Disappearance of local ventricular components during extrastimulus pacing after ultra-low-temperature cryoablation for ventricular tachycardia: a case report.

Background: Ultra-low-temperature cryoablation (ULTC) enables the creation of deep and potentially transmural myocardial lesions and is increasingly used for ventricular tachycardia (VT) substrate modification. However, the chronic electrophysiological properties of myocardium following extreme cryothermal injury remain incompletely understood. Case summary: A 66-year-old man with dilated cardiomyopathy and a cardiac resynchronization therapy defibrillator presented with recurrent sustained VT 15 months after ULTC of the left ventricular outflow tract. During repeat ablation, high-density mapping revealed sharp local ventricular electrograms within the prior ablation region. Programmed ventricular stimulation from the right ventricular outflow tract reproducibly induced disappearance of these sharp local components during extrastimulus pacing, while the surface QRS complex remained preserved, indicating preserved global ventricular activation. The phenomenon was consistently observed across different pacing protocols. Radiofrequency ablation targeting this region resulted in elimination of the sharp local electrograms, whereas dull far-field signals persisted. After ablation, VT was no longer inducible, and the patient remained free from recurrence at 3-month follow-up. Discussion: This case demonstrates a reproducible disappearance of near-field ventricular electrograms during extrastimulus pacing in myocardium previously treated with ULTC. The findings suggest localized refractoriness or source-sink mismatch within partially injured myocardium, rather than conventional slow conduction. These observations provide novel insight into the chronic electrophysiological effects that may occur after ULTC and may have implications for substrate assessment during repeat VT ablation.