Published online Sep 26, 2018. doi: 10.4330/wjc.v10.i9.110
Peer-review started: March 29, 2018
First decision: April 23, 2018
Revised: June 28, 2018
Accepted: August 5, 2018
Article in press: August 5, 2018
Published online: September 26, 2018
Processing time: 185 Days and 8.2 Hours
To compare myocardial viability assessment accuracy of cardiac magnetic resonance imaging (CMR) compared to [18F]-fluorodeoxyglucose (FDG)- positron emission tomography (PET) depending on left ventricular (LV) function.
One-hundred-five patients with known obstructive coronary artery disease (CAD) and anticipated coronary revascularization were included in the study and examined by CMR on a 1.5T scanner. The CMR protocol consisted of cine-sequences for function analysis and late gadolinium enhancement (LGE) imaging for viability assessment in 8 mm long and contiguous short axis slices. All patients underwent PET using [18F]-FDG. Myocardial scars were rated in both CMR and PET on a segmental basis by a 4-point-scale: Score 1 = no LGE, normal FDG-uptake; score 2 = LGE enhancement < 50% of wall thickness, reduced FDG-uptake ( ≥ 50% of maximum); score 3 = LGE ≥ 50%, reduced FDG-uptake (< 50% of maximum); score 4 = transmural LGE, no FDG-uptake. Segments with score 1 and 2 were categorized “viable”, scores 3 and 4 were categorized as “non-viable”. Patients were divided into three groups based on LV function as determined by CMR: Ejection fraction (EF), < 30%: n = 45; EF: 30%-50%: n = 44; EF > 50%: n = 16). On a segmental basis, the accuracy of CMR in detecting myocardial scar was compared to PET in the total collective and in the three different patient groups.
CMR and PET data of all 105 patients were sufficient for evaluation and 5508 segments were compared in total. In all patients, CMR detected significantly more scars (score 2-4) than PET: 45% vs 40% of all segments (P < 0.0001). In the different LV function groups, CMR found more scar segments than PET in subjects with EF< 30% (55% vs 46%; P < 0.0001) and EF 30%-50% (44% vs 40%; P < 0.005). However, CMR revealed less scars than PET in patients with EF > 50% (15% vs 23%; P < 0.0001). In terms of functional improvement estimation, i.e., expected improvement after revascularization, CMR identified “viable” segments (score 1 and 2) in 72% of segments across all groups, PET in 80% (P < 0.0001). Also in all LV function subgroups, CMR judged less segments viable than PET: EF < 30%, 66% vs 75%; EF = 30%-50%, 72% vs 80%; EF > 50%, 91% vs 94%.
CMR and PET reveal different diagnostic accuracy in myocardial viability assessment depending on LV function state. CMR, in general, is less optimistic in functional recovery prediction.
Core tip: Both cardiac magnetic resonance imaging (CMR) and [18F]-fluorodeoxyglucose-positron emission tomography (PET) are considered standard methods and reliable in myocardial viability imaging in coronary artery disease. However, CMR in general detects more scar and is, therefore, less optimistic in functional recovery prediction. Moreover, CMR and PET reveal different diagnostic accuracy depending on left ventricular (LV) function state: Particularly in severe and moderate LV function impairment, where revascularization is performed to improve function, CMR detects more scar and less viable myocardium - most probably due to higher spatial resolution. This aspect has not been reported, yet. Irrespective of LV function, PET might overestimate the improvement of regional and global function after revascularization.