600,000 Heart Procedures, Only 7,000 Trial Patients: The Evidence Gap

Closing the pocket looks like a straightforward fix. It isn't a complete one, though. The procedure doesn't remove every possible source of blood clots, and the device itself can sometimes become a spot where clots develop.

Why did researchers doubt the evidence?

The Mass General Brigham team reviewed the major trials of the procedure and found several weaknesses in how it was tested:

• Small numbers. Over 600,000 procedures performed globally, but randomized trials covered just over 7,000 participants.
• Inconsistent designs. The trials enrolled different kinds of patients, used different devices and followed people for different lengths of time, making direct comparisons hard.
• Outdated comparators. Some studies tested the procedure against warfarin, an older blood thinner, rather than the newer medications many patients take today. A result against an older drug may not show which option is best now.
• A weaker bar for success. Many trials were designed to test whether the procedure was not much worse than medication — not whether it was better at preventing strokes.

What happens when patients stop medication afterward?

The review flagged another reason for caution. When patients stopped taking clot-preventing medicines after the procedure, researchers found warning signs, including possible clots in the veins.

The procedure also carries immediate risks of its own. Those have to be weighed against the ongoing bleeding risks that come with staying on medication — a balance that varies from patient to patient.

Does this mean the procedure should be abandoned?

No. The findings don't rule out closure for everyone. For selected people who cannot safely continue long-term blood thinners, the procedure may remain a reasonable option.

The review's central lesson is that treatment choice shouldn't be driven by convenience alone. And the analysis has its own limits: because it's a review of existing trials rather than a new head-to-head study, it can't settle every open question.

More directly comparable trials are needed, the researchers argue, before doctors can confidently expand use of the procedure. Until then, the 600,000-procedure count keeps growing faster than the evidence base behind it.