Use of a device and system to clear dislodged "debris" during percutaneous interventions to open a blocked artery following a heart attack does not appear to be clinically beneficial, according to a study in the March 2 issue of JAMA.
Dislodgement of atheromatous (an abnormal fatty deposit in an artery) and thrombotic (blood clot) material ("debris") during percutaneous coronary intervention (PCI) following a heart attack is common. This debris may travel to more distal smaller vessels (beyond the site of arterial blockage) and may result in microcirculatory dysfunction. Prevention of this "distal embolization" may improve reperfusion success, reduce the damage caused by a blocked artery, and enhance event-free survival.
A procedure commonly used with PCI involves use of a specialized guidewire and catheter device to collect liberated embolic debris in the artery. Pilot studies and small randomized trials have demonstrated that distal (situated beyond the point in the obstructed artery) protection of the microcirculation during primary PCI retrieves embolic debris in most patients and may result in greater rates of normal blood flow, improved left ventricular function, and enhanced event-free survival compared with controls.
Gregg W. Stone, M.D., of Columbia University Medical Center and Cardiovascular Research Foundation, New York, and colleagues performed a clinical trial to evaluate the usefulness of distal microcirculatory protection during mechanical reperfusion therapy in acute myocardial infarction (AMI). The randomized controlled trial was conducted at 38 academic and community-based institutions in 7 countries, enrolling 501 patients aged 18 years or older with ST-segment elevation myocardial infarction (STEMI) presenting within 6 hours of symptom onset and undergoing primary PCI or rescue intervention after failed thrombolysis.
The patients were randomized between May 20, 2002, and November 21, 2003 to receive PCI with a balloon occlusion and aspiration (removal by suction of dislodged debris) distal microcirculatory protection system vs. angioplasty without distal protection.
Among 252 patients assigned to the distal protection group, aspiration was performed in 97 percent (242/251), all angioplasty balloon inflations were fully protected in 79 percent (193/245), and visible debris was retrieved from 73 percent (182/250). Complete ST-segment resolution (STR) was achieved in a similar proportion reperfused with vs. without the distal protection device (63.3 percent vs. 61.9 percent, respectively; and left ventricular infarct size was similar in both groups. Major adverse cardiac events at six months occurred with similar frequency in the distal protection group and in the control group.
"We did not identify clinical usefulness of distal microcirculatory protection in AMI, and its routine use in patients undergoing mechanical reperfusion therapy cannot be recommended.
Multiple explanations may be proposed as to why distal microcirculatory protection failed to enhance myocardial reperfusion success, reduce infarct size, or improve clinical outcomes in the present trial. First, the device may not have been efficient enough in aspirating liberated atherothrombotic debris," the authors write. "Second, the additional median 21-minute delay to angioplasty in the distal protection group or the several extra minutes of additional balloon occlusion may have increased infarct size and worsened clinical outcomes, offsetting the potential benefit of emboli removal, though most prior studies have suggested that this degree of delay at a median reperfusion time of 3.6 hours would be unlikely to affect myocardial salvage or survival."