Assessment of Left Ventricular Ejection Fraction Calculation on Long-axis Views From Cardiac Magnetic Resonance Imaging in Patients With Acute Myocardial Infarction

To assess left ventricular ejection fraction (LVEF) accurately, cardiac magnetic resonance (CMR) can be indicated and lays on the evaluation of multiple slices of the left ventricle in short axis (CMR(SAX)). The objective of this study was to assess another method consisting of the evaluation of 2 long-axis slices (CMR(LAX)) for LVEF determination in acute myocardial infarction. One hundred patients underwent CMR 2 to 4 days after acute myocardial infarction. LVEF was computed by the area-length method on horizontal and vertical CMR(LAX) images. Those results were compared to reference values obtained on contiguous CMR(SAX) images in one hand, and to values obtained from transthoracic echocardiography (TTE) in the other hand. For CMR(SAX) and TTE, LVEF was computed with Simpson method. Reproducibility of LVEF measurements was additionally determined. The accuracy of volume measurements was assessed against reference aortic stroke volumes obtained by phase-contrast MR imaging. LVEF from CMR(LAX) had a mean value of 47 ± 8% and were on average 5% higher than reference LVEF from CMR(SAX) (42 ± 8%), closer to routine values from TTE(LAX) (49 ± 8%), much better correlated with the reference LVEF from CMR(SAX) (R = 0.88) than that from TTE (R = 0.58), obtained with a higher reproducibility than with the 2 other techniques (% of interobserver variability: CMR(LAX) 5%, CMR(SAX) 11%, and TTE 13%), and obtained with 4-fold lower recording and calculation times than for CMR(SAX). Apart from this, CMR(LAX) stroke volume was well correlated with phase-contrast values (R = 0.81). In patients with predominantly regional contractility abnormalities, the determination of LVEF by CMR(LAX) is twice more reproducible than the reference CMR(SAX) method, even though the LVEF is consistently overestimated compared with CMR(SAX). However, the CMR(LAX) LVEF determination provides values closer to TTE measurements, the most available and commonly used method in clinical practice, clinical trials, and guidelines in ischemic cardiomyopathy. Moreover, LVEF determination by CMR(LAX) allows a 63% gain of acquisition/reading time compared with CMR(SAX). Thus, despite the fact that LVEF obtained from CMR(SAX) remains the gold standard, CMR(LAX) should be considered to shorten the overall imaging acquisition and reading time as a putative replacement.