Case presentation

After experiencing a 1-month history of intermittent chest discomfort, a 47-year-old man suddenly developed severe left-sided chest pain while loading a truck. The chest pain continued despite stopping to rest and was associated with nausea, diaphoresis, and light-headedness. He drove himself to a hospital without the capacity to perform primary angioplasty. In the emergency room, he was discovered to have an acute ST-segment elevation inferoposterior myocardial infarction, and the emergency room physician administered sublingual nitroglycerin without relief of pain. The patient was within 1 hour of symptom onset and the treating physician decided to reperfuse with thrombolysis rather than delay reperfusion in order to transfer to a hospital with PCI capability. Therefore, while still in the emergency room, the patient received aspirin, clopidogrel, and tenecteplase, along with enoxaparin (30 mg intravenously and 100 mg subcutaneously). Twenty-five minutes after receiving thrombolysis, the patient noted improvement in chest pain. A repeat electrocardiogram confirmed near complete resolution of ST-segment elevation. Unfortunately, approximately 30 minutes later, his chest pain returned, along with marked ST-segment elevation, hypotension, and bradycardia. At this point, the emergency room physician decided to transfer the patient for rescue intervention, to a hospital 60 minutes away by helicopter.

Upon arrival, the patient continued to report chest pain, and there remained persistent ST-segment elevation present on the electrocardiogram. A review of the patient’s medical history was relevant only for ongoing tobacco abuse and a family history of premature coronary disease. Physical exam was notable for a heart rate of 69 bpm, a blood pressure of 105/63 mmHg, elevated neck veins, and clear lung fields. Initial troponin I was normal and all other laboratory evaluations were within normal limits. He was taken emergently to the cardiac catheterization laboratory.

Cardiac catheterization

The patient arrived in the cardiac catheterization laboratory approximately 2 hours after receiving thrombolysis. As expected, the right coronary artery was completely occluded (Figure 14-1). There was no significant obstructive disease noted in the left coronary arteries. An additional intravenous bolus of enoxaparin was administered, along with a bolus plus infusion of eptifibatide. The operator inserted a guide catheter and easily passed a 0.014 inch floppy-tipped guidewire to the distal artery. A 2.5 mm by 20 mm long compliant balloon inflated at the occlusion site immediately restored TIMI-3 flow, and resulted in resolution of chest pain and ST-segment elevation. However, an extensive filling defect was observed, consistent with a large intracoronary thrombus (Figure 14-2 and Video 14-1). The operator passed a Pronto extraction catheter over the floppy-tipped guidewire to the distal artery and, using a 30 cc syringe, gently aspirated as the catheter was withdrawn to the guide catheter. A large amount of clot was successfully removed and improved the angiographic appearance of the artery with no evidence of distal embolization (Figure 14-3 and Video 14-2). A 4 mm diameter by 28 mm long bare-metal stent postdilated with a 4.5 mm noncompliant balloon successfully treated the residual stenosis (Figures 14-4, 14-5 and Video 14-3). At the completion of the procedure, the patient had no further chest pain and was transferred to the coronary care unit.

FIGURE 14-1 This is a right coronary angiogram demonstrating complete occlusion of the proximal right coronary artery in a patient with an acute ST-segment elevation inferoposterior myocardial infarction.

FIGURE 14-2 This angiogram, taken after balloon angioplasty of the proximal segment, shows extensive filling defects consistent with thrombus within the lumen of the artery (arrows).

FIGURE 14-3 After aspiration of thrombus, the filling defects are gone. There are residual stenoses present (arrows).

FIGURE 14-4 A bare-metal stent was placed in the proximal artery.

FIGURE 14-5 Final angiographic result after stenting.

Postprocedural course

After a femoral angiogram confirmed puncture of the common femoral artery, the arterial sheaths were removed in the cardiac catheterization laboratory and hemostasis achieved with a closure device. The patient completed a 14-hour course of eptifibatide and remained asymptomatic. Echocardiography showed mildly decreased left ventricular function with inferior hypokinesis. The remainder of his hospital stay was uneventful, and he was discharged 72 hours after admission on aspirin, clopidogrel, metoprolol, lisinopril, and atorvastatin. At follow-up 6 months and again 1 year following the procedure, he remained completely asymptomatic and off cigarettes.

Discussion

Using angiographic criteria, a thrombus is definitely present when a filling defect surrounded by contrast on all sides is observed within the lumen of a coronary artery. Typically, the clot appears to dangle from the distal end of an atherosclerotic plaque of varying severity. A probable thrombus is defined by the presence of a hazy or “washed-out” appearance to the lesion. However, angiography is not very sensitive for thrombus; angioscopy is better at identifying intracoronary clot but is not used clinically. Intravascular ultrasound is not useful because organized thrombus usually appears indistinguishable from a fatty plaque.

Angiographic thrombus is most often encountered in patients undergoing an intervention for acute coronary syndromes. Visible clot often occurs in patients with ST-segment elevation infarction. Similarly, patients undergoing PCI for failed thrombolysis (i.e., rescue angioplasty), as demonstrated in this case, also are likely to have a large thrombus burden. The presence of visible clot is a high-risk feature and is associated with a higher rate of death, myocardial infarction, and abrupt vessel closure,¹ and is also associated with other adverse angiographic outcomes such as failure to achieve TIMI-3 flow post-PCI for acute MI, development of no-reflow phenomenon, and distal embolization.

Adjunctive pharmacology helps reduce the risk of complication from PCI in the setting of visible thrombus. Antiplatelet agents are highly efficacious in this setting and both pretreatment with aspirin and clopidogrel and the adjunctive use of the glycoprotein IIb/IIIa inhibitors are essential for success. Additionally, it is important to achieve an adequate antithrombin effect. If unfractionated heparin is used, the activated clotting time (ACT) should be at least within the therapeutic range (>200 seconds if a glycoprotein IIb/IIIa inhibitor is used); some operators prefer higher levels (250 to 300 seconds) in the presence of a visible clot. Although anecdotal reports abound, the role of intracoronary glycoprotein IIb/IIIa inhibitors or intracoronary lytics has not been well established in a randomized controlled manner.² Similarly, although bivalirudin is an effective antithrombin agent for PCI in the setting of acute myocardial infarction (especially if pre-loaded with clopidogrel), the efficacy of this agent without glycoprotein IIb/IIIa inhibitors for PCI in the setting of visible thrombus is unclear.

Numerous mechanical methods have been developed for physical removal of the thrombus. The more complex devices such as the rheolytic thrombectomy device (Angiojet) and an atherectomy-type device (X-Sizer catheter) have not been shown to be beneficial and may be associated with increased risk of adverse outcomes, likely due to distal embolization.^3,4 Aspiration catheters are simply large-bore catheters that use manual aspiration with a syringe to remove clot. They are highly effective at removing clot and employ much simpler techniques and more limited device inventory than the more complex devices. Importantly, aspiration devices have been shown to improve outcomes when used routinely in patients with ST-segment elevation myocardial infarction.⁵ Distal protection devices have not shown benefit when applied routinely to patients with STEMI;⁶ whether they are helpful in preventing distal embolization in patients with large, visible thrombus such as this case is unclear.