Utility of cardiac magnetic resonance imaging for the diagnosis of heart transplant rejection

Objectives. To assess the value of the use of cardiac MRI to detect rejection (necrosis) and its ability to discriminate it from other pathologic alterations (edema and fibrosis). Materials and methods. A prospective and consecutive study was designed in which cardiac MRI was performed at the same time as the scheduled endomyocardial biopsy. The study period was from 31-10-01 to 01-05-02. Ten patients with claustrophobia were excluded. Sixty-four examinations were performed in the remaining 40 patients. MRI assessment was blinded to the biopsy result. The 17 biopsies performed were insufficient (too small sample). Rejection was defined as the presence of at least 1 focus of myocyte necrosis. Technique. A high-field (1.5 T) GE CV/i magnetic resonance imaging system was used to obtain pre- and postcontrast white and black blood anatomic sequences (breath-hold fast spin-echo T1-weighted images), as well as myocardial cine, perfusion and viability sequences. Variables analyzed. Ejection fraction, ventricular volumes, pericardial effusion, hypertrophy, absolute and relative myocardial intensity and uptake. Statistics. Variables were normally distributed. Student's t test was used for quantitative variables and the X-2 test for proportions. Results. Mean age, 51 +/- 13 years. Women 5, men 35. Time since HT, 13 to 3725 days. No significant differences were found between rejection and ventricular volumes or the presence of effusion and hypertrophy. Visual estimation of myocardial perfusion and viability sequences did not detect any significant changes. Uptake showed a clear trend to increase in patients with necrosis: 34 +/- 21 versus 23 +/- 17 for relative uptake, P < .05. There were also differences in uptake when fibrosis was present: 68 +/- 47 versus 102 +/- 48 in the group without fibrosis, P < .05; but not in the presence of edema: 93 +/- 55 versus 94 +/- 45 for absolute uptake. Conclusions. (1) Cardiac MRI is a promising technique for diagnosis of rejection. (2) Patients with myocyte necrosis show a clear trend toward increased myocardial uptake. (3) Interstitial fibrosis is associated with decreased levels of uptake.