# Magnetocardiography for noninvasive surveillance of rejection and cardiac allograft vasculopathy in heart transplant recipients

## TL;DR

Magnetocardiography (MCG) is a noninvasive tool that may help detect heart transplant complications like rejection and vasculopathy earlier than current methods.

## Contribution

This review synthesizes evidence on MCG's potential for post-transplant surveillance and outlines barriers to its adoption.

## Key findings

- MCG detects electrophysiologic changes linked to rejection and CAV before traditional methods confirm them.
- Rejection correlates with dipole strength and repolarization heterogeneity, while CAV relates to QTc and Magnetic Dispersion Velocity.
- MCG remains underutilized due to small studies, lack of standardization, and limited equipment availability.

## Abstract

Heart transplantation is the definitive treatment for end-stage heart failure, yet long-term graft survival is hindered by two major complications: acute/chronic rejection (cellular or antibody mediated) and cardiac allograft vasculopathy (CAV). Standard surveillance is performed to screen for these issues and predominantly consists of cardiac catheterization with hemodynamics, endomyocardial biopsy and invasive coronary angiography, with intravascular ultrasound (IVUS) and coronary flow reserve. The use of IVUS increases the sensitivity for CAV detection. Overall, these procedures have associated morbidities, need anesthesia and have associated patient discomfort and substantial cost. Magnetocardiography (MCG), a noninvasive modality that measures cardiac magnetic fields, has emerged as a potential tool for early detection of complications in post-transplant patients. Unlike electrocardiography, MCG provides spatially resolved data on depolarization and repolarization, independent of body habitus or tissue conductivity. Early studies suggest that MCG can identify electrophysiologic abnormalities associated with both acute rejection and CAV, in some cases preceding histologic or angiographic confirmation. Rejection is reflected by alterations in magnetic dipole strength and repolarization heterogeneity, while CAV correlates with repolarization dispersion indices such as QTc heterogeneity and Magnetic Dispersion Velocity. Despite promising pilot data, MCG remains underutilized, largely due to small study sizes, lack of standardized interpretation, and limited availability of equipment. This review synthesizes the existing evidence, highlights potential advantages and limitations, and outlines future directions for integrating MCG into standard post-transplant surveillance protocols.