“The major procedural difference between elective primary percutaneous coronary intervention (PCI) and an ST-segment elevation myocardial infarction (STEMI) intervention is thrombus, and you will encounter thrombus,” warned Sameer Mehta, MD, University of Miami, Miami, Florida, USA. “The major component of intervention for STEMI is understanding thrombus and how to manage it effectively.”

In a retrospective study that investigated the impact of thrombus burden on clinical outcomes in 812 consecutive patients who were treated with drug-eluting stents (DES), large thrombus burden (defined as thrombus burden ≥2 vessel diameters) was an independent predictor of mortality (HR, 1.76; p=0.023) and major adverse cardiac events (MACE; HR, 1.88; p=0.001) [Sianos G et al. J Am Coll Cardiol 2007]. Small thrombus burden was associated with less distal emboli and incidence of no reflow, greater final TIMI 3 flow, and higher rates of myocardial blush grade 3. The initial amount of thrombus impacted both acute and long-term outcomes.

Svilaas and colleagues randomly assigned 1071 patients to receive manual thrombus aspiration or conventional PCI before undergoing coronary angiography and found that even minimal aspiration resulted in better reperfusion and clinical outcomes than conventional PCI, irrespective of clinical and angiographic characteristics at baseline [Svilaas T et al. N Eng J Med 2008]. Patients who were pretreated with a manual thrombectomy device before PCI had better epicardial and myocardial perfusion, less distal embolization, and significant reduction in 30-day mortality (p=0.003). Thus, if not contraindicated, adjunctive manual thrombectomy devices should be routinely used in STEMI patients who are undergoing primary angioplasty [De Luca G et al. Eur Heart J 2008]. Both the United States and European guidelines support the use of aspiration thrombectomy for patients who are undergoing PCI for STEMI

The Mehta Classification [Mehta S et al. Cath Lab Digest 2011] provides a selective strategy for thrombus management, based upon the thrombus grade. The first step is to identify the grade of thrombus using a scale, where Grade 0 represents no thrombus and Grade 5 represents complete occlusion of the vessel. For Grades 0 and 1, direct stenting is possible. For Grades 2 and 3, aspiration thrombectomy is recommended, followed by PCI. Passes with the aspiration catheters should be made throughout the entire length of the thrombus until there is no angiographic evidence remaining; often, just 2 passes is sufficient. For Grades 4 and 5, the use of a mechanical approach (eg, the AngioJet® or Clearway™) is recommended. The rheolytic thrombectomy device is effective for debulking voluminous thrombi. If AngioJet devices are not available, a default catheter, such as an aspiration catheter, may be used for high-grade thrombus. Early upstream antiplatelet pharmacology must be incorporated as well.

In summary, said Dr. Mehta, “to eliminate the thrombus, you must first identify the grade of thrombus. The thrombus-graded approach to using these devices, as in the SINCERE (Single Individual Community Experience Registry for Primary PCI) database, produces excellent clinical results.”