Determination of left ventricular long-axis orientation using MRI: changes during the respiratory and cardiac cycles in normal and diseased subjects.
BACKGROUND: It has previously been shown that magnetic resonance imaging (MRI) can be used to accurately determine left ventricular (LV) long-axis orientation in healthy individuals. However, the inter- and intra-observer variability in patients with acute coronary syndrome (ACS) and chronic heart failure (CHF) has not been explored. Furthermore, the changes in LV long-axis orientation because of respiration and during the cardiac cycle remain to be determined. METHODS: LV long-axis orientation was determined by MRI in the frontal and transverse planes in 44 subjects with no cardiac disease, 20 ACS patients and 13 CHF patients. Changes in LV long-axis orientation because of respiration were assessed in a subset of 25 subjects. Changes during the cardiac cycle were assessed in six subjects from each subject group. Reproducibility was assessed by a re-examination of 17 subjects after 28 days. RESULTS: The inter- and intra-observer variability for LV long-axis orientation was low for all subject groups. The difference between the baseline and the 28 days examinations was -1.4+/-5.9 degrees and -0.8+/-4.4 degrees in the frontal and transverse planes, respectively. No significant change in LV long-axis orientation was found between end-expiration and end-inspiration (frontal plane, P=0.63 and transverse plane, P=0.42; n=25). No significant difference in change of the LV long-axis orientation during the cardiac cycle was found between the subject groups (frontal plane, chi-square 1.8, P=0.40 and transverse plane, chi-square 5.7, P=0.06). CONCLUSIONS: There is a low inter-and intra-observer variability and a high reproducibility for determining LV long-axis orientation in patients with no cardiac disease as well as in patients with ACS or CHF. There is no significant change in LV long-axis orientation due to respiration, and only small changes during the cardiac cycle in these groups.
Foster, JE; Engblom, H; Martin, TN; Wagner, GS; Steedman, T; Ferrua, S; Elliott, AT; Dargie, HJ; Groenning, BA
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