Standardization of Some Electrocardiographic Parameters of Captive Wild Cats (Leopardus wiedii, Leptailurus serval and Oncifelis colocolo)
S.G.S. Oda; R.J. Yamato; J.D.L. Fedullo; M.L.N. Neto; M.H.M.A. Larsson
The wild felines' habitat destruction by countless factors, such as the progress of the agricultural borders, the exploration of ores and wood, settlement and construction of dams for hydroelectric power station and illegal hunting, are responsible for the decline of their population (Oliveira 1994). Considering that all Brazilian savage felines are in extinction Zoos demonstrate a very big interest in maintaining and reproducing these species in captivity. However, they have been noticing difficulty of adaptation of the small felines' species, with rare exceptions, to reproduction programs in captivity (Oliveira & Cassaro 1999). Diseases, inadequate housing, poor nutrition, suboptimal reproduction and reduced number of animals in captivity are a big obstacle to be overcome in the conservation of these species. Furthermore, the high coefficient of consanguinity can lead to an emergence of a larger number of congenital diseases in certain populations. Therefore, maintaining small populations' survival will likely require intense handling, through translocation of individuals' from one population to another, providing a diffusion of the genetics from different populations of the same species.
Materials and Methods
This study was approved by the São Paulo Zoo Scientific and Research Committee. Seven captive healthy adult Oncifelis colocolo, nine Leptailurus serval and eight Leopardus wiedii were electrocardiographically evaluated. They were all also vaccinated with triple vaccine (FelO-VanPCT-lab Fort Dodge®, Saúde Animal Ltda, Campinas, São Paulo 13065-858, Brazil) and kept, each specie, into collective cages receiving special feeding, vitamins and mineral supplementation. These animals were anesthetized with a protocol of xylazine (Sedazine®, Fort Dodge Saúde Animal Ltda, Campinas, São Paulo 13065-858, Brazil; 1-2 mg/kg) and ketamine (Dopalen®, Sespo Divisão Vetbrands Saúde Animal, Jacareí, São Paulo 12308-420, Brazil; 10 mg/kg) and subjected to electrocardiographic examinations. The ECG exams were realized using electrocardiograph ECG 6 model (ECAFIX, São Paulo, Brazil); the animals were positioned in right lateral recumbency on a rubber rug to avoid interferences and electrodes were fastened to the skin with alligator clips. The contact points were humidified with liquid alcohol. All exams were registered, in all leads, in 1 cm = 1 mV sensibility and 25 mm/s speed (Kittleson & Kienle 1998, Miller et al. 1999, Tilley 1992), repeating the DII lead at the 50 mm/s speed with the same sensibility. The leads registered were DI, DII, DIII, aVR, aVL, aVF, CV5RL, CV6LL, CV6LU, V10 (Côté & Ettinger 2005, Kittleson & Kienle 1998, Miller et al. 1999). The values obtained were submitted to statistically descriptive analysis so that mean and standard deviation could be calculated. The results were analyzed by "Two sample T-test and Confidence Interval" from Minitab 14 for Windows, adopting P < 0.05.
Results expressed by mean and standard deviation for Oncifelis colocolo specie were: Heart Rate = 100±16 (bpm); P wave = 0.027±0.008 (s) X 0.086±0.024 (mV); PR interval = 0.084±0.011 (s); QRS compound = 0.044±0.005 (s) X 0.836±0.225 (mV); QT interval = 0.206±0.022 (s); R wave (CV6LL) = 1.414±0.254 (mV); R wave (CV6LU) = 1.057±0.444 (mV); Heart Rhythm: normal sinus rhythm (43.0%), sinus rhythm with wandering pacemaker (WPM) (28.5%), sinus arrhythmia with WPM (28.5%); electric axis: between +60° and +90° (100%); ST segment: normal (100%); T wave polarity (DII): positive (57.0%), negative (43.0%); T wave (V10): negative (100%).
