Abstract

Fetal echocardiography represents the single most important tool for the assessment of the cardiovascular well-being of the human fetus. Because of logistic, anatomic and behavioral challenges, detailed fetal echocardiographic evaluation of dolphins has not been previously described. We sought to develop an approach to evaluating the fetal dolphin's cardiovascular status using conventional, fetal echocardiographic techniques developed in humans. A captive, 18-year-old pregnant female dolphin, living at an open water facility, carrying a singleton fetus with an estimated gestational age of 11 months, was evaluated in the water, without sedation, using a conventional, portable ultrasound system (Cypress, Siemens Medical Systems). Multiple transducers, probe positions, and pregnant dolphin positions were utilized to maximize image quality. Fetal echocardiography included two-dimensional imaging of the heart and great vessels, pulsed Doppler evaluation of the umbilical artery and vein, and color flow mapping of the heart and great vessels. A thorough assessment of the fetal dolphin's cardiovascular status was successfully performed without complications. The best images were obtained with the dolphin on her right side, with the probe mid lateral on the left side at the level of the dorsal fin. We demonstrated normal structure and function of the heart and great vessels, including the pulmonary veins, inferior vena cava, right and left atria, foramen ovale, tricuspid and mitral valves, right and left ventricles, ventricular septum, pulmonary and aortic valves, main pulmonary artery and ascending aorta, ductus arteriosus and descending aorta. Pulsed Doppler techniques demonstrated normal umbilical arterial and venous waveforms, and color flow mapping demonstrated absence of valvar regurgitation. Fetal cardiovascular health was demonstrated by the following findings: structurally normal heart and great vessels, absence of pulsatility in the umbilical vein, absence of significant pericardial effusion, absence of tricuspid regurgitation, and good biventricular systolic function. Generous diastolic flow in the umbilical artery suggested low (normal) placental resistance. We conclude that fetal echocardiography can provide a detailed assessment of the cardiovascular status of the fetal dolphin, even as late as 11 months gestation. Further work applying this technique to earlier gestation fetuses may increase our understanding of normal fetal dolphin cardiovascular physiology and development, and may represent an important clinical tool for the assessment of the overall well-being of the fetal bottlenose dolphin.