Abstract
Electrocardiographic (ECG) measurements were recorded in two subspecies of awake, apparently healthy, free-living manatees (Trichechus manatus manatus and Trichechus manatus latirostis) undergoing routine field examinations in Belize and Florida. The manatee is unique in its cardiac and thoracic anatomy, and detailed studies on ECGs in manatees are lacking.1-6 The objectives of this prospective study were 1) to develop a technique to obtain ECG recordings in awake manatees applicable to field and captive settings; 2) to determine reference ranges for standard ECG recordings (heart rate and rhythm; wave-form morphology, amplitude, and duration; and mean electrical axis); and 3) to provide a means of continually monitoring heart rate and rhythm of sick, stranded, and healthy manatees.
Twelve manatees (nine from Belize and three from Florida) were used in this study. Six juveniles (consisting of dependent and independent calves) and six adults (>250cm) were maintained in ventral recumbency for ECG measurements. Six lead ECGs were recorded on all manatees and standard ECG measurements were made. The mean and median values for each of the above measurements were calculated and compared. Statistical differences using a t-test for quality of measurements were determined.
Evaluation showed significant differences in heart rate (p = 0.047), P wave duration (p = 0.019), mean electrical axis (p = 0.021) and PR interval (p = 0.025) between adult manatees and calves. No significant differences were seen when comparing sub-species or sex. Evaluation allowed for establishment of preliminary normal ECG reference ranges for manatees (See Table 1).
This abstract documents the techniques for and baseline recordings of ECGs in juvenile and adult free-living manatees. The project also demonstrates that continual assessment of cardiac function in the awake manatee can be performed and used to aid veterinarians and biologists in routine health assessment, during procedures, and in detecting the presence of cardiac disease or dysfunction.
Table 1.
|
Normal manatee ECG values |
|
|
|
Range |
|
|
Heart rate (bpm) |
51.41-65.92 |
Adult |
|
61.09-74.56 |
Calf |
|
P wave height (mV) |
0.04-0.05 |
|
|
P wave duration (msec) |
0.12-0.17 |
Adult |
|
0.04-0.13 |
Calf |
|
P-R duration (msec) |
0.23-0.32 |
Adult |
|
0.15-0.26 |
Calf |
|
QRS complex height (mV) |
0-0.25 |
|
|
QRS duration (msec) |
0.08-0.11 |
|
|
S-T segment (mV) |
0.15-0.31 |
|
|
T wave height (mV) |
0-0.09 |
|
|
T wave duration (msec) |
0.09-0.21 |
|
|
Q-T interval (msec) |
0.44-0.56 |
|
|
MEA (degrees) |
-67.94-7.94 |
Adult |
|
-7.94-67.94 |
Calf |
Acknowledgments
We thank Mr. Robert Bonde (USGS), Dr. James (Buddy) Powell (Wildlife Trust), and Dr. Holly Edwards (FWC) for their help in manatee capture, Mr. Arthur Wong and Dr. Lara Croft (University of Florida) for their help with data collection and ECG recording, Ben Winton (Florida Medical Sales, Inc.) for donation of the MAC 500 Resting ECG machine, and the Aquatic Animal Department at the College of Veterinary Medicine, University of Florida, for financial assistance.
References
1. Murphy D. 2003. Sirenia. In: Fowler, M.E. and R.E. Miller. Zoo and Wild Animal Medicine, 5th ed. W.B. Saunders Co., Pennsylvania. Pp. 476-481.
2. Rommel SA, LJ Lowenstine. 2001. Gross and Microscopic Anatomy. In: Dierauf, L.A. and F.M.D. Gulland. CRC Handbook of Marine Mammal Medicine, 2nd ed. CRC Press, New York. Pp. 142-145.
3. Rommel SA, JE Reynolds. 2000. Diaphragm structure and function in the Florida manatee (Trichechus manatus latirostris). The Anatomical Record, 259(1):41-51.
4. Tenney SM, NH Hanover. 1958. Correlative observations on the electrocardiogram and morphology of the heart of the Florida manatee. Am Heart J. 56 (6):933-938.
5. Tilley LP (ed.). 1992. Essentials of Canine and Feline Electrocardiography. Lea and Febiger, Pennsylvania. Pp. 40-55.
6. Walsh MT, GD Bossart. 1999. Manatee Medicine. In: Fowler M.E. and R.E. Miller. Zoo and Wild Animal Medicine, 4th ed. W.B. Saunders, Pennsylvania. Pp. 507-516.