[A 66-year old female patient with tachycardia and syncope].

A 66-year old female patient suffered from paroxysmal tachycardias, palpitations, dizziness and once a short period of unconsciousness. The surface ECG showed preexcitation, and the clinical diagnosis of WPW syndrome was established. The electrophysiological study revealed the rare occurrence of an epicardial posteroseptal accessory pathway. Retrograde venous angiography of the coronary sinus showed a coronary sinus diverticulum. Ablation of the accessory pathway in the neck of the coronary sinus diverticulum was successful. Epicardial accessory pathways in a coronary sinus diverticulum are rare. However, successful ablation of accessory pathways at this site is safely possible.