Cardiac image integration implications for atrial fibrillation ablation

Extracardiac findings on cardiac computed tomography in patients undergoing atrial fibrillation catheter ablation

Abstract Background and Aim

To assess the prevalence of incidental extracardiac findings in patients who underwent cardiac CT for the evaluation of left atrial (LA) anatomy before atrial fibrillation (AF) catheter ablation. We also aimed to determine the independent predictors of relevant extracardiac alterations.

Patients and Methods

We studied consecutive patients who underwent cardiac CT with a 256-slice scanner for the visualization of LA anatomy before AF ablation. Prevalence of clinically significant and not significant extracardiac findings were recorded. Moreover, we determined the variables associated with relevant extracardiac alterations with uni- and multivariate logistic regression analyses.

Results

In total, 1,952 consecutive patients who underwent cardiac CT examination between 2010 and 2020 were included in our study (mean age 61.2±10.6 years; 66.2% male). Incidental extracardiac findings were detected in 820 (42.0%; 95%CI=0.40-0.44%) patients, while clinically significant alterations were reported in 416 (21.3%; 95%CI=20.0-23.2%) patients. When analyzing the predictors of clinically relevant alterations, age (OR=1.04; 95%CI=1.03- 1.05), male sex (OR=1.39; 95%CI=1.12-1.73), chest pain (OR=1.46; 95%CI=1.09-1.93), hypertension (OR=1.42; 95%CI=1.12-1.81), heart failure (OR=1.68; 95%CI=1.09-2.53), obstructive CAD (OR=1.56; 95%CI=1.16-2.09) and prior stroke/TIA (OR=1.56; 95%CI=1.04- 2.30) showed association with clinically significant incidental findings in the univariate analysis (all p<0.05). In the multivariate analysis, age (OR=1.04; 95%CI=1.02-1.06; p<0.001) proved to be the only significant predictor of clinically relevant extracardiac finding.

Conclusion

Cardiac CT performed before AF ablation is not only helpful in understanding LA anatomy, but might also identify clinically significant pathologies. These incidental findings might have further diagnostic or therapeutic consequences.

Collateral findings during computed tomography scan for atrial fibrillation ablation: Let’s take a look around

The growing number of atrial fibrillation catheter ablation procedures warranted the development of advanced cardiac mapping techniques, such as image integration between electroanatomical map and cardiac computed tomography. While scanning the chest before catheter ablation, it is frequent to detect cardiac and extracardiac collateral findings. Most collateral findings are promptly recognized as benign and do not require further attention. However, sometimes clinically relevant collateral findings are detected, which often warrant extra diagnostic examinations or even invasive procedure, and sometimes need to be followed-up over time. Even though reporting and further investigating collateral findings has not shown a clear survival benefit, almost all the working groups providing data on collateral findings reported some collateral findings eventually coming out to be malignancies, sometimes at an early stage. Therefore, there is currently no clear agreement about the right strategy to be followed.

Voltage-based device tracking in a 1.5 Tesla MRI during imaging: initial validation in swine models

PURPOSE

Voltage-based device-tracking (VDT) systems are commonly used for tracking invasive devices in electrophysiological cardiac-arrhythmia therapy. During electrophysiological procedures, electro-anatomic mapping workstations provide guidance by integrating VDT location and intracardiac electrocardiogram information with X-ray, computerized tomography, ultrasound, and MR images. MR assists navigation, mapping, and radiofrequency ablation. Multimodality interventions require multiple patient transfers between an MRI and the X-ray/ultrasound electrophysiological suite, increasing the likelihood of patient-motion and image misregistration. An MRI-compatible VDT system may increase efficiency, as there is currently no single method to track devices both inside and outside the MRI scanner.

METHODS

An MRI-compatible VDT system was constructed by modifying a commercial system. Hardware was added to reduce MRI gradient-ramp and radiofrequency unblanking pulse interference. VDT patches and cables were modified to reduce heating. Five swine cardiac VDT electro-anatomic mapping interventions were performed, navigating inside and thereafter outside the MRI.

RESULTS

Three-catheter VDT interventions were performed at >12 frames per second both inside and outside the MRI scanner with <3 mm error. Catheters were followed on VDT- and MRI-derived maps. Simultaneous VDT and imaging was possible in repetition time >32 ms sequences with <0.5 mm errors, and <5% MRI signal-to-noise ratio (SNR) loss. At shorter repetition times, only intracardiac electrocardiogram was reliable. Radiofrequency heating was <1.5°C.

