Acute Inferior ST-Segment Elevation Myocardial Infarction
Treated with Primary Angioplasty Using Only a Pronto
Aspiration Cath

The benefits of adjunctive mechanical devices to prevent distal embolization in patients undergoing mechanical revascularization for acute myocardial infarction (AMI) are still a matter of debate.

Case Report. A 34-year-old male smoker with dyslipidemia and no prior cardiac history presented to the emergency department of a community hospital within 1 hour of the onset of chest pain that awakened him early in the morning. The pain was radiating to the spine and to the elbows and was accompanied by nausea and diaphoresis. His blood pressure was 135 over 85 and his heart rate was 58 bpm. The electrocardiogram (ECG) revealed ST-segment elevation in leads III and aVF, and ST-segment depression in leads I and aVL. After initiation of medical therapy which included aspirin, clopidogrel, enoxaparin subcutaneously and nitrates intravenously, the pain resolved and thrombolytic therapy was not administered. The patient was transferred for further evaluation and treatment.

Upon arrival to our institution, the patient had mild chest pain. An ECG still showed ST-segment elevation (1 to 2 mm) in leads III and aVF, with shallow Q waves, and the R waves were preserved. In addition, ST elevation was present in the right precordial leads RV4–RV6. The patient underwent coronary angiography, which revealed a subtotal occlusion of the dominant right coronary artery (RCA) in the middle segment involving the ostium of the acute marginal branch and containing a large amount of thrombus (Figure 1). The left coronary artery was free of significant stenoses. Administration of tirofiban was initiated and coronary intervention proceeded using a 7 Fr right Judkins guiding catheter via the right femoral approach. A 0.014 BMW guidewire (Guidant Corp., Santa Clara, California) was advanced through the lesion. Considering the high likelihood for embolization (due to the large amount of thrombus), a Pronto V3 thrombus extraction catheter (Vascular Solutions, Inc., Minneapolis, Minnesota) was used in an attempt to remove as much thrombus as possible. After a few runs of aspiration, a significant amount of thrombus was extracted and this was consistent with the reduced thrombotic burden as estimated by angiography (Figure 2). Further runs of aspiration resulted in embolization of large pieces of thrombus, causing total occlusion of the vessel proximal to the crux (Figure 3). Most of this thrombus was also extracted after multiple runs of aspiration with the Pronto catheter. The orthogonal views recorded subsequently revealed no significant residual stenosis (Figures 4A and B), obviating the need for further intervention. Removal of some embolic material embolized at the distal posterolateral branch was not attempted because the diameter of the branch was less than 2 mm. The patient had an uncomplicated hospital course and was discharged 5 days later with a regimen that included aspirin, clopidogrel, a statin, an angiotensin-converting enzyme inhibitor and a betablocker. Three months later, he was asymptomatic and underwent a maximal exercise stress test which showed no evidence of ischemia.

Discussion. Despite successful epicardial revascularization, suboptimal myocardial perfusion may occur in 20–40% of patients, with a significant impact on long-term survival.¹ Macroscopic distal embolization may occur in up to 16% of patients undergoing primary angioplasty,² and atherosclerotic debris may be retrieved from 70–95% of patients undergoing primary angioplasty with distal protection devices.³ Proximal or distal protection devices and thrombectomy catheters have been used to prevent distal embolization.
A recent meta-analysis of all randomized trials with mechanical devices to prevent distal embolization in primary angioplasty demonstrated that the use of these devices is associated with better myocardial perfusion and less distal embolization, but without any apparent improvement in survival.⁴ Angiographic evidence of thrombus was required in a minority of trials, and it is possible that adjunctive mechanical devices are most effective in the setting of a large thrombus burden.
The Pronto V3 catheter is a simple, user-friendly, singleoperator, monorail, hydrophilically-coated, dual-lumen catheter designed for the removal of fresh, soft emboli and thrombi from the arterial system. While the smaller-wire lumen accommodates the guidewire, the large-sloped atraumatic extraction lumen allows for removal of thrombus by using simple vacuum suction with a syringe. Its use was reported previously as an adjunctive device in patients undergoing mechanical revascularization in acute myocardial infarction^5,6 and in the treatment of stent thrombosis.⁷

