An analysis of the influence of atrial wall thickness on the protective effects of proactive esophageal cooling during high-power short-duration radiofrequency ablation

Background

The use of proactive esophageal cooling using a dedicated cooling device during radiofrequency (RF) left atrial ablation has increased, with endoscopic studies showing reductions in esophageal lesions using medium power ablation settings. With no atrioesophageal fistula yet identified using esophageal cooling, and clinical practice increasingly shifting to high-power short-duration (HPSD) ablation, additional data on the protective potential of this technique in HPSD ablation may help guide RF ablation strategies. In particular, a better understanding of the effects of anatomical variations in myocardial thickness on cooling efficacy is warranted.

Purpose

We sought to evaluate the influence of atrial wall thickness on the protective effects of proactive esophageal cooling during HPSD ablation.

Methods

Using a computer model of the left atrium and esophagus, we analyzed the esophageal damage that occurs under two HPSD ablation conditions (50 W for 10 s and 90 W for 4 s) with and without proactive esophageal cooling while varying atrial wall thickness. Injury to the esophagus was quantified using the Arrhenius equation as well as by determining the percentage of tissue reaching a 50°C lethal isotherm. Atrial thickness was varied between 0.6 mm to 2.0 mm. Esophageal cooling was set to the recommended 4°C coolant temperature.

Results

Using 50 W power settings in control (non-cooled) conditions, esophageal lesion transmurality ranged from 75% to 82% as calculated by the Arrhenius equation, with decreased transmurality seen as atrial wall thickness increased. With the addition of proactive cooling, lesion transmurality decreased to less than 43% in the thinnest atrial wall sections, and to less than 25% in the thickest atrial wall sections. Using 90 W power settings, control conditions showed esophageal lesion transmurality ranging from 52% to 63%, with the greatest damage seen in the middle-range atrial thicknesses (1 and 1.5 mm). Active esophageal cooling reduced this esophageal injury to less than 12% transmurality through the esophagus in all anatomic scenarios.

Conclusions

Modeling suggests that the use of proactive esophageal cooling significantly reduces esophageal lesion transmurality under HPSD ablation conditions across a range of typical atrial wall thicknesses, including in very thin myocardium, where the risk of esophageal injury is greatest.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Attune

Influence of tissue thickness on thermal latency during high-power short-duration radiofrequency ablation with proactive esophageal cooling

Funding Acknowledgements

Type of funding sources: None.

Background

Thermal latency, or delayed heating, is increasingly recognized as an important factor in the formation of both intentional and unintentional lesions during radiofrequency (RF) ablation for the treatment of atrial fibrillation (AF). High-power short-duration (HPSD) ablation appears to have greater thermal latency than low or medium power ablation. Proactive esophageal cooling (PEC) has been shown to reduce esophageal lesion formation under a variety of conditions by directly reducing the effects of thermal latency, but the influence of anatomic dimensions on the protective efficacy of cooling during HPSD ablation has not been investigated.

Purpose

Determine the impact of changes in pericardial tissue thickness on thermal latency in order to quantify the protective efficacy of PEC across a range of anatomic dimensions.

Methods

We created a mathematical model of the left atrium undergoing HPSD ablation, both with and without a PEC device in place, using a range of pericardial tissue thicknesses (0.5, 0.75, and 1 mm). HPSD ablation was set at 50 W for 10 s, or 90 W for 4 s. We then examined the temperature dynamics at a range of thickness, focusing on the layer of mostly fatty tissue between the atrial and esophageal walls by varying the thickness of this layer while quantifying the degree of esophageal damage using the Arrhenius equation to determine the fraction of damage after peak heating has occurred.

Results

Under control conditions, the growth of lesions from RF ablation at both 50 W and 90 W was found to continue for greater than 10 seconds beyond the cessation of RF energy application. Esophageal lesion formation ranged from 71% to 96% transmurality after 50 W ablation for 10 s, and from 50% to 72% transmurality after 90 W ablation for 4 s. With PEC in place, esophageal lesion transmurality was markedly reduced, with a maximum transmurality ranging from 12% to 32% with 50 W ablation, and from 2% to 20% with 90 W ablation (Figure). Increasing thickness of pericardial tissue (with simulations of 0.5, 0.75, and 1 mm) resulted in decreasing esophageal lesion transmurality (67%, 74%, and 83% at 50 W power, and 72%, 82%, and 96% at 90 W power, respectively, with the 0.5, 0.75, and 1 mm simulations).

Conclusions

Thermal latency with HPSD ablation contributes to lesion growth and can cause esophageal injury. Proactive esophageal cooling counteracts this effect across a range of pericardial tissue thicknesses, and reduces esophageal lesion transmurality by an average of 79%.

Trends and patterns in electrophysiologic and ablation catheter reuse in the United States

In a survey of 140 electrophysiologic laboratories in the USA, 49% reuse catheters to some extent. Catheter reuse is associated with significant reductions in cost but is not conducted in a standardized fashion.

