Radiation exposure is an underestimated risk in complex ablation procedures. Here, we describe a protocol to significantly decrease fluoroscopy time and dosage for both the patient and the lab staff by using a novel non-fluoroscopic catheter visualization system.
A technological platform (MediGuide) has been recently introduced for non-fluoroscopic catheter tracking. In several studies, we have demonstrated that the application of this non-fluoroscopic catheter visualization system (NFCV) reduces fluoroscopy time and dose by 90-95% in a variety of electrophysiology (EP) procedures. This can be of relevance not only to the patients, but also to the nurses and physicians working in the EP lab. Furthermore, in a subset of indications such as supraventricular tachycardias, NFCV enables a fully non-fluoroscopic procedure and allows the lab staff to work without wearing lead aprons. With this protocol, we demonstrate that even complex procedures such as ablations of atrial fibrillation, that are typically associated with fluoroscopy times of >30 min in conventional settings, can safely be performed with a reduction of >90% in fluoroscopy exposure by the additional use of NFCV.
Catheter ablation has become a standard therapy in the treatment of many arrhythmias. While different ablation strategies have been proposed and are currently applied, all ablation procedures share one commonality in their necessity for the use of fluoroscopy to visualize catheters. Heavy reliance on the use of live x-ray for ablation procedures was alleviated in the 1990s with the advent of 3D electroanatomical mapping systems (EAMS) that helped to significantly reduce radiation time and dosage. Integration of cardiac imaging using magnetic resonance imaging (MRI) and computed tomography (CT) was shown to even further reduce fluoroscopy exposure during ablation procedures1. More recently, a new technology for catheter visualization, called the MediGuide-(MG) technology, has been introduced that can further facilitate reduction in radiation exposure2,3. Details have been previously described4,5. Briefly, single-coil sensors embedded in the catheter tip can be accurately localized by an electromagnetic field. Information about the 3D position and orientation of the tools is then transferred to the fluoroscopy system and is used to visualize the catheter tip in a virtual bi-planar view projected on 2 pre-recorded cine loops. It has been previously shown that the application of the MG technology can lead to a significant reduction in fluoroscopy burden by using diagnostic catheters in atrial flutter4 and by using both diagnostic and ablation catheters in several supraventricular tachycardias (SVT)6 and atrial fibrillation (AF)7 cases. There may be concerns that the application of the non-fluoroscopic catheter visualization (NFCV) technology may increase procedural risks in the absence of the catheter shaft visualization and catheter localization that is solely based on the location of the catheter tip. It was demonstrated that the complication rate is equal or even lower to procedures performed with conventional tools14. This could be explained by a limitation of conventional procedures: only in a certain percentage of the procedure catheters will be “visible”. This changed by application of NFCV technology since catheters will be visible during the entire procedure on this virtual biplanar view.
In this protocol, we perform an ablation of atrial fibrillation in a patient with paroxysmal, drug-refractory and highly symptomatic atrial fibrillation. The goal of this protocol is to achieve the same endpoints as in a conventional procedure, i.e., isolation of all pulmonary veins with proven bi-directional block, and to reduce fluoroscopy exposure for the patient by >90% as compared to conventional settings via the additional use of the NFCV technology.
All patients signed an informed consent form after all typical complications of an ablation procedure such as pericardial effusion, vascular complications at the access site, stroke/TIA, and esophago-atrial fistula, were explained. This fulfilled the requirements of the local ethics committee. No patient subgroup had to be excluded (e.g., patients with pacemakers or ICD); only general contraindications for AF ablation procedures (e.g., contraindication for anticoagulation, hyperthyreosis, valvular AF, etc.) had to be addressed.
1. Patient Setup
2. Ablation Procedure
3. Post-procedural Management
This procedure typically lasts 2-2.5 hr. The patients are under deep analog-sedation, meaning that they are sleeping, receiving analgesics but breathe spontaneously. If all endpoints including bi-directional block in all pulmonary veins, healthy left atrial tissue, and non-inducibility of atrial fibrillation or atrial flutter are achieved, patients have about a 75% probability of freedom from atrial fibrillation recurrence after 12 months. If the left atrium has fibrotic tissue with low voltage areas (see Figure 2), the chances of permanent freedom from arrhythmias decrease compared to patients with healthy left atrial tissue (see Figure 3). Typically, patients can be discharged 24 hr after the procedure. In the first 4-6 weeks after the ablation procedure, short episodes of atrial arrhythmias can occur and are frequent. After 6 weeks, the likely outcomes of the ablation procedure are evident. In most cases, all medical anti-arrhythmic treatments are discontinued on the day of the ablation procedure. Oral anticoagulation is mandatory and needs to be continued after the ablation procedure irrespective of the individual’s stroke risk for at least 3 months.
