Influence of scanning frequency and ultrasonic contrast agent on reproducibility of left ventricular measurements in the mouse.

BACKGROUND: Mice are now widely used as models of cardiovascular disease. Their small size and fast heart rates are technically challenging to echocardiography. This study examined the influence of different scanning frequencies and ultrasonic contrast agent (UCA) on the accuracy and reproducibility of measurements of left ventricular (LV) structure and function. METHODS: Normal mouse hearts (C57BL6) were imaged at 3 different scanning frequencies before and after intravenous injection of the UCA, Optison. Coronary artery ligation mice and sham-operated controls were scanned at 10-22 MHz with and without UCA. RESULTS: Scanning frequency had no significant effect on intraobserver or interobserver variation of LV measurements in normal mice under baseline conditions. Use of UCA significantly reduced estimated ejection fraction at 10-22 MHz compared with baseline (baseline 50.8 +/- 7.6% vs UCA 39.7 +/- 7.6%; P = .03) and significantly increased values for LV cavity dimensions (eg, LV area diastole 20.74 +/- 1.20 vs 23.23 +/- 0.98 mm 2 ; P = .002). UCA significantly reduced intraobserver and interobserver variation in LV ejection fraction. CONCLUSIONS: Scanning frequency had no significant effect on reproducibility of LV measurements in the mouse but UCA significantly reduced interobserver variation. Use of UCA could reduce the number of mice required in any given experiment to observe a statistically significant change in LV function.