During the generation of radiofrequency (RF) lesions in the ventricular myocardium, the maintenance of adequate electrode-tissue contact is critically important. In this study, lesion dimensions and temperature and impedance changes were evaluated while controlling electrode-tissue contact levels (-5, 0, +1, and +3 mm) and power levels (10, 20, and 30 W). This data was used to assess the ability of impedance and temperature monitoring to provide useful information about the quality of electrode-tissue contact. The results show that as the electrode-tissue contact increases, so does the amount of temperature rise. With the electrode floating in blood (-5 contact), the average maximum temperature increase with 20 and 30 W was only 7 +/- 1 and 11 +/- 2 degrees C, respectively. At 20 and 30 W the temperature plateaued shortly after the initiation of power application. With good electrode-tissue contact (+1 mm or +3 mm), the temperature increase within the first 10 seconds was significantly greater than the temperature increase from baseline with poor contact (0 mm or -5 mm) and reached a maximum of 60 +/- 1 degrees C after 60 seconds of power application. As the electrode-tissue contact increased, so did the rate and level of impedance decrease. However, the rate of impedance decrease was slower compared to the rate of temperature rise. With the electrode floating in blood, the maximum impedance decreases with 20 and 30 W were 6 +/- 6 omega and 9 +/- 5 omega, respectively. The impedances plateaued after a few seconds of power application. With the electrode in good contact, the maximum impedance decreases with 20 and 30 W were 25 +/- 2 omega and 20 +/- 6 omega, respectively. In these cases the rate of the impedance decrease plateaued after 40 seconds of power application. The increase in lesion diameter and depth correlate well with decreasing impedance and increasing temperature. However, lesion depth appears to correlate better with impedance than temperature. We conclude that, since the electrode-tissue contact is not known prior to the application of power to the endocardium, in the absence of a temperature control system, the power should initially be set at a low level. The power should be increased slowly over 20-30 seconds, and then maintained at its final level for at least 90 seconds to allow for maximal lesion depth maturation. The power level should be lowered if the impedance drop exceeds 15 omega.
Various types of atrial electrograms are present at different locations during atrial fibrillation. The atrial electrogram characteristics of atrial fibrillation at a specific location are related to the atrial effective refractory period, with short effective refractory periods associated with organized atrial electrograms and long effective refractory periods associated with disorganized electrograms.
Our results demonstrate the efficacy and tolerability of CLB, TOP and LAM in children with difficult to treat epilepsies and a good response in CLB and LAM, and a reasonable response in TOP beyond 12 months.
In this study, ADS synchronized to NQRS complexes appeared to be safe regardless of the preceding RR interval. In the presence of LBBB or RBBB, RR intervals preceding the ADS of >345 ms at baseline and >380 ms in the presence of procainamide would have been required to avoid VF. Alternatively, ADS delivered 50 ms after the onset of the RV electrogram appeared to be safe in all circumstances regardless of the preceding RR interval.
Adding an additional shocking electrode may reduce ADER when compared with the RA (anode) to CS (cathode) configuration. This concept could be incorporated into future implantable atrial defibrillators or used for refractory patients undergoing temporary transvenous cardioversion.
A variety of microwave applicators were designed, fabricated and tested for catheter applications: I-radiators, U-radiators, O-radiators, forward helical coil radiator, reverse helical coil, double coil radiator, loaded monopole radiator, leaky coaxial radiator and tee radiators. The comparative and relative radiation characteristics of these applicators were tested in a saline bath and tissues. Most radiators designed produced larger lesions than have been described previously.
Gabapentin (GAB) is a newer second-line antiepileptic drug (AED) used in children. This is a multi-centre retrospective observational study of the efficacy, tolerability and retention rate in 105 children, aged 0-17.5 years (mean 10.1) over a 14 year period. The median age of epilepsy onset was 2.5 years (range 0-14.6). 72% started GAB as at least the 3rd AED, with 43% having been withdrawn from at least 2 AEDs. 77% had focal and 52% symptomatic epilepsies. The maintenance doses for GAB ranged 6.0-87.3 mg/kg/day (mean 43.7). The study comprised 157 person-treatment years for GAB. GAB was well tolerated with 55% remaining on treatment beyond 1 year. No serious adverse events were reported whilst on GAB, but 39% reported possibly and probably related adverse events. Seizure improvement (<50% seizure frequency compared to baseline) at more than 12 months of treatment, was reported in 35% of patients starting GAB, including 6% who remained seizure free. The results demonstrated the efficacy and tolerability of GAB in children with difficult to treat epilepsies, and a good response to treatment beyond 12 months, in both focal and generalised epilepsies.
AimsTo systematically observe the use of four second-line antiepileptic drugs (AEDs) in children and the retention, perceived effectiveness, tolerability and safety over 12 months follow-up.MethodsAll children starting clobazam (CLB), gabapentin (GAB), lamotrigine (LAM) or topiramate (TOP) in a defined period and hospital clinic population were ascertained retrospectively from the hospital pharmacy and paediatric neurology secretaries' databases and clinic letters. A standard data sheet was used to record background data and outcomes at more than 2, 6 and 12 months follow-up. This was a registered clinical audit and service evaluation, and was undertaken as part of medical student's BMedSci courses. Simple statistical analysis was undertaken in SPSS on an intention to treat basis.Results147 children aged 0.1–17 years have been studied to date: CLB (49), GAB (21), LAM (41), TOP (36), and notes on a further 100 are being interrogated. Epilepsies were evenly split between focal and generalised; apart from GAB (75% on GAB had focal epilepsies). Most were symptomatic or probably symptomatic with a median age of onset 2 years. The AEDs were used after a mean of two other AEDs had been withdrawn (range 1–10).Preliminary analysis showed no major differences in perceived effectiveness between the AEDs, although there was a fall-off of efficacy for all from 2 months to 12 months follow-up: CLB 46–30%, GAB 53–43%, LAM 38–29%, TOP 33–22%. Probably, AED-related adverse events were found in 50% at some stage, although no serious adverse events were recorded. Overall, 54% were still taking the AED after 12 months.ConclusionsThis is a simple way of auditing the effects of AED treatment in an unselected population with difficult to treat childhood epilepsies and complements data from randomised controlled trials which are usually in more selected populations with shorter follow-up. More data will be available by March 2010, and clinically significant differences in perceived effectiveness might then be confirmed or excluded, and subset analyses undertaken. Comparison with other second-line AEDs levetiracetam, zonisamide, lacosamide and others used in this population will be helpful.
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