Inability of the Signal-Averaged Electrocardiogram to Determine Risk of Arrhythmia Recurrence in Patients with Implantable Cardioverter Defibrillators

Signal-averaged electrocardiography has been used to identify patients at risk for arrhythmic death after myocardial infarction. Since patients with implantable cardioverter defibrillators (ICDs) are at high risk for arrhythmic events, they should also be expected to have a high incidence of abnormal signal-averaged electrocardiograms (SAECGs). However, whether the SAECG can discriminate patients who will have arrhythmia recurrence and receive appropriate ICD shocks from those who will have no recurrence and no shocks is unknown. This study examines the usefulness of the SAECG to separate appropriate users from non-users of the ICD. Fifty patients with ICDs participated in this study. Those who received a shock preceded by symptoms, a shock without preceding symptoms but with electrocardiographic documentation of ventricular fibrillation or ventricular tachycardia, or a shock while asleep were classified as ICD users. All other patients were classified as nonusers. The SAECG was classified as normal if the QRS duration on the standard electrocardiogram was less than or equal to 110 msec and if the total filtered QRS duration was less than 120 msec, the root-mean square voltage of the terminal 40 msec was greater than 25 muV, and the terminal low amplitude signal duration measured less than 38 msec. The SAECG was classified as abnormal if the QRS duration on the standard electrocardiogram was less than or equal to 110 msec and any one of these three criteria were outside the "normal range." The SAECG was classified as indeterminate if the QRS duration on the standard 12-lead electrocardiogram was greater than 110 msec. For the entire group of 50 patients, 8 (16%), 12 (24%), and 30 (60%) had normal, abnormal, and indeterminate SAECGs, respectively. Of the 22 ICD users, 1 (5%), 5 (23%), and 16 (73%) patients had normal, abnormal, and indeterminate SAECGs, respectively. Of the 28 ICD nonusers, 7 (25%), 7 (25%), and 14 (50%) patients had normal, abnormal, and indeterminate SAECGs, respectively. ICD users had lower left ventricular ejection fractions (P = 0.0002), a higher incidence of ventricular tachycardia (P = 0.04), prior exposure to a greater number of antiarrhythmic drugs (P = 0.04), and a lower likelihood for survival (P = 0.02) compared to the ICD nonusers. There was no statistically significant difference between the ICD users and nonusers as stratified by SAECG classification regardless of whether or not the interminate studies were included or excluded from the analysis.(ABSTRACT TRUNCATED AT 400 WORDS)     

Phenytoin in the Treatment of Inducible Ventricular Tachycardia: Results of Electrophysiologic Testing and Long-Term FoUow-Up

Phenytoin treatment of inducible ventricular tachyarrhythmias was assessed by serial electrophysiologic studies (EPS) in 64 patients with spontaneous ventricular tachycardia, cardiac arrest, or symptoms compatible with a ventricular tachyarrhythmia. Coronary artery disease was the primary cardiac disease in 75% of the patients. All subjects had either inducible ventricular tachycardia (greater than or equal to 10 repetitive beats) or ventricular fibrillation at electrophysiologic study. Phenytoin was administered intravenously in 38 studies and orally in 31 studies. The mean serum phenytoin level was 19.5 +/- 4.7 mcg/ml. Only seven patients (11%) had a negative electrophysiologic study (less than or equal to 10 repetitive beats) after the administration of phenytoin and were classified as phenytoin responders (group I). The remaining 54 patients (89%) were classified as nonresponders (group II). For the nonresponders, phenytoin increased the cycle length of identical monomorphic ventricular tachycardias from a mean of 31 ms to a mean of 327 ms (p less than 0.001). For the four patients tested receiving both intravenous and oral phenytoin, the intravenous response always predicted the oral response. For the seven patients in whom electrophysiologic study indicated phenytoin efficacy, two are alive and arrhythmia-event free, two had sudden death when the regimen was changed (one case, quinidine added; one case, subtherapeutic serum level), and three died from nonarrhythmic causes. For the 10 patients treated empirically with phenytoin, either alone (seven patients) or in combination with another antiarrhythmic agent (three patients), four died secondary to an arrhythmic event.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vitro antibody-mediated macrophage activity on Breinlia macropi microfilariae. I. Adherence and cytotoxicity

Intense adherence accompanied by cytotoxicity, which initially occurred at 4 h of interaction was observed when the microfilariae of Breinlia macropi were introduced to cultures of quokka peritoneal macrophages previously sensitized in 20% immune serum. No significant difference in the adherence or cytotoxic effects was observed among macrophages from normal, microfilaraemic and amicrofilaraemic quokkas. However, the serum component mediating these effects was found only in microfilaraemic and seropositive amicrofilaraemic quokkas. This mediator was heat-labile and its mediation of the adherence and cytotoxic effects was independent of complement. Because of its apparent dissociation from IgG and its heat lability, the possibility that the mediator resides in the previously-described reaginic antibody of the quokkas was discussed.     

