How much are atrial volumes and ejection fractions assessed by cardiac magnetic resonance imaging influenced by the ECG gating method?
OBJECTIVE
Most magnetic resonance imaging (MRI) centers currently use prospective electrocardiographic (ECG) triggering for image acquisition. Retrospectively gated sequences allow the coverage of the entire cardiac cycle. It has been recently shown that ventricular volumes and ejection fraction (EF) differ according to the gating method used for image acquisition. The authors sought to evaluate how much measurements of atrial volumes and EF differ depending on the gating method.


METHODS
Eighteen subjects with no cardiovascular disease were investigated by MRI using a 1.5 Tesla scanner. Images were acquired with a gradient-echo sequence with steady-state free precession (SSFP) using the standard short-axis method for volume and EF measurements. Images were acquired with 6 mm thick slices using both prospective triggering and retrospective gating. Left and right atrial volumes (end diastolic volume [EDV]; end systolic volume [ESV]; stroke volume [SV]) and EF were determined with a commercially available software package.


RESULTS
ESV was significantly smaller with the retrospectively gated SSFP sequence than with the prospectively triggered sequence (mean difference: ESV left 3.97 +/- 1.3 ml, p < 0.0001; ESV right 4.34 +/- 1.8 ml, p < 0.0001). EF and SV were significantly smaller with prospective triggering (mean difference: EF left -5.94 +/- 0.9%, p < 0.0001; EF right -5.52 +/- 1.3 %, p < 0.0001; SV left -3.99 +/- 1.3 ml, p < 0.0001; SV right -4.32 +/- 1.9 ml, p < 0.0001). EDV remained unchanged (mean difference: EDV left -0.03 +/- 0.8 ml, p = 0.902; right EDV 0.04 +/- 0.7 ml, p = 0.882).


CONCLUSIONS
The gating method has a significant impact on atrial volume and EF measurements. Atrial EF is underestimated by using the prospective triggering technique.
Sievers
Burkhard
B
Department of Cardiology and Angiology, Marienhospital, University of Bochum, Herne, NRW Germany. burkhard.sievers@duke.edu
Addo
Marvin
M
Kirchberg
Simon
S
Bakan
Asli
A
John-Puthenveettil
Binu
B
Franken
Ulrich
U
Trappe
Hans-Joachim
HJ
D002306:Cardiac Volume; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006325:Heart Atria / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013318:Stroke Volume; D013599:Systole