The Missing Link in STEMI Interventions - Thrombus Aspiration during Primary Percutaneous Coronary Intervention
The dots in ST-elevation myocardial infarction (STEMI) interventions finally get connected through the robust results of the Thrombus Aspiration during Primary Percutaneous Coronary Intervention (TAPAS), published in the recent edition of the New England Journal of Medicine (NEJM 2008; 358:557-67; see sidebar). In this landmark randomized trial of primary percutaneous coronary intervention (PCI), Felix Zijlstra and colleagues report better reperfusion and clinical outcomes than conventional PCI with thrombus aspiration performed with the 6-French Export Aspiration Catheter (Medtronic, Inc., Santa Clara, CA), irrespective of clinical and angiographic characteristics at baseline.
In a total of 1,071 patients that were randomly assigned to the thrombus-aspiration group or the conventional-PCI group, the researchers reported a myocardial blush grade of 0 or 1 in 17.1% of the patients in the thrombus-aspiration group and in 26.3% of those in the conventional-PCI group (p<0.0001). In addition, complete resolution of ST-segment elevation occurred in 56.6% and 44.2% of patients respectively (p<0.0001).
Most critically, the TAPAS investigators demonstrated the critical importance of the surrogates of myocardial blush grade (MPG) and ST-segment resolution (STR) as appropriate endpoints. At 30 days, the rate of death in patients with a myocardial blush grade of 0 or 1, 2 and 3 was 5.2%, 2.9% and 1% respectively (p<0.003) and the rate of adverse events was 14.1%, 8.8% and 4.2% respectively (p<0.0001).
Although numerous trials (Table 1) have demonstrated favorable trends in the use of aspiration and thrombectomy devices, TAPAS provides irrefutable benefits of thrombectomy for STEMI lesions. Benefits with thrombus aspiration were seen across the board and thrombus aspiration was better irrespective of the sex, age, total ischemic time, infarct-related vessel or segment, TIMI grade or visible thrombus by angiography.
From our experience in the Single INdividual Community Experience REgistry for Primary PCI (SINCERE) database, we offer a few additional refinements to the superb work from TAPAS:
a. It must be recognized that it may not always be possible to identify thrombus by angiography — it is precisely in dealing with this limitation wherein TAPAS provides rationale for using thrombectomy for all subsets. Yet, not only should every effort be made to demonstrate thrombus, we even suggest trying to determine the thrombus grade.
b. Using the thrombus grade (Table 2) as a baseline, we then suggest a strategy to employ either aspiration or mechanical thrombectomy (Table 3). Although we are committed to universally employing thrombectomy for all STEMI interventions and we find the low-profile and trackability of aspiration catheters extremely beneficial, we also recognize the limitations of these catheters in the presence of bulky thrombus and in treating saphenous vein grafts. For these indications, we strongly feel that mechanical thrombectomy with devices such as the AngioJet (Possis Medical, Inc., Minneapolis, MN), provides even more effective treatment of thrombus.
c. Finally, we offer a few tips from our experience regarding the use of aspiration catheters:
1. These catheters are most effective with fresh clot. Organized thrombus is more resistant to debulking.
2. Various aspiration catheters have different profiles:
a. Different pushability, tractability and aspiration rates.
b. All are 6-French compatible.
c. It is useful to stock and be familiar with the use of at least one.
3. Flush catheter lumen well before use as it facilitates better tracking over the wire.
4. Avoid kinking the catheter — advance slowly over the initial, softer portion of the catheter.
5. Monitor distal tip of the guidewire as the aspiration catheter is advanced — it is not uncommon for the guidewire to advance during this maneuver.
6. Advance the aspiration catheter through the entire length of occlusive disease.
7. Maintain aspiration for longer duration in the dense portion of the thrombus.
8. Maintain aspiration rate by maintaining negative pressure during advancement and withdrawal of the catheter.
9. Watch the guide catheter as aspiration catheter is withdrawn:
a. Anecdotal reports of the guiding catheter getting sucked in.
b. It may cause trauma to proximal vessel (e.g., left main).
c. Consider releasing the negative pressure while withdrawing the catheter.
10. If no suction of blood despite appropriate preparation and lesion selection:
a. The aspiration lumen may be plugged with thrombus. In this case, withdraw and flush the catheter, and repeat the procedure.
11. Additional passes may be needed for bulky thrombus.
12. If thrombus burden is unchanged after two passes with appropriate technique and the vessel anatomy is suitable, consider a switch to the AngioJet.
Portions of this article were reprinted with permission from Mehta S. Chapter 8: Practical Guidelines for Performing STEMI Interventions. In: Mehta S, ed. Textbook of STEMI Interventions. Malvern, PA: HMP Communications, 2008:113-130.
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