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J. ELECTROCARDIOLOGY, 8 (3) 241-246
The Electrocardiogram of Burros BY TAKETOSHI MORIMOTO, STEVEN M. HORVATH AND MOHAMED K. YOUSEF*
SUMMARY Electrocardiograms of two burros are pre-
sented. Compared to those seen in humans, amplitudes were lower, especially in lead I, and marked prolongations were observed in P-Q and Q-T intervals. The QRS axes were craniad.
Our knowledge of the electrocardiograms of equ ines r e l a t e s exc lus ive ly to the horse , Equus caballus. 1.2 We were unable to find any reports dealing with the electrocardiogram of the burro, despite the fact tha t the burro, Equus asinus, commonly known as the don- key or the ass, is one of the oldest domesti- cated animals. Elec t rocard iograms (ECGs) were recorded on two burros on whom exten- sive physiological da ta have been accumu- lated, especially in relat ion to their adapt- ative potentials towards dehydrat ion induced by wa te r depr iva t ion and work in dese r t heat.3-s
MATERIALS AND METHODS The two female burros, Mabel and Maud, were
about 9 years old at the time of this study and weighed 240 and 216 kg respectively. Their history and physical and physiological characteristics have been reported. 3-s They are stabled in corrals near Boulder City, Nevada, where the ECGs were recorded. The recordings were taken as the burros stood quietly without anesthesia or any other medication. These animals had been well trained for this quiet standing in order to measure their metabolic heat production. Needle electrodes (20 gauge subdermal needle connected to the leads) were inserted subcutaneously in the four limbs and a fifLh needle electrode was utilized for the V-leads (V-l, 2, 3, 4, 5, 6, 10). All recordings were made on a Hewlett-Packard 1500A electrocardiograph. A calibration of 1 mV = 2 cm deflection and paper speeds of 25 and 50 mm/sec were used. Standard unipolar, bipolar limb leads, and precordial V-leads were taken in sequence, and the re- cordings were measured and averaged for five successive cycles for each lead. The following parameters were determined: heart rate, P wave, P-R interval, QRS duration and Q-T interval. The amplitudes of the component deflections were also measured for each lead, and the electrical axes were plotted in the frontal plane for each burro.
From the Institute of Environmental Stress, Uni- versity of California, Santa Barbara, Santa Bar- bara, California 93106.
*Dr. Yousef is from the Laboratory of Environ- mental Patho-Physiology, Desert Research Insti- tute, University of Nevada System, Boulder City, Nevada 89005.
Reprint requests to Steven M. Horvath, Director, Institute of Environmental Stress, University of California, Santa BarlJara, Santa Barbara, CA 93106.
241
RESULTS Electrocardiograms recorded from two bur-
ros are shown in Figs. 1 and 2. There was a str iking similari ty between leads II and III and also between aVR and aVL in their shape and amplitude (Figs. 1 and 2).
Hear t rates and intervals are summarized in Table 1. Compared to ECGs of humans, marked prolongations were observed in P-R and Q-T intervals. The amplitudes of the var- ious components are low compared with the ECG of man, especially in lead I. The T-P intervals showed considerable var ia t ion with change in hear t rate. The QRS complexes are a lmost monophasic especially in aVR and aVL, and on leads II, III, and aVF dominant S
2 4 2 M O R I M O T O E T A L
M A B E L
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I I
V2
aVR
aVL
I
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~f aVF -r
ii~lililli~!ifiiiilii!l~iilliiiliiilliiill
i S I I I L;~ [ I
t-I, II f'l I ~ i
1 I I
[ I ] I I I t t I I I I [ I :1 I I I I I I I I I I I :1 1141 , ~ - . . - l ~ k , J ~ - I ; - , ,,, L I I I 1,1 I
I l l l i I I I I I l i t I f I i t
..... " I I I i I I t ITJ I I
I I / k : l I : l l l t I I ~ 1 1 I t F ~ I I [ :1 I ! .1 I I I I I h I ~ , " i ~ t ~ ~ I ~ 1, I I " ~ ~ I I t I Pll I I t / 1-1117 I I r % l , J
l 1 I l l I I I I l ] l l ! l i l , I I t I I F I I I I I t I I I I
' I I I I11 I Ii I
llmV I
Isec
Fig. 1. Standard bipolar, unipolar limb and V2 leads from female burro, Mabel.
waves are observed with very small R. The P waves obtained from Maud showed a diphasic pattern in every lead. Notchings were also ob- served on the QRS complexes on her espe- cially in aVR and aVL.
