Case Report
A 20-year-old woman with VVS suffered recurrent cardioinhibitory syncope seven months after successful CNA (see Fig 1), the details of which are published elsewhere (7). Evaluation of her ILR data at the time of recurrence revealed both HRV and average ventricular rate gradually trending back toward baseline pre-CNA levels, after having initially dropped off following CNA (see Fig 2). On her subsequent clinic visit, a thorough discussion was held with the patient and her mother, during which time she expressed a strong desire to re-attempt CNA.
She presented to the EP suite again in a fasting state, and the same preparations were made. She was administered atropine 0.5 mg; however, her HR increased from 51 beats per minute (BPM) to only 60 BPM. After ruling out administration errors and waiting approximately 20 minutes, a second dose of atropine 0.5 mg was administered, and again no significant HR response was observed. These findings were in stark contrast to those of her index procedure, when a single dose of atropine 0.4 mg increased her HR by 81% (7). A transseptal puncture was performed in the usual fashion. Fractionation mapping was then undertaken, resulting in the same annotated fractionation areas as in the first CNA (see Fig 3A). High-frequency stimulation (HFS) was applied to each of the ganglionated plexi (GP); however, this time, slow junctional responses could not be reliably elicited from any GP sites, except for a single junctional beat following HFS from the posterior RA GP. Ablation at both the posterior RA GP and along the anterior RSPV acutely increased the HR by approximately 10 BPM, suggestive of further vagal denervation (see Fig 3B). Of note, the anterior RSPV lesions covered a broader area than in the index CNA. RF ablation was applied at each of the GP sites, due to sparse new diagnostic data in support of any given site, and with cognizance that this was a repeat procedure (see Fig 3C). Atropine was again administered at the end of ablation, and the patient’s HR paradoxically dropped from 78 BPM to 40 BPM in response. Isoproterenol 10 mcg was given as a bolus, and HR increased to >100 BPM. A 12-lead ECG obtained in the post-procedural recovery area recorded normal sinus rhythm, HR 65 BPM, with all measured intervals within normal range.
On follow up 2 months after her repeat CNA, she reported feeling quite well, with no further syncope events. Her ILR again demonstrated an abrupt decrease in HRV, although its ensuing ascent was steeper than the pattern following her initial procedure (see Fig 2B). Further, there was not a sustained increase in her average ventricular rate, unlike her spike following her first CNA (7).