The prevalence of cardiac arrhythmia in Khuzestan buffaloes (Bubalus bubalis)

Transcription

1 CARDIAC ARRHYTHMIA IN BUFFALOES 99 The prevalence of cardiac arrhythmia in Khuzestan buffaloes (Bubalus bubalis) A. GHADRDAN MASHHADI 1, R. HAJI HAJIKOLAI 1, A. REZAKHANI 2, R. FATEMI 1, S. KAMALI 1 1 School of veterinary medicine, Shahid Chamran University, Ahvaz, Iran. 2 School of veterinary medicine, Shiraz University, Shiraz, Iran. *Corresponding author kianeg2000@yahoo.com SUMMARY The present study was performed to establish the prevalence of cardiac arrhythmia in 100 clinically healthy buffaloes of different ages and sexes. The buffaloes were divided into male (n=41) and female (n=59) and two age groups (less than 2.5, n=53, and more than 2.5, n=47). After taking the anamnesis and performing a clinical examination, electrocardiogram was obtained based on an apex lead system with the paper speed of 25mm sec -1 and sensitivity of 10 mm mv -1 at rest. The electrocardiograms were evaluated and the results showed that 70% of the buffaloes were affected with some kind of arrhythmia. The most frequent arrhythmias were wandering pacemaker (57% of all buffaloes), Sinus arrhythmia (29%), Second-degree atrioventricular (AV) block (9%), Electrical alternance (5%), and First degree AV block (2%). In the two age groups, significant difference in the prevalence of the arrhythmia was observed only for sinus arrhythmia and second degree atrioventricular block, The frequencies of these two cardiac arrhythmias were higher in the younger buffaloes (P<0.05). There was no significant difference in the prevalence of the different arrhythmia between males and females. Keywords: Arrhythmia, Cardiac, Buffalo, ECG SOMMAIRE La prévalence de l arythmie cardiaque chez les buffles de Khuzestan (Bubalus bubalis) La présente étude a été réalisée pour connaître la prévalence des troubles du rythme cardiaque chez 100 buffles cliniquement sains, dans deux groupes d âge et les deux sexes (41 males et 59 femelles). Les buffles ont été divisés en 2 groupes d âge (moins de 2,5 ans et plus de 2,5 ans). Après la prise de l historique et un examen clinique, un électrocardiogramme (ECG) a été au repos selon la dérivation «base-apex a la vitesse de défilement de 25 25mm sec -1 et la sensibilité de 10 mm mv -1. Les ECG ont été évalués et les résultats ont montré que 70% des buffles présentent au moins un type d arythmie. les Arythmies observées ont e un Wandering Pacemaker (59% des cas), une arythmie sinusale (29%), un bloc AtrioVentriculaire du second degré(9%), un alternance électrique(5%) et un bloc AV du premier degré(2%). Une différence significative entre les deux groupes d âge, n a été observée que dans la fréquence de l arythmie sinusale et du bloc AV du second degré, significativement plus fréquents dans le groupe de moins de 2.5 ans (p <0,05). Aucune différence significative de la fréquence des arythmies n a été notée entre les groupes des deux sexes. Mots-clés: Arythmie, cardiaque, buffles, ECG Introduction Cardiac arrhythmias are abnormalities in the normal heart rate, rhythm or conduction pattern. Arrhythmias result from abnormalities of impulse generation or impulse conduction or a combination of both (6). Irregularity in cardiac rate and rhythm can occur in normal animals due to strong or varying autonomic influence (functional) but it can also be reflection of primary myocardial disease (pathological). Other factors such as acid- base and electrolyte imbalances can influence rate and rhythm (11). It is important to distinguish between pathological arrhythmias that are primary and those that are secondary. The treatment and prognosis for two types of arrhythmias can be different, and examination and laboratory tests are used to assist in making the distinction. The most effective method for identifying the specific arrhythmia is to perform an electrocardiogram (ECG) (6). Although there are several studies carried out on the frequency and types of functional arrhythmias in large animals (12, 13, 18) it is very scanty in buffaloes (17, 21). The study was aimed to determine the prevalence of cardiac dysrhythmias in the healthy river buffalo (Bubalus bubalis) in Khuzestan province (Southwest of Iran). Because of Specific climatic conditions, Khuzestan is a major center of buffalo breeding in Iran and almost buffaloes are kept in this province. Materials and methods One hundred buffaloes (Bubalus bubalis) from five Counties of Khuzestan province (Ahvaz, Shoshtar, Dezfoul, Shadegan and Sosangerd) were selected for this study. In each farm, after taking the anamnesis, all buffaloes were used for an ECG recording, providing that the animals were healthy with no clinical signs of any organ abnormalities and no treated or not taking medication in recent weeks. The ECGs were recorded outdoors and in season with low temperature changes in the morning from 9.00 to Closer to the hot season, the same procedure but with shortening the morning test period starting from 9.00 AM was used. Each animal was kept in a standing position in a stock without any tranquilizer or sedative and given at least 5 to10 minutes to get relaxed. No clipping or shaving was carried out for electrodes attachment. A base apex bipolar lead was used for recording. Alligator types of electrodes were used for this recording. After cleaning the area with alcohol, the positive electrode was attached to the skin over the left fifth intercostals space just posterior to the olecranon and the negative one over the jugular furrow about 1/3 of the neck on the left side, and the

