Comparison of left ventricular function assessment using phonocardiogram- and electrocardiogram-triggered 2D SSFP CINE MR imaging at 1.5 T and 3.0 T

As high-field cardiac MRI (CMR) becomes more widespread the propensity of ECG to interference from electromagnetic fields (EMF) and to magneto-hydrodynamic (MHD) effects increases and with it the motivation for a CMR triggering alternative. This study explores the suitability of acoustic cardiac triggering (ACT) for left ventricular (LV) function assessment in healthy subjects (n = 14). Quantitative analysis of 2D CINE steady-state free precession (SSFP) images was conducted to compare ACT's performance with vector ECG (VCG). Endocardial border sharpness (EBS) was examined paralleled by quantitative LV function assessment. Unlike VCG, ACT provided signal traces free of interference from EMF or MHD effects. In the case of correct R-wave recognition, VCG-triggered 2D CINE SSFP was immune to cardiac motion effects - even at 3.0 T. However, VCG-triggered 2D SSFP CINE imaging was prone to cardiac motion and EBS degradation if R-wave misregistration occurred. ACT-triggered acquisitions yielded LV parameters (end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF) and left ventricular mass (LVM)) comparable with those derived from VCG-triggered acquisitions (1.5 T: ESVVCG = (56 ± 17) ml, EDVVCG = (151 ± 32) ml, LVMVCG = (97 ± 27) g, SVVCG = (94 ± 19) ml, EFVCG = (63 ± 5)% cf. ESVACT = (56 ± 18) ml, EDVACT = (147 ± 36) ml, LVMACT = (102 ± 29) g, SVACT = (91 ± 22) ml, EFACT = (62 ± 6)%; 3.0 T: ESVVCG = (55 ± 21) ml, EDVVCG = (151 ± 32) ml, LVMVCG = (101 ± 27) g, SVVCG = (96 ± 15) ml, EFVCG = (65 ± 7)% cf. ESVACT = (54 ± 20) ml, EDVACT = (146 ± 35) ml, LVMACT = (101 ± 30) g, SVACT = (92 ± 17) ml, EFACT = (64 ± 6)%). ACT's intrinsic insensitivity to interference from electromagnetic fields renders it suitable for clinical CMR. (orig.)