A medical imaging technique to measure the magnetic fields produced by the heart’s electrical activity using extremely sensitive devices.
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MCG has demonstrated the potential to identify myocardial regions with compromised electric activity at rest in multiple studies in the past. It is theorized that this is possible due to MCG displaying significantly greater spatial resolution compared to ECG, where MCG is so sensitive to changes in the heart’s magnetic field that it can identify ischemic tissue or tissue predisposed to ischemia.
Stress-based MCG should theoretically offer enhanced detection of inducible ischemia in patients by giving physicians the ability to compare the heart’s magnetic field at rest versus during a controlled period of stress. Further research is needed to validate applications where stress-based MCG offers additional diagnostic value over rest-based MCG.
In contrast with ECG (which records electrical voltages across the skin to measure cardiac electrophysiology), MCG aims to measure cardiac electrophysiology by measuring the magnetic fields generated by the heart’s electrical pacemaking activity but does so without making physical contact with the patient (i.e. MCG is a contactless modality).
One of the major advantages of MCG over ECG is that unlike the electrical currents measured by ECG, magnetic fields are undistorted as they travel through tissue. MCG is also sensitive to tangential and vortex currents that are undetected by ECG.
MCG’s significantly increased resolution in mapping cardiac activity means MCG can be sensitive to conditions that are not easily detected in a clinically scalable way by ECG.
MCG is most easily understood as a functional imaging test, and not as an anatomic one, as it does not directly image any coronary arteries. Early data suggests that visual changes in the Magnetic Field Map of a patient may be associated with stenosis location and could be used to infer the location of an obstructed coronary artery or arteries. However, research into a proper clinical application for localization is currently ongoing.
Because of MCG’s demonstrated sensitivity to ischemia across multiple studies, MCG has clear potential as an efficient, high-throughput tool for initial ACS risk stratification and then further determination of the need for additional downstream testing. In the ED environment, where unit economics are most acutely felt, MCG could represent a significant source of cost-savings for the management of suspected ACS patients.
In outpatient scenarios, MCG could easily assess patients presenting with new onset chest pain (or similar symptoms), meaning it could be used for both risk stratification of angina as well as serial monitoring of changes in cardiac function over time.
Beyond the detection of ischemia across all forms and presentations of Ischemic Heart Disease, MCG has shown significantly unique potential for diagnosing arrhythmias, cardiomyopathies, and other congenital heart diseases.
Because the test effectively places zero burden – radiation or otherwise – on a patient, MCG could also be deployed as a rapid, serial scan intended to track chronic disease progressions and measure patient response to treatment uptake.
While MCG has clearly demonstrated diagnostic utility in each of these patient populations separately, additional research still needs to be done to determine if a single MCG scan can effectively distinguish between the two forms without the need for additional information.
The most recent study into MCG’s sensitivity to microvascular dysfunction, Genetesis’s own MICRO trial, produced great proof-of-concept data that MCG can be used to rule-in CMD in patients with angina once obstructive coronary artery disease has been ruled out (via CCTA or invasive angiography).