Magnetic resonance imaging (MRI) reveals high cardiac ejection fractions in red-footed tortoises (Chelonoidis carbonarius).
Catherine J A WilliamsEva M GreunzSteffen RinggaardKasper HansenMads F BertelsenTobias WangPublished in: The Journal of experimental biology (2019)
The ejection fraction of the trabeculated cardiac ventricle of reptiles has not previously been measured. Here, we used the gold standard clinical methodology - electrocardiogram-gated flow magnetic resonance imaging (MRI) - to validate stroke volume measurements and end diastolic ventricular blood volume. This produced an estimate of ejection fraction in our study species, the red footed tortoise Chelonoidis carbonarius (n=5), under isoflurane anaesthesia of 88±11%. After reduction of the prevailing right-to-left intraventricular shunt through the action of atropine, the ejection fraction was 96±6%. This methodology opens new avenues for studying the complex hearts of ectotherms, and validating hypotheses on the function of a more highly trabeculated heart than that of endotherms, which have lower ejection fractions.
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