Evaluation of epicardial microwave lesions in the pig model using an electroanatomic mapping system

Therapeutic effect of methylprednisolone combined with high frequency electrotherapy on acute spinal cord injury in rats

Acute spinal cord injury (SCI) has a high rate of disability and mortality. Although secondary SCI results in local tissue hypoxia and the release of inflammatory mediators, it is both controllable and reversible. Therefore, timely rehabilitation treatment is beneficial for the partial recovery of patients with SCI. The present study aimed to investigate the use of methylprednisolone combined with high-frequency electrotherapy as a method of rehabilitation treatment in rats with SCI. The rat SCI model was prepared using the modified Allen's method with the animals randomly divided into the following 4 groups (n=10 for each group): SCI; methylprednisolone (300 mg/kg); high-frequency electrotherapy; and combination treatment with electrotherapy combined with methylprednisolone (300 mg/kg). The Basso, Beattie and Bresnahan (BBB) score, somatosensory evoked potential (SEP) and motor evoked potential (MEP) were used to assess spinal function. Brain-derived neurotrophic factor (BDNF) and NF-κB expression levels were detected using reverse transcription-quantitative PCR and western blotting. Tumor necrosis factor (TNF)-α and IL-2 expression levels were determined by ELISA, and caspase 3 activity was also assessed. In all treatment groups, BDNF mRNA and protein expression levels were significantly increased, whilst those of NF-κB were reduced. Additionally, an elevated BBB score, improved SEPs and MEPs, inhibited caspase 3 activity and downregulated TNF-α and IL-2 expression levels were observed, compared with the SCI group (P<0.05). However, the combination group exhibited more significant effects on SCI. In conclusion, methylprednisolone combined with high frequency electrotherapy may improve the symptoms of SCI by increasing the expression level of BDNF, reducing that of NF-κB, and suppressing the secretion of inflammatory factors.

Biophysical parameters during radiofrequency catheter ablation of scar-mediated ventricular tachycardia: epicardial and endocardial applications via manual and magnetic navigation

BACKGROUND

There is a paucity of data on biophysical parameters during radiofrequency ablation of scar-mediated ventricular tachycardia (VT).

METHODS AND RESULTS

Data were collected from consecutive patients undergoing VT ablation with open-irrigation. Complete data were available for 372 lesions in 21 patients. The frequency of biophysical parameter changes were: >10Ω reduction (80%), bipolar EGM reduction (69%), while loss of capture was uncommon (32%). Unipolar injury current was seen in 72% of radiofrequency applications. Both EGM reduction and impedance drop were seen in 57% and a change in all 3 parameters was seen in only 20% of lesions. Late potentials were eliminated in 33%, reduced/modified in 56%, and remained after ablation in 11%. Epicardial lesions exhibited an impedance drop (90% vs. 76%, P = 0.002) and loss of capture (46% vs. 27%, P < 0.001) more frequently than endocardial lesions. Lesions delivered manually exhibited a >10Ω impedance drop (83% vs. 71%, P = 0.02) and an EGM reduction (71% vs. 40%, P < 0.001) more frequently than lesions applied using magnetic navigation, although loss of capture, elimination of LPs, and a change in all 3 parameters were similarly observed.

CONCLUSIONS

VT ablation is inefficient as the majority of radiofrequency lesions do not achieve more than one targeted biophysical parameter. Only one-third of RF applications targeted at LPs result in complete elimination. Epicardial ablation within scar may be more effective than endocardial lesions, and lesions applied manually may be more effective than lesions applied using magnetic navigation. New technologies directed at identifying and optimizing ablation effectiveness in scar are clinically warranted.

Epicardial Ablation on the Beating Heart: Limited Efficacy of a Novel, Cooled Radiofrequency Ablation Device

OBJECTIVE: To perform a minimally invasive procedure for atrial fibrillation without cardiopulmonary bypass, it is necessary to create transmural lesions on the beating heart. Although bipolar radiofrequency clamps can isolate the pulmonary veins, they have difficulty in performing any other left atrial lesions, particularly those of the traditional Cox-Maze procedure. This study examined the performance of an internally cooled, bipolar radiofrequency device designed for such an application. METHODS: Eleven domestic pigs underwent median sternotomy. Five animals had eight atrial lesions created with the radiofrequency device at times of 20, 30, 40, and 50 seconds. In six other pigs, the device was compared with another technology that has been used clinically for epicardial, beating heart ablation, the Guidant Flex 4 microwave device. The tissue was stained with 2,3,5-triphenyl-tetrazoluim chloride, and the lesions were sectioned at 5-mm intervals. Lesion width, depth, and transmurality were evaluated. RESULTS: The radiofrequency device had a linear dose-response relationship. Lesions were wider and deeper with increasing ablation times. A total of 40%, 45%, 60%, and 67% of lesions were transmural at times of 20, 30, 40, and 50 seconds, respectively. Ninety-one percent of lesions in tissue up to 4-mm thick were transmural after 50 seconds. However, performance in thicker tissue was poor. Lesions created by the device were deeper and more likely to be transmural than the Flex 4. CONCLUSIONS: This internally cooled, bipolar radiofrequency device can reliably create transmural lesions on tissue up to 4-mm thick and performs better than a microwave device.