Asymmetric Biphasic Pulses Reshape Atrial Fibrillation Ablation in Landmark Chinese Trial

Atrial fibrillation, the world’s most common sustained heart-rhythm disorder, has just received one of its most intriguing technological updates yet. A team of Chinese researchers has reported the results of a prospective, multicenter clinical trial of a novel asymmetric biphasic pulsed field ablation (PFA) system, publishing their findings in Frontiers in Cardiovascular Medicine. The study enrolled 120 patients with drug-refractory paroxysmal atrial fibrillation across ten Chinese centers and followed them for a full year after a single ablation procedure. The results offer both reassurance and a fresh engineering perspective on a technology that has rapidly become the hottest topic in cardiac electrophysiology.

Pulsed field ablation works on the principle of irreversible electroporation: extremely short, high-voltage electric pulses punch nanoscale pores into cell membranes, killing cardiomyocytes while largely sparing neighboring structures. Because different tissue types have different thresholds for irreversible injury, PFA is inherently tissue-selective. That selectivity is what has made it so attractive compared with thermal techniques such as radiofrequency and cryoablation, which can inadvertently damage the esophagus, the phrenic nerve, or the coronary arteries that lie close to the pulmonary veins—the trigger sites for most paroxysmal atrial fibrillation.

Early PFA platforms relied on monophasic pulses, which are simple to generate and highly efficient at electroporating cells, but they came with a well-documented set of problems. Monophasic stimulation provoked violent skeletal muscle contractions, required deep anesthesia, and drove unwanted electrochemical reactions at the electrodes, including polarization and gas formation. Biphasic waveforms—pairs of pulses with opposite polarity—were introduced to balance the delivered electrical charge, dramatically reducing muscle stimulation and electrochemical byproducts. Today, essentially every major commercial platform, from FARAPULSE to VARIPULSE to PulseSelect, uses some form of biphasic delivery.

But symmetric biphasic designs carry their own subtle biophysical trade-offs. When the second, opposite-polarity phase immediately follows the first, it can partially cancel the transmembrane potential that the first phase built up—a phenomenon known as the charge-cancellation effect. Compensating for that inefficiency requires higher electric field strengths, and pushing more energy through dense, high-frequency pulse bursts can generate unintended Joule heating, microbubble formation, and acute hemolysis. Those complications are not theoretical: silent cerebral lesions and hemolysis-related kidney injury have both emerged as safety concerns in the broader PFA literature.

The Chinese team, led by researchers at Tianjin Medical University and collaborating hospitals, took a different route. Their system delivers each pulse as an asymmetric biphasic waveform—a 7-microsecond positive phase followed by a 3-microsecond negative phase, separated by a 5-microsecond interval—at an amplitude of 1,000 volts. The catheter itself is a 10.5 French device with six adjustable splines, each carrying a single electrode. During each pulse, three electrodes act as anodes and three as cathodes. The catheter can be partially expanded into a basket shape to advance into a pulmonary vein, then fully deployed into a flower configuration with a maximum diameter of 32 millimeters at the vein’s ostium, maximizing tissue contact for ablation.

The trial, registered as ChiCTR2200062157, enrolled patients between January 2022 and December 2024. All had symptomatic paroxysmal atrial fibrillation that had failed or could not be tolerated on at least one class I or class III antiarrhythmic drug. Fifteen patients withdrew before the procedure, leaving 105 who underwent ablation and completed the prespecified 12-month follow-up. The cohort had a mean age of 63.7 years, was 60 percent male, and carried a mean CHA2DS2-VASc stroke-risk score of 1.54. Procedures were performed under general anesthesia or conscious sedation with uninterrupted oral anticoagulation and heparin to maintain an activated clotting time of at least 300 seconds.

The procedural results were striking. All 420 targeted pulmonary veins were acutely isolated—a 100 percent acute success rate—and no vein reconnected during the mandatory 20-minute waiting period after ablation. The mean ablation time, from the first PFA application to the last, was just under 219 seconds, and the mean total procedure time was about 102 minutes. Post-ablation voltage mapping, performed in roughly half the patients at the operator’s discretion, confirmed complete isolation at the pulmonary vein antra with no evidence of unintentional lesion formation elsewhere in the left atrium.

