This study aims to provide reliable patient monitoring inside the MRI, and improve cardiac MRI imaging of arrhythmia patients. ECGs within the MRI are overlaid with a Magneto-Hydro-Dynamics (MHD) voltage (VMHD), so S-T segment elevation during ischemia cannot be determined. In addition, cardiac MRI of arrhythmia patients is blurred due to non-robust synchronization to the R-wave. We will develop an MR-safe 12-lead Electro-Cardio-Gram (ECG) system, permitting ECG acquisition during cardiac MR imaging. We will extract the real ECG signals (ECGreal) from the MHD-contaminated ECGs, allowing for reliable patient monitoring. The extracted clean ECGreal will be sent to the MRI for selective cardiac gating based on PVC/Sinus Rhythm (SR) beats. The separated MHD signals (VMHD) will be used for a non- invasive estimation of systolic beat-to-beat cardiac stroke volume (SV.
Aim #1 : MR compatible 12-lead ECG acquisition system We will develop an MR compatible ECG acquisition system in which the recorded 12-lead ECG signals are not distorted or masked by induced MR gradient and Radio Frequency (RF) pulses in 3 Tesla MRI scanners. Reduction of noise during MRI-gradient rise/fall will be removed via a novel electronic switching-circuit that cuts off ECG transmission to the ECG amplifier during gradient ramps and also during RF-pulse transmission. The system will also meet the FDA patient heating limits during MRI imaging.
Aim #2 : Real-time ECG processing for MHD signal filtering We will develop a real-time adaptive filtering procedure to extract ECGreal and VMHD from 12-lead ECGs. This software will provide diagnostic quality ECGs and deliver a non-invasive estimation of SV, computed from the systolic-integrated VMHD. We will develop a real-time PVC/SR beat classification method based on a novel 3-D representation of 12-lead ECG data. Scan triggering and image data can then be utilized according to the current beat type present, for use in triggering cardiac MRI. To test the system functionality, acute arrhythmia will be created in a swine model.
Aim # 3: Improved Cardiac MRI imaging in Arrhythmia patients We will evaluate the hardware and software developed in Aims 2 and 3 in a cohort of 10 Idiopathic Outflow Tract (IOT) PVC patients. Conventional ECG-gated scans will be performed, comparing the new platform to the commercial 4-lead ECG systems used today. Image spatial resolution and acquisition times will be compared. In severe (>20% PVC/SR beats) IOT PVC patients, selective imaging during PVCs will be attempted, possibly providing unique insight on heart motion during PVCs.
This project addresses the difficulty to obtain artifact-free Electro-cardiogram (ECGs) traces in high-field MRI. High- fidelity 12-lead ECGs are required for patient physiological monitoring, and can improve MRI-scan synchronization. Major artifacts are MRI gradient ramps [1], and Magneto-Hydro-Dynamic (MHD) voltages, which masks acute-ischemia monitoring [2]. We will develop a clinical 12-lead ECG [3-6] that operates safely at 3T, and use it in arrhythmia patients.
