Catheter ablation for atrial arrhythmias in adults with congenital heart disease: recurrence rates and predictors of acute procedural success

Funding Acknowledgements

Type of funding sources: None.

Background

Heart rhythm disorders are an important cause of morbidity and emergency hospitalisation in patients with adult congenital heart disease (ACHD), and this is due to a combination of surgical scar, residual haemodynamic lesions, and cardiac chamber dilatation. The most effective available treatment is catheter ablation, although this can be extremely challenging owing to abnormal anatomy and problems accessing intra cardiac sites critical to the arrhythmia mechanism. However, outcomes of catheter ablation and analysis of factors which may predict recurrence of arrhythmia remain poorly defined. 

Purpose 

To define the cohort of ACHD patients undergoing catheter ablation for atrial arrhythmia in a large tertiary centre, characterise outcomes, and determine factors associated with arrhythmia recurrence.

Methods

Retrospective study of all catheter ablations for atrial arrhythmias in ACHD patients between April 13, 2016 and December 16, 2019 at our institution.  Patients were identified using a field search through a centralised database; and pre-specified clinical and procedural data of interest, and time from ablation to recurrence were determined from the computerised electronic record. Binary logistical regression and cox regression analysis were used to determine potential predictors of acute procedural success and arrhythmia recurrence respectively. 

Results

Among 90 patients (mean age 43 ± 15 years) who underwent catheter ablation for atrial arrhythmia, 39 (43%) were treated for macro-reentrant atrial tachycardia, 19 (21%) for focal atrial tachycardia, 9 (10%) for multifocal atrial tachycardia, 10 (10%) for atrial fibrillation, 7 (8%) for atrioventricular nodal reentrant tachycardia, and 6 (7%) for atrioventricular reentrant tachycardia. 35 (39%) of patients had "severe" complexity ACHD as per the Bethesda classification. 35 (39%) experienced recurrent arrhythmia with a median time to recurrence of 120 days. Age, gender, body mass index, complexity of congenital heart disease, and previous surgical repair were not identified as being significantly associated with recurrence, however univariate cox regression analysis showed a significantly longer time to recurrence in cases utilising electroanatomical mapping and demonstrating non-inducibility of arrhythmia in the lab post ablation (p < 0.001). There was 1 case of post-ablation bradycardia requiring pacemaker implantation, but no other complications.

Conclusion

Catheter ablation for atrial arrhythmia in ACHD patients is safe and effective, with a majority of patients achieving multiple arrhythmia-free months. Non-inducibility of arrhythmia post procedure and use of electroanatomical mapping are predictors of freedom from recurrence of atrial arrhythmia, suggesting effective characterisation and ablation of the arrhythmia mechanism is more important than the underlying substrate. These findings may aid management decisions for recurrent arrhythmia in ACHD patients.

The stability of imaging biomarkers in radiomics: a framework for evaluation

This paper studies the sensitivity of a range of image texture parameters used in radiomics to: (i) the number of intensity levels, (ii) the method of quantisation to select the intensity levels and (iii) the use of an intensity threshold. 43 commonly used texture features were studied for the gross target volume outlined on the CT component of PET/CT scans of 50 patients with non-small cell lung carcinoma (NSCLC). All cases were quantised for all values between 4 and 128 intensity levels using four commonly used quantisation methods. All results were analysed with and without a threshold range of  -200 HU to 300 HU. Cases were ranked for each texture feature and for all quantisation methods with the Spearman's rank correlation coefficient determined to evaluate stability. Results showed large fluctuations in ranking, particularly for low numbers of levels, differences between quantisation methods and with the use of a threshold, with values Spearman's Rank Correlation for many parameters below 0.2. Our results demonstrated the sensitivity of radiomics features to the parameters used during analysis and highlight the risk of low reproducibility comparing studies with slightly different parameters. In terms of the lung cancer CT datasets, this study supports the use of 128 intensity levels, the same uniform quantiser applied to all scans and thresholding of the data. It also supports several of the features recommended in the literature for such studies such as skewness and kurtosis. A recommended framework is presented for curation of the data analysis process to ensure stability of results.

Adapting clinical gamma cameras for body monitoring in the event of a large-scale radiological incident

After a release of radionuclides, accidental or otherwise, there will be an urgent need to identify members of the general public who have received a significant intake of radioactive material, sufficient to require medical treatment or further investigation. A large number of people could be contaminated in such an incident. For gamma-ray emitting radionuclides this screening could be carried out using gamma camera medical imaging systems, such as those that are present in many large UK hospital sites. By making a number of simple reversible changes such as removal of collimators, these cameras could be employed as useful additional screening instruments as well as an aid in contamination control. A study was carried out to investigate which systems were present in sufficient number to offer wide scale coverage of UK population centres. Nine gamma cameras (eight dual head and one single head) were assessed using point source and bottle mannequin (BOMAB) phantom measurements so that a mathematical model could be developed for use with the MCNPX Monte Carlo radiation transport code. The gamma camera models were assessed for practical seated and supine geometries to give calibration factors for a list of target radionuclides that could be released in a radiological incident. The minimum detectable activities (MDAs) that were achieved for a five minute measurement demonstrated that these systems are sufficiently sensitive to be used for screening of the general public and are comparable to other body monitoring facilities. While gamma cameras have on-board software that are designed for imaging and provide for a gamma-ray energy range suitable for radionuclides for diagnostic imaging (such as ^99mTc), they are not as versatile as custom-built body monitoring systems.

The role of texture analysis in imaging as an outcome predictor and potential tool in radiotherapy treatment planning

Predicting a tumour's response to radiotherapy prior to the start of treatment could enhance clinical care management by enabling the personalization of treatment plans based on predicted outcome. In recent years, there has been accumulating evidence relating tumour texture to patient survival and response to treatment. Tumour texture could be measured from medical images that provide a non-invasive method of capturing intratumoural heterogeneity and hence could potentially enable a prior assessment of a patient's predicted response to treatment. In this article, work presented in the literature regarding texture analysis in radiotherapy in relation to survival and outcome is discussed. Challenges facing integrating texture analysis in radiotherapy planning are highlighted and recommendations for future directions in research are suggested.