2 100 GHADRDAN MASHHADI (A.) AND COLLABORATORS earth electrode was attached away from these two electrodes. The attachment of the negative electrode on the left side of the neck was used as previously researched proved that there is no significant difference when attaching this electrode on the right or left side of the neck in the horse and cattle (Rezakhani et al., 1994). Electrocardiograms were taken for at least 2 minutes and all of them were obtained on a single channel battery driven machine (Fukuda Denshi, Tokyo, Japan) with the paper speed 25mm/sec and calibration of 10 mm equal to 1 mv. ECGs were examined by two authors (A.GH and AR) independently and finally both authors interpreted all dysrhythmias jointly, the heart rates of all animals were recorded. The first degree AV block was diagnosed when P-R intervals exceeded 0.26 seconds (15) and Sinus arrhythmia was diagnosed when variation in the P-P intervals (greater than 10% of the mean heart rate) with or without variation in the P-R interval (11). If there was an abnormality in cardiac rhythm, for the differentiation between physiological and pathological arrhythmia, the animal was forced to exercise for 2-5 minutes and electrocardiography was done again immediately. Animals were arbitrarily divided into two age groups: less than 2.5 years old (group 1), and more than 2.5 years old (group 2) according to teeth formula. They were also divided into two sex groups: male group (m) and female group (f). Statistical methods used were, the Mann-Whitney U and Chi-square. Data were analyzed using SPSS software version 16. P<0.05 was considered as statistically significant. Results The heart rates of each age group and each sex group were calculated and were 70±12.5, 70±15, 80±12.5, and 70±10 for groups of 1, 2, m, and f, respectively. No difference was found between group1 and group 2 and between group m and group f. Also, the heart rate of animals with arrhythmia and animals without arrhythmia was calculated and were 70±10 and 80±15, respectively. The heart rate of cases with arrhythmia was lower than in buffaloes with no abnormality, but this difference was not statistically significant. The result showed that 70% of buffaloes had at least, one type of cardiac arrhythmias. All arrhythmias in the present study were physiologic and disappeared after to force the animal to exercise. The frequency of cardiac arrhythmia in two age groups (group 1 and group2) and two sexes (male and female) were 44 (83%), 26 (55.3%), 31 (75.6%), and 39 (66.1%), respectively. A significant relationship was observed between age groups and cardiac arrhythmias but the relationship between sex and cardiac arrhythmias was not significant. The types and number of arrhythmias in age and sex groups are given in the Tables I and II. One, two, three and four types of cardiac arrhythmia were diagnosed respectively in 45%, 19%, 5% and 1% of buffaloes. 57% of cases showed wandering pacemaker with 33 (62.3%), 24 (51.1%), 26 (63.4%) and 31 (52.5%) in the groups of 1, 2, m and f, respectively. Sinus arrhythmia was seen in 29 cases with 11 (26.8%), 18 (30.5%), 21 (39.6%), and 8 (17%) in the groups of m, f, 1 and 2, respectively. Second- degree AV block was seen in 9 buffaloes with 7(13.2%), 2(4.2%), 3 (14.6%), and 6 (5%) in groups of 1, 2, m and f, respectively. Electrical alternance was seen in five buffaloes, all of them were in the group 1, and two buffaloes (4.8%) were in the group m and three buffaloes (5%) were in the group f. Two female buffaloes had first degree AV block, which one of them (2.1%) in group 2, had second degree AV block, Sinus arrhythmia, and wandering pacemaker and another one (1.8%) was in group 1, had second degree AV block and Sinus arrhythmia. In two age groups, significant difference was seen only in the frequency of sinus arrhythmia (p=0.022) and second degree of AV block (p=0.029). The frequencies of these two types of cardiac arrhythmia in group 1 were more than another age group. The relationship between sex and each types of cardiac arrhythmia were not significant. Discussion While severe cardiovascular diseases are relatively uncommon in bovidae but it is important that clinicians examine this system with care during the routine clinical examination. Early detection of cardiovascular disease might enable appropriate remedial action be taken and an accurate prognosis of the patient condition to be offered (4). Electrocardiography is a method of choice for evaluating electrical activity of the heart. Many studies have been carried out to establish the prevalence of cardiac arrhythmias in domestic animals (1,2,3,5,7,10,12,14,15,18,20 and 21). The majority of studies have been conducted on dogs and horses (1, 2, 12 and18). In the ruminants, the work has been focused on cattle and very few studies were carried out on buffaloes (17, 21). Various lead systems have been used for recording ECG from animals and it has been established that a base apex lead is the best for monitoring arrhythmias in cows (15). In this study a base apex lead was used for diagnosing cardiac rhythm irregularities in clinically healthy buffaloes. This study showed 70% of buffaloes had at least one type of cardiac arrhythmias. As it was mentioned, all arrhythmias were disappearing after to be forced animals to exercise and therefore these arrhythmias were classified as physiological induced by increased vagal tone. Most of these arrhythmias were seen in buffaloes with lower heart rate, which it confirms the above conclusion regarding the increased vagal tone. The frequencies of physiological arrhythmia in a variety of large animals have been reported but such a study on buffaloes is scant. In other large animals different results have been reported. For example in a study on 952 clinically healthy cattle, 202 (21.2%) cases had arrhythmias and differences