We report on the use of the Pronto catheter to treat a case of acute ST-segment myocardial infarction. Although our aim was to use the Pronto catheter as an adjunctive device to reduce the thrombotic burden before proceeding to stent implantation, thrombus aspiration proved so effective and residual stenosis was so trivial, that no further intervention was finally needed.
It is well recognized that myocardial infarction commonly follows the rupture of a plaque that did not cause a significant stenosis previously. Therefore, removal of the thrombotic material may be expected to reveal a nonsignificant residual stenosis in such cases. Nevertheless, mechanical treatment of AMI with the sole use of a thrombectomy device is not commonly reported.
To the best of our knowledge, this is the second reported case of AMI treated mechanically with the sole use of a Pronto extraction catheter without further balloon dilatation or stent implantation. In the only other case that was reported previously, the Pronto catheter was used in the treatment of AMI after coronary embolism post mitral valve replacement.⁸ A tubular structure was recovered in that case and repeat angiography revealed no atherosclerotic stenosis. AMI caused by coronary embolism is an unusual situation. In our patient, altered rheology in the aneurysmal dilatation just proximal to the occlusion could have predisposed him to thrombus formation, but there is no evidence to support the hypothesis that the myocardial infarction was due to embolism. Most likely, the infarction occurred following the rupture of an atherosclerotic plaque that was not significant previously.
During the procedure, embolization occurred, but it was successfully treated with the same catheter. This embolization may have been due to shifting of thrombotic material by the catheter, or it may have been related to the technique applied. Maintaining suction during the entire procedure may be of critical importance.⁹ If negative pressure is lost (by turning the stopcock to the “off” position, or when the aspiration syringe is filled completely with blood), the thrombus that remains in the vessel may be free to embolize, with no more vacuum holding it. Aspirating the guiding catheter after removing the Pronto has been proposed as an effective way to decrease the risk of embolization.⁹ Aspiration of the thrombus embolized at the posterolateral branch was not attempted, as the use of the Pronto catheter is contraindicated in vessels less than 2 mm in diameter.

 

References
1. De Luca G, van 't Hof AW, Ottervanger JP, et al. Unsuccessful reperfusion in patients with ST-segment elevation myocardial infarction treated by primary angioplasty. Am Heart J 2005;150:557–562.
2. Henriques JP, Zijlstra F, Ottervanger JP, et al. Incidence and clinical significance of distal embolization during primary angioplasty for acute myocardial infarction. Eur Heart J 2002;23:1112–1117.
3. Stone GW, Webb J, Cox DA, et al. Distal microcirculatory protection during percutaneous coronary intervention in acute ST-segment elevation myocardial infarction: A randomized controlled trial. JAMA 2005;293:1063–1072.
4. De Luca G, Suryapranata H, Stone GW, et al. Adjunctive mechanical devices to prevent distal embolization in patients undergoing mechanical revascularization for acute myocardial infarction: A meta-analysis of randomized trials. Am Heart J 2007;153:343–353.
5. Lim MJ, Reis L, Ziaee A, Kern MJ. Use of a new thrombus extraction catheter (the Pronto) in the treatment of acute myocardial infarction. J Interv Cardiol 2005;18:189–192.
6. Pershad A, Hoelzinger D, Patel S. Pronto catheter thrombectomy in acute ST-segment myocardial infarction: A case series. J Invasive Cardiol 2006;18:E191–194.
7. Siddiqui DS, Choi CJ, Tsimikas S, Mahmud E. Successful utilization of a novel aspiration thrombectomy catheter (Pronto) for the treatment of patients with stent thrombosis. Catheter Cardiovasc Interv 2006;67:894–899.
8. De Young MB, Kazziha S. Use of a thrombus extraction catheter (Pronto) in the treatment of acute myocardial infarction after coronary embolism post mitral valve replacement. J Invasive Cardiol 2006;18:E273–E275.
9. Mallavarapu RK, Culclasure TF Jr, James EA. The Pronto catheter: Distal embolization of any remaining thrombus fragments may be a risk of creating and then removing negative pressure (letter). J Invasive Cardiol 2007;19:285.