Case Studies with the Experts: Management Decisions in Atrial Fibrillation

Atrial fibrillation (AF) is the most common outpatient arrhythmia. The recent ACC/AHA/ESC guidelines outline a variety of approaches to the management of AF, but their implementation into clinical practice requires multi-faceted patient evaluations and assessments for optimizing patient care. Using a case-based approach, issues such as rate versus rhythm control, anticoagulation, cardioversion, pharmacological and catheter ablation for maintenance of sinus rhythm, and the pathophysiology of AF are discussed. These data were originally presented at a satellite symposium titled Case Studies with the Experts: Management Decisions in AF , held on May 10, 2007, during the annual Heart Rhythm Society meeting.     

Spontaneous Accelerated Junctional Rhythm: An Unusual but Useful Observation Prior to Radiofrequency Catheter Ablation for Atrioventricular Node Reentrant Tachycardia in Young Patients

Between May 1990 and March 1995, 5 of 29 young patients (ages 4.2–25 years; median 14.1 years) undergoing RF ablation for atrioventricular node reentrant tachycardia (AVNRT) presented with spontaneous accelerated junctional rhythm (AJR) (CL = 500–750 ms), compared to 0 of 58 age matched controls undergoing RF ablation for a concealed AV accessory pathway (P = 0.004). In 3 of the 5 patients with AVNRT and AJR, junctional beats served as a trigger for reentry. During attempted slow pathway modification in the five patients with AVNRT and AJR, AVNRT continued to be inducible until the AJR was entirely eliminated or dramatically slowed. These 5 patients are tachycardia-free in followup (median 15 months; range 6–31 months) with only 1 of the 5 patients continuing to experience episodic AJR at rates slower than observed preablation. Episodic spontaneous AJR is statistically associated with AVNRT in young patients and can serve as a trigger for reentry. Successful modification of slow pathway conduction may be predicted by the elimination of AJR or its modulation to slower rates, suggesting that the rhythm is secondary to enhanced automaticity arising near or within the slow pathway.     

Transferrin and the Absorption of Iron

A loop isolated in situ has been used to study iron absorption in the dog.An infusion of iron salt into the artery supplying the isolated loop fails tostop the absorption of iron from the lumen of the gut. Iron absorption appearsto be independent of the relative saturation of iron-binding protein.

Submitted on July 9, 1962 Accepted on July 26, 1962     

European guidelines for the certification of professionals in sleep medicine: report of the task force of the European Sleep Research Society

In recent years, sleep medicine has evolved into a full-grown discipline, featuring a multidisciplinary approach to diagnosis and treatment of patients with sleep disorders. Sleep medicine cuts across the boundaries of different conventional disciplines and is therefore open to medical and non-medical professionals with different specialty backgrounds. The aim of the current paper is to introduce a qualification for those professionals whose main occupation is to practice sleep medicine in the setting of a sleep medicine centre. The drafting of guidelines dealing with requirements for such qualification was entrusted to a task force by the European Sleep Research Society. The guidelines are the result of a progressive consensus procedure in which standards were defined for education, training, and evaluation. The final step along this pathway is a theoretical and practical examination, providing proof of proficiency in the field of sleep medicine. This paper describes the object of specific competences, the scope of sleep medicine, and the qualification procedures that pertain to three professional categories: medical specialists, non-medical professionals with a university master degree (such as psychologists and biologists), and nurses and technologists. Indices of preceding practical experience and theoretical knowledge are presented in Appendices 1 and 2 . These guidelines are a European standard. They may be adapted in the future according to new scientific insights. National certification programs that comply with these guidelines may be subject to homologation by the ESRS.     

Free testosterone levels in umbilical‐cord blood predict infant head circumference in females

Aim Fetal androgens influence fetal growth as well as postnatal neurocognitive ability. However, to our knowledge, no published study has prospectively examined the impact of early‐life androgens on infant brain growth. We report the association between circulating fetal androgen levels, measured from umbilical‐cord blood at birth, and a proxy measure of brain growth: head circumference. Method Participants were 82 unselected female infants from a large representative birth cohort (mean gestational age 39.4wks, SD 1.7). Umbilical‐cord blood was obtained at birth and analysed for androgen concentrations (total testosterone, androstenedione, dehyrdroepiandrosterone, and its sulphated metabolite). Head circumference and two other measures of growth – weight (mean 3311.4g, SD 461.3) and length – were measured within 3 days of birth and again at approximately 1 year of age (mean age 13.1mo, SD 1.1). Results Multivariate linear regressions found an inverse association between levels of free testosterone and growth in head circumference (correlation=?.24), even when adjusting for sociodemographic/obstetric covariates and head size at birth. Growth in weight and length could not be predicted by free testosterone concentration. Interpretation This is the first report of an association between prenatal androgen levels and postnatal growth in head circumference. These findings suggest that early‐life androgens may impact brain development during infancy.