Knowledge Vault 3/31 - G.TEC BCI & Neurotechnology Spring School 2024 - Day 3
Noninvasive in-vivo whole heart electrophysiological mapping
Gaby Captur, University College London (UK)
<Resume Image >

Concept Graph & Resume using Claude 3 Opus | Chat GPT4 | Llama 3:

graph LR classDef noninvasive fill:#f9d4d4, font-weight:bold, font-size:14px; classDef vest fill:#d4f9d4, font-weight:bold, font-size:14px; classDef ecgi fill:#d4d4f9, font-weight:bold, font-size:14px; classDef clinical fill:#f9f9d4, font-weight:bold, font-size:14px; classDef limitations fill:#f9d4f9, font-weight:bold, font-size:14px; A[Gaby Captur] --> B[Non-invasive physiological mapping system
alongside CMR. 1] A --> C[Electrophysiological mapping: electrical wavefronts,
arrhythmia-linked deranged electrophysiology. 2] A --> D[Invasive methods robust but
not scalable. 3] A --> E[ECGI: high-resolution ECGs,
inverse solution algorithm. 4] A --> F[Vest links cardiac MRI,
personalized electrophysiological map. 5] F --> G[Cardiac MRI: myocardial health,
mechanics, scar. 6] F --> H[Vest: textile electrodes,
dry electrodes. 7] H --> I[Quick recording, high throughput. 8] F --> J[Co-registering electrodes: 'mirror vest',
synthetic approach. 9] F --> K[Excellent ECG quality,
ground electrode. 10] F --> L[Anatomical CMR: high-resolution
transaxial HASTE stack. 11] F --> M[Signal averaging, segmentation
using MATLAB. 12] F --> N[Inverse solution algorithm:
1000-node epicardial maps. 13] F --> O[Unipolar electrograms: activation time,
repolarization time, ARI. 14] O --> P[ARI mirrors action potential,
changes in disease. 15] F --> Q[Good test-retest reproducibility. 16] A --> R[1946 British birth
cohort study. 17] R --> S[Cardiac amyloidosis: early
disease mechanism insights. 18] R --> T[Hypertrophic cardiomyopathy: risk
stratification, subclinical disease. 19] R --> U[Arrhythmogenic cardiomyopathy: abnormal
signatures, scar correlation. 20] A --> V[4D electromechanical models:
arrhythmia, sudden death risk. 21] A --> W[Limitations: costs, validation,
inverse solution challenges. 22] A --> X[Reusable vest vs
Medtronic's single-use vest. 23] A --> Y[Complete chest coverage
for inverse solution. 24] A --> Z[ECGI vs EEG/MEG:
heart distance, structures. 25] A --> AA[One-size vest, adjustable,
pediatric version planned. 26] AA --> AB[G-Sahara electrodes: good
contact, reliability. 27] A --> AC[Medtronic's single-use vest:
environmental sustainability concerns. 28] A --> AD[No neighboring organ
artifacts, motion denoising. 29] A --> AE[800+ patients, large-scale
potential with validation. 30] class B,C,D noninvasive; class F,G,H,I,J,K,L,M,N,O,P,Q,AA,AB,AC vest; class E,Y,Z ecgi; class R,S,T,U,V clinical; class W,AD limitations;


1.-Dr. Gabby discussed developing a non-invasive in vivo whole physiological mapping system to work alongside cardiovascular magnetic resonance (CMR) imaging.

2.-Electrophysiological mapping looks at electrical wavefronts traveling across the beating heart to identify deranged electrophysiology linked to arrhythmias.

3.-Current invasive electrophysiological mapping methods like electrode socks and catheters provide robust data but are not feasible for large-scale use.

4.-Electrocardiographic imaging (ECGI) collects high-resolution ECGs from the chest surface and uses an inverse solution algorithm to generate epicardial maps.

5.-Dr. Gabby's group developed a vest to link the rich cardiac MRI data with the patient's personalized electrophysiological map.

6.-Cardiac MRI provides detailed non-invasive information about myocardial substrate health, mechanics, perfusion, scar, and more without radiation.

7.-Initial vest prototypes used embroidered textile electrodes. The current version uses GTEC G-Sahara dry electrodes that don't require shaving.

8.-The vest recording takes 5 minutes, and donning/doffing the vest is quick, enabling high throughput. Over 800 patients have used it.

9.-Co-registering electrode positions originally used a "mirror vest" with MRI markers. A new synthetic approach just requires corner markers.

10.-The vest provides excellent quality ECG data across 256 channels. A ground electrode over the right shoulder improves results.

11.-Anatomical CMR data is collected using a high-resolution transaxial HASTE stack covering the entire torso.

12.-Signal averaging of the ECG data is done using in-house MATLAB code. Heart segmentation is currently manual but automating it is planned.

13.-Professor Rudy's extensively validated inverse solution algorithm is used to generate 1000-node epicardial maps, except for the septum.

14.-Unipolar electrograms allow extracting activation time, repolarization time, and activation recovery interval (ARI) as key electrophysiological biomarkers.

15.-ARI mirrors action potential duration. Changes in ARI are more pronounced in diseased myocardium.

16.-The vest and analysis pipelines have demonstrated good test-retest reproducibility, a key requirement for clinical use.

17.-The vest was used to study electrophysiological profiles in 500 participants aged 70+ from the famous 1946 British birth cohort.

18.-Another study of cardiac amyloidosis patients showed ECGI provides earlier insights into disease mechanisms compared to 12-lead ECG.

19.-In hypertrophic cardiomyopathy, ECGI distinguished high vs low sudden cardiac death risk and identified subclinical disease missed by ECG.

20.-In arrhythmogenic cardiomyopathy, abnormal ECGI signatures correlated with areas of scar. More work is needed on risk stratification.

21.-Dr. Gabby's group is using ECGI and CMR to develop 4D electromechanical heart models to predict arrhythmia and sudden death risk.

22.-Limitations of ECGI include upfront equipment costs, some remaining need for clinical validation, and challenges with the inverse solution.

23.-Compared to Medtronic's single-use ECGI vest for CT, their reusable vest is more cost-effective and works with MRI.

24.-Electrodes are placed across the entire chest because heart position varies and complete coverage is needed for the inverse solution.

25.-The ECGI inverse problem is similar to EEG/MEG but complicated by the heart's greater distance from electrodes and intervening structures.

26.-The one-size vest fits most adults, with adjustable Velcro straps. A pediatric version is planned. Obese patients are usually excluded.

27.-G-Sahara electrodes make good skin contact even with chest hair, eliminating the need for shaving. Their large surface helps reliability.

28.-Medtronic's vest is single-use because washing would damage the inbuilt electronics. This raises environmental sustainability concerns.

29.-No artifacts from neighboring organs affect the ECGI, but motion artifacts during exercise recordings require denoising.

30.-With over 800 patients recorded, the vest enables large-scale studies and has potential for clinical translation with further validation.

Knowledge Vault built byDavid Vivancos 2024