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AF Symposium 2020

“Virtual Heart” Assists Actual Ablations

by Steve S. Ryan

We have previously described the innovate, exciting work of Prof. Natalia Trayanova of Johns Hopkins Un. in Baltimore, MD. See ‘3D Virtual Heart’ Predicts Location of Rotors (2017 AF Symposium) and The Virtual Heart Computerized Simulation (2015 AF Symposium).

N. Trayanova, MD

At the 2020 AF Symposium, Prof. Natalia Trayanova of Johns Hopkins University presented “Computationally Guided Personalized Targeted Ablation for Persistent AF.” This computerized model is used to simulate an individual patient’s heart. This ‘Virtual Heart’ can then be used to guide an individual patient’s therapy.

Significant for Persistent A-Fib: For patients with Persistent Atrial Fibrillation, this computerized model is especially important. In a simple case of A-Fib, ablating/isolating the Pulmonary Veins (PVs) is usually all that’s necessary to restore a patient to sinus.

But with persistent A-Fib, it’s frequently required to do more than isolate the PVs. Persistent A-Fib patients often have fibrosis (fibrotic substrate) which perpetuates re-circulating electrical waves (rotors). The Virtual Heart identifies these fibrotic areas which sustain A-Fib.

How the Virtual Heart Works

Dr. Trayanova and her team start by doing an MRI scan. Then they hyper-enhance segments which correspond to areas of fibrotic remodeling in a patient’s heart.

The next step is to develop a computational mesh that incorporates representations of ion channels, calcium cycling and other electrophysical aspects of an individual’s atria. All this is incorporated into patient-specific geometry of the model.

Virtual-Heart-OPTIMA-approach-flowchart.

What the Model Can Reveal: They run the model to see what the arrhythmia looks like.

• Does the fibrotic substrate anchor rotors in particular locations?
• What are the spatial characteristics of the regions where they are located?
• Can these spatial metrics guide where the proper ablation should be?
• Can we reliably predetermine ablation targets?

Dr. Trayanova’s team merges these virtual atria with an advanced imaging technology (CARTO 3 System) to predict where the catheter should ablate.

The “Virtual Heart” Identifies Rotors: Prof. Trayanova found that re-entrant drivers (rotors) persisted in areas of higher fibrosis density and entropy (lack of order or predictability). They didn’t persist in regions of non-fibrotic sites and regions of deep fibrosis. The Virtual Heart is designed to completely eliminate the ability of the fibrotic substrate to sustain A-Fib.

Dr. Trayanova compared the predictive ability of her models to actual ECGI mapping cases from the Bordeaux group. Overall, her prediction of where rotors would be found coincided with where rotors were actually found by ECGI.

First-In-Human Virtual Ablation

Dr. Trayanova made major news when she announced the first-in-human clinical study of her Virtual Heart system! The first ten patients were part of an FDA approved clinical study of 160 persistent A-Fib patients called OPTIMA―Optimal Target Identification via Models of Arrhythmogenesis.

These ten patients had MRI heart scans which showed the fibrosis/scarring in their hearts.

This is a personalized approach tailored for each patient. The amount and structure of fibrosis is different in each individual.

Schematic summarizing the process of importing OPTIMA ablation targets into CARTO.

Creating Digital 3-D Models: Dr. Trayanova and colleagues then created digital 3-D models (Carto) and duplicated digitally the substrate and areas of fibrosis in individual patients.

They filled this model with digital virtual heart cells which mimicked and became a computerized duplicate heart. This digital heart behaved just like that individual patient’s real heart.

This digital heart behaved just like that individual patient’s real heart.

Then, they stimulate/pace the virtual heart electrically in many different locations to see where a stimulus produces an irregular heartbeat or rotor.

Rounds of Virtual Ablation: At this point, they performed several rounds of virtual ablation to digitally ablate those areas. Again, they tested to see if the digital ablation scars generated sites of emergent activity.

By the third round, there are no more hidden areas that can cause abnormal electrical signals. “We repeat the process till the substrate is no longer inducible for AF.” This also targets latent atrial arrhythmias, such as those that might emerge following initial ablation.

The Patient’s Digital Model: Finally, they export the digital model of the patient’s heart with all the A-Fib sites/rotors marked for the EP doing the actual ablation. In the EP lab, the EP uses this map to guide the catheter to the areas that need to be ablated.

Success of First Ten Patients

Persistent A-Fib patients, in general, are the most difficult to return to normal sinus rhythm. Around 50% of these patients have recurrences and have to return for additional ablations (which often cause yet more scar tissue).

Of Dr. Trayanova’s first 10 persistent patients in the OPTIMA procedure, only one patient had to return for a Flutter ablation (this was mostly because they ran out of time during the first ablation). In particular, all the rotor sites were correctly identified and ablated.

Editor’s Comments:

Persistent A-Fib patients are perhaps the most difficult to make A-Fib free.
Today, it’s common for even the best Master EPs to bring back persistent A-Fib patients for a second and even a third ablation before restoring them to sinus.
This may change with deployment of the Virtual Heart system.
The Virtual Heart system extensively and repeatedly maps where all A-Fib signals are coming from in a particular patient’s heart. With this mapping, the EP knows exactly where to ablate, including “hidden” areas which could emerge after a preliminary ablation, and areas that would cause electrical misfiring in the future.
Very important, with the Virtual Heart ablation there is no or very little recurrence of A-Fib.
The Virtual Heart system represents a major breakthrough in the treatment of persistent A-Fib patients.
The potential of Dr. Trayanova’ s research for A-Fib patients is incredible!
Imagine getting an MRI and knowing where your A-Fib is coming from, how your A-Fib affects and works in your heart both now and in the predictive future, how various A-Fib drugs can be expected and predicted to affect your heart, how much and what kind of fibrosis you have, how you can expect your fibrosis to progress and affect you over time, what therapies should be done in your particular case.
Imagine…if you need a catheter ablation, your EP knows exactly where to ablate in your heart.
Imagine…being able to accurately predict whether or not or how fast you will progress from paroxysmal to persistent A-Fib.
Imagine…all based on computer models that mirror your own heart.

Dr. Trayanova’s research has the potential to radically change the way A-Fib is treated. Almost all the uncertainties EPs and A-Fib patients now have to deal with can potentially be eliminated with the virtual computer reconstruction of individual A-Fib hearts.

References
Trayanova, N. A. Custom Cardiology: A Virtual Heart for Every Patient; Personalized computer models will let cardiologists test life-saving interventions. IEEE online, 28 Oct 2014. Accessed Feb 26, 2015, URL: http://www.ieee.org/about/index.html

Scudellari, Megan. Personalized Virtual Hearts Could Improve Cardiac Surgery―Digital replicas of patients’ hearts can identify hidden, irregular heart tissue for surgeons to destroy. IEEE Spectrum, August 22, 2019 / 12:00 GMT https://spectrum.ieee.org/the-human-os/biomedical/imaging/virtual-hearts-improve-cardiac-surgery

If you find any errors on this page, email us. Y Last updated: Wednesday, August 26, 2020

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