Leptailurus serval specie were: Heart Rate = 111±35 (bpm); P wave = 0.032±0.004 (s) X 0.100±0.000 (mV); PR interval = 0.090±0.017 (s); QRS compound = 0.046±0.007 (s) X 1.439±0.472 (mV); QT interval = 0.236±0.022 (s); R wave (CV6LL) = 1.483±0.789 (mV); R wave (CV6LU) = 1.333±0.371 (mV); Heart Rhythm: normal sinus rhythm (56%), sinus rhythm with wandering pacemaker (WPM) (33%), sinus arrhythmia with WPM (11%); electric axis: between 0° and -30° (11%), between +60° and +90° (89%); ST segment: normal (78%), depression (22%); T wave polarity (DII): positive (78%), negative (11%), biphasic (11%); T wave (V10): negative (56%), positive (33%) and with interference (11%).
Leopardus wiedii specie were: Heart Rate = 106±16 (bpm); P wave = 0.026±0.005 (s) X 0.088±0.023 (mV); PR interval = 0.085±0.021 (s); QRS compound = 0.044±0.009 (s) X 0.925±0.318 (mV); QT interval = 0.221±0.022 (s); R wave (CV6LL) = 0.850±0.293 (mV); R wave (CV6LU) = 0.981±0.540 (mV); Heart Rhythm: normal sinus rhythm (62.5%), sinus rhythm with wandering pacemaker (WPM) (37.5%); electric axis: +60 (12%), between +60° and +90° (62%), +90° (13%), between +90° and +120° (13%); ST segment: normal (75%), elevation (25%); T wave polarity (DII): positive (100%); T wave (V10): negative (62.5%) and with interference (37.5%).
The R wave amplitude (DII) presented by some animals of the different species studied could be indicative of left ventricle enlargement if compared with normal parameter for Felis cati (domestic cat: 0.9 mV) (Côté & Ettinger 2005). However, a parallel echocardiographic study using the same animals didn't reveal any heart cavities' size alterations (Carvalho et al. 2007) in those animals whose R wave were over 0.9mV. Comparative x-rays of the animals that presented increased and normal R wave amplitude verified that animals with R wave over 0.9mV presented a more horizontal heart relative to the thorax when compared with those that presented normal R wave amplitude. Positioning of the heart within the thorax was presumed to be responsible for these electrocardiographic findings, as a more horizontal heart position provides greater R wave amplitude in the absence of enlargement of the left ventricle (Oda et al. 2007). Xylazine is an α2-agonists drug that causes a dose-dependent cardiac depression due to stimulation of α2-adrenergic receptors in central and peripheral nervous system. It also causes a decrease of central and peripheral norepinephrine release generating decrease of sympathetic nervous system activity. Effects of xylazine on the cardiovascular system include decreased heart rate, atrioventricular blockade that can be of 1st, 2nd and 3rd degree and reduction of the circulating blood volume (Fantoni & Cortopassi 2002). Ketamine is an anesthetic drug of the dissociative group that has a primarily sympathomimetic character and has, as main action mechanisms: interaction with N-methyl-D-aspartate (NMDA) type receptors reducing, selectively, the excitement produced by the excitatory amino acids; blockage of muscarinic receptors of central neurons increasing GABA inhibitor effects; and inhibition of serotonin, dopamine and noradrenaline reuptake. Effects of ketamine on cardiovascular system include increased heart rate, heart debit, blood pressure, and positive inotropic action on heart musculature, but the effect on heart rhythm is controversial (Fantoni & Cortopassi 2002). These stimulating effects of ketamine on the cardiovascular system can be attenuated by the preadministration of α2-agonists due to decreased sympathetic activity (Fantoni & Cortopassi 2002). Many studies can be found about α2-agonists and ketamine influence over cardiovascular system in cats (Calvert & Coulter 1981, Curro et al. 2004, Golden et al. 1998, Grove & Ramsay 2000) and they mainly cite bradycardia and hypotension induction by xylazine-ketamine association (Curro et al. 2004, Hsu & Lu 1984). It is evident that ketamine and xylazine can interfere with electrocardiographic parameters, mainly heart frequency and rhythm, but anesthesia is essential for the accomplishment of an electrocardiographic exam in wild species.
