Beat-to-beat T-wave amplitude variability in the long QT syndrome.

AIMS: Long QT syndrome (LQTS) is a primary electrical disease characterized by QT prolongation and increased repolarization dispersion leading to T-wave amplitude beat-to-beat changes. We aimed to quantify beat-to-beat T-wave amplitude variability from ambulatory Holter recordings in genotyped LQTS patients. METHODS AND RESULTS: Seventy genotyped LQTS patients (mean age 23 +/- 15 years, 42 males, 50% LQT1, 39% LQT2, and 11% LQT3) and 70 normal matched control subjects underwent a 24-h digital Holter recording. Using the Tvar software (Ela Medical, Sorin group), the beat-to-beat variance of the T-wave amplitude (TAV in microV) [corrected] was assessed on 50-ms consecutive clusters during three 1-h periods: one with around average diurnal heart rate (Day Fast), one nocturnal period (Night), and one diurnal period with around average nocturnal heart rate (Day Slow). TAV was increased in LQTS patients during the two diurnal periods but not at night (during the Day Fast period, mean TAV was 34 +/- 20 microV [corrected] in LQTS patients vs. 27 +/- 10 microV [corrected] in controls, P < 0.05). This effect depended on the genotype. In LQT1, TAV was larger when compared with controls for both Day Fast and Slow periods, but in LQT2 only Day Fast shows higher TAV. Oppositely, in LQT3 the TAV was higher than in the control group during the Day slow period (mean TAV = 34 +/- 20 vs. 25 +/- 8 microV [corrected] in controls, P < 0.05). CONCLUSION: In genotyped LQTS patients beat-to-beat T-wave amplitude variability was increased when compared with control subjects. That pattern was modulated by circadian influences in a gene-dependent manner.

Rapid and low-cost method to prove the nature of no documented tachycardia in children and teenagers without pre-excitation syndrome.

Aims Symptoms in children are often difficult to interpret. The purpose of this study was to report the results of transoesophageal electrophysiological study (EPS) performed in children complaining of sudden onset tachycardia with normal non-invasive studies. Methods and results Eighty-two children and teenagers (mean age 15 +/- 3 years) presented with suspected but no documented paroxysmal supraventricular tachycardia (SVT). ECG was normal. Non-invasive studies were negative; 23 children had syncope with tachycardias. They underwent transoesophageal EPS in our out-patient clinic. The mean duration of transoesophageal EPS was 11 +/- 5 min. Electrophysiological study was negative in 25 children. AV nodal re-entrant tachycardia could be induced in 37 children, 11 of them associated with syncope. Wolff-Parkinson-White syndrome (WPW) was diagnosed in five children in which atrioventricular re-entrant tachycardia was inducible. Atrioventricular re-entrant tachycardia due to a concealed AP was induced in 14 children. Verapamil-sensitive ventricular tachycardia was induced in one patient. Factors associated with tachycardia inducibility were an older age (15.5 +/- 2 vs. 14 +/- 4 years) (P < 0.05) and the absence of syncope (81 vs. 52%) (P < 0.05). During a mean follow-up of 3 +/- 1 year, no patient with negative EPS developed documented tachycardia. In 17 children with inducible SVT, radiofrequency ablation of the re-entrant circuit was subsequently performed. Conclusion Transoesophageal EPS is a fast method for proving the nature of paroxysmal tachycardia in children and teenagers presenting with normal ECG and for demonstrating WPW syndrome not visible on standard ECG. The negative predictive value of transoesophageal EPS for the diagnosis of SVT was 100%.

Are the results of electrophysiological study different in patients with a pre-excitation syndrome, with and without syncope?

AIMS: Syncope in Wolff-Parkinson-White (WPW) syndrome may reveal an arrhythmic event or is not WPW syndrome related. The aim of the study is to evaluate the results of electrophysiological study in WPW syndrome according to the presence or not of syncope and the possible causes of syncope. METHODS AND RESULTS: Among 518 consecutive patients with diagnosis of WPW syndrome, 71 patients, mean age 34.5 +/- 17, presented syncope. Transoesophageal electrophysiological study in control state and after isoproterenol infusion was performed in the out-patient clinic. Atrioventricular re-entrant tachycardia (AVRT) was more frequently induced than in asymptomatic patients (n = 38, 53.5%, P < 0.01), less frequently than in those with tachycardia; atrial fibrillation (AF) and/or antidromic tachycardia (ATD) was induced in 28 patients (39%) more frequently (P < 0.05) than in asymptomatic patients or those with tachycardia. The incidence of high-risk form [rapid conduction over accessory pathway (AP) and AF or ATD induction] was higher in syncope group (n = 18, 25%, P < 0.001) than in asymptomatic subjects (8%) or those with tachycardias (7.5%). Maximal rate conducted over AP was similar in patients with and without syncope, and higher in patients with spontaneous AF, but without syncope. Results were not age-related. CONCLUSION: Tachycardia inducibility was higher in patients with syncope than in the asymptomatic group. The incidence of malignant WPW syndrome was higher in patients with syncope than in asymptomatic or symptomatic population, but the maximal rate conducted over AP was not higher and another mechanism could be also implicated in the mechanism of syncope.