Modulation of terminal deoxynucleotidyltransferase activity by the DNA-dependent protein kinase

Rare Ig and TCR coding joints can be isolated from mice that have a targeted deletion in the gene encoding the 86-kDa subunit of the Ku heterodimer, the regulatory subunit of the DNA-dependent protein kinase (DNA-PK). However in the coding joints isolated from Ku86-/- animals, there is an extreme paucity of N regions (the random nucleotides added during V(D)J recombination by the enzyme TdT). This finding is consistent with a decreased frequency of coding joints containing N regions isolated from C.B-17 SCID mice that express a truncated form of the catalytic subunit of the DNA-PK (DNA-PKCS). This finding suggests an unexpected role for DNA-PK in addition of N nucleotides to coding ends during V(D)J recombination. In this report, we establish that TdT forms a stable complex with DNA-PK. Furthermore, we show that DNA-PK modulates TdT activity in vitro by limiting both the length and composition of nucleotide additions.

Safety and efficacy of hydrogen peroxide plasma sterilization for repeated use of electrophysiology catheters

OBJECTIVES

The purpose of this study was to evaluate a new technique for sterilizing nonlumen electrophysiology catheters that uses hydrogen peroxide gas plasma.

BACKGROUND

The reuse of electrophysiology catheters may potentially result in a significant cost savings. While ethylene oxide sterilization appears to be safe and effective from a clinical standpoint, toxic ethylene oxide residuals, which exceed Food and Drug Administration standards, have been reported.

METHODS

Ten nonlumen electrophysiology catheters were extensively evaluated. Each catheter was used five times and resterilized after each use with hydrogen peroxide gas plasma. Tests for sterility, mechanical and electrical integrity, chemical residuals and standard and electron microscopic inspection were performed.

RESULTS

Loss of electrical integrity or mechanical integrity was not observed in any catheter. No evidence of microbial contamination was found. Surface integrity was preserved except for one ablation catheter that exhibited fraying of the insulation at the insulation-electrode interface. Surface inspection using standard magnification and electron microscopy revealed no significant change in surface characteristics associated with the sterilization process. Hydrogen peroxide was the only chemical residual noted, with an average concentration of 0.22% by weight, which is within accepted American Association for the Advancement of Medical Instrumentation limits. The cost for a standard electrophysiology catheter ranges from $200 to $800, and one sterilization cycle costs $10. If electrophysiology catheters are used five times, resterilization could potentially result in a savings of $2,000 per catheter, or $9,000 for five ablation procedures.

CONCLUSIONS

Hydrogen peroxide gas plasma sterilization may provide a cost-effective means of sterilizing nonlumen electrophysiology catheters without the problem of potentially harmful chemical residuals. However, careful visual inspection of catheters, particularly at the insulation-electrode interface, is required if catheter reuse is performed.

Radiofrequency catheter ablation versus medical therapy for initial treatment of supraventricular tachycardia and its impact on quality of life and healthcare costs

We prospectively compared the impact on quality of life and cost effectiveness between ablation and medication as an initial strategy for patients with paroxysmal supraventricular tachycardia (SVT). Seventy-nine consecutive patients with newly documented paroxysmal SVT were treated with either ablation or medication. Health surveys (SF-36 and disease-specific questions) were obtained at baseline and after 12 months of follow up. Cost of health care utilization for the 6 months before and after treatment were measured. Both medication and ablation improved quality of life. However, ablation improved quality of life in more general health categories than medication. At follow up, ablation was associated with significantly improved quality of life in the bodily pain (63+/-24 vs 81+/-20, p <0.005), general health (69+/-21 vs 79+/-21, p <0.05), vitality (55+/-21 vs 66+/-22, p <0.05), and role emotion (78+/-36 vs 94+/-17, p <0.05) categories when compared with medication. Although both medication and ablation decreased frequency of disease-specific symptoms, ablation resulted in complete amelioration of symptoms in more patients (33% vs 74%). Potential long-term costs were similar for medication and ablation. In conclusion, ablation improves health-related quality of life to a greater extent, and in more aspects of general and disease-specific health than medication.

A left free-wall, decrementally conducting, atrioventricular (Mahaim) fiber: diagnosis at electrophysiological study and radiofrequency catheter ablation guided by direct recording of a Mahaim potential

A 64-year-old female with Wolff-Parkinson-White syndrome and an ECG demonstrating a right posterolateral accessory pathway was referred for electrophysiological study. During electrophysiological testing two AV pathways were identified: a right posterolateral pathway that displayed conventional electrophysiological properties: and a left free-wall pathway that conducted only anterogradely and demonstrated decremental properties. Two separate wide complex tachycardias were induced that utilized the left free-wall pathway anterogradely and either the AV node or the right posterolateral accessory pathway retrogradely. A discrete electrical potential on the free wall of the mitral annulus was identified during tachycardia and was utilized to facilitate mapping and ablation.