Objective To investigate the characteristics of supraventricular tachycardia affiliated with left concealed atrioventrieular accessory pathway (AP) with rapid rate dependent ventriculoatrial conduction and the experience of electrophysiological (EP) study and radiofrequency catheter ablation (RFCA) in these cases.

Methods 8 patients, 5 male, 3 female, aged from 24 to 62 years, who all had symptoms of paroxysmal palpitation and whose ECG recorded at the onset of tachycardia all manifested as narrow QRS complex, underwent electrophysiologic study and RFCA by the routine method, which including the properties of ventriculoatrial conduction while pacing (s₁s₁) were performed in right ventricular apex (RVA) and left ventricle, mapping AP and RFCA.

Result 8 cases were all left concealed atrioventrieular AP. In all patients that special kind of atrioventrieular AP with rapid rate dependent ventriculoatrial conduction were demonstrated to exist by EP study and the atrio-ventrieular reentrant tachycardia with the earliest atrial activated site located were induced. When pacing with slow rate in RVA, there were no ventriculoatrial conduction by AP; when pacing with fast rate, there were internal ventriculoatrial conduction by AP and when pacing with faster rate, there were 1:1 ventriculoatrial conduction by AP. Ablation were identified during rapid rate ventricular pacing and a successful ablation was attained in every patient.

Conclusion Rapid rate dependent conduction of left concealed atrioventricular accessory pathway is existent and it can also induce atrioventrieular reentrant tachycardia. We should pay attention to it avoiding missed diagnosis.