title: Evaluating cardiac physiology through echocardiography in bottlenose dolphins: using stroke volume and cardiac output to estimate systolic left ventricular function during rest and following exercise.
abstract: Heart-rate (fH) changes during diving and exercise are well documented for marine mammals, but changes in stroke volume (SV) and cardiac output (CO) are much less known. We hypothesized that both SV and CO are also modified following intense exercise. Using transthoracic ultrasound Doppler at the level of the aortic valve, we compared blood flow velocities in the left ventricle and cardiac frequencies during rest and at 1, 3 and 4 min after a bout of exercise in 13 adult bottlenose dolphins (Tursiops truncatus, six male and seven female, body mass range 143-212 kg). Aortic cross-sectional area and ventricle blood velocity at the aortic valve were used to calculate SV, which together with fH provided estimates of left CO at rest and following exercise. fH and SV stabilized approximately 4-7 s following the post-respiratory tachycardia, so only data after the fH had stabilized were used for analysis and comparison. There were significant increases in fH, SV and CO associated with each breath. At rest, fH, SV and CO were uncorrelated with body mass, and averaged 41±9 beats min(-1), 136±19 ml and 5514±1182 l min(-1), respectively. One minute following high intensity exercise, the cardiac variables had increased by 104±43%, 63±11% and 234±84%, respectively. All variables remained significantly elevated in all animals for at least 4 min after the exercise. These baseline values provide the first data on SV and CO in awake and unrestrained cetaceans in water.
authors.affiliation: Oceanografic, Ciudad de las Artes y las Ciencias, Valencia 46013, Spain slemon@mac.com.
authors.forename: Stefan
authors.initials: S
authors.lastname: Miedler
authors.affiliation: Department of Life Science, Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Fahlman
authors.affiliation: Oceanografic, Ciudad de las Artes y las Ciencias, Valencia 46013, Spain.
authors.forename: Mónica
authors.initials: M
authors.lastname: Valls Torres
authors.affiliation: Oceanografic, Ciudad de las Artes y las Ciencias, Valencia 46013, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Álvaro Álvarez
authors.affiliation: Oceanografic, Ciudad de las Artes y las Ciencias, Valencia 46013, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Garcia-Parraga
mesh_terms: D000818:Animals; D050681:Bottle-Nosed Dolphin / Q000502:physiology*; D002302:Cardiac Output; D004452:Echocardiography; D005260:Female; D008297:Male; D010805:Physical Conditioning, Animal; D012146:Rest; D013318:Stroke Volume; D013599:Systole; D016277:Ventricular Function, Left / Q000502:physiology*
keywords: Aortic flow; Cardiac reserve; Cardiac ultrasound; Cetaceans; Diving physiology; Ejection fraction; Marine mammals