[MARMAM] New publication - Dolphin cardiac auscultation and characterization of heart murmurs

Barb Linnehan barb.linnehan at nmmpfoundation.org
Tue Nov 3 09:36:03 PST 2020


Dear colleagues,

We are pleased to share our recent publication:

Linnehan BK, Hsu A, Gomez FM, Huston SM, Takeshita R, Colegrove KM, Rowles
TK, Barratclough A, Musser WB, Harms CA, Cendejas V, Zolman ES, Balmer BC,
Townsend FI, Wells RS, Jensen ED, Schwacke LH and Smith CR. (2020)
Standardization of Dolphin Cardiac Auscultation and Characterization of
Heart Murmurs in Managed and Free-Ranging Bottlenose Dolphins (*Tursiops
truncatus*). Front. Vet. Sci. 7:570055. doi: 10.3389/fvets.2020.570055

Available open access:
https://www.frontiersin.org/articles/10.3389/fvets.2020.570055/full

Abstract
Cardiac auscultation is an important, albeit underutilized tool in aquatic
animal medicine due to the many challenges associated with in-water
examinations. The aims of this prospective study were to (1) establish an
efficient and repeatable in-water cardiac auscultation technique in
bottlenose dolphins (Tursiops truncatus), (2) describe the presence and
characterization of heart murmurs detected in free-ranging and managed
dolphins, and (3) characterize heart murmur etiology through
echocardiography in free-ranging dolphins. For technique development, 65
dolphins cared for by the Navy Marine Mammal Program (Navy) were
auscultated. The techniques were then applied to two free-ranging dolphin
populations during capture-release health assessments: Sarasota Bay,
Florida (SB), a reference population, and Barataria Bay, LA (BB), a
well-studied population of dolphins impacted by the Deepwater Horizon oil
spill. Systolic heart murmurs were detected at a frequent and similar
prevalence in all dolphin populations examined (Navy 92%, SB 89%, and BB
88%), and characterized as fixed or dynamic. In all three populations,
sternal cranial and left cranial were the most common locations for murmur
point of maximal intensity (PMI). An in-water transthoracic echocardiogram
technique was refined on a subset of Navy dolphins, and full
echocardiographic exams were performed on 17 SB dolphins and 29 BB
dolphins, of which, 40 had murmurs. Spectral Doppler was used to measure
flow velocities across the outflow tracts, and almost all dolphins with
audible murmurs had peak outflow velocities ≥1.6 m/s (95%, 38/40); three
dolphins also had medium mitral regurgitation which could be the source of
their murmurs. The presence of audible murmurs in most of the free-ranging
dolphins (88%) was attributed to high velocity blood flow as seen on
echocardiography, similar to a phenomenon described in other athletic
species. These innocent murmurs were generally characterized as Grade I-III
systolic murmurs with PMI in the left or sternal cranial region. This study
is the first to describe an efficient technique for in-water dolphin
cardiac auscultation, and to present evidence that heart murmurs are common
in bottlenose dolphins.

Please feel free to contact me with questions.
Cheers,
Barb Linnehan
--
Barbara Linnehan, DVM
Deputy Director of Medicine
National Marine Mammal Foundation
U.S. Navy Marine Mammal Program
Barb.Linnehan at nmmf.org
*Linnehan at spawar.navy.mil <Linnehan at spawar.navy.mil>*
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