Low Incidence of Ischemic Stroke Associated With Thrombus Aspiration in STEMI Patients Undergoing Primary PCI

Background. Thrombus aspiration (TA) during primary percutaneous coronary intervention (PPCI) for ST-segment elevation myocardial infarction (STEMI) was recommended to minimize distal embolization and to reduce thrombus burden prior to PPCI. Subsequent randomized trials showed no mortality benefit from TA and suggested an increased risk of stroke up to 180 days following TA, although it was not obvious that the procedure alone caused the strokes. Methods and Results. This study retrospectively analyzed the periprocedural stroke rate in a series of STEMI patients treated with TA and PPCI at a single, large, tertiary hospital, where a rigorous uniform protocol of aspiration was used in all patients. Of 3734 patients, 1404 patients (38%; group 1) underwent TA as part of the PPCI procedure and 2330 patients (62%; group 2) did not undergo TA. There were no significant clinical differences between the 2 groups. In total, there were 20 strokes (0.54%), with 3 (0.2%) occurring in group 1, and 17 (0.7%) occurring in group 2 (P=.04). The majority of strokes occurred within 5 days of the procedure, and 3 (0.08%) were hemorrhagic. There were 22 intraprocedural deaths (0.6%), related to cardiogenic shock. There were no intraprocedural strokes. Conclusions. Very low stroke rates immediately post STEMI were seen in patients undergoing TA and PPCI in this real-world study. TA can be performed safely in STEMI patients undergoing PPCI with a short-term stroke risk equivalent to risk without TA. Further studies may be needed to explain the increased incidence of late stroke noted after TA and elucidate causative mechanisms.

J INVASIVE CARDIOL 2021;33(10):E805-E807. Epub 2021 August 19.

Key words: primary percutaneous coronary intervention, STEMI, stroke, thrombus aspiration

Thrombus aspiration (TA) during primary percutaneous coronary intervention (PPCI) for ST-segment elevation myocardial infarction (STEMI) was recommended to minimize distal embolization and to reduce thrombus burden prior to PPCI.¹ Subsequent randomized trials showed no mortality benefit from TA² and suggested an increased risk of stroke up to 180 days following TA.³ The mechanisms of stroke varied, and it was not obvious that the procedure alone caused the strokes.

We retrospectively analyzed the periprocedural stroke rate in a series of STEMI patients treated with TA and PPCI between January 2004 and June 2017 at a single, large, tertiary hospital, where a rigorous uniform protocol of aspiration was used in all patients (Westmead Hospital, Sydney, Australia). The incidence of clinically evident inpatient stroke was retrieved from patient records. The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki and was approved by the Western Sydney Local Health District human research ethics committee.

Demographic and procedural data are presented in Table 1 (Part 1; Part 2). Of 3734 patients, 1404 patients (38%; group 1) underwent TA as part of PPCI procedure and 2330 patients (62% ; group 2) did not. There were no significant clinical differences between the 2 groups.

In total, there were 20 strokes (0.54%), with 3 (0.2%) occurring in group 1 and 17 (0.7%) occurring in group 2 (P=.04). The majority of strokes occurred within 5 days of the procedure, and 3 (0.08%) were hemorrhagic. There were 22 intraprocedural deaths (0.6%), related to cardiogenic shock. There were no intra- procedural strokes.

Our study reports an equivalent short-term stroke risk in STEMI patients undergoing TA vs those without TA. This suggests that a rigorous, protocol-based technique of TA may minimize the risk of periprocedural stroke. All patients received standard therapy with antiplatelet medications and unfractionated heparin prior to TA. The guide catheter was always selectively engaged prior to removal of the aspiration catheter. Negative suction was maintained during removal, followed by generous aspiration of the guide catheter.

It is possible that TA-related strokes may be related to technique. However, this would usually result in ischemic strokes and be evident in the first 48 hours post procedure. Those strokes that are primarily hemorrhagic or occur later (>48 hours post procedure) may not be related to TA. In the TOTAL trial, the number of ischemic strokes in the first 48 hours was low and of borderline significance.³ In the TASTE trial, there was no significant difference in the early-period stroke rate between TA and conventional PPCI groups.⁴

Additional hypotheses have been proposed to explain mechanisms of stroke post TA during PPCI. A thrombus that cannot be fully aspirated is at risk of entering the systemic vasculature intact or fracturing and shedding fragments into the systemic circulation, especially if suction is not maintained on the TA catheter during withdrawal.⁵ This risk may be increased if the guide catheter is not engaged in the coronary artery when the TA catheter is withdrawn. Additional factors that may contribute to a higher risk of stroke in patients undergoing TA include the need for catheters >5 Fr, multiple catheter exchanges, and generally longer procedure times.

It is possible that the reported increase in stroke rates late after TA may be unrelated to the technique itself. Stroke rates in the TA arm in the TOTAL trial were increased at 30 days, at 180 days, and at 12 months post PPCI,³ suggesting an incidence of stroke remote from the index procedure. It is likely that these late-onset strokes relate to TA-independent factors, such as medication during and after the procedure, or an acceleration in the systemic response to ischemic injury on a background of chronic atherosclerosis.

Study limitations. This was a single-center study, and further larger, multicenter studies are required to validate these findings. Due to the retrospective nature of the study, we did not have stroke data after discharge from the hospital; however, this is the subject of an ongoing, prospective study.

Very low stroke rates immediately post STEMI were seen in patients undergoing TA and PPCI in this real-world study. TA can be performed safely in STEMI patients undergoing PPCI with a short-term stroke risk equivalent to risk without TA. Further studies may be needed to explain the increased incidence of late stroke noted after TA and to elucidate the causative mechanisms.