OBJECTIVES:Â To compare magnetic resonance elastography (MRE) with ventricular pressure changes in an animal model.
METHODS:Â Three pigs of different cardiac physiology (weight, 25 to 53 kg; heart rate, 61 to 93 bpm; left ventricular [LV] end-diastolic volume, 35 to 70 ml) were subjected to invasive LV pressure measurement by catheter and noninvasive cardiac MRE. Cardiac MRE was performed in a short-axis view of the heart and applying a 48.3-Hz shear-wave stimulus. Relative changes in LV-shear wave amplitudes during the cardiac cycle were analyzed. CorrelationÂ coefficients betweenÂ waveÂ amplitudesÂ andÂ LVÂ pressureÂ asÂ wellÂ asÂ betweenÂ waveÂ amplitudesÂ andÂ LV diameter were determined.
RESULTS:Â A relationship between MRE and LV pressure was observed in all three animals (R2 Â 0.76). No correlation was observed between MRE and LV diameter (R2  0.15). Instead, shear wave amplitudesÂ decreasedÂ 102Â Â±Â 58Â msÂ earlierÂ thanÂ LVÂ diametersÂ atÂ systoleÂ andÂ amplitudes increased 175 Â± 40 ms before LV dilatation at diastole. Amplitude ratios between diastole and systole ranged from 2.0 to 2.8, corresponding to LV pressure differences of 60 to 73 mmHg.
CONCLUSIONS:Â Externally induced shear waves provide information reflecting intraventricular pressure changes which, if substantiated in further experiments, has potential to make cardiac MRE a unique noninvasive imaging modality for measuring pressure-volume function of the heart. Tavon Austin Authentic Jersey