CONCLUSION

An MRI-compatible VDT system is feasible.

Quantitative modeling of the accuracy in registering preoperative patient-specific anatomic models into left atrial cardiac ablation procedures

PURPOSE

In cardiac ablation therapy, accurate anatomic guidance is necessary to create effective tissue lesions for elimination of left atrial fibrillation. While fluoroscopy, ultrasound, and electroanatomic maps are important guidance tools, they lack information regarding detailed patient anatomy which can be obtained from high resolution imaging techniques. For this reason, there has been significant effort in incorporating detailed, patient-specific models generated from preoperative imaging datasets into the procedure. Both clinical and animal studies have investigated registration and targeting accuracy when using preoperative models; however, the effect of various error sources on registration accuracy has not been quantitatively evaluated.

METHODS

Data from phantom, canine, and patient studies are used to model and evaluate registration accuracy. In the phantom studies, data are collected using a magnetically tracked catheter on a static phantom model. Monte Carlo simulation studies were run to evaluate both baseline errors as well as the effect of different sources of error that would be present in a dynamic in vivo setting. Error is simulated by varying the variance parameters on the landmark fiducial, physical target, and surface point locations in the phantom simulation studies. In vivo validation studies were undertaken in six canines in which metal clips were placed in the left atrium to serve as ground truth points. A small clinical evaluation was completed in three patients. Landmark-based and combined landmark and surface-based registration algorithms were evaluated in all studies. In the phantom and canine studies, both target registration error and point-to-surface error are used to assess accuracy. In the patient studies, no ground truth is available and registration accuracy is quantified using point-to-surface error only.

RESULTS

The phantom simulation studies demonstrated that combined landmark and surface-based registration improved landmark-only registration provided the noise in the surface points is not excessively high. Increased variability on the landmark fiducials resulted in increased registration errors; however, refinement of the initial landmark registration by the surface-based algorithm can compensate for small initial misalignments. The surface-based registration algorithm is quite robust to noise on the surface points and continues to improve landmark registration even at high levels of noise on the surface points. Both the canine and patient studies also demonstrate that combined landmark and surface registration has lower errors than landmark registration alone.

CONCLUSIONS

In this work, we describe a model for evaluating the impact of noise variability on the input parameters of a registration algorithm in the context of cardiac ablation therapy. The model can be used to predict both registration error as well as assess which inputs have the largest effect on registration accuracy.

Prevalence and clinical significance of collateral findings detected by chest computed tomography in patients undergoing atrial fibrillation ablation

AIMS

Chest computed tomography (CT) scanning is increasingly used as an imaging technique in patients undergoing atrial fibrillation (AF) catheter ablation. Chest CT scans visualize organs other than the heart and collateral findings may be identified incidentally. Our study aims to assess the prevalence and clinical relevance of such collateral findings in patients undergoing AF ablation.

METHODS AND RESULTS

One hundred and seventy-three patients (127 males, age 59 ± 10 years) underwent chest CT scan for image integration in AF ablation. Collateral findings from visualized thoracic and upper abdominal organs were collected. Findings that required further investigations or treatment according to current guidelines were considered as clinically significant. A total of 164 collateral findings were identified in 97 (56%) patients, and most patients showed abnormalities of the lungs (67 patients, 39%). Forty-nine (28%) patients had clinically significant findings needing further investigation and 17 (10%) of them required specific treatments, including three cases (1.7 %) of lung malignancy.

CONCLUSIONS

Chest CT images acquired for integration in AF ablation should be read thoroughly as they may serve as a screening tool for otherwise unrecognized clinically significant conditions of the heart, lungs, or other visualized organs.

The Pericardial Space: Obtaining Access and an Approach to Fluoroscopic Anatomy

The pericardial space is now increasingly used as a means and vantage point for mapping and ablating various arrhythmias. In this review, present techniques to access the pericardial space are examined and potential improvements over this technique discussed. The authors then examine in detail the regional anatomy of the pericardial space relevant to the major arrhythmias treated in contemporary electrophysiology. In each of these sections, emphasis is placed on anatomic fluoroscopic correlation and avoiding complications that may result.