High throughput echocardiography in conscious mice: training and primary screens

Genetic engineering techniques led to an exponential increase in the number of transgenic and knock-out mouse models. For many genetically modified mice, high throughput echocardiography is an essential part of a systematic screening workflow. Many researchers perform mouse echocardiography in conscious animals to avoid anesthesia-induced impairment of cardiac function. However, it has been controversially discussed whether mice need to be habituated to handling before their cardiac function can be assessed. The aim of this study was to test the influence of training on parameters assessed during conscious mouse echocardiography. In addition, we tested whether a simple and fast echocardiography protocol has sufficient sensitivity and specificity for primary screening.

Examined parameters include fractional shortening, heart rate and respiratory rate. A total of 139 mice were examined in this study with a total of 587 echocardiograms. 103 mice were examined on five consecutive days (with examinations on day 1 - 4 regarded as training), 36 mice were only examined on day 1 and 5.

Fractional shortening, heart rate and respiratory rate did not show any statistically significant difference between day 1 and day 5 in both groups. The sensitivity and specificity of fractional shortening assessment for predicting a homozygote knock out genotype were 86 % and 97 %, respectively.

We conclude that conscious mouse echocardiography can be performed in untrained mice. Fractional shortening measurements may suffice for correct phenotyping in a high throughput setting.