Thrombus Aspiration as Definitive Mechanical Intervention for<br />
ST-Elevation Myocardial Infarction: A Report of Five Cases

The primary goal of treatment in patients presenting with ST-elevation myocardial infarction (STEMI) is reperfusion of the infarcted myocardium. Percutaneous coronary intervention (PCI) has emerged as preferred reperfusion therapy for STEMI.¹ To protect the microcirculation against distal embolization during primary PCI, various mechanical devices have been developed. Randomized controlled trials have demonstrated that manual thrombus aspiration for STEMI is safe and results in improved myocardial perfusion when compared with conventional angioplasty.^2–4 In some patients, thrombus aspiration itself results in complete restoration of epicardial blood flow, without residual stenosis or angiographic signs of plaque rupture at the culprit lesion. It is currently unclear if additional angioplasty is also necessary in these patients. This case report describes 5 patients in whom thrombus aspiration was performed without additional angioplasty as treatment for STEMI.

Methods
Population. Between January 2005 and March 2007, thrombus aspiration was performed to prepare the occluded vessel for stent implantation in 533 patients with acute STEMI.^5,6 We retrospectively analyzed procedural data and selected patients in whom only thrombus aspiration was performed. In 5 patients (0.9%), thrombus aspiration was used as definitive treatment without additional balloon angioplasty or stenting. These 5 patients all had total coronary occlusion (thrombolysis in myocardial infarction [TIMI] flow 0), which was observed in 249 (47%) of all thrombus aspiration patients.
Thrombus aspiration. The Export aspiration catheter (Medtronic, Inc., Santa Rosa, California) (Cases 1, 2, 4 and 5) or the Diver Clot Extraction catheter (ev3, Inc., Plymouth, Minnesota) (Case 3) was used for thrombus aspiration. The Export catheter has an aspiration lumen of 0.041 inches and contains a radiopaque marker located 2 mm from the distal tip. The aspiration lumen of the Diver catheter is 0.062 inches, and the radiopaque marker is located 1 mm from the aspiration tip. After passing the guidewire through the coronary occlusion, the thrombus aspiration catheter was advanced to the proximal side of the occlusion. Thrombus aspiration was performed by hand with a lockable 20 mL syringe that allowed for an aspiration rate of 1 mL/second. The thrombus aspiration catheter was advanced through the coronary occlusion several times, and at least 2 x 20 mL were aspirated to achieve maximal particle aspiration. The syringe was emptied in a filtering cup to separate the aspirated fragments from the blood. Histopathological analysis. The aspirated material was collected for assessment of atherothrombotic characteristics. Aspirated fragments were histologically analyzed for thrombus type and classified as white or red thrombi. White thrombi consisted only of platelet aggregates and red thrombi contained layers of coagulated erythrocytes. In addition, thrombus size was measured and categorized into five groups: 1) residue of small, loosely cohesive platelets; 2) well-formed thrombi < 0.5 mm; 3) 0.5–1 mm; 4) 1–2 mm; and 5) thrombi > 2 mm.
Angiographic analysis. TIMI flow and myocardial blush grade (MBG) were evaluated after thrombus aspiration as previously described.7,8 The percentage of residual stenosis was evaluated by quantitative coronary analysis (QCA). The guiding catheter was used as a reference measurement and residual stenosis was calculated by computerized analysis.
Pharmacologic treatment. After electrocardiographic confirmation of STEMI, all patients received a bolus of acetylsalicylic acid (500 mg), intravenous heparin (5000–10,000 IU) and clopidogrel (600 mg). All patients were treated with abciximab after diagnostic coronary angiography. After sheath removal, low-molecular weight heparin was given. The standard medical therapy after PCI included acetylsalicylic acid (80–100 mg/24 hours), clopidogrel (75 mg/24 hours for 1 month), lipid-lowering agents, β-blockers and angiotensin-converting enzyme inhibitors.

Case 1. An 85-year-old male with a history of 2 PCIs of the right coronary artery (RCA) more than 12 months before presentation was transferred to our hospital under suspicion of an acute myocardial infarction (AMI). He had diabetes, was a smoker and had a body mass index (BMI) of 28. Within 2 hours of symptomonset, coronary angiography was performed, and showed total occlusion of the distal RCA (Figure 1A). Moderate lesion calcification was seen. The left main artery, left anterior descending artery (LAD) and circumflex artery (Cx) contained vessel stenoses up to 50%. Thrombus aspiration was performed in the RCA. Histopathological examination of the aspirated material showed multiple fragments of white thrombi without signs of erythrocytes or plaque material. The size of the aspirated fragments was < 0.5 mm.