The resul ts of vector analyses (frontal plane) are shown in Fig. 3 and the values are summarized in Table 2. The orientation of the vector on the QRS complex is craniad and those of P and T are caudad. Precordial leads taken at V1 to V6 showed almost identical wave forms wi th leads II and III wi th a max imum ampli tude in lead V~, which is shown in Figs. 1 and 2. The precordial leads are presented in Fig. 4. The effects of respira- tion on ECG were not detectable since the respiratory frequency was almost identical with hear t rate.
DISCUSSION
The electrocardiographic data on the two burros are summarized in Table 3 together with those reported on some other mammals. The durations of electrocardiographic inter- vals found in the burros are within the nor- mal range reported for horses except tha t the Q-T interval is longer in burros. Vector orien- tations of burros appeared similar to tha t of the horse reported by Detwei ler and P a t t e r s o n 1 only as a v e c t o r c a r d i o g r a m without numerical values, al though the vec- tor was more craniad in burros. Another ani- mal which exhibits ECGs somewhat similar to the burro is the camel. The durations of QRS complex and Q-T interval are longer in the burros, but P-R in te rva ls are a lmost
J. E L E C T R O C A R D I O L O G Y , V O L . 8, N O . 3, 1 9 7 5
ECG OF BURROS 243
M A U D
I
11
IT[
I I
V 2
I I
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a V R ' ...... ......... . . . . . . . . . . . . . . . . . . . . . . . . . . j ; !:iii!;L iiiii iiiiiiiiii; iii#ii:~ :i!iiiiiii!iiiii!: iil
f i l l 1 1 1 F iil I I I I I I I l i l Iil!il ' : ill IIIlil:::~i Iii ili:~iilii Ii1! liliil iiiliiiilii! J i:#lliil I I? I ;I I I l i I iI I:i~l::~:li!ili~ !l i ill II]llliiiil!iii II]t] lib !liili I~:i!ili!i::liii lti!i ll!liitiJll I I
~;:gl IIi ill! if! | ? I I I g l I I t I I I I I i::~:::::::::::::i:::::::::i
A ~ I / I I Ill I I ; 1 / I I , ~ l l . l l l l I I:::::.::l::tl:l~ll:.::l:~ll~l U V L
" " ~ " " ::i I I I I I I I I
I I
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aVF i ' . . . . . J2 I I N o E C G T O O I
, [ I m V I s e c
Fig. 2. Standard bipolar, unipolar limb and V2 leads from female burro, Maud.
identical. Furthermore, the vector orientation reported by Geddes et aP is very similar to that observed in the burros. The low ampli- tude QRS deflections observed in the burros are also reported for other large animals l~ and are probably expla ined as be ing the consequence of the high degree of synchro- nized ventricular depolarization resulting in various waves of depolarization having a can-
celling effect and in a resultant slight average wave of depolarization passing in any given direction, lo
The low voltage recorded in limb lead I suggests tha t the average direction of de- polarization is almost perpendicular to that plane so that the wave front of depolarization does not pass primarily toward or away from the recording leads. The diphasic P wave and
TABLE 1
Heart Rate and Intervals of Burros' ECGs*
Heart Rate P P-R QRS Q-T (beats/rain) (sec) (sec) (sec) (sec)
Mabel 48 0.09 0.23 0.10 0.60
Maud 47 0.10 0.26 0.10 0.59
*Results are mean values on standard bipolar and unipolar limb leads, which are determined as a mean of five successive cycles.
J. ELECTROCARDIOLOGY, VOL. 8, NO. 3, 1975
244 M O R I M O T O ET AL
Q R S
T
MABEL
0 . 5 mV . _ 1 0 ~
QRS
M A U D
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P
-r
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Vl
V2
V5
M A U D I ' I
- �84 �84
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I
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I
~ 1 1 J t I ) ~ i]*:!}ili Ii[ 1i I !l iJi i l i! l l I ?l LII:1111 I I~q~[-( I '1"[
i ! i i i i i i i i : i i i i
~ iil I i i L iii[ i I :: liiiil
~ eORPO~T,ON ~UFFAL0. ~ W VO~
.. I ImV Isec
Fig. 4. Chest leads V1 to V6 and Vlo (over the dorsal spinal process at the level of V6) on burro, Maud.
