The benefit of manual thrombus aspiration (TA) as an adjunctive technique in the reperfusion of patients with ST-elevation myocardial infarction (STEMI) has been hotly debated. The advantage of TA during primary percutaneous coronary (PPCI) is that it reduces the risk of distal embolization of thrombotic material during the procedure, thus improving microvascular perfusion and reducing infarct size.1–6 Compared to mechanical thrombus removal, manual TA is simpler to perform and is of equal or superior efficacy.7–9

The introduction of manual TA aroused great interest and it is now widely used in interventional cardiology; it has a class IIa recommendation, level of evidence B, in the European Society of Cardiology guidelines for the management of STEMI.10 Nevertheless, there is considerable variation in use of this technique as adjunctive therapy to reperfusion.11 In a recent survey, manual TA was used in less than 20% of PPCI procedures in the US.12 Although some randomized studies have demonstrated clinical benefit by reducing major cardiovascular events,13–15 subsequently confirmed in meta-analyses,8,16–18 other series, including one large-scale study, have not shown the same clinical efficacy.19–22 However, TA may not be possible in some cases (10% of patients scheduled for TA in the TAPAS study13). The effect of failure of TA in patients in whom it was considered to be indicated has been largely unreported.

The primary objective of this study was to identify the predictors of TA failure in a consecutive series of STEMI patients referred for PPCI, in which TA was systematically used as the first option (bail-out procedures were excluded). The secondary objective was to assess the impact of failed TA on cumulative mortality (cardiac and non-cardiac) in the medium term.

Of a total of 614 patients with STEMI, 40 were excluded due to lack of data. Of the 574 assessed, TA was used in 417 (72.6%), and was effective in 365 (87.5%) and ineffective in 52 (12.5%). In the latter group, the lesion could not be crossed in four cases (4/52, 7.7%); the operator proceeded to balloon dilatation of the lesions, but TA was attempted again in only one of these patients, which was also unsuccessful. Tables 1 and 2 summarize the clinical and procedure-related characteristics, respectively, of the study population, according to the efficacy of TA. TA failure was significantly associated with non-smokers, higher GRACE and SYNTAX scores and Killip class at admission, and longer TIT. With regard to the procedure, the circumflex was less frequently the culprit artery, and an intra-aortic balloon pump was more frequently used in those with ineffective TA. There was a tendency for a higher rate of previous therapy with nitrates and calcium channel blockers in the ineffective TA group, and lower hemoglobin at admission. In terms of in-hospital outcome (Table 3), the rate of no reflow was higher in those with failed TA. No significant differences were found in peak CK, CK-MB or TnT, or in LVEF at discharge, although it should be noted that enzyme peaks could not be measured in the first 24 h in 21 patients (3.7%), mainly due to death soon after the procedure (n=19 [90.5%]). Of these 21 patients, TA was used in 12 (57.1%), and was effective in seven (58.3%) and ineffective in five (41.7%). Hospital stay was longer in the ineffective TA group. Mortality was also higher (13.5% vs. 6%, p=0.073) in this group, but without statistical significance.

On univariate analysis, age, SYNTAX score, current smoking, admission hemoglobin, previous therapy with nitrates or calcium channel blockers, TIT and Killip class III/IV at admission correlated with ineffective TA. In multivariate analysis, only SYNTAX score (odds ratio [OR]: 1.049, 95% confidence interval [CI]: 1.015–1.084, p=0.005) and TIT (OR: 1.001, 95% CI: 1.000–1.003, p=0.02) were independent predictors.

