Thrombectomy in acute myocardial infarction: Current evidence, challenges, and emerging technologies

Table 1 Thrombus score classification using coronary angiography

Thrombus grade	Definition
Grade 0	No thrombus
Grade 1	Possible thrombus
Grade 2	Small (greatest dimension ≤ 1/2 VD
Grade 3	Moderate (> 1/2 but < 2 VD)
Grade 4	Large (≥ 2 VD)
Grade 5	Unable to assess TB due to vessel occlusion

2 VD: Two times vessel diameter; TB: Thrombus burden.

Table 2 Landmark studies on thrombectomy in acute myocardial infarction

Ref.	Sample size	Design and randomisation	TA catheter type	Primary endpoint	Finding
Byrne et al[1] (REMEDIA)	100 STEMI	Standard PCI (n = 49) vs Manual TA (n = 50)	Diver CE catheter	Post-procedure myocardial blush grade ≥ 2, and ST segment resolution ≥ 70%	TA improves MBG (≥ 2) and STR (68.0% and 44.9% vs 58.0% and 36.7%, respectively) with OR 2.6 (95%CI: 1.2-5.9; P = 0.020) and OR 2.4 (95%CI: 1.1-5.3; P = 0.034), respectively. Direct stenting was more frequently used in TA than standard PCI groups (66% vs 24%). TA is feasible and improves the angiographic and ECG criteria of myocardial reperfusion compared to PCI alone
Szummer et al[2] (EXPIRA)	175 STEMI +	Standard PCI (n = 87) vs Manual TA + PCI (n = 88)	Export Medtronic catheter	Post-procedure myocardial blush grade ≥ 2, and ST segment resolution ≥ 70% at 90 min post-procedure	TA improved MBG (≥ 2) and STR (88% vs 60%; P = 0.001; and 64% vs 39%; P = 0.001). The extent of microvascular obstruction defined by contrast-enhanced cardiac MRI was significantly lower in the TA group; TA significantly reduced infarct size at 3 months, and lower cardiac death was observed at 9 months
Rezkalla et al[3], Iwakura et al[4] (TAPAS)	1071 STEMI	Standard PCI (n = 536), manual TA + PCI (n = 535)	Export Medtronic catheter	MBG of 0 or 1, indicating poor myocardial perfusion	MBG of 0 or 1 was significantly lower in the TA group (17.1%) compared to the conventional PCI group (26.3) (P < 0.001). Complete ST-segment resolution was more frequent in the TA group (56.6% vs 44.2%, P < 0.001), 30-day mortality was significantly lower in the TA group (3.6% vs 6.7%, P = 0.02), one-year mortality was also lower in TA group (3.6% vs 6.7%, P = 0.01)
van Lavieren et al[5], van 't Hof et al[6], Ndrepepa et al[7] (INFUSE-AMI)	452 STEMI ++	Prospective,open-label, randomized, controlled trials, using a 2 × 2 factorial design, were andomized to: (1) Intracoronary abciximab infusion; (2) No intracoronary abciximab; (3) TA; and (4) No TA	Export Medtronic catheter	Reduction in infarct size (measured by cardiac MRI at 30 days)	The intra-coronary Abciximab arm at 30 days showed a reduced infarct size (measured by cardiac MRI) compared to no Abciximab (median 15.1%; IQR: 6.8%-22.7%; n = 181, vs 17.9%; IQR: 10.3%-25.4%; n = 172; P = 0.03). TA vs no TA showed no difference in infarct size at 30 days (median 17.0%; IQR: 9.0%-22.8%; n = 174, vs 17.3%; IQR: 7.1%-25.5%; n = 179; P = 0.51) as well as no mortality difference at 1 year
Vrints et al[8], Kirtane et al[9] (TASTE)	7244 STEMI	Multicentre, randomized, controlled, open-label trial, Thrombus aspiration + PCI vs PCI alone	Multiple catheters	All-cause mortality at 30 days. Secondary endpoints are recurrent myocardial infarction, stent thrombosis, heart failure, and cardiogenic shock	Death from any cause occurred in 2.8% (TA group) vs 3.0% (PCI group) (HR = 0.94; 95%CI: 0.72-1.22; P = 0.63). Routine TA before PCI did not affect 30-day mortality compared to PCI alone[44]. There was no reduction in death from any cause or composite of death, myocardial infarction, or stent thrombosis at 1 year
Matsuo et al[10], Yaméogo et al[11] (TOTAL)	10732 STEMI	Multicentre, randomized, controlled, open-label trial comparing routine aspiration thrombectomy + PCI vs PCI alone	Export Medtronic catheter	Cardiovascular death, myocardial infarction, cardiogenic shock, or class IV heart failure at 180 days	Primary outcome occurred in 6.9% (TA group) vs 7.0% in PCI-only group (HR = 0.99; 95%CI: 0.85-1.15; P = 0.86) with no reduction in CV death, recurrent myocardial infarction, cardiogenic shock, or heart failure within 180 days. Primary outcome at 1 year occurred in 8% of each group (HR 1.00; 95%CI: 0.87-1.15; P = 0.99). CV death at 1 year was reported as 4% in each group (HR = 0.93; 95%CI: 0.76-1.14; P = 0.48)
Keeley et al[12] (NATURE study)	148 STEMI patients till Dec 2014	Randomized, multicentre clinical trial: Compare the safety and efficacy of the enVast™ system as an adjunctive measure to conventional intervention vs the standard of care in STEMI patients with significant thrombus burden	EnVast	The study aims to determine if the enVast™ device can improve procedural success and long-term outcomes in this patient population	The enVast™ thrombectomy catheter represents a promising advancement in treating STEMI patients with significant thrombus burdens. These ongoing studies are expected to provide more definitive evidence regarding its role in improving clinical outcomes

REMEDIA: The randomized evaluation of the effect of mechanical reduction of distal embolization by thrombus-aspiration in primary and rescue angioplasty; TA: Thrombus aspiration; PCI: Percutaneous coronary intervention; ST: St segment; ECG: Electrocardiogram; STEMI: ST elevation myocardial infarction; MBG: Myocardial blush grade; STR: ST segment reduction; MRI: Magnetic resonance image; EXPIRA: Thrombectomy with export catheter in infarct-related artery during primary percutaneous coronary intervention; TAPAS: Thrombus aspiration during percutaneous coronary intervention in acute myocardial infarction study; INFUSE-AMI: Intracoronary abciximab and aspiration thrombectomy in patients with large anterior myocardial infarction; IQR: Interquartile range; TASTE: Thrombus aspiration during ST-segment elevation myocardial infarction; TOTAL: A trial of routine aspiration thrombectomy with percutaneous coronary intervention vs percutaneous coronary intervention alone; CV: Cardiovascular; HR: Heart rate; NATURE (NAtuRE): EnVast as an adjunct primary percutaneous coronary intervention in subjects presenting with coronary occlusions.