The electrocardiographic parameters of Leopardus wiedii, Leptailurus serval and Oncifelis colocolo have their own peculiarities that counter indicate usage of other species' ECG parameters to evaluate them. Electrocardiographic parameters established in this study can be considered normal when this xylazine / ketamine anesthetic protocol is used.
1. Oliveira TG (ed.) 1994. Neotropical Cats Ecology and Conservation. EDUFMA. São Luis. Pp. 220.
2. Oliveira TG, Cassaro K (eds). 1999. Guia de identificação dos felinos brasileiros, 2nd ed. Sociedade de Zoológicos do Brasil. São Paulo. Pp. 60.
3. Kittleson MD, Kienle RD (eds). 1998. Electrocardiography: basic concepts, diagnosis of chambers enlargement, and intraventricular conduction disturbances, p.72-94. In: Small animal cardiovascular medicine. Mosby. St Louis.
4. Miller MS, Tilley LP, Smith JR FW, Fox PR. 1999. Electrocardiography, p.67-105. In: Fox PR, Sisson D & Moise S. (eds). Canine and feline cardiology, 2nd ed. W.B. Saunders. Philadelphia.
5. Tilley LP (ed). 1992. General principles of electrocardiography, p.21-55. In: Essentials of canine and feline electrocardiography, 3rd ed. Lea & Febiger. Philadelphia.
6. Côté E, Ettinger SG. 2005. Electrocardiography and cardiac arrhythmias, p.1040-1076. In: Ettinger SG & Feldman EC (eds). Textbook of Veterinary Internal Medicine. Elsevier Saunders. St Louis.
7. Carvalho PSL, Pereira GG, Petrus LC, Soares EC, Michima LE, Larsson 2007. Avaliação de alguns parâmetros ecocardiográficos do gato-do-mato (Leopardus tigrinus), mantido em cativeiro e submetido à anestesia com xilazina e quetamina. Arq. Bras. Med. Vet. Zootec. 59(3):695-699.
8. Oda SGS, Neto ML, Fedullo JDL, Yamato RJ, Larsson MHMA. 2007. Padronização de alguns parâmetros eletrocardiográficos de animais da espécie Herpailurus yagouaroundi, mantidos em cativeiro. Bras. Ci. Vet. 14(1):47-50.
9. Fantoni DT, Cortopassi SRG (eds). 2002. Anestesia em Cães e Gatos. Roca. São Paulo p.151-173.
10. Calvert CA, Coulter DB. 1981. Electrocardiographic values for anesthetized cats in lateral and sternal recumbency. Am. J. Vet. Res. 42(8):1453-1455.
11. Curro TG, Okeson D, Zimmerman D, Armstrong DL, Simmons LG. 2004. Xylazine-midazolam-ketamine versus medetomidine-midazolam ketamine anesthesia in captive Siberian tigers (Panthera tigris altaica). J. Zoo. Wild. Med. 35(3):320-327.
12. Golden AL, Bright JM, Daniel GB, Fefee D, Schmidt D, Harvey RC. 1998. Cardiovascular effects of the alpha2-adrenergic receptor agonist medetomidine in clinically normal cats anesthetized with isoflurane. Am. J. Vet. Res. 59(4):509-513.
13. Grove DM, Ramsay EC. Sedative and physiologic effects of orally administered α2-adrenoceptor agonists and ketamine in cats. J. Am. Vet. Med. Assoc. 216(12):1929-1932.
14. Hsu WH, Lu Z. 1984. Effect of yohimbine on xylazine-ketamine anesthesia in cats. J. Am. Vet. Med. Assoc. 185:886-888.