Swallow syncope associated with complete atrioventricular block in an adolescent.

We describe a 16-year-old female with a history of swallowing-induced syncope. The physical examination, ECG, echocardiography, barium swallow test, and thyroid function tests were within normal limits. The ambulatory ECG revealed intermittent complete atrioventricular block only associated with swallowing. There was also intermittent first-degree atrioventricular block not related to eating. An electrophysiologic study was performed during the implantation of a single-chamber transvenous ventricular pacemaker. There was mild atrioventricular nodal conduction disturbance with a His-ventricular interval of 70 msec and Wenckebach cycle length of 420 msec. During 1 year follow-up, the patient remained asymptomatic.

Idiopathic monomorphic ventricular tachycardia originating from the left aortic sinus cusp in children: endocardial mapping and radiofrequency catheter ablation.

BACKGROUND: Idiopathic repetitive monomorphic ventricular tachycardia with an inferior axis and left bundle branch block pattern typically originates from the superior right ventricular outflow tract. When indicated, radiofrequency catheter ablation is usually safe and effective. However, a left ventricular origin has been described recently in adult patients in whom ablation attempts in the right ventricular outflow tract were unsuccessful. Experience in pediatric patients is limited. PATIENTS AND METHODS: Since 1998, 13 young patients suffering from symptomatic ventricular tachycardia episodes with an inferior axis and left bundle branch block pattern underwent an electrophysiological study and radiofrequency catheter ablation. In 2 patients, age 13 and 15 years, no endocardial local electrograms preceding the surface ECG QRS complex could be recorded within the right ventricular outflow tract during ventricular ectopy. Detailed mapping within the left ventricular outflow tract and in the aortic root revealed local electrograms 25 and 53 ms earlier than the QRS complex and a 11/12 and 12/12 lead match during pacing inferior and anterior to the ostium of the left main coronary artery in the left aortic sinus cusp. Earliest activation was recorded 10 and 12 mm away from the coronary artery ostium identified angiographically. In each of the patients, one single radiofrequency current application (60 degrees C, 30 W, duration 30 and 60 s, respectively) resulted in complete cessation of ventricular ectopy. Subsequent selective injection into the left coronary artery did not reveal any abnormalities. During follow-up (2 and 34 months) off any antiarrhythmic drugs, both of the patients are in continuous normal sinus rhythm. CONCLUSION: In young patients with symptomatic idiopathic ventricular tachycardia originating from the left aortic sinus cusp, radiofrequency catheter ablation was safe and effective.

P wave signal-averaged electrocardiogram as a new marker for atrial tachyarrhythmias in postoperative Fontan patients.

OBJECTIVES: This study was undertaken to determine the potential role of P wave signal-averaged electrocardiogram (PSAECG) for risk assessment of atrial tachyarrhythmias (ATs) in patients after Fontan operation. BACKGROUND: Onset of atrial flutter/fibrillation (AFF) in patients who have undergone Fontan operation for univentricular hearts constitutes an unfavorable clinical event associated with a high risk of cardiovascular complications. There is no data available on PSAECG in postoperative Fontan patients to predict potential susceptibility to ATs. METHODS: Twenty-four post-Fontan patients and 15 age-matched healthy subjects were prospectively studied with PSAECG, and the following measurements were made: filtered P wave duration (FPWD), P wave vector integrals (PINTs), root-mean-square voltage for the initial 30 ms (RMSi30), and duration of persistent amplitude signals <4 microV from the beginning of the P wave (Di4). RESULTS: The FPWDs were significantly longer in the study group patients with ATs when compared with the study group patients without ATs (p<0.01) and compared with the controls (p < 0.001). An FPWD cut point of 135 ms resulted in a sensitivity of 71% and a specificity of 81% in differentiating patients with ATs from patients without ATs among the postoperative Fontan patients. The PINT was significantly greater in Fontan patients with AFF and also without AFF when compared with controls (p<0.01, p<0.05, respectively). The RMSi30 and the Di4 were not significantly different between study and control groups. CONCLUSIONS: Signal-averaged P wave duration is significantly prolonged in postoperative Fontan patients. A prolonged signal-averaged P wave duration may be an effective noninvasive marker to predict risk of development of ATs in this patient group.

Cardiac rhythm abnormalities during intravenous immunoglobulin G infusion for treatment of thrombocytopenia.

PURPOSE: Several side effects of intravenous immunoglobulin G (IVIG) therapy are known, but it has never been reported to be associated with cardiac rhythm abnormalities other than sinus tachycardia. PATIENTS AND METHODS: We describe the development of cardiac dysrhythmias during intravenous immunoglobulin G infusion in two children with thrombocytopenia. One of the patients had a history of supraventricular tachycardia, and the other had evidence suggestive of preexisting long QT syndrome. CONCLUSION: Cardiac rhythm abnormalities may be exacerbated in individuals with preexisting cardiac problems by IVIG infusion, and such patients should be monitored closely during IVIG administration.