Neuroimaging in childhood arterial ischaemic stroke: evaluation of imaging modalities and aetiologies

Aim The aim of this study was to describe neuroimaging patterns associated with arterial ischaemic stroke (AIS) in childhood and to differentiate them according to stroke aetiology. Method Clinical and neuroimaging (acute and follow‐up) findings were analysed prospectively in 79 children (48 males, 31 females) aged 2 months to 15 years 8 months (median 5y 3mo) at the time of stroke by the Swiss Neuropaediatric Stroke Registry from 2000 to 2006. Results Stroke was confirmed in the acute period in 36 out of 41 children who underwent computed tomography, in 53 of 57 who underwent T2‐weighted magnetic resonance imaging (MRI) and in all 48 children who underwent diffusion‐weighted MRI. AIS occurred in the anterior cerebral artery (ACA) in 63 participants and in all cases was associated with lesions of the middle cerebral artery (MCA). The lesion was cortical–subcortical in 30 out of 63 children, cortical in 25 out of 63, and subcortical in 8 of 63 children. Among participants with AIS in the posterior circulation territory, the stroke was cortical–subcortical in 8 out of 16, cortical in 5 of 16, and thalamic in 3 out of 16 children. Interpretation AIS mainly involves the anterior circulation territory, with both the ACA and the MCA being affected. The classification of Ganesan is an appropriate population‐based classification for our Swiss cohort, but the neuroimaging pattern alone is insufficient to determine the aetiology of stroke in a paediatric population. The results show a poor correlation between lesion pattern and aetiology.     

Effects of Polarity on Defibrillation Thresholds Using a Biphasic Waveform in a Hot Can Electrode System

The polarity of a monophasic and biphasic shocks have been reported to influence DFTs in some studies. The purpose of this study was to evaluate the effect of the first phase polarity on the DFTofa biphasic shock utilizing a nonthoracotomy "hot can" electrode configuration which had a 90-μF capacitance. We tested the hypothesis that anodal first phase was more effective than cathodal ones for defibrillation using biphasic shocks in ten anesthetized pigs weighing 38.9 ± 3.9 kg. The lead system consisted of a right ventricular catheter electrode with a surface area of 2.7 cm² and a left pectoral "hot can" electrode with 92.9 cm² surface area. DFT was determined using a repeated "down-up" technique. A shock was tested 10 seconds after initiation of ventricular fibrillation. The mean delivered energy at DFT was 11.2 ± 1.7 J when using the right ventricular apex electrode as the cathode and 11.3 ± 1.2 J (P = NS) when using it as the anode. The peak voltage at DFT was also not significantly different (529.0 ± 41.3 and 531.8 ± 28.6 V, respectively). We concluded that the first phase polarity of a biphasic shock used with a nonthoracotomy "hot can" electrode configuration did not affect DFT.     

A Minimal Model of the Single Capacitor Biphasic Defibrillation Waveform

A quantita tive model of the single capacitor biphasic defibrillation wave form is proposed. The primary hypothesis of this model is that the first phase leaves a residual charge on the membranes of the unsynchronized cells, which can then reinitiate fibrillation. The second phase diminishes this charge, reducing the potential for refibrillation. To suppress this potential refibrillation, a monophasic shock must be strong enoagh to synchronize a critical mass of nearly 100% of the myocytes. Since the biphasic waveform performs this protection function by removing the residual charge (with its second phase), its first phase may be of a lower strength than a monophasic shock of equivalent performance. A quantitative model was developed to calculate the residual membrane voltage, V_m, assuming a capacitive membrane being alternately charged and discharged by the first and second phases, respectively. It was further assumed that the amplitude of the first phase would be predicted by a minimum value plus a term proportional to V_m². The model was evaluated on the pooled data of three relevant published studies comparing biphasic waveforms. The model explained 79% of the variance in the first phase amplitude and predicted optimal durations for various defibrillator capacitances and electrode resistances. Assuming a first phase of opti mal duration, the optimal second phase duration appears to be about 2.5 msec for all capacitances and resistances now seen clinically. Conclusion: The effectiveness of the single capacitor biphasic waveform may be explained by the second phase "burping" of the deleterious residual charge of the first phase that, in turn, reduces the synchronization requirement and the amplitude requirements of the first phase.     

A Minimal Model of the Monophasic Defibrillation Pulse

A minimal model of the defibrillation capability of a monophasic capacitive discharge pulse is derived from the Weiss-Lapicque strength duration model. The model suggests that present, empirically derived values of pulse durations and tilts are close to optimum for presently used values of capacitors and electrode resistances. The model suggests that neither the tilt nor fixed duration specification is universally superior to the other for dealing with electrode resistance changes. A tilt specification would appear to best handle resistance decreases while a fixed duration specification would best handle resistance increases. The model was used to study the effect of capacitance changes. It appears that the optimum tilt and pulse duration vary with the capacitance value. The model further suggests that decreasing the capacitance from presently used values may lower defibrillation thresholds.     

Transobturatory tension-free composite sling for urethral support in patients with stress urinary incontinence: Favorable experience after 1 year follow up

OBJECTIVE: Symptomatic, anatomic and urodynamic results of a composite transobturatory tension-free sling with an absorbable middle part, in patients with stress urinary incontinence (SUI), were studied. METHODS: A prospective study in 40 women with SUI was performed. Symptoms, urodynamics and anatomical improvements were evaluated separately. Surgery was performed with the transobturatory approach. RESULTS: All patients had both clinically and urodynamically confirmed SUI. Clinical outcome was favorable in 36/40 (90%) patients, after 1 year. Operation improved the position of the bladder neck (2.8 cm and 1.4 cm below the pubic bone, respectively) and significantly decreased mobility of the bladder neck during abdominal straining (3.3 cm and 1.7 cm, respectively). Both symptoms and quality of life were significantly improved 1 month after the surgery. Postoperative maximum flow was lower than the preoperative one but with borderline significance (25.8 and 23.7 mL/s; P = 0.05). Pressure flow study showed unobstructed voiding both preoperatively and postoperatively. Detrusor pressure at the maximum flow was increased (20, 4 and 22, 8 cmH(2)O, respectively) but not significantly. CONCLUSION: Our results confirmed a high objective cure rate, improvement of symptoms and quality of life, and at the same time, corrected position of the bladder neck and unobstructed voiding.