Mechanical Thrombectomy Catheter Systems

Mechanical Thrombectomy Catheter Systems

Haude Michael
Interventional Cardiology 2007
Published: October 2007
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Myocardial infarction (MI) is the leading cause of death worldwide in both men and women.1 An impending infarction is recognised by ST elevation, which is predominantly the result of an occlusive thrombosis in a coronary artery.

An immediate goal in MI is to restore blood flow through the occluded coronary artery. Reperfusion is carried out using primary percutaneous coronary intervention (PCI) or thrombolytic therapy; as a last resort, a coronary bypass is performed. For acute ST segment elevation, the benefits of prompt primary PCI have long been proved to be superior to those of thrombolytic therapy and coronary bypass.2

Primary PCI involves performing a coronary angiogram to determine the precise location of the infarcting vessel, followed by angioplasty. Typically, a balloon-tipped catheter is threaded through the thrombus and then inflated, widening the coronary artery. In most cases, reperfusion is successful with primary PCI; however, macro- and microembolisation of thrombotic debris occurs frequently, which may disrupt microvessel blood flow. This is where mechanical thrombectomy, which involves the use of a catheter system with a mechanical attachment, for example a pump, is advantageous. Mechanical thrombectomy allows removal of the vast majority of thrombus burden and hence prevents sections of the thrombus from travelling downstream, thus eliminating the risk of embolism. Despite the superiority of mechanical PCI for MI, systemic thrombolysis is currently the most widely used treatment.3 In the US, the thrombectomy procedure is restricted to hospitals with or in reach of cardiac surgery facilities in case of complications, and can be performed only by surgeons who participate in more than 75 procedures per year.4,5 This limits the number of facilities able to carry out the procedure.

Mechanical Thrombectomy Catheter Devices
There are several devices for mechanical thrombectomy that differ considerably in construction, principles of operation and management.6–8

Aspiration Thrombectomy
Aspiration thrombectomy uses an 8 or 9F guiding catheter placed through a 10F arrow sheath to form a double-layered catheter.9

Aspiration is carried out manually through suction with a 60ml syringe. Manual aspiration thrombectomy effects were examined on myocardial perfusion and left ventricular remodelling in 78 patients with ST-segment elevation and clear evidence of an intracoronary thrombus.10 Significant benefits were noted in patients treated with the aspiration device. However, because of the small scale of the trial, no conclusions can be drawn about the clinical outcome of the technique.

Rheolytic Thrombectomy
Rheolytic thrombectomy involves a high-velocity jet of saline solution ejected from a drive unit control console to create a Venturi effect at the tip of a 5F catheter.9 In essence, the Venturi effect creates a pressure gradient where the pressure is lower in the catheter than in the vessel, so the thrombi are sucked into the catheter tip. Several small-scale studies demonstrate the benefits of using this technique.11–13 However, the AngioJet Rheolytic Thrombectomy In Patients Undergoing Primary Angioplasty for Acute Myocardial Infarction (AIMI) study concluded that there were no benefits in terms of reduced infarct size or in thrombolysis in MI, and that this technique had an increased risk of major adverse cardiac events.13 This trial was on a much larger scale than previous studies, including 480 patients across the US and Canada over three years. Further studies need to be carried out in order to come to a conclusion regarding the effectiveness of rheolytic thrombectomy in reperfusion.

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