Background:
Left ventricular (LV) mass (LVM) predicts cardiovascular morbidity and mortality, thus accurate quantification of LVM is essential. Cardiac magnetic resonance (CMR) is considered the gold-standard for LVM and right ventricular (RV) mass (RVM) quantification. The steady-state free precession (SSFP) is the most widely used sequence nowadays; however, SSFP-derived LVM/RVM has only been validated in normal animals, while CMR is usually performed under pathological conditions. Therefore, our objective was to validate in vivo SSFP-derived LVM/RVM with the gold-standard autopsy weights of experimental animals with myocardial infarction (MI), LV remodeling, and pulmonary hypertension (PH).
Methods:
MI was induced in 11 pigs by balloon occlusion of the proximal LAD for 60 min, and MRIs were obtained 2 months post-MI. PH was induced in 11 pigs by surgical ligation of three pulmonary veins and animals underwent CMR 4 months post-surgery. Animals were euthanized immediately after CMR. Each ventricle was separately weighted using a high-fidelity scale. MRI studies were performed with a 3.0 Tesla magnet.
Results:
In the MI model, infarct size (IS) was 29±6% of LV, LVEF 34±8%, RVEF 62±149%, mean pulmonary artery pressure (mPAP) 16±4mmHg, and pulmonary vascular resistance (PVR) 2.3±1.1 Wood units. In the PH model, IS was 0%, LVEF 64±5%, RVEF 55±10%, mPAP 36±16mmHg and PVR was 7.2±5.5 Wood units. All animals provided images of diagnostic quality. Excellent correlations were obtained between SSFP-calculated LV mass (86.6±12.9g) and autopsy-measured LV mass (91.1±15.2g, r=0.97, p<0.001). For LV, the correlation was not different in both groups of animals (r=0.98, p=0.01 for post-MI animals; r=0.96, p=0.01 for PH animals). There was also a strong correlation between RV mass obtained from CMR (37.9±14.1g) and from autopsy (41.6±13.1g r=0.9, p=0.01). For RV, the correlation was higher in PH animals (r=0.92, p<0.001) than in post-MI pigs (r=0.8, p=0.01).
Conclusions:
In vivo SSFP-CMR sequences determine LVM and RVM accurately and reliably compared with autopsy. Therefore, our study provides further validation for the clinical use of SSFP sequence derived LVM and RVM.
Range of ventricular dimensions and function by steady-state free precession cine MRI in repaired tetralogy of Fallot: Right ventricular outflow tract patch vs. conduit repair