Association between radiographic Wallerian degeneration and neuropathological changes post childhood stroke

Aim Wallerian degeneration is a radiological finding thought to reflect corticospinal tract degeneration. This finding on magnetic resonance imaging (MRI) is routinely used as a predictor of poor prognosis in childhood stroke. However, its validity has never been established. Our objective was to correlate Wallerian degeneration seen on MRI with histopathology. Method We searched the databases of the Department of Pathology and Children’s Stroke registry at the Hospital for Sick Children, Toronto for autopsy specimens exhibiting focal infarcts from children born at term who underwent MRI after a stroke. The specimens were examined for Wallerian degeneration and then correlated with the pre‐mortem MRI findings. Results Seven children (four females, three males) with a median age of 11 years (1–17y) at the time of stroke met the inclusion criteria for this study. Of the seven children included in the study with ischaemic or haemorrhagic infarcts, six had concordant Wallerian degeneration findings on both MRI and post‐mortem histopathological examination. The median time between stroke and death was 20 days (3–1825d). Interpretation Our results show for the first time that the radiographic finding of Wallerian degeneration is a valid biomarker of corticospinal tract degeneration in children who have had ischaemic or haemorrhagic stroke.     

Broad Applicability of Ultrarapid Train Stimulation as an Efficient Alternative to Conventional Programmed Electrical Stimulation

FISHER, J.D., et al.: Broad Applicability of Ultrarapid Train Stimulation as an Efficient Alternative to Conventional Programmed Electrical Stimulation. Background and study objective:Conventional programmed electrical stimulation (PES) is useful for establishing inducibility or noninducibility of clinical ventricular arrhythmias (VA), but is complex and time-consuming. This study compared a standard PES protocol with ultrarapid train stimulation (UTS) in a broad range of patients with and without a history of ventricular arrhythmias or structural heart disease. Methods: Patients prospectively underwent electrophysiologic testing with both UTS and conventional PES protocols in a randomized, crossover design. Results: The results were concordant in 79% of 150 matched pairs of comparisons in 104 patients (NS). There were no differences related to underlying heart disease or arrhythmia, or antiarrhythmic treatment. Induction of nonclinical arrhythmias with the two methods was similar   (P = 0.524)   . Inhibition phenomena were minor except in some patients receiving amiodarone. Fewer drive-extrastimuli sequences and less time were needed to complete the trains protocol   (P < 0.0001)   . Conclusions: In cases where the main intent is to induce ventricular arrhythmias, UTS yields results that are similar to those of conventional PES protocols in a shorter length of time. (PACE 2003; 26[Pt. II]:518–523)     

Alternation of Atrioventricular Nodal Conduction Time During Atrioventricular Reentrant Tachycardia:

AV Nodal Conduction Time Alternation. Introduction: Alternation of atrial cycle length and AV nodal conduction time (NCT) is often observed during AV reentrant tachycardia. Both AV nodal dual pathway and rate-dependent function have been postulated to be involved in this phenomenon. This study was designed to determine the respective role of these two mechanisms in the alternation observed in an in vitro model of orthodromic AV reentrant tachycardia. Methods and Results: The tachycardia was produced by detecting each His-bundle activation and stimulating the atrium after a retrograde delay, thereby simulating retrograde pathway conduction, in six isolated rabbit heart preparations. After a 5-minute stabilization period at a fast rate, the retrograde delay was decremented by 2 msec every minute until nodal blocks occurred. We observed a sequential alternation of the cycle length and NCT in four preparations in the short retrograde delay range. The magnitude of the alternation gradually increased as the retrograde delay was decreased and reached 4.6 ± 0.5 msec during 1:1 conduction. The alternation increased further just prior to termination of the tachycardia by an AV nodal block. None of the preparations showed discontinuous AV nodal recovery curves. Moreover, an electrode positioned over the endocardial surface of the node showed that the alternation developed distally to the nodal inputs, which are believed to constitute a major component of dual pathways. A mathematical model predicted the alternation from known characteristics of rate-dependent nodal functional properties. Conclusions: NCT and cycle length alternation can arise during orthodromic AV reentrant tachycardia when the retrograde delay is sufficiently short. The characteristics of the alternation, presence of continuous recovery curves, intranodal location of the alternation, and mathematical modeling suggest that the alternation is predictahle from the known functional properties of the AV node without postulating dual pathway physiology.     

