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Published on: May 26, 2010
The electrophysiological characteristics of accessory pathways in pediatric patients with intermittent preexcitation
Douglas Y Mah1, Elizabeth D Sherwin, Mark E Alexander
1Department of Cardiology, Boston Children's Hospital, Boston, Massachusetts; the Department of Pediatrics, Harvard Medical School, Boston, Massachusetts.
Insights
Intermittent preexcitation (IPX) pathways, though often considered lower risk, can still present with rapidly conducted atrial fibrillation. The presence of IPX on an electrocardiogram does not exclude the possibility of high-risk accessory pathways.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Diagnostics
Background:
- Accessory pathways (APs) with intermittent preexcitation (IPX) are generally perceived as lower risk.
- However, clinical reports indicate that some IPX patients may experience rapidly conducted atrial fibrillation.
- This study investigates the risk stratification of IPX in preexcitation syndromes.
Purpose of the Study:
- To compare the electrophysiological characteristics of accessory pathways (APs) in patients with intermittent preexcitation (IPX) versus persistent preexcitation (PPX).
- To determine if baseline electrocardiogram findings of IPX can reliably rule out potentially high-risk APs.
Main Methods:
- Retrospective analysis of 328 patients with preexcitation undergoing electrophysiological study (EPS).
- IPX defined by loss of delta wave on ECG before EPS; compared with persistent preexcitation (PPX) and IPX on exercise testing (IPX-ET).
- Excluded patients with congenital heart disease or prior ablations.
Main Results:
- Of 328 patients, 41 (12.5%) had IPX. IPX and PPX groups were similar in age and AP location.
- IPX patients had longer median refractory periods (340 ms vs. 310 ms, P=0.001) than PPX patients.
- Incidence of APs with refractory periods ≤250 ms was similar between IPX and PPX (10% vs. 12%, P=1.0) and between IPX and IPX-ET groups.
Conclusions:
- Patients with IPX demonstrated longer AP refractory periods compared to PPX.
- The incidence of accessory pathways with short refractory periods (≤250 ms) did not significantly differ between IPX and PPX groups.
- Intermittent preexcitation on a baseline ECG should not preclude the identification of potentially high-risk accessory pathways.
Background:
Accessory pathways (APs) with intermittent preexcitation (IPX) are thought to be of lower risk, but there are reports of IPX patients presenting with rapidly conducted atrial fibrillation.
Methods:
Retrospective study performed on patients with preexcitation who underwent an electro-physiological study (EPS). IPX was defined as loss of the delta wave on electrocardiogram prior to EPS. Patients with IPX were compared with those with persistent preexcitation (PPX) or suppression of the delta wave on exercise test (IPX-ET). Congenital heart disease and prior ablations were excluded.
Results:
Of 328 patients with preexcitation, 41 (12.5%) had IPX. Patients with IPX or PPX were similar in age (12.9 years vs 13.0 years, P = 0.8) and AP location (left-sided 54% vs 50%, P = 0.7; septal 32% vs 35%, P = 0.4). Testing on isoproterenol was performed in 17 (41%) IPX and 41 (14%) PPX patients. Although IPX patients had a longer median refractory period compared to PPX patients (340 ms vs 310 ms, P = 0.001), the incidence of APs with refractory periods ≤250 ms was similar (10% vs 12%, P = 1.0). Exercise tests were performed on 208 patients and 24 (12%) had IPX-ET. Compared with IPX patients, IPX-ET had similar median AP refractory periods (320 ms, P = 0.4) and incidence of APs with refractory periods ≤250 ms (13%, P = 1.0).
Conclusion:
Patients with IPX had longer AP refractory periods than those with PPX, but the incidence of pathways with refractory periods ≤250 ms was not significantly different. The finding of IPX on a baseline electrocardiogram does not rule out potentially high-risk pathways.
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