Where it fits
Carto 3 is one of the two systems most EP labs run day to day, alongside Abbott’s EnSite X. It is the native mapping environment for Biosense Webster catheters and is the platform most fellows train on first. Compared with Affera (one-catheter PFA + map) and Rhythmia HDx (ultra-high-density basket), Carto sits in the middle: very versatile, deeply integrated with contact-force RF, and built around a magnetic reference that gives it stable, reproducible geometry for long cases.
Localization technology
Carto 3 uses a hybrid magnetic + impedance scheme.
- A location pad beneath the table generates three low-strength magnetic fields. Sensors embedded in compatible catheter tips report their position in that field — this is the high-accuracy backbone.
- Body surface electrodes (the back-and-chest patch set) drive impedance currents through the patient. Every electrode on every catheter is then localized by impedance, even if it has no magnetic sensor.
- The system continuously cross-corrects impedance against the magnetic reference, so distortions from local impedance changes (saline irrigation, RF lesions, edema) get pulled back into the magnetic ground truth.
The practical result: position accuracy on the order of a millimeter at the tip, with full-shaft visualization of multi-electrode catheters that do not need their own magnetic sensor.
Compatible catheters & accessories
- Mapping catheters — PentaRay (5 splines, 20 electrodes), OptraySense (HD grid-style with contact sensing on selected electrodes), OctaRay (8 splines, very high density).
- Ablation catheters — SmartTouch SF (contact-force, saline-irrigated RF), QDOT MICRO (very-high-power short-duration RF with microelectrodes and temperature monitoring), THERMOCOOL SmartTouch.
- Reference / diagnostic — decapolar CS catheters, His catheters, the system’s body surface ECG patches.
- CARTOSOUND module if intracardiac echo (SoundStar ICE) is being used for integrated chamber reconstruction.
Lab setup
What we prep before the patient is on the table:
- Power the workstation early — boot, login, and patient registration are the slowest steps in the room.
- Confirm the location pad is seated under the table at the level of the heart; sliding it after the drape is up is a non-starter.
- Place skin patches with the patient supine, arms in their final case position:
- Three MetalRef / back patches between the scapulae and along the flanks.
- Body surface ECG patches per the system diagram.
- Grounding / indifferent patch on the back or thigh for RF return.
- Skin prep: clip hair, alcohol, let dry. Wet skin is the most common cause of intermittent impedance.
- Confirm patch impedance in range and stable on a still patient before drape goes up.
- Connect the patient interface unit (PIU) cables for each catheter port and the recording system bridge.
- Load the case profile (AF, atypical flutter, VT, SVT) — this sets defaults for windows, annotation, and map types.
Workflow during the case
A typical AF case flow:
- After femoral access and CS catheter placement, register the CS in Carto and confirm magnetic + impedance signals are clean.
- Transseptal under ICE; bring the mapping catheter (PentaRay or OctaRay) into the LA.
- Build LA geometry with ConfiDENSE auto-acquisition — the system streams points, filters by cycle length, stability, and position, and assembles a high-density map without manual point-by-point capture.
- Tag PV ostia, LAA, esophagus position, mitral annulus.
- Switch to SmartTouch SF or QDOT MICRO for ablation; CARTO tracks contact force, impedance drop, and lesion tags in real time.
- After PVI, re-acquire a quick voltage / activation map to confirm isolation and check for gaps.
- For substrate cases, CARTO PRIME layers in scar analysis, late potentials, and channel detection on the voltage map.
- CARTO REPLAY lets the team scroll back through the case timeline if a question comes up about a specific lesion or signal.
What’s distinctive
- Magnetic reference makes the geometry feel locked-in — small patient movement is corrected rather than destroying the map.
- Deep integration with contact-force RF: every lesion carries force, time, impedance, and (on QDOT) temperature data.
- CARTOSOUND fuses ICE-acquired chamber contours into the Carto geometry — useful for complex LA anatomy and for VT cases needing intramural awareness.
- Strong automation suite (ConfiDENSE, PRIME, REPLAY) reduces manual annotation time.
- Catheter ecosystem is closed — non-Biosense catheters will visualize via impedance only and may not be fully supported.
Common pitfalls
- Location-pad shift. Bumping the pad during patient transfer or repositioning shifts the magnetic frame; geometry built before the shift is now wrong. Recognize as sudden, uniform offset of every catheter; fix by re-registering or rebuilding.
- Patient movement. A coughing, shifting, or repositioned patient breaks the impedance correction. If the map suddenly looks distorted, check the patient first.
- MetalRef / metal artifacts. Stray metal on or near the field — a forgotten hemostat, an unshielded cable, ICE catheter cable looped over a back patch — produces local geometry distortion. Sweep the field if something looks off.
- Patch lift. Long cases, sweating, and adhesive failure cause patches to peel. Impedance drifts, points start landing in wrong places. Replace the patch, re-verify, and consider re-registration.
- Wrong case profile loaded — annotations and windows will be set for the wrong rhythm; easy to miss until the map looks nonsensical.
- Cable to recording system not bridged — points are taken but signals are not annotated to surface ECG; activation maps are useless.
Staff role
- Before the case — patch placement, system boot, patient registration, cable check, catheter profile loaded.
- During the case — mapping tech drives point acquisition, calls out stability and contact, saves the map at every checkpoint, and flags drift or impedance issues to the operator immediately.
- Nurses and techs — protect the patches and cables during repositioning, watch for patient movement under drape, and keep metal off the field.
- End of case — save final maps, export to the case archive, power down per lab protocol.