After thrombus aspiration, a stenosis of 30% remained in the culprit lesion, as measured by QCA (Figure 1B). No further balloon angioplasty or stenting was performed. TIMI 3 flow and MBG 3 were achieved. Partial ST-segment elevation resolution was seen on the electrocardiography (ECG) with a cumulative persistent ST-segment deviation of 0.5 mV on the first postinterventional ECG. The patient remained asymptomatic 1 year after treatment without any adverse events.
Case 2. A 74-year-old female with no cardiac history or cardiovascular risk factors presented with symptoms of AMI. Her symptom duration was 3.5 hours at hospital admission. Based on the ECG, an apical MI was diagnosed. Angiography showed single-vessel disease with total occlusion in the distal LAD. Thrombus aspiration was performed and the aspirated material in this case contained white platelet aggregates without plaque material or erythrocytes. The size of the aspirated thrombus was > 2 mm. After thrombus aspiration, no additional balloon dilatation or stent implantation was performed. A < 20% stenosis remained and TIMI 3 flow was achieved. However, myocardial perfusion remained impaired after the procedure (MBG 1). The ECG showed partial ST-segment resolution with a cumulative persistent ST-segment deviation of 0.7 mV. Her symptoms rapidly disappeared after thrombus aspiration and the patient had an uneventful course at 1-year follow up.
Case 3. An 87-year-old male with a BMI of 28 and no other cardiovascular risk factors or cardiac history was transferred to our hospital for acute anterior STEMI. His duration of symptoms was 1.5 hours. Angiography showed three-vessel disease with a total occlusion located in the proximal LAD. Thrombus aspiration was successfully performed in the proximal LAD and a stenosis of 35% remained. The aspirated thrombus material of > 2 mm contained layers of coagulated erythrocytes, but no plaque material (Figure 2). No balloon angioplasty or stent placement was performed. TIMI 3 flow and MBG 1 were achieved. The ECG showed complete normalization of the ST segment. At 6-month follow up, the patient remained asymptomatic without additional coronary interventions or adverse cardiac events.

Case 4. A 54-year-old male with a BMI of 41 and a history of smoking presented to our hospital with acute anterior STEMI. He was known to have hypertension, hypercholesterolemia and a positive family history of cardiovascular disease. A small-cell bronchial carcinoma was diagnosed 1 month before presentation and was treated with chemotherapy. The patient’s ischemic time was 5 hours. The angiogram showed a total occlusion in the proximal LAD with extensive thrombosis and ectatic diffuse coronary artery disease. Thrombus aspiration was performed in the LAD, resulting in 25% residual stenosis after the procedure. Multiple red thrombus fragments > 2 mm in size were aspirated. Examination of the aspirated thrombus showed only coagulated erythrocytes. After thrombus aspiration, no additional angioplasty or stenting was performed. TIMI 3 flow and MBG 1 were achieved. The ECG showed partial ST-segment elevation resolution with a residual cumulative ST deviation of 0.4 mV. No additional coronary interventions were performed at follow up. The patient died 10 months after thrombus aspiration from metastasized bronchus carcinoma.
Case 5. A 50-year-old male smoker with a history of MI 5 years previously was transferred to our hospital under suspicion of inferior STEMI. He was known to have hypertension, hypercholesterolemia and a positive family history for cardiovascular disease. Symptom duration was 1.5 hours at hospital admission. Coronary angiography showed a 70% stenosis in the proximal LAD and vessel irregularities in the Cx, with moderate collateral filling. The RCA contained proximal aneurysms and a complete occlusion located distally. Thrombus aspiration was performed in the RCA. Aspirated material was > 2 mm in size, containing erythrocytes, but no plaque material at histopathological examination. A residual stenosis of 35% was measured. No additional balloon angioplasty or stenting was performed. TIMI 3 flow and MBG 3 were achieved and the patient’s symptoms rapidly disappeared. The ECG showed complete normalization of the ST segments. The patient remained event-free 1 year after treatment.

Discussion
These cases demonstrate that when thrombus aspiration results in complete restoration of epicardial blood flow without significant residual stenosis or signs of plaque rupture, additional angioplasty with balloon or stent placement may not be necessary. At follow up, all patients remained event-free, indicating that thrombus aspiration as a standalone therapy was safe and effective in these patients.
Thrombus aspiration without additional angioplasty has only been described before as therapy for coronary embolisms originating from outside the coronary arteries.^9,10 To our knowledge, this is the first report investigating the potential role of thrombus aspiration without additional angioplasty for STEMI caused by occlusive coronary artery disease.
Only 5 out of 249 patients with an acute total coronary occlusion underwent thrombus aspiration for definitive treatment of STEMI. Potentially, more than 5 patients could have been treated with thrombus aspiration as definitive therapy, but our data do not allow any conclusions with regard to how often this strategy can be applied. To gain greater clarity regarding the relevance of residual lesions and the necessity of performing additional PCI after thrombus aspiration, fractional flow reserve (FFR) or intravascular ultrasound (IVUS) measurements may be helpful.¹¹ Earlier studies have shown that elective patients with residual stenoses ≤ 30%^12,13 or ≤ 35% and FFR ≥ 0.9¹⁴ after balloon angioplasty had favorable clinical outcomes at longterm follow up. This may suggest that in patients with minimal residual stenosis, no signs of plaque rupture on angiography and/or IVUS and almost normal FFR, thrombus aspiration alone may result in clinical outcomes comparable with those achieved after additional angioplasty or stenting. Furthermore, as thrombus aspiration is nontraumatic to the vessel wall, eventfree outcomes after thrombus aspiration without additional angioplasty may be related to diminished vessel injury. During balloon angioplasty and stenting, platelet aggregation, inflammation and intimal proliferation are induced and these mechanisms may result in restenosis or reocclusion.¹⁵
We conclude from these 5 cases that the performance of thrombus aspiration alone, without the use of balloon or stenting in the culprit lesion, is safe and effective in selected patients.
Acknowledgment. We appreciate the thoughtful comments of Prof. Dr. F. Zijlstra, Dr. G.F. Diercks and Dr. A.J. Suurmeijer in the preparation of this manuscript.

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