Distal Protection Adds Early Boost to Thrombectomy in STEMI, but No Lasting Benefit

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In patients with ST-segment elevation myocardial infarction (STEMI), thrombus aspiration with distal protection shows an early advantage over aspiration alone in restoring coronary blood flow but fails to yield long-term benefit with regard to left ventricular (LV) function, according to an observational study published online September 16, 2013, ahead of print in the American Journal of Cardiology.

Shinji Satoh, MD, PhD, of the National Hospital Organization Kyushu Medical Center (Fukuoka, Japan), and colleagues looked at 176 STEMI patients undergoing primary PCI who were assigned to thrombus aspiration with (n = 72) or without (n =104) distal protection using a filter device (Filtrap, NIPRO, Osaka, Japan; n = 72) based on the operator’s choice and anatomical accessibility.

Early Advantage Fades

Initial TIMI flow grades were 0 in 82% of patients in the aspiration-alone group and 78% in the aspiration plus distal protection group. The initial rate of achieving a postprocedural TIMI flow grade of 2 or 3 (primary endpoint), was higher in the distal protection group (table 1).

Table 1. Post-PCI TIMI Flow Grade

^a P for trend = 0.0049.

A similar pattern in favor of distal protection was seen for myocardial blush grades (P for trend = 0.0186).

However, among those who underwent follow-up catheterization, there were no differences between the groups in LV end-diastolic volume index (P = 0.96), LV end-systolic volume index (P = 0.45), or LV ejection fraction (P = 0.18) either at baseline or at 6 months. Additionally, 6-month mortality was similar for the aspiration-alone group and the aspiration-plus-distal-protection group (6% vs. 1%; P = 0.24).

Damage May Already Be Done

According to Dr. Satoh and colleagues, the TIMI flow and myocardial blush grades suggest that thrombus aspiration with distal protection is superior to thrombectomy alone in initially restoring coronary blood flow, irrespective of the clinical and angiographic characteristics at baseline. But, they add, the study also suggests distal protection failed to reduce infarct size, prevent cardiac remodeling, or preserve myocardial function, even in the presence of ACE inhibitors and/or angiotensin II receptor blockers or beta blockers.

One explanation may be that the distal protection device did not adequately block all atherothrombotic debris. “Although visible debris was extracted, embolization may still have occurred at the time of the initial lesion crossing and/or in the unprotected proximal side branches, although there were no angiographically apparent increases in side-branch occlusion in the distal protection group,” the investigators write.

Other possibilities are that transmural infarction may already be complete with little chance for additional myocardial recovery in most patients reperfused after 3 hours, or that coronary microcirculatory flow reserve may already be impaired, even in patients with a TIMI grade of 2, the authors note.

Timing Is Everything

In an e-mail communication with TCTMD, Sunil V. Rao, MD, of the Duke Clinical Research Institute (Durham, NC), said the study underscores the disconnect between what is done procedurally to try to improve efficacy, and subsequent patient outcomes.

“Procedural strategies that improve outcome are really the ones that reduce complications from the procedure, such as bivalirudin and radial access,” Dr. Rao explained. Conversely, procedural strategies like thrombectomy and distal protection aimed at improving efficacy are generally futile because the procedure takes place well after the period of potential benefit, he said.

“Similar to the recent [disappointing] door-to-balloon time data, we need to focus on getting the symptom onset to reperfusion times lower. With the prolonged time between symptom onset and PCI, by the time we use thrombectomy or distal protection, it's probably too late to show a benefit,” Dr. Rao maintained.

Also troubling are recent results from the TASTE trial, presented earlier this month at the European Society of Cardiology meeting in Amsterdam, The Netherlands. In that study, the primary endpoint of 30-day all-cause mortality was similar between PCI with and without thrombus aspiration (P = 0.63), although a strong trend favored thrombus aspiration for reinfarction at 30 days (HR 0.61; P = 0.09).

But Dr. Rao said there may still be hope for determining whether routine thrombectomy has a role in STEMI. The ongoing TOTAL trial will be powered for clinical outcomes, “so we will see if there will be a benefit, or harm, from thrombectomy in a much larger dataset,” he said.

Study Details

There were no differences between the groups in distribution of the culprit lesions, number of diseased vessels, PCI procedures, rate of use of assist devices, or onset-to-reperfusion time.

 

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Source:
Satoh S, Inoue H, Omura S, et al. Comparison of the reperfusion efficacy of thrombus aspiration

with and without distal protection during primary percutaneous coronary intervention in patients with acute ST-segment elevation myocardial infarction. Am J Cardiol. 2013;Epub ahead of print.

 

 

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