The Relationship Between Electrogram Cycle Length and Dominant Frequency in Patients with Persistent Atrial Fibrillation

Introduction: Sites of complex fractionated atrial electrograms (CFAE) with a short mean cycle length (MCL) and sites with a high dominant frequency (DF) have been advocated as targets for ablation in patients with persistent atrial fibrillation (AF). However, there are little data on the relationship between theses 2 markers. This study assessed the relationship between the DF and electrogram MCL after pulmonary vein (PV) isolation in patients with persistent AF. Methods and Results: A total of 44 patients with persistent AF were studied. Four‐second bipolar electrograms were obtained with a multielectrode mapping catheter at regions throughout the left atrium after isolation of the pulmonary veins, with analysis of the MCL and DF at each site. The DF was defined as the largest frequency peak within a 2.5‐ to 16‐Hz spectral profile generated with fast Fourier transformation of the electrogram. A total of 9,262 electrograms from the 44 patients were analyzed. The average MCL and DF post‐PV isolation were 135 ± 24 ms and 6.1 ± 0.6 Hz, respectively. There was a statistically significant but weak correlation between the MCL and DF (r = 0.21, P < 0.001). Additionally, analysis of this relationship within each patient did not demonstrate a strong correlation (range of r values per patient =?0.18 to 0.47). Conclusions: There is a poor correlation between the electrogram MCL and DF in patients with persistent AF. Ablation strategies targeting DF and those targeting CFAE are therefore unlikely to direct ablation toward similar left atrial sites. Comparative studies are necessary to determine the effectiveness of each strategy in guiding catheter ablation of persistent AF.     

Cerebral sinus venous thrombosis in Swiss children

Aim To describe the characteristics of paediatric cerebral sinus venous thrombosis (CSVT) in Switzerland. Method Data on clinical features, neuroimaging, risk factors, and treatment were collected for all children in Switzerland younger than 16 years of age who had CSVT between January 2000 and December 2008. A follow‐up examination and a cognitive assessment were performed (mean follow‐up period 26mo). Differences between neonates and children (patients older than 28d) were assessed and predictors of outcome were determined. Results Twenty‐one neonates (14 males, seven females; mean age 9d, SD 8d) and 44 children (30 males, 14 females; mean age 8y 7mo, SD 4y 5mo) were reported. The incidence of paediatric CSVT in Switzerland was 0.558 per 100 000 per year. In neonates, the deep venous system was more often involved and parenchymal injuries were more common. The strongest predictor of poor outcome was neonatal age (odds ratio 17.8, 95% confidence interval 0.847–372.353). Most children showed global cognitive abilities within the normal range, but impairments in single cognitive subdomains were frequent. Interpretation Paediatric CSVT is rare. Its outcome is poor in neonates. Most children have good neurological outcomes, but some patients have individual neuropsychological impairments.     

Initial Experience With a Multielectrode Catheter Equipped With the Single‐Axis Sensor Technology for High‐Density Electroanatomical Mapping in a Swine Model

Utility of Single‐Axis Sensor Technology in High‐Density Electroanatomical Mapping. Introduction: Magnetic‐based electroanatomical mapping systems are widely used during catheter ablation. Currently, the size of the sensor incorporated in the catheter to allow its localization is large, prohibiting the placement of more than one sensor on any single catheter. As a result, multielectrode catheters cannot be tracked by the magnetic‐based mapping systems. Single‐axis sensors (SAS) are new generation sensors that are significantly smaller in size. The small size of these new sensors allows the placement of more than one sensor on each catheter, allowing the tracking of multielectrode catheters. The objective of this study is to test the feasibility of creating high‐density magnetic electroanatomical maps using a new generation multielectrode catheter equipped with the SAS technology. Methods and Results: Anatomical reconstruction of cardiac chambers and the aorta, together with activation mapping of the right atrium during both sinus rhythm and pacing‐induced premature atrial contractions (PACs), were performed in 5 swine using both a conventional mapping catheter and the novel multielectrode catheter equipped with SAS. The multielectrode mapping provided a detailed definition of cardiac anatomy while requiring shorter acquisition times. In addition, mapping of PACs origin was significantly faster using the multielectrode catheter. Conclusion: The novel multielectrode catheter equipped with the SAS technology can be used in combination with magnetic electroanatomical mapping systems to generate high‐density anatomical reconstructions and activation maps. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1403‐1407, December 2010)     

