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).