TOTAL Substudy: Routine Thrombectomy Has No Effect on Culprit Lesion Thrombus Burden in STEMI


Bad news keeps rolling in for routine thrombectomy as an adjunct to PCI. An OCT substudy of the TOTAL trial, published online May 20, 2015, ahead of print in the European Heart Journal, has shown that thrombectomy does not reduce thrombus burden or volume in STEMI patients. 

Recent studies including the main TOTAL trial and TASTE also have shown lack of benefit with the adjunctive therapy.

Next Step: TOTAL Substudy: Routine Thrombectomy Has No Effect on Culprit Lesion Thrombus Burden in STEMI

TOTAL, originally published in the New England Journal of Medicine earlier this year, randomized 10,732 STEMI patients who were referred for primary PCI within 12 hours of symptom onset to routine manual thrombectomy with the Export catheter (Medtronic) before intervention or to PCI alone. Compared with PCI alone, routine thrombectomy did not reduce the primary composite endpoint of cardiovascular death, recurrent MI, cardiogenic shock, or NewYork Heart Association (NYHA) class IV heart failure at 180 days.

Unexpectedly, the thrombectomy group in TOTAL had a slightly higher risk of stroke at both 30- and 180-day follow up.

For the substudy, Tej Sheth, MD, of McMaster University and Hamilton Health Sciences (Hamilton, Canada), and colleagues looked at 214 patients who underwent OCT imaging immediately after thrombectomy or PCI alone and again after stent deployment. Interpretable images were available for 173 patients.

No Obvious Differences

The percentage of pre-stent thrombus burden (primary outcome) and various secondary outcomes were similar between the patients who received thrombectomy before PCI and those who did not (table 1).

Table 1. TOTAL Subanalysis: Primary and Secondary Endpoints

Additionally, among subgroups of baseline TIMI thrombus grade, no differences were seen in the percentage of thrombus burden before or after stenting or in post-stent atherothrombotic burden. However, there was low correlation between post-stent atherothrombotic burden and pre-stent thrombus burden both overall (r = 0.34) and by treatment group (r = 0.29 for thrombectomy plus PCI and r = 0.38 for PCI alone).

Bailout Still on the Table

“Our findings suggest that the lack of a reduction in clinical events with thrombectomy is not due to inadequate removal of thrombus,” Dr. Sheth and colleagues write. “In fact, the low thrombus burden in most patients after thrombectomy indicates that more aggressive measures to reduce thrombus in STEMI may not improve outcomes when employed as a routine strategy.”

Instead, they suggest that bailout use of thrombectomy “may still be appropriate in patients with high thrombus burden where an initial PCI-alone strategy fails,” which occurred in 7% of those initially receiving PCI alone in TOTAL.

Yet the authors also note important limitations of the OCT substudy. Mean pre-stent thrombus burden was lower than anticipated, suggesting that the study may have been underpowered to detect a difference between groups. Additionally, the prevalence of high thrombus burden may have been underestimated due to inability to perform adequate imaging. It is also possible, they say, that catheter passage may have displaced thrombus from the culprit lesion in some cases prior to imaging, potentially contributing to the low pre-stent thrombus burden observed. Finally, enrolment in the OCT substudy was at operator discretion, and some patients with more extreme thrombus burden may have been excluded.

Enthusiasm Waning for Thrombus Extraction in Coronaries

“Whichever way the findings of this study are interpreted or explained, it is an important step towards understanding the effects of [thrombectomy] and [PCI] at the level of the culprit lesion and possible identification of patients who may benefit from [thrombectomy],” says Ronald K. Binder, MD, of University Hospital Zürich (Zürich, Switzerland), in an accompanying editorial.

Importantly, Dr. Binder notes that as support for thrombus extraction in cerebral vessels is rising in stroke therapy, enthusiasm for its use in the coronaries is waning due to the recent spate of negative trials, including TOTAL and TASTE.

“In the light of major randomized trials showing no effect on survival of [thrombectomy] in STEMI all-comers, we need to understand whether [it] should be restricted to a bailout after unsuccessful [PCI] or should become a tailored initial approach in selected patients (eg, patients with the highest preprocedural thrombus load),” Dr. Binder concludes.


Sources:

1. Bhindi R, Kajander OA, Jolly SS, et al. Culprit lesion thrombus burden after manual thrombectomy or percutaneous coronary intervention alone in ST-segment elevation myocardial infarction: the optical coherence tomography substudy of the TOTAL (ThrOmbecTomy versus PCI ALone) trial. Eur Heart J. 2015;Epub ahead of print. 
2. Binder RK. Look beyond what seems obvious: thrombus burden after aspiration thrombectomy [editorial]. Eur Heart J. 2015;Epub ahead of print. 

Disclosures:

  • The TOTAL OCT substudy was supported in part by a grant from St. Jude Medical.  
  • The TOTAL trial was supported by grants from Medtronic, the Canadian Institutes of Health Research, and the Canadian Network and Center for Trials Internationally (CANNeCTIN). 
  • Dr. Sheth reports receiving grants and personal fees from St. Jude Medical during the conduct of the study. 
  • Dr. Binder reports no relevant conflicts of interest. 

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