Figure 1: Ablation of atrial fibrillation using NFCV technology. Left and middle: catheter visualization using the NFCV technology: ablation catheter (red tip) in the left superior pulmonary vein (LSPV, blue marker). Right: the same setting displayed in the 3D mapping system. Ablation catheter (green halo) placed in the left superior pulmonary vein close to the ridge to the left atrial appendage. Esophageal temperature probe posterior to the left atrium (green catheter). Please click here to view a larger version of this figure.
Figure 2: Voltage map of a “diseased” left atrium. 3D reconstructed CT with low-voltage areas at the posterior wall of the left atrium and in the mitral isthmus region indicating areas of previous ablation. Please click here to view a larger version of this figure.
Figure 3: Voltage map of a “healthy” left atrium. 3D reconstructed CT model of a left atrium. A color-coded voltage map is shown with purple for healthy tissue (electrograms >0.5 mV) and grey for scar tissue (electrograms <0.2 mV). Electrogram amplitudes >0.2 mV and <0.5 mV are displayed in yellow, red, and blue. Please click here to view a larger version of this figure.
Video 1: Principle of NFCV. In the beginning of the procedure, 2 short cine loops (3 sec each) are recorded and are used as the dynamic background for catheter visualization. Specially-designed catheters with miniaturized sensors at the tip are inserted in the patient and visualized by the NFCV system. Please click here to view this video.
Radiation exposure for interventional cardiologists and electrophysiologists is an underestimated risk because of its unpredictable side-effects. Current literature reveals a higher incidence of left-sided brain-tumors among this subgroup of clinicians, suggesting that the proximity of the left hemisphere to the X-Ray source may be a culprit12. The latency between radiation exposure and diagnosis of neoplasia has been reported to be 20 years or more. Therefore, today’s interventionalists should use all technological options to reduce radiation exposure to a minimum.
The NFCV system can help reduce fluoroscopy exposure without affecting procedure time14,15 with a workflow that was adapted several times over the past 3 years in order to minimize radiation exposure according to the ALARA principle.
3D mapping systems can help to improve the understanding of complex 3-dimensional structures, but the basic orientation for the operator is generated using conventional fluoroscopy.
The transseptal puncture remains the largest contributing step (75-80%) of the radiation dose during these procedures since no sensor-equipped material for use with NFCV technology is currently available. Especially in unexperienced hands this represents the most critical step in that procedure- other imaging modalities (such as intracardiac or transesophageal echo) can contribute to safe punctures and low complication rates.
The NFCV is not only used in ablation procedures but also in complex implantations such as cardiac resynchronization therapy (CRT). In these procedures, the system allows the reduction of fluoroscopy burden by 75-80% compared to conventional implantations13. A recent publication could show that after a learning curve of 30 – 40 procedures a median fluoroscopy time of 1.1 min for 50 consecutive patients is feasible and safe14. This was confirmed when extending the data acquisition to >500 patients (see Figure 4).
Figure 4: Please click here to view a larger version of this figure.
The limitation of the current available system is that only the tips of the catheters are visualized. Unexperienced operators will probably not be able to interpolate from the orientation of the tip to know what the position of the catheter shaft will be. Furthermore, the system is not able to visualize the transseptal sheath yet. Only a limited choice of catheters are currently available- therefore only a limited number of different procedures is suitable using NFCV technology.
In near future more devices and tools will be available that are equipped with a sensor to be visualized non-fluoroscopically. The system here basically works as a cardiovascular platform for different procedures; electrophysiology is just the first application that has been introduced.
The authors have nothing to disclose.
We acknowledge the funding by SJM.
MediGuide System | SJM | MG1000 | Non fluoroscopic mapping system |
Patient Reference Sensor (PRS) Patch | SJM | H700071 | Reference sensor |
Livewire™ Diagnostic Catheter MediGuide Enabled™ | SJM | D402058 | diagnostic catheter |
Agilis Nxt steerable introducers 71cm small curle | SJM | 408309 | steerable sheath |
BRK transseptal needle and stainless steel stylet | SJM | 408314 | transseptal needle |
EnSite Velocity patch set | SJM | 100003331 | 3D mapping tools |
Safire BLU | SJM | A088087 | Ablation catheter |
Sensitherm | SJM | 26155ST | thermoprobe |
Siemens Artis | Siemens | x | X Ray biplanar |
Ensite Velocity v. 2.1 | SJM | x | 3D mapping system |
Ampere generator | SJM | H700494 | RF generator |
Ampere Remote control | SJM | H700490 | Remote control for generator |
Cool point | SJM | IBI-89003 | Irrigation pump |
Cool point tubing set | SJM | 85785 | Tubing set |