Sinus tachycardia (ST) can be described as a heart rhythm that originates in the sinus node and proceeds through the rest of the electrical conduction system, but is faster than normal. It is a heart rhythm with elevated rate of impulses originating from the sinoatrial node. In dogs, there are different normal heart rates for different size dogs. In standard dogs, greater than 160 bpm is considered sinus tachycardia condition. For giant breeds, greater than 140 bpm, 180 bpm in toy breeds, and 220 bpm in puppies. Changes in heart rate usually involve a reciprocal action of the parasympathetic and sympathetic divisions of the autonomic nervous system.
The rapid heart rate can compromise cardiac output as too rapid rate shortens filling time for heart chambers which results in decreased cardiac output, decreased coronary blood flow and a concurrent increase in oxygen demands. This is the most common benign arrhythmia in dogs. It is also the most common rhythm disturbance in postoperative patients.
Common symptoms of Sinus Tachycardia include
Often no clinical signs because condition is a compensatory response to a variety of stresses
If associated with primary cardiac disease, weakness, exercise intolerance, or loss of consciousness may be reported
Pale mucous membranes if associated with anemia or congestive heart failure
Fever may be present
Signs of congestive heart failure, such as shortness of breath, cough, and pale mucous membranes may be present when ST is associated with primary cardiac disease
