Accuracy of M mode echocardiographic measurements of the left ventricle

M mode echocardiography provides quantitative information regarding the dimensions of the left ventricle. To compare left ventricular dimensions obtained by several methods from the M mode echocardiogram with actual dimensions, M mode echocardiograms of the inferventricular septum and left ventricular posterior wall were recorded simultaneously with sonomicrometer crystal signals of the left ventricular minor axis dimension in 12 instrumented open chest dogs. End-diastolic dimension from the M mode echocardiogram was measured (1) at the onset of the QRS complex, (2) at the peak of the R wave of the electrocardiogram, and (3) as the largest diameter. End-systolic dimension was measured from the M mode echocardiogram (1) at the nadir of septal motion, (2) at the peak of posterior wall motion, and (3) as the smallest dimension. End-diastolic dimension measured either at the onset of the QRS complex or at the peak of the R wave did not differ from that measured from the sonomicrometer crystal signals. However, end-diastolic dimension measured as the largest diameter was significantly larger than that measured from the sonomicrometer crystal signals (p < 0.001). Endsystolic dimension measured at the nadir of septal motion did not differ from that measured from the sonomicrometer crystal signals; however, when measured at the most anterior ascent of posterior wall motion or as the smallest dimension, it was significantly smaller than end-systolic dimension measured from the sonomicrometer crystal signals (p < 0.05 and p < 0.001, respectively). On the M mode echocardiogram, end-diastolic dimension is most accurately measured at the onset of the QRS complex or at the peak of the R wave of the electrocardiogram. End-systolic dimension is most accurately measured at the nadir of posterior motion of the interventricular septum when septal motion is normal. These data support the recommendations of The American Society of Echocardiography on attempts to quantitate left ventricular minor axis dimensions from the M mode echocardiogram.