Study Presented of Embolic Protection Devices for SAVR
March 19, 2017—The American College of Cardiology (ACC) announced the presentation of a study demonstrating that two cerebral embolic protection devices that have been cleared by the US Food and Drug Administration for use during surgical aortic valve replacement (SAVR) did not significantly reduce overall number of brain infarcts over standard surgical procedure. The study's lead investigator, Michael Mack, MD, presented the study at the ACC's 66th annual scientific session in Washington, DC.
According to the ACC, approximately two-thirds of patients experienced the study’s primary endpoint: central nervous system infarcts, as measured clinically or with diffusion-weighted magnetic resonance imaging (DW- MRI), at 7 days after the operation. That proportion was approximately the same for patients randomized to receive the standard aortic cannula, the Embol-X device (Edwards Lifesciences), or the CardioGard device (CardioGard Ltd.). The Embol-X filter captures debris as it flows through the artery. The CardioGard is a suction-based device that removes debris and air bubbles from the blood while it is being pumped through a heart-lung machine.
The ACC summary noted that the results are similar to those of a recent trial assessing the use of a comparable medical device with transcatheter aortic valve replacement (TAVR), which also did not show a strong benefit in terms of brain infarcts detected by DW-MRI.
In the ACC announcement, Dr. Mack commented, “Despite the fact that debris was captured—which was the mechanism by which these devices are intended to work—there was no difference in the primary endpoint. However, the vast majority of infarcts were only detectable by postoperative MRI, with fewer than 10% of patients exhibiting clinical symptoms. Moreover, trends with respect to the volume of brain infarction suggest that embolic protection device recipients were less likely to have larger infarcts. This may be important, as the risk of symptomatic stroke increases with infarct volume.”
"There is suggestive evidence that there may be a benefit, despite not meeting the primary endpoint of this trial,” advised Dr. Mack, who is Medical Director for cardiovascular surgery at Baylor Health Care System in Dallas, Texas.
As reported by ACC, the study enrolled 383 patients undergoing SAVR at 18 sites in North America. Patients were randomly assigned to receive either the standard aortic cannula (132 patients), Embol-X (133 patients), or CardioGard (118 patients). The investigators performed separate analyses comparing each of the groups treated with the embolic protection device to those receiving only the standard cannula (controls). Because the trial began with randomizing Embol-X or control, the first 12 control patients served as controls for Embol-X only and 120 patients were common to both control groups. Clinicians tracked damage to the central nervous system using diffusion-weighted MRI scans, neurocognitive assessments, and clinical stroke diagnoses.
The study showed that the devices functioned as intended, capturing debris in 99.1% of patients treated with Embol-X and 75.8% of patients treated with CardioGard. In addition, the results showed a significant reduction in in-hospital delirium at day 7 after surgery in patients receiving the CardioGard device and a trend toward reduced delirium in patients receiving Embol-X. The proportion of patients with clinical strokes based on physical findings by seven days did not differ among patients randomized to receive CardioGard, Embol-X, or standard aortic cannula.
However, there were fewer severe clinical strokes observed in the embolic protection device groups compared to controls in the first 3 days after surgery, although the study was not designed to assess the clinical significance of this observed trend. Neurocognitive outcomes at 90 days were similar between groups, with the exception of executive function decline, which was reduced in patients receiving the Embol-X device. Further study could help to clarify whether these findings may translate into significantly better health outcomes for patients, noted the investigators.
A key limitation of the trial is that it was not large enough to definitively detect differences in the incidence of clinical stroke, which was analyzed as a secondary outcome. The trial was stopped early after an interim analysis showed it was not likely to meet its primary endpoint and, thus, enrolling more patients would likely be futile. It is also possible that DW-MRI is an overly sensitive tool for measuring damage to the brain, hampering investigators’ ability to distinguish between blood vessel blockages that cause actual neurological deficits from those that do not, reported the investigators in the ACC announcement.