At 12 months, the Kaplan–Meier estimate of freedom from atrial arrhythmia recurrence—atrial fibrillation, flutter, or tachycardia lasting at least 30 seconds on protocol-specified monitoring—was 69.5 percent, with a 95 percent confidence interval of 60.1 to 77.5 percent. That figure sits comfortably within the range reported for other PFA technologies. The SINGLE SHOT CHAMPION trial reported 62.9 percent one-year freedom from recurrence, the PULSED AF Pivotal Trial reported 66.2 percent, and the VOLT-AF IDE study reported 81.1 percent. Importantly, no patient in the Chinese trial underwent repeat ablation during the 90-day blanking period, whereas several comparator studies permitted repeat procedures without counting them as endpoint failures—a difference the authors flag when urging caution about direct cross-study comparisons.

On the safety front, the results were equally notable. Not a single case of pulmonary vein stenosis, phrenic nerve injury, atrioesophageal fistula, stroke, cardiac tamponade, or acute kidney injury was recorded across the entire 12-month follow-up. The primary safety endpoint—a predefined serious adverse event—occurred in just one patient (0.95 percent), who experienced a transient coronary vasospasm on postoperative day three that resolved completely after intracoronary vasodilator administration. That patient had a pre-existing high-grade atherosclerotic coronary lesion, and while the authors acknowledge that a contributory role of the PFA procedure cannot be entirely excluded, the episode underscores a known pattern: ST-segment elevation during or after PFA should prompt urgent coronary angiography and nitroglycerin, and prophylactic nitrates may be worth considering when ablating near coronary arteries.

Two secondary safety signals deserve attention. Silent cerebral lesions, detected on brain MRI 12 to 48 hours after ablation, appeared in two patients (1.9 percent)—a rate lower than the 6.7 to 12.9 percent reported in some other PFA studies. The lesions disappeared completely on follow-up imaging at three and six months. The authors attribute the low rate partly to their waveform choice, noting that bench tests showed biphasic waveforms generate fewer microbubbles than monophasic ones, and that asymmetric biphasic pulses achieve better ablation depth than symmetric ones. Electrode geometry was also deliberately designed to avoid sharp edges and current-concentration hotspots that promote arcing and bubble formation. Meanwhile, laboratory hemolysis was common—87.6 percent of patients met the prespecified definition, with significant drops in haptoglobin and rises in lactate dehydrogenase and free plasma hemoglobin—but creatinine levels were unchanged and no patient developed acute kidney injury. The authors credit their asymmetric waveform, the basket-type catheter with single-sided electrodes that keeps current focused on tissue rather than blood, and a standardized peri-procedural saline hydration protocol. The study has limitations worth noting: it was single-arm with no comparator, lacked continuous implanted rhythm monitoring, enrolled a relatively modest sample, and excluded patients with significant renal impairment, so the hemolysis findings may not generalize to that population. Still, as a real-world, multicenter demonstration that a re-engineered pulse waveform and catheter geometry can deliver complete pulmonary vein isolation with an exceptionally clean safety record, the trial adds meaningful weight to the argument that the next generation of PFA will be defined as much by waveform physics as by catheter design.

Subject of Research: Clinical evaluation of an asymmetric biphasic pulsed field ablation system for paroxysmal atrial fibrillation

Article Title: Asymmetric biphasic pulsed field ablation of paroxysmal atrial fibrillation: clinical assessment

Article References: Xu, X., Li, Y., Lu, F., Li, H., & Cai, H. (2026). Asymmetric biphasic pulsed field ablation of paroxysmal atrial fibrillation: clinical assessment. Frontiers in Cardiovascular Medicine, 13, Article 1945178. https://doi.org/10.3389/fcvm.2026.1945178

Image Credits: AI Generated

DOI: 10.3389/fcvm.2026.1945178

Keywords: pulsed field ablation, atrial fibrillation, pulmonary vein isolation, irreversible electroporation, biphasic waveform, silent cerebral lesions, hemolysis, coronary vasospasm, cardiac electrophysiology, catheter ablation, clinical trial, Tianjin Medical University