Initial Experience With a PaSo Module Upgrade to Biosense Webster’s Carto 3 System

The PaSo Module upgrade to the Carto 3 system (Biosense Webster, Inc., a Johnson & Johnson company) is used in the evaluation of ventricular tachycardia (VT) morphology and to increase efficiency in mapping VT. PaSo is designed fundamentally to help physicians automatically compare pace map signals with arrhythmia signals. 

The PaSo Module automatically checks all VT morphologies to pacing sites to find the best match. 

Dr. Kaufman, a cardiac electrophysiologist at Porter Regional Hospital, became aware of the PaSo Module upgrade at an early stage of marketing and wanted to evaluate the impact of this new software in providing better patient care and outcomes. Specifically, he was interested in learning whether, based on initial experience, PaSo would reduce procedural time, increase patient safety with the potential reduction of inappropriate ablation applications, and improve the mapping of VT arrhythmias. Included here are our observations as well as a brief case. 

About the Hospital

Porter Regional Hospital opened its doors to the public on August 25, 2012. It had taken only 26 months to construct a state-of-the-art hospital that was double in size from the previous facility.

A great deal of attention was focused on ensuring that cardiovascular care was located in one centralized area in the new hospital. Thus, the Center for Cardiovascular Medicine was created and designed to provide comprehensive evaluation, consultation, and medical and surgical management of the heart and circulatory system for the region. The Center has 15 private cardiac admission rooms and four cardiac procedural rooms including an electrophysiology lab. The EP lab was newly equipped with a biplane imaging system, cardiac mapping systems, and monitoring and ablation systems. 

The facility recently achieved accreditation as a recognized Chest Pain Center and also has initiated a strategic alliance with the Cleveland Clinic. This partnership will provide detailed information about the Center’s cardiovascular services, including process and outcome data.

Specialized Equipment

To meet the requirements for the modular upgrade, the center’s Carto 3 system required a software upgrade to Version 3.1. This was achieved with a recent software update from Biosense Webster called Multi-Electrode Mapping (MEM), which allows the acquisition of multiple mapping points simultaneously with MEM-enabled catheters. Of these MEM-enabled devices, the PentaRay or DecaNav mapping catheters were the two recommended for this type of ventricular arrhythmia. Under consultation with Porter Regional Hospital’s Biosense Webster Regional Educational Specialist, Chris Fillier, the DecaNav catheter was chosen for this particular case.

Case Study

A suitable patient requiring a ventricular tachycardia (VT) ablation was selected by Dr. Kaufman. All risks and benefits were explained to the patient and a procedural date was scheduled.

The patient is a 69-year-old male who was referred for an electrophysiology consult for evaluation of palpitations and an abnormal Holter monitor. His cardiac history included a sustained episode of VT at approximately 170 bpm and palpitations. A baseline EKG showed left atrial dilation, left ventricular hypertrophy with a normal ejection fraction of 55%, some mitral annular calcification and normal pulmonary artery (PA) pressures.

The Holter monitor consisted of activity showing 3,657 ventricular ectopic beats, of which 1,102 beats were in one run lasting nine minutes at a rate of 167 bpm. The patient showed no adverse symptoms during this episode.

At the beginning of April 2013, an EP study was performed and indicated normal conduction properties. An easily reproducible, monomorphic VT was produced with a cycle length of 460 ms. A right bundle branch block with normal axis was also noted.

With the physician’s recommendation, discussion of risks and benefits, and the patient’s agreement, an ablation for VT was scheduled and performed in late April 2013.

Assistance with optimal Carto patch placement, grounding patch placement and 12-lead positioning was performed. This support was provided to the physician and staff for this first case from Porter Regional Hospital’s Biosense Webster Regional Education Specialist. 

Under monitored anesthesia care, an 8 French and 7 French sheath were inserted into the right femoral vein at two separate sites. An 8 French sheath was also inserted into the right femoral artery. Through these, a 6 French quadripolar pacing catheter was positioned into the right ventricular apex. Pacing was performed with extrastimuli at 500/320 and a sustained VT was induced. This tachycardia had a cycle rate of 140 bpm and had a right bundle branch block. The patient remained hemodynamically stable while in this rhythm. A DecaNav catheter was inserted via the arterial sheath, and a detailed activation map using the Carto 3 system was obtained of the left ventricle. To reduce the risk of thrombus formation, heparin was initiated with regular activated clotting time (ACT) levels drawn as per hospital policy. From this map, it appeared the earliest activation point was located in an area just under the aortic valve. During this stage in the procedure, a Biosense Webster bi-directional ThermoCool catheter D/F curve was utilized. (Figure 3)

Mapping points with this catheter were taken across the areas of interest. Without the need for the physician to leave the patient’s side to compare 12-lead EKG, the PaSo upgrade was able to give a correlation percentage between the pace map’s morphology and the arrhythmia morphology. The initial correlation showed an 88% morphology match. With recommendations from Chris Fillier, more pace maps were obtained to achieve a desired percentage of 95% or more before an ablation attempt would be made. The catheter was repositioned to obtain other pace maps (total of 28 pace maps) and a 99.3% correlation was found just under the aortic valve. (Figures 4 and 5)

At this specific area just under the aortic valve, the ablation application was applied at 35 watts and then repeated with 40 watts totaling 240 seconds. After these lesions were applied, repeat testing was performed with no initial VT induced. Isuprel was then initiated and vigorous stimulation performed again, and the arrhythmia could not be reinduced. After 30 minutes the procedure was terminated, all sheaths were removed, and the patient returned to the recovery area.

With no bleeding from puncture sites, no complaints of pain, and after an uneventful recovery period of five hours, the patient was discharged to home with family in the early evening. 

Conclusions

Porter Regional Hospital’s previous experiences of similar ablations had left the staff preparing for the potential of a lengthy case. The average case length from the time the patient entered the procedure room to the time of leaving was anywhere from four and a half hours to seven hours. 

The new PaSo technology demonstrated value in this initial case. The advantage of having the physician concentrate on the placement of the catheter rather than having to leave the procedure area to review each pace map showed instant appeal for this technology. The time it took to acquire the 28 pace maps and get a good representation of the target area was only 25 minutes. The optimal comparison percentage was acquired and only four minutes of lesions applied. This initial procedure only lasted three hours and the patient went home the same day.

The patient greatly benefited from this new technology by not being subjected to inappropriate ablation applications, experienced less radiation, received less anesthesia and was at reduced risk for pressure area breakdown. 

From a financial perspective, the patient required less nursing and facility time due to the reduced procedure time. There was a cost for the upgrade; however, Porter Regional Hospital acquired the software at no cost due to it being grandfathered with the Carto system purchase.

Consideration has to be made with regard to the MEM software update that Porter Regional Hospital received. The PaSo Module upgrade’s ability with the use of the DecaNav catheter to acquire multiple mapping points in a shortened amount of time was extremely valuable. In total, it took only 15 minutes to build an activation map composed of over 200 points. Looking forward, all signs appear favorable for the PaSo technology. The ability to instantly calculate the best morphology comparisons has initially shown not only benefits to the facility, but most importantly, to the patient. 

Disclosure: The authors report no conflicts of interest regarding the content herein.