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CMR of Heart Transplant Complications

Non-invasive Imaging: Magnetic Resonance Imaging

This pre-lunch session included five experts who discussed the role of cardiac MRI in the assessment of cardiac rejection in transplanted patients. 

James Carr, MD (Northwestern University) began the session with an excellent overview of the challenges involved with transplant medicine.  Specifically, he discussed the impact that acute and chronic rejection surveillance has on the morbidity of this disease process.  Surveillance biopsies can occur up to 16 times per year in a single individual with a gross annual cost of over $450 million.  Complications such as developing a right bundle branch block, tricuspid regurgitation, coronary fistulas and myocardial scar formation are rare but still a possibility in <1% of those undergoing right ventricular biopsy.  Cardiac MRI can play a role here with reducing both the morbidity and cost of frequent surveillance (8 times reduction in cost).

Pierre-Yves Marie, MD (Centre Hospitalier Universitaire de Nancy) followed with the T1 and T2 assessment in cardiac transplant rejection.  He noted that black blood T2 imaging correlated better than T1 with rates of rejection and also improved with anti-rejection therapies.  An abnormally high T2 signal >65 msec was associated with a 4 times increased relative risk of rejection over those with a T2 signal <55 msec.  He noted that a national trail entitled the DRAGET trial, designed to assess the impact of T2 imaging on rejection, recently began enrollment with plans for completion in 2017.

Monique Bernard, PhD (CEMEREM) addressed the role of 31-Phosperous MR-spectroscopy in assessing the suitability of the donor heart.  31-P is a marker of basic metabolic activity of the cell and can be used to determine both graft viability and vasculopathy.  In vitro, the donor heart is assessed prior to transplant, in an ice chest, with a brief scan that can take up to 30 minutes.  This procedure is sometimes performed in grafts from marginal donors, grafts being considered for discard or grafts that require rehabilitation prior to implant.  The reported sensitivity and specificity for detection of vasculopathy is up to 100% and 70%, respectively.

Transplant vasculopathy can alternatively be evaluated by CMR perfusion.  This was discussed in detail by Chris Miller, MBChB (University Hospital of South Manchester).  Vasculopathy can present as either epicardial stenosis and/or microvascular obstruction.  Dr. Miller discussed the role of myocardial perfusion reserve with semi-quantitative assessment of the changes in signal intensity over time during a perfusion sequence utilising a gadolinium contrast agent.  Reduction of the myocardial perfusion reserve is associated with both microvascular and epicardial disease and worsening outcomes (death, MI, PCI) in the cardiac transplant patient.

Rene Botnar, PhD (King’s College London/St. Thomas Hospital) concluded the session addressing coronary wall imaging in transplant vasculopathy.  He noted that coronary imaging by CMR is best performed with a self-navigator technique.  He gave examples of coronary haemorrhage and coronary delayed enhancement and discussed their association with coronary artery vasculopathy (CAV).  He went on to note that this coronary enhancement is associated with coronary plaques as noted on intravascular ultrasound.  An increased diameter of the enhanced portion of the coronary vessel was also associated with an increased grade and worsening degree of CAV.  In addition, he discussed the upcoming role of molecular imaging in CAV including elastin imaging using elastin-specific contrast agents.
The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.