3 CARDIAC ARRHYTHMIA IN BUFFALOES 101 Rhythm Under 2.5 year Upper 2.5 year Total No Freq (%) No Freq (%) No Freq (%) No abnormalities SA SA+AVB II +el al SA+WPM SA+ el al SA+WPM+ AVB II SA+WPM+ AVB II+AVB І SA+WPM+ el al SA+ AVB II+AVB І AVB II WPM+ el al WPM+ AVB II WPM el al Total SA: Sinus arrhythmia, AVB І: First degree AV block, AVB II: Second degree AV block, WPM: wandering pacemaker el al., Electrical alternance. Table І: Frequency of cardiac arrhythmia in two age groups Rhythm Female Male Total No Freq (%) No Freq (%) No Freq (%) No abnormalities SA SA+AVB II +el al SA+WPM SA+ el al SA+WPM+ AVB II SA+WPM+ AVB II+AVB І SA+WPM+ el al SA+ AVB II+AVB І AVB II WPM+ el al WPM+ AVB II WPM el al Total SA: Sinus arrhythmia, AVB І: First degree AV block, AVB II: Second degree AV block, WPM: wandering pacemaker el al.: Electrical alternance. Table II: Frequency of cardiac arrhythmia in two sex groups

4 102 GHADRDAN MASHHADI (A.) AND COLLABORATORS between three age groups (1-3 years, 3-6 years and upper 6 years old) were not significant(3). In a study performed on 118 healthy Iranian Najdi goats 53% of goats had at least one type of arrhythmia (10). Physiologic arrhythmia in goat is also reported by smith & Sherman (19). Pourjafar et al. evaluated ECGs of 32 healthy Iranian fat tailed sheep and detected 20 (62.5%) with sinus arrhythmia (8). Ghadrdan et al. (20) reported several types of arrhythmias in 105 Arab horses (36.2%). There was significant differences between two sex groups, but not between age groups (under 4 years, between 4-8 years, upper 8 years)(20). The physiological arrhythmia observed in this study was wandering pacemaker, sinus arrhythmia, second -degree AV block, electrical alternance and first- degree AV block. Wandering pacemaker was the most common arrhythmia (57%). It refers to a sudden or gradual charge in configuration and amplitude of atrial depolarization wave (p- wave) (21). The sinus arrhythmia is a normal physiological arrhythmia that occurs at slow resting heart rates and is associated with variation in the rate of discharge from the sinoatrial node associated with variation in the intensity of vagal stimulations (11). This type of arrhythmia was observed in 29% of buffaloes of our study. First degree AV block occurs when conduction is delayed at the Atrioventricular node. The P-R interval is prolonged beyond normal limits and the condition may be transient because of vaxing and waning vagal tone (11). In present study, two buffaloes had First degree AV block. Second degree AV block also called partial heart block, occurs when there is periodic interference with conduction at the Atrioventricular node so that some atrial contraction are not followed by ventricular contraction. This may occur apparently at random or occur in a regular pattern. The electrocardiogram shows the presence of a P-wave but complete absence of the subsequent QRS and T waves at the blocked beat (11). The prevalence of this arrhythmia in buffaloes was 9% in our study. In a study on 100 buffaloes, sinus arrhythmia, electrical alternance and second -degree AV block were seen in 3, 1 and 1 buffaloes, respectively (16). Reasons of differences in frequency of type of arrhythmias were not clear for author. In a study on 284 buffaloes with different age groups wandering pacemaker was seen in 27 buffaloes. The authors believed that wandering pacemaker was not pathological and presented because of increasing vagal tone and showed the occurrence of wandering pacemaker in less than 1.5 years male buffaloes more than adult male and female buffaloes (21). In this study, the difference between age groups is almost similar to our study as the prevalence of wandering pacemaker was higher in younger buffaloes(less than 2.5 years). Machida et al. performed a study on 285 healthy Holstein dairy cows and detected atrial fibrillation in seven cows (2.5%). They suggested that this condition may be interpreted as an increased load imposed on the heart, sympathetic tone or increased vagal tone (5). Rezakhani et al. performed a study on 952 healthy cows and detected sinus arrhythmia, sinus tachycardia, first degree AV block, ventricular premature complex, atrial premature contraction, sinus bradycardia, and ventricular escape beat (14). Pourjafar et al. evaluated arrhythmia in 118 clinical healthy Najdi goats and recorded sinus arrhythmia (n=23), ventricular premature beat (n=3), and sinoatrial block (n=1). 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