| Objective: The purpose of this study was to examine the surface electro- cardiogram features, electrophysiologic characteristics and the mapping and ablation of the tachyarrhythmia originating from the aortic sinus cusp (ASC).Methods: Twenty-four consecutive patients with tachyarrhythmia were referred for the electrophysiologic examination [included 8 patients with focal atrial tachycardia (FAT), 15 patients with frequency premature ventricular contractions or ventricular tachycardia (PVCs/VT) and 1 patient with atrioventricular reentrant tachycardia (AVRT)], the site with the earliest atrial activation (EAA)/the earliest ventricular activation(EVA) was mapped and ablated in both of atrium/ventricle and the aortic sinus cusp. To analyze the surface electrocardiogram features, electrophysiologic characteristics and the results of the ablation of all the tachyarrhythmia mentioned above.Results: Radiofrequency ablation applications were delivered in the non-coronary aortic cusp and terminated FAT in all 8 patients. FATs with cycle length of 284.0～410.0(mean 344.9±50.5)ms were easily reproducibly induced and terminated by atrial pacing in all 8 patients. The surface electrocardiogram demonstrated a shorter P′wave duration (59.0～99.0ms,mean 81.6±12.9ms) during FAT than the P wave duration (100.0～130.0ms,mean113.4±10.4ms)during sinus rhythm(P<0.05).The EAA recorded from the non-coronary aortic cusp preceded the atrial activation at the His bundle by 0～17.0(mean9.9±5.4)ms. FATs were terminated in 2～7 seconds during the first or second radiofrequency in the non-coronary aortic cusp. All 8 patients were free of FAT without antiarrhymic drugs during a follow-up of 2～21months. In 1 patient with PVCs, PVCs were terminated in 4 seconds during the first radiofrequency in the non-coronary aortic cusp where the EVA preceding the QRS complex of PVCs by 18ms was recorded from. The surface electrocardiogram showed a notched"R"pattern in lead I, a"rSr"pattern in lead aVL. In the remaining 14 patients with PVCs/VT, the EVA was recorded from the left coronary cusp. The surface electrocardiogram QRS features of PVCs/VT included an atypical left bundle branch block and right axis deflation, with a low amplitude"rsr""rs""rS"or"QS"pattern in lead I, a high amplitude"R"pattern in lead II, III, aVF, a"R"pattern in V6,precordial R wave transition zone in V1～V3(12 in 14 patients, 85.7%),the R wave duration index≥50% (10 in 14 patients, 71.4%)and R /S wave amplitude index≥30% (11 in 14 patients, 78.6%)determined for leads V1 and V2.The EVA recorded from the left coronary cusp preceded the onset of the QRS complex by 35.0～61.0(mean 45.1±8.0)ms in 9 patients underwent successful catheter ablation and by 17.0～32.0(mean 26.4±5.9)ms in 5 patients underwent failure catheter ablation(P<0.05).A presystolic potential preceding the QRS complex of PVCs/VT with high frequency and low amplitude (P1 potential) was recorded from the ablation target in 9 patients underwent successful catheter ablation. During sinus rhythm, a potential following the QRS complex with high frequency and low amplitude (P2 potential) was recorded from the same ablation target. PVCs/VT were terminated in 3～10 seconds during the 1～3 times radiofrequency in the ablation target and a delay P2 potential after radiofrequency energy was observed in all 9 patients.P1 potential was recorded from the locus that the EVA was mapped in 2 patients out of 5 patients underwent failure catheter ablation. 10 patients underwent successful catheter ablation had no recurrence without antiarrhymic drugs during a follow-up of 4 months～6years. The symptoms were improved in 2 patients underwent failure catheter ablation with Metoprolol and Propranolol oral application respectively.1 patient with AVRT underwent successful catheter ablation in the non-coronary aortic cusp and had no recurrence during a follow-up of 22 months.1 patient had severe angina pectoris and ischemic electrocardiographic changes following ablation of PVCs at the left coronary cusp and recovered after drug therapy. No complications occurred in the remaining 23 patients. Conclusions: Various kinds of tachyarrhythmia may originate from the aortic sinus cusp or its vicinity and they have certain electrocardiographic and electrophysiological characteristics. Radiofrequency catheter ablation from the aortic sinus cusp can be used as a relatively safety and efficiency therapy to cure some of these tachyarrhythmia.
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