Cardiac MR Elastography: Comparison with left ventricular pressure measurement

OBJECTIVES:  To compare magnetic resonance elastography (MRE) with ventricular pressure changes in an animal model.

METHODS:  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. Correlation  coefficients between  wave  amplitudes  and  LV  pressure  as  well  as  between  wave  amplitudes  and  LV diameter were determined.

RESULTS:  A relationship between MRE and LV pressure was observed in all three animals (R2  0.76). No correlation was observed between MRE and LV diameter (R2 [1] 0.15). Instead, shear wave amplitudes  decreased  102  ±  58  ms  earlier  than  LV  diameters  at  systole  and  amplitudes increased 175 ± 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:  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

PMID: 19900266

Posted in Magnetic Resonance Imaging and tagged , , .

One Comment

  1. While there is a long way to go before MR elastography becomes a clinical tool, this study is interesting as it is the first to investigate the correlation between measured wave amplitudes and intracardiac chamber pressures as directly measured by catheter.
    The study (within its limitations) showed that changes in shear wave amplitudes over the cardiac cycle were caused by elasticity changes in the myocardium and not driven by geometrical effects. As the authors state in their discussion: “The most important result of this study is that there is a clear distinction between the coherences of WAV pressure and WAV geometry functions: While wave amplitudes vary (reciprocally) in synchrony with pressure changes there is a clear delay between MRE and LV-diameter.”
    On the technical side, the authors required a continuous infusion of metoprolol tatrate to maintain the heart rate (although they don’t mention the HR goal nor achieved) and the images were obtained during 1 minute periods of stopped ventilation. Clearly, although incredibly exciting, there is still some work to do to bring this technology to the clinical arena.

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