomized Trials With Manual Thrombectomy - De Luca Meta-Analysis

Slide 5.

Randomized Trials With Manual Thrombectomy - De Luca Meta-Analysis - 30-Day Mortality

These trials provide evidence that aspiration thrombectomy may be beneficial with primary PCI, but they do have limitations. All of the randomized trials were small trials with surrogate endpoints (usually MBG and STR) and none were powered for clinical endpoints. The largest trial, TAPAS, was not powered to detect differences in mortality, and mortality was not a prespecified endpoint.[6,7] The 46% mortality reduction at 1 year is much larger than one would expect. If there is a mortality benefit from aspiration thrombectomy, it is certainly smaller than this and would not have been detected in a trial this size except by chance.

Meta-analyses have limitations, one of which is that negative trials are often not reported or not published. There are certainly examples of treatments that are thought to be effective based on meta-analyses, but which are proven to be of no benefit when evaluated by a properly powered clinical trial. The use of magnesium for treatment of acute MI, which was found not to be effective in the Fourth International Study of Infarct Survival (ISIS-4) trial, is one example.[9] Virtually all of the randomized trials with aspiration thrombectomy enrolled a broad spectrum of patients with STEMI. One might expect aspiration thrombectomy to be most beneficial in patients with large thrombus burden, but none of the trials evaluated thrombectomy in patients with large thrombus burden and none were large enough to look at subgroups to see which patients might benefit the most.

The potential benefit of aspiration thrombectomy with primary PCI may be due to one of two mechanisms. The conventional paradigm is that thrombectomy may be beneficial by preventing distal embolization, with consequent improvement in myocardial reperfusion. This can result in better left ventricular function and better clinical outcomes. Recently, it has been suggested that thrombectomy may reduce the risk of subsequent stent thrombosis. Sianos and colleagues found that patients with STEMI treated with drug-eluting stents, who have a large thrombus burden, have an increased risk of stent thrombosis (Slide 6).[1] Large thrombus burden was defined as a filling defect whose length was greater than or equal to twice the vessel diameter. In patients with total occlusion of the infarct artery, reperfusion was established with a wire or small balloon before thrombus burden was assessed. The authors found that the risk of subsequent stent thrombosis after primary PCI with stenting can be dramatically reduced with rheolytic thrombectomy.

Slide 6.

Importance of Thrombus Burden - Outcomes After DES for STEMI

Late stent malapposition is much more common after stenting with primary PCI compared with elective PCI, especially with drug-eluting stents, and may predispose to stent thrombosis. Late malapposition may be related to underdeployment of stents at the time of primary PCI, and this may be due in part to thrombus behind the stent, which subsequently resolves and leads to stent malapposition. Removal of thrombus before stenting potentially could lead to better stent expansion and less late malapposition.

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