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Agnieszka Noszczyk-Nowak, Urszula Paslawska, Jozef Nicpon ©
Department of Internal Diseases with Clinic for Horses, Dogs and Cats, Faculty of Veterinary Medicine, University of Environmental and Life Sciences, pl. Grunwaldzki
47, 50-366 Wroclaw, Poland
MORPHOLOGY OF VENTRICULAR PREMATURE BEATS IN BOXER
key words: dog, boxer, EKG, premature ventricular beat
Introduction
Boxers are a breed which is predisposed to cardiac diseases. Cardiomyopathy is a common cause of morbidity and mortality in boxers. Boxer cardiomyopathy has been grouped into 3 categories: isolated subclinical ventricular arrhythmias, arrhythmia-associated syncope or sudden death with normal myocardial function and systolic myocardial failure with or without ventricular arrhythmias. The trait of ventricular arrhythmias is inherited in boxers. The characteristic ventricular arrhythmias have been described in afflicted boxers. Left ventricular failure predominates and cardiac pathology of left ventricle (LV) is recognized in dogs with Boxer cardiomyopathy (DCM). In these dogs ventricular arrhythmias from left ventricle should predominate. In boxers with arrhythmogenic right ventricular dysplasia (ARVD) ventricular arrhythmias from right ventricle (RV) may be predominant. Routine electrocardiography is sensitive for detection of ventricular arrhythmias in boxers only if ventricular premature beats are frequent. Boxers with ARVD generally have > 1000 ventricular premature beats (VPs) in 24 hours. Kraus et al elaborated an algorithm of morphology classification of VPs in boxers as measured by 12-lead electrocardiography. This algorithm is helpful to evaluate an exit place of arrhythmias.
Task, the aim of article
The aim of this study was to evaluate morphology of ventricular premature beats in boxers with: dilated cardiomyopathy, arrhythmogenic right ventricular dysplasia and isolated subclinical ventricular arrhythmias.
This study was performed in 48 boxers. The clinical examination of the animals was conducted according to the following procedure: anamnesis, general clinical examination and cardiological examination. In all the dogs we carried out electrocardiography and echocardiography examinations. The 12-lead ECG was performed on BLT SD 08 device. The diagnosis was made on the basis of the recordings from all the leads. The ECG recordings were analyzed according to common procedures such as measuring of heart rate, leading rhythm and arrhythmias, amplitude and time of waves: P, Q, R, S and T; appearance of additional waves, duration of intervals and complexes: PQ, QRS, ST, QT, value of mean electrical axis, as well as other visible features of the recording. The next step was to evaluate morphology of VPs by Kraus' algorithm. ECHO was performed on Aloka 4000+
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echocardiograph. We evaluated the size of the right ventricle and the size of the left ventricle in diastole and systole, intraventricular septum and wall thickness in diastole and systole, shortening fraction and ejection fraction of the left ventricle. Results of research
We elaborated the table for this algorithm.
Table 1. Morphology of VPs and exit site in ventricles.
Right ventricle Left ventricle
lead Right septum Right apex RVOT Left septum Left apex LVOT Left caudal
I + + - +/-- - - -
II + + + - - - -
III + + + - - - -
aVR - - - + + + +
aVL - +/- - +/- + +/- +
aVF + + + - - - -
V1 +/- - +/- - + +
V2 + + + +/- - + +
V3 + + + +/- - + +/-
V4 + + + +/- - + -
V5 + + + - - - -
V6 + + + - - - -
+ Positive QRS deflection, - negative QRS deflection, RVOT, LVOT - outflow tract
Eleven (23%) of 48 boxers have VPs in electrocardiography record. In 6 dogs (55%) the exit size of arrhythmias was the left ventricle, in 5 dogs (45%) was right ventricle. Predominant cause of arrhythmias was isolated subclinical ventricular arrhythmias (45%).
Results of exit size of arrhythmias are included in Figure 1 and Table2 Figure 1. Exit size and cause of arrhythmias in boxers.
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Table 2. Exit size ant cause of arrhythmias in boxers.
No Exit size Cause
1 LVOT Isolated subclinical ventricular arrhythmias
2 RVOT Dilated cardiomyopathy
3 LVOT Isolated subclinical ventricular arrhythmias
4 RVOT Isolated subclinical ventricular arrhythmias
5 Left apex Isolated subclinical ventricular arrhythmias
6 Right apex Isolated subclinical ventricular arrhythmias
7 RVOT, right septum Arrhytmogenic right ventricular dysplasia
8 RVOT, right septum Arrhytmogenic right ventricular dysplasia
9 LVOT Dilated cardiomyopathy
10 LVOT Dilated cardiomyopathy
11 LVOT Aorta stenosis
Conclusion
The Kraus' algorithm is useful to evaluate an exit place of arrhythmias in boxers. The exit place of premature ventricular beats in boxers is the most often outflow tract from left ventricle. Main cause of premature ventricular beats in boxers was isolated subclinical ventricular arrhythmias.
Acknowledgments
This work was supported by the Polish Ministry of Education and Science (Grant No. N N308 071037)
Reference
1. Bright JM, Cali JV: Clinical usefulness of cardiac event recording in dogs and cats examined because of syncope, episodic collapse, or intermittent weakness: 60 cases (1997-1999). JAVMA 2000, 216, 1110-1114.
2. Fisher EW: Fainting in Boxers - The possibility of vaso-vagal syncope (Adams-Stokes attacks). J Small Anim Pract 1971, 12, 347-349
3. Krause MS, Moise NS, Rishniw M, Dykes N, Efb HN: Morphology of ventricular arrhythmias in boxer as measured by 12-lead electrocardiography with pace-mapping comparison. J Vet Intern Med 2002, 16, 153-158
4. Meurs KM, Spier AW, Wright NA, Atkins CE,. DeFrancesco TC. Gordon SG, Hamlin RL, Keene BW, Miller MW, Moise NS: Comparison of the effects of four antiarrhythmic treatments for familial ventricular arrhythmias in Boxer JAVMA 2002, 221, 522-52
5. Smith CE, Freeman LM, Rush JE, Cunningham SM, Biourge V: Omega-3 fatty acids in boxer dogs with arrhythmogenic right ventricular cardiomyopathy. J Vet Intern Med 2007, 21, 265-273
6. Vollmar A.: Cardiomyopathy in dogs. I Congress of veterinary cardiology. Wroclaw, 15.01.2000 s.1-10 .
Summary
Boxers are a breed which is predisposed to cardiac diseases. Cardiomyopathy is a common cause of morbidity and mortality in boxers. Kraus et al elaborated an algorithm of morphology classification of VPs in boxers as measured by 12-lead electrocardiography. This algorithm is helpful to evaluate an exit place of arrhythmias. The aim of this study was to evaluate morphology of ventricular premature beats in boxers. This study was performed in 48 boxers, 12 had VPs. We carried out qualification of VPs morphology and exit sites by the algorithm.
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