In this feature interview, EP Lab Digest speaks with Ramesh Hariharan, MD and Rajesh Venkataraman, MD — two electrophysiologists from Houston Methodist who recently converted to Abbott’s EnSite Precision™ Cardiac Mapping System and TactiCath™ Quartz Contact Force Ablation Catheter. They discuss why they decided to convert, as well as benefits of the mapping system and contact force catheter. Dr. Hariharan is Chief of Cardiac Electrophysiology and a Professor of Medicine at McGovern Medical School at UTHealth. Dr. Venkataraman is with UT Physicians – EP Heart (EPH) and is an Assistant Professor of Cardiac Electrophysiology at The University of Texas Health Science Center at Houston.
What do you think are the key features of the EnSite Precision Cardiac Mapping System? Has this technology met or exceeded your expectations?
The older EnSite (Velocity) mapping system was based on impedance, and hence, was dependent on the reference catheter position — usually the decapolar catheter. Certainly, the older system did have a system reference, but this was not as accurate. The new EnSite Precision Cardiac Mapping System, which has both magnetic- and impedance-based points, is a major advancement. Using the system reference has allowed us to lean more on the system during catheter placement; this, in turn, has allowed for an overall reduction of fluoro time and dosage during procedures. Another leap forward with this blended system is that the new magnetic points are gaited to end respiration, so regardless of whether the patient has shallow or deep inhalation, end respiration is consistent every time. Consistency leads to stability, and stability leads to a better outcome for the patient.
How many and what kinds of cases have you performed with the EnSite Precision Cardiac Mapping System?
As a citywide practice, EPH has performed approximately 100 procedures using the EnSite Precision Cardiac Mapping System. The majority of these cases are for pulmonary vein isolation (PVI) and supraventricular tachycardia (SVT). I would estimate that it is a 60/30/10 split between SVT/PVI/PVC.
What attracted you to start using the EnSite Precision Cardiac Mapping System?
Again, the combination of magnetic- and impedance-based points as well as subsequent improvement in accuracy attracted us to upgrade our current EnSite (Velocity) system. The integration of magnetics assists in both field scaling and geometrical point collection. Automated features such as AutoMap and AutoMark take the ambiguity out of data points and lesion location. Having the stability of the catheter reference, as well as ability to rely on system reference from the moment the catheter enters the body, creates an accurate geometry from groin to the superior vena cava. Finally, high-density point maps can be easily and quickly created from any catheter of our choice.
How has the system helped you to achieve successful results for your patients, and has it changed your patient treatment strategy? Could you discuss an example case?
Our patient strategy and PVI workflow have remained unchanged; however, creating a stable map and performing wide area circumferential ablation around the PVs has become much easier. We use endotracheal intubation and complete paralysis for our atrial fibrillation cases; coupled with a somewhat lower tidal volume, which results in minimal patient movement, and the new Precision system, the ablation points are marked very accurately. Further, most patients require a cavotricuspid isthmus ablation; coupling with a FlexAbility ablation catheter (Abbott) results in markedly faster procedure times.
Why is automation important in the diagnosis and delivery of therapy to your patients in EP procedures? How does the EnSite Precision Cardiac Mapping System help you achieve this?
The answer is twofold. While the geometry and imaging on our mapping screen is static, one must not forget we are working in a very dynamic environment. While we are navigating chambers of the heart, especially the left atrium, catheters can push and stretch the thin walls of the veins while creating geometry. By having the system mark lesions in a 3D matrix, it can verify any push or give that may have been created with that venous geometry. More importantly, the primary benefit of properly annotating therapeutic lesions is to assist in identifying any leaks (gaps) with our lesion set, whether it be a straight line or encompassing an os (ostium) of a vein. Finally, the flexibility of combining multiple data sets within one lesion and visualizing it, such as impedance drop and time, helps confirm successful lesion placement.
What advice do you have for your peers considering the EnSite Precision?
There are so many new features with this system, that it isn’t just a system upgrade — it is a completely revamped mapping system. For each case, use one new feature at a time. It can be overwhelming to try using every new feature for every case, and that is just not efficient. Also, since it is still an open platform system, you can use any impedance-based catheter for geo collection, such as the Reflexion Spiral (Abbott). Physicians can create a mix of the catheters that they are comfortable with alongside the new magnetic sensor-enabled catheters.
How has the stability of the EnSite Precision Cardiac Mapping System improved?
We have moved from using an internal coronary sinus (CS) reference to using the system reference; this has allowed us more freedom, especially during atypical flutters, if we have to ablate within the CS. In addition, we rely on the system reference to assist in minimizing our fluoro exposure by using the mapping system to follow catheters up from the groin and place catheters in the heart. Lastly, a small but critical improvement has been the adhesiveness of the skin patches. They are better designed for our older female patients, and the patches stay exactly where they are placed, even if the patient sweats on the table. The adhesive prevents any potential movement from sweat, patient movement, or from accidently being pulled on by other components and cabling on the table.
Does lateral contact force accuracy matter in a case? How often?
Very rarely is a physician touching the tissue surface with the catheter at a 90-degree angle throughout the entire case. The lateral force is crucial to assure contact, especially if one is ablating tissue by dragging the catheter along the surface. Another area that is critical to lateral force is during typical atrial flutter ablations, when the catheter comes near the inferior vena cava (IVC). At that point, one is nearly always horizontal and precariously positioned at the IVC/RA junction. That particular area of anatomy will always need lateral contact to ablate.
Further, we use the Flex Ablation Catheter (Abbott), which deforms when force is applied laterally, opens up the irrigation ports, and enhances lesion size. The ablation electrograms in the Flex ablation catheter also have a higher fidelity.
Are you using the 12-lead morphology score match to map PVCs? How has the AutoMap feature impacted your workflow?
The 12-lead match is extremely useful when there is a lack of ectopy and very few actual PVCs to map. Having a true mathematical calculation to determine how close our pacemap is to the clinical PVC takes all guesswork away from where the site of interest or breakout area lies. This has changed the pacemap conversation from “this is close, this matches in a few leads, but is not as peaked in others” to “you only have a 60% match” or “you have a 95% match — this is our area of interest.” There is more certainty in our maps.
In regards to AutoMap, we prefer to use the Reflexion Spiral within the left atrium. Coupled with AutoMap, it has allowed us to create high-density maps in a relatively short amount of time. For example, we recently mapped 8400 points in about 10 minutes with the combination of Reflexion Spiral and AutoMap software.
What features of EnSite Precision Cardiac Mapping System have you used to help define your ablation strategy for patients?
The flexibility of this system allows us to still use catheters such as the Reflexion Spiral to create high definition and high point density maps. This allows us to rely more on system reference to follow catheters up from the groin and minimize fluoro for both ourselves and the patient. Using this system with MediGuide allows us to also visualize the temp probe in the esophagus for an additional layer of safety, helping us track the ablation catheter while ablating on the posterior wall.
Disclosures: The authors have no conflicts of interest to report regarding the content herein. Outside the submitted work, Dr. Hariharan reports personal fees for training other physicians as part of St. Jude Medical’s (now Abbott) LV Lead program.