Clinical case nr. 3

Asymptomatic ventricular pre-excitation

The typical electrocardiographic features of pre-excitation are a short PR-interval associated with a slurred upstroke of the QRS-complex. This is called a delta wave. It is caused by premature activation of the ventricles by the impulse that travels through the accessory pathway. Wolff–Parkinson–White syndrome (WPW) is defined as recurring episodes of arrhythmias in a patient with ventricular pre-excitation, caused by an accessory pathway with antegrade conduction (in this case, the Kent bundle).

Management of pre-excitation

Since the risk of sudden cardiac death in asymptomatic pre-excitation is very low (0.15-0.20%), it is unclear which patients should undergo risk stratification and treatment. Risk stratification relies on an electrophysiologic study to determine the risk of atrial arrhythmias (e.g. the inducibility of AV-nodal re-entry tachycardia or atrial fibrillation) and the properties of the accessory pathway (factors suggesting an increased risk include an R-R interval less than 240 ms at baseline or less than 220 ms during isoproterenol infusion, a refractory period less than 250ms at baseline, multiple or a septal location of the accessory pathway). Patients with accessory pathways should also have an echocardiogram to look for an associated Ebstein's anomaly or hypertrophic cardiomyopathy. Radiofrequency catheter ablation should not be performed in all individuals with WPW syndrome because there are inherent risk involved in the procedure (especially if the accessory pathway is localized anteroseptally) that may not outweigh the benefits of the intervention. Anti-arrhythmic drugs have not been shown to be helpful in this condition.

During intensive exercise, catecholamines can decrease the refractory period of the accessory pathway and provoke tachyarrhythmias. Moreover, evidence suggests there might be an increased risk of atrial fibrillation with excessive levels of exercise. Competitive sports can be considered on an individual basis in the absence of risk factors on cardiac electrophysiology testing and if there is no risk when the patient loses consciousness (which might be the case in pilots, for example).

References

• Heidbüchel H, Panhuyzen-Goedkoop N, Corrado D, et al (2006). "Recommendations for participation in leisure-time physical activity and competitive sports in patients with arrhythmias and potentially arrhythmogenic conditions Part I: Supraventricular arrhythmias and pacemakers". Eur J Cardiovasc Prev Rehabil 13 (4): 475–84. doi:10.1097/01.hjr.0000216543.54066.72. PMID 16874135. 

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