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Background —The purpose of this study was to evaluate the safety and efficacy of a temperature-controlled radiofrequency catheter ablation system. Methods and Results —The patient population included 1050 patients who had undergone ablation of atrioventricular nodal reentrant tachycardia (AVNRT), an accessory pathway (AP), or the atrioventricular junction (AVJ). Ablation was successful in 996 patients. The probability of success was highest among patients who had undergone ablation of the AVJ, lowest in patients who had undergone ablation of an AP, and in between for patients who had undergone ablation of AVNRT. A major complication occurred in 32 patients. Four variables predicted ablation success (AVJ, AVNRT, or left free wall AP ablation and an experienced center). Four factors predicted arrhythmia recurrence (right free wall, posteroseptal, septal, and multiple APs). Two variables predicted development of a complication (structural heart disease and the presence of multiple targets), and 3 variables predicted an increased risk of death (heart disease, lower ejection fraction, and AVJ ablation). Conclusions —These findings may serve as a guide to clinicians considering therapeutic options in patients who are candidates for ablation.

The objective of this study was to identify factors that predict fluoroscopy duration and radiation exposure during catheter ablation procedures. The patient population included 859 patients who participated in the Atakr Ablation System clinical trial at 1 of 9 centers (398 male and 461 female patients, aged 36 +/- 21 years). Each patient underwent catheter ablation of an accessory pathway, the atrioventricular junction, or atrioventricular nodal reentrant tachycardia using standard techniques. The duration of fluoroscopy was 53 +/- 50 minutes. Factors identified as independent predictors of fluoroscopy duration included patient age and sex, the success or failure of the ablation procedure, and the institution at which the ablation was performed. Catheter ablation in adults required longer fluoroscopy exposure than it did in children. Men required longer durations of fluoroscopy exposure than did women. The mean estimated "entrance" radiation dose was 1.3 +/- 1.3 Sv. The dose needed to cause radiation skin injury was exceeded during 22% of procedures. The overall mean effective absorbed dose from catheter ablation procedures was 0.025 Sv for female patients and 0.017 Sv for male patients. This degree of radiation exposure would result in an estimated 1,400 excess fatal malignancies in female patients and 2,600 excess fatal malignancies in male patients per 1 million patients.

Previous studies have shown that single-chamber sensor-driven pacing improves exercise tolerance for patients with chronotropic incompetence. However, long-term single-chamber pacing has a number of inherent problems that limit its usefulness. Although sensor-driven dual-chamber pacing largely obviates the problems inherent with single-chamber sensor-driven pacing, the physiologic benefit of dual-chamber sensor-driven pacing has not yet been demonstrated. Accordingly, the purpose of this study was to compare exercise-induced cardiac output for patients with chronotropic incompetence, after programming their pacemakers to either a simulated sensor-driven single or simulated dual-chamber mode. Cardiac output was measured noninvasively at rest and peak exercise using standard Doppler-derived measurements, obtained in a blinded fashion. At rest the Doppler-derived resting VVI and DDD cardiac outputs were 4.49 +/- 0.3 L/min and 4.68 +/- 0.3 L/min, respectively. At peak exercise, the DDD cardiac output was 5.07 +/- 0.5 L/min, whereas the simulated activity VVI and DDD cardiac outputs were 6.33 +/- 0.6 L/min and 7.41 +/- 0.70 L/min, respectively. Analysis of variance showed that there was an overall significant difference in cardiac output from rest to peak exercise (p less than 0.001). However, only the simulated activity DDD cardiac output was significantly different from its respective control value (p less than 0.05). Thus this study shows for the first time that the addition of rate responsiveness to dual-chamber pacing results in a significant improvement in cardiac output for patients with chronotropic incompetence.

Neurally mediated syncope is being recognized with increasing frequency in young adults and more recently in children.1–4 Most children undergoing formal orthostatic testing exhibit a vasodepressor or mixed response with a gradual onset of hypotension, often preceded by sinus tachycardia, followed by secondary bradycardia and syncope.1–3 Few of these patients have a dominant cardioinhibitory response exhibiting sudden onset of bradycardia and syncope without prior hypotension or tachycardia.1 Syncopal episodes in this group (unusual in the pediatric experience) may present more risk owing to the rapid onset of syncope, prolonged asystole and seizure activity often exhibited.4 This study reports on the incidence, clinical features, management and outcome of infants and children presenting with dominant Cardioinhibitory syncope.

Radiation exposure is an important risk during ablation (abl) procedures. To determine the relationship between the target arrhythmia, fluoroscopy time (fluoro), and the success of abl procedures we analyzed data from 450 patients in the Atakr multicenter clinical study(217 F, 233 M, 38 ± 21 yrs). Target arrhythmias included AVNRT (154 pts), the AV junction (54 pts, AVJ), and 241 accessory pathway (APs). Results Similar success was achieved during abl of APs, AVNRT. and the AVJ (93%, 98%, and 94% respectively, p g 0.1). In contrast, fluoro time was greater during abl of APs than during abl of AVNRT or the AVJ (62 ± 48, versus 31 ± 29 a 36 ± 24 min, p l 0.05). Cumulative success of catheter abl of APs rose rapidly during the first 90 min of fluoro exposure and then plateaued. In contrast. cumulative success during abl of the AVJ and AVNRT plateaued after 40 and 70 min. Concl Similar success can be achieved during abl of APs, AVNRT. and the AVJ, but greater fluoro is needed during abl of APs. Resultant radiation risk should be considered when determining an appropriate termination point. Download : Download high-res image (85KB) Download : Download full-size image

Sumn2ary.-The purpose of this srudy was to investigate whether the age, race, and sex of psychological examiners (Es) would affect the objective personality scale performance of Negro and Caucasian psychiatric patients. Eight groups of 10 Ss each were administered the Taylor MAS, the MMPI X scale, and the MMPI L scale by one of eight Es. Half the Ss were Negro and half were Caucasian. Half the Es were Negro and half were Caucasian; half the Es were male and half were female; and half the Es were older (M.,, = 36) and half were younger (Ma,. = 23). Analysis of che data indicated that, depending on Ss' race, significant performance differences in Ss' objective test responses were related to E's age, sex, and race. However, the inreraction between Es' age and Ss' race was the most consistently demonstrated effect in this study. Comprehensive reviews by Masling (1960), Kintz, Delprato, Mettee, Persons, and Shappe ( 1965 ), and Rosenthal ( 1966) present considerable evidence supporting the position that Ss' responses to psychological tests are influenced by varying characteristics of the psychological E. The sex (Rosenthal, 1966, 1967), race (Dreger & Miller, 1968), and age (Rosenthal, 1966) of E have been found to influence Ss' responses. There is evidence that college students' responses to highly structured, objective tests, such as the Taylor (1953) Manifest Anxiety Scale (MAS) and the MMF'I ( 1951) K and L scales may be significantly influenced by E characteristics (Walker, Davis, & Firetto, 1968; Davis, 1968). This srudy investigated the effect of Es' age, race, and sex on the objective test performance of Negro and Caucasian psychiatric patients.