Maquet Cardiovascular v. Abiomed — Court Denies Summary Judgment on Doctrine of Equivalents for Blood Pump Patent

Background

Maquet Cardiovascular sued Abiomed for infringing U.S. Patent No. 10,238,783, covering intravascular blood pump technology. The patent claims a blood pressure detection mechanism “comprising a fluid column” disposed within an elongate catheter. Abiomed’s accused products — the Impella 5.0 and Impella CP with SmartAssist — use different pressure-sensing technologies: a differential pressure sensor (piezoelectric) in the Impella 5.0 and an optical pressure sensor (optical fiber) in the Impella CP.

This is the second lawsuit between the parties over intravascular blood pump patents. In March 2025, the Federal Circuit vacated an earlier noninfringement judgment in this case, holding that the district court had misapplied prosecution disclaimer when construing claim terms, and remanded for further proceedings. On remand, Abiomed moved for partial summary judgment, arguing that Maquet’s doctrine-of-equivalents theory would improperly vitiate the “fluid column” limitation from the patent claims.

The Court’s Holding

Judge Saylor denied both of Abiomed’s summary judgment motions. The first motion, seeking invalidation of claim 2 for lack of written description, was denied as moot because Maquet voluntarily withdrew that claim.

The central dispute concerned the doctrine of equivalents applied to claims 3 and 24. Abiomed argued that finding equivalence between a fluid-column pressure sensor and either a differential or optical sensor would vitiate the “fluid column” limitation entirely — effectively reading it out of the patent. The court acknowledged this principle but found Maquet was not arguing that “any pressure sensing structure” would be equivalent. Instead, Maquet’s expert, Boris Leschinsky, provided detailed function-way-result analyses for each specific accused product.

For the Impella 5.0, Leschinsky opined that the differential pressure sensor performs substantially the same function (detecting blood pressure), in substantially the same way (communicating pressure from the pump location through the catheter to the console via deflection of a diaphragm), to achieve the same result. For the Impella CP, he offered a parallel analysis for the optical fiber sensor. The court found these analyses created genuine disputes of material fact that must be decided at trial.

The court also rejected Abiomed’s ensnarement defense, finding that Abiomed had not met its initial burden of production to identify prior art that would be ensnared by Maquet’s equivalents theory. Abiomed waited until after the close of fact discovery to raise this defense, and the court held the issue was not ripe for summary judgment.

In a notable aside, Judge Saylor criticized the doctrine of equivalents itself, calling it “fraught with problems” that “tend[] to reward poor draftsmanship, promote gamesmanship, and increase litigation expense and risk,” and observing that it “conflicts with the definitional and public-notice functions of the statutory claiming requirement.” Nevertheless, he applied binding precedent and denied the motion.

Key Takeaways

• The vitiation doctrine does not bar doctrine-of-equivalents claims targeting specific alternative technologies — it only bars theories so broad they would encompass any structure performing the claimed function, effectively reading a limitation out of the patent.
• Expert testimony providing a detailed function-way-result analysis for each specific accused product can create triable issues of fact, even when the accused technology uses a fundamentally different physical phenomenon (optical vs. hydraulic vs. electrical).
• The burden of production on ensnarement rests initially on the party asserting it — the accused infringer must first identify specific prior art that would be ensnared before the patentee is required to propose a hypothetical claim.
• Judge Saylor’s criticism of the doctrine of equivalents, while dictum, reflects a growing judicial skepticism that may influence future Federal Circuit attention to this area of law.

Why It Matters

This ruling keeps alive a high-stakes patent dispute over billion-dollar medical device technology. Abiomed’s Impella devices are the market-leading percutaneous heart pumps, and Maquet’s patent family has been the subject of extensive litigation between these parties for nearly a decade. The decision signals that patent holders can pursue infringement claims under the doctrine of equivalents even when the accused product uses an entirely different sensing technology — provided they anchor their expert analysis to the specific accused product rather than arguing for equivalence to an entire category of alternatives. For medical device companies and patent practitioners, the ruling underscores the importance of detailed claim-by-claim, element-by-element expert analysis when pursuing or defending against equivalents theories.