**4.4 Sinus Pauses (SP)**

The long SP (more than 2 seconds) or in high quantity may be a factor in the initiation of arrhythmias. The SP generally occurs when the animal's FC is the lowest. Among the breeds studied: 40% of healthy German shepherd dogs had SP. All healthy Doberman and Boxer dogs and 70% of healthy dogs of the English cocker spaniel breed also presented it, so the frequency of SP varies among healthy individuals of different breeds. The median frequency of SP also varies among different breeds, English cocker spaniel, German shepherd, Boxer and Doberman dogs, showed median SP, respectively, 3, 32.5, 366 and 141 in 24 hours. The average of greater SP is more similar: 2.5, 2.87, 3.5 and 3.3, respectively. Therefore, these preliminary studies, the median of PS varies among breeds more than the average of greater SP. The SP occurs with a wide variation among the numbers of healthy individuals and may be higher than 5 seconds at times of low HR in normal dogs.

### **4.5 Ventricular arrhythmias**

The EC detects the same changes of the ECG ventricular depolarization, but measured by a prolonged period and it identifies the different morphologies of normal and premature ventricular complexes (PVC) and is useful in predicting the DCM and in the identification of intermittent arrhythmias.

The presence of multiple PVC, single or repeated (mainly paroxysmal ventricular tachycardia) is associated with episodes of syncope or weakness. In more than half of the Boxer dogs who have syncope, the examination identifies at least 50 PVC in 24 hours.

Also, there is variation in the amount of PVC in dogs of different breeds; the occurrence is 26% for animals of the Beagle breed, 10% for the Doberman dogs, 20% in German shepherd and 40% in English cocker spaniel. However, between 50 and 70% of healthy Boxer dogs, have presented ventricular ectopic activity.

Doberman dogs that have more than 50 PVC in 24 hours have a higher risk of developing DCM, and it is considered abnormal if the presence of PVC is greater than 100 in 24 hours, especially if PVC are repeated or multiform. Based on studies a table was made (Table 1) for the evaluation of EC exams in Doberman pinschers. And Boxer dogs that present more than 91 PVC in 24 hours may have represented dogs with arrhythmogenic right ventricular cardiomyopathy or other disease processes that could have resulted in the development of ventricular arrhythmias (Stern et al., 2010).

The presence of supraventricular arrhythmias is typically observed in less than 25% of healthy small animals within 24 hours. The evaluation of this type of arrhythmia should be cautious; the software which reads the tapes are calibrated to values of human waves and sinus arrhythmia of normal dogs may be misinterpreted as supraventricular premature complex, and even if there are trembling in the baseline sinus, arrhythmia associated with the software can be interpreted incorrectly, such as atrial fibrillation. Solid memory devices (e.g. Memory card) work similarly to cassette and offer the advantage to be programmed to work with range of values of dogs and cats ranges, minimizing the number of premature supraventricular complexes false positive in the exam. So when the reading is done, someone familiar with sinus arrhythmia of dogs must be present to review this arrhythmia.

The long SP (more than 2 seconds) or in high quantity may be a factor in the initiation of arrhythmias. The SP generally occurs when the animal's FC is the lowest. Among the breeds studied: 40% of healthy German shepherd dogs had SP. All healthy Doberman and Boxer dogs and 70% of healthy dogs of the English cocker spaniel breed also presented it, so the frequency of SP varies among healthy individuals of different breeds. The median frequency of SP also varies among different breeds, English cocker spaniel, German shepherd, Boxer and Doberman dogs, showed median SP, respectively, 3, 32.5, 366 and 141 in 24 hours. The average of greater SP is more similar: 2.5, 2.87, 3.5 and 3.3, respectively. Therefore, these preliminary studies, the median of PS varies among breeds more than the average of greater SP. The SP occurs with a wide variation among the numbers of healthy individuals and may

The EC detects the same changes of the ECG ventricular depolarization, but measured by a prolonged period and it identifies the different morphologies of normal and premature ventricular complexes (PVC) and is useful in predicting the DCM and in the identification of

The presence of multiple PVC, single or repeated (mainly paroxysmal ventricular tachycardia) is associated with episodes of syncope or weakness. In more than half of the Boxer dogs who have syncope, the examination identifies at least 50 PVC in 24 hours.

Also, there is variation in the amount of PVC in dogs of different breeds; the occurrence is 26% for animals of the Beagle breed, 10% for the Doberman dogs, 20% in German shepherd and 40% in English cocker spaniel. However, between 50 and 70% of healthy Boxer dogs,

Doberman dogs that have more than 50 PVC in 24 hours have a higher risk of developing DCM, and it is considered abnormal if the presence of PVC is greater than 100 in 24 hours, especially if PVC are repeated or multiform. Based on studies a table was made (Table 1) for the evaluation of EC exams in Doberman pinschers. And Boxer dogs that present more than 91 PVC in 24 hours may have represented dogs with arrhythmogenic right ventricular cardiomyopathy or other disease processes that could have resulted in the development of

be higher than 5 seconds at times of low HR in normal dogs.

**4.4 Sinus Pauses (SP)** 

**4.5 Ventricular arrhythmias** 

intermittent arrhythmias.

have presented ventricular ectopic activity.

ventricular arrhythmias (Stern et al., 2010).


Table 1. Recommendations for interpretation of CE exam in Doberman dogs (Goodwin, 1998).

Sudden death has been reported in young dogs of German shepherd breed, very similar to the illness of sudden death in human babies. Both are characterized by paroxysmal ventricular tachycardia at moments of parasympathetic influences, as in deep sleep and after exercise. Any animal displaying episodes of ventricular tachycardia has high risk of sudden death.

This familiar arrhythmia in German shepherd dogs usually decreases after seven months of age, but can be detected in animals older than 5 years and are considered affected, the animals showing more than 240 PVC during the examination. Death was observed in 15 to 20% of affected animals and usually occurs at the age of 4-8 months (Moise et al., 1997). In Brazil, there are no reports of this hereditary disease that has been observed in North America.
