Recently, myocardial perfusion using MRI has become a promising non-invasive method to evaluate myocardial ischemia in cardiovascular diseases (CVDs).^1,2 However, assessment of CMR's effectiveness in differentiating quantitative metrics of regional myocardial perfusion in patients with CVD and comparison of regional myocardial perfusion indices to cardiac global functional parameters has not been thoroughly studied. To address this unmet clinical need, we evaluated myocardial perfusion and cardiac function in 12 healthy volunteers and 9 cardiac transplant patients.

12 healthy volunteers (10 males, mean age 52+/-17 years old, body weight: 93+/-20 kg) without documented history of CVDs and 9 cardiac transplant patients were recruited following IRB approval and written informed consent. MRI scans were performed at 1.5 T systems (Magnetom Aera, Siemens Medical Solutions, Erlangen, Germany). Each volunteer and patient underwent a cardiac MRI enclosing first pass perfusion imaging after injection of Gd contrast agent and short axis CINE SSFP imaging for the assessment of global cardiac function.

Perfusion images were acquired in left ventricular (LV) short axis orientation with three slices positioned at basal, mid-chamber, and apical location after the injection of a single dose of gadopentetate dimeglumine (Magnevist, 0.1 ml/kg). Perfusion date reconstruction included inline and fully automated motion correction to compensate for the effects of cardiac and respiratory motion. Perfusion Imaging parameters were as follows: FOV = 360 x 360 mm², Slice thickness = 8mm, TR/TE/flip angle = 168/1.14ms/12degree. Measurements = 60

All CINE data were transferred to a computer (Siemens Leonardo Syngo) for analysis using ARGUS software. A single reviewer semi-automatically drew the borders (endo and epi-cardial) of the LV at each slice for each study and global cardiac function parameters were calculated.

Cardiac global functional parameters including absolute EF, absolute and normalized EDV, absolute and normalized ESV, absolute and normalized SV, absolute CO, and normalized CI were measured based on short-axis cine images. Perfusion data analysis include LV contour segmentation, and calculation of peak perfusion signal intensity, peak slope of the signal change, and time to peak perfusion (TTP). Perfusion data were evaluated in myocardial segments based on the AHA 16-segment model.

Differences in perfusion on a segmental and global level were assessed between volunteers and patients using an unpaired two-tailed t-test. In addition, differences in global functional parameters were assessed between volunteers and patients using an unpaired two-tailed t-test. Finally, correlation between perfusion and global functional parameters was assessed by using Pearson correlation coefficient (r) for volunteers and cardiac transplant patients.

The results for t-tests assessing differences between volunteers and patients for perfusion, slope, and time to peak perfusion are shown in Table 1. The most significant differences were seen in the perfusion parameter, with 7 of the 16 segments showing significant differences between patients and controls. However, few significant differences were seen in slope and time to peak perfusion parameters. The average perfusion (averaged over entire LV) for volunteers and patients is shown in Table 2 and was significantly different between controls and patients (85.27 +/- 19.6, 63.07 +/-14.07, p =0.016). The results for differences in cardiac global functional parameters between volunteers and controls as well as the results for correlation between functional parameters and perfusion are shown in Table 3. No significant differences were seen in functional parameters between volunteers and patients. No significant relationships between perfusion and global functional cardiac parameters were found except normalized SV (0.508, p=0.039).Cardiac MR detected significant differences in regional myocardial perfusion indices between healthy volunteers and recipients of cardiac transplantation, as evidenced by the significant differences measured in segmental and average perfusion. The absence of significant correlations of perfusion with cardiac functional parameters indicates that metrics of myocardial perfusion may be more sensitive to detect early changes in LV dysfunction prior to the onset of impairment in global cardiac function. Additional studies in larger cohorts are warranted to further evaluate relationships among various cardiac indices.