Effects of resting vagal tone on accessory atrioventricular connections.
Why the study?
Does atropine administration alter the electrophysiological properties of accessory AV connections in patients with Wolff-Parkinson-White syndrome?
Population
20 patients with Wolff-Parkinson-White syndrome (13 in the primary group, 7 in the secondary group)
Comparison
Atropine administration vs Baseline electrophysiological measurements prior…
Design
Case_series
Authors
Discussion
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Implication
Supports vagal modulation of accessory pathways in WPW; hypothesis-generating from case report and should not change practice.
Key Points
- To determine the electrophysiological effects of resting vagal tone on accessory atrioventricular connections in patients with Wolff-Parkinson-White syndrome.
- Administered intravenous atropine (0.04 mg/kg) to 13 patients with Wolff-Parkinson-White syndrome to evaluate changes in accessory connection conduction and refractory periods.
- Administered propranolol (0.2 mg/kg) prior to atropine in a separate cohort of 7 patients to assess whether vagal effects depend on baseline sympathetic tone.
- In 13 patients, atropine shortened anterograde block cycle length from 305 ± 51 to 279 ± 54 msec (p < 0.001), retrograde block cycle length from 288 ± 57 to 251 ± 50 msec (p < 0.001), and anterograde effective refractory period from 295 ± 45 to 265 ± 47 msec (p < 0.001).
- During atrial fibrillation, mean ventricular cycle length decreased from 434 ± 88 to 352 ± 56 msec (p < 0.001) and shortest preexcited RR interval decreased from 302 ± 56 to 256 ± 43 msec (p < 0.01).
- In 7 patients pretreated with propranolol, atropine induced similar alterations in accessory connection conduction, demonstrating that vagal depressant effects do not require background sympathetic activity.
Structured PICO
Does atropine administration alter the electrophysiological properties of accessory AV connections in patients with Wolff-Parkinson-White syndrome?
P
Population
20 patients with Wolff-Parkinson-White syndrome (13 in the primary group, 7 in the secondary group)
I
Intervention
Atropine (0.04 mg/kg) administration (with or without prior propranolol 0.2 mg/kg)
C
Comparator
Baseline electrophysiological measurements prior to drug administration
O
Outcome
Electrophysiological properties of the accessory AV connection, including anterograde and retrograde block cycle lengths and effective refractory periodsurrogate
Resting vagal tone exerts a direct depressant effect on accessory AV connections in patients with Wolff-Parkinson-White syndrome, independent of background sympathetic activity.
Cite This Study
Morady et al. (1990) studied this question.