Factors Affecting the Normal ECG of Dogs
3.1 The dog's body position and forelimb position during measurement: The waveforms of the ECGs recorded in different body positions vary greatly in each lead. For example, Q waves are commonly seen in the right side of the Bits are rarely present or very small. Since the S-T segment and T wave of different body positions are also significantly different in some leads, the same body position must be used, otherwise the analysis and comparison will not be possible. At present, the right side is often used for measurement. Changes in the position of the dog's forelimbs will significantly change the dog's electrocardiogram, in which the Q wave, T wave and S-T segment have obvious changes. When measuring, the two front limbs of the dog must be parallel to each other and perpendicular to the long axis of the body.
3.2 The body shape of the dog: The body shape of the dog is different, and the position of the heart is not all the same. This has a large effect on the ECG pattern, especially the QRS complex. In addition, different body types have different cardiac potentials. The cardiac potential of dogs with short and wide thorax is transverse and vertical cardiac potential; dogs with narrow and long thorax are pendulous cardiac potentials, such as Collie, French poodle and German shepherd, etc.; French poodles and boxer dogs are intermediate cardiac potentials.
3.3 Breathing: Breathing action can cause changes in the position of the heart, changes in the electrical conductivity of lung tissue, changes in ventricular congestion, and changes in autonomic tension. Therefore, breathing has a great influence on the ECG waveform, especially when breathing deeply, the lung volume increases and the QRS complex decreases.
3.4 Gender: Different gender, the ECG data of dogs are not all the same, for example, the duration of P waves in female dogs is longer than that of male dogs.
3.5 Age: Dogs with different ages have different ECG data. The heart rate of puppies is faster than that of adult dogs, and the duration and interval of each wave will change.
3.6 Neural factors: sympathetic nerve excitation can cause heart rate to increase, P-R and Q-T intervals shorten, and P waves and T waves increase; vagus nerve excitation often causes the opposite result.
3.7 Feeding, training and external environment: Different feeding and training conditions will also affect the dog's ECG. Generally speaking, the heart rate of an untrained dog is faster than that of a trained dog; a well-raised dog is better than a poorly-raised dog. The dog's heart rate should be slow and relatively uniform. The interference of the external environment is mainly the interference of electrical appliances and wires. There should not be any charged instruments and wires passing through within two meters from the dog and the electrocardiograph. Large electrical appliances such as X-ray machines should be kept 10 meters away.
3.8 Human factors and other factors: inaccurate electrode positions of limb leads and chest leads when tracing ECG; poor electrode contact; improper operation of the ECG machine, etc., all of which can cause errors in the ECG graph, and even cannot be analyzed. In addition, the dog must be on the insulating surface during the measurement, and the metal collar and iron chain of the dog must be removed at the same time.
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