Purpose: To determine whether the recently applied technique of acquisition-weighted 31 P-MR spectroscopy (AW-MRS) allows for the detection of depressed energy metabolism in patients with inferior wall myocardial infarctions.
Materials and Methods:Eight patients with subacute myocardial infarction and wall motion abnormalities restricted to the inferior wall were examined with a 1.5-T MR scanner. Global and regional left ventricular (LV) function was assessed by cine MRI, and the size and extent of myocardial infarction was assessed by late enhancement (LE). MRS was performed with an AW three-dimensional chemical shift imaging sequence. Phosphocreatine/ATP ratios were determined with the postprocessing model AMARES for four voxels positioned in the anterior, lateral, inferior, and septal parts of the LV.
Results:The LV ejection fraction (EF) was reduced to 37.5% Ϯ 9.0%. Seven of eight patients had transmural LE in the inferior wall, and one patient showed subendocardial enhancement in the inferior-lateral parts. Phosphocreatine/ATP ratios of the inferior wall were significantly reduced (P Ͻ 0.05) compared to all other parts of the LV (1.03 Ϯ 0.39 (inferior), 1.67 Ϯ 0.81 (lateral), 1.73 Ϯ 0.29 (anterior), and 1.49 Ϯ 0.31 (septal)). The ratios in five of seven patients with transmural enhancement were Ͻ1.00 in the inferior wall. BECAUSE OF THE INTRINSIC technical limitations of phosphorous spectroscopy, 31 P-MR spectra in the human heart are generally acquired only from anteroseptal portions of the human heart (1,2). The main reason for this is that phosphorous has an inherently low signal-to-noise ratio (SNR), which necessitates the use of sophisticated localization techniques. Consequently, only large single volumes (voxels) can be analyzed in a nondiscriminating manner. Accordingly, previous MR spectroscopy (MRS) studies were restricted to the analysis of anteroseptal regions (3,4) or anterior wall myocardial infarctions in patients with coronary artery disease (5). With the advent of multivoxel techniques, such as chemical shift imaging (6), it has become feasible to study different regions of the left ventricle (LV) separately. However, previous studies were restricted to anterior and septal parts of the LV (7,8). Recent studies analyzed four regions of the LV, including the lateral and inferior wall, in healthy volunteers using acquisition weighting (9,10).The aim of the present study was to determine whether acquisition weighting can overcome one important limitation of current clinical applications of MRS: analysis is restricted to anteroseptal regions of the heart in patients with myocardial infarctions. Toward that end, we examined patients with myocardial infarctions of the inferior wall.
MATERIALS AND METHODS
Patients and Study DesignEight male patients (52-77 years old, mean age ϭ 64.0 Ϯ 8.9 years) with electrocardiographically and enzymatically proven myocardial infarctions were included in the study. The patients were selected according to indications of wall motion abnormalities restricted to the i...