Noninvasive monitoring of cardiac allograft vasculopathy with fast MR imaging

Cardiac allograft vasculopathy (CAV), also known as chronicle rejection, is a leading cause of graft (foreign heart) loss and death in patients who survive the first year after heart transplantation. The typical pathological change of CAV is gradually thickening of coronary wall in "foreign" heart due to continuous immunological reaction between donated heart and the host. In some cases, undetected CAV may silently cause graft failure with global myocardial ischemia without any documented infarction signs. Thus, continually monitoring development of asymptomatic CAV is important for selecting prophylactic strategies to get better prognosis. However, most current examinations of detecting CAV are invasive and with certain risks.

A new study done by researchers at Northwestern University Feinberg School of Medicine indicates that Magnetic Resonance (MR) Imaging may be a promising candidate for directly imaging pathological changes of allograft. 

"There is a main technical barrier. Recipients of heart transplantation usually have heart rates much faster than healthy individuals because of denervation or sub-normal re-innervation of the donor (foreign) heart. Unfortunately, traditional MRI technique is very sensitive to cardiac motion, which is positively related to heart rates. Furthermore, long term effect of lowering heart rate on such patients is still unknown. Therefore, most patients with heart transplant would have been ruled out of this examination. In this study, we developed and apply a fast MR imaging technique (Steady state free procession). We expected that this technique will break the traditional threshold of heart rate and greatly improve image quality under conditions of fast heart beat and may be further used in clinically detecting CAV. " said Debiao Li, PhD, Professor of Radiology, Northwestern University, Chicago, a major developer of the advanced MR technique.

"Currently, more than 2200 heart transplants occur each year in the United States. We have tested the feasibility of this promising technique and got some nice images on recipients of heart transplantation. The preliminary results are encouraging. Those pictures allows us to find subtle morphologic changes on coronary wall, the early sign of CAV, at almost no extra risk to patients" said Kai Lin, MD, MS, Northwestern University, Chicago, the principle investigator of this study. "Currently, we are recruiting more patients with heart transplant to test clinical impaction of this new clinical application. We believe it will finally improve survival and live quality of recipients of heart transplantation. "

"In theory, Steady-State Free Precession is not a new concept of MR imaging. It has already been used in imaging aorta and carotid artery. However, we are the first group to use it in detecting CAV. We believe that we have applied a cutting-edge technical development where it is needed most. The ultimate beneficiaries of the “win-win situation” are patients."

The study is supported by American Heart Association Clinical Research Grant. Dr. Kai Lin will present the preliminary result on Scientific Session 2010 of American Heart Association as a finalist of Melvin Judkins Young Investigator Award, a world renowned prize named for the pioneer of coronary angiography.

Scientific session to be held at the American Heart Association (Nov 2010, Chicago, IL). (http://e.ctt.bz/e.asp?e=347531C8-E4FD-4A60-825A-37E8F48FD192)