Assessment of left ventricular mass in mice: Comparison between two-dimensional and M-mode echocardiography

Objective: M-mode echocardiography has been used extensively for estimating left ventricular (LV) mass in mice, but accuracy is limited by its unidimensional nature. This study tested whether two-dimensional (2-D) echocardiographic measurement of LV mass using area-length and truncated ellipsoid methods overcomes this limitation. Methods: Twenty-five anesthetized FVB/N mice (Mus musculus) underwent high resolution (15 MHZ) two-dimensionally directed M-mode and 2-D echocardiography. End-diastolic epicardial and endocardial areas from short-axis views and the LV orthogonal long-axis views were measured, while LV mass was calculated by 2-D area-length and truncated ellipsoid methods. LV mass was calculated from M-mode using the uncorrected cube equation. Hearts were removed and weighed after completing the echocardiographic studies. The correlation and agreement between echocardiographic-determined LV mass and gravimetric LV weight were examined. Results: LV mass using the area-length method correlated better with autopsy LV weight (r = 0.87, slope = 0.87, standard error of the estimate [SEE] = 12.4 mg, P < 0.001) than M-mode echocardiography (r = 0.85, slope 0.71, SEE = 11.1 mg, P < 0.001), and the degree of agreement (bias +/- 2 SD) was better (10.2 +/- 25.1 mg vs 13.1 +/- 25.8 mg, P = NS). Although 2-D truncated ellipsoid LV mass showed a good correlation with necropsy LV weight (r = 0.87, slope = 0.78, SEE = 11.0 mg, P < 0.001), the agreement between the truncated ellipsoid estimates and LV weight was less than that between M-mode and gravimetric LV mass. Conclusions: The 2-D area-length method is an accurate method of LV mass determination in symmetrical ventricles and can be used as an alternative for in vivo measurement of LV mass in mice.