The main finding of our study is that AngioJet rheolytic thrombectomy with PCI in patients with TIMI thrombus grade 5 did not reduce all-cause mortality, heart failure, rehospitalization, target vessel revascularization as compared with routine treatment at 1-year follow-up. However, unlike manual thrombus aspiration, AngioJet rheolytic thrombectomy did not increase the risk of stroke in patients with high thrombus burden.
High thrombus burden is associated with poor myocardial perfusion and adverse clinical outcomes6, 11. An individual patient Meta-Analysis showed that manual thrombus aspiration was associated with fewer cardiovascular deaths (170 [2.5%] versus 205 [3.1%]; hazard ratio, 0.80; 95% confidence interval, 0.65–0.98; P = .03) and with more strokes or transient ischemic attacks (55 [0.9%] versus 34 [0.5%]; odds ratio, 1.56; 95% confidence interval, 1.02–2.42, P = .04)12. In the Chinese population of TOTAL trial, manual thrombus aspiration was significantly associated with a nearly sevenfold increased risk of stroke at 5 years compared with PCI alone13. The risk of stroke might be correlated with embolization of thrombus from the coronary artery to systemic circulation. AngioJet rheolytic thrombectomy is achieved by injecting pressurized saline through a hypotube by the distal tip of the coronary catheter, thereby leading to a low-pressure zone (Bernoulli effect). Thrombus is fragmented by the saline jets out of the catheter before being evacuated from the body through the catheter. A comparison of manual thrombus aspiration with rheolytic thrombectomy by optical coherence tomography showed that rheolytic thrombectomy group had a lower residual thrombotic burden as compared with manual aspiration14. Therefore, rheolytic thrombectomy is more effective in thrombus removal than manual aspiration, which might be the main reason why rheolytic thrombectomy did not increase the risk of stroke in our study.
So far, the results of randomized trials on rheolytic thrombectomy in patients with STEMI were controversial. The JETSTENT trial, which enrolled 501 patients with thrombus grade 3 to 5, showed a higher event-free survival rate as compared with direct stenting alone15. The MUSTELA trial revealed that thrombectomy had a better post-procedural ST-segment elevation resolution and reduced microvascular obstruction at 3 months in patients with high thrombus load by using Export catheter and AngioJet Ultra catheter in a sequential alternating fashion16. On the contrary, the AiMI trial showed increased 1-month mortality and major adverse cardiovascular event (MACE) rate in patients treated with rheolytic thrombectomy as compared with PCI alone17. The inconsistencies of these results may be associated with study design, limited sample size, technique, and selection bias of the patients.
Our study showed that AngioJet rheolytic thrombectomy had a significantly lower mortality than the routine treatment group in all patients with TIMI thrombus grade 5. The death rate was still lower in the AT group after propensity-score matching (4.3% vs 6.8%), but the difference was not statistically significant. As it was a non-randomized retrospect study, there may exist selection bias. The patients underwent AngioJet rheolytic thrombectomy had a higher thrombus burden in real-world experiences since operators won’t take into account thrombus aspiration in patients with mild thrombus burden. The creatine kinase-MB at admission was significantly higher in the AT group, which indicated that the patients of the AT group might have a larger infarct size. Hence, the patients of the AT group might have a more serious clinical condition than the RT group. Patients who are at high risk of adverse outcomes tend to have the maximum benefit from a given treatment, which is called as “quantitative interaction”18. A real-word study enrolled 9100 patients diagnosed with STEMI showed that selective aspiration thrombectomy at the operation’s discretion had a comparable mortality rate compared with PCI alone and did not increase the risk of stroke19.
Previous studies revealed that patients with high risk might benefit from thrombus aspiration20, 21. Ruben et al have reported that rheolytic thrombectomy was associated with a lower target vessel revascularization in patients with acute myocardial infarction complicated by cardiogenic shock22. Ahmed et al found that thrombus aspiration might be associated with improved reperfusion and myocardial salvage especially in STEMI patients presenting after 12 h from symptom onset23. Accordingly, further investigations on AngioJet rheolytic thrombectomy among patients with high risk is warranted.
Our study has several limitations. First, this is a non-randomized retrospective study. Although propensity-score matching was used, the baseline characteristics can not be matched utterly. There might be selection bias which might influence the findings. Second, our study lack of surrogate markers of myocardial reperfusion, such as myocardial blush grade, ST-segment resolution, or infarct size. Finally, our research was a single-center study with a small sample size. A large multicenter trial is warranted to shed light on the benefit and safety of AngioJet rheolytic thrombectomy in patients with high thrombus burden.