At Engenious Design, our team brings more than a decade of experience developing pulsed field ablation systems. Here's what we wish someone had told us before we started.
When R&D teams new to pulsed field ablation (PFA) generator development first encounter the output architecture of these generators, the reaction is usually the same: it seems more complicated than it needs to be. Multiple nested timing loops, a vocabulary that does not map neatly to conventional power electronics, and performance requirements that touch every layer of the hierarchy simultaneously.
Pulse is the fundamental unit. A single pulse is a discrete high-voltage event, typically 500 nanoseconds to 10 microseconds in duration for irreversible electroporation, longer for reversible applications. At 5 kV across a 50-ohm load, a 1.5-microsecond pulse delivers 250 kW instantaneously. This is what actually interacts with tissue at the cellular level.
Pulses can be monophasic (voltage in one direction only) or biphasic (a positive phase followed by a negative phase). The choice has significant implications for both the biological effect and the output stage architecture. Biphasic delivery requires a full H-bridge capable of reversing polarity, and it influences the charge balance on the tissue and the electrode.
Burst is an ordered sequence of pulses with defined interpulse intervals. A burst might contain 100 pulses, each separated by a fixed dead time. The burst is the unit of therapeutic delivery that a clinician or researcher thinks about when designing a protocol: the accumulated effect of a burst on tissue is the outcome being engineered. Burst-to-burst consistency matters enormously. If the output stage or energy storage architecture behaves differently at pulse 90 of a burst than at pulse 1, the delivered therapy is not what the protocol specifies.
Packet is an ordered sequence of bursts with defined interburst intervals. Between packets, there is typically a longer idle period ranging from hundreds of milliseconds to several seconds. This structure allows tissue to respond between high-dose delivery events and gives the generator’s energy storage time to recover. The packet is often the unit used to structure a complete treatment.
The nested timing structure is not just a software concern, it propagates directly into hardware requirements.
The energy storage system must support instantaneous power delivery at the pulse level while recovering within the interburst and interpacket intervals. If the capacitor bank does not recover fully between bursts, pulse fidelity degrades across the burst. This is one of the more common – and difficult-to-diagnose – failure modes in early pulsed field ablation generator prototypes: everything looks correct at the pulse level in isolation, but burst-level performance reveals an energy delivery problem.
The control loop architecture must operate coherently across all three timescales simultaneously. Pulse timing precision is typically in the nanosecond-to-microsecond range. Burst sequencing is in the microsecond-to-millisecond range. Packet control may involve feedback from sensors operating at much longer timescales. These are not naturally harmonious requirements, and the firmware and hardware architecture must be designed with the full hierarchy in mind from the beginning.
The output stage is often an H-bridge, uniquely designed for PFA applications. These amplifiers must switch cleanly and reliably at pulse repetition rates that put real stress on the drive circuitry and gate drive power supplies. Dead time management in the H-bridge is critical: too much dead time distorts the pulse shape; too little risks destructive shoot-through. This challenge is not unique to pulsed field ablation, but the combination of high voltage and fast switching makes it critical to get timing right, and reliable in our experience.
The most common early-stage mistake is designing and validating at the pulse level only, then discovering that burst and packet-level behavior does not match expectations. Pulse-level bench testing is necessary but not sufficient. Build test fixtures and firmware that can exercise the full hierarchy from day one, even if early prototypes cannot hit final voltage specifications.
The second common mistake is underestimating the firmware complexity. The timing hierarchy looks like a straightforward nested loop on paper. In practice, it requires careful attention to interrupt architecture, timer resource allocation, and the interaction between pulse generation, feedback monitoring, and fault handling. Teams with strong hardware backgrounds sometimes underscope the firmware effort. Even for experienced teams, safe firmware control systems are real engineering work that deserves real resources.
The third common mistake is treating the algorithm as fixed once it is initially implemented. Pulsed field ablation therapy protocols are still evolving rapidly. The ability to reconfigure pulse parameters, burst structure, and packet timing without a hardware revision is a significant competitive and practical advantage. Build in configurability early because the cost is low at the architecture stage but high after the fact.
The packet, burst, pulse hierarchy is an elegant solution to the problem of delivering precisely controlled pulsed energy to biological tissue, once designers accumulate experience. This framework gives clinicians and researchers meaningful control at every level of the delivery structure, and gives R&D teams a clear framework for specifying and verifying performance.
A decade of turning this hierarchy into working hardware still teaches us something new on every program. If your team is tackling a PFA generator design, get in touch.
PFA—Pulsed Field Ablation. A therapeutic technique that uses high-voltage electrical pulses to destroy targeted tissue through irreversible electroporation as opposed to thermal energy.
PEF—Pulsed Electric Field. The broader technology category; PFA is a clinical application of PEF. The terms are sometimes used interchangeably in medical device contexts, though PEF is the more general descriptor.
ESU—Electrosurgical Unit. A device that uses high-frequency electrical current to ablate, cut or coagulate tissue through thermal energy. ESUs are the established FDA category PFA generators are often regulated under, despite the different underlying mechanism.
RFG—Radio Frequency Generator. A generator that produces high-frequency alternating current for electrosurgical or ablation applications. RF ablation uses thermal energy to destroy tissue; often cited as the incumbent technology that PFA is positioned to improve upon in selectivity and safety profile.
