Magnetic resonance imaging versus echocardiography to ascertain the regression of left ventricular hypertrophy after bioprosthetic aortic valve replacement: Results of the REST study

Objectives: To compare the decrease in left ventricular mass index (LVMI) by magnetic resonance imaging (MRI) versus transthoracic echocardiography (TTE) after aortic valve replacement (AVR) for severe aortic stenosis with Epic and Epic Supra stented porcine bioprostheses (St Jude Medical, Inc, St Paul, Minn). Methods: This prospective multicenter study enrolled 149 patients who underwent AVR between January 2006 and February 2008. TTE and cardiac MRI measurements of LVMI were made at baseline and at 6 months of follow-up and were compared. Changes in mean pressure gradients were examined using TTE. Results: TTE measurements of LVMI were 48% to 63% higher than the MRI measurements. A decrease in LVMI from 137 +/- 32 to 95 +/- 16 g/m(2) with the Epic and from 139 +/- 29 to 104 +/- 28 g/m(2) with the Epic Supra valves (P < .0001 for both comparisons) was measured by TTE. Cardiac MRI revealed decreases in LVMI from 84 +/- 20 to 64 +/- 12 g/m(2) and from 86 +/- 27 to 64 +/- 17 g/m(2) with the Epic and Epic Supra valves, respectively (P < .0001 for both comparisons). TTE revealed a significant regression of mean pressure gradients from 51.6 +/- 15.3 to 15.5 +/- 5.2 mm Hg with the Epic and from 46.7 +/- 19.4 to 17.9 +/- 12.8 mm Hg with the Epic supra (P < .0001 for both comparisons). Conclusions: A significant decrease in LVMI was measured after AVR with all sizes of both bioprosthetic models. Because of the overestimation of the decrease in LVMI by the Devereux formula, as well as the higher accuracy and reproducibility of cardiac MRI measurements, the latter should be preferred to TTE. An ultimate validation of this thesis could only be done comparing each of these modalities with pathologic examination. (J Thorac Cardiovasc Surg 2012;144:640-5)