We identified 331 patients with at least 12 months of follow-up after STEMI. It was not possible to ascertain vital status in two of these (0.6%), and so 329 patients were included in the analysis of medium-term mortality (mean follow-up: 24±0.82 months, cumulative mortality rate: 13.9%). Unadjusted cumulative mortality was higher in the ineffective TA group (Figure 1). After adjustment for covariables with p<0.1 on univariate analysis (gender, age, TA efficacy, APPROACH and SYNTAX scores, current smoking, TIT, CrCl, target vessel, intra-aortic balloon pump, hemoglobin, systolic blood pressure, Killip class III/IV at admission and LVEF at discharge), LVEF showing moderate or severe dysfunction (hazard ratio [HR]: 6.256, 95% CI: 1.896–20.644, p=0.003), APPROACH score (HR: 1.094, 95% CI: 1.016–1.177, p=0.017), and Killip class III/IV (HR: 2.953, 95% CI: 1.122–7.770, p=0.028) showed a positive correlation with mortality, while higher CrCl values had a protective effect (HR: 0.973, 95% CI: 0.953–0.994, p=0.011).

Figure 1.

Cumulative survival curves as a function of thrombus aspiration efficacy. TA: thrombus aspiration.

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In this series, TA was scheduled in the majority of patients (72.6%), and was effective in most cases (87.5%). It is plausible that the more organized the thrombus, the less effective TA will be, and it is thus not surprising that the longer the delay between symptom onset and reperfusion, the greater the likelihood of TA failure. The correlation between TIT and thrombus organization as a predictor of adverse events has been reported in previous studies.29–32 However, the relationship between SYNTAX score and TA failure is unknown. The technique is more likely to be unsuccessful in patients with unfavorable coronary anatomy such as tortuosity or calcification, or with a large amount of plaque that is at risk of distal embolization, resulting in impaired microvascular perfusion. A correlation between SYNTAX score and risk of no reflow has been demonstrated in some series of patients undergoing PPCI.33

Excluding patients in whom TA was not performed, for example because the vessel involved was of small caliber or there was insufficient thrombotic material to justify TA, systematic use of the technique might be expected to reduce infarct size when effective. However, this assumption was not confirmed in our series. Although peak enzyme levels can only estimate infarct size, they correlate well with infarct size as assessed by CMR.34,35 In studies using CMR to assess the area of necrosis, patients undergoing TA did not show reduced infarct size,22,36 even in cases with less microvascular obstruction.20

With regard to mortality, no significant differences in clinical endpoints would be expected in view of the small sample size. However, the trend observed in in-hospital mortality could be more marked in larger series. Unsurprisingly, in the patient subgroup assessed for cumulative mortality, LVEF showing moderate to severe dysfunction and Killip class III/IV were strong independent predictors of medium-term mortality. These two parameters,37–39 together with the area of myocardium at risk,40 have been reported as markers of adverse prognosis. An interesting possibility is that TA may only have a significant impact in patients with large areas of at-risk myocardium,41 but specially designed prospective studies are needed to confirm this hypothesis. Renal failure has often been cited as an independent cause of mortality in STEMI patients,42,43 and so it is to be expected that higher CrCl values are associated with a protective effect.

The debate concerning the benefits of TA in reperfusion is far from consensus.44 The conflicting results of studies published to date may be due to sample sizes being too small to assess clinical endpoints and to different methods of evaluating coronary microvascular perfusion. At the same time, it appears that not all patients benefit to the same extent from TA, reflecting the heterogeneity of STEMI patients. Only large-scale studies or meta-analyses will provide solid evidence on the most important clinical endpoints, and so our results concerning mortality should be interpreted with caution. It is known that patients with no reflow have increased long-term mortality.45 The significant relationship found between no reflow and ineffective TA may be reflected in increased cumulative mortality in larger series, which would enable this association to be studied in more detail. Overall, the results of this observational study are similar to the latest series comparing TA with conventional PPCI. With the exception of a lower rate of no reflow, effective TA did not result in an unequivocal benefit compared to ineffective TA.

Limitations include the fact that this was a single-center retrospective study and with too small a sample size to assess the impact of TA efficacy on medium-term mortality. The rate of TA failure was low (<15%), which may have affected the results.

In our series, TA was ineffective in 12.5% of cases, and TIT and SYNTAX score were independent predictors of TA failure. On multivariate analysis, ineffective TA was not related to larger infarct size or increased medium-term mortality.

The authors have no conflicts of interest to declare.