Key result
Atropine increases ejection fraction by ~8% in red-footed tortoises by eliminating the right-to-left shunt.
Why the study?
The ejection fraction of the trabeculated cardiac ventricle of reptiles had not previously been measured.
Absolute Event Rate: 96% vs 88%
ECG-gated flow MRI successfully measured high cardiac ejection fractions in red-footed tortoises, providing a validated methodology to study the complex hearts of ectotherms.
Validates ECG-gated MRI for ectotherm cardiac assessment; leaves open translation to comparative or clinical cardiovascular research.
The ejection fraction of the trabeculated cardiac ventricle of reptiles has not previously been measured. Here we use the gold standard clinical methodology – electrocardiogram (ECG) gated flow magnetic resonance imaging (MRI) – to validate stroke volume measurements and end diastolic ventricular blood volumes. This produces an estimate of ejection fraction in the red footed tortoise Chelonoidis carbonaria (n=5) under isoflurane anaesthesia of 88±11%. After elimination 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 possess lower ejection fractions.
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Williams et al. (2019) studied this question. Atropine vs. Baseline was evaluated on Cardiac ejection fraction. ECG-gated flow MRI measured a baseline cardiac ejection fraction of 88±11% in red-footed tortoises, which increased to 96±6% after elimination of the right-to-left shunt using atropine.
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