Noncompressibility of myocardium during systole with freehand three-dimensional echocardiography.

BACKGROUND

Measures of ventricular performance, such as the ejection fraction, assume that myocardium is noncompressible and does not change volume significantly from end diastole to end systole. Although this principle is widely accepted as true, little data exist in the literature to support it. Freehand 3-dimensional (3D) echocardiography has previously been shown to be highly accurate for measurement of myocardial mass and volume. Therefore, we hypothesized that it has sufficient accuracy to test the validity of this assumption. We measured myocardial volume at end diastole and end systole in 2 groups of subjects with hypertrophy.

METHODS

Forty-one healthy young adult athletes and 17 adult patients with hypertension, hypertrophy, normal ejection fraction, and heart failure symptoms underwent examination with freehand 3D echocardiography. Endocardial and epicardial surfaces at end diastole and end systole were reconstructed, and their volumes were computed. From these surface volumes, myocardial volume at end diastole and end systole and epicardial stroke volume and endocardial stroke volume were calculated. These volumes were compared with the 2 sample paired t test.

RESULTS

Myocardial volume was constant from diastole to systole (174.7 +/- 45.3 mL versus 174.6 +/- 45.8 mL; P = not significant), and endocardial and epicardial stroke volumes were identical (76.0 +/- 17.4 mL versus 76.0 +/- 17.1 mL; P = not significant). The average absolute difference between the end-diastolic and end-systolic myocardial volumes was 1.9 mL, or less than 1.1% of end-diastolic volume.

CONCLUSION

Myocardial volume measured with freehand 3D echocardiography does not change significantly during systole. Myocardial volume may be considered noncompressible for purposes of measurement of ventricular function with freehand 3D echocardiography. Comparison of end-diastolic and end-systolic myocardial volumes may be used for quality assurance in performing 3D reconstructions.