Missing diagnosis of preexcitation syndrome on ECG: Clinical and electrophysiological significance

Electrocardiographic criteria of preexcitation syndrome are sometimes not visible on ECG in sinus rhythm (SR). The purpose of the study was to evaluate the significance of unapparent preexcitation syndrome in SR, when overt conduction through accessory pathway (AP) was noted at atrial pacing.MethodsAnterograde conduction through atrioventricular AP was identified at electrophysiological study (EPS) in 712 patients, studied for tachycardia (n = 316), syncope (n = 89) or life-threatening arrhythmia (n = 55) or asymptomatic preexcitation syndrome (n = 252). ECG in SR at the time of EPS was analysed.Results78 patients (11%) (group I) had a normal ECG in SR and anterograde conduction over AP at atrial pacing; 634 (group II) had overt preexcitation in SR. Group I was as frequently asymptomatic (35%) as group II (35%), had as frequently tachycardias, syncope or life-threatening arrhythmia as group II (43, 5, 2% vs 43, 13, 8%). AP was more frequently left lateral in group I (57%) than in group II (36%)(p < 0.001). AV re-entrant tachycardia, atrial fibrillation (AF), antidromic tachycardia were induced as frequently in group I (54, 18, 10%) as in group II (54, 27, 7%). Malignant forms (induced AF with RR intervals between preexcited beats < 250 ms in control state or < 200 ms after isoproterenol) were as frequent in group I (11.5%) as II (14%).ConclusionsThe frequency of unapparent preexcitation syndrome represents 11% of our population with anterograde conduction through an AP and could be underestimated. The risk to have a malignant form is as high as in patients with overt preexcitation syndrome in SR.

Research highlights► 11% of patients with conduction through accessory pathway had unapparent preexcitation syndrome. ► It is recommended repeating the ECG recordings in subjects who practice sports. ► Do not hesitate to indicate electrophysiological study in a patient who complains of tachycardia.