Maquet v. Abiomed — Court Issues Three Pre-Trial Rulings on Blood Pump Patent, Preserves Written Description Challenge but Strikes Indefiniteness and Means-Plus-Function Arguments

Background

Maquet Cardiovascular LLC and Abiomed have been litigating over intravascular blood pump patents since 2016. This is the second lawsuit between the parties (Abiomed II), focused on U.S. Patent No. 10,238,783, which covers guidance systems for miniaturized pumps inserted through a patient’s blood vessels to support a failing heart.

At the center of the dispute is a fundamental design difference: the ‘783 patent’s specification describes only cable-driven blood pumps — devices where an external motor turns the pump rotor via a flexible cable threaded through the patient’s vasculature. But the patent’s claims use the broader term “intravascular blood pump” without limiting it to any particular drive mechanism. Abiomed’s accused Impella devices use a different architecture entirely: a miniaturized internal motor that sits inside the heart itself.

After the Federal Circuit vacated the district court’s claim construction in March 2025 and partially reversed again in February 2026, the case returned to Judge Saylor for trial preparation. With trial set for May 11, 2026, the court issued three significant pre-trial rulings in the span of one week.

The Court’s Holdings

May 1: Written Description and Indefiniteness (Doc. 663)

Maquet moved for partial summary judgment to eliminate four of Abiomed’s invalidity defenses. The court issued a mixed ruling:

Indefiniteness — Granted for Maquet. The court struck Abiomed’s indefiniteness challenges to the terms “partially disposed” (claim 24) and “elongate catheter” (claim 3). For “partially disposed,” Abiomed conceded it would not present the issue to the jury. For “elongate catheter,” the court found Abiomed’s argument was really about breadth, not definiteness — quoting Nautilus: “Breadth is not indefiniteness.”

Written description — Denied (triable issue survives). The critical ruling: the court refused to eliminate Abiomed’s argument that the ‘783 patent’s cable-only disclosure cannot support claims covering all intravascular blood pumps, including internally-driven ones. Judge Saylor identified three potentially applicable legal frameworks: the “unclaimed feature” doctrine, the “genus/species” line of cases, and the ICU Medical/LizardTech line holding that a narrow specification can invalidate an overly broad claim.

The court acknowledged Maquet’s argument that the drive mechanism is unclaimed and therefore need not be described. But it rejected a blanket rule, reasoning that an intravascular blood pump is “not just a fluid pump, adaptable to any conventional form of propulsion” — it is a “highly sophisticated miniaturized device that must be guided to, and then operate in, an extraordinarily challenging environment — the beating heart of a live human being.” Abiomed’s expert testified that the differences between cable-driven and internally-driven pumps were significant and unpredictable, creating a genuine factual dispute for trial.

Enablement — Denied. The court found the enablement issue would be resolved by the written description dispute and declined to grant summary judgment on either side.

May 4: Reverse Doctrine of Equivalents Survives (Doc. 677)

In a notable ruling on patent defense doctrine, Judge Saylor addressed whether the reverse doctrine of equivalents (RDOE) — which excuses literal infringement when the accused product operates on a fundamentally different principle — remains viable. The Federal Circuit’s 2025 decision in Steuben Foods v. Shibuya Hoppman Corp. called the doctrine’s viability into serious question, with the court finding the arguments for abolishing it “compelling” while declining to actually rule.

Judge Saylor acknowledged this puts trial courts in a “difficult position” but concluded he must “apply the law as it exists” rather than predict what the Federal Circuit might do in a future case. The defense remains alive, will be tried to the jury (not the court sitting in equity), and its applicability on the facts will be determined at trial.

May 6: Supplemental Claim Construction Denied (Doc. 685)

Abiomed sought, one month before trial, to construe the term “guide mechanism comprising a lumen” in claim 1 as a means-plus-function term under 35 U.S.C. § 112(f). It pointed to the Federal Circuit’s February 2026 affirmance of the court’s prior means-plus-function construction of a similar “guide mechanism” term in a related patent. The court found waiver: Abiomed had six years to raise this argument, previously filed and then withdrew a similar motion without explanation, and was now seeking to inject a potentially case-dispositive theory one month before trial. The court also rejected the argument that recent Federal Circuit decisions constituted “changed circumstances,” noting Abiomed had the relevant precedent in hand when claim construction proceedings began.

Key Takeaways

• Written description is headed to trial. Whether a patent specification disclosing only one type of drive mechanism (cable-driven) can support claims broad enough to cover a fundamentally different architecture (internally-driven motor) is a factual question the jury will decide. This has implications for any patent where the specification describes one embodiment but claims a broader genus.
• The reverse doctrine of equivalents is on life support. Judge Saylor’s candid acknowledgment that the Federal Circuit has all but signaled it will abolish the RDOE — while faithfully applying it anyway — highlights the doctrine’s precarious status. Defendants considering this defense should be aware it may not survive appellate review.
• Claim construction waiver is real. Parties that sit on claim construction arguments for years, or withdraw motions and then refile them on the eve of trial, risk losing those arguments entirely — even when intervening appellate decisions arguably support the proposed construction.
• “Unclaimed feature” is not a magic bullet. The court rejected Maquet’s argument that because the patent claims don’t recite a drive mechanism, the specification need not address different types. For complex, highly specialized technology, the unclaimed-feature doctrine may not apply when the undisclosed feature is integral to the invention’s operation.

Why It Matters

This trio of rulings sets the stage for a high-stakes trial in one of the most significant medical device patent cases in recent years. The written description issue has broad implications: as patents increasingly claim broad functional results while disclosing narrow implementations, courts must decide when a specification that teaches one approach is sufficient to cover a fundamentally different one. The court’s refusal to apply the “unclaimed feature” doctrine as a categorical rule — and its emphasis on the complexity and unpredictability of the technology — suggests that patentees in the medical device space cannot assume broad claims will survive validity challenges simply because they chose not to claim the distinguishing feature.

The reverse doctrine of equivalents ruling also deserves attention beyond this case. Judge Saylor’s opinion is a model of judicial restraint — acknowledging the strong signals from the Federal Circuit while declining to anticipate a ruling that hasn’t happened yet. The defense’s uncertain future means that any party planning to rely on it should have robust alternative defenses ready.