Impact of Tricuspid Regurgitation and Prior Coronary Bypass Surgery on the Geometry of the Coronary Sinus: A Rotational Coronary Angiography Study

Coronary Venous Geometry in Patients Undergoing CRT . Introduction: The coronary sinus (CS) is often distorted in patients with advanced cardiomyopathy, making CS cannulation difficult. The objective of this study was to examine the impact of the underlying cardiac pathology on the variability of the CS anatomy, using rotational coronary venous angiography (RCVA). Methods and Results: Seventy‐nine patients undergoing RCVA for cardiac resynchronization therapy (CRT) were evaluated: age 63 ± 15 years, 43% with prior coronary artery bypass grafting (CABG). Aspects of the CS anatomy which could impact cannulation were examined: the CS ostial angle, the posterior displacement of the CS away from the atrioventricular groove, a measure of CS curvature, and the presence of stenoses and aneurysmal dilatations. The CS ostial angle was variable (65–151°, mean 119 ± 19°, <90° in 8 patients) and decreased significantly (P = 0.0022) with increasing severity of tricuspid regurgitation (TR), reaching 94 ± 18° in patients with severe TR. The posterior displacement of the CS was significantly more accentuated in patients with prior CABG when compared with the patients without CABG (7.1 ± 3.7 vs 4.5 ± 2.8 mm; P = 0.0246). The decrease in luminal diameter at the CS–great cardiac vein (GCV) junction was 2.0 ± 1.0 mm, being more pronounced in patients with prior CABG versus nonCABG (26 vs 20%; P = 0.042). Stenoses and aneurysmal dilatations of the CS–GCV were encountered in 4 (5%) and 6 (8%) of patients, respectively, all of them with prior CABG, representing 12% and 18% of the CABG group. Conclusion: The CS anatomy in patients undergoing CRT is variable, and is impacted by the severity of the underlying TR and history of a prior CABG. (J Cardiovasc Electrophysiol, Vol. 21, pp. 436–440, April 2010)     

Optimal Timing of Implantable Cardioverter‐Defibrillator Implantation After Myocardial Infarction: A Decision Analysis

ICD Implant Timing . Background: The optimal timing of implantable cardioverter defibrillator (ICD) placement for the primary prevention of sudden cardiac death after myocardial infarction (MI) remains unknown. Methods and Results: We developed a Markov model to investigate the optimal timing of ICD implantation after MI (no ICD, ICD at 60 days, 6 months, and 1 year) in patients who meet current guidelines. Estimates of arrhythmic death (baseline risk 6%, range 1–20% per year), nonarrhythmic death, and ICD efficacy were based upon MADIT‐II and other contemporary post‐MI clinical trials. We used both deterministic and stochastic modeling processes in our analysis. After 10 years follow‐up, the baseline probability of survival was higher in those treated with ICD implantation versus not (42% vs 30%, P < 0.001). Survival was highest with ICD implantation at 60 days versus 6 months versus 1 year: 42.4%, 42.3%, and 42.0% (P = 0.0028). ICD implantation at 60 days provided a mean incremental survival of 0.28 months and 0.84 months per patient (compared with implantation at 6 months and 1 year). In sensitivity analyses, patients’ competing risk for nonarrhythmic death was the primary determinant of benefit from ICD implantation. Overall, ICD implantation at 60 days resulted in the greatest life expectancy over a wide range of plausible nonarrhythmic and arrhythmic death rates. Conclusions: The benefits of early ICD implantation are modest when compared with delayed implantation at 6 months/1 year. Our results suggest that making sure a patient receives an ICD, when appropriate, may be more important than the timing of the implantation procedure. (J Cardiovasc Electrophysiol, Vol. pp. 791‐798, July 2010)