Groningen, the Netherlands - The use of thrombus aspiration to prevent the embolization of atherothrombotic debris during PCI results in better reperfusion and clinical outcomes compared with conventional PCI, a new study has shown [1]. Investigators say that manual aspiration can be performed in a large majority of patients presenting with ST-segment-elevation MI, irrespective of their clinical and angiographic features, such as a visible thrombus on angiography.

Lead investigator Dr Tone Svilaas (University Medical Center Groningen, the Netherlands) and colleagues also observed a significant relationship between myocardial and electrocardiographic variables or reperfusion and rates of death and major adverse cardiac events, supporting "the validity of these reperfusion variables as surrogate end points in patients who have myocardial infarction with ST-segment elevation."

In an editorial accompanying the published study [2], Dr George Vetrovec (Virginia Commonwealth University, Richmond) said that on the basis of these data, thrombus extraction is "conceptually sound and appears to reduce the risk among patients undergoing primary PCI." He notes, however, that operators were from a single center, and all were highly experienced interventionalists with low failure rates, and it is unknown "whether more general use will demonstrate similar safety and favorable outcomes."

The study, known as Thrombus Aspiration During Percutaneous Coronary Intervention in Acute Myocardial Infarction Study (TAPAS), and the editorial are published in the February 7, 2008 issue of the New England Journal of Medicine.

Microvascular obstruction, which is related to plaque embolization or downstream thrombotic particles in the infarcted artery, results in diminished myocardial perfusion, and this event, note the authors, is associated with an increased infarct size and increased mortality. This has led to the development of various devices to protect microcirculation, some of which have been successful, while other devices have not.

In this study, the operators used a 6-French compatible manual-aspiration catheter, a device they say is "relatively flexible and nontraumatic in use," to evaluate whether aspiration could improve perfusion during PCI. In total, 1071 patients with ST-segment-elevation MI were randomly assigned to treatment—thrombus aspiration during PCI or conventional PCI—before coronary angiography was performed, thus eliminating considerations of angiographic selection criteria.

Results showed that aspiration before stenting resulted in improved myocardial reperfusion, as documented by improvements in myocardial blush grade, increased resolution of ST-segment elevation, and reduced residual ST-segment deviation. The benefit, as noted, was consistent across all patients, regardless of baseline clinical or angiographic characteristics such as age, sex, the infarct-related coronary artery, preprocedural TIMI flow, or visible thrombus on the angiogram.

Clinical outcomes at 30 days, including major bleeding, death, reinfarction, target-vessel revascularization, and major adverse cardiac events (MACE), were not statistically different between the two treatment arms. The rates of death and MACE, however, were both significantly related to myocardial blush grade, resolution of ST-segment elevation, and ST-segment deviation, an association that confirms "the prognostic value of the myocardial blush grade and degree of resolution of the ST-segment elevation after reperfusion," write the authors.

Of those who underwent aspiration during PCI, thrombus was retrieved in 73% of patients, and histopathological study confirmed earlier observations that thrombi are predominantly composed of platelets in ST-segment-elevation MI patients, the authors add.

In his editorial, Vetrovec notes that one of the concerns with aspiration during PCI is that the catheters can damage or dissect the artery, which results in the need for longer stents, something that could increase the risk of late restenosis.

Thrombus aspiration appears to be such a favorable improvement.

He also points out that patients undergoing conventional PCI in the TAPAS study had balloon angioplasty followed by stenting. Some operators, he writes, believe that direct stenting without multiple balloon inflations can reduce the risk of distal emboli and that this difference—those in the thrombus-aspiration group had stents placed directly—could affect the results.

Vetrovec writes that the risk of death associated with early reperfusion in acute MI is low and any refinements to PCI can be expected to make only small, albeit clinical meaningful, improvements in outcome. "Thrombus aspiration," he writes, "appears to be such a favorable improvement."