Irregular Heartbeat in Dogs

Arrhythmia is a condition in which the heart beats with an abnormal or irregular rhythm. The heart may beat too fast, too slow, or it may skip beats. An irregular heart beat is the primary symptom of arrhythmia. A sinus arrhythmia is a condition in which the heart beat is irregular such that the heart rate speeds up during inhalation and slows down duing exhalation. Sinus arrhythmia is a normal variation in the heart rhythm caused by breathing.

The heart is positioned in the chest cavity, along with the lungs. With every inhalation, a slight negative pressure is put in the lungs which draws in air. With every exhalation, the opposite happens. A slight positive pressure is put on lungs. The heart is also exposed to these slight pressures as it is positioned with lungs. With a slight negative pressure caused by inhalation, a slight increase in the volume of the blood returning to the heart occurs. The heart senses this increase and takes it as a sign that the heart is filling up. Therefore, it responds by beating slightly faster. During exhalation, opposite happens. The heart slows down as it senses a slight decrease in blood volume. These minor changes are termed as sinus arrhythmia. 

Sinus arrhythmia also depends on reflexes involving stretch receptors in the lung, pressure-volume sensory receptors in the heart, blood vessels, and chemical factors of the blood. There is generally no consequence in blood flow, but marked sinus arrhythmia may produce a long enough pause in the heart's beating action to produce loss of consciousness if not accompanied by an escape rhythm.

Arrhythmia, usually, is not a cause of concern. An occasional irregular heartbeat may not cause any other problems. However, it can be a sign of some underlying condition and it is a good idea to have the dog checked for any underlying condition.

Bulldogs, lhasa apsos, Pekingese, pugs, shar-peis, shih tzus, and boxers are the breeds that are predisposed to sinus arrhythmia.

The most common and primary symptom of sinus arrhythmia a heartbeat that is too fast or too slow or that skips a beat. If pauses between beats are excessively long, weakness and loss of consciousness can occur. 

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