Assessment of left ventricular function and mass in patients undergoing Computed Tomography (CT) coronary angiography using 64-detector-row CT: Comparison to magnetic resonance imaging

Purpose: To quantify left ventricular function and mass derived from retrospectively ECG-gated 64-detector-row computed tomography coronary angiography data sets in comparison to cine magnetic resonance (MR) imaging as the reference standard. We hypothesized that the administration of beta-blockers prior to multidetector computed tomography (MDCT) coronary angiography has a significant impact on left ventricular functional parameters. Material and Methods: Multiplanar reformations in the short-axis orientation were calculated from axial contrast-enhanced CT images in 21 patients (16 male, five female; age range 41-75 years, mean 64.3±6.8 years) referred for CT coronary angiography. Patients whose heart rates exceeded 60bpm received 5mg bisoprolol orally 1 hour before the MDCT examination. In case of insufficient heart-rate reduction, up to four vials (20mg) of metoprolol were injected intravenously. The end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), cardiac output (CO), and left ventricular mass (LVM) of the reformatted images were analyzed compared to volumetric measurements based on continuous short-axis steady-state free-precession cine MR sequences (TR 3ms, TE 1.5ms, FA 60°). Results: On average, each patient received 15.5mg metoprolol (range 0-20mg) and 3.85mg bisoprolol (range 0-5mg). The mean heart rate was 56±5bpm during CT and 73±9bpm during MRI examination. This difference was statistically significant (P<0.05). Mean EDV and ESV measured on MDCT were significantly higher compared to MR (MDCT vs. MR: EDV 164.2±52.5 vs. 144.2±46.7ml, ESV 77.3±46.6 vs. 63.8±47.3ml; P<0.05). Mean EF and CO derived from MDCT images were significantly lower compared to MR (MDCT vs. MR: EF 55.4±11.8 vs. 59.3±15.4%, CO 4822±779 vs. 5755±1267ml; P<0.05). Mean SV and LVM were not significantly different between both methods (MDCT vs. MR: SV 86.8±18.1 vs. 80.3±15.6ml, P = 0.44; LVM 132.4±42.5 vs. 138.7±39.1g, P = 0.31). Conclusion: Left ventricular volumes assessed by the newest-generation MDCT scanners are significantly higher compared with MRI, whereas ejection fraction and cardiac output are significantly lower in MDCT. This appears to be a result of the frequent application of beta-blockers prior to MDCT examinations.