Determination of left ventricular mass by magnetic resonance imaging in hearts deformed by acute infarction.

Measurement of left ventricular (LV) mass by magnetic resonance imaging (MRI) is accurate in normal hearts. Because determination of mass by MRI does not require assumptions about ventricular shape, this method may be well suited for evaluating hearts distorted by infarction. To test this hypothesis, gated MRI was performed in 15 dogs before and after acute myocardial infarction. The LV mass of each dog was calculated from five short-axis images acquired at end systole, when shape distortion is greatest, at end diastole, and also from slices at varying phases of the cycle with a multiphase mode that required only one acquisition. Correlation was excellent between actual mass and end-systolic mass before infarction (p less than 0.001, r = 0.98, and SEE = 5.1 g) and after infarction (p less than 0.001, r = 0.97, and SEE = 6.6 g). Likewise, values correlated closely at end diastole before (p less than 0.001, r = 0.96, and SEE = 6.7 g) and after infarction (p less than 0.001, r = 0.94, and SEE = 8.7 g). Surprisingly, measurements of mass by a multiphase mode were also very accurate before (p less than 0.001, r = 0.98, and SEE = 5.1 g) and after (p less than 0.001, r = 0.95, and SEE = 6.49 g) infarction. Therefore, at the same phase and at multiphases of the cardiac cycle, MRI permits accurate determination of LV mass in distorted hearts.