O. ELECTROCARDIOLOGY, VOL. 8, NO. 3, 1975
E C G O F B U R R O S 2 4 5
TABLE 2
Vector Orientation of Burros' ECGs
P QRS T
degrees mV degrees mV degrees mV
Mabel 92 0.23 -90 136 74 0.40
Maud 91 0.30 -82 0.87 92 0.36
TABLE 3
Comparison of ECG Data on Various Animals
Heart Intervals Vector Orientations Rate (sec) (degree)
(beats/min) P-R QRS Q-T P QRS T Reference
27 to 60 0.32 to 0.73 0.09 to 0.34 0.36 to 1.08 Cited from Geddes et al., 19739
75 0.19 0.10 0.33 "
24t0 50 0.28t00.50 0.07to0.18 0.55to1.00 "
24to 77 0.24to0.26 0.04to0.09 0.42to0.57 50to70 90to280 115to250 Geddesetal.,19739
24 to 70 0.19 to 0.38 0.08 to 0.14 0.38 to 0.58 Detweiler and Patterson, 19631
85to150 0.14t00.22 0.07to0.12 0.24t00.30 25t050 290tu345 75to110 Hamlinetal.,197211
100to200 0.06to0.13 0.03to0.04 0.15te0.26 17to71 -90to 93 90to-108 Dukesand Szabuniewicz, 196912
43 to 54 0.22 to 0.27 0.09 to 0.11 0.58 to 0.62 91 to 92 -82 to -90 74 to 92 Present study
Whales
Giraffes
Elephants
Camels
Horses
Pinnipeds
Pigs
Burros
the notchings observed in Maud's ECGs were consistent, being seen on recordings made on o the r days. Such diphasic waves have been reported to be frequent ly found in equine ECGs and are considered to be normal. 1
Animal species tha t have thus far been sub- jected to e lect rocardiographic s tudy have been categorized according to their mean spa- t ia l QRS. 13 Category A consists of those species whose QRS is oriented caudad, in which primates and carnivores are included. Category B consists of those species whose QRS is oriented craniad, in which ungulates, birds, equine species, swine and cetaceans thus far studied are included. Burros studied in this report fall in" Category B and support the categorization by Hamlin et a l J a
J. E L E C T R O C A R D I O L O G Y . VOL. 8. NO. 3. 1975
REFERENCES
1. DETWEILER, D K AND PATTERSON, D F: Dis- eases of the blood and cardiovascular system. In Equine Medicine and Surgery, Bone, J R, et al, eds. American Veterinary Publication, Inc, Santa Barbara, Ca, 1963, p. 341
2. LANNEK, N AND RUTQVIST, L: Electrocardiog- raphy in horses, A historical review. Nord Veterinarmed 3:435, 1951. (Cited from Ref 1)
3. YOUSEF, M K AND DILL, D B: Resting energy metabolism and cardiorespiratory activity in the burro, Equus asinus. J Appl Physiol 27:229, 1969
4. YOUSEF, M K AND DILL, D B: Energy expendi- ture in desert walks: Man and burro, Equus asinus. J Appl Physiol 27:681, 1969
246 MORIMOTO ET AL
5. BULLARD, R W, DILL, D B AND YOUSEF, M K: Responses of the burro to desert heat stress. J Appl Physiol 29:159, 1970
6. YOUSEF, M K, DILL, D B AND MAYER, M G: Shifts in body fluids during dehydration in the burro, Equus asinus. J Appl Physiol 29:345, 1970
7. YOUSEF, M K, BURK, D AND DILL, D B: Bio- chemical properties of the blood of three equines. Comp Biochem Physio139B:279, 1971
8. YOUSEF, M K, DILL, D B AND FREELAND, D V: Energetic cost of grade walking in man and burro, Equus asinus: desert and mountain. J Appl Physiol 33:337, 1972
9. GEDDES, L A, TACKER, W A, ROSBOROUGH, J, MOORE, A G AND CABLER, P: The electro-
cardiogram of a dromedary camel J Electro- cardiol 6:211, 1973
10. BREAZILE, J E, ed.: Textbook of Veterinary Physiology. Lea & Febiger, Philadelphia, Pa, 1971, p. 244
11. HAMLIN, R L, RIDGWAY, S H AND GILMARTIN, W G: Electrocardiogram of pinnipeds. Am J Vet Res 33:867, 1972
12. DUKES, T W AND SZABUNIEWICZ, M: The electrocardiogram of conventional and minia- ture swine (Sus scrofa). Can J Comp Med 33:118, 1969
13. HAMLIN, R L AND SMITH, C R: Categorization of common domestic mammals based upon their ventricular activation process. Ann NY Acad Sci 127:195, 1965
J. ELECTROCARDIOLOGY, VOL